How dark matter and dark energy shape the cosmos | Janna Levin

0:10 It's such a pleasure to be here tonight.

0:12 I wonder how many of you reflected on this phenomenon,

0:18 which is that everything anyone has ever seen or ever will see

0:25 makes up less than 5% of what is out there in the universe.

0:29 All the people, all the faces, all the mountains, the moon, the stars,

0:34 the galaxies, supernova, all of it, anything we've ever seen, less than 5%.

0:40 The rest is in a form of dark matter and dark energy as yet unknown.

0:45 And the dark phrasing, the terminology is a misnomer.

0:49 The dark energy is in this room right now.

0:53 It fills the room.

0:55 The dark matter is coursing through you right now.

1:00 It's not dark.

1:01 They're not dark, they're invisible.

1:05 And I wonder, I know people have

1:06 thought about this and maybe you've wondered yourself,

1:08 what is all this dark stuff?

1:10 What does it, where does it come from?

1:12 What is it?

1:12 Or, or maybe you study astrophysics

1:14 and you actually build detectors deep in minds,

1:19 and you wait patiently for years for one

1:23 dark matter particle to strike your detector,

1:27 then decades, despite its abundance, the dark matter has never revealed itself.

1:35 Now, it could be that it never will,

1:41 that we'll never be able to identify exactly what it is.

1:45 But maybe you've also reflected on this strange

1:48 disparity between us and this dark universe.

1:51 Or maybe you've never heard of it before.

1:53 I don't know, maybe this is your first time, but imagine us as a collection

1:59 of confetti that's tossed amongst this impassive void.

2:03 Sparkling.

2:03 Because we are luminous and yet to the dark matter,

2:08 we are as invisible to the dark sector as a dark sector is to us.

2:14 So if you consider the visible universe, you can see your hand because the atoms

2:19 in your body scatter light and your eyes absorb that light,

2:23 and that light triggers an electrical impulse along nerve endings.

2:27 And, and that ignites in your mind an image this quaia of the visual world.

2:32 And you can feel your fingertips be because atoms interact

2:36 and, and you can smell and you can taste because of chemical interactions.

2:42 And your heartbeat is in fact

2:45 regulated by electrical impulses from specialized cells.

2:50 And this is the world, right?

2:52 This is the world that we know.

2:54 This is the visual world.

2:55 It's electrical, it's magnetic, it's the world of atoms and of light.

3:01 But it's not just our microcosm.

3:04 This is the same material that burns in stars,

3:08 the same light that shines from stars.

3:11 It's the same matter that's lingering from the big bang.

3:15 That is everything that everyone has ever seen and ever will see.

3:22 But if we spiral out to the large scale,

3:26 then we're in the domain of the dark matter and the dark energy.

3:30 The astronomer, Edwin Hubble,

3:32 working not that far from here at Mount Wilson Observatory,

3:35 at what was the largest telescope at the time, made this remarkable discovery.

3:40 He realized that this collection of stars, this spiral, Milky Way,

3:45 which is what we call our own galaxy, was not the only one.

3:50 He was the first person in the 1920s to observe another galaxy.

3:55 Tremendous observation.

3:57 When Einstein was working, he did not know there were other galaxies out there.

4:01 And as Hubble is looking at these other galaxies that he's discovered,

4:05 these collections of hundreds of billions of stars,

4:08 he observes that the space between the galaxies is stretching.

4:14 It's just an incredible observation.

4:16 The space between the galaxies is stretching.

4:20 This was predicted as a consequence of the Big Bang.

4:25 Now, it was thought the universe would come out

4:27 of the Big Bang space stretching in all directions.

4:30 There's no galaxies yet.

4:32 It's the early universe.

4:33 And over the course of time,

4:35 galaxies would form the world would unfold in the way that we've seen it.

4:38 But this expansion would have to slow down.

4:41 It would ebb.

4:42 Now, many years after Hubble, the famed satellite, Hubble space telescope,

4:49 named in his honor, observed that the universe abounds with galaxies.

4:56 There's not just a splattering of galaxies in our little neighborhood.

4:59 There are as many galaxies in the observable universe

5:04 as there are stars in our own milky way.

5:07 That's hundreds of billions.

5:11 And then there were other observations that pushed even further

5:14 and realized that this expansion between the galaxies isn't slowing.

5:19 In fact, it seems to be getting ever faster as though

5:24 something was driving the universe on to continue to expand.

5:29 Now, astronomers retrofitting the data,

5:32 tried to take the measure of this invisible source that seemed to have

5:37 this peculiar pressure on space time driving it to expand ever faster.

5:42 And the best that they could ascertain was that there was an unknown,

5:47 unidentified unseen form of energy implicated,

5:52 and yet no specific culprit could be identified.

5:56 And so it was dubbed enigmatically the dark energy.

6:01 And this energy permeates all of space.

6:04 We don't know what it is.

6:05 It might literally be the energy of empty space.

6:11 We don't know.

6:12 But we do know that that dark

6:14 energy doesn't shine and it doesn't interact directly.

6:18 Adams cos through it unimpeded and oblivious.

6:23 Now, the dark matter behaves differently.

6:27 It, it collects on these unseen, these invisible filaments.

6:31 And in the early universe, it creates these kinds of seeds,

6:35 these these depressions and and wells into which

6:39 ordinary matter collects forming galaxies and clusters of galaxies

6:45 and the dark matter pools on these vast

6:48 and translucent halos that surround these galaxies yet unseen.

6:54 And the dark matter also doesn't shine

6:56 and even clustered together right around galaxies.

7:00 It does not collide with atoms.

7:02 The atoms stream through it and the dark matter through the atoms,

7:06 again, totally unimpeded and again, oblivious essentially.

7:13 Now these star components are extremely significant in the story of our history.

7:19 Because on these vast cosmological scales,

7:22 they dominate the evolution and structure

7:24 of the universe across billions of light years.

7:29 And the luminous universe that we see with all of our instruments,

7:33 all of our detectors with the naked eye.

7:35 When we walk out at night in a rare dark, not foggy, not polluted evening,

7:41 what we're seeing is the luminous

7:46 universe suspended from this unseen architecture.

7:52 Now spiraling back in, you are submersed in a static ocean of dark energy.

8:00 And there are rainstorms of dark matter in every room you occupy.

8:04 At the moment, millions of dark matter particles are coursing

8:08 through you at hundreds or even thousands of kilometers per second.

8:12 Our entire solar system moves together and orbits around the Milky Way.

8:18 There's a super massive black hole at the center of our galaxy.

8:20 We very, very slowly orbit it.

8:22 And as we orbit this super massive black hole in this vast galaxy,

8:27 we are streaming ourselves through this dark matter halo.

8:31 We tend to be going in the direction of the constellation sickness.

8:35 If that's of interest to you.

8:36 When you look up at night, you will see the dark matter.

8:38 Well, we don't technically see it.

8:40 The dark matter streams through us as we move through this dark halo.

8:45 And we don't know how complicated that dark sector is.

8:50 We don't know if there are dark forces, entire dark laws of physics.

8:54 Maybe there are dark stars and dark planets and maybe there's dark creatures.

9:00 We don't know how complicated this dark sector is.

9:03 There could be a dark creature occupying the same space as you,

9:07 like a shadow haunting you or you him,

9:11 although that last part is really just completely science fiction.

9:13 That's completely unfair.

9:14 But you get the idea.

9:15 We don't know how complicated or how simple it is.

9:19 It could have eddies and turbulences.

9:21 There could be a storm around us.

9:22 If we could turn on some ability to see the dark matter,

9:25 we might be seeing a tornado or a storm that is happening around us,

9:31 that, that that of which we are unaware.

9:34 Now regardless, we simply factually have to accept

9:40 that we are not everything and we're not even much.

9:45 And with that astronomical perspective comes a shift.

9:49 And I know some people will express a, a sense of dread or you know,

9:54 a existential terror that comes with these kinds of realizations,

9:58 dizzying realizations.

9:59 For me, it gives me a great sense of being part

10:03 of a grander story of connecting all the way back to the Big bang.

10:07 And, and at least for a moment,

10:10 having a sense of quieting the thoughts and, and understanding

10:15 some perspective on our obsessiveness over our everyday concerns,

10:20 at least for a moment.

10:22 So let's enjoy the humility of the astronomical perspective for a second.

10:26 Now we can soak that in there.

10:29 This reminds me, a lot of people like

10:33 to indulge in the sense of our inconsequentially.

10:37 You know, in the sense of our insignificance,

10:40 especially when taking an astronomical view.

10:42 There's a great cartoon from the New Yorker of a guy standing

10:46 on the edge of the world and there's a view like this behind him.

10:49 And his companion is running to take his photo and he says,

10:53 make sure you can see how insignificant I am.

10:57 I love that cartoon.

10:59 So I want you to imagine as you are soaking up your insignificance,

11:04 when you are considering yourself against the stage of the known world,

11:08 with its trillions of galaxies and its trillions of stars,

11:12 to imagine the next time you admire a starry sky,

11:15 that that saturated abyss in the background is most everything.

11:22 And for just a moment, I feel we need a Rumi quote to save us.

11:33 From this moment, I have an aphorism

11:36 from the great 13th century Persian poet Rumi.

11:40 He said, you are not a drop in the ocean.

11:43 You are the entire ocean in a drop.

11:48 It's a beautiful quote, and I think it's very appropriate.

11:52 Here you are the glowing, luminous exception in a universe of darkness.

12:00 You are an arrangement of agnostic atoms,

12:04 forged and stars that can only act and react exactly as prescribed.

12:10 Yet you contain multitudes.

12:13 You are the history of the collisions in the universe,

12:17 the the explosions from stars that threw matter back out

12:21 into the universe to form into the planets and your body.

12:26 You are evidence of the entire universe grinding into being.

12:32 You hold in your hand a fistful of the ocean,

12:36 of dark energy streams, of storms of dark matter.

12:41 You are a droplet precipitated from the 5%

12:45 of that gooey residue left over from the Big Bang.

12:49 And you're briefly aware and you're briefly illuminated.

12:53 So you are not a drop in the ocean.

12:55 You are the entire ocean in a drop.

12:58 Thank you.