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Everything ever seen — every star, mountain, and face — makes up less than 5 percent of the universe. Astrophysicist Janna Levin reminds us that the rest — dark matter and dark energy — is invisible, mysterious, and everywhere. We are the luminous exception in a universe of darkness.
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Applause
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It's such a pleasure to be here tonight
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I wonder how many of you reflected on this phenomenon, which is that everything anyone has ever seen or ever will see
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makes up less than 5% of what is out there in the universe
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All the people, all the faces, all the mountains, the moon, the stars, the galaxies, supernova, all of it
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Anything we've ever seen, less than 5%. The rest is in a form of dark matter and dark energy as yet unknown
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And the dark phrasing, the terminology is a misnomer. The dark energy is in this room right now
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It fills the room. The dark matter is coursing through you right now
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It's not dark. They're not dark. They're invisible. And I wonder, I know people have thought about this
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and maybe you've wondered yourself, what is all this dark stuff? What is it? Where does it come from
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What is it? Or maybe you study astrophysics and you actually build detectors deep in minds
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and you wait patiently for years for one dark matter particle to strike your detector than decades
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Despite its abundance, the dark matter has never revealed itself. Now, it could be that it never will
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that we'll never be able to identify exactly what it is. But maybe you've also reflected on this strange disparity
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between us and this dark universe. Or maybe you've never heard of it before
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I don't know, maybe this is your first time. But imagine us as a collection of confetti that's
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tossed amongst this impassive void, sparkling, because we are luminous. And yet to the dark
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matter, we are as invisible to the dark sector as a dark sector is to us. So if you consider
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the visible universe, you can see your hand because the atoms in your body scatter light
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and your eyes absorb that light and that light triggers an electrical impulse
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along nerve endings and that ignites in your mind an image, this qualia of the visual world
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And you can feel your fingertips because atoms interact and you can smell and you can taste
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because of chemical interactions. And your heartbeat is in fact regulated by electrical impulses
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from specialized cells. And this is the world This is the world that we know. This is the visual world
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It's electrical, it's magnetic, it's the world of atoms and of light
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But it's not just our microcosm. This is the same material that burns in stars
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The same light that shines from stars. It the same matter that lingering from the Big Bang That is everything that everyone has ever seen and ever will see But if we spiral out to the large scale then we in the domain of the
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dark matter and the dark energy. The astronomer Edwin Hubble, working not that far from here
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at Mount Wilson Observatory at what was the largest telescope at the time, made this remarkable
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discovery, he realized that this collection of stars, this spiral Milky Way, which is what we
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call our own galaxy, was not the only one. He was the first person in the 1920s to observe another
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galaxy. Tremendous observation. When Einstein was working, he did not know there were other galaxies
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out there. And as Hubble is looking at these other galaxies that he's discovered, these collections
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of hundreds of billions of stars, he observes that the space between the galaxies is stretching
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It's just an incredible observation. The space between the galaxies is stretching. This was
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predicted as a consequence of the Big Bang. Now it was thought the universe would come out of the
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Big Bang, space stretching in all directions. There's no galaxies yet. It's the early universe
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and over the course of time, galaxies would form, the world would unfold in the way that we've seen it
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but this expansion would have to slow down. It would ebb. Now, many years after Hubble
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the famed satellite, Hubble Space Telescope, named in his honor, observed that the universe abounds with galaxies
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There's not just a splattering of galaxies in our little neighborhood. there are as many galaxies in the observable universe as there are stars in our own Milky Way
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That's hundreds of billions. And then there were other observations that pushed even further
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and realized that this expansion between the galaxies isn't slowing. In fact, it seems to be getting ever faster
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as though something was driving the universe on to continue to expand
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Now, astronomers retrofitting the data tried to take the measure of this invisible source
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that seemed to have this peculiar pressure on space-time driving it to expand ever faster
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And the best that they could ascertain was that there was an unknown, unidentified, unseen form of energy implicated
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and yet no specific culprit could be identified. identified. And so it was dubbed enigmatically the dark energy. And this energy permeates all
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of space. We don't know what it is. It might literally be the energy of empty space. We don't
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know. But we do know that that dark energy doesn't shine. And it doesn't interact directly. Atoms
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course through it unimpeded and oblivious Now the dark matter behaves differently It collects on these unseen these invisible filaments and in the early universe it creates these kinds of seeds these depressions and wells into which ordinary matter collects
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forming galaxies and clusters of galaxies. And the dark matter pools on these vast and translucent halos
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that surround these galaxies, yet unseen. And the dark matter also doesn't shine
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and even clustered together right around galaxies, it does not collide with atoms
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The atoms stream through it, and the dark matter through the atoms
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Again, totally unimpeded, and again, oblivious, essentially. Now, these dark components are extremely significant
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in the story of our history because on these vast cosmological scales
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they dominate the evolution and structure of the universe across billions of light years
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And the luminous universe that we see with all of our instruments
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all of our detectors, with the naked eye when we walk out at night
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in a rare, dark, not foggy, not polluted evening, what we're seeing is the luminous universe
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suspended from this unseen architecture. Now spiraling back in, you are submerged in a static ocean of dark energy
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And there are rainstorms of dark matter in every room you occupy
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At the moment, millions of dark matter particles are coursing through you at hundreds or even thousands of kilometers per second
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Our entire solar system moves together and orbits around the Milky Way
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There's a supermassive black hole at the center of our galaxy. We very, very slowly orbit it
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And as we orbit this supermassive black hole in this vast galaxy
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we are streaming ourselves through this dark matter halo. We tend to be going in the direction of the constellation Cygnus
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if that's of interest to you when you look up at night. You will see the dark matter
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Well, we don't technically see it. The dark matter streams through us as we move through this dark halo
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And we don't know how complicated that dark sector is. We don't know if there are dark forces, entire dark laws of physics
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Maybe there are dark stars and dark planets. Maybe there's dark creatures
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We don't know how complicated this dark sector is. There could be a dark creature occupying the same space as you, like a shadow, haunting you or you him
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Although that last part is really just completely science fiction. That's completely unsure. But you get the idea
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We don't know how complicated or how simple it is. It could have eddies and turbulences
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There could be a storm around us. If we could turn on some ability to see the dark matter
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we might be seeing a tornado or a storm that is happening around us
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of which we are unaware. Now, regardless, we simply factually have to accept
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that we are not everything. And we not even much And with that astronomical perspective comes a shift And I know some people will express a sense of dread or you know existential terror that comes with these kinds of realizations dizzying
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realizations for me it gives me a great sense of being part of a grander story of connecting all
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the way back to the big bang and and at least for a moment having a sense of quieting the thoughts
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and understanding some perspective on our obsessiveness over our everyday concerns, at least for a moment
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So let's enjoy the humility of the astronomical perspective for a second. Now, we can soak that in
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This reminds me, a lot of people like to indulge in the sense of our inconsequentiality
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in the sense of our insignificance, especially when taking an astronomical view
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There's a great cartoon from the New Yorker of a guy standing on the edge of the world
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and there's a view like this behind him, and his companion is running to take his photo
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and he says, make sure you can see how insignificant I am. I love that cartoon
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So I want you to imagine as you are soaking up your insignificance
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when you are considering yourself against the stage of the known world
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with its trillions of galaxies and its trillions of stars, to imagine the next time you admire a starry sky
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that that saturated abyss in the background is most everything. And for just a moment, I feel we need a Rumi quote
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To save us from this moment, I have an aphorism from the great 13th century Persian poet Rumi
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he said, you are not a drop in the ocean, you are the entire ocean in a drop
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It's a beautiful quote, and I think it's very appropriate here. You are the glowing, luminous exception in a universe of darkness
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You are an arrangement of agnostic atoms forged in stars that can only act and react exactly as prescribed
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Yet, you contain multitudes. You are the history of the collisions in the universe
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the explosions from stars that threw matter back out into the universe
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to form into the planets and your body. You are evidence of the entire universe grinding into being
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You hold in your hand a fistful of the ocean of dark energy
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streams of storms of dark matter. You are a droplet, precipitated from the 5% of that gooey
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residue left over from the Big Bang. And you're briefly aware and you're briefly illuminated
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So you are not a drop in the ocean, you are the entire ocean in a drop. Thank you
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