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Could quantum clocks detect dark matter? · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Daniel, if you were dark Matter, where would you hide?
• 0:12
  Speaker 2: I wouldn't hide. If I was dark matter, I would
• 0:14
  Speaker 2: totally parade myself in front of all the scientists in
• 0:17
  Speaker 2: the galaxy.
• 0:18
  Speaker 1: Ooh, a parade. You mean like a pageant.
• 0:20
  Speaker 2: Queen, Yeah, something like that. You know, just don't be
• 0:24
  Speaker 2: so shy.
• 0:26
  Speaker 1: Well, if it turns out you are dark matter, we'll
• 0:28
  Speaker 1: definitely throw you a parade. But so far, it seems
• 0:31
  Speaker 1: like dark matter is kind of reclusive, right, It's kind
• 0:33
  Speaker 1: of shy, So maybe it is hiding. What would be
• 0:36
  Speaker 1: some good spots for it to hide it?
• 0:38
  Speaker 2: Well, if dark matter doesn't want a tiara and it's
• 0:41
  Speaker 2: hiding somewhere, then I don't know where it would hide.
• 0:43
  Speaker 2: I mean, if I knew, I would go and look
• 0:45
  Speaker 2: for it there.
• 0:46
  Speaker 1: What if it's somewhere kind of.
• 0:47
  Speaker 2: Obvious, like what like right behind me?
• 0:50
  Speaker 1: Yeah, or right in front of you, or right on
• 0:53
  Speaker 1: TV and the Matter universe contest, that.
• 0:56
  Speaker 2: Would be a great twist ending for the m Knight
• 0:58
  Speaker 2: Shamanlan version of this story.
• 1:01
  Speaker 1: Well, man, do you think he knows I see dark Matter?
• 1:19
  Speaker 3: Hi?
• 1:20
  Speaker 1: I'm Jorge Mack, cartoonists and the author of Ollor's Great
• 1:22
  Speaker 1: Big Universe.
• 1:23
  Speaker 4: Hi.
• 1:23
  Speaker 2: I'm Daniel. I'm a particle physicist, and I wish I
• 1:26
  Speaker 2: had a dark matter Tiara.
• 1:28
  Speaker 1: Oh, but it wouldn't be very shiny or bright. It
• 1:30
  Speaker 1: would be dark, So what's the point. Also, when it
• 1:33
  Speaker 1: had just fall through your head, it.
• 1:36
  Speaker 2: Would be hard to wear, but it'd be like the greatest,
• 1:39
  Speaker 2: most amazing piece of jewelry.
• 1:41
  Speaker 1: Ever, how would you even keep it in your house?
• 1:46
  Speaker 2: These are just like engineering details, you know. Once I've
• 1:48
  Speaker 2: solved the physics of a dark matter Tiara, I'll just
• 1:51
  Speaker 2: pass that off to the engineers.
• 1:52
  Speaker 1: This is just all part of your dream to be
• 1:54
  Speaker 1: the universe's doctor Universe.
• 1:59
  Speaker 2: I would like a little bit of bling. Yeah, you know,
• 2:01
  Speaker 2: physics blining would be nice. I'm not going to win
• 2:03
  Speaker 2: a Nobel Prize anytime soon, So dark matter Tira sounds good.
• 2:06
  Speaker 1: I see. I see. You could just say you have
• 2:08
  Speaker 1: a dark matter Tierra, and they nobody would be able
• 2:11
  Speaker 1: to see it, or feel it or detect it. They
• 2:14
  Speaker 1: would just have to believe you.
• 2:15
  Speaker 2: I need evidence, man, That's what science is all about.
• 2:18
  Speaker 2: You got to have data.
• 2:20
  Speaker 1: I don't think those beauty contests depend on data very much.
• 2:22
  Speaker 2: But I'm trying to win a science contest.
• 2:24
  Speaker 1: But anyway's welcome. Dark podcast Daniel and Jorge Explain the Universe,
• 2:28
  Speaker 1: a production of iHeartRadio in which.
• 2:30
  Speaker 2: We enter you in the greatest science contest of all time,
• 2:34
  Speaker 2: the quest to understand the nature of the universe. What
• 2:38
  Speaker 2: is it, what's in it, what's it made out of?
• 2:41
  Speaker 2: How does it all work. We think these questions are
• 2:43
  Speaker 2: deep and fundamental parts of being a human being in
• 2:46
  Speaker 2: this cosmos, and unraveling these questions is a joy that
• 2:50
  Speaker 2: everybody should share. So on this podcast we take those
• 2:54
  Speaker 2: questions apart and try to share our answers and our
• 2:56
  Speaker 2: ignorance with you.
• 2:58
  Speaker 1: That's right, because science is the greatest beauty contest in
• 3:01
  Speaker 1: the universe, where the goal is to discover the beauty
• 3:03
  Speaker 1: of how this universe is put together, how it works,
• 3:06
  Speaker 1: and what is our place in it.
• 3:07
  Speaker 2: Over the last fifty one hundred years, we've developed a
• 3:09
  Speaker 2: pretty good sense for what's in the universe. We know
• 3:12
  Speaker 2: about stars and galaxies and all the bright and shiny
• 3:16
  Speaker 2: stuff that's out there in the universe, and we've also
• 3:19
  Speaker 2: figured out that there's a lot of the universe that
• 3:21
  Speaker 2: we can't see directly using our senses or any of
• 3:24
  Speaker 2: the forces that we've discovered except for gravity. We know
• 3:28
  Speaker 2: that a huge chunk of the stuff that's out there
• 3:31
  Speaker 2: in the universe is invisible. It's intangible, which makes it
• 3:35
  Speaker 2: very hard to discover and to figure out how to
• 3:38
  Speaker 2: make it into a tiara.
• 3:39
  Speaker 1: Yeah, because it turns out that a pretty good understanding
• 3:41
  Speaker 1: of the universe only covers about uh five percent of
• 3:45
  Speaker 1: what we know is out there. The rest, the ninety
• 3:47
  Speaker 1: five percent of the universe that we know is there,
• 3:49
  Speaker 1: we have no idea what it is or how it works.
• 3:54
  Speaker 2: That sounds like a good title for a book.
• 3:56
  Speaker 1: Yeah, I think we rode One Daniel, which is available
• 3:59
  Speaker 1: for a sale everywhere.
• 4:00
  Speaker 2: That's right. The kind of stuff that you and I
• 4:03
  Speaker 2: are made out of, atoms specifically, or what physicists called baryons,
• 4:08
  Speaker 2: only makes up five percent of the energy budget in
• 4:11
  Speaker 2: the universe. There's another twenty five twenty seven percent that's
• 4:15
  Speaker 2: dark matter, some kind of stuff that we know is matter.
• 4:18
  Speaker 2: We know it's out there, but we don't know what
• 4:21
  Speaker 2: it is, and we only have a very rough sense
• 4:23
  Speaker 2: of even where it is around us. The rest of
• 4:26
  Speaker 2: the universe is something we call dark energy, which is
• 4:28
  Speaker 2: contributing to the accelerating expansion of the universe and we
• 4:31
  Speaker 2: have even less clue about what makes that up.
• 4:35
  Speaker 1: Yeah, there's a lot we don't know, and it seems
• 4:37
  Speaker 1: like these are maybe the defining mysteries of our times
• 4:41
  Speaker 1: is to figure out what the universe is actually made
• 4:44
  Speaker 1: out of, given that what we're made out of counts
• 4:47
  Speaker 1: is so little of it.
• 4:48
  Speaker 2: Yeah, you're right. And in the last few decades there's
• 4:50
  Speaker 2: been a huge program of people looking for dark matter.
• 4:54
  Speaker 2: We've talked on the podcast about trying to make dark
• 4:57
  Speaker 2: matter in the laboratory by smashing particles together. We're searching
• 5:00
  Speaker 2: for the dark matter wind. We might be floating through
• 5:03
  Speaker 2: with very sensitive underground facilities looking for an individual piece
• 5:07
  Speaker 2: of dark matter to bump into liquid xenon, for example,
• 5:11
  Speaker 2: or maybe evidence of dark matter annihilating itself in the
• 5:14
  Speaker 2: center of the galaxy. But so far, none of these
• 5:16
  Speaker 2: experiments have found dark matter, which means we've got to
• 5:19
  Speaker 2: get creative about other ways to maybe detect this most
• 5:23
  Speaker 2: important or at least most common kind of matter in
• 5:26
  Speaker 2: the universe.
• 5:27
  Speaker 1: So to be on the podcast, we'll be tackling the
• 5:29
  Speaker 1: question could quantum clocks detect dark matter and how many
• 5:40
  Speaker 1: jargon words can we fit into one podcast title.
• 5:44
  Speaker 2: I know it does sound like buzzword sound, you know, like,
• 5:48
  Speaker 2: could we use AI generated crypto bitcoin to detect dark matter?
• 5:52
  Speaker 1: You mean quantum nanomtter Yes, exactly, quantum nanomtter tierras.
• 5:58
  Speaker 2: Wow, I like quantum nano matter. I go use that
• 6:00
  Speaker 2: in a proposal.
• 6:01
  Speaker 1: That's good, I said it first, I said at first, Daniel. Also,
• 6:05
  Speaker 1: it's probably already on sale on Amazon. There's probably some
• 6:08
  Speaker 1: product out there with that name.
• 6:09
  Speaker 2: So yeah, but you didn't say ching tm after it,
• 6:13
  Speaker 2: so I can use it.
• 6:14
  Speaker 1: No, you don't have to.
• 6:15
  Speaker 2: What I gotta brush up on my podcast property law.
• 6:19
  Speaker 1: Yeah, you better or else I'm gonna see you for
• 6:22
  Speaker 1: nano dollars for nano bitcoins, you know what?
• 6:26
  Speaker 2: Or hey, you can have all of my nano bitcoins.
• 6:31
  Speaker 1: What's the price of bitcoins these days?
• 6:33
  Speaker 2: Nano bitcoins zero? Yeah, doesn't exist.
• 6:37
  Speaker 1: But anyways, it's kind of an intriguing title. Could quantum
• 6:40
  Speaker 1: clocks detect dark matter? And quantum clocks sounds like it
• 6:44
  Speaker 1: does sound like something you could buy an off of Amazon.
• 6:47
  Speaker 1: Did you check to see if it's something you can
• 6:49
  Speaker 1: just get next day?
• 6:50
  Speaker 3: Oh?
• 6:51
  Speaker 2: Yeah, it turns out Amazon will sell you something. It
• 6:53
  Speaker 2: calls a quantum clock, like a quantum entanglement led wall clock,
• 6:59
  Speaker 2: but none of these things are actually quantum clocks the
• 7:02
  Speaker 2: way that we understand them.
• 7:04
  Speaker 1: Well, technically, isn't everything a quantum something? Well, I mean
• 7:08
  Speaker 1: not everything, but you know, the five percent that we
• 7:09
  Speaker 1: know about in the universe is in it all quantum technically,
• 7:14
  Speaker 1: like this is a quantum podcast.
• 7:17
  Speaker 2: I mean, that's a really interesting philosophical question and not
• 7:20
  Speaker 2: one that we really have an answer to, because on
• 7:22
  Speaker 2: one hand, you're right that everything is made out of
• 7:24
  Speaker 2: quantum particle, so isn't the whole universe quantum? On the
• 7:27
  Speaker 2: other hand, we know that when you zoom out things
• 7:30
  Speaker 2: behave by different rules. We call that classical. We don't
• 7:32
  Speaker 2: really understand why there is that transition, but there definitely
• 7:35
  Speaker 2: is a transition. So to call everything quantum is either
• 7:39
  Speaker 2: to say that look classical is just big zoomed out quantum,
• 7:43
  Speaker 2: or is to say that clackical doesn't really matter, which
• 7:45
  Speaker 2: doesn't really sit well with me. Or what if I
• 7:47
  Speaker 2: have no class, then you probably have a lot of
• 7:51
  Speaker 2: big coin.
• 7:53
  Speaker 1: Then I'm not going to win any beauty contest. I
• 7:56
  Speaker 1: have poise, but just no class.
• 7:58
  Speaker 2: Yeah, exactly, But you know, for example, a clock that
• 8:02
  Speaker 2: just works on mechanical parts would also work in the
• 8:05
  Speaker 2: universe where quantum mechanics didn't rule the microscopic because it's
• 8:08
  Speaker 2: not sensitive to those microscopic details, and so that wouldn't
• 8:12
  Speaker 2: be a quantum clock, for example, like a pendulum clock
• 8:15
  Speaker 2: or an old fashioned Swiss gear based clock.
• 8:18
  Speaker 1: A discussion about new mankla Sure that's my favorite.
• 8:22
  Speaker 2: Hey, you brought it up, But.
• 8:23
  Speaker 1: Anyways, it's a kind of an interesting question and so
• 8:25
  Speaker 1: we'll dig into it. But as usually, we were wondering
• 8:28
  Speaker 1: how many people out there had thought about putting the
• 8:30
  Speaker 1: concepts of dark matter and quantum and clocks all together
• 8:34
  Speaker 1: in one sentence.
• 8:35
  Speaker 2: So thanks very much to everybody who participates in this
• 8:38
  Speaker 2: segment of the podcast. We love that you volunteer, We
• 8:40
  Speaker 2: love hearing your thoughts, and we love sharing your voice
• 8:43
  Speaker 2: with all of the other listeners. Please chime in if
• 8:47
  Speaker 2: you'd like, writeing me two questions at Danielanjorge dot com
• 8:50
  Speaker 2: and you can't participate.
• 8:51
  Speaker 1: So think about it for a second. Do you think
• 8:54
  Speaker 1: quantum clocks can use to detect dark matter? Here's what
• 8:58
  Speaker 1: people had to say.
• 9:00
  Speaker 4: I've heard of a quantum clock, but I'm not sure
• 9:02
  Speaker 4: how it would be able to detect dark matter anymore
• 9:04
  Speaker 4: than a regular clock could. I guess maybe even with
• 9:08
  Speaker 4: a regular clock, you could send it out into space,
• 9:10
  Speaker 4: and if it hits a huge clump of dark matter
• 9:12
  Speaker 4: and therefore gravity, maybe we could learn that there's a
• 9:15
  Speaker 4: big well of gravity out in some location that we
• 9:18
  Speaker 4: otherwise couldn't detect.
• 9:20
  Speaker 1: So sure, I suppose it's possible, but I have no
• 9:22
  Speaker 1: clue how it would Maybe something to do with entanglement.
• 9:26
  Speaker 3: Since you're asking, the answer is probably yes, but maybe
• 9:29
  Speaker 3: still theoretical. I would think you'd have to use the
• 9:33
  Speaker 3: idea of measuring light passing through an area of more
• 9:37
  Speaker 3: density that's possibly dark matter that causes curvature of space
• 9:42
  Speaker 3: and also time dilation. How to do that, I'm not sure.
• 9:46
  Speaker 2: Since we don't possess a quantum clock, it doesn't seem
• 9:49
  Speaker 2: unreasonable to suggest that a non existent clock cannot detect
• 9:52
  Speaker 2: dark matter.
• 9:53
  Speaker 1: All right, it's pretty uh intense answers here. I feel
• 9:57
  Speaker 1: like it's something that some of the listeners have I
• 10:00
  Speaker 1: heard about before. Did you pull your professor colleagues this time?
• 10:05
  Speaker 2: No, these are our listeners online. You know there's some
• 10:08
  Speaker 2: good answers here about entanglement and light passing through areas
• 10:14
  Speaker 2: with dark matter density in them, and just in general
• 10:16
  Speaker 2: sense that this is a hard problem.
• 10:18
  Speaker 1: Maybe you should ask a bunch of beauty queens next
• 10:21
  Speaker 1: time we're making one of the standard questions in a
• 10:23
  Speaker 1: beauty pageant. Forget howdy, how would you save the world
• 10:27
  Speaker 1: or how would you know make things better? What do
• 10:30
  Speaker 1: you think about quantum plock?
• 10:33
  Speaker 2: Well, where is the dark matter? Yeah, I'd love to
• 10:35
  Speaker 2: hear that answer in the beauty pageant.
• 10:38
  Speaker 1: Not that it couldn't happen, of course, no, absolutely. All right, Well,
• 10:41
  Speaker 1: let's dig into this intriguing question of whether dark matter
• 10:45
  Speaker 1: can be detected by quantum clocks, and let's start with
• 10:48
  Speaker 1: the basics, Daniel, what do we know about dark matter?
• 10:51
  Speaker 2: So there's a lot that we do and do not
• 10:53
  Speaker 2: know about dark matter. So let's start with what we
• 10:57
  Speaker 2: do know. We know that it's out there, and we
• 10:59
  Speaker 2: know that it's here as well. We know that dark
• 11:02
  Speaker 2: matter is something that exists in the universe. And then
• 11:05
  Speaker 2: it's matter. We know that because we see its gravity.
• 11:08
  Speaker 2: We see it holding galaxies together as they spin. There
• 11:11
  Speaker 2: isn't enough gravity from the stars and the gas and
• 11:14
  Speaker 2: dust that make up those galaxies to keep the stars
• 11:17
  Speaker 2: in place as they swirl around the center of the
• 11:19
  Speaker 2: galaxy at very high speeds, and yet they do stay
• 11:23
  Speaker 2: in place. Galaxies are mostly not throwing stars out into
• 11:27
  Speaker 2: intergalactic space, and so we infer that there must be
• 11:29
  Speaker 2: some matter there to hold that galaxy together. But it's
• 11:33
  Speaker 2: more than just that one inference, that one fudge factor
• 11:36
  Speaker 2: to make that particular equation work. We see evidence for
• 11:39
  Speaker 2: dark matter all over the history of the universe, from
• 11:42
  Speaker 2: the very first few moments when the early universe plasma
• 11:45
  Speaker 2: is slashing around and you have dark matter and normal
• 11:48
  Speaker 2: matter and photons all acting very differently and creating different
• 11:52
  Speaker 2: slashing patterns. From looking at that slashing in the cosmic
• 11:56
  Speaker 2: microwave background radiation, we can figure out that there was
• 11:59
  Speaker 2: dark matter, even measure how much of it there is,
• 12:02
  Speaker 2: and we can trace the history of dark matter's gravity
• 12:04
  Speaker 2: as it shapes the structure formation of the whole universe.
• 12:07
  Speaker 2: Why we have galaxies at all this early in the
• 12:10
  Speaker 2: history of the universe, and so dark matter is definitely
• 12:13
  Speaker 2: out there as a kind of matter, but we don't
• 12:15
  Speaker 2: know really what it is or very specifically where it
• 12:18
  Speaker 2: is because it's so hard to see since it only
• 12:22
  Speaker 2: feels gravity. It doesn't feel any of the other forces
• 12:24
  Speaker 2: that we've discovered.
• 12:26
  Speaker 1: And we can also sort of see dark matter right like,
• 12:28
  Speaker 1: we can see it in the same way that you
• 12:30
  Speaker 1: can see a lens or glass lens or example. You
• 12:32
  Speaker 1: can see how it distorts the light behind it.
• 12:35
  Speaker 2: Right, Yeah, exactly, we can see dark matter through gravity,
• 12:38
  Speaker 2: and so that means we can see stuff bending around
• 12:41
  Speaker 2: dark matter. We can see it holding galaxies together, and
• 12:44
  Speaker 2: that even impacts how light moves in the vicinity of
• 12:47
  Speaker 2: dark matter. If you have a big blob of dark
• 12:50
  Speaker 2: matter between you and some distant galaxy, for example, the
• 12:53
  Speaker 2: photons from that distant galaxy will bend as they move
• 12:56
  Speaker 2: through that dark matter, creating apparent distortions in your image.
• 13:00
  Speaker 2: You can even sometimes see the same galaxy twice in
• 13:03
  Speaker 2: the sky because of this gravitational lensing, and so we
• 13:07
  Speaker 2: know that it's out there, and we can use some
• 13:08
  Speaker 2: techniques like that to sometimes tell roughly where it is.
• 13:12
  Speaker 2: But because dark matter is so weak it's particles only
• 13:15
  Speaker 2: feel gravity, we think it's very difficult to figure out
• 13:18
  Speaker 2: what exactly is made out of To isolate one piece
• 13:21
  Speaker 2: of dark matter, because gravity is so weak that essentially
• 13:25
  Speaker 2: a particle's gravity is almost impossible to measure.
• 13:28
  Speaker 1: Yeah, and dark matter is also something that's not just
• 13:31
  Speaker 1: out there in space. It's sort of like all around us,
• 13:34
  Speaker 1: right like it's floating through us right now, sort of
• 13:36
  Speaker 1: like the fourth you know, it flows through us, binds
• 13:39
  Speaker 1: us all together. It's made out of meti chlorians.
• 13:42
  Speaker 2: Perhaps, perhaps, yeah, exactly, you'll only really understand it after
• 13:47
  Speaker 2: nine hundred years of study. That's a really good question,
• 13:49
  Speaker 2: and that's sort of the central question of this episode
• 13:52
  Speaker 2: is exactly where is the dark matter and can we
• 13:56
  Speaker 2: find like concentrations of it? Can we map it out?
• 14:00
  Speaker 2: Because dark matter is so weakly interacting like only gravity,
• 14:03
  Speaker 2: it takes huge amounts of it to feel anything, and
• 14:06
  Speaker 2: so that makes it very hard to tell exactly where
• 14:09
  Speaker 2: the dark matter is. It might be that it's mostly
• 14:11
  Speaker 2: spread out evenly through the galaxy. It might be more
• 14:14
  Speaker 2: clumpy than that depends a lot on your particular theory
• 14:17
  Speaker 2: of dark matter. Where it exactly is. So it could
• 14:21
  Speaker 2: be that we are in a dark matter wind as
• 14:23
  Speaker 2: the Earth orbits the Sun and the Sun moves through
• 14:25
  Speaker 2: the galaxy. We could also be in a dark matter
• 14:28
  Speaker 2: Liss bubble, a bubble of space in which there's comparatively
• 14:31
  Speaker 2: little dark matter, or it could be that dark matter
• 14:34
  Speaker 2: is fairly dense in our area.
• 14:36
  Speaker 1: You know, I have to say every time you say
• 14:37
  Speaker 1: dark matter wind, it makes me think of dark.
• 14:40
  Speaker 2: Part elevating the discourse every week.
• 14:48
  Speaker 1: That's my job. That's why I'm here. Smells all grounded
• 14:51
  Speaker 1: or grounded or you know, flat as in fletch winds.
• 14:56
  Speaker 1: But anyways, so it's sort of all around this, and
• 14:58
  Speaker 1: I guess I'm wondering, like, if it is all around us,
• 15:00
  Speaker 1: would we be able to tell, Like, you know, if
• 15:03
  Speaker 1: let's say dark matter is floating through the Earth right now,
• 15:06
  Speaker 1: or let's say it wasn't, would you be able to
• 15:07
  Speaker 1: tell the difference.
• 15:08
  Speaker 2: That's exactly what these experiments are trying to measure. And
• 15:11
  Speaker 2: to give you a sense of the difficulty the challenge
• 15:14
  Speaker 2: of this, think about like why we didn't discover dark
• 15:17
  Speaker 2: matter earlier. Just in studying how our Solar system moves.
• 15:21
  Speaker 2: We have now very precise measurements of the orbit of
• 15:24
  Speaker 2: Jupiter and Mars and all the planets and all the
• 15:27
  Speaker 2: little pieces of the Solar System as they orbit the Sun.
• 15:30
  Speaker 2: You might think, hey, if dark matter is here in
• 15:32
  Speaker 2: our Solar system and it has gravity, wouldn't it change
• 15:35
  Speaker 2: the way those things orbit? Shouldn't we be able to
• 15:37
  Speaker 2: detect it? But because we think dark matter might be
• 15:40
  Speaker 2: spread very thin, probably there isn't that much dark matter
• 15:44
  Speaker 2: in the vicinity of our solar system. So even those
• 15:46
  Speaker 2: very very precise measurements, you know, like knowing the motion
• 15:50
  Speaker 2: of Jupiter to meters or centimeters, can't detect dark matter
• 15:54
  Speaker 2: because it would be very thin and very spread out,
• 15:56
  Speaker 2: and mostly we think homogeneous, which in the end doesn't
• 15:59
  Speaker 2: give much much gravitational pull on the objects in the
• 16:02
  Speaker 2: solar system. So it takes a very specialized, highly sensitive
• 16:05
  Speaker 2: device to be able to detect this dark matter.
• 16:08
  Speaker 1: Yeah, and then don't we say once like, if you
• 16:10
  Speaker 1: take all the dark matter that is potentially floating through
• 16:13
  Speaker 1: the Earth right now, it would only weigh about as
• 16:15
  Speaker 1: much as a squirrel or something like that.
• 16:18
  Speaker 2: Yeah, exactly, though that's very speculative, right. That assumes that
• 16:21
  Speaker 2: dark matter is essentially equally spread out in our galaxy,
• 16:24
  Speaker 2: which we don't believe is true. But if you assume
• 16:27
  Speaker 2: that there is, then we know our galaxy, for example,
• 16:31
  Speaker 2: is ninety five percent dark matter. That means for every
• 16:35
  Speaker 2: kilogram of matter made out of atoms like hydrogen and
• 16:38
  Speaker 2: helium or whatever, there's nineteen kilograms of matter made out
• 16:41
  Speaker 2: of whatever dark matter is made out of, And so
• 16:44
  Speaker 2: it's like nineteen to one in our galaxy.
• 16:47
  Speaker 1: Which sounds like a lot, but I guess also galaxies
• 16:50
  Speaker 1: kind of very empty mostly, right, Like it's probably like
• 16:53
  Speaker 1: ninety nine percent empty.
• 16:55
  Speaker 2: Yeah, exactly. Now, normal matter clumps up a lot, right
• 16:58
  Speaker 2: like the Sun is an extraord ordinarily dense collection of
• 17:01
  Speaker 2: normal matter. Normal matter is not spread evenly through the galaxy.
• 17:05
  Speaker 2: But if you take dark matter and spread it evenly
• 17:07
  Speaker 2: through the galaxy, you get a pretty small density. It's
• 17:11
  Speaker 2: like ten to the twenty six kilograms per cubic light year,
• 17:15
  Speaker 2: which is a huge volume, which means it's like ten
• 17:18
  Speaker 2: to the negative twenty two kilograms per cubic meter. So
• 17:22
  Speaker 2: then if you add up all the cubic meters in
• 17:24
  Speaker 2: the Earth, that adds up to about two thirds of
• 17:27
  Speaker 2: a kilogram of dark matter inside the volume of the Earth. Again,
• 17:30
  Speaker 2: assuming that dark matter is evenly spread throughout the galaxy,
• 17:34
  Speaker 2: which it probably isn't, but it might be.
• 17:36
  Speaker 1: Roughly, which is about the size or mass of a squirrel.
• 17:40
  Speaker 2: Yeah, exactly, so one squirrel of dark matter inside the
• 17:43
  Speaker 2: volume of the Earth compared to you know, the many,
• 17:45
  Speaker 2: many millions and billions of kilograms of normal matter inside
• 17:48
  Speaker 2: the volume of the Earth. That sounds the importance of clumping, right,
• 17:51
  Speaker 2: Because normal matter clumps together, its gravity is much more
• 17:54
  Speaker 2: powerful in our local neighborhood than dark matter. Even though
• 17:58
  Speaker 2: dark matter outweighs normal matter by nineteen to one, if
• 18:01
  Speaker 2: it's much more thinly spread out, the local effects of
• 18:04
  Speaker 2: its gravity are much harder to detect.
• 18:06
  Speaker 1: I think maybe what you're saying is that dark matter,
• 18:09
  Speaker 1: in terms of the universe scale, it mostly hangs out
• 18:12
  Speaker 1: in galaxies. Like you don't see a lot of dark
• 18:14
  Speaker 1: matter floating out there on its own between galaxies.
• 18:17
  Speaker 2: Yeah, we can do really precise measurements of where dark
• 18:19
  Speaker 2: matter is on the galaxy scale, because galaxies are really
• 18:21
  Speaker 2: really big. If you can tell how galaxies are orbiting
• 18:24
  Speaker 2: around each other, just the way we can tell how
• 18:26
  Speaker 2: stars are moving through the galaxy, so enormous clumps of
• 18:30
  Speaker 2: dark matter, absolutely we can measure their gravity. But when
• 18:33
  Speaker 2: you zoom in in a really fine grained way and
• 18:35
  Speaker 2: want to say, hey, is there a moon sized blob
• 18:37
  Speaker 2: of dark matter anywhere in our solar system. That's a
• 18:40
  Speaker 2: tough question to answer.
• 18:41
  Speaker 1: So then within the galaxy, you're saying, like, there's a
• 18:44
  Speaker 1: lot of dark matter within our galaxy. Ninety five percent
• 18:46
  Speaker 1: of the mass of our galaxy is dark matter. And
• 18:48
  Speaker 1: what does it look like. Does it look like, you know,
• 18:50
  Speaker 1: an intense, dense ball of dark matter in the middle.
• 18:54
  Speaker 1: Is it evenly distributed? And also like our galaxy looks
• 18:57
  Speaker 1: like a disc, sort of like a flat disk. Is
• 18:59
  Speaker 1: dark matter also shaped like a flat disk?
• 19:01
  Speaker 2: So we have the best answers the more we zoom out,
• 19:03
  Speaker 2: and then as we zoom in, things get literally fuzzy.
• 19:06
  Speaker 2: But on the scale of the galaxy, we have some ideas.
• 19:09
  Speaker 2: We think that dark matter is like a big halo.
• 19:11
  Speaker 2: So imagine the visible galaxy right at the edge of
• 19:14
  Speaker 2: the stars. Dark matter is a big halo that goes
• 19:17
  Speaker 2: out beyond the visible stars, and it's bigger and fuzzier.
• 19:21
  Speaker 2: It hasn't collapsed the way normal matter has because it
• 19:23
  Speaker 2: just doesn't clump right. In order to clump, things need
• 19:26
  Speaker 2: other kinds of interaction other than gravity. Like if you
• 19:29
  Speaker 2: have two dark matter particles, they attract each other gravitationally
• 19:32
  Speaker 2: and then just pass right through each other. They're just
• 19:34
  Speaker 2: gonna zig and zag back and forth, oscillate forever. They're
• 19:37
  Speaker 2: not going to clump together. To do that. You need
• 19:38
  Speaker 2: like electromagnetism or the strong force or something that wants
• 19:42
  Speaker 2: to grab onto each other. So dark matter stays a
• 19:44
  Speaker 2: big puffy halo, and the galaxy is sort of embedded
• 19:48
  Speaker 2: in that halo. And that's not a coincidence. Right. The
• 19:51
  Speaker 2: reason the galaxy exists is because of a big dark
• 19:54
  Speaker 2: matter blob there that's gathered together all the hydrogen helium
• 19:58
  Speaker 2: gravitationally and may it into a galaxy. It's the reason
• 20:01
  Speaker 2: we have stars, et cetera.
• 20:03
  Speaker 1: Now, when you say like halo, you don't actually mean
• 20:06
  Speaker 1: like an angel's halo that looks like a ring. You
• 20:08
  Speaker 1: actually mean just like a blob, right.
• 20:10
  Speaker 2: Yeah, exactly, like a big fuzzy blob that extends out
• 20:13
  Speaker 2: further along the disc and then further above and below
• 20:16
  Speaker 2: the disc. But even that we know already is not
• 20:19
  Speaker 2: evenly distributed.
• 20:20
  Speaker 1: Is it like football shaped? Is it you? Is it
• 20:22
  Speaker 1: kind of flat or is it a perfect sphere?
• 20:24
  Speaker 2: It's more like a hockey puck, right, It's flat, but
• 20:27
  Speaker 2: not as flat as the galaxy. Itself.
• 20:29
  Speaker 1: What made it flat?
• 20:30
  Speaker 2: Yeah, maybe a hockey puck is the wrong analogy. It's
• 20:32
  Speaker 2: not quite that flat. It's more like a big ellipsoid.
• 20:35
  Speaker 1: You mean like a slightly squished ball.
• 20:37
  Speaker 2: Yeah, exactly, It's like a big basketball that somebody's sitting
• 20:42
  Speaker 2: on or something.
• 20:42
  Speaker 1: All right, Well, let's get a little bit more into
• 20:45
  Speaker 1: the details of what we know about dark matter. How
• 20:47
  Speaker 1: much of it can we see? How much can we
• 20:49
  Speaker 1: discern about what it's doing in our universe? And we'll
• 20:54
  Speaker 1: answer the question of whether you can use a quantum
• 20:56
  Speaker 1: clock from Amazon dot com to detect it. So we'll
• 21:00
  Speaker 1: get to those questions, but first's take at a quick break.
• 21:16
  Speaker 1: All right, we're asking the question can you use quantum
• 21:18
  Speaker 1: clocks to detect dark matter? And we've been recapping a
• 21:22
  Speaker 1: little bit about what we know about dark matter, Daniel.
• 21:25
  Speaker 1: How much of the details of it can we see?
• 21:27
  Speaker 2: Not really very much. We have this sense of a big,
• 21:31
  Speaker 2: fuzzy halo that surrounds the galaxy, and we can also
• 21:36
  Speaker 2: measure the density as a function of distance from the center.
• 21:39
  Speaker 2: So if you're a star, for example, orbiting the center
• 21:41
  Speaker 2: of the galaxy, the speed at which you orbit depends
• 21:45
  Speaker 2: on the force that's holding you in that orbit. So
• 21:48
  Speaker 2: the stronger the force, the faster you can go, or
• 21:51
  Speaker 2: the faster you can go, the stronger the force that's
• 21:53
  Speaker 2: needed to hold you in that orbit. So by measuring
• 21:56
  Speaker 2: the speed of a given star, we can essentially measure
• 21:59
  Speaker 2: the mass of all all that stuff that's holding on
• 22:01
  Speaker 2: to that star. So then if you look at stars
• 22:03
  Speaker 2: at different distances from the center, you can basically map
• 22:07
  Speaker 2: out the density of stuff in the galaxy as you
• 22:10
  Speaker 2: go further and closer to the center of the galaxy.
• 22:13
  Speaker 1: Like if dark matter was super condensed in the middle
• 22:16
  Speaker 1: of the galaxy, then the stars in the galaxy would
• 22:19
  Speaker 1: be rotating a certain way. Or if the dark matter
• 22:22
  Speaker 1: was more spread out, then the stars in the galaxy
• 22:25
  Speaker 1: would be rotating in a different way.
• 22:27
  Speaker 2: Yeah, exactly, if all the dark matter in the galaxy
• 22:29
  Speaker 2: was at the center, then everything would act in a
• 22:32
  Speaker 2: certain way, would just go like one over are squared.
• 22:34
  Speaker 2: It's sort of like the way the Solar system orbits
• 22:36
  Speaker 2: the Sun. But if you take some of that mass
• 22:38
  Speaker 2: and you spread it out through the galaxy instead, then
• 22:40
  Speaker 2: the dark matter that's further out than a given star
• 22:43
  Speaker 2: doesn't affect its orbit because its gravity all cancels out,
• 22:46
  Speaker 2: so that changes the rotation speed of those stars. And
• 22:49
  Speaker 2: that's in fact how we first discover dark matter was
• 22:52
  Speaker 2: by looking at these rotation speeds of stars around the
• 22:55
  Speaker 2: center of the galaxy and seeing that we couldn't explain
• 22:58
  Speaker 2: it by mapping all the mass from the stars and
• 23:00
  Speaker 2: the gas and the dust. And that's exactly how you
• 23:02
  Speaker 2: can tell where you need to add more mass to
• 23:05
  Speaker 2: explain these rotation speeds. It's not just like, hey, add
• 23:08
  Speaker 2: a big blob at the center. You need to add
• 23:09
  Speaker 2: some of the center and also some further out and
• 23:12
  Speaker 2: some further out, and so precise measurements of those velocities
• 23:15
  Speaker 2: give you a fairly accurate picture of where the dark
• 23:18
  Speaker 2: matter is in the galaxy. And it's not evenly spread out.
• 23:21
  Speaker 2: It's more densely clumped at the center, which is something you'd.
• 23:24
  Speaker 1: Expect because it is affected by gravity, right, It.
• 23:27
  Speaker 2: Is, in the end affected by gravity, and so it's
• 23:29
  Speaker 2: pulled itself together. And the whole reason that this exists
• 23:33
  Speaker 2: is because of some like early universe perturbation where you
• 23:37
  Speaker 2: had a denser blob of dark matter that created this
• 23:40
  Speaker 2: whole well gathered together the other dark matter and created
• 23:43
  Speaker 2: this over density which then pulled in hydrogen, helium and
• 23:46
  Speaker 2: whatever was around to make a galaxy. So it's a
• 23:49
  Speaker 2: little bit denser at the center. Though it's not very
• 23:52
  Speaker 2: well understood, like if we do calculations simulations to describe
• 23:56
  Speaker 2: what we think should happen. If you have a bunch
• 23:58
  Speaker 2: of dark matter and you'll give it a few billion
• 24:00
  Speaker 2: years to fall together and to form some structure. It
• 24:03
  Speaker 2: describes what astronomers call a cusp, which means like a
• 24:06
  Speaker 2: point of high density of the center and then very
• 24:08
  Speaker 2: steeply falling, should like drop off quickly. But if you
• 24:10
  Speaker 2: go out and measure the actual distributions of stars velocities,
• 24:15
  Speaker 2: you see something that looks like a bigger core. It's
• 24:17
  Speaker 2: not like it's pointing near the center. It's more spread
• 24:20
  Speaker 2: out in the inner galaxy. It's like flatter, and so
• 24:23
  Speaker 2: this is not something we understand very well. And it
• 24:25
  Speaker 2: also gives you a sense of like the scale of
• 24:27
  Speaker 2: which we can figure this stuff out. We're talking about
• 24:30
  Speaker 2: over light years distances, right, we're not resolving dark matter
• 24:33
  Speaker 2: in meters or even in aus with very very coarse
• 24:37
  Speaker 2: ways to measure where the dark matter is. Again, because
• 24:40
  Speaker 2: its gravity is so weak.
• 24:41
  Speaker 1: Are you saying, like the beginning of the universe, dark
• 24:44
  Speaker 1: matter was more evenly spread out, Like you know, all
• 24:46
  Speaker 1: those light years of empty space between us and Andromeda
• 24:49
  Speaker 1: and other galaxies was all filled with dark matter, and
• 24:52
  Speaker 1: then it all collapsed into certain clusters.
• 24:54
  Speaker 2: Yeah, it definitely gathered itself together. The early universe had
• 24:57
  Speaker 2: initial density fluctuations, and that's a whole big question about
• 25:01
  Speaker 2: where exactly that came from. And then those seated gravity
• 25:05
  Speaker 2: to pull things together. So gravity does form structure, but
• 25:08
  Speaker 2: it takes time. And so yeah, dark matter was more
• 25:11
  Speaker 2: spread out and now it's less spread out.
• 25:13
  Speaker 1: Why would dark matter stay stuck together?
• 25:15
  Speaker 2: Well, it's not that dark matter is sticking together. It's
• 25:17
  Speaker 2: not like it's bonded to itself. And again we don't
• 25:19
  Speaker 2: really know because we don't have a microscopic picture of
• 25:22
  Speaker 2: the dark matter. But I think you're asking, like why
• 25:24
  Speaker 2: does dark matter form even gravitational structures? Like why does
• 25:28
  Speaker 2: it get more dense in some places and then in others?
• 25:30
  Speaker 2: Is that what you're asking?
• 25:31
  Speaker 1: Yeah, Like I'm imagining at the beginning of the universe
• 25:33
  Speaker 1: there's a bit of dark matter that was you know,
• 25:36
  Speaker 1: let's say ten light years away, and then it got
• 25:38
  Speaker 1: attracted to our galaxy, so it flew over here. But
• 25:41
  Speaker 1: then why didn't it just keep flying to the other side.
• 25:44
  Speaker 2: Yeah, so as that distant piece of dark matter approaches
• 25:46
  Speaker 2: the galaxy, it gains velocity. Right, it's exchanging gravitational potential
• 25:51
  Speaker 2: energy for kinetic energy. And then you're imagining, like the
• 25:54
  Speaker 2: way a ball rolls down a valley, why doesn't it
• 25:56
  Speaker 2: roll back up the other side? And it will, yes,
• 25:58
  Speaker 2: but then it comes back right, And so gravity in
• 26:01
  Speaker 2: the end is organizing something. There's the second piece to that,
• 26:05
  Speaker 2: which is that it doesn't completely grow back up the
• 26:08
  Speaker 2: other side. You know, anything that's accelerating is emitting gravitational
• 26:12
  Speaker 2: radiation for example. So the reason, for example, two black
• 26:16
  Speaker 2: holes orbiting each other will eventually spiral in and collapse
• 26:20
  Speaker 2: is that they're emitting gravitational energy. So none of these
• 26:23
  Speaker 2: things are really stable. So over long periods of time,
• 26:26
  Speaker 2: even without inelastic interactions like electromagnetism or whatever, these things
• 26:30
  Speaker 2: will form very large structures and they will gradually collapse
• 26:34
  Speaker 2: due to gravitational radiation.
• 26:36
  Speaker 1: All right, so we kind of have a fuzzy picture
• 26:38
  Speaker 1: of where it is in the universe. So now the
• 26:41
  Speaker 1: question of the episode is can we use quantum clocks
• 26:44
  Speaker 1: to detect dark matter? How do quantum clocks fit into this?
• 26:48
  Speaker 2: So quantum clocks might give us a sense for where
• 26:51
  Speaker 2: the dark matter is if we can find a place
• 26:53
  Speaker 2: where it's like clumpy, if we can find a place
• 26:56
  Speaker 2: in our solar system where it's like gathered together for
• 26:59
  Speaker 2: some reason. And that would be really cool because not
• 27:02
  Speaker 2: only would it help us detect what dark matter is,
• 27:05
  Speaker 2: but it would help us understand where it is. It's
• 27:07
  Speaker 2: a really deep mystery, I think, not just because we
• 27:10
  Speaker 2: want to understand dark matter, but because we want like
• 27:12
  Speaker 2: a map. You know, humans are visual creatures. We want
• 27:15
  Speaker 2: to know like where the stuff is, and just not
• 27:17
  Speaker 2: knowing where dark matter is in the universe really bugs me.
• 27:20
  Speaker 2: So I would love to know where it is and
• 27:23
  Speaker 2: understanding its map on a finer scale would be really helpful.
• 27:27
  Speaker 2: And quantum clocks might be able to help us map
• 27:29
  Speaker 2: where dark matter is if we can send them out
• 27:31
  Speaker 2: into space and if they're sensitive to dark matter, if
• 27:35
  Speaker 2: their operation changes as they pass through dark matter.
• 27:38
  Speaker 1: Okay, I think you're saying that you know, at the
• 27:40
  Speaker 1: galaxy level, we know that it looks like a big blob.
• 27:43
  Speaker 1: It's sort of like a switchball. It's sort of more
• 27:45
  Speaker 1: intense or more dense in the center of the galaxy.
• 27:48
  Speaker 1: But I think maybe you're saying, can we know in
• 27:50
  Speaker 1: finer detail what it looks like between stars within the galaxy,
• 27:55
  Speaker 1: like is it clumpy, is it chunky, or is it
• 27:58
  Speaker 1: like peanut butter or smooth exactly?
• 28:01
  Speaker 2: And people have tackled this problem in the past, Like
• 28:04
  Speaker 2: people use the technique you mentioned gravitation lensing to look
• 28:06
  Speaker 2: for blobs of dark matter, and that works and it's powerful,
• 28:10
  Speaker 2: but only if you have like a really nice galaxy
• 28:13
  Speaker 2: behind the blob of dark matter that can show you
• 28:16
  Speaker 2: that it's there, So that tells us a little bit
• 28:18
  Speaker 2: about the dark matter density. But there aren't like galaxies
• 28:21
  Speaker 2: in all the right places to like X ray the
• 28:23
  Speaker 2: whole Solar system and figure out where it is, And
• 28:25
  Speaker 2: that technique isn't always powerful enough. You need like a
• 28:27
  Speaker 2: really big blob of dark matter. Another technique people have
• 28:30
  Speaker 2: used is to look for dwarf galaxies. Essentially, our galaxy
• 28:33
  Speaker 2: is formed by the combination of lots of galaxies, right,
• 28:36
  Speaker 2: we think galaxies formed kind of small and then grew
• 28:39
  Speaker 2: together with all sorts of absorptions and collisions. That means
• 28:42
  Speaker 2: that our galaxy has other, like many galaxies embedded within it.
• 28:46
  Speaker 2: Some of these we call dwarf galaxies because they're small
• 28:49
  Speaker 2: and we think they're like very high dark matter density.
• 28:52
  Speaker 2: They're very few stars, and so we can look at
• 28:55
  Speaker 2: the motion of the stars inside those little galaxies to
• 28:58
  Speaker 2: get sensors for like where those blobs are. But we
• 29:00
  Speaker 2: don't have a great way to like X ray the
• 29:02
  Speaker 2: Solar System and figure out like where is the dark
• 29:05
  Speaker 2: matter in our Solar system? Is it hanging out by Jupiter?
• 29:08
  Speaker 2: Is it spread evenly like peanut butter? What's going on?
• 29:11
  Speaker 1: You want to know it's distribution at the Solar system
• 29:14
  Speaker 1: scale exactly.
• 29:15
  Speaker 2: That's what I want to do. And I read a
• 29:16
  Speaker 2: recent paper which was very clever, which is looking at
• 29:19
  Speaker 2: asteroids and trying to track asteroid trajectories and see if
• 29:22
  Speaker 2: like tiny little deviations in the trajectory of asteroids or
• 29:26
  Speaker 2: comets as they move through the Solar System could reveal
• 29:29
  Speaker 2: the presence of dark matter. It's very difficult to do
• 29:32
  Speaker 2: because if dark matter is evenly spread out or only
• 29:34
  Speaker 2: a little bit clumpy, that be basically no effect on
• 29:37
  Speaker 2: those asteroids. But it's the kind of thing that we're
• 29:40
  Speaker 2: just on the verge of being able to potentially do
• 29:42
  Speaker 2: now that we have better measurements and better computational tools
• 29:45
  Speaker 2: to try to like infer this information from really specific measurements.
• 29:49
  Speaker 1: All right, So then how would you use a quantum
• 29:51
  Speaker 1: clock to de teg dark matter?
• 29:53
  Speaker 2: So when we talk about a quantum clock, really what
• 29:55
  Speaker 2: we mean is something which is based on fundamental quantum
• 29:59
  Speaker 2: mechanical principles. And you know, it sounds fancy, but even
• 30:01
  Speaker 2: just like an atomic clock is a quantum clock. An
• 30:04
  Speaker 2: atomic clock is something that looks at like the oscillation
• 30:07
  Speaker 2: of electron between two energy levels and a caesium atom,
• 30:10
  Speaker 2: which is a very precise, very very regular process that
• 30:15
  Speaker 2: we can use essentially to tell how time has passed.
• 30:18
  Speaker 2: And so on Earth, we have extraordinarily precise atomic clocks
• 30:22
  Speaker 2: which now set the standard and in fact define what
• 30:25
  Speaker 2: we mean by a second. A second used to have
• 30:27
  Speaker 2: a different definition, but now a second is defined as
• 30:30
  Speaker 2: like a certain number of cycles of a specific kind
• 30:32
  Speaker 2: of atom. That's literally how we measure time now, and
• 30:37
  Speaker 2: so it's the standard.
• 30:39
  Speaker 1: But it's like the minute, like it used to be
• 30:41
  Speaker 1: like a minute with sixty seconds, but now people say, oh,
• 30:43
  Speaker 1: it's been a minute to really mean something totally different.
• 30:50
  Speaker 2: Yes, it's just like that exactly. And we call it
• 30:55
  Speaker 2: a quantum clock because this really is a quantum process.
• 30:58
  Speaker 2: We're talking about quantum particles, an electron, there's an atom.
• 31:01
  Speaker 2: The electron is moving in the potential well of the atom,
• 31:04
  Speaker 2: so it's interacting electromagnetically with the nucleus, and the way
• 31:08
  Speaker 2: that it's moving, the way it oscillates between energy levels,
• 31:11
  Speaker 2: is completely controlled by quantum processes. This is not a
• 31:14
  Speaker 2: clock that you could have in a perfectly classical universe.
• 31:17
  Speaker 2: You know, if we lived in a universe where electrons
• 31:19
  Speaker 2: really were tiny little balls that went to orbits and
• 31:21
  Speaker 2: had smooth classical paths the way planets do, then this
• 31:25
  Speaker 2: clock could not exist. And so that's when we meet
• 31:27
  Speaker 2: by quantum clock.
• 31:29
  Speaker 1: But I guess, if it's a quantum clock, doesn't it
• 31:31
  Speaker 1: have a certain amount of uncertainty to it or unknowability?
• 31:34
  Speaker 1: How can it be precise? If there's the Heisenberg uncertainty principle.
• 31:39
  Speaker 2: Yeah, you're right, there's no absolutely precise quantum clock. But
• 31:43
  Speaker 2: this is about as regular as it gets. And amazingly,
• 31:45
  Speaker 2: these quantum clocks are more precise than mechanical clocks, which
• 31:49
  Speaker 2: of course also have uncertainty in them, because no mechanical
• 31:52
  Speaker 2: device is perfectly created, right, And so this is as
• 31:55
  Speaker 2: accurate as they've been able to make them, and recently
• 31:57
  Speaker 2: they've been even able to make them small and transportable.
• 32:01
  Speaker 2: You might think of an atomic clock as like some
• 32:03
  Speaker 2: huge device in the basement of a laboratory in Colorado
• 32:07
  Speaker 2: that weighs like ten tons and fills a room. But
• 32:09
  Speaker 2: actually these things can be made quite small.
• 32:12
  Speaker 1: So a quantum clock is really just an atomic clock,
• 32:14
  Speaker 1: or is there another kind that doesn't use atoms?
• 32:17
  Speaker 2: There's no atomic clock that's not a quantum clock. So
• 32:19
  Speaker 2: quantum clock is just a fancier sounding name for atomic clock.
• 32:22
  Speaker 1: Yes, can you have a quantum clock that maybe doesn't
• 32:24
  Speaker 1: use an atom, that maybe just relies on electrons or
• 32:28
  Speaker 1: quarks or something.
• 32:29
  Speaker 2: Yeah, sure, you're not limited to atoms. You can imagine
• 32:32
  Speaker 2: quantum clocks made out of like photons interacting or splitting
• 32:35
  Speaker 2: or bouncing or something like that. In some sense, lego
• 32:39
  Speaker 2: is a clock because it's measuring the time for photons
• 32:42
  Speaker 2: to travel along its legs, right, It's just converting that
• 32:45
  Speaker 2: to a distance measurement, and so you could have other
• 32:48
  Speaker 2: quantum clocks that are not based on atoms. Yes, And
• 32:51
  Speaker 2: one day, when we discover dark matter, maybe we could
• 32:53
  Speaker 2: build a clock.
• 32:53
  Speaker 1: Out of dark matter, which may or may not tell
• 32:56
  Speaker 1: you the time.
• 32:58
  Speaker 2: And may or may not smell like flatulin.
• 33:00
  Speaker 1: Well, I guess, maybe give us an example of like,
• 33:02
  Speaker 1: what's a typical or popular or a commonly used quantum
• 33:05
  Speaker 1: clock and how does it work.
• 33:07
  Speaker 2: Well, the most precise quantum clock is based on the
• 33:10
  Speaker 2: caesium one thirty three atom. That's the one that's actually
• 33:13
  Speaker 2: used to define what a second is. And so here
• 33:16
  Speaker 2: we have two states of electrons. There's a small splitting
• 33:19
  Speaker 2: in an energy state here. It's called a hyper fine
• 33:22
  Speaker 2: splitting because the difference is very very small, and when
• 33:24
  Speaker 2: the electron sits in there, it sort of goes back
• 33:26
  Speaker 2: and forth between the two different states.
• 33:29
  Speaker 1: Meaning like, this is an electron that's orbiting around the
• 33:32
  Speaker 1: caesium atom.
• 33:33
  Speaker 2: Yeah, I wouldn't say orbiting if we want to be
• 33:35
  Speaker 2: really really technical. But it's captured by the caesium atom.
• 33:38
  Speaker 1: And you're saying it's switching energy levels. Why would it
• 33:40
  Speaker 1: switch energy levels?
• 33:42
  Speaker 2: So you have this caesium atom and you embed the
• 33:44
  Speaker 2: whole thing in some microwave radiation that can lift those
• 33:46
  Speaker 2: electrons up from the lower state to the higher state.
• 33:50
  Speaker 1: Meaning you like put it in a microwave or you
• 33:52
  Speaker 1: shoot it with this like a light gun.
• 33:54
  Speaker 2: There's not a difference, right, that's what a microwave is.
• 33:56
  Speaker 2: A microwave is shooting microwave radiation at your food, and
• 34:00
  Speaker 2: microwaves are lights. Though basically a microwave is a light gun.
• 34:03
  Speaker 1: Sounds hot. So then you have this atom and you
• 34:06
  Speaker 1: you stick it in the microwave.
• 34:07
  Speaker 2: Uh huh, yeah, So you stick in the microwave and
• 34:09
  Speaker 2: you measure how often it jumps up and then down
• 34:12
  Speaker 2: and then up and then down.
• 34:13
  Speaker 1: Because the light, as the light passes through it, it
• 34:16
  Speaker 1: knocks the electron up and down or what.
• 34:18
  Speaker 2: Yeah, the light is tuned to exactly the frequency for
• 34:21
  Speaker 2: the electron to jump up into the higher energy level. Remember,
• 34:24
  Speaker 2: electrons can go from a lower to a higher energy
• 34:27
  Speaker 2: level if a photon of the right energy comes along.
• 34:29
  Speaker 2: So they've tuned this microwave to exactly that energy level.
• 34:33
  Speaker 2: So electrons and the lower level can absorb these photons
• 34:36
  Speaker 2: jump up to the higher level, but then they'll naturally
• 34:38
  Speaker 2: decay down because the universe likes to spread energy out,
• 34:42
  Speaker 2: and so the time of these oscillations turns out to
• 34:45
  Speaker 2: be very very regular, Like an electron will do this
• 34:48
  Speaker 2: nine point one nine to two billion times per second.
• 34:52
  Speaker 1: And it doesn't depend on the frequency of the light,
• 34:54
  Speaker 1: or it does.
• 34:55
  Speaker 2: It definitely depends on the frequency of the light. If
• 34:57
  Speaker 2: the frequency of the light is not correct, then it
• 34:59
  Speaker 2: won't even abso, right, it won't happen.
• 35:01
  Speaker 1: Oh but then don't you need to make that frequency
• 35:04
  Speaker 1: super precise?
• 35:05
  Speaker 2: Yeah, exactly, And this is one source of uncertainty in
• 35:07
  Speaker 2: these clocks, right, making those accurate. And you can measure
• 35:11
  Speaker 2: these things, like you build two independent ones, you can
• 35:13
  Speaker 2: see how their counts drift relative to each other. And
• 35:16
  Speaker 2: that's how you measure the accuracy of clocks. In general.
• 35:19
  Speaker 2: There's no absolute standard by which you can tell like, oh,
• 35:21
  Speaker 2: this clock is off or that clock is off. You
• 35:23
  Speaker 2: just build a few of them and you measure them
• 35:24
  Speaker 2: relative to each other. And this is something that we
• 35:27
  Speaker 2: know well enough. We know how to design the middle
• 35:29
  Speaker 2: of the physics and the engineering that you can build
• 35:32
  Speaker 2: these things so that atomic clocks in independent locations agree
• 35:36
  Speaker 2: to like zero point three nanoseconds per day. It's really
• 35:39
  Speaker 2: very incredibly precise.
• 35:41
  Speaker 1: WHOA, so what are you measuring? How are you measuring
• 35:44
  Speaker 1: whether these electrons are going up and down?
• 35:46
  Speaker 2: When the electron goes back down, it emits radiation, right,
• 35:49
  Speaker 2: and so you can gather that as.
• 35:50
  Speaker 1: Well, like it shoots off light, like it will blink.
• 35:52
  Speaker 2: Basically exactly little flash.
• 35:55
  Speaker 1: All right. So then, and you're saying you can build
• 35:57
  Speaker 1: these things now to be the size of a toaster
• 35:59
  Speaker 1: or or a microwave oven.
• 36:02
  Speaker 2: A quantum toaster. They have them now and they've deployed
• 36:05
  Speaker 2: them out in space. They actually built the Deep Space
• 36:08
  Speaker 2: Atomic Clock Mission and they sent an atomic clock out
• 36:11
  Speaker 2: into space to see, like, hey, can we operate one
• 36:13
  Speaker 2: of these things out in space? And you might wonder
• 36:16
  Speaker 2: like is this just a bunch of nerds trying to
• 36:18
  Speaker 2: do something that seems cool?
• 36:20
  Speaker 1: Yes? Is always the answer, Like can we shoot a
• 36:22
  Speaker 1: microwave into space and will it still heat up my burrito?
• 36:26
  Speaker 1: My seizing Burritoah? Is that the challenge?
• 36:29
  Speaker 2: That's the challenge. But also if we want to do
• 36:31
  Speaker 2: things like navigate in space, navigation needs timing. You need
• 36:35
  Speaker 2: to know like how long you're going in one direction.
• 36:37
  Speaker 2: If you want to do dead reckoning, you want to
• 36:39
  Speaker 2: know where you are. Timing is absolutely crucial. Or if
• 36:42
  Speaker 2: you want to use like nearby pulsars to triangulate your position,
• 36:46
  Speaker 2: my whole episode about how that works, you also need
• 36:49
  Speaker 2: very accurate timing so you can measure the time between
• 36:51
  Speaker 2: the pulses. So this was like a technological challenge that's
• 36:54
  Speaker 2: going to lay the groundwork for all sorts of cool innovations.
• 36:58
  Speaker 2: And this was totally successful, this deep space atomic clock mission.
• 37:01
  Speaker 1: Well, let's get into how you would actually use these
• 37:04
  Speaker 1: and how the timing might tell you where dark matter
• 37:07
  Speaker 1: is within our Solar system and maybe even within the Earth.
• 37:11
  Speaker 1: So let's dig into that. But first let's take another
• 37:14
  Speaker 1: quick break. All right, we're talking about using a microwave
• 37:30
  Speaker 1: stuck inside of a microwave to detect dark matter so
• 37:33
  Speaker 1: you can win a Tierra for being the prettiest scientist.
• 37:37
  Speaker 2: Yeah, exactly. Does it take longer to heat up your
• 37:39
  Speaker 2: burrito when there's dark matter around?
• 37:41
  Speaker 1: So the idea is that you take these atomic or
• 37:44
  Speaker 1: basically an atomic clock, which is a quantum clock, but
• 37:48
  Speaker 1: it seems like the most popular ones use atoms, and
• 37:50
  Speaker 1: so you shrink them down to the size of a
• 37:52
  Speaker 1: toaster or microwave and then you shoot them in space,
• 37:54
  Speaker 1: and then how does that help you measure dark matter?
• 37:57
  Speaker 2: Well, there were a bunch of physicists who thought, okay,
• 37:59
  Speaker 2: this is that's cool because now we not only have
• 38:02
  Speaker 2: all some super precise atomic clocks, but now we have
• 38:05
  Speaker 2: them spread out through the Solar System, like in principle
• 38:08
  Speaker 2: the way we like scent devices near the Sun with
• 38:10
  Speaker 2: a Parker solar probe. People are, what if we built
• 38:12
  Speaker 2: a bunch of these things and we spread them out
• 38:14
  Speaker 2: in the Solar system, could they give us a picture
• 38:17
  Speaker 2: of where the dark matter is in the Solar system
• 38:20
  Speaker 2: if they operate differently when there's dark matter around, like
• 38:23
  Speaker 2: if they're sensitive to the dark matter density, Like if
• 38:26
  Speaker 2: your atomic clock gets off if it drifts when there's
• 38:29
  Speaker 2: more or less dark matter around, than having a bunch
• 38:32
  Speaker 2: of these atomic clocks spread out through the Solar system
• 38:35
  Speaker 2: could give you a picture for where in the Solar
• 38:37
  Speaker 2: System the dark matter is.
• 38:39
  Speaker 1: But I guess what's the mechanism by which dark matter
• 38:42
  Speaker 1: would affect the timing of these clocks.
• 38:45
  Speaker 2: Yeah, so mostly it wouldn't. For many theories of dark matter,
• 38:48
  Speaker 2: dark matter is just some wimp. It's a massive particle
• 38:51
  Speaker 2: that only interacts gravitationally, and so it has essentially no
• 38:54
  Speaker 2: effect on these clocks except for gravitational time dilation. We
• 38:58
  Speaker 2: know the areas with greater mass more curvature, and a
• 39:01
  Speaker 2: curvature causes time dilation, but that would be very, very
• 39:04
  Speaker 2: difficult to measure even with these quantum clocks.
• 39:06
  Speaker 1: But wait, wait, why would it be difficult.
• 39:08
  Speaker 2: You can measure gravitational time dilation with quantum clocks, and
• 39:11
  Speaker 2: we've done that. You can do it on the surface
• 39:13
  Speaker 2: of the Earth, for example, and you could put a
• 39:15
  Speaker 2: quantum clock one meter above another one and you can
• 39:18
  Speaker 2: see the difference between them because one of them is
• 39:21
  Speaker 2: deeper in the curvature than the other. Super duper awesome,
• 39:24
  Speaker 2: but that's because the Earth has a huge amount of
• 39:26
  Speaker 2: gravity and this significant curvature. Here. Dark matter doesn't contribute
• 39:30
  Speaker 2: significantly to the curvature because it's pretty spread out, and
• 39:34
  Speaker 2: we would already know if dark matter wasn't pretty spread out,
• 39:37
  Speaker 2: because we would have seen deviations and like Jupiter's orbit
• 39:39
  Speaker 2: and whatever. So in principle you can, but we don't
• 39:42
  Speaker 2: think it's going to be very sensitive. If you had
• 39:44
  Speaker 2: a lot of quantum clocks and there were much more sensitive,
• 39:46
  Speaker 2: then you could probably detect dark matter local density variations
• 39:50
  Speaker 2: using that.
• 39:51
  Speaker 1: Principle, meaning these clocks would take at a different frequency
• 39:55
  Speaker 1: depending on how close it was to big sources of
• 39:58
  Speaker 1: mass or even sources of mass, because that's just how
• 40:02
  Speaker 1: relativity works.
• 40:03
  Speaker 2: Yeah, that's how relativity works. Remember, in relativity, it is
• 40:05
  Speaker 2: two kinds of time dilation. One is based on speed.
• 40:08
  Speaker 2: If you see a clock moving quickly, then you see
• 40:10
  Speaker 2: it ticking slowly, and that's very confusing because it's relative,
• 40:14
  Speaker 2: and so it depends on two observers. But there's another
• 40:16
  Speaker 2: kind of time dilation, gravitational, which is absolute. It just
• 40:20
  Speaker 2: says anybody in curvature their clock is going to tick slowly,
• 40:23
  Speaker 2: no matter who's looking at it, and everybody's going to
• 40:25
  Speaker 2: agree about whose clock is ticking slowly. So that's very powerful,
• 40:29
  Speaker 2: and that's something you can use to measure just like
• 40:32
  Speaker 2: how much stuff is there in general, because clocks tick
• 40:35
  Speaker 2: slower near stuff. Really kind of an awesome feature of
• 40:38
  Speaker 2: the universe.
• 40:39
  Speaker 1: Meaning like if I had two of these atomic clocks
• 40:41
  Speaker 1: and one of them is out there in the middle
• 40:42
  Speaker 1: of empty space, and the other one is near a
• 40:45
  Speaker 1: big blob of dark matter. The one near the blob
• 40:47
  Speaker 1: of dark matter would take slower.
• 40:50
  Speaker 2: Right, Yeah, that's exactly right.
• 40:52
  Speaker 1: And so you might like start them out in the
• 40:54
  Speaker 1: same spot. But then after being for a while and
• 40:57
  Speaker 1: two different spots, one near the dark matter, and you
• 40:59
  Speaker 1: run a back, you would see that one of them
• 41:02
  Speaker 1: take more ticks than the other.
• 41:03
  Speaker 3: Yeah.
• 41:03
  Speaker 2: So now imagine like a grid, you have a quantum
• 41:06
  Speaker 2: clock every ten meters in the solar system, right, you
• 41:09
  Speaker 2: start them all out at the same time, and then
• 41:11
  Speaker 2: you monitor it, and by measuring the difference in that
• 41:13
  Speaker 2: number of ticks after a year on your reference clock,
• 41:16
  Speaker 2: the one that's hanging out with you, you can tell where
• 41:19
  Speaker 2: stuff is in the solar system.
• 41:21
  Speaker 1: Like which spots in the solar system have slower time.
• 41:24
  Speaker 2: Yes, exactly, because slower time means more matter, more curvature,
• 41:28
  Speaker 2: more energy density.
• 41:29
  Speaker 1: Really, I guess, on top of what you already know
• 41:32
  Speaker 1: about the Solar system right like right now, even if
• 41:35
  Speaker 1: we didn't have dark matter, a clock near the Sun
• 41:38
  Speaker 1: would take slower than a clock here exactly.
• 41:40
  Speaker 2: And we've done some basic version of this, as I
• 41:43
  Speaker 2: said earlier, If a few clocks on Earth at different altitudes,
• 41:46
  Speaker 2: those are different distances from the matter of the Earth
• 41:48
  Speaker 2: and the ones closer do ticks more slowly, and satellites
• 41:52
  Speaker 2: up in space their clocks tick faster than atomic clocks
• 41:55
  Speaker 2: here on the surface of the Earth. And you've got
• 41:57
  Speaker 2: to take that new account famously when you're doing GPS,
• 42:00
  Speaker 2: et cetera.
• 42:00
  Speaker 1: But you're saying, we're not going to be using this effect,
• 42:03
  Speaker 1: this time dilation from relativity to measure dark matter. Dark
• 42:07
  Speaker 1: matter is just too weak.
• 42:08
  Speaker 2: Dark matter is too weak, and we think it's not
• 42:10
  Speaker 2: cluppy enough to really detect that, though it would be
• 42:12
  Speaker 2: super awesome. There's a special kind of dark matter which
• 42:15
  Speaker 2: might give much larger effects, which would be much easier
• 42:18
  Speaker 2: to discover. And this is a theory called fuzzy dark matter.
• 42:22
  Speaker 1: Sounds fuzzy. But wait, so you're saying, like this idea
• 42:27
  Speaker 1: of using atomic clocks to measure dark matter would only
• 42:30
  Speaker 1: work for a certain theoretical meaning guessie type of dark matter,
• 42:37
  Speaker 1: which we don't know whether it's true or not or
• 42:39
  Speaker 1: exists or not. M So this is a huge sources
• 42:42
  Speaker 1: in white scheme that you don't really know if it's
• 42:45
  Speaker 1: going to work.
• 42:46
  Speaker 2: You know, you were talking about nomenclature and now you're
• 42:48
  Speaker 2: using the words guess and scheme. You know, really kind
• 42:51
  Speaker 2: of undermine the credibility of science, but you know, this
• 42:53
  Speaker 2: is good faith stuff. This is like, hey, what if
• 42:55
  Speaker 2: dark matter is this other weird particular thing. How could
• 42:58
  Speaker 2: we see that and yet be best if we had experiments
• 43:01
  Speaker 2: which could detect any kind of dark matter. But you know,
• 43:03
  Speaker 2: there might be kinds of dark matter which we could
• 43:05
  Speaker 2: only detect in certain ways or easier to spot in
• 43:08
  Speaker 2: some ways. And so it's good to be creative and
• 43:10
  Speaker 2: think about how we could detect specific kinds of dark
• 43:13
  Speaker 2: matter as well, even though we don't know what dark
• 43:15
  Speaker 2: matter is. And if this theory is at.
• 43:17
  Speaker 1: All correct, well, I'm just trying to understand the scheme.
• 43:22
  Speaker 1: So are you saying there's a theoretical kind of dark
• 43:24
  Speaker 1: matter called fuzzy dark matter? So what is it? So?
• 43:27
  Speaker 2: Fuzzy dark matter suggests that maybe dark matter isn't very massive,
• 43:31
  Speaker 2: like some people suggest that dark matter could be like
• 43:33
  Speaker 2: one hundred GeV like the mass of a w or
• 43:36
  Speaker 2: a z boson, like one hundred times the mass of
• 43:39
  Speaker 2: a proton, a pretty hefty particle, almost as massive as
• 43:42
  Speaker 2: a Higgs. That's sort of the classic strategy, and there's
• 43:45
  Speaker 2: reasons for that. There's something called the wimp miracle check
• 43:48
  Speaker 2: in our podcast about that, which argues strongly that dark
• 43:51
  Speaker 2: matter should be around one hundred gv based on how
• 43:54
  Speaker 2: much of it there is in the universe. But people
• 43:56
  Speaker 2: are like, well, maybe that's all wrong, and there's an
• 43:58
  Speaker 2: assumption there that's wrong. What if dark matter super duper light,
• 44:01
  Speaker 2: like a trilliance the mass of an electron. So now
• 44:04
  Speaker 2: there's an enormous number of these dark matter particles, so
• 44:08
  Speaker 2: many more than you could even imagine, because you have
• 44:10
  Speaker 2: to somehow make like a big fraction of the mass
• 44:13
  Speaker 2: of the universe out of particles that are a tiny
• 44:16
  Speaker 2: fraction of the mass of the electron, which is already
• 44:19
  Speaker 2: very very light.
• 44:20
  Speaker 1: Well, first of all, I think this whole podcast is
• 44:22
  Speaker 1: a wimp miracle, Daniel. But I think you're saying, like
• 44:26
  Speaker 1: this version of dark matter, instead of being maybe marble
• 44:29
  Speaker 1: sized particles, they're like super tiny bb sized particles. And
• 44:33
  Speaker 1: some of that makes it fuzzier.
• 44:35
  Speaker 2: Yeah, it makes it fuzzier because if they're very very
• 44:37
  Speaker 2: low mass, then their wavelengths are more spread out. Some
• 44:40
  Speaker 2: of these things can have a wavelength like the size
• 44:43
  Speaker 2: of the galaxy.
• 44:44
  Speaker 1: What do you mean a wavelength?
• 44:45
  Speaker 2: The wavelength of a particle is like the distance on
• 44:47
  Speaker 2: which these quantum interference effects appear, and so you can
• 44:51
  Speaker 2: calculate this quantity. It's called the Debrogely wavelength. You'll see
• 44:54
  Speaker 2: wave like effects for a particle when you interact over
• 44:58
  Speaker 2: these kinds of distances, and that's the wavelength of a particle.
• 45:01
  Speaker 1: Meaning sort of like the size of it kind of right.
• 45:03
  Speaker 2: Sort of, Yeah, it's when it stops acting like a
• 45:05
  Speaker 2: blob like a particle and starts acting more like a wave.
• 45:09
  Speaker 2: Things that have wavelike behaviors. Really, it's always acting like
• 45:12
  Speaker 2: a wave. It's just that when you zoom out you
• 45:14
  Speaker 2: can approximate it as a particle.
• 45:15
  Speaker 1: Because they have low mass. What's the relationship between having
• 45:18
  Speaker 1: low mass and being having big wavelengths.
• 45:21
  Speaker 2: Well, the wavelength depends on your momentum and your mass,
• 45:24
  Speaker 2: So lower mass just means a larger wavelength because it's
• 45:28
  Speaker 2: really like a ratio between the momentum and the mass.
• 45:31
  Speaker 2: When things have a lot of kinetic energy relative to
• 45:33
  Speaker 2: their mass, they act more like light because light is
• 45:35
  Speaker 2: pure kinetic energy. When things have very small amounts of
• 45:38
  Speaker 2: energy relative to their mass, they're stationary, so they act
• 45:41
  Speaker 2: more like bits of sand, like particles, and so it's
• 45:44
  Speaker 2: just sort of a rough way to understand where that
• 45:47
  Speaker 2: transition happens.
• 45:48
  Speaker 1: Okay, So, then if dark matter is this kind of
• 45:50
  Speaker 1: fuzzy kind of dark matter, you're saying that each particle
• 45:53
  Speaker 1: would be super duper light, and it would also have
• 45:56
  Speaker 1: huge variations in their size. That's what you mean by fuzzy.
• 46:00
  Speaker 1: It's like they might be some of them might be
• 46:01
  Speaker 1: super big and somewhere might be super small.
• 46:03
  Speaker 2: Yeah. Well, the wavelengths could be very very large, which
• 46:06
  Speaker 2: means they can interact over long distances. But the fascinating
• 46:09
  Speaker 2: thing is that in simulations of this dark matter, it
• 46:11
  Speaker 2: predicts like a mini halo of dark matter in our
• 46:14
  Speaker 2: Solar system, essentially that this stuff would be clumped up
• 46:17
  Speaker 2: in and near the Sun. That most of the dark
• 46:20
  Speaker 2: matter in the Solar System might be like clumped up
• 46:23
  Speaker 2: near the Sun. It might be like hiding in the Sun.
• 46:26
  Speaker 1: And if it wasn't this kind of fuzzy dark matter,
• 46:28
  Speaker 1: it wouldn't.
• 46:29
  Speaker 2: Now, this kind of fuzzy dark matter is the kind
• 46:31
  Speaker 2: we think would clump up like a.
• 46:33
  Speaker 1: Halo near the Sun, and the other kinds wouldn't.
• 46:35
  Speaker 2: Yeah, the other kinds wouldn't necessarily, I mean, I've heard
• 46:38
  Speaker 2: of other theories of dark matter clumping in the Sun.
• 46:40
  Speaker 2: There's all sorts of theories, but this particular one tends
• 46:44
  Speaker 2: to make a halo near the Sun and would affect
• 46:47
  Speaker 2: the operation of quantum clocks because of its special fuzziness.
• 46:50
  Speaker 2: It can also slightly interact with electrons through sort of
• 46:54
  Speaker 2: like a back door in quantum mechanics, which would change
• 46:56
  Speaker 2: the way a quantum clock operates. It's like it changes
• 46:59
  Speaker 2: the electrons math and how it responds to photons because
• 47:02
  Speaker 2: of oscillations in this fuzzy dark matter field, and so
• 47:06
  Speaker 2: effectively it changes the frequency of these clocks. And so
• 47:10
  Speaker 2: you can detect in principle whether you're near a dense
• 47:13
  Speaker 2: blob of this ultra light dark matter by looking at
• 47:16
  Speaker 2: a quantum clock and counting its ticks very carefully. And
• 47:19
  Speaker 2: this would be a bigger effect than the effect we
• 47:21
  Speaker 2: talked about earlier, the gravitational curvature.
• 47:24
  Speaker 1: But I thought that dark matter couldn't interact with regular
• 47:26
  Speaker 1: matter only through it could only do it through gravity.
• 47:29
  Speaker 2: Yeah, it could only do it through gravity in general,
• 47:31
  Speaker 2: But this one takes a back door through the Higgs field.
• 47:34
  Speaker 2: It like interacts with the Higgs field and it changes
• 47:36
  Speaker 2: how the Higgs field works, and so near the presence
• 47:39
  Speaker 2: of this ultra light dark matter, electrons effectively have a
• 47:42
  Speaker 2: different mass.
• 47:43
  Speaker 1: But I guess if that was true, wouldn't we see
• 47:46
  Speaker 1: it effect regular matter on a larger scale.
• 47:49
  Speaker 2: You would see it happen, but it's a subtle effect,
• 47:51
  Speaker 2: and so you need to be near a dense clump
• 47:53
  Speaker 2: of it. So the idea is, take something that's very
• 47:56
  Speaker 2: very sensitive to the electron mass, like a quantum clock,
• 47:59
  Speaker 2: and try to put it near a dense clump of
• 48:01
  Speaker 2: this special ultra light dark matter, maybe near the Sun.
• 48:04
  Speaker 2: So that's the idea is, like launch a bunch of
• 48:06
  Speaker 2: quantum clocks, have them orbit near the Sun, and look
• 48:09
  Speaker 2: for deviations in their timekeeping, and see if that's evidence
• 48:12
  Speaker 2: for ultra light dark matter interfering with the masses of
• 48:15
  Speaker 2: the electrons in these quantum clocks.
• 48:18
  Speaker 1: We mean that you would maybe like throw a bunch
• 48:19
  Speaker 1: of the sun, have them kind of form a half
• 48:22
  Speaker 1: ring around the Sun to see if time changes there,
• 48:25
  Speaker 1: sort of like a giant tirra, like.
• 48:28
  Speaker 2: A giant tr a quantum cosmic tira.
• 48:31
  Speaker 1: All right, But I guess which one would you be proving?
• 48:33
  Speaker 1: Would you be proving that dark matter is fuzzy, or
• 48:36
  Speaker 1: would you be proving that it's there? Or are they
• 48:39
  Speaker 1: both related?
• 48:40
  Speaker 2: They're both related.
• 48:41
  Speaker 4: Though.
• 48:41
  Speaker 2: You know, if we saw this thing, there would instantly
• 48:43
  Speaker 2: be like fifty other theories to explain it as well.
• 48:47
  Speaker 2: It probably wouldn't be a unique prediction of this kind
• 48:49
  Speaker 2: of dark matter. Theories are very very clever people, and
• 48:52
  Speaker 2: they'll always come up with another way to explain the
• 48:54
  Speaker 2: data that we were seeing. But it's cool because it's
• 48:57
  Speaker 2: a prediction that this theory makes and we go out
• 48:59
  Speaker 2: and we see it. That's really fascinating, and then we
• 49:02
  Speaker 2: can think about ways to distinguish all the different ideas
• 49:04
  Speaker 2: that might also explain this kind of observation. It would
• 49:08
  Speaker 2: just be cool to see something different. Currently, all of
• 49:10
  Speaker 2: our dark matter experiments basically see nothing. It would be
• 49:14
  Speaker 2: cool to have a signal somewhere.
• 49:16
  Speaker 1: So you're thinking, hey, let's put a bunch of microways
• 49:18
  Speaker 1: in space and see if it sticks exactly.
• 49:21
  Speaker 2: Let's see if one burrito is a little bit colder
• 49:23
  Speaker 2: than another.
• 49:24
  Speaker 1: All right, Well, an interesting idea for how we could
• 49:26
  Speaker 1: maybe possibly crack sort of a theoretical version of one
• 49:31
  Speaker 1: of the biggest mysteries in the universe.
• 49:33
  Speaker 2: That's right. Physicists are being very creative and trying to
• 49:35
  Speaker 2: come up with new theories of dark matter and new
• 49:38
  Speaker 2: ways to discover them, including using super duper sets in
• 49:42
  Speaker 2: quantum clocks distributed through the solar system, which also would
• 49:46
  Speaker 2: just be fun to do.
• 49:47
  Speaker 1: You just want to parade, Daniel, I just want a Tiara?
• 49:50
  Speaker 2: Is that too much to ask?
• 49:53
  Speaker 1: How about we just buy you a Tiara?
• 49:55
  Speaker 2: Is it made of dark matter? Are you using your bitcoin?
• 49:57
  Speaker 1: It can be, but in any way that you want.
• 50:00
  Speaker 1: But if it's saves tax dollars billions of dollars, you know,
• 50:03
  Speaker 1: it would be a pretty good investment.
• 50:05
  Speaker 2: Yeah, there we go. That was my scheme the whole time.
• 50:07
  Speaker 1: Yeah, to get us to buy you at tiara without
• 50:10
  Speaker 1: actually having to run in a beauty contest.
• 50:13
  Speaker 2: I'm busted.
• 50:15
  Speaker 1: Well, you are the most beautiful podcaster with a show
• 50:19
  Speaker 1: called Daniel Jorge Explaining the Universe. So whose name is Daniels?
• 50:23
  Speaker 2: I'll take very highly qualified compliments, thank you.
• 50:26
  Speaker 1: It's a very specific tiara based on a very theoretical
• 50:31
  Speaker 1: model of the universe.
• 50:33
  Speaker 2: Fuzzy compliments from Morehey, all.
• 50:34
  Speaker 1: Right, well we hope you enjoyed that. Thanks for joining us.
• 50:37
  Speaker 1: See you next time.
• 50:43
  Speaker 2: For more science and curiosity, come find us on social media,
• 50:46
  Speaker 2: where we answer questions and post videos. We're on Twitter, Discord, Instant,
• 50:51
  Speaker 2: and now TikTok. Thanks for listening, and remember that Daniel
• 50:55
  Speaker 2: and Jorge Explain the Universe is a production of Iheartworting.
• 50:59
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• 51:04
  Speaker 2: or wherever you listen to your favorite shows.