back to indexAlex Filippenko: Supernovae, Dark Energy, Aliens & the Expanding Universe | Lex Fridman Podcast #137
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The following is a conversation with Alex Filipenko, an astrophysicist and professor
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of astronomy from Berkeley.
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He was a member of both the Supernova Cosmology Project and the HiZ Supernova Search Team
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which used observations of the extragalactic supernova to discover that the universe is
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accelerating and that this implies the existence of dark energy.
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This discovery resulted in the 2011 NOVA Prize for Physics.
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Outside of his groundbreaking research, he is a great science communicator and is one
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of the most widely admired educators in the world.
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I really enjoyed this conversation and am sure Alex will be back again in the future.
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Quick mention of each sponsor, followed by some thoughts related to the episode.
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Neuro, the maker of functional, sugar free gum and mints that I used to give my brain
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a quick caffeine boost.
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BetterHelp, an online therapy with a licensed professional, Masterclass, online courses
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Please check out these sponsors in the description to get a discount and to support this podcast.
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As a side note, let me say that as we talk about in this conversation, the objects that
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populate the universe are both awe inspiring and terrifying in their capacity to create
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and to destroy us.
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Solar flares and asteroids lurking in the darkness of space threaten our humble, fragile
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existence here on Earth.
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In the chaos, tension, conflict, and social division of 2020, it's easy to forget just
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how lucky we humans are to be here, and with a bit of hard work, maybe one day, we'll
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venture out towards the stars.
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If you enjoy this thing, subscribe on YouTube, review it with Five Stars on Apple Podcast,
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follow on Spotify, support on Patreon, or connect with me on Twitter at Lex Friedman.
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And now, here's my conversation with Alex Filipenko.
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Let's start by talking about the biggest possible thing, the universe.
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Will the universe expand forever or collapse on itself?
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Well, you know, that's a great question.
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It's one of the big questions of cosmology, and of course, we have evidence that the matter
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density is sufficiently low that the universe will expand forever.
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But not only that, there's this weird repulsive effect, we call it dark energy for want of
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a better term, and it appears to be accelerating the expansion of the universe.
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So if that continues, the universe will expand forever, but it need not necessarily continue.
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It could reverse sign, in which case the universe could, in principle, collapse at some point
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in the far, far future.
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So in terms of investment advice, if you were to give me and then to bet all my money on
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one or the other, where does your intuition currently lie?
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Well, right now, I would say that it would expand forever because I think that the dark
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energy is likely to be just quantum fluctuations of the vacuum.
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The vacuum zero energy state is not a state of zero energy.
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That is, the ground state is a state of some elevated energy which has a repulsive effect
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And that will never go away because it's not something that changes with time.
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So if the universe is accelerating now, it will forever continue to do so.
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And yet, I mean, you so effortlessly mentioned dark energy.
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Do we have any understanding of what the heck that thing is?
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But we're getting progressively better observational constraints.
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So different theories of what it might be predict different sorts of behavior for the
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evolution of the universe.
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And we've been measuring the evolution of the universe now.
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And the data appear to agree with the predictions of a constant density vacuum energy, a zero
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But one can't prove that that's what it is because one would have to show that the measured
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numbers agree with the predictions to an arbitrary number of decimal places.
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And of course, even if you've got 8, 9, 10, 12 decimal places, what if in the 13th one,
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the measurements significantly differ from the prediction?
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Then the dark energy isn't this vacuum state, ground state energy of the vacuum.
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And so then it could be some sort of a field, some sort of a new energy, a little bit like
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light, like electromagnetism, but very different from light, that fills space.
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And that type of energy could in principle change in the distant future.
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It could become gravitationally attractive for all we know.
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There is a historical precedent to that, and that is that the inflation with which the
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universe began when the universe was just a tiny blink of an eye old, a trillionth of
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a trillionth of a trillionth of a second, the universe went whoosh, it exponentially
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That dark energy like substance, we call it the inflaton, that which inflated the universe,
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later decayed into more or less normal gravitationally attractive matter.
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So the exponential early expansion of the universe did transition to a deceleration,
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which then dominated the universe for about nine billion years.
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And now this small amount of dark energy started causing an acceleration about five billion
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And whether that will continue or not is something that we'd like to answer, but I don't know
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that we will anytime soon.
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So there could be this interesting field that we don't yet understand that's morphing over
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time, that's changing the way the universe is expanding.
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I mean, it's funny that you were thinking through this rigorously like an experimentalist.
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But what about like the fundamental physics of dark energy?
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Is there any understanding of what the heck it is, or is this the kind of the god of the
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gaps or the field of the gaps?
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So like there must be something there because of what we're observing.
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I'm very much a person who believes that there's always a cause, you know, there are no miracles
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of a supernatural nature, okay?
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So I mean, there are two broad categories, either it's the vacuum zero point energy,
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or it's some sort of a new energy field that pervades the universe.
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The latter could change with time, the former, the vacuum energy cannot.
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So if it turns out that it's one of these new fields, and there are many, many possibilities,
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they go by the name of quintessence and things like that, but there are many categories of
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those sorts of fields, we try with data to rule them out by comparing the actual measurements
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with the predictions.
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And some have been ruled out, but many, many others remain to be tested.
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And the data just have to become a lot better before we can rule out most of them and become
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reasonably convinced that this is a vacuum energy.
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So there is hypotheses for different fields, like with names and stuff like that?
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Yeah, you know, generically quintessence, like the Aristotelian fifth essence, but there
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are many, many versions of quintessence.
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There's K essence, there's even ideas that, you know, this isn't something from within
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this dark energy, but rather, there are a bunch of, say, bubble universes surrounding
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our universe, and this whole idea of the multiverse is not some crazy madman type idea anymore.
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It's, you know, real card carrying physicists are seriously considering this possibility
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And some types of multiverses could have, you know, a bunch of bubbles on the outside,
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which gravitationally act outward on our bubble because gravity or gravitons, the quantum
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particle that is thought to carry gravity, is thought to traverse the bulk, the space
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between these different little bubble membranes and stuff.
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And so it's conceivable that these other universes are pulling outward on us.
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That's not a favored explanation right now, but really, nothing has been ruled out.
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No class of models has been ruled out completely.
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Certain examples within classes of models have been ruled out.
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But in general, I think we still have really a lot to learn about what's causing this
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observed acceleration of the expansion of the universe, be it dark energy or some forces
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from the outside, or perhaps, you know, I guess it's conceivable that, and sometimes
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I wake up in the middle of the night screaming, that dark energy, that which causes the acceleration,
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and dark matter, that which causes galaxies and clusters of galaxies to be bound gravitationally
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even though there's not enough visible matter to do so.
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Maybe these are our 20th and 21st century Ptolemaic epicycles.
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So Ptolemy had a geocentric and Aristotelian view of the world.
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Everything goes around Earth.
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But in order to explain the backward motion of planets among the stars that happens every
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year or two, or sometimes several times a year for Mercury and Venus, you needed the
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planets to go around in little circles called epicycles, which themselves then went around
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And in this part of the epicycle where the planet is going in the direction opposite
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to the direction of the overall epicycle, it can appear in projection to be going backward
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among the stars, so called retrograde motion.
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And it was a brilliant mathematical scheme.
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In fact, he could have added epicycles on top of epicycles and reproduced the observed
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positions of planets to arbitrary accuracy.
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And this is really the beginning of what we now call Fourier analysis, right?
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Any periodic function can be represented by a sum of sines and cosines of different periods,
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amplitudes, and phases.
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So it could have worked arbitrarily well.
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But other data show that, in fact, Earth is going around the sun.
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So our dark energy and dark matter, just these band aids that we now have to try to explain
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the data, but they're just completely wrong.
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That's a possibility as well.
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And as a scientist, I have to be open to that possibility as an open minded scientist.
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How do you put yourself in the mindset of somebody that, or majority of the scientific
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community or majority of people believe that the Earth, everything rotates around Earth?
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How do you put yourself in that mindset and then take a leap to propose a model that the
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sun is, in fact, at the center of the solar system?
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I mean, so that puts us back in the shoes of Copernicus, right, 500 years ago, where
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he had this philosophical preference for the sun being the dominant body in what we now
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call the solar system.
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The observational evidence in terms of the measured positions of planets was not better
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explained by the heliocentric, sun centered system.
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It's just that Copernicus saw that the sun is the source of all our light and heat, and
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he knew from other studies that it's far away.
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So the fact that it appears as big as the moon means it's actually way, way bigger because
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even at that time, it was known that the sun is much farther away than the moon.
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So he just felt, wow, it's big, it's bright.
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What if it's the central thing?
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But the observed positions of planets at the time in the early to mid 16th century under
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the heliocentric system was not a better match, at least not a significantly better match
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than Ptolemy's system, which was quite accurate and lasted 1500 years.
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That's so fascinating to think that the philosophical predispositions that you bring to the table
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So like you have to have a young person come along that has a weird infatuation with the
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That like almost philosophically is like however their upbringing is, they're more ready for
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whatever the more the simpler answer is.
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Oh, that's kind of sad.
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It's a sad from an individual descendant of eight perspective because then that means
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like me, you as a scientist, you're stuck with whatever the heck philosophies you brought
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to the table and you might be almost completely unable to think outside this particular box
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This is why I'm saying that, you know, as an objective scientist, one needs to have
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an open mind to crazy sounding new ideas.
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And even Copernicus was very much a man of his time and dedicated his work to the Pope.
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He still used circular orbits.
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The sun was a little bit off center, it turns out, and a slightly off center circle looks
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like a slightly eccentric elliptical orbit.
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So then when Kepler, in fact, showed that the orbits are actually in general ellipses,
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not circles, the reason that he needed Tuco Brahe's really great data to show that distinction
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was that a slightly off center circle is not much different from a slightly eccentric ellipse.
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And so there wasn't much difference between Kepler's view and Copernicus's view and Kepler
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needed the better data, Tuco Brahe's data.
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And so that's, again, a great example of science and observations and experiments working together
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with hypotheses and they kind of bounce off each other.
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They play off of each other and you continually need more observations.
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And it wasn't until Galileo's work around 1610 that actual evidence for the heliocentric
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hypothesis emerged.
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It came in the form of Venus, the planet Venus, going through all of the possible phases from
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new to crescent to quarter to gibbous to full to waning gibbous, third quarter waning crescent,
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and then new again.
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It turns out in the Ptolemaic system with Venus between Earth and the sun, but always
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roughly in the direction of the sun, you could only get the new and crescent phases of Venus.
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But the observations showed a full set of phases.
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And moreover, when Venus was gibbous or full, that meant it was on the far side of the sun.
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That meant it was farther from Earth than when it's crescent, so it should appear smaller
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and indeed it did.
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So that was the nail in the coffin in a sense.
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And then Galileo's other great observation was that Jupiter has moons going around it,
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the four Galilean satellites.
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And even though Jupiter moves through space, so too do the moons go with it.
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So first of all, Earth is not the only thing that has other things going around it.
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And secondly, Earth could be moving as Jupiter does and things would move with it.
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We wouldn't fly off the surface and our moon wouldn't be left behind and all this kind
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So that was a big breakthrough as well, but it wasn't as definitive in my opinion as
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the phases of Venus.
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Sometimes I'm revealing my ignorance, but I didn't realize how much data they were working
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So it wasn't Einstein or Freud thinking in theories.
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It was a lot of data and you're playing with it and seeing how to make sense of it.
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So it isn't just coming up with completely abstract thought experiments.
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It's looking at the data.
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And you look at Newton's great work, right?
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The Principia, it was based in part on Galileo's observations of balls rolling down inclined
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planes, supposedly falling off the Leaning Tower of Pisa, but that's probably apocryphal.
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In any case, the Roman Catholic Church did history a favor, not that I'm condoning them,
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but they placed Galileo under house arrest and that gave Galileo time to publish, to
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assemble and publish the results of his experiments that he had done decades earlier.
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It's not clear he would have had time to do that, had he not been under house arrest.
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And so Newton, of course, very much used Galileo's observations.
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Let me ask the old Russian overly philosophical question about death.
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So we're talking about the expanding universe.
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How do you think human civilization will come to an end if we avoid the near term issues
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Will it be our sun burning out?
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Will it be comets?
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Will it be, what is it?
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Do you think we have a shot at reaching the heat death of the universe?
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So we're going to leave out the anthropogenic causes of our potential destruction, which
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I actually think are greater than the celestial causes.
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So if we get lucky and intelligent, I don't know.
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So no way will we as humans reach the heat death of the universe.
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It's conceivable that machines, which I think will be our evolutionary descendants, might
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reach that, although even they will have less and less energy with which to work as time
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progresses because eventually even the lowest mass stars burn out, although it takes them
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trillions of years to do so.
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So the point is that certainly on Earth, there are other celestial threats, existential threats,
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comets, exploding stars, the sun burning out.
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So we will definitely need to move away from our solar system to other solar systems.
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And then the question is, can they keep on propagating to other planetary systems sufficiently
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In our own solar system, the sun burning out is not the immediate existential threat.
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That'll happen in about five billion years when it becomes a red giant, although I should
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hasten to add that within the next one or two billion years, the sun will have brightened
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enough that unless there are compensatory atmospheric changes, the oceans will evaporate
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They're going to need much less carbon dioxide for the temperatures to be maintained roughly
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at their present temperature, and plants wouldn't like that very much.
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So you can't lower the carbon dioxide content too much.
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So within one or two billion years, probably the oceans will evaporate away.
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But on a sooner time scale than that, I would say an asteroid collision leading to a potential
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mass extinction, or at least an extinction of complex beings such as ourselves that require
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quite special conditions unlike cockroaches and amoebas to survive, one of these civilization
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changing asteroids is only one kilometer or so in diameter and bigger, and a true mass
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extinction event is 10 kilometers or larger.
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Now it's true that we can find and track the orbits of asteroids that might be headed toward
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Earth, and if we find them 50 or 100 years before they impact us, then clever applied
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physicists and engineers can figure out ways to deflect them.
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But at some point, some comet will come in from the deep freeze of the solar system,
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and there we have very little warning, months to a year.
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What's the deep freeze, sorry to interrupt.
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The deep freeze is sort of out beyond Neptune.
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There's this thing called the Kuiper Belt, and it consists of a bunch of dirty ice balls
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or icy dirt balls.
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It's the source of the comets that occasionally come close to the Sun.
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And then there's an even bigger area called the Scattered Disk, which is sort of a big
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doughnut surrounding the solar system way out there from which other comets come.
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And then there's the Oort Cloud, W O O R T after Jan Oort, a Dutch astrophysicist, and
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it's the better part of a light year away from the Sun, so a good fraction of the distance
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to the nearest star, but that's like a trillion or 10 trillion comet like objects that occasionally
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get disturbed by a passing star or whatever, and most of them go flying out of the solar
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system, but some go toward the Sun, and they come in with little warning.
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By the time we can see them, they're only a year or two away from us.
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And moreover, not only is it hard to determine their trajectories sufficiently accurately
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to know whether they'll hit a tiny thing like Earth, but outgassing from the comet of gases
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when the ices sublimate, that outgassing can change the trajectory just because of conservation
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of momentum, right?
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It's the rocket effect.
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Gases go out in one direction, the object moves in the other direction.
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And so since we can't predict how much outgassing there will be and in exactly what direction
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because these things are tumbling and rotating and stuff, it's hard to predict the trajectory
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with sufficient accuracy to know that it will hit.
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And you certainly don't want to deflect a comet that would have missed but you thought
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it was going to hit and end up having it hit.
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That would be like the ultimate Charlie Brown goat instead of trying to be the hero, right?
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He ended up being the goat.
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What would you do if it seemed like in a matter of months that there is some nonzero probability,
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maybe a high probability that there will be a collision?
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So from a scientific perspective, from an engineering perspective, I imagine you would
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actually be in the room of people deciding what to do.
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What uh, philosophically too.
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It's a tough one, right?
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Because if you only have a few months, that's not much time in which to deflect it.
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Early detection and early action are key because when it's far away, you only have to deflect
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it by a tiny little angle.
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And then by the time it reaches us, the perpendicular motion is big enough to miss Earth.
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All you need is one radius or one diameter of the Earth, right?
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That actually means that all you would need to do is slow it down so it arrives four minutes
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later or speed it up so it arrives four minutes earlier and Earth will have moved through
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one radius in that time.
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So it doesn't take much.
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But you can imagine if a thing is about to hit you, you have to deflect it 90 degrees
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You know, and you don't have much time to do so and you have to slow it down or speed
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it up a lot if that's what you're trying to do to it.
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And so decades is sufficient time, but months is not sufficient time.
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So at that point, I would think the name of the game would be to try to predict where
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And if it's in a heavily populated region, try to start an orderly evacuation perhaps.
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But you know, that might cause just so much panic that I'm, how would you do with New
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York City or Los Angeles or something like that, right?
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I might have a different opinion a year ago, I'm a bit disheartened by, you know, in the
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movies, there's always extreme competence from the government.
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But we expect extreme incompetence, if anything, right?
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So I'm quite disappointed.
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But sort of from a medical perspective, I think you're saying there, and a scientific
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one, it's almost better to get better and better, maybe telescopes and data collection
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to be able to predict the movement of these things, or like come up with totally new technologies
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that you can imagine actually sending out, like probes out there to be able to sort of
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almost have little finger sensors throughout our solar system to be able to detect stuff.
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Well, that's right.
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Yeah, monitoring the asteroid belt is very important and 99% of the so called near earth
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objects ultimately come from the asteroid belt.
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And so there we can track the trajectories and even if there's a close encounter between
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two asteroids which deflects one of them toward earth, it's unlikely to be on a collision
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course with earth in the immediate future, it's more like tens of years, so that gives
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But we would need to improve our ability to detect the objects that come in from a great
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And those are much rarer, the comets come in, 1% of the collisions perhaps are with
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comets that come in without any warning hardly.
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So that might be more like a billion or two billion years before one of those hits us.
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So maybe we have to worry about the sun getting brighter on that time scale.
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I mean, there's the possibility that a star will explode near us in the next couple of
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But over the course of the history of life on earth, the estimates are that maybe only
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one of the mass extinctions was caused by a star blowing up in particular, a special
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kind called a gamma ray burst, and I think it's the Ordovician–Silurian extinction
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420 or so, 440 million years ago that is speculated to have come from one of these particular
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types of exploding stars called gamma ray bursts.
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But even there, the evidence is circumstantial.
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So those kinds of existential threats are reasonably rare.
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The greater danger I think is civilization changing events where it's a much smaller
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asteroid, which those are harder to detect, or a giant solar flare that shorts out the
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grid in all of North America, let's say.
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Now, astronomers are monitoring the sun 24 seven with various satellites and we can tell
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when there's a flare or a coronal mass ejection and we can tell that in a day or two, a giant
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bundle of energetic particles will arrive and twang the magnetic field of earth and
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send all kinds of currents through long distance power lines and that's what shorts out the
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transformers and transformers are expensive and hard to replace and hard to transport
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and all that kind of stuff.
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So if we can warn the power companies and they can shut down the grid before the big
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bundle of particle hits, then we will have mitigated much of this.
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Now for a big enough bundle of particles, you can get short circuits even over small
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distance scales, so not everything will be saved, but at least the whole grid might not
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So again, astronomers, I like to say, support your local astronomer, they may help someday
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save humanity by telling the power companies to shut down the grid, finding the asteroid
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50 or 100 years before it hits, then having clever physicists and engineers deflect it.
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So many of these cosmic threats, cosmic existential threats, we can actually predict and do something
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about or observe before they hit and do something about.
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So it's terrifying to think that people would listen to this conversation.
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It's like when you listen to Bill Gates talk about pandemics in his Ted talk a few years
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ago and realizing we should have supported our local astronomer more.
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Well, I don't know whether it's more because as I said, I actually think human induced
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threats or things that occur naturally on earth, either a natural pandemic or perhaps
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a bioengineering type pandemic or something like a super volcano.
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There was one event towed by I think it was 70 plus thousand years ago that caused a gigantic
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decrease in temperatures on earth because it sent up so much soot that it blocked the
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It's the nuclear winter type disaster scenario that some people including Carl Sagan talked
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about decades ago.
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What we can see in the history of volcanic eruptions even more recently in the 19th century,
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Tambora and other ones, you look at the record and you see rather large dips in temperature
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associated with massive volcanic eruptions.
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Well these super volcanoes, one of which by the way exists under Yellowstone in the central
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US, it's not just one or two states, it's a gigantic region and there's controversy
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as to whether it's likely to blow anytime in the next 100,000 years or so.
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But that would be perhaps not a mass extinction or perhaps not a complete existential threat
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because you have to get rid of the very last humans for that, but at least getting rid
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of killing off so many humans, truly billions and billions of humans.
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There have been ones tens of thousands of years ago including this one, Toba I think
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it's called, where it's estimated that the human population was down to 10,000 or 5,000
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individuals, something like that.
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If you have a 15 degree drop in temperature over quite a short time, it's not clear that
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even with today's advanced technology, we would be able to adequately respond at least
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for the vast majority of people.
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Maybe some would be in these underground caves where you'd keep the president and a bunch
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of other important people, but the typical person is not going to be protected when all
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of agriculture is cut off.
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It could be hundreds of millions or billions of people starving to death.
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They don't all die immediately, but they use up their supplies or again, this electrical
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First of toilet paper.
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Dash that toilet paper or the electrical grid.
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Imagine North America without power for a year.
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We've become so dependent, we're no longer the cave people.
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They would do just fine.
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What do they care about the electrical grid?
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What do they care about agriculture, their hunters and gatherers?
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But we now have become so used to our way of life that the only real survivors would
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be those rugged individualists who live somewhere out in the forest or in a cave somewhere,
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completely independent of anyone else.
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Recently I recommended, it's totally new to me, this kind of survivalist folks, but there's
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There's a lot of shows of those, but I saw one on Netflix and I started watching them
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and they make a lot of sense.
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They reveal to you how dependent we are on all aspects of this beautiful systems we human
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have built and how fragile they are.
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Incredibly fragile.
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And this whole conversation is making me realize how lucky we are.
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Oh, we're incredibly lucky, but we've set ourselves up to be very, very fragile and
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we are intrinsically complex biological creatures that except for the fact that we have brains
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and minds with which we can try to prevent some of these things or respond to them.
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We as a living organism require quite a narrow set of conditions in order to survive.
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We're not cockroaches.
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We're not going to survive a nuclear war.
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So we're kind of this beautiful dance between, we've been talking about astronomy, that astronomy,
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the stars like inspires everybody and at the same time, there's this pragmatic aspect that
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we're talking about.
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And so I see space exploration as the same kind of way that it's reaching out to other
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planets, reaching out to the stars, this really beautiful idea.
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But if you listen to somebody like Elon Musk, he talks about space exploration as very pragmatic.
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Like we have to be, he has this ridiculous way of sounding like an engineer about it,
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which is like, it's obvious we need to become a multi planetary species if we were to survive
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So maybe both philosophically in terms of beauty and in terms of practical, what's your
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thoughts on space exploration, on the challenges of it, on how much we should be investing
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in it and on a personal level, like how excited you are by the possibility of going to Mars,
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colonizing Mars and maybe going outside the solar system.
link |
You know, great question.
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There's a lot to unpack there of course.
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Humans are by their very nature explorers, pioneers.
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They want to go out, climb the next mountain, see what's behind it, explore the option depths,
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This is our destiny to go out there.
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And of course, from a pragmatic perspective, yes, we need to plant our seeds elsewhere
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really because things could go wrong here on Earth.
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Now some people say that's an excuse to not take care of our planet.
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Well, we say we're elsewhere and so we don't have to take good care of our planet.
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No, we should take the best possible care of our planet.
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We should be cognizant of the potential impact of what we're doing.
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Nevertheless, it's prudent to have us be elsewhere as well.
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So in that regard, I actually agree with Elon.
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It'd be good to be on Mars.
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That would be yet another place for us from which to explore further.
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Would that be a good next step?
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Well, it's a good next step.
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I happen to disagree with him as to how quickly it will happen.
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I think he's very optimistic.
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Now you need visionary people like Elon to get people going and to inspire them.
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I mean, look at the success he's had with multiple companies.
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So maybe he gives this very optimistic timeline in order to be inspirational to those who
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are going out there.
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And certainly his success with the rocket that is reusable because it landed upright
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I mean, that's a game changer.
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It's sort of like every time you flew from San Francisco to Los Angeles, you discard
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the airplane, right?
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I mean, that's crazy, right?
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So that's a game changer.
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But nevertheless, the timescale over which he thinks that there could be a real thriving
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colony on Mars, I think is far too optimistic.
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What's the biggest challenges to you?
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One is just getting rockets, not rockets, but people out there and two is the colonization.
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Do you have thoughts about this, the challenges of this kind of prospect?
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Yeah, I haven't thought about it in great detail other than recognizing that Mars is
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a harsh environment.
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You don't have much of an atmosphere there.
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You've got less than a percent of Earth's atmosphere.
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So you'd need to build some sort of a dome right away, right?
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And that would take time.
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You need to melt the water that's in the permafrost or have canals dug from which you transport
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it from the polar ice caps.
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You know, I was reading recently in terms of like, what's the most efficient source
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of nutrition for humans that were to live on Mars?
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And people should look into this, but it turns out to be insects.
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So you want, you want to build giant colonies of insects and just be eating them.
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Yeah, insects have a lot of protein.
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Yeah, a lot of protein.
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And they're easy to grow.
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Like you can think of them as farming.
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But it's not going to be as easy as growing a whole plot of potatoes like in the movie
link |
The Martian, you know, or something, right?
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It's not going to be that easy.
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But you know, so there's this thin atmosphere.
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It's got the wrong composition.
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It's mostly carbon dioxide.
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There are these violent dust storms.
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The temperatures are generally cold.
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You know, you'd need to do a lot of things.
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You need to terraform it basically in order to make it nicely livable without some dome
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And if you, and if you insist on a dome, well, that's not going to house that many people,
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You know, so let's look, let's look briefly then, you know, we're looking for a new apartment
link |
So let's look outside the solar system.
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Do you think you've, you've spoken about exoplanets as well?
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Do you think there's possible homes out there for us outside of our solar system?
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There are lots and lots of homes.
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There are, there's a planetary system around nearly every star you see in the sky.
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And one in five of those is thought to have a roughly Earth like planet.
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And that's a relatively new discovery.
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It's a new discovery.
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I mean, the Kepler satellite, which was flying around above Earth's atmosphere was able to
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monitor the brightness of stars with exquisite detail.
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And they could detect planets crossing the line of sight between us and the star, thereby
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dimming its light for a short time ever so slightly.
link |
So there are now thousands and thousands of these exoplanet candidates of which something
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like 90% are probably genuine exoplanets.
link |
And you have to remember that only about 1% of stars have their planetary system oriented
link |
edge on to your line of sight, which is what you need for this transit method to work,
link |
Your planetary angle won't work and certainly perpendicular to your line of sight.
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That is in the plane of the sky won't work because the planet is orbiting the star and
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never crossing your line of sight.
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So the fact that they found planets orbiting about 1% of the stars that they looked at
link |
in this field of 150 plus thousand stars, they found planets around 1%.
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You then multiply by the inverse of 1%, which is 1% is about what the fraction of the stars
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that have their planetary system oriented the right way.
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And that already back of the envelope calculation tells you that of order 50 to 100% of all
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stars have planets.
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And then they've been finding these Earth like planets, et cetera, et cetera.
link |
So there are many potential homes.
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The problem is getting there.
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So then a typical bright star, Sirius, the brightest star in the sky, maybe not a typical
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bright star, but it's 8.7 light years away.
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So that means the light took 8.7 years to reach us.
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We're seeing it as it was about nine years ago.
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So then you ask how long would a rocket take to get there at Earth's escape speed, which
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is 11 kilometers per second.
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And it turns out it's about a quarter of a million years.
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Now that's 10,000 generations.
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Let's say a generation of humans is 25 years.
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So you'd need this colony of people that is able to sustain itself, all their food, all
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their waste disposal, all their water, all the recycling of everything.
link |
For 10,000 generations, they have to commit themselves to living on this vehicle.
link |
I just don't see it happening.
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What I see potentially happening, if we avoid self destruction, intentional or unintentional
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here on Earth, is that machines will do it, robots that can essentially hibernate.
link |
They don't need to do much of anything for a long, long time as they're traveling.
link |
And moreover, if some energetic charged particle, some cosmic ray, hits the circuitry, it fixes
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Machines can do this.
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It's a form of artificial intelligence.
link |
You just tell the thing, fix yourself basically.
link |
And then when you land on the planet, start producing copies of yourself, initially from
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materials that were perhaps sent, or you just have a bunch of copies there.
link |
And then they set up factories with which to do this.
link |
This is very, very futuristic, but it's much more feasible, I think, than sending flesh
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and blood over interstellar distances, a quarter of a million years to even the nearest stars.
link |
You're subject to all kinds of charged particles and radiation.
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You have to shield yourself really well.
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That's by the way, one of the problems of going to Mars is that it's not a three day
link |
journey like going to the moon.
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You're out there for the better part of a year or two, and you're exposed to lots of
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radiation, which typically doesn't do well with living tissue, or living tissue doesn't
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do well with the radiation.
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And the hope is that the robots, the AI systems might be able to carry the fire of consciousness,
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whatever makes us humans, like a little drop of whatever makes us humans so special, not
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to be too poetic about it.
link |
No, but I like being poetic about it because it's an amazing question.
link |
Is there something beyond just the bits, the ones and zeros to us?
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It's an interesting question.
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I like to think that there isn't anything, and that how beautiful it is that our thoughts,
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our emotions, our feelings, our compassion all come from these ones and zeros, right?
link |
That to me actually is a beautiful thought.
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And the idea that machines, silicon based life effectively, could be our natural evolutionary
link |
descendants, not from a DNA perspective, but they are our creations and they then carry
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That to me is a beautiful thought in some ways, but others find it to be a horrific
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So that's exciting to you.
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It is exciting to me as well because to me, from a purely an engineering perspective,
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I believe it's impossible to create, like whatever systems we create that take over
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the world, it's impossible for me to imagine that those systems will not carry some aspect
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of what makes humans beautiful.
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So like a lot of people have these kind of paperclip ideas that we'll build machines
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that are cold inside or philosophers call them zombies.
link |
That naturally the systems that will out compete us on this earth will be cold and non conscious,
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not capable of all the human emotions and empathy and compassion and love and hate,
link |
the beautiful mix of what makes us human.
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But to me, intelligence requires all of that.
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So in order to out compete humans, you better be good at the full picture.
link |
So artificial general intelligence, in my view, encompasses a lot of these attributes
link |
that you just talked about, curiosity, inquisitiveness, you know, right?
link |
It might look very different than us humans, but it will have some of the magic.
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But it'll also be much more able to survive the onslaught of existential threats that
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either we bring upon ourselves or don't anticipate here on earth, or that occasionally come from
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beyond and there's nothing much we can do about a supernova explosion that just suddenly
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And really, if we want to move to other planets outside our solar system, I think realistically
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that's a much better option than thinking that humans will actually make these gigantic
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And, you know, then I do this calculation for my class, you know, Einstein's special
link |
theory of relativity says that you can do it in a short amount of time in your own frame
link |
of reference if you go close to the speed of light.
link |
But then you bring in E equals MC squared and you figure out how much energy it takes
link |
to get you accelerated to close enough to the speed of light to make the time scales
link |
short in your own frame of reference.
link |
And the amount of energy is just unfathomable, right?
link |
We can do it at the Large Hadron Collider with protons, you know, we can accelerate
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them to 99.9999% of the speed of light, but that's just a proton.
link |
We're gazillions of protons, okay?
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And that doesn't even count the rocket that would carry us, the payload.
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And you would need to either store the fuel in the rocket, which then requires even more
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mass for the rocket or collect fuel along the way, which, you know, is difficult.
link |
And so getting close to the speed of light, I think, is not an option either other than
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for a little tiny thing like, you know, Yuri Milner and others are thinking about this,
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the Starshot project where they'll send a little tiny camera to Alpha Centauri 4.2 light
link |
They'll zip past it, take a picture of the exoplanets that we know, orbit that three
link |
or more star system and say hello real quick.
link |
Say hello real quickly and then send the images back to us, okay?
link |
So that's a tiny little thing, right?
link |
Maybe you can accelerate that to, they're hoping, 20% of the speed of light with a whole
link |
bunch of high powered lasers aimed at it.
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It's not clear that other countries will allow us to do that, by the way, but that's a very
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forward looking thought.
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I mean, I very much support the idea, but there's a big difference between sending a
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little tiny camera and sending a payload of people with equipment that could then mine
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the resources on the exoplanet that they reach and then go forth and multiply, right?
link |
Well, let's talk about the big galactic things and how we might be able to leverage them
link |
I know this is a little bit science fiction, but, you know, ideas of wormholes and ideas
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at the edge of black holes that reveal to us that this fabric of space time could be
link |
messed with, perhaps.
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Is that at all an interesting thing for you?
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I mean, in looking out at the universe and studying it as you have, is that also a possible,
link |
like a dream for you that we might be able to find clues how we can actually use it to
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improve our transportation?
link |
It's an interesting thought.
link |
I'm certainly excited by the potential physics that suggests this kind of faster than light
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travel effectively or, you know, cutting the distance to make it very, very short through
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a wormhole or something like that.
link |
Well, you know, call me not very imaginative, but based on today's knowledge of physics,
link |
which I realize, you know, people have gone down that rabbit hole and, you know, a century
link |
ago, Lord Kelvin, one of the greatest physicists of all time, said that all of fundamental
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physics is done, the rest is just engineering, and guess what?
link |
Then came special relativity, quantum physics, general relativity, how wrong he was.
link |
So let me not be another Lord Kelvin.
link |
On the other hand, I think we know a lot more now about what we know and what we don't know
link |
and what the physical limitations are.
link |
And to me, most of these schemes, if not all of them, seem very farfetched, if not impossible.
link |
So travel through wormholes, for example, you know, it appears that for a non rotating
link |
black hole, that's just a complete no go because the singularity is a point like singularity
link |
and you have to reach it to traverse the wormhole and you get squished by the singularity, okay?
link |
Now for a rotating black hole, it turns out there is a way to pass through the event horizon,
link |
the boundary of the black hole, and avoid the singularity and go out the other side
link |
or even traverse the donut hole like singularity.
link |
In the case of a rotating black hole, it's a ring singularity.
link |
So there's actually two theoretical ways you could get through a rotating black hole or
link |
a charged black hole, not that we expect charged black holes to exist in nature because they
link |
would quickly bring in the opposite charge so as to neutralize themselves.
link |
But rotating black holes, definitely a reality.
link |
We now have good evidence for them.
link |
Do they have traversable wormholes?
link |
Probably not because it's still the case that when you go in, you go in with so much energy
link |
that it either squeezes the wormhole shut or you encounter a whole bunch of incoming
link |
and outgoing energy that vaporizes you.
link |
It's called the mass inflation instability, and it just sort of vaporizes you.
link |
Nevertheless, you could imagine, well, you're in some vapor form, but if you make it through,
link |
maybe you could reform or something.
link |
So it's still information.
link |
Yeah, it's still information.
link |
It's scrambled information, but there's a way maybe of bringing it back, right?
link |
But then the thing that really bothers me is that as soon as you have this possibility
link |
of traversal of a wormhole, you have to come to grips with a fundamental problem, and that
link |
is that you could come back to your universe at a time prior to your leaving, and you could
link |
essentially prevent your grandparents from ever meeting.
link |
This is called the grandfather paradox, right?
link |
And if they never met, and if your parents were never born, and if you were never born,
link |
how would you have made the journey to prevent the history from allowing you to exist, right?
link |
It's a violation of causality, of cause and effect.
link |
Now physicists such as myself take causality violation very, very seriously.
link |
We've never seen it.
link |
Yeah, I mean, it's one of these back to the future type movies, right?
link |
And you have to work things out in such a way that you don't mess things up, right?
link |
Some people say that, well, you come back to the universe, but you come back in such
link |
a way that you cannot affect your journey.
link |
But then that seems kind of contrived to me.
link |
Or some say that you end up in a different universe, and this also goes into the many
link |
different types of the multiverse hypothesis and the many worlds interpretation and all
link |
And then it's not the universe from which you left, right?
link |
And you don't come back to the universe from which you left.
link |
And so you're not really going back in time to the same universe, and you're not even
link |
going forward in time necessarily then to the same universe, right?
link |
You're ending up in some other universe.
link |
So what have you achieved, right?
link |
You ended up in a different place than you started in more ways than one.
link |
And then there's this idea, the Alcubierre drive, where you warp space time in front
link |
of you so as to greatly reduce the distance, and you can expand the space time behind you.
link |
So you're sort of riding a wave through space time.
link |
But the problem I see with that, beyond the practical difficulties and the energy requirements,
link |
and by the way, how do you get out of this bubble through which you're riding this wave
link |
And Miguel Alcubierre acknowledged all these things.
link |
He said this is purely theoretical, fanciful, and all that.
link |
But a fundamental problem I see is that you'd have to get to those places in front of you
link |
so as to change the shape of space time so as to make the journey quickly.
link |
But to get there, you got there in the normal way at a speed considerably less than that
link |
So in a sense, you haven't saved any time, right?
link |
You might as well have just taken that journey and gotten to where you were going, right?
link |
What have you done?
link |
It's not like you snap your fingers and say, okay, let that space there be compressed,
link |
and then I'll make it over to Alpha Centauri in the next month.
link |
You can't snap your fingers and do that.
link |
But yeah, we're sort of assuming that we can fix all the biological stuff that requires
link |
for humans to persist through that whole process, because ultimately, it might go down to just
link |
extending the life of the human in some form, whether it's through the robot, through the
link |
digital form, or actually just figuring out genetically how to live forever, because that
link |
journey that you mentioned, the long journey, might be different if somehow our understanding
link |
of genetics, of our understanding of our own biology, all that kind of stuff, that's another
link |
trajectory that possibly...
link |
If you could put us into some sort of suspended animation, hibernation or something, and greatly
link |
increase the lifetime, and so these 10,000 generations I talked about, what do they care?
link |
It's just one generation, and they're asleep, okay?
link |
So then you can do it.
link |
It's still not easy, right?
link |
Because you've got some big old huge colony, and that just through E equals MC squared,
link |
That's a lot of mass.
link |
That's a lot of stuff to accelerate.
link |
The Newtonian kinetic energy is gigantic, right?
link |
So you're still not home free, but at least you're not trying to do it in a short amount
link |
of clock time, right?
link |
Which if you look at E equals MC squared, requires truly unfathomable amounts of energy,
link |
because the energy is your rest mass, M naught C squared, divided by the square root of one
link |
minus V squared over C squared.
link |
And if your listeners want to just sort of stick into their pocket calculator, as V over
link |
C approaches one, that one over the square root of one minus V squared over C squared
link |
approaches infinity.
link |
So if you wanted to do it in zero time, you'd need an infinite amount of energy.
link |
That's basically why you can't reach, let alone exceed the speed of light, for a particle
link |
moving through a preexisting space.
link |
It's that it takes an infinite amount of energy to do so.
link |
So that's talking about us going somewhere.
link |
What about, one of the things that inspires a lot of folks, including myself, is the possibility
link |
that there's other, that this conversation is happening on another planet in different
link |
forms with intelligent life forms.
link |
So first we could start, as a cosmologist, what's your intuition about whether there
link |
is or isn't intelligent life out there?
link |
Outside of our own?
link |
Yeah, I would say I'm one of the pessimists in that I don't necessarily think that we're
link |
the only ones in the observable universe, which goes out, you know, roughly 14 billion
link |
years in light travel time and more like, you know, 46 billion years when you take into
link |
account the expansion of space.
link |
So the diameter of our observable universe is something like, you know, 90, 92 billion
link |
That encompasses, you know, a hundred billion to a trillion galaxies with, you know, a hundred
link |
billion stars each.
link |
So now you're talking about something like 10 to the 22nd, 10 to the 23rd power stars
link |
and roughly an equal number of Earth like planets and so on.
link |
So there may well be other intelligent life.
link |
But your sense is our galaxy is not teeming with life.
link |
Yeah, our galaxy, our Milky Way galaxy with several hundred billion stars and potentially
link |
habitable planets is not teeming with intelligent life.
link |
Yeah, I wouldn't, well, I'll get to the primitive life, the bacteria in a moment, but, you know,
link |
we may well be the only ones in our Milky Way galaxy, at most a handful, I'd say, but
link |
I'd probably side with the school of thought that suggests we're the only ones in our own
link |
galaxy, just because I don't see human intelligence as being a natural evolutionary path for life.
link |
I mean, there's a number of arguments.
link |
First of all, there's been more than 10 billion species of life on Earth in its history.
link |
Everything has approached our level of intelligence and mechanical ability and curiosity.
link |
You know, whales and dolphins appear to be reasonably intelligent, but there's no evidence
link |
that they can think abstract thoughts that they're curious about the world.
link |
They certainly can't build machines with which to study the world.
link |
So that's one argument.
link |
Secondly, we came about as early hominids only four or five million years ago and as
link |
homo sapiens only about a quarter of a million years ago.
link |
So for the vast majority of the history of life on Earth, an intelligent alien zipping
link |
by Earth would have said there's nothing particularly intelligent or mechanically able on Earth.
link |
Thirdly, it's not clear that our intelligence is a long term evolutionary advantage.
link |
Now it's clear that in the last 100 years, 200 years, we've improved the lives of hundreds
link |
of millions of people, but at the risk of potentially destroying ourselves either intentionally
link |
or unintentionally or through neglect, as we discussed before.
link |
That's a really interesting point, which is it's possible that they're a huge amount of
link |
intelligent civilizations have been born even through our galaxy, but they live very briefly
link |
Flash bulbs in the night.
link |
That brings me to the fourth issue and that is the Fermi paradox.
link |
If they're common, where the hell are they?
link |
Notwithstanding the various UFO reports in Roswell and all that, they just don't meet
link |
They don't clear the bar of scientific evidence in my opinion.
link |
So there's no clear evidence that they've ever visited us on Earth here.
link |
And SETI has been now, the search for extraterrestrial intelligence has been scanning the skies and
link |
true, we've only looked a couple of hundred light years out and that's a tiny fraction
link |
of the whole galaxy, a tiny fraction of these hundred billion plus stars.
link |
Nevertheless, if the galaxy were teaming with life, especially intelligent life, you'd expect
link |
some of it to have been far more advanced than ours.
link |
There's nothing special about when the industrial revolution started on Earth.
link |
The chemical evolution of our galaxy was such that billions of years ago, nuclear processing
link |
and stars had built up clouds of gas after their explosion that were rich enough in heavy
link |
elements to have formed Earth like planets, even billions of years ago.
link |
So there could be civilizations that are billions of years ahead of ours.
link |
And if you look at the exponential growth of technology among Homo sapiens in the last
link |
couple of hundred years and you just project that forward, I mean, there's no telling what
link |
they could have achieved even in 1000 or 10,000 years, let alone a million or 10 million or
link |
And if they reach this capability of interstellar travel and colonization, then you can show
link |
that within 10 million years or certainly a hundred million years, you can populate
link |
So then you don't have to have tried to detect them beyond a hundred or a thousand light
link |
They would already be here.
link |
Do you think as a thought experiment, do you think it's possible that they are already
link |
here, but we humans are so human centric that we're just not like our conception of what
link |
intelligent life looks like is, we don't want to acknowledge it.
link |
Like what if trees?
link |
Okay, I guess the, in the form of a question, do you think we'll actually detect intelligent
link |
life if it came to visit us?
link |
I mean, it's like, you know, you're an ant crawling around on a sidewalk somewhere and
link |
do you notice the humans wandering around and the empire state building and you know,
link |
rocket ships flying to the moon and all that kind of stuff, right?
link |
It's conceivable that we haven't detected it and that we're so primitive compared to
link |
them that we're just not able to do so.
link |
Like if you look at dark energy, maybe we call it as a field.
link |
It's just that my own feeling is that in science now through observations and experiments,
link |
we've measured so many things and basically we understand a lot of stuff.
link |
Fabric of reality.
link |
The fabric of reality, we understand quite well.
link |
And there are a few little things like dark matter and dark energy that may be some sign
link |
of some super intelligence, but I doubt it.
link |
You know, why would some super intelligence be holding clusters of galaxies together?
link |
Why would they be responsible for accelerating the expansion of the universe?
link |
So the point is, is that through science and applied science and engineering, we understand
link |
so much now that I'm not saying we know everything, but we know a hell of a lot.
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And so there's, it's not like there are lots of mysteries flying around there that are
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completely outside our level of exploration or understanding.
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From a, I would say from, from a mystery perspective, it seems like the mystery of our own like
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cognition and consciousness is much grander than like the degrees of freedom of possible
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explanations for what the heck is going on is much greater there than in the, in the
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physics of the observed.
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How the brain works.
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How did life arise?
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That's big, big questions.
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But they, to me, don't indicate the existence of, of, of an alien or something.
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I mean, unless we are the aliens, you know, we could have been contamination from some
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rocket ship that, that hit here a long, long time ago and all evidence of it has been destroyed.
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But again, that alien would have started out somewhere.
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They're not, they're not here watching us right now, right?
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They're not among us.
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And so though there are expert potential explanations for the Fermi paradox, and one of them that
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I kind of like is that the truly intelligent creatures are those that decided not to colonize
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the whole galaxy because they'd quickly run out of room there because it's exponential,
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You send a probe to a planet, it makes two copies, they go out, they make two copies
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each and it's an exponential, right?
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They quickly colonize the whole galaxy.
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But then the distance to the next galaxy, the next big one like Andromeda, that's two
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and a half million light years.
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That's a much grander scale now, right?
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And so it also could be that the reason they survived this long is that they got over this
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tendency that may well exist among sufficiently intelligent creatures, this tendency for aggression
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and self destruction, right?
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If they bypass that, and that may be one of the great filters if there are more than one,
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Then they may not be a type of creature that feels the need to go and say, oh, there's
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a nice looking planet and there's a bunch of ants on it, let's go squish them and colonize
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No, it could even be the kind of Star Trek like prime directive where you go and explore
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worlds, but you don't interfere in any way, right?
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And also we call it exploration is beautiful and everything, but there is underlying this
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desire to explore is a desire to conquer.
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I mean, if we're just being really honest right now for us, it is right.
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And you're saying it's possible to separate, but I would venture to say that you wouldn't
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that those are coupled.
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So I could, I could imagine a civilization that lives on for billions of years that just
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stays on, it's like figures out the minimal effort way of just peacefully existing.
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It's like a monastery.
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And it limits itself.
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You know, it's, it's planted its seeds in a number of places.
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So it's not vulnerable to a single point failure, right?
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Supernova going off near one of these stars or something, or an asteroid or a comet coming
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in from the Oort cloud equivalent of that planetary system and without warning, you
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know, thrashing them to bits.
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So they've got their seeds in a bunch of places, but they chose not to colonize, colonize the
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And they also choose not to interfere with this incredibly prevalent, primitive organism
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homo sapiens, right?
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Or they, uh, this is like a, they enjoy, this is like a TV show for them.
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It could be like a TV show.
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So they just tuned in.
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There are no other possible explanations yet.
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I think that to me, the most likely explanation for the peri me paradox is that they really
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are very, very rare.
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And you know, Carl Sagan estimated a hundred thousand of them.
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If there's that many, some of them would have been way ahead of us and, and I think we would
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have seen them by now.
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If there are a handful, maybe they're there.
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But at that point, you're right on this dividing line between being a pessimist and an optimist.
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And what are the odds for that?
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What are the things that had to go right for us?
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And then, you know, getting back to something you said earlier, let's discuss, you know,
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That could be the thing that's difficult to achieve.
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Just getting the random molecules together to a point where they start self replicating
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and evolving and becoming better and all that.
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That's an inordinately difficult thing, I think, though I'm not, you know, some molecular
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or cell biologist, but just it's, it's, it's the usual argument.
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You know, you're wandering around in the Sahara desert and you stumble across a watch.
link |
Is your, is your initial response, oh, you know, a bunch of sand grains just came together
link |
randomly and formed this watch.
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No, you, you think that something formed it or it came from some simpler structure that
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then became, you know, more complex.
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It didn't just form.
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Well, even the simplest life is, is a very, very complex structure.
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Even the, even the simplest prokaryotic cells, not to mention eukaryotic cells, although
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that transition may have been the so called great filter as well.
link |
Maybe the cells without a nucleus are relatively easy to form.
link |
And then the big next step is where you have a nucleus, which then provides a lot of energy,
link |
which allows the cell to become much, much more complex and so on.
link |
Interestingly, going from eukaryotic cells, single cells to multicellular organisms does
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not appear to be, at least on earth, one of these great filters because there's evidence
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that it happened dozens of times independently on earth.
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So by, by a really great filter, something that happens very, very rarely, I mean that
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we had to get through an obstacle that is just incredibly rare to get through.
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And one of the really exciting scientific things is that that particular point is something
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that we might be able to discover, even in our lifetimes that find life elsewhere like
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Europa or be able to see that would be bad news, right?
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Because if we find lots of pretty advanced life, yeah, that would suggest, and especially
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if we found some, you know, defunct, you know, fossilized civilization or something somewhere
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else that would be bacteria, you mean, defunct civilization of like, oh, I'm sorry, I switched
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If we, if we found some intelligent or even trilobites right and stuff, you know, elsewhere,
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that would be bad news for us because that would mean that the great filter is ahead
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of us, you know, right, because it would mean that lots of, lots of things have gotten roughly
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But, but given the Fermi paradox, if you accept that the Fermi paradox means that there's
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no one else out there, you don't necessarily have to accept that, but if you accept that
link |
it means that no one else is out there and yet there are lots of things we found that
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are at or roughly at our level, that means that the great filter is ahead of us and that
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bodes poorly for our longterm future, you know, it's funny you said, uh, you started by saying
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you're a little bit on the pessimistic side, but it's funny because we're doing this kind
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of dance between pessimism and optimism because I'm not sure if us being alone in the observable
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universe as intelligent beings is pessimistic, well, it's good news in a sense for us because
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it means that we made it through, see, if we're the only ones and there are such great
link |
filters, maybe more than one formation of life might be one of them formation of eukaryotic
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that is with the nucleus cells being another development of human like intelligence might
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be another, right?
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There might be several such filters and we were the lucky ones.
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And you know, then people say, well then that means you're putting yourself into a special
link |
perspective and every time we've done that we've been wrong and yeah, yeah, I know all
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those arguments, but it still could be the case that there's one of us at least per galaxy
link |
or pretend or a hundred or a thousand galaxies and we're sitting here having this conversation
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And so there's a, there's an observational selection effect there, right?
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Just because we're special doesn't mean that we shouldn't have these conversations about
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whether or not we're special, right?
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Yeah, so that's, that's so exciting.
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That's optimistic.
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So that's the, that's the optimistic part that if we don't find other intelligent life
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there, it might mean that we're the ones that made it.
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And in general, outside the great filter and so on, you know, it's not obvious that the
link |
Stephen Hawking thing, which is, it's not obvious that life out there is going to be kind to
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So, you know, I knew Hawking and I greatly respect his, his scientific work and in particular
link |
the early work on the unification of general theory of relativity and quantum physics to
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two great pillars in modern physics, you know, Hawking radiation and all that fantastic work.
link |
You know, if you were alive, you should have been a recipient of this year's physics Nobel
link |
prize, which was for the discovery of black holes and also by Roger Penrose for the theoretical
link |
work showing that given a star that's massive enough, you basically can't avoid having a
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Anyway, Hawking, fantastic.
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I, I tip my hat to him.
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May he rest in peace.
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That would have been a heck of a Nobel prize, black holes, heck of a good group.
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But, but, but going back to what he said that we shouldn't be broadcasting our presence
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to others there, I actually disagree with him respectfully because first of all, we've
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been unintentionally broadcasting our presence for a hundred years since the development
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Secondly, any alien that has the capability of coming here and squashing us either already
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knows about us and you know, doesn't care because we're just like little ants.
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And when there are ants in your kitchen, you tend to squash them.
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But if there are ants on the sidewalk and you're walking by, do you feel some great
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conviction that you have to squash any of them?
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No, you generally don't, right?
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We're irrelevant to them.
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All they need to do is keep an eye on us to see whether we're approaching the kind of
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technological capability and know about them and have intentions of attacking them.
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And then they can squash us, right?
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Um, you know, they, they could have done it long ago.
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They'll, they'll do it if they want to, whether we advertise our presence or not is, is irrelevant.
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So I really think that that's not a huge existential threat.
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So this is a good place to bring up a difficult topic.
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You mentioned, um, they might, they would be paying attention to us to see if we come
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up with any crazy technology.
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There's folks who have reported UFO sightings.
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There's actually, I've recently found out there's a websites that track this, the data,
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the data of these reportings, and there's millions of them in the past, uh, several
link |
So seven decades and so on that they've been recorded and the ufologist community, as they
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refer to themselves, you know, one of the ideas that I find compelling from an alien
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perspective that they kind of started showing up ever since we figured out how to build
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nuclear weapons that we should, uh, so I mean, you know, if I was an LA and I would start
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showing up then as well, just, well, why not just observe us from afar?
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I would figure out, but that's why I'm always, uh, keeping a distance and staying blurry,
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but very pixelated, very pixelated, you know, that there is a something in the human condition
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that a cognition that wants to see, wants to believe beautiful things and, uh, some
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are terrifying, some are exciting, uh, goats, Bigfoot is a big fascination for folks.
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And, uh, UFO sightings, I think falls into that.
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There's people that look at lights in the night sky and I mean, there's, it's kind of
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a downer to think in a skeptical sense, to think that that's just a light.
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You want to feel like there's something magical there.
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Uh, I mean, I felt that first when my dad, my dad's a physicist, when he first told me
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about ball lightning when I was like a little kid, very weird, very like weird physical
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And he said, his intuition was telling me this as a little kid, uh, like, I really like
link |
His intuition was whoever figures out ball lightning, we'll get a Nobel prize.
link |
Like he, I think that was a side comment he gave me and I decided there when I was like
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five years old or whatever, I'm going to win a Nobel prize for figuring out ball lightning.
link |
That was like one of the first sort of sparks of the scientific mindset.
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Those mysteries, they capture your imagination.
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I think when I speak to people that report UFOs, that's that fire.
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That's what I see.
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And I understand that.
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But what, what do we do with that?
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Because there's hundreds of thousands, if not millions, and then the scientific community,
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you're like the perfect person.
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You have an awesome Einstein shirt.
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What, what do we do with those reports?
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It's a, most of the scientific community kind of rolls their eyes and dismisses it.
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Is it possible that a tiny percent of those folks saw something that's worth deeply investigating?
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We should investigate it.
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It's just one of these things where, you know, they've not brought us a hunk of kryptonite
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or something like that, right?
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They haven't brought us actual tangible physical evidence with which experiments can be done
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It's, it's anecdotal evidence.
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The photographs are, in some cases, in most cases, I would say quite ambiguous.
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I don't know what to think about.
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So David Faber is the first person.
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He's a Navy pilot, commander, and there's a bunch of them, but he's sort of one of the
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most legit pilots and people I've ever met.
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The fact that he saw something weird, he doesn't know what the heck it is, but he saw something
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I mean, I don't know what to do with that.
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And one on the psychological side, so I'm pretty confident he saw what he says he saw,
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which he's not, he's saying it's something weird.
link |
One of the interesting psychological things that worries me is that everybody in the Navy,
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everybody in the US government, everybody in the scientific community, just kind of
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like pretended that nothing happened.
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That kind of instinct.
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That's what makes me believe if aliens show up, we would all like just ignore their presence.
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That's what bothered me that you don't, you don't investigate it more carefully and use
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this opportunity to inspire the world.
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So in terms of kryptonite, I think the conspiracy theory folks say that whenever there is some
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good hard evidence that scientists would be excited about, there's this kind of conspiracy
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that I don't like because it's ultimately negative that the US government will somehow
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hide the good evidence to protect it.
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Of course, there's some legitimacy to it because you want to protect military secrets, all
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that kind of stuff.
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But I don't know what to do with this beautiful mess because I think millions of people are
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inspired by UFOs and it feels like an opportunity to inspire people about science.
link |
So I would say, as Carl Sagan used to say, extraordinary claims require extraordinary
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I've quoted him a number of times.
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We would welcome such evidence.
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On the other hand, a lot of the things that are seen or perhaps even hidden from us, you
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could imagine for military purposes, surveillance purposes, the US government doesn't want us
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Or maybe some of these pilots saw Soviet or Israeli or whatever satellites or some of
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the crashes that have occurred were later found to be weather balloons or whatever.
link |
When there are more conventional explanations, science tends to stay away from the sensational
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And so it may be that someone else's calling in life is to investigate these phenomena.
link |
And I welcome that as a scientist.
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I don't categorically actually deny the possibility that ships of some sort could have visited
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us because, as I said earlier, at slow speeds, there's no problem in reaching other stars.
link |
In fact, our Voyager and Pioneer spacecraft in a few million years are going to be in
link |
the vicinity of different stars.
link |
We can even calculate which ones they're going to be in the vicinity of, right?
link |
So there's nothing that breaks any laws of physics if you do it slowly.
link |
But that's different, just having Voyager or Pioneer fly by some star, that's different
link |
from having active aliens altering the trajectory of their vehicle in real time, spying on us,
link |
and then either zipping back to their home planet or sending signals that tell them about
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us because they are likely many light years away, and they're not going to have broken
link |
that barrier as well, okay?
link |
So I just, you know, go ahead, study them.
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For some young kid who wants to do it, it might be their calling, and that's how they
link |
might find meaning in their lives, is to be the scientist who really explores these things.
link |
I chose not to because at a very young age, I found the evidence, to the degree that I
link |
investigated it, to be really quite unconvincing, and I had other things that I wanted to do.
link |
But I don't categorically deny the possibility, and I think it should be investigated.
link |
Yeah, I mean, this is one of those phenomena that 99.9% of people are almost definitely,
link |
there's conventional explanations, and then there's like mysterious things that probably
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have explanations that are a little bit more complicated, but there's not enough to work
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I tend to believe that if aliens showed up, there will be plenty of evidence for scientists
link |
And exactly as you said, avoid your type of spacecraft that could see sort of some kind
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of, kind of a dumb thing, almost like a sensor that's like probing, like statistically speaking.
link |
Flying by, maybe lands, maybe there's some kind of robot type of thingies that just like
link |
move around and so on, like in ways that we don't understand.
link |
But I feel like, well, I feel like there'll be plenty of hard, hard to dismiss evidence.
link |
And I also, especially this year, believe that the US government is not sufficiently
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competent given the huge amount of evidence that will be revealed from this kind of thing
link |
to conceal all of it.
link |
At least in modern times, you can say maybe decades ago, but in modern times.
link |
Right, you know, the people I speak to and the reason I bring it up is because so many
link |
people write to me, they're inspired by it.
link |
By the way, I wanted to comment on something you said earlier on, yeah, I had said that
link |
I'm sort of a pessimist in that I think there are very few other intelligent, mechanically
link |
able creatures out there.
link |
But then I said, yes, in a sense, I'm an optimist, as you pointed out, because it means
link |
that we made it through the great filter.
link |
I meant originally that I'm a pessimist in that I'm pessimistic about the possibility
link |
that there are many, many of us out there, you know, mathematically speaking in the Drake
link |
But it may mean a good thing for our ultimate survival.
link |
So I'm glad you caught me on that.
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Yeah, I definitely agree with you.
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It is ultimately an optimistic statement.
link |
But anyway, I think, you know, UFO research is interesting.
link |
And I guess one of the reasons I've not been terribly convinced is that I think there are
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some scientists who are investigating this and they've not found any clear evidence.
link |
Now, I must admit, I have not looked through the literature to convince myself that there
link |
are many scientists doing systematic studies of these various reports.
link |
I can't say for sure that there's a critical mass of them, but it's just that you never
link |
get these reports from hardcore scientists.
link |
That's another thing.
link |
And astronomers, you know, what do we do?
link |
We spend our time studying the heavens and you'd think we'd be the ones that are most
link |
likely aside from pilots, perhaps, at seeing weird things in the sky.
link |
And we just never do of the unexplained UFO type nature.
link |
Yeah, I definitely, I try to keep an open mind, but for people who listen, it's actually
link |
really difficult for scientists.
link |
Like I get probably like this year, I've probably gotten over probably maybe over a thousand
link |
emails on the topic of AGI.
link |
It's very difficult to, you know, people write to me, it's like, how can you ignore this
link |
Like this model, this is obviously the model that's going to achieve general intelligence.
link |
How can you ignore it?
link |
I'm giving you the answer.
link |
Here's my document.
link |
And they're always just these large write ups.
link |
The problem is it's very difficult to weed through a bunch of BS.
link |
It's very possible that you had actually saw the UFO, but you have to acknowledge that
link |
by UFO, I mean, an extraterrestrial life, you have to acknowledge the hundreds of thousands
link |
of people who are a little bit, if not a lot full of BS.
link |
And from a scientist perspective, it's really hard work and it's when there's amazing stuff
link |
out there, it's like, why invest in Bigfoot when evolution in all of its richness is beautiful?
link |
Who cares about a monkey that walks on two feet or eight or whatever?
link |
Like there's a zillion decoys at observatories.
link |
We get lots and lots of phone calls when Venus, the evening star, but just really a bright
link |
planet happens to be close to the crescent moon because it's such a striking pair.
link |
This happens once in a while.
link |
And we get these phone calls, oh, there's a UFO next to the moon.
link |
And no, it's Venus.
link |
And so they're just and I'm not saying the best UFO reports are of that nature.
link |
No, there are some much more convincing cases.
link |
And I've seen some of the footage and blah, blah, blah.
link |
But it's just there's so many decoys, right?
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So much so much noise that you have to filter out.
link |
And there's only so many scientists.
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There's only so much.
link |
There's only so much time as well.
link |
And you have to choose what problems you work on.
link |
You know, this might be a fun question to ask to kind of explore the idea of the expanding
link |
So the the radius of the observable universe is 45.7 billion light years.
link |
And the age of the universe is 13.7 billion years.
link |
That's less than the radius of the universe.
link |
How's that possible?
link |
So that's a great question.
link |
So I meant to bring a little a little prop I have with ping pong balls on a rubber hose,
link |
I use it in many of the lectures that one can find of me online.
link |
But you have in an expanding universe, the space itself between galaxies or more correctly,
link |
clusters of galaxies expanding.
link |
So imagine light going from one cluster to another.
link |
It traverses some distance and then while it's traversing the rest, that part that it
link |
already traveled through continues to expand.
link |
Now 13.7 billion years might have gone by since the light that we are seeing from the
link |
early stages, the so called cosmic microwave background radiation, which is the afterglow
link |
of the Big Bang or the echo of the Big Bang.
link |
Yeah, 13.7 billion years have gone by.
link |
That's how long it's taken that light to reach us.
link |
But while it's been traveling that distance, the parts that it already traveled continue
link |
So it's like you're walking on at an airport, you know, on one of these walkways and you're
link |
walking along because you're trying to get to your terminal.
link |
But the walkway is continuing as well.
link |
You end up traveling a greater distance or the same distance faster is another way of
link |
putting it, right?
link |
That's why you get on one of these traveling walkways.
link |
So you get roughly a factor of pi, you know, but it's more like 3.2, I think.
link |
But when you work it all out, you multiply the number of years the universe has been
link |
in existence by, you know, three and a quarter or so.
link |
And that's how you get this 46 billion light year radius.
link |
But how is that, let me ask some nice dumb questions, how is that not traveling faster
link |
than the speed of light?
link |
Yeah, it's not traveling faster than the speed of light because locally at any point, if
link |
you were to measure the light, the photons zipping past, it would not be exceeding the
link |
The speed of light is a locally measured quantity.
link |
After light has traversed some distance, if the rubber band keeps on stretching, then
link |
yes, it looks like the light traveled a greater distance than it would have had the space
link |
not been expanding.
link |
But locally, it never was exceeding the speed of light.
link |
It's just that the distance through which it already traveled then went off and expanded
link |
on its own some more.
link |
And if you give the light credit, so to speak, for having traversed that distance, well,
link |
then it looks like it's going faster than the speed of light.
link |
But that's not how speed works.
link |
And in relativity, also, the other thing that is interesting is that if you take two ping
link |
pong balls that are sufficiently far apart, especially in an accelerating universe, you
link |
can easily have them moving apart from one another faster than the speed of light.
link |
So take two ping pong balls that were originally 400,000 kilometers from each other and let
link |
every centimeter in your rubber band expand to two in one second.
link |
Then suddenly, this 400,000 kilometer distance is 800,000 kilometers.
link |
It went out by 400,000 kilometers in one second.
link |
That exceeds the 300,000 kilometer per second speed of light.
link |
But that light limit, that particle limit in special relativity, applies to objects
link |
moving through a preexisting space.
link |
There's nothing in either special or general relativity that prevents space itself from
link |
expanding faster than the speed of light.
link |
That's no problem.
link |
Einstein wouldn't have had a problem with a universe as observed now by cosmologists.
link |
Yeah, I'm not sure I'm yet ready to deal emotionally with expanding space.
link |
That to me is one of the most awe inspiring things, starting from the Big Bang.
link |
It's definitely abstract.
link |
Space itself is expanding.
link |
Could you, can we talk about the Big Bang a little bit?
link |
What, so like the entirety of it, the universe, was very small.
link |
But it was not a point.
link |
It was not a point.
link |
Because if we live in what's called a closed universe now, a sphere or the three dimensional
link |
version of that would be a hypersphere, then regardless of how far back in time you go,
link |
it was always that topological shape.
link |
You can't turn a point suddenly into a shell, okay?
link |
It always had to be a shell.
link |
So when people say, well, the universe started out as a point, that's being kind of flippant,
link |
It just started out at a very high density.
link |
And we don't know actually whether it was finite or infinite, I think personally that
link |
it was finite at the time, but it expanded very, very quickly.
link |
Indeed, if it exponentiated and continued in some places to exponentiate, then it could
link |
in fact be infinite right now.
link |
And most cosmologists think that it is infinite.
link |
What infinite, which dimension, mass, size?
link |
Infinite in space.
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Infinite in space.
link |
And by that I mean that if you were trying to measure.
link |
There's no boundary.
link |
There's no light to measure its size.
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You'd never be able to measure its size because it would always be bigger than the distance
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That's what you get in a universe that's accelerating in its expansion.
link |
But if a thing was a hypersphere, it's very small, not a point, how can that thing be
link |
Well, it expands exponentially.
link |
That's what the inflation theory is all about.
link |
Indeed, at your home institution, Alan Guth is one of the originators of the whole inflationary
link |
universe idea, along with Andre Linde at Stanford University here in the Bay Area.
link |
And others, Alexei Starobinsky and others had similar sorts of ideas.
link |
But in an exponentially expanding universe, if you actually try to make this measurement,
link |
you send light out to try to see it curve back around and hit you in the back of the
link |
But in an exponentially expanding universe, the amount of space remaining to be traversed
link |
is always a bigger and bigger quantity.
link |
So you'll never get there from here.
link |
You'll never reach the back of your head.
link |
So observationally or operationally, it can be thought of as being infinite.
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That's one of the best definitions of infinity, by the way.
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That's one of the best sort of physical manifestations of infinity.
link |
Because you have to ask, how would you actually measure it?
link |
Now, I sometimes say to my cosmology theoretical friends, well, if I were God and I were outside
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this whole thing and I took a godlike slice in time, wouldn't it be finite no matter how
link |
And they object and they say, Alex, you can't be outside and take a godlike slice of time,
link |
Because there's nothing outside.
link |
Well, I'm not, you know, or also, you know, what slice of time you're taking depends on
link |
And that's true even in special relativity that slices of time get tilted, in a sense,
link |
if you're moving quickly, the axes, x and t actually become tilted, not perpendicular
link |
And you can look at Brian Greene's books and lectures and other things where he imagines
link |
taking a loaf of bread and slicing it in units of time as you progress forward.
link |
But then if you're zipping along relative to that loaf of bread, the slices of time
link |
actually become tilted.
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And so it's not even clear what slices of time mean.
link |
But I'm an observational astronomer, I know which end of the telescope to look through.
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And the way I understand the infinity is, as I just told you, that operationally or
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observationally, there'd be no way of seeing that it's a finite universe, of measuring
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a finite universe.
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And so in that sense, it's infinite, even if it started out as a finite little dot.
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Not a dot, I'm sorry, a finite little hypersphere.
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But it didn't really start out there because what happened before that?
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Well, we don't know.
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So this is where it gets into a lot of speculation.
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Let's go, I mean...
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The idea of what happened before t equals zero and whether there are other universes
link |
out there, I like to say that these are sort of on the boundaries of science.
link |
They're not just ideas that we wake up at three in the morning to go to the bathroom
link |
and say, oh, well, let's think about what happened before the Big Bang or let there
link |
be a multiplicity of universes.
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In other words, we have real testable physics that we can use to draw certain conclusions
link |
that are plausibility arguments based on what we know.
link |
Now, admittedly, there are not really direct tests of these hypotheses.
link |
That's why I call them hypotheses.
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They're not really elevated to a theory because a theory in science is really something that
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has a lot of experimental or observational support behind it.
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So they're hypotheses, but they're not unreasonable hypotheses based on what we know about general
link |
relativity and quantum physics.
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And they may have indirect tests in that if you adopt this hypothesis, then there might
link |
be a bunch of things you expect of the universe, and lo and behold, that's what we measure.
link |
But we're not actually measuring anything at t less than zero, or we're not actually
link |
measuring the presence of another universe in this multiverse, and yet there are these
link |
indirect ideas that stem forth.
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So it's hard to prove uniqueness, and it's hard to completely convince oneself that a
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certain hypothesis must be true.
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But the more and more tests you have that it satisfies, let's say there are 50 predictions
link |
it makes, and 49 of them are things that you can measure.
link |
And then the 50th one is the one where you want to measure the actual existence of that
link |
other universe, or what happened before t equals zero, and you can't do that.
link |
But you've satisfied 49 of the other testable predictions, and so that's science, right?
link |
Now a conventional condensed matter physicist or someone who deals with real data in the
link |
laboratory might say, oh, you cosmologists, that's not really science because it's not
link |
directly testable, but I would say it's sort of testable.
link |
But it's not completely testable, and so it's at the boundary, but it's not like we're coming
link |
up with these crazy ideas, among them quantum fluctuations out of nothing, and then inflating
link |
into a universe with, you might say, well, you created a giant amount of energy.
link |
But in fact, this quantum fluctuation out of nothing in a quantum way violates the conservation
link |
That was a classical law anyway.
link |
And then an inflating universe maintains whatever energy it had, be it zero or some infinitesimal
link |
In a sense, the stuff of the universe has a positive energy, but there's a negative
link |
gravitational energy associated with it.
link |
It's like I drop an apple.
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I got kinetic energy, energy of motion out of that, but I did work on it to bring it
link |
So by going down and gaining energy of motion, positive one, two, three, four, five units
link |
of kinetic energy, it's also gaining or losing, depending on how you want to think of it,
link |
negative one, two, three, four, five units of potential energy, so the total energy remains
link |
An inflating universe can do that, or other physicists say that energy isn't conserved
link |
in general relativity.
link |
That's another way out of creating a universe out of nothing.
link |
But the point is that this is all based on reasonably well tested physics, and although
link |
these extrapolations seem kind of outrageous at first, they're not completely outrageous.
link |
They're within the realm of what we call science already.
link |
And maybe some young whippersnapper will be able to figure out a way to directly test
link |
what happened before T equals zero or to test for the presence of these other universes,
link |
but right now we don't have a way of doing that.
link |
So speaking of young whippersnappers, Roger Penrose.
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So he kind of has a, you know, idea that we, there may be some information that travels
link |
from whatever the heck happened before the Big Bang.
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I kind of doubt it.
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So do you think it's possible to detect something, like actually experimentally be able to detect
link |
some, I don't know what it is, radiation, some sort of...
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Yeah, and the cosmic microwave background radiation, there may be ways of doing that.
link |
But is it, is it philosophically or practically possible to detect signs that this was before
link |
the Big Bang or is it, or is it what you said, which is like everything we observe will,
link |
as we currently understand, will have to be a creation of this particular observable universe?
link |
I mean, you know, if you, it's very difficult to answer right now because we don't have
link |
a single verified, fully self consistent, experimentally tested quantum theory of gravity.
link |
And of course the beginning of the universe is a large amount of stuff in a very small
link |
So you need both quantum mechanics and general relativity.
link |
Same thing if our universe re collapses and then bounces back to another Big Bang.
link |
You know, there's also ideas there that some of the information leaks through or survives.
link |
I don't know that we can answer that question right now because we don't have a quantum
link |
theory of gravity that most physicists believe in.
link |
And belief is perhaps the wrong word that most physicists trust because the experimental
link |
evidence favors it.
link |
There are various forms of string theory.
link |
There's quantum loop gravity.
link |
There are various ideas, but which, if any, will be the one that survives the test of
link |
time and more importantly, within that, the test of experiment and observation.
link |
So my own feeling is probably these things don't survive.
link |
I don't think we've seen any evidence in the cosmic microwave background radiation
link |
of information leaking through.
link |
Similarly, the one way or one of the few ways in which we might test for the presence of
link |
other universes is if they were to collide with ours, that would leave a pattern, a temperature
link |
signature in the cosmic microwave background radiation.
link |
Some astrophysicists claim to have found it, but in my opinion, it's not statistically
link |
significant to the level that would be necessary to have such an amazing claim, right?
link |
It's just a 5% chance that the microwave background had that distribution just by chance.
link |
5% isn't very long odds if you're claiming that instead that you're finding evidence
link |
from another universe.
link |
I mean, it's like if the Large Hadron Collider people had claimed after gathering enough
link |
data to show the Higgs particle when there was a 5% chance it could be just a statistical
link |
fluctuation in their data.
link |
No, they required 5 sigma, 5 standard deviations, which is roughly one chance in 2 million that
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this is a statistical fluctuation of no physical greater significance.
link |
Extraordinary claims require extraordinary evidence.
link |
It all boils down to that.
link |
And the greater your claim, the greater is the evidence that is needed and the more evidence
link |
you need from independent ways of measuring or of coming to that deduction.
link |
A good example was the accelerating universe.
link |
When we found evidence for it in 1998 with supernovae with exploding stars, it was great
link |
that there were two teams that lent some credibility to the discovery.
link |
But it was not until other astrophysicists used not only that technique, but more importantly,
link |
other independent techniques that had their own potential sources of systematic error
link |
But they all came to the same conclusion and that started giving a much more complete picture
link |
of what was going on and a picture in which most astrophysicists quickly gained confidence.
link |
That's why that idea caught on so quickly is that there were other physicists and astronomers
link |
doing observations completely independent of supernovae that seemed to indicate the
link |
That period of your life that work with an incredible team of people that won the Nobel
link |
Prize is just fascinating work.
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Never in my wildest dreams as a kid did I think that I would be involved, much less
link |
so heavily involved, in a discovery that's so revolutionary.
link |
As a kid, as a scientist, if you're realistic, once you learn a little bit more about how
link |
science is done and you're not going to win a Nobel Prize and be the next Newton or Einstein
link |
or whatever, you just hope that you'll contribute something to humankind's understanding of
link |
how nature works and you'll be satisfied with that.
link |
But here I was in the right place at the right time, a lot of luck, a lot of hard work, and
link |
We discovered something that was really amazing and that was the greatest thrill, right?
link |
I couldn't have asked for anything more than being involved in that discovery.
link |
So the couple of teams, the Supernova Cosmology Project and the HiZ Supernova Search Team,
link |
what was the Nobel Prize given for?
link |
It was given for the discovery of the accelerating expansion of the universe, not for the elucidation
link |
of what dark energy is or what causes that expansion, that acceleration, be it universes
link |
on the outside or whatever, it was only for the observational fact.
link |
So first of all, what is the accelerating universe?
link |
So the accelerating universe is simply that if we look at the galaxies moving away from
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us right now, we would expect them to be moving away more slowly than they were billions of
link |
That's because galaxies have visible matter, which is gravitationally attractive, and dark
link |
matter of an unknown sort that holds galaxies together and holds clusters of galaxies together.
link |
And of course, they then pull on one another and they would tend to retard the expansion
link |
Just as when I toss an apple up, even ignoring air resistance, the mutual gravitational attraction
link |
between Earth and the apple slows the apple down.
link |
If that attraction is great enough, then the apple will someday stop and even come back.
link |
The Big Crunch, you could call it, or the Gnab Gibb, which is Big Bang backwards, right?
link |
That's what could have happened to the universe.
link |
But even if the universe's original expansion energy was so great that it avoids the Big
link |
Crunch, that's like an apple thrown at Earth's escape speed.
link |
It's like the rockets that go to Mars someday, right, with people.
link |
Even then, you'd expect the universe to be slowing down with time.
link |
But we looked back through the history of the universe by looking at progressively more
link |
distant galaxies and by seeing that the evolution of this expansion rate is that in the first
link |
nine billion years, yeah, it was slowing down.
link |
But in the last five billion years, it's been speeding up.
link |
So who asked for that, right, you know?
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I think it's interesting to talk about a little bit of the human story of the Nobel Prize,
link |
which is, I mean, it's fascinating.
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It's a really, first of all, the prize itself.
link |
It's kind of fascinating on the psychological level that prizes, I know we kind of think
link |
that prizes don't matter, but somehow they kind of focus the mind about some of the most
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special things we've accomplished.
link |
It's the recognition, the funding, you know.
link |
And also inspiration for, like I said, when I was a little kid, thinking about the Nobel
link |
Prize, like I didn't, you know, it inspires millions of young scientists.
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At the same time, there's a sadness to it a little bit that, especially in the field,
link |
like depending on the field, but experimental fields that involve teams of, I don't know,
link |
sometimes hundreds of brilliant people, the Nobel Prize is only given to just a handful.
link |
Is it maxed at three?
link |
And it's not even written in Alfred Nobel's will, it turns out.
link |
One of our teammates looked into it in a museum in Stockholm when we went there for Nobel
link |
The leaders who got the prize formally knew that without the rest of us working hard in
link |
the trenches, the result would not have been discovered.
link |
So they invited us to participate in Nobel Week.
link |
And so one of the team members looked in the will and it's not there.
link |
It's just tradition.
link |
That's interesting.
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But it's archaic, you know, that's the way science used to be done.
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It's not the way a lot of science is done now.
link |
And you look at gravitational wave discovery, which was, you know, recognized with the Nobel
link |
Prize in 2017, Ray Weiss at MIT got it and Kip Thorne and Barry Barish at Caltech.
link |
And Ron Drever, one of the masterminds, had passed away earlier in the year.
link |
So again, one of the rules of Nobel is that it's not given posthumously, or at least the
link |
one exception might be if they've made their decision and they're busy making their press
link |
releases right before October, the first week in October or whatever, and then the person
link |
I think they don't change their minds then.
link |
But yeah, you know, it doesn't square with today's reality that a lot of science is done
link |
by big teams, in that case, a team of a thousand people.
link |
In our case, it was two teams consisting of about 50 people.
link |
And we used techniques that were arguably developed in part by people who, astrophysicists
link |
who weren't even on those two papers, I mean, some of them were, but other papers were written
link |
by other people, you know, and so it's like we're standing on the shoulders of giants.
link |
And none of those people was officially recognized.
link |
And to me, it was okay.
link |
You know, again, it was the thrill of doing the work and ultimately the work, the discovery
link |
was recognized with the prize.
link |
And you know, we got to participate in Nobel week and, you know, it's okay with me.
link |
I've known other physicists whose lives were ruined because they did not get the Nobel
link |
prize and they felt strongly that they should have.
link |
Ralph Alpher of the Alpher beta gamma paper predicting the microwave background radiation,
link |
we should have gotten it.
link |
His advisor Gamoff was dead by that point.
link |
But you know, Penzias and Wilson got it for the discovery and an Alpher, apparently from
link |
colleagues who knew him well, I've talked to them.
link |
His life was ruined by this.
link |
He just, it just not at his innards so much.
link |
It's very possible that in a small handful of people, even three, that you would be one
link |
of the Nobel, one of the winners of the Nobel prize.
link |
That doesn't weigh heavy on you.
link |
Well, you know, there were the two team leaders, Saul Perlmutter and Brian Schmidt.
link |
And usually there's the team leaders that are recognized.
link |
And then Adam Rees was my postdoc.
link |
First author, I guess.
link |
I was second author of that paper.
link |
So I was his direct mentor at the time.
link |
Although he was, you know, one of these people who just, you know, runs with things.
link |
He was an MIT undergraduate by the way, Harvard graduate student, and then a postdoc as a
link |
so called Miller fellow for basic research and science at Berkeley, something that I
link |
was back in 84 to 86.
link |
But you're, you know, you're largely a free agent, but he worked quite closely with me
link |
and he came to Berkeley to work with me and on Schmidt's team, he was charged with analyzing
link |
the data and he measured the brightnesses of these distant supernovae showing that they're
link |
fainter and thus more distant than anticipated.
link |
And that led to this conclusion that the universe had to have accelerated in order to push them
link |
out to such great distances.
link |
And I was shocked when he showed me the data, the results of his calculations and measurements.
link |
But it's very, you know, so he deserved it.
link |
And on Sol's team, Gerson Goldhaber deserved it.
link |
But he died, I think a year earlier in 2010, but that would have been four.
link |
And so, and me, well, I was on both teams, but, you know, was I number four, five, six,
link |
It's also very, so if I were to, it's possible that you're, I mean, I can make a very good
link |
case for urine in the three.
link |
And does that, is that psychologically, I mean, listen, it weighs on me a little bit
link |
because I don't know what to do with that.
link |
Perhaps it should motivate the rethinking, like Time magazine started doing like, you
link |
know, person of the year and like they would start doing like concepts and almost like
link |
the black hole gets the Nobel prize or the universe gets the Nobel prize and here's the
link |
So like, or like the Oscar that you could say, because it's a team effort now and it
link |
And the breakthrough prize in fundamental physics, which was started by Yuri Milner
link |
and Zuckerberg is involved in others as well, you know, uh, they recognize the larger team.
link |
Yeah, they, they recognize teams.
link |
And so in fact, both teams in the accelerating universe were recognized with the breakthrough
link |
Nevertheless, the same three people, Reese Perlmutter and Schmidt got the red carpet
link |
rolled out for them and were at the big ceremony and shared half of the prize money.
link |
And the rest of us, roughly 50 shared the other half and didn't get to go to the ceremony.
link |
So, but I, I feel for them, I mean, for the gravitational waves, it was a thousand people.
link |
What are they going to do?
link |
Invite everyone for the Higgs particle.
link |
It was six to 8,000 physicists and engineers.
link |
In fact, because of the whole issue of who gets it experimentally, that discovery still
link |
has not been recognized, right?
link |
The theoretical work by Peter Higgs and, uh, Anglaire got recognized, but there was a troika
link |
of other people who perhaps wrote the most complete paper and they were, they were left
link |
out and, um, another guy died, you know, and
link |
It's all of his heartbreak.
link |
And some people argue that the Nobel prize has been diluted too, because if you look
link |
at Roger Penrose, you can make an argument that he should get the prize by himself.
link |
Like it's just separate those, like he could have and should have, perhaps he should have
link |
perhaps gotten it with Hawking before Hawking's death, right?
link |
The problem was Hawking radiation had not been detected, but you could argue that Hawking
link |
made enough other fundamental contributions to the theoretical study of black holes and
link |
the observed data were already good enough at the time of before Hawking's death.
link |
I mean, the latest results by Reinhard Genzel's group is that they see the time dilation effect
link |
of a star that's passing very close to the black hole in the middle of our galaxy.
link |
That's cool, but, and it adds additional evidence, but hardly anyone doubted the existence of
link |
the supermassive black hole and Andrea Gaz's group, I believe hadn't yet shown that relativistic
link |
effect and yet she got part of the prize as well.
link |
So clearly it was given for the, the original evidence that was really good.
link |
And that evidence is at least a decade old, you know, so one could make the case for,
link |
for Hawking, one could make the case that in 2016, when Mayor and Caloz won the Nobel
link |
Prize for the discovery of the first exoplanet, 51B Pegasi, well, there was a fellow at Penn
link |
State, Alex Wolszczan, who in 1992, three years preceding 1995, found a planet orbiting
link |
a pulsar, a very weird kind of star, a neutron star, and that wouldn't have been a normal
link |
And so the Nobel committee, you know, they gave it for the discovery of planets around
link |
normal sun like stars, but, but hell, you know, Wolszczan found a planet so they could
link |
have given it to him as the third person instead of to Jim Peebles for the development of what's
link |
called physical cosmology.
link |
He's at Princeton, he deserved it, but they could have given Nobel for the development
link |
of physical cosmology to Peebles and I would claim some other people were pretty important
link |
in that development as well.
link |
You know, and they could have given it some other year.
link |
So there's, there's a lot of controversy.
link |
I try not to dwell on it.
link |
Was I number three?
link |
You know, Adam Riess did the work.
link |
You know, I helped bounce ideas off of him, but we wouldn't have had the result without
link |
And I was on both teams for reasons, I mean, you know, I, the style of the first team,
link |
the supernova cosmology project didn't match mine.
link |
They came largely from experimental high energy particle physics, physics where there's these
link |
hierarchical teams and stuff and it's hard for the little guy to have a say, at least
link |
that's what I kind of thought.
link |
Whereas the team of astronomers led by Brian Schmidt was first of all, a bunch of my friends
link |
and they grew up as astronomers making contributions on little teams and we decided to band together,
link |
but all of us had our voices heard.
link |
So it was sort of a culture, a style that I preferred really.
link |
But let me tell you a story at the Nobel banquet, okay?
link |
I'm sitting there between two physicists who are members of the committee of the Swedish
link |
National Academy of Sciences, you know, and I strategically kept, you know, offering them
link |
wine and stuff during this long drawn out Nobel ceremony, right?
link |
And I got them to be pretty talkative and then in a polite diplomatic way, I started
link |
asking them pointed questions and basically they admitted that if there are four or more
link |
people equally deserving, they wait for one of them to die or they just don't give the
link |
prize at all when it's unclear who the three are, at least unclear to them.
link |
But unclear to them, they're not even right part of the time.
link |
I mean, Jocelyn Bell discovered pulsars with a radio antenna, a set of radio antennas that
link |
her advisor Anthony Hewish conceived and built, so he deserves some credit, but he didn't
link |
discover the pulsar.
link |
And his initial reaction to the data that she showed him was a condescending rubbish,
link |
Yeah, I'm not kidding.
link |
Now, I know Jocelyn Bell and she did not let this destroy her life.
link |
She won every other prize under the sun, okay?
link |
Vera Rubin, arguably one of the discoverers of dark matter, although there, if you look
link |
at the history, there were a number of people and that was the issue, I think there were
link |
a number of people, four or more who had similar data and similar ideas at about the same time.
link |
Rubin won every prize under the sun, the new big large scale survey telescope being built
link |
in Chile is being renamed the Vera Rubin Telescope because she passed away in December of 2015,
link |
You know, it'll conduct this survey, large scale survey with the Rubin Telescope.
link |
So she's been recognized, but never with the Nobel Prize.
link |
And I would say that to her credit, she did not let that consume her life either.
link |
And perhaps it was a bit easier because there had been no Nobel given for the discovery
link |
of dark matter, whereas in the case of pulsars and Jocelyn Bell, there was a prize given
link |
for the discovery of the freaking pulsars and she didn't get it.
link |
Well, I mean, what a travesty of justice.
link |
So I also think as a fan of fiction, as a fan of stories that the travesty and the tragedy
link |
and the unfairness and the tension of it is what makes the prize and similar prizes beautiful.
link |
The decisions of other humans that result in dreams being broken and, you know, like
link |
that's why we love the Olympics as so many, you know, people, athletes give their whole
link |
life for this particular moment and then there's referee decisions and like little slips of
link |
here and there, like the little misfortunes that destroy entire dreams.
link |
And that's, it's, it's weird to say, but it feels like that makes the entirety of it even
link |
If it was perfect, it wouldn't be interesting.
link |
Humans like competition and they like heroes and unfortunately it gives the impression
link |
to youngsters today that science is still done by white men with gray beards wearing
link |
And I'm very pleased to see that this year, you know, Andrea Ghez, the fourth woman in
link |
the history of the physics prize to have received it.
link |
And then two women, one at Berkeley, one elsewhere won the Nobel prize in chemistry without any
link |
male co recipient.
link |
And so that's sending a message I think to girls that they can do science and they have
link |
I think the breakthrough prize and other such prizes show that teams get recognized as well.
link |
And if you pay attention to the newspapers, you know, most of the good authors like, you
link |
know, Dennis Overby of the New York Times and others said that these were teams of people
link |
and they, they emphasize that and, you know, they all played a role.
link |
And you know, maybe if some grad student hadn't soldered some circuit, maybe the whole thing
link |
wouldn't have worked, you know.
link |
But still, you know, Ray Weiss and Kip Thorne was the theoretical, you know, impetus for
link |
the whole search for gravitational waves, Barry Barish brought the MIT and Caltech teams
link |
together to get them to cooperate at a time when the project was nearly dead from what
link |
I understand and contributed greatly to the experimental setup as well.
link |
He's a great experimental physicist, but he was really good at bringing these two teams
link |
together instead of having them duke it out in blows and leaving both of them bleeding
link |
You know, the National Science Foundation was going to cut the funding from what I understand,
link |
So, so there's human drama involved in this whole thing.
link |
And the Olympics, yeah, you know, a runner, a swimmer, a runner, runner, you know, they
link |
slip just at the moment that they were taking off from the first thing and that costs them
link |
some fraction of a second and that's it.
link |
They didn't win, you know.
link |
And in that case, I mean, the coaches, the families, which I met a lot of Olympic athletes
link |
and the coaches and the families of the athletes are really the winners of the medals.
link |
But they don't get the medal and it's, you know, credit assignment is a fascinating thing.
link |
I mean, that's the full human story we have.
link |
And outside of prizes, it's fascinating.
link |
I mean, just to be in the middle of it for artificial intelligence, there's a field of
link |
That's really exciting.
link |
And people have been, there's yet another award, the touring awards given for deep learning
link |
to three folks who are very much responsible for the field, but so are a lot of others.
link |
Yeah, that's right.
link |
And there's a few, there's a, there's a fellow by the name of Schmidt Huber who sort of symbolizes
link |
the, the forgotten folks in the deep learning community.
link |
But you know, that's, that's the unfortunate sad thing where you remember, remember Isaac
link |
Newton or remember these, these, these special figures and the ones that flew close to them,
link |
Well, that's right.
link |
And you know, often the breakthroughs are made based on the body of knowledge that had
link |
been assimilated prior to that.
link |
But you know, again, people like to worship heroes.
link |
You mentioned the Oscars earlier and you know, you look at the direct, I mean, well, I mean,
link |
okay, directors and stuff sometimes get awards and stuff, but you know, you look at even
link |
something like, I don't know, songwriters, musicians, Elton John or something, right?
link |
Bernie Taupin, right?
link |
Wrote many of the words or he's not as well known or the Beatles or something like that.
link |
I was heartbroken to learn that Elvis didn't write most of the songs.
link |
But he was the king, right?
link |
And he had such a personality and it was such a performer, right?
link |
But it's the unsung heroes in many cases.
link |
So maybe taking a step back, we talked about the Nobel prize of the accelerating universe,
link |
but your work and the ideas around supernova were important in detecting this accelerating
link |
Can we go to the very basics of what is this beautiful, mysterious object of a supernova?
link |
So a supernova is an exploding star.
link |
Most stars die a relatively quiet death, our own sun, well, despite the fact that it'll
link |
become a red giant and incinerate earth, it'll do that reasonably slowly.
link |
But there's a small minority of stars that end their lives in a Titanic explosion.
link |
And that's not only exciting to watch from afar, but it's critical to our existence because
link |
it is in these explosions that the heavy elements synthesize through nuclear reactions during
link |
the normal course of the star's evolution and during the explosion itself, get injected
link |
into the cosmos, making them available as raw material for new stars, planets, and ultimately
link |
And that's just a great story, the best in some ways.
link |
So we like to study these things and our origins, but it turns out these are incredibly useful
link |
beacons as well, because if you know how powerful an exploding star really is by measuring the
link |
apparent brightness at its peak in galaxies whose distances we already know through having
link |
made other measurements, and you can thus calibrate how powerful the thing really is,
link |
and then you find ones that are much more distant, then you can use their observed brightness
link |
compared with their true intrinsic power or luminosity to judge their distance and hence
link |
the distance of the galaxy in which they're located.
link |
Let me just give this one analogy.
link |
You judge the distance of an oncoming car at night by looking at how bright its headlights
link |
appear to be, and you've calibrated how bright the headlights are of a car that's two or
link |
three meters away of known distance, and you go, oh, that's a faint headlight, and so that's
link |
You also use the apparent angular separation between the two headlights as a consistency
link |
check in your brain, but that's what your brain is doing.
link |
So we can do that for cars, we can do that for stars.
link |
Nice, I like that.
link |
But you know, with cars, the headlights are all, there's some variation, but they're somewhat
link |
similar so you can make those kinds of conclusions.
link |
How much variation is there between supernova that you can detect them?
link |
Right, so first of all, there are several different ways that stars can explode, and
link |
it depends on their mass and whether they're in a binary system and things like that.
link |
And the ones that we used for these cosmological purposes, studying the expansion of the history
link |
of the universe, are the so called type Roman numeral I, lowercase a, type Ia supernovae.
link |
They come from a weird type of a star called a white dwarf.
link |
Our own sun will turn into a white dwarf in about seven billion years.
link |
It'll have about half its present mass compressed into a volume just the size of Earth.
link |
So that's an inordinate density, okay?
link |
It's incredibly dense.
link |
And the matter is what's called by quantum physicists degenerate matter, not because
link |
it's morally reprehensible or anything like that, but this is just the name that quantum
link |
physicists give to electrons that are squeezed into a very tight space.
link |
The electrons take on a motion due to Heisenberg's uncertainty principle, and also due to the
link |
Pauli exclusion principle that electrons don't like to be in the same place, they like to
link |
And those two things mean that a lot of electrons are moving very rapidly, which gives the star
link |
an extra pressure far above the thermal pressure associated with just the random motions of
link |
particles inside the star.
link |
So it's a weird type of star, but normally it wouldn't explode and our sun won't explode,
link |
except that if such a white dwarf is in a pair with another more or less normal star,
link |
it can steal material from that normal star until it gets to an unstable limit, roughly
link |
one and a half times the mass of our sun, 1.4 or so.
link |
This is known as the Chandrasekhar limit after Subramanian Chandrasekhar, an Indian astrophysicist
link |
who figured this out when he was about 20 years old on a voyage from India to England
link |
where he was to be educated.
link |
And then he did this and then 50 years later he won the Nobel Prize in physics in 1984
link |
largely for this work that he did as a youngster who was on his way to be educated.
link |
And his advisor, the great Arthur Eddington in England, who had done a lot of great things
link |
and was a great astrophysicist, nevertheless, he too was human and had his faults.
link |
He ridiculed Chandra's scientific work at a conference in England and most of us, if
link |
we had been Chandra, would have just given up astrophysics at that time when the great
link |
Arthur Eddington ridicules our work.
link |
That's another inspirational story for the youngster.
link |
But anyway, no matter what your advisor says or don't always pay attention to your advisor.
link |
Don't lose hope if you really think you're onto something.
link |
That doesn't mean never listen to your advisor.
link |
They may have sage advice as well.
link |
But anyway, when a white dwarf grows to a certain mass, it becomes unstable.
link |
And one of the ways it can end its life is to go through a thermonuclear runaway.
link |
So basically, the carbon nuclei inside the white dwarf start fusing together to form
link |
And the energy that those fusion reactions emit doesn't go into being dissipated out
link |
of the star or expanding it the way if you take a blowtorch to the middle of the Sun,
link |
you heat up its gases, the gases would expand and cool.
link |
But this degenerate star can't expand and cool.
link |
And so the energy pumped in through these fusion reactions goes into making the nuclei
link |
And that gets more of them sufficiently close together that they can undergo nuclear fusion,
link |
thereby releasing more energy that goes into speeding up more nuclei.
link |
And thus you have a runaway, a bomb, an uncontrolled fusion reactor instead of the controlled fusion,
link |
which is what our Sun does.
link |
Our Sun is a marvelous controlled fusion reactor.
link |
This is what we need here on Earth, fusion energy to solve our energy crisis, right?
link |
But the Sun holds the stuff in through gravity and you need a big mass to do that.
link |
So this uncontrolled fusion reaction blows up a star that's pretty much the same in
link |
And you measure it to be almost the same in all cases.
link |
But the devil is in the details, and in fact, we observe them to not be all the same.
link |
And theoretically, they might not be all the same because the rate of the fusion reactions
link |
might depend on the amount of trace heavier elements in the white dwarf.
link |
And that could depend on how old it is, whether it was born billions of years ago when there
link |
weren't many heavier elements or whether it's a relatively young white dwarf and all
link |
kinds of other things.
link |
And part of my work was to show that indeed, not all the Type Ia's are the same.
link |
You have to be careful when you use them.
link |
You have to calibrate them.
link |
They're not standard candles the way it just, if all headlights or all candles were the
link |
same lumens or whatever, you'd say they're standard and then it would be relative.
link |
Standard candles is an awesome term, okay.
link |
Standard candles is what astronomers like to say, but I don't like that term because
link |
there aren't any standard candles, but there are standardizable candles.
link |
And by looking at these type Ia's, you look at enough of them in nearby galaxies whose
link |
distances you know independently.
link |
And what you can tell is that, you know, this is something that a colleague of mine, Mark
link |
Phillips did who was on Schmidt's team and arguably was one of the people who deserved
link |
He showed that the intrinsically more powerful Type Ia's decline in brightness, and it turns
link |
out rise in brightness as well, more slowly than the less luminous Ia's.
link |
And so if you calibrate this by measuring a whole bunch of nearby ones and then you
link |
look at a distant one, instead of saying, well, it's a 100 watt Type Ia supernova, they're
link |
much more powerful than that by the way, plus or minus 50, you can say, no, it's a hundred
link |
and 12 plus or minus 15, or it's 84 plus or minus 17.
link |
It tells you where it is in the power scale and it greatly decreases the uncertainties.
link |
And that's what makes these things cosmologically useful.
link |
I showed that if you spread the light out into a spectrum, you can tell spectroscopically
link |
that these things are different as well.
link |
And in 1991, I happened to study two of the extreme peculiar ones, the low luminosity
link |
ones and the high luminosity ones, 1991BG and 1991T.
link |
This showed that not all the Ia's are the same.
link |
And indeed, at the time of 1991, I was a little bit skeptical that we could use Type Ia's
link |
because of this diversity that I was observing.
link |
But in 1993, Mark Phillips wrote a paper that showed this correlation between the light
link |
curve, the brightness versus time and the peak luminosity.
link |
Which gives you enough information to calibrate.
link |
Then they become calibratable and that was a game changer.
link |
How many Type Ia's are out there to use for data?
link |
Now there are thousands of them, but at the time, the high Z team had 16 and the supernova
link |
cosmology project had 40.
link |
But the 16 were better measured than the 40.
link |
And so our statistical uncertainties were comparable if you look at the two papers that
link |
How does that make you feel that there's these gigantic explosions just sprinkled out there?
link |
Well, I certainly don't want one to be very nearby and it would have to be within something
link |
like 10 light years to be an existential threat.
link |
So they can happen in our galaxy?
link |
So they would be okay?
link |
In most cases we'd be okay because our galaxy is 100,000 light years across.
link |
And you'd need one of these things to be within about 10 light years to be an existential
link |
And it gives birth to a bunch of other stars, I guess?
link |
Yeah, it gives birth to expanding gases that are chemically enriched and those expanding
link |
gases mixed with other chemically enriched expanding gases or primordial clouds of hydrogen
link |
I mean, this is in a sense the greatest story ever told, right?
link |
I teach this introductory astronomy course at Berkeley and I tell them there's only five
link |
or six things that I want them to really understand and remember and I'm going to come to their
link |
deathbed and I'm going to ask them about this and if they get it wrong, I will retroactively
link |
fail and their whole career will have been shot.
link |
That's a student's worst nightmare.
link |
If they don't know and observe a total solar eclipse and yet they had the opportunity to
link |
do so, I will retroactively fail them.
link |
But one of them is, where did we come from?
link |
Where did the elements in our DNA come from?
link |
The carbon in our cells, the oxygen that we breathe, the calcium in our bones, the iron
link |
in our red blood cells.
link |
Those elements, the phosphorus in our DNA, they all came from stars, from nuclear reactions
link |
in stars and they were ejected into the cosmos and in some cases, like iron, made during
link |
the explosions and those gases drifted out, mixed with other clouds, made a new star or
link |
a star cluster, some of whose members then evolved and exploded, thus enriching the gases
link |
in the galaxy progressively more with time until finally, four and a half billion years
link |
ago from one of these chemically enriched clouds, our solar system formed with a rocky
link |
earthlike planet and somewhere, somehow, these self replicating, evolving molecules, bacteria
link |
formed and evolved through paramecia and amoebas and slugs and apes and us.
link |
And here we are, sentient beings that can ask these questions about our very origins
link |
and with our intellect and with the machines we make, come to a reasonable understanding
link |
What a beautiful story.
link |
I mean, if that does not put you at least in awe, if not in love with science and its
link |
power of deduction, I don't know what will, right?
link |
It's one of the greatest stories, if not the greatest story.
link |
Obviously, that's personality dependent and all that, it's a subjective opinion, but it's
link |
perhaps the greatest story ever told.
link |
I mean, you could link it to the Big Bang and go even farther, right, to make an even
link |
more complete story, but as a subset, that's even in some ways a greater story than even
link |
the existence of the universe in some ways, because you could just imagine some really
link |
boring universe that never leads to sentient creatures such as ourselves.
link |
And is a supernova usually the introduction to that story?
link |
So are they usually the thing that launches the, is there other engines of creation?
link |
Well, the supernova is the one, I mean, I touch upon the subject earlier in my course,
link |
in fact, right about now in my lectures, because I talk about how our sun right now is fusing
link |
hydrogen to form helium nuclei and later it'll form carbon and oxygen nuclei, but that's
link |
where the process will stop for our sun, it's not massive enough, some stars that are more
link |
massive can go somewhat beyond that.
link |
So that's the beginning of this idea of the birth of the heavy elements, since they couldn't
link |
have been born at the time of the Big Bang, conditions of temperature and pressure weren't
link |
sufficient to make any significant quantities of the heavier elements.
link |
And so that's the beginning, but then you need some of these stars to explode, right?
link |
Because if those heavy elements remained forever trapped in the cores of stars, then they would
link |
not be available for the production of new stars, planets, and ultimately life.
link |
So indeed the supernova, my main area of interest, plays a leading role in this whole story.
link |
I saw that you got a chance to call Richard Feynman a mentor of yours when you were at
link |
Do you have any fond memories of Feynman, any lessons that stick with you?
link |
Oh yeah, he was quite a character and one of the deepest thinkers of all time probably,
link |
and at least in my life, the physicist who had the single most intuitive understanding
link |
of how nature works of anyone I've met.
link |
I learned a number of things from him, he was not my thesis advisor, I worked with Wallace
link |
Sargent at Caltech on what are called active galaxies, big black holes in the centers of
link |
galaxies that are accreting or swallowing material, a little bit like the stuff of this
link |
year's Nobel Prize in Physics 2020.
link |
But Feynman I had for two courses, one was general theory of relativity at the graduate
link |
level and one was applications of quantum physics to all kinds of interesting things.
link |
And he had this very intuitive way of looking at things that he tried to bring to his students
link |
and he felt that if you can't explain something in a reasonably simple way to a non scientist
link |
or at least someone who is versed a little bit with science but is not a professional
link |
scientist then you probably don't understand it very well yourself very thoroughly.
link |
So that in me made a desire to be able to explain science to the general public and
link |
I've often found that in explaining things, yeah, there's a certain part that I didn't
link |
really understand myself, that's one reason I like to teach the introductory courses to
link |
the lay public is that I sometimes find that my explanations are lacking in my own mind.
link |
So he did that for me.
link |
Is there a, if I could just pause for a second, you said he had one of the most intuitive
link |
understanding of nature.
link |
What if you could break apart what intuitive means, like is that on the philosophical level?
link |
No, sort of physical.
link |
How do you draw a mental picture or a picture on paper of what's going on?
link |
And he's perhaps most famous in this regard for his Feynman diagrams, which in what's
link |
called quantum electrodynamics, a quantum field theory of electricity and magnetism.
link |
What you have are actually an exchange of photons between charged particles and they
link |
might even be virtual photons if the particles are at rest relative to one another.
link |
And there are ways of doing calculations that are brute force that take pages on pages and
link |
pages of calculations.
link |
And Julian Schwinger developed some of the mathematics for that and won the Nobel prize
link |
But Feynman had these diagrams that he made and he had a set of rules of what to do at
link |
You'd have two particles coming together and then a particle going out and then two particles
link |
And he'd have these rules associated when there were vertices and when there were particles
link |
splitting off from one another and all that.
link |
And it looked a little bit like a bunch of a hodgepodge at first.
link |
But to those who learned the rules and understood them, they saw that you could do these complex
link |
calculations in a much simpler way.
link |
And indeed, in some ways, Freeman Dyson had an even better knack for explaining really
link |
what quantum electrodynamics actually was.
link |
But I didn't know Freeman Dyson.
link |
Maybe he did have a more intuitive view of the world than Feynman did.
link |
But of the people I knew, Feynman was the most intuitive, most sort of, is there a picture?
link |
Is there a simple way you can understand this?
link |
In the path that a particle follows even, you can get the classical path, at least for
link |
a baseball or something like that, by using quantum physics if you want.
link |
But in a sense, the baseball sniffs out all possible paths.
link |
It goes out to the Andromeda galaxy and then goes to the batter.
link |
But the probability of doing that is very, very small because tiny little paths next
link |
door to any given path cancel out that path.
link |
And the ones that all add together, they're the ones that are more likely to be followed.
link |
And this actually ties in with Fermat's principle of least action and there are ideas in optics
link |
that go into this as well and just sort of beautifully brings everything together.
link |
But the particle sniffs out all possible paths.
link |
What a crazy idea.
link |
But if you do the mathematics associated with that, it ends up being actually useful, a
link |
useful way of looking at the world.
link |
So you're also, I mean, you're widely acknowledged as, I mean, outside of your science work as
link |
being one of the greatest educators in the world.
link |
And Feynman is famous for being that.
link |
Is there something about being a teacher that you...
link |
Well, it's very, very rewarding when you have students who are really into it.
link |
You know, going back to Feynman, at Caltech, I was taking these graduate courses and there
link |
were two of us, myself and Jeff Richmond, who's now a professor of physics at University
link |
of California, Santa Barbara, who asked lots of questions.
link |
And a lot of the Caltech students are nervous about asking questions.
link |
They want to save face.
link |
They seem to think that if they ask a question, their peers might think it's a stupid question.
link |
Well, I didn't really care what people thought and Jeff Richmond didn't either.
link |
We asked all these questions and in fact, in many cases, they were quite good questions
link |
and Feynman said, well, the rest of you should be having questions like this.
link |
And I remember one time in particular when he said to the rest of the class, why is it
link |
Aren't the rest of you curious about what I'm saying?
link |
Do you really understand it all that well?
link |
If so, why aren't you asking the next most logical question?
link |
No, you guys are too scared to ask these questions that these two are asking.
link |
So he actually invited us to lunch a couple of times where just the three of us sat and
link |
had lunch with one of the greatest thinkers of 20th century physics.
link |
And so, yeah, he rubbed off on me and, you know, you encourage questions as well, encourage
link |
questions, you know, and yeah, you know, definitely, I mean, you know, I encourage questions.
link |
I like it when students ask questions.
link |
I tell them that they shouldn't feel shy about asking a question.
link |
Probably half the students in the class would have that same question if they even understood
link |
the material enough to ask that question.
link |
Curiosity is the first step of seeing the beauty of something.
link |
So yeah, and the question is the ultimate form of curiosity.
link |
Let me ask, what is the meaning of life?
link |
The meaning of life, you know, from a cosmologist's perspective or from a human perspective, personal,
link |
you know, life is what you make of it, really, right?
link |
It's each of us has to have our own meaning and it doesn't have to be.
link |
Well, I think that in many cases, meaning is to some degree associated with goals.
link |
You set some goals or expectations for yourself, things you want to accomplish, things you
link |
want to do, things you want to experience, and to the degree that you experience those
link |
and do those things, it can give you meaning.
link |
You don't have to change the world the way Newton or Michelangelo or da Vinci did.
link |
I mean, people often say, you changed the world, but look, come on, there's seven and
link |
a half, close to eight billion of us now.
link |
Most of us are not going to change the world and does that mean that most of us are leading
link |
No, it just has to be something that gives you meaning, that gives you satisfaction,
link |
that gives you a good feeling about what you did.
link |
And often, based on human nature, which can be very good and also very bad, but often
link |
it's the things that help others that give us meaning and a feeling of satisfaction.
link |
You taught someone to read, you cared for someone who was terminally ill, you brought
link |
up a nice family, you brought up your kids, you did a good job, you put your heart and
link |
soul into it, you read a lot of books if that's what you wanted to do, had a lot of perspectives
link |
on life, you traveled the world if that's what you wanted to do.
link |
But if some of these things are not within reach, you're in a socioeconomic position
link |
where you can't travel the world or whatever, you find other forms of meaning.
link |
It doesn't have to be some profound, I'm going to change the world, I'm going to be
link |
the one who everyone remembers type thing, right?
link |
In the context of the greatest story ever told, like the fact that we came from stars
link |
and now we're two apes asking about the meaning of life, how does that fit together?
link |
How does that make any sense?
link |
It does, it does, and this is sort of what I was referring to, that it's a beautiful
link |
universe that allows us to come into creation, right?
link |
It's a way that the universe found of knowing, of understanding itself, because I don't
link |
think that inanimate rocks and stars and black holes and things have any real capability
link |
of abstract thoughts and of learning about the rest of the universe or even their origins.
link |
I mean, they're just a pile of atoms that has no conscience, has no ability to think,
link |
has no ability to explore, and we do.
link |
And I'm not saying we're the epitome of all life forever, but at least for life on Earth
link |
so far the evidence suggests that we are the epitome in terms of the richness of our thoughts,
link |
the degree to which we can explore the universe, do experiments, build machines, understand
link |
And I just hope that we use science for good, not evil, and that we don't end up destroying
link |
I mean, the whales and dolphins are plenty intelligent.
link |
They don't ask abstract questions, they don't read books, but on the other hand, they're
link |
not in any danger of destroying themselves and everything else as well.
link |
And so maybe that's a better form of intelligence, but at least in terms of our ability to explore
link |
and make use of our minds, I mean, to me, it's this.
link |
It's this that gives me the potential for meaning, right?
link |
The fact that I can understand and explore.
link |
It's kind of fascinating to think that the universe created us and eventually we've built
link |
telescopes to look back at it, to look back at its origins and to wonder how the heck
link |
It needn't have been that way, right?
link |
And this is one of the, you know, the multiverse sort of things.
link |
You know, you can alter the laws of physics or even the constants of nature, seemingly
link |
inconsequential things like the mass ratio of the proton and the neutron, you know, wake
link |
me up when it's over, right?
link |
What could be more boring?
link |
But it turns out you play with things a little bit like the ratio of the mass of the neutron
link |
to the proton and you generally get boring universes, only hydrogen or only helium or
link |
You can't even get the rich periodic table, let alone bacteria, paramecia, slugs and humans,
link |
I'm not even anthropocentrizing this to the degree that I could.
link |
Even a rich periodic table wouldn't be possible if certain constants weren't this way, but
link |
And that to me leads to the idea of a multiverse that, you know, the dice were thrown many,
link |
many times and there's this cosmic archipelago where most of the universes are boring and
link |
some might be more interesting.
link |
But we are in the rare breed that's really quite darn interesting.
link |
And if there were only one and maybe there is only one, well then that's truly amazing.
link |
But I actually think there are lots and lots, just like there are lots of planets.
link |
Earth isn't special for any particular reason.
link |
There are lots of planets in our solar system and especially around other stars.
link |
And occasionally there are going to be ones that are conducive to the development of complexity
link |
culminating in life as we know it.
link |
And that's a beautiful story.
link |
I don't think there's a better way to end it.
link |
Alex, it's a huge honor.
link |
One of my favorite conversations I've had in this podcast.
link |
Well, thank you so much for talking to us.
link |
For the honor of having been asked to do this.
link |
Thanks for listening to this conversation with Alex Filipenko, and thank you to our
link |
Neuro, the maker of functional sugar free gum and mints that I use to give my brain
link |
a quick caffeine boost.
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BetterHelp, online therapy with a licensed professional.
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If you enjoy this thing, subscribe on YouTube, review it with 5 Stars and Apple Podcast,
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follow on Spotify, support on Patreon, or connect with me on Twitter at Lex Friedman.
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And now, let me leave you with some words from Carl Sagan.
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The nitrogen in our DNA, the calcium in our teeth, the iron in our blood, the carbon in
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our apple pies, were made in the interiors of collapsing stars.
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We are made of star stuff.
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Thank you for listening, and hope to see you next time.