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Speaker 1: Hey, Daniel, if you were dark Matter, where would you hide?

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Speaker 2: I wouldn't hide. If I was dark matter, I would

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Speaker 2: totally parade myself in front of all the scientists in

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Speaker 2: the galaxy.

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Speaker 1: Ooh, a parade. You mean like a pageant.

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Speaker 2: Queen, Yeah, something like that. You know, just don't be

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Speaker 2: so shy.

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Speaker 1: Well, if it turns out you are dark matter, we'll

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Speaker 1: definitely throw you a parade. But so far, it seems

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Speaker 1: like dark matter is kind of reclusive, right, It's kind

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Speaker 1: of shy, So maybe it is hiding. What would be

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Speaker 1: some good spots for it to hide it?

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Speaker 2: Well, if dark matter doesn't want a tiara and it's

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Speaker 2: hiding somewhere, then I don't know where it would hide.

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Speaker 2: I mean, if I knew, I would go and look

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Speaker 2: for it there.

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Speaker 1: What if it's somewhere kind of.

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Speaker 2: Obvious, like what like right behind me?

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Speaker 1: Yeah, or right in front of you, or right on

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Speaker 1: TV and the Matter universe contest, that.

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Speaker 2: Would be a great twist ending for the m Knight

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Speaker 2: Shamanlan version of this story.

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Speaker 1: Well, man, do you think he knows I see dark Matter?

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Speaker 3: Hi?

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Speaker 1: I'm Jorge Mack, cartoonists and the author of Ollor's Great

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Speaker 1: Big Universe.

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Speaker 4: Hi.

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Speaker 2: I'm Daniel. I'm a particle physicist, and I wish I

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Speaker 2: had a dark matter Tiara.

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Speaker 1: Oh, but it wouldn't be very shiny or bright. It

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Speaker 1: would be dark, So what's the point. Also, when it

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Speaker 1: had just fall through your head, it.

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Speaker 2: Would be hard to wear, but it'd be like the greatest,

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Speaker 2: most amazing piece of jewelry.

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Speaker 1: Ever, how would you even keep it in your house?

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Speaker 2: These are just like engineering details, you know. Once I've

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Speaker 2: solved the physics of a dark matter Tiara, I'll just

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Speaker 2: pass that off to the engineers.

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Speaker 1: This is just all part of your dream to be

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Speaker 1: the universe's doctor Universe.

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Speaker 2: I would like a little bit of bling. Yeah, you know,

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Speaker 2: physics blining would be nice. I'm not going to win

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Speaker 2: a Nobel Prize anytime soon, So dark matter Tira sounds good.

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Speaker 1: I see. I see. You could just say you have

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Speaker 1: a dark matter Tierra, and they nobody would be able

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Speaker 1: to see it, or feel it or detect it. They

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Speaker 1: would just have to believe you.

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Speaker 2: I need evidence, man, That's what science is all about.

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Speaker 2: You got to have data.

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Speaker 1: I don't think those beauty contests depend on data very much.

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Speaker 2: But I'm trying to win a science contest.

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Speaker 1: But anyway's welcome. Dark podcast Daniel and Jorge Explain the Universe,

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Speaker 1: a production of iHeartRadio in which.

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Speaker 2: We enter you in the greatest science contest of all time,

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Speaker 2: the quest to understand the nature of the universe. What

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Speaker 2: is it, what's in it, what's it made out of?

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Speaker 2: How does it all work. We think these questions are

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Speaker 2: deep and fundamental parts of being a human being in

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Speaker 2: this cosmos, and unraveling these questions is a joy that

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Speaker 2: everybody should share. So on this podcast we take those

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Speaker 2: questions apart and try to share our answers and our

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Speaker 2: ignorance with you.

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Speaker 1: That's right, because science is the greatest beauty contest in

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Speaker 1: the universe, where the goal is to discover the beauty

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Speaker 1: of how this universe is put together, how it works,

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Speaker 1: and what is our place in it.

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Speaker 2: Over the last fifty one hundred years, we've developed a

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Speaker 2: pretty good sense for what's in the universe. We know

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Speaker 2: about stars and galaxies and all the bright and shiny

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Speaker 2: stuff that's out there in the universe, and we've also

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Speaker 2: figured out that there's a lot of the universe that

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Speaker 2: we can't see directly using our senses or any of

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Speaker 2: the forces that we've discovered except for gravity. We know

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Speaker 2: that a huge chunk of the stuff that's out there

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Speaker 2: in the universe is invisible. It's intangible, which makes it

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Speaker 2: very hard to discover and to figure out how to

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Speaker 2: make it into a tiara.

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Speaker 1: Yeah, because it turns out that a pretty good understanding

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Speaker 1: of the universe only covers about uh five percent of

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Speaker 1: what we know is out there. The rest, the ninety

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Speaker 1: five percent of the universe that we know is there,

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Speaker 1: we have no idea what it is or how it works.

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Speaker 2: That sounds like a good title for a book.

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Speaker 1: Yeah, I think we rode One Daniel, which is available

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Speaker 1: for a sale everywhere.

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Speaker 2: That's right. The kind of stuff that you and I

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Speaker 2: are made out of, atoms specifically, or what physicists called baryons,

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Speaker 2: only makes up five percent of the energy budget in

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Speaker 2: the universe. There's another twenty five twenty seven percent that's

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Speaker 2: dark matter, some kind of stuff that we know is matter.

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Speaker 2: We know it's out there, but we don't know what

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Speaker 2: it is, and we only have a very rough sense

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Speaker 2: of even where it is around us. The rest of

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Speaker 2: the universe is something we call dark energy, which is

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Speaker 2: contributing to the accelerating expansion of the universe and we

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Speaker 2: have even less clue about what makes that up.

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Speaker 1: Yeah, there's a lot we don't know, and it seems

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Speaker 1: like these are maybe the defining mysteries of our times

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Speaker 1: is to figure out what the universe is actually made

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Speaker 1: out of, given that what we're made out of counts

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Speaker 1: is so little of it.

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Speaker 2: Yeah, you're right. And in the last few decades there's

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Speaker 2: been a huge program of people looking for dark matter.

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Speaker 2: We've talked on the podcast about trying to make dark

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Speaker 2: matter in the laboratory by smashing particles together. We're searching

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Speaker 2: for the dark matter wind. We might be floating through

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Speaker 2: with very sensitive underground facilities looking for an individual piece

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Speaker 2: of dark matter to bump into liquid xenon, for example,

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Speaker 2: or maybe evidence of dark matter annihilating itself in the

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Speaker 2: center of the galaxy. But so far, none of these

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Speaker 2: experiments have found dark matter, which means we've got to

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Speaker 2: get creative about other ways to maybe detect this most

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Speaker 2: important or at least most common kind of matter in

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Speaker 2: the universe.

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Speaker 1: So to be on the podcast, we'll be tackling the

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Speaker 1: question could quantum clocks detect dark matter and how many

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Speaker 1: jargon words can we fit into one podcast title.

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Speaker 2: I know it does sound like buzzword sound, you know, like,

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Speaker 2: could we use AI generated crypto bitcoin to detect dark matter?

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Speaker 1: You mean quantum nanomtter Yes, exactly, quantum nanomtter tierras.

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Speaker 2: Wow, I like quantum nano matter. I go use that

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Speaker 2: in a proposal.

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Speaker 1: That's good, I said it first, I said at first, Daniel. Also,

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Speaker 1: it's probably already on sale on Amazon. There's probably some

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Speaker 1: product out there with that name.

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Speaker 2: So yeah, but you didn't say ching tm after it,

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Speaker 2: so I can use it.

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Speaker 1: No, you don't have to.

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Speaker 2: What I gotta brush up on my podcast property law.

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Speaker 1: Yeah, you better or else I'm gonna see you for

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Speaker 1: nano dollars for nano bitcoins, you know what?

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Speaker 2: Or hey, you can have all of my nano bitcoins.

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Speaker 1: What's the price of bitcoins these days?

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Speaker 2: Nano bitcoins zero? Yeah, doesn't exist.

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Speaker 1: But anyways, it's kind of an intriguing title. Could quantum

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Speaker 1: clocks detect dark matter? And quantum clocks sounds like it

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Speaker 1: does sound like something you could buy an off of Amazon.

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Speaker 1: Did you check to see if it's something you can

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Speaker 1: just get next day?

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Speaker 3: Oh?

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Speaker 2: Yeah, it turns out Amazon will sell you something. It

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Speaker 2: calls a quantum clock, like a quantum entanglement led wall clock,

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Speaker 2: but none of these things are actually quantum clocks the

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Speaker 2: way that we understand them.

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Speaker 1: Well, technically, isn't everything a quantum something? Well, I mean

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Speaker 1: not everything, but you know, the five percent that we

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Speaker 1: know about in the universe is in it all quantum technically,

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Speaker 1: like this is a quantum podcast.

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Speaker 2: I mean, that's a really interesting philosophical question and not

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Speaker 2: one that we really have an answer to, because on

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Speaker 2: one hand, you're right that everything is made out of

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Speaker 2: quantum particle, so isn't the whole universe quantum? On the

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Speaker 2: other hand, we know that when you zoom out things

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Speaker 2: behave by different rules. We call that classical. We don't

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Speaker 2: really understand why there is that transition, but there definitely

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Speaker 2: is a transition. So to call everything quantum is either

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Speaker 2: to say that look classical is just big zoomed out quantum,

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Speaker 2: or is to say that clackical doesn't really matter, which

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Speaker 2: doesn't really sit well with me. Or what if I

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Speaker 2: have no class, then you probably have a lot of

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Speaker 2: big coin.

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Speaker 1: Then I'm not going to win any beauty contest. I

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Speaker 1: have poise, but just no class.

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Speaker 2: Yeah, exactly, But you know, for example, a clock that

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Speaker 2: just works on mechanical parts would also work in the

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Speaker 2: universe where quantum mechanics didn't rule the microscopic because it's

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Speaker 2: not sensitive to those microscopic details, and so that wouldn't

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Speaker 2: be a quantum clock, for example, like a pendulum clock

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Speaker 2: or an old fashioned Swiss gear based clock.

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Speaker 1: A discussion about new mankla Sure that's my favorite.

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Speaker 2: Hey, you brought it up, But.

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Speaker 1: Anyways, it's a kind of an interesting question and so

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Speaker 1: we'll dig into it. But as usually, we were wondering

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Speaker 1: how many people out there had thought about putting the

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Speaker 1: concepts of dark matter and quantum and clocks all together

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Speaker 1: in one sentence.

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Speaker 2: So thanks very much to everybody who participates in this

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Speaker 2: segment of the podcast. We love that you volunteer, We

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Speaker 2: love hearing your thoughts, and we love sharing your voice

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Speaker 2: with all of the other listeners. Please chime in if

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Speaker 2: you'd like, writeing me two questions at Danielanjorge dot com

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Speaker 2: and you can't participate.

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Speaker 1: So think about it for a second. Do you think

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Speaker 1: quantum clocks can use to detect dark matter? Here's what

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Speaker 1: people had to say.

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Speaker 4: I've heard of a quantum clock, but I'm not sure

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Speaker 4: how it would be able to detect dark matter anymore

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Speaker 4: than a regular clock could. I guess maybe even with

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Speaker 4: a regular clock, you could send it out into space,

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Speaker 4: and if it hits a huge clump of dark matter

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Speaker 4: and therefore gravity, maybe we could learn that there's a

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Speaker 4: big well of gravity out in some location that we

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Speaker 4: otherwise couldn't detect.

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Speaker 1: So sure, I suppose it's possible, but I have no

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Speaker 1: clue how it would Maybe something to do with entanglement.

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Speaker 3: Since you're asking, the answer is probably yes, but maybe

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Speaker 3: still theoretical. I would think you'd have to use the

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Speaker 3: idea of measuring light passing through an area of more

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Speaker 3: density that's possibly dark matter that causes curvature of space

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Speaker 3: and also time dilation. How to do that, I'm not sure.

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Speaker 2: Since we don't possess a quantum clock, it doesn't seem

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Speaker 2: unreasonable to suggest that a non existent clock cannot detect

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Speaker 2: dark matter.

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Speaker 1: All right, it's pretty uh intense answers here. I feel

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Speaker 1: like it's something that some of the listeners have I

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Speaker 1: heard about before. Did you pull your professor colleagues this time?

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Speaker 2: No, these are our listeners online. You know there's some

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Speaker 2: good answers here about entanglement and light passing through areas

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Speaker 2: with dark matter density in them, and just in general

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Speaker 2: sense that this is a hard problem.

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Speaker 1: Maybe you should ask a bunch of beauty queens next

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Speaker 1: time we're making one of the standard questions in a

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Speaker 1: beauty pageant. Forget howdy, how would you save the world

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Speaker 1: or how would you know make things better? What do

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Speaker 1: you think about quantum plock?

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Speaker 2: Well, where is the dark matter? Yeah, I'd love to

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Speaker 2: hear that answer in the beauty pageant.

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Speaker 1: Not that it couldn't happen, of course, no, absolutely. All right, Well,

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Speaker 1: let's dig into this intriguing question of whether dark matter

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Speaker 1: can be detected by quantum clocks, and let's start with

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Speaker 1: the basics, Daniel, what do we know about dark matter?

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Speaker 2: So there's a lot that we do and do not

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Speaker 2: know about dark matter. So let's start with what we

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Speaker 2: do know. We know that it's out there, and we

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Speaker 2: know that it's here as well. We know that dark

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Speaker 2: matter is something that exists in the universe. And then

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Speaker 2: it's matter. We know that because we see its gravity.

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Speaker 2: We see it holding galaxies together as they spin. There

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Speaker 2: isn't enough gravity from the stars and the gas and

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Speaker 2: dust that make up those galaxies to keep the stars

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Speaker 2: in place as they swirl around the center of the

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Speaker 2: galaxy at very high speeds, and yet they do stay

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Speaker 2: in place. Galaxies are mostly not throwing stars out into

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Speaker 2: intergalactic space, and so we infer that there must be

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Speaker 2: some matter there to hold that galaxy together. But it's

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Speaker 2: more than just that one inference, that one fudge factor

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Speaker 2: to make that particular equation work. We see evidence for

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Speaker 2: dark matter all over the history of the universe, from

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Speaker 2: the very first few moments when the early universe plasma

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Speaker 2: is slashing around and you have dark matter and normal

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Speaker 2: matter and photons all acting very differently and creating different

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Speaker 2: slashing patterns. From looking at that slashing in the cosmic

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Speaker 2: microwave background radiation, we can figure out that there was

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Speaker 2: dark matter, even measure how much of it there is,

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Speaker 2: and we can trace the history of dark matter's gravity

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Speaker 2: as it shapes the structure formation of the whole universe.

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Speaker 2: Why we have galaxies at all this early in the

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Speaker 2: history of the universe, and so dark matter is definitely

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Speaker 2: out there as a kind of matter, but we don't

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Speaker 2: know really what it is or very specifically where it

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Speaker 2: is because it's so hard to see since it only

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Speaker 2: feels gravity. It doesn't feel any of the other forces

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Speaker 2: that we've discovered.

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Speaker 1: And we can also sort of see dark matter right like,

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Speaker 1: we can see it in the same way that you

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Speaker 1: can see a lens or glass lens or example. You

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Speaker 1: can see how it distorts the light behind it.

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Speaker 2: Right, Yeah, exactly, we can see dark matter through gravity,

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Speaker 2: and so that means we can see stuff bending around

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Speaker 2: dark matter. We can see it holding galaxies together, and

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Speaker 2: that even impacts how light moves in the vicinity of

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Speaker 2: dark matter. If you have a big blob of dark

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Speaker 2: matter between you and some distant galaxy, for example, the

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Speaker 2: photons from that distant galaxy will bend as they move

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Speaker 2: through that dark matter, creating apparent distortions in your image.

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Speaker 2: You can even sometimes see the same galaxy twice in

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Speaker 2: the sky because of this gravitational lensing, and so we

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Speaker 2: know that it's out there, and we can use some

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Speaker 2: techniques like that to sometimes tell roughly where it is.

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Speaker 2: But because dark matter is so weak it's particles only

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Speaker 2: feel gravity, we think it's very difficult to figure out

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Speaker 2: what exactly is made out of To isolate one piece

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Speaker 2: of dark matter, because gravity is so weak that essentially

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Speaker 2: a particle's gravity is almost impossible to measure.

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Speaker 1: Yeah, and dark matter is also something that's not just

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Speaker 1: out there in space. It's sort of like all around us,

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Speaker 1: right like it's floating through us right now, sort of

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Speaker 1: like the fourth you know, it flows through us, binds

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Speaker 1: us all together. It's made out of meti chlorians.

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Speaker 2: Perhaps, perhaps, yeah, exactly, you'll only really understand it after

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Speaker 2: nine hundred years of study. That's a really good question,

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Speaker 2: and that's sort of the central question of this episode

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Speaker 2: is exactly where is the dark matter and can we

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Speaker 2: find like concentrations of it? Can we map it out?

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Speaker 2: Because dark matter is so weakly interacting like only gravity,

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Speaker 2: it takes huge amounts of it to feel anything, and

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Speaker 2: so that makes it very hard to tell exactly where

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Speaker 2: the dark matter is. It might be that it's mostly

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Speaker 2: spread out evenly through the galaxy. It might be more

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Speaker 2: clumpy than that depends a lot on your particular theory

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Speaker 2: of dark matter. Where it exactly is. So it could

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Speaker 2: be that we are in a dark matter wind as

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Speaker 2: the Earth orbits the Sun and the Sun moves through

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Speaker 2: the galaxy. We could also be in a dark matter

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Speaker 2: Liss bubble, a bubble of space in which there's comparatively

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Speaker 2: little dark matter, or it could be that dark matter

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Speaker 2: is fairly dense in our area.

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Speaker 1: You know, I have to say every time you say

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Speaker 1: dark matter wind, it makes me think of dark.

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Speaker 2: Part elevating the discourse every week.

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Speaker 1: That's my job. That's why I'm here. Smells all grounded

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Speaker 1: or grounded or you know, flat as in fletch winds.

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Speaker 1: But anyways, so it's sort of all around this, and

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Speaker 1: I guess I'm wondering, like, if it is all around us,

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Speaker 1: would we be able to tell, Like, you know, if

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Speaker 1: let's say dark matter is floating through the Earth right now,

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Speaker 1: or let's say it wasn't, would you be able to

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Speaker 1: tell the difference.

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Speaker 2: That's exactly what these experiments are trying to measure. And

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Speaker 2: to give you a sense of the difficulty the challenge

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Speaker 2: of this, think about like why we didn't discover dark

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Speaker 2: matter earlier. Just in studying how our Solar system moves.

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Speaker 2: We have now very precise measurements of the orbit of

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Speaker 2: Jupiter and Mars and all the planets and all the

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Speaker 2: little pieces of the Solar System as they orbit the Sun.

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Speaker 2: You might think, hey, if dark matter is here in

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Speaker 2: our Solar system and it has gravity, wouldn't it change

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Speaker 2: the way those things orbit? Shouldn't we be able to

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Speaker 2: detect it? But because we think dark matter might be

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Speaker 2: spread very thin, probably there isn't that much dark matter

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Speaker 2: in the vicinity of our solar system. So even those

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Speaker 2: very very precise measurements, you know, like knowing the motion

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Speaker 2: of Jupiter to meters or centimeters, can't detect dark matter

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Speaker 2: because it would be very thin and very spread out,

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Speaker 2: and mostly we think homogeneous, which in the end doesn't

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Speaker 2: give much much gravitational pull on the objects in the

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Speaker 2: solar system. So it takes a very specialized, highly sensitive

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Speaker 2: device to be able to detect this dark matter.

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Speaker 1: Yeah, and then don't we say once like, if you

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Speaker 1: take all the dark matter that is potentially floating through

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Speaker 1: the Earth right now, it would only weigh about as

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Speaker 1: much as a squirrel or something like that.

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Speaker 2: Yeah, exactly, though that's very speculative, right. That assumes that

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Speaker 2: dark matter is essentially equally spread out in our galaxy,

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Speaker 2: which we don't believe is true. But if you assume

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Speaker 2: that there is, then we know our galaxy, for example,

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Speaker 2: is ninety five percent dark matter. That means for every

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Speaker 2: kilogram of matter made out of atoms like hydrogen and

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Speaker 2: helium or whatever, there's nineteen kilograms of matter made out

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Speaker 2: of whatever dark matter is made out of, And so

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Speaker 2: it's like nineteen to one in our galaxy.

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Speaker 1: Which sounds like a lot, but I guess also galaxies

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Speaker 1: kind of very empty mostly, right, Like it's probably like

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Speaker 1: ninety nine percent empty.

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Speaker 2: Yeah, exactly. Now, normal matter clumps up a lot, right

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Speaker 2: like the Sun is an extraord ordinarily dense collection of

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Speaker 2: normal matter. Normal matter is not spread evenly through the galaxy.

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Speaker 2: But if you take dark matter and spread it evenly

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Speaker 2: through the galaxy, you get a pretty small density. It's

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Speaker 2: like ten to the twenty six kilograms per cubic light year,

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Speaker 2: which is a huge volume, which means it's like ten

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Speaker 2: to the negative twenty two kilograms per cubic meter. So

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Speaker 2: then if you add up all the cubic meters in

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Speaker 2: the Earth, that adds up to about two thirds of

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Speaker 2: a kilogram of dark matter inside the volume of the Earth. Again,

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Speaker 2: assuming that dark matter is evenly spread throughout the galaxy,

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Speaker 2: which it probably isn't, but it might be.

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Speaker 1: Roughly, which is about the size or mass of a squirrel.

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Speaker 2: Yeah, exactly, so one squirrel of dark matter inside the

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Speaker 2: volume of the Earth compared to you know, the many,

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Speaker 2: many millions and billions of kilograms of normal matter inside

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Speaker 2: the volume of the Earth. That sounds the importance of clumping, right,

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Speaker 2: Because normal matter clumps together, its gravity is much more

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Speaker 2: powerful in our local neighborhood than dark matter. Even though

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Speaker 2: dark matter outweighs normal matter by nineteen to one, if

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Speaker 2: it's much more thinly spread out, the local effects of

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Speaker 2: its gravity are much harder to detect.

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Speaker 1: I think maybe what you're saying is that dark matter,

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Speaker 1: in terms of the universe scale, it mostly hangs out

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Speaker 1: in galaxies. Like you don't see a lot of dark

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Speaker 1: matter floating out there on its own between galaxies.

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Speaker 2: Yeah, we can do really precise measurements of where dark

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Speaker 2: matter is on the galaxy scale, because galaxies are really

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Speaker 2: really big. If you can tell how galaxies are orbiting

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Speaker 2: around each other, just the way we can tell how

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Speaker 2: stars are moving through the galaxy, so enormous clumps of

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Speaker 2: dark matter, absolutely we can measure their gravity. But when

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Speaker 2: you zoom in in a really fine grained way and

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Speaker 2: want to say, hey, is there a moon sized blob

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Speaker 2: of dark matter anywhere in our solar system. That's a

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Speaker 2: tough question to answer.

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Speaker 1: So then within the galaxy, you're saying, like, there's a

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Speaker 1: lot of dark matter within our galaxy. Ninety five percent

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Speaker 1: of the mass of our galaxy is dark matter. And

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Speaker 1: what does it look like. Does it look like, you know,

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Speaker 1: an intense, dense ball of dark matter in the middle.

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Speaker 1: Is it evenly distributed? And also like our galaxy looks

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Speaker 1: like a disc, sort of like a flat disk. Is

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Speaker 1: dark matter also shaped like a flat disk?

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Speaker 2: So we have the best answers the more we zoom out,

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Speaker 2: and then as we zoom in, things get literally fuzzy.

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Speaker 2: But on the scale of the galaxy, we have some ideas.

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Speaker 2: We think that dark matter is like a big halo.

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Speaker 2: So imagine the visible galaxy right at the edge of

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Speaker 2: the stars. Dark matter is a big halo that goes

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Speaker 2: out beyond the visible stars, and it's bigger and fuzzier.

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Speaker 2: It hasn't collapsed the way normal matter has because it

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Speaker 2: just doesn't clump right. In order to clump, things need

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Speaker 2: other kinds of interaction other than gravity. Like if you

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Speaker 2: have two dark matter particles, they attract each other gravitationally

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Speaker 2: and then just pass right through each other. They're just

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Speaker 2: gonna zig and zag back and forth, oscillate forever. They're

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Speaker 2: not going to clump together. To do that. You need

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Speaker 2: like electromagnetism or the strong force or something that wants

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Speaker 2: to grab onto each other. So dark matter stays a

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Speaker 2: big puffy halo, and the galaxy is sort of embedded

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Speaker 2: in that halo. And that's not a coincidence. Right. The

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Speaker 2: reason the galaxy exists is because of a big dark

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Speaker 2: matter blob there that's gathered together all the hydrogen helium

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Speaker 2: gravitationally and may it into a galaxy. It's the reason

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Speaker 2: we have stars, et cetera.

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Speaker 1: Now, when you say like halo, you don't actually mean

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Speaker 1: like an angel's halo that looks like a ring. You

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Speaker 1: actually mean just like a blob, right.

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Speaker 2: Yeah, exactly, like a big fuzzy blob that extends out

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Speaker 2: further along the disc and then further above and below

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Speaker 2: the disc. But even that we know already is not

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Speaker 2: evenly distributed.

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Speaker 1: Is it like football shaped? Is it you? Is it

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Speaker 1: kind of flat or is it a perfect sphere?

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Speaker 2: It's more like a hockey puck, right, It's flat, but

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Speaker 2: not as flat as the galaxy. Itself.

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Speaker 1: What made it flat?

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Speaker 2: Yeah, maybe a hockey puck is the wrong analogy. It's

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Speaker 2: not quite that flat. It's more like a big ellipsoid.

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Speaker 1: You mean like a slightly squished ball.

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Speaker 2: Yeah, exactly, It's like a big basketball that somebody's sitting

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Speaker 2: on or something.

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Speaker 1: All right, Well, let's get a little bit more into

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Speaker 1: the details of what we know about dark matter. How

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Speaker 1: much of it can we see? How much can we

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Speaker 1: discern about what it's doing in our universe? And we'll

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Speaker 1: answer the question of whether you can use a quantum

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Speaker 1: clock from Amazon dot com to detect it. So we'll

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Speaker 1: get to those questions, but first's take at a quick break.

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Speaker 1: All right, we're asking the question can you use quantum

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Speaker 1: clocks to detect dark matter? And we've been recapping a

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Speaker 1: little bit about what we know about dark matter, Daniel.

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00:21:25,320 --> 00:21:27,560
Speaker 1: How much of the details of it can we see?

440
00:21:27,720 --> 00:21:31,160
Speaker 2: Not really very much. We have this sense of a big,

441
00:21:31,280 --> 00:21:35,960
Speaker 2: fuzzy halo that surrounds the galaxy, and we can also

442
00:21:36,080 --> 00:21:39,280
Speaker 2: measure the density as a function of distance from the center.

443
00:21:39,440 --> 00:21:41,879
Speaker 2: So if you're a star, for example, orbiting the center

444
00:21:41,880 --> 00:21:45,200
Speaker 2: of the galaxy, the speed at which you orbit depends

445
00:21:45,320 --> 00:21:48,680
Speaker 2: on the force that's holding you in that orbit. So

446
00:21:48,680 --> 00:21:51,760
Speaker 2: the stronger the force, the faster you can go, or

447
00:21:51,800 --> 00:21:53,560
Speaker 2: the faster you can go, the stronger the force that's

448
00:21:53,680 --> 00:21:56,320
Speaker 2: needed to hold you in that orbit. So by measuring

449
00:21:56,320 --> 00:21:59,200
Speaker 2: the speed of a given star, we can essentially measure

450
00:21:59,240 --> 00:22:01,600
Speaker 2: the mass of all all that stuff that's holding on

451
00:22:01,760 --> 00:22:03,679
Speaker 2: to that star. So then if you look at stars

452
00:22:03,680 --> 00:22:07,040
Speaker 2: at different distances from the center, you can basically map

453
00:22:07,119 --> 00:22:10,199
Speaker 2: out the density of stuff in the galaxy as you

454
00:22:10,280 --> 00:22:13,159
Speaker 2: go further and closer to the center of the galaxy.

455
00:22:13,480 --> 00:22:16,440
Speaker 1: Like if dark matter was super condensed in the middle

456
00:22:16,440 --> 00:22:19,520
Speaker 1: of the galaxy, then the stars in the galaxy would

457
00:22:19,520 --> 00:22:22,480
Speaker 1: be rotating a certain way. Or if the dark matter

458
00:22:22,560 --> 00:22:25,119
Speaker 1: was more spread out, then the stars in the galaxy

459
00:22:25,160 --> 00:22:26,840
Speaker 1: would be rotating in a different way.

460
00:22:27,000 --> 00:22:29,800
Speaker 2: Yeah, exactly, if all the dark matter in the galaxy

461
00:22:29,920 --> 00:22:32,119
Speaker 2: was at the center, then everything would act in a

462
00:22:32,119 --> 00:22:34,080
Speaker 2: certain way, would just go like one over are squared.

463
00:22:34,080 --> 00:22:35,960
Speaker 2: It's sort of like the way the Solar system orbits

464
00:22:36,000 --> 00:22:38,040
Speaker 2: the Sun. But if you take some of that mass

465
00:22:38,040 --> 00:22:40,840
Speaker 2: and you spread it out through the galaxy instead, then

466
00:22:40,880 --> 00:22:43,240
Speaker 2: the dark matter that's further out than a given star

467
00:22:43,320 --> 00:22:46,520
Speaker 2: doesn't affect its orbit because its gravity all cancels out,

468
00:22:46,760 --> 00:22:49,960
Speaker 2: so that changes the rotation speed of those stars. And

469
00:22:49,960 --> 00:22:52,879
Speaker 2: that's in fact how we first discover dark matter was

470
00:22:52,880 --> 00:22:55,679
Speaker 2: by looking at these rotation speeds of stars around the

471
00:22:55,680 --> 00:22:58,400
Speaker 2: center of the galaxy and seeing that we couldn't explain

472
00:22:58,440 --> 00:23:00,720
Speaker 2: it by mapping all the mass from the stars and

473
00:23:00,760 --> 00:23:02,600
Speaker 2: the gas and the dust. And that's exactly how you

474
00:23:02,640 --> 00:23:05,199
Speaker 2: can tell where you need to add more mass to

475
00:23:05,280 --> 00:23:08,040
Speaker 2: explain these rotation speeds. It's not just like, hey, add

476
00:23:08,040 --> 00:23:09,920
Speaker 2: a big blob at the center. You need to add

477
00:23:09,920 --> 00:23:12,000
Speaker 2: some of the center and also some further out and

478
00:23:12,080 --> 00:23:15,800
Speaker 2: some further out, and so precise measurements of those velocities

479
00:23:15,960 --> 00:23:18,240
Speaker 2: give you a fairly accurate picture of where the dark

480
00:23:18,280 --> 00:23:21,200
Speaker 2: matter is in the galaxy. And it's not evenly spread out.

481
00:23:21,400 --> 00:23:24,280
Speaker 2: It's more densely clumped at the center, which is something you'd.

482
00:23:24,119 --> 00:23:27,560
Speaker 1: Expect because it is affected by gravity, right, It.

483
00:23:27,480 --> 00:23:29,800
Speaker 2: Is, in the end affected by gravity, and so it's

484
00:23:29,840 --> 00:23:33,320
Speaker 2: pulled itself together. And the whole reason that this exists

485
00:23:33,880 --> 00:23:37,600
Speaker 2: is because of some like early universe perturbation where you

486
00:23:37,640 --> 00:23:40,600
Speaker 2: had a denser blob of dark matter that created this

487
00:23:40,640 --> 00:23:43,719
Speaker 2: whole well gathered together the other dark matter and created

488
00:23:43,720 --> 00:23:46,440
Speaker 2: this over density which then pulled in hydrogen, helium and

489
00:23:46,480 --> 00:23:49,600
Speaker 2: whatever was around to make a galaxy. So it's a

490
00:23:49,600 --> 00:23:52,080
Speaker 2: little bit denser at the center. Though it's not very

491
00:23:52,080 --> 00:23:56,240
Speaker 2: well understood, like if we do calculations simulations to describe

492
00:23:56,359 --> 00:23:58,440
Speaker 2: what we think should happen. If you have a bunch

493
00:23:58,480 --> 00:24:00,359
Speaker 2: of dark matter and you'll give it a few billion

494
00:24:00,440 --> 00:24:02,960
Speaker 2: years to fall together and to form some structure. It

495
00:24:03,000 --> 00:24:06,280
Speaker 2: describes what astronomers call a cusp, which means like a

496
00:24:06,320 --> 00:24:08,320
Speaker 2: point of high density of the center and then very

497
00:24:08,359 --> 00:24:10,840
Speaker 2: steeply falling, should like drop off quickly. But if you

498
00:24:10,840 --> 00:24:14,680
Speaker 2: go out and measure the actual distributions of stars velocities,

499
00:24:15,000 --> 00:24:17,360
Speaker 2: you see something that looks like a bigger core. It's

500
00:24:17,400 --> 00:24:20,080
Speaker 2: not like it's pointing near the center. It's more spread

501
00:24:20,119 --> 00:24:23,679
Speaker 2: out in the inner galaxy. It's like flatter, and so

502
00:24:23,800 --> 00:24:25,800
Speaker 2: this is not something we understand very well. And it

503
00:24:25,840 --> 00:24:27,840
Speaker 2: also gives you a sense of like the scale of

504
00:24:27,880 --> 00:24:30,000
Speaker 2: which we can figure this stuff out. We're talking about

505
00:24:30,000 --> 00:24:33,080
Speaker 2: over light years distances, right, we're not resolving dark matter

506
00:24:33,119 --> 00:24:37,280
Speaker 2: in meters or even in aus with very very coarse

507
00:24:37,359 --> 00:24:40,200
Speaker 2: ways to measure where the dark matter is. Again, because

508
00:24:40,200 --> 00:24:41,720
Speaker 2: its gravity is so weak.

509
00:24:41,520 --> 00:24:44,080
Speaker 1: Are you saying, like the beginning of the universe, dark

510
00:24:44,080 --> 00:24:46,840
Speaker 1: matter was more evenly spread out, Like you know, all

511
00:24:46,840 --> 00:24:49,640
Speaker 1: those light years of empty space between us and Andromeda

512
00:24:49,680 --> 00:24:52,159
Speaker 1: and other galaxies was all filled with dark matter, and

513
00:24:52,160 --> 00:24:54,639
Speaker 1: then it all collapsed into certain clusters.

514
00:24:54,800 --> 00:24:57,639
Speaker 2: Yeah, it definitely gathered itself together. The early universe had

515
00:24:57,680 --> 00:25:01,400
Speaker 2: initial density fluctuations, and that's a whole big question about

516
00:25:01,440 --> 00:25:05,000
Speaker 2: where exactly that came from. And then those seated gravity

517
00:25:05,040 --> 00:25:08,439
Speaker 2: to pull things together. So gravity does form structure, but

518
00:25:08,520 --> 00:25:11,040
Speaker 2: it takes time. And so yeah, dark matter was more

519
00:25:11,080 --> 00:25:13,000
Speaker 2: spread out and now it's less spread out.

520
00:25:13,040 --> 00:25:14,960
Speaker 1: Why would dark matter stay stuck together?

521
00:25:15,160 --> 00:25:17,520
Speaker 2: Well, it's not that dark matter is sticking together. It's

522
00:25:17,520 --> 00:25:19,560
Speaker 2: not like it's bonded to itself. And again we don't

523
00:25:19,560 --> 00:25:22,119
Speaker 2: really know because we don't have a microscopic picture of

524
00:25:22,240 --> 00:25:24,920
Speaker 2: the dark matter. But I think you're asking, like why

525
00:25:24,920 --> 00:25:27,959
Speaker 2: does dark matter form even gravitational structures? Like why does

526
00:25:28,000 --> 00:25:30,520
Speaker 2: it get more dense in some places and then in others?

527
00:25:30,560 --> 00:25:31,359
Speaker 2: Is that what you're asking?

528
00:25:31,560 --> 00:25:33,679
Speaker 1: Yeah, Like I'm imagining at the beginning of the universe

529
00:25:33,680 --> 00:25:36,480
Speaker 1: there's a bit of dark matter that was you know,

530
00:25:36,640 --> 00:25:38,720
Speaker 1: let's say ten light years away, and then it got

531
00:25:38,720 --> 00:25:41,800
Speaker 1: attracted to our galaxy, so it flew over here. But

532
00:25:41,920 --> 00:25:44,280
Speaker 1: then why didn't it just keep flying to the other side.

533
00:25:44,440 --> 00:25:46,880
Speaker 2: Yeah, so as that distant piece of dark matter approaches

534
00:25:46,920 --> 00:25:51,120
Speaker 2: the galaxy, it gains velocity. Right, it's exchanging gravitational potential

535
00:25:51,200 --> 00:25:54,159
Speaker 2: energy for kinetic energy. And then you're imagining, like the

536
00:25:54,200 --> 00:25:56,080
Speaker 2: way a ball rolls down a valley, why doesn't it

537
00:25:56,160 --> 00:25:58,880
Speaker 2: roll back up the other side? And it will, yes,

538
00:25:58,920 --> 00:26:01,840
Speaker 2: but then it comes back right, And so gravity in

539
00:26:01,880 --> 00:26:05,399
Speaker 2: the end is organizing something. There's the second piece to that,

540
00:26:05,480 --> 00:26:08,680
Speaker 2: which is that it doesn't completely grow back up the

541
00:26:08,720 --> 00:26:12,520
Speaker 2: other side. You know, anything that's accelerating is emitting gravitational

542
00:26:12,640 --> 00:26:16,040
Speaker 2: radiation for example. So the reason, for example, two black

543
00:26:16,080 --> 00:26:19,720
Speaker 2: holes orbiting each other will eventually spiral in and collapse

544
00:26:20,080 --> 00:26:23,040
Speaker 2: is that they're emitting gravitational energy. So none of these

545
00:26:23,040 --> 00:26:25,960
Speaker 2: things are really stable. So over long periods of time,

546
00:26:26,200 --> 00:26:30,359
Speaker 2: even without inelastic interactions like electromagnetism or whatever, these things

547
00:26:30,400 --> 00:26:34,760
Speaker 2: will form very large structures and they will gradually collapse

548
00:26:34,840 --> 00:26:36,240
Speaker 2: due to gravitational radiation.

549
00:26:36,600 --> 00:26:38,879
Speaker 1: All right, so we kind of have a fuzzy picture

550
00:26:38,920 --> 00:26:41,520
Speaker 1: of where it is in the universe. So now the

551
00:26:41,600 --> 00:26:44,360
Speaker 1: question of the episode is can we use quantum clocks

552
00:26:44,680 --> 00:26:48,080
Speaker 1: to detect dark matter? How do quantum clocks fit into this?

553
00:26:48,359 --> 00:26:51,000
Speaker 2: So quantum clocks might give us a sense for where

554
00:26:51,000 --> 00:26:53,639
Speaker 2: the dark matter is if we can find a place

555
00:26:53,680 --> 00:26:56,399
Speaker 2: where it's like clumpy, if we can find a place

556
00:26:56,560 --> 00:26:59,720
Speaker 2: in our solar system where it's like gathered together for

557
00:26:59,800 --> 00:27:02,520
Speaker 2: some reason. And that would be really cool because not

558
00:27:02,560 --> 00:27:05,040
Speaker 2: only would it help us detect what dark matter is,

559
00:27:05,240 --> 00:27:07,919
Speaker 2: but it would help us understand where it is. It's

560
00:27:07,960 --> 00:27:09,960
Speaker 2: a really deep mystery, I think, not just because we

561
00:27:10,040 --> 00:27:12,000
Speaker 2: want to understand dark matter, but because we want like

562
00:27:12,040 --> 00:27:15,080
Speaker 2: a map. You know, humans are visual creatures. We want

563
00:27:15,080 --> 00:27:17,159
Speaker 2: to know like where the stuff is, and just not

564
00:27:17,400 --> 00:27:20,679
Speaker 2: knowing where dark matter is in the universe really bugs me.

565
00:27:20,760 --> 00:27:22,800
Speaker 2: So I would love to know where it is and

566
00:27:23,280 --> 00:27:26,959
Speaker 2: understanding its map on a finer scale would be really helpful.

567
00:27:27,000 --> 00:27:29,520
Speaker 2: And quantum clocks might be able to help us map

568
00:27:29,680 --> 00:27:31,840
Speaker 2: where dark matter is if we can send them out

569
00:27:31,920 --> 00:27:35,720
Speaker 2: into space and if they're sensitive to dark matter, if

570
00:27:35,720 --> 00:27:38,760
Speaker 2: their operation changes as they pass through dark matter.

571
00:27:38,840 --> 00:27:40,359
Speaker 1: Okay, I think you're saying that you know, at the

572
00:27:40,359 --> 00:27:43,359
Speaker 1: galaxy level, we know that it looks like a big blob.

573
00:27:43,400 --> 00:27:45,879
Speaker 1: It's sort of like a switchball. It's sort of more

574
00:27:45,920 --> 00:27:48,200
Speaker 1: intense or more dense in the center of the galaxy.

575
00:27:48,400 --> 00:27:50,520
Speaker 1: But I think maybe you're saying, can we know in

576
00:27:50,600 --> 00:27:55,400
Speaker 1: finer detail what it looks like between stars within the galaxy,

577
00:27:55,520 --> 00:27:58,240
Speaker 1: like is it clumpy, is it chunky, or is it

578
00:27:58,280 --> 00:28:01,000
Speaker 1: like peanut butter or smooth exactly?

579
00:28:01,119 --> 00:28:03,840
Speaker 2: And people have tackled this problem in the past, Like

580
00:28:04,000 --> 00:28:06,920
Speaker 2: people use the technique you mentioned gravitation lensing to look

581
00:28:06,960 --> 00:28:10,320
Speaker 2: for blobs of dark matter, and that works and it's powerful,

582
00:28:10,480 --> 00:28:13,480
Speaker 2: but only if you have like a really nice galaxy

583
00:28:13,720 --> 00:28:16,320
Speaker 2: behind the blob of dark matter that can show you

584
00:28:16,400 --> 00:28:18,520
Speaker 2: that it's there, So that tells us a little bit

585
00:28:18,520 --> 00:28:20,960
Speaker 2: about the dark matter density. But there aren't like galaxies

586
00:28:21,000 --> 00:28:22,960
Speaker 2: in all the right places to like X ray the

587
00:28:23,000 --> 00:28:25,159
Speaker 2: whole Solar system and figure out where it is, And

588
00:28:25,160 --> 00:28:27,199
Speaker 2: that technique isn't always powerful enough. You need like a

589
00:28:27,200 --> 00:28:29,919
Speaker 2: really big blob of dark matter. Another technique people have

590
00:28:30,040 --> 00:28:33,600
Speaker 2: used is to look for dwarf galaxies. Essentially, our galaxy

591
00:28:33,680 --> 00:28:36,640
Speaker 2: is formed by the combination of lots of galaxies, right,

592
00:28:36,840 --> 00:28:39,240
Speaker 2: we think galaxies formed kind of small and then grew

593
00:28:39,280 --> 00:28:42,600
Speaker 2: together with all sorts of absorptions and collisions. That means

594
00:28:42,600 --> 00:28:46,360
Speaker 2: that our galaxy has other, like many galaxies embedded within it.

595
00:28:46,760 --> 00:28:49,400
Speaker 2: Some of these we call dwarf galaxies because they're small

596
00:28:49,600 --> 00:28:52,440
Speaker 2: and we think they're like very high dark matter density.

597
00:28:52,480 --> 00:28:55,480
Speaker 2: They're very few stars, and so we can look at

598
00:28:55,480 --> 00:28:58,000
Speaker 2: the motion of the stars inside those little galaxies to

599
00:28:58,040 --> 00:29:00,760
Speaker 2: get sensors for like where those blobs are. But we

600
00:29:00,800 --> 00:29:02,800
Speaker 2: don't have a great way to like X ray the

601
00:29:02,840 --> 00:29:05,360
Speaker 2: Solar System and figure out like where is the dark

602
00:29:05,360 --> 00:29:07,959
Speaker 2: matter in our Solar system? Is it hanging out by Jupiter?

603
00:29:08,240 --> 00:29:11,080
Speaker 2: Is it spread evenly like peanut butter? What's going on?

604
00:29:11,560 --> 00:29:14,160
Speaker 1: You want to know it's distribution at the Solar system

605
00:29:14,200 --> 00:29:15,000
Speaker 1: scale exactly.

606
00:29:15,040 --> 00:29:16,680
Speaker 2: That's what I want to do. And I read a

607
00:29:16,680 --> 00:29:19,320
Speaker 2: recent paper which was very clever, which is looking at

608
00:29:19,360 --> 00:29:22,600
Speaker 2: asteroids and trying to track asteroid trajectories and see if

609
00:29:22,640 --> 00:29:26,200
Speaker 2: like tiny little deviations in the trajectory of asteroids or

610
00:29:26,200 --> 00:29:29,520
Speaker 2: comets as they move through the Solar System could reveal

611
00:29:29,600 --> 00:29:32,040
Speaker 2: the presence of dark matter. It's very difficult to do

612
00:29:32,080 --> 00:29:34,720
Speaker 2: because if dark matter is evenly spread out or only

613
00:29:34,720 --> 00:29:37,600
Speaker 2: a little bit clumpy, that be basically no effect on

614
00:29:37,720 --> 00:29:40,160
Speaker 2: those asteroids. But it's the kind of thing that we're

615
00:29:40,200 --> 00:29:42,440
Speaker 2: just on the verge of being able to potentially do

616
00:29:42,560 --> 00:29:45,760
Speaker 2: now that we have better measurements and better computational tools

617
00:29:45,800 --> 00:29:49,720
Speaker 2: to try to like infer this information from really specific measurements.

618
00:29:49,760 --> 00:29:51,840
Speaker 1: All right, So then how would you use a quantum

619
00:29:51,880 --> 00:29:53,560
Speaker 1: clock to de teg dark matter?

620
00:29:53,680 --> 00:29:55,880
Speaker 2: So when we talk about a quantum clock, really what

621
00:29:55,880 --> 00:29:59,040
Speaker 2: we mean is something which is based on fundamental quantum

622
00:29:59,080 --> 00:30:01,800
Speaker 2: mechanical principles. And you know, it sounds fancy, but even

623
00:30:01,840 --> 00:30:04,880
Speaker 2: just like an atomic clock is a quantum clock. An

624
00:30:04,880 --> 00:30:07,520
Speaker 2: atomic clock is something that looks at like the oscillation

625
00:30:07,600 --> 00:30:10,560
Speaker 2: of electron between two energy levels and a caesium atom,

626
00:30:10,840 --> 00:30:14,920
Speaker 2: which is a very precise, very very regular process that

627
00:30:15,000 --> 00:30:18,240
Speaker 2: we can use essentially to tell how time has passed.

628
00:30:18,840 --> 00:30:22,360
Speaker 2: And so on Earth, we have extraordinarily precise atomic clocks

629
00:30:22,400 --> 00:30:25,040
Speaker 2: which now set the standard and in fact define what

630
00:30:25,080 --> 00:30:27,240
Speaker 2: we mean by a second. A second used to have

631
00:30:27,280 --> 00:30:30,040
Speaker 2: a different definition, but now a second is defined as

632
00:30:30,120 --> 00:30:32,840
Speaker 2: like a certain number of cycles of a specific kind

633
00:30:32,880 --> 00:30:37,280
Speaker 2: of atom. That's literally how we measure time now, and

634
00:30:37,320 --> 00:30:38,680
Speaker 2: so it's the standard.

635
00:30:39,040 --> 00:30:41,040
Speaker 1: But it's like the minute, like it used to be

636
00:30:41,120 --> 00:30:43,680
Speaker 1: like a minute with sixty seconds, but now people say, oh,

637
00:30:43,720 --> 00:30:46,640
Speaker 1: it's been a minute to really mean something totally different.

638
00:30:50,600 --> 00:30:55,400
Speaker 2: Yes, it's just like that exactly. And we call it

639
00:30:55,440 --> 00:30:58,160
Speaker 2: a quantum clock because this really is a quantum process.

640
00:30:58,200 --> 00:31:01,479
Speaker 2: We're talking about quantum particles, an electron, there's an atom.

641
00:31:01,680 --> 00:31:04,680
Speaker 2: The electron is moving in the potential well of the atom,

642
00:31:04,800 --> 00:31:08,120
Speaker 2: so it's interacting electromagnetically with the nucleus, and the way

643
00:31:08,200 --> 00:31:10,760
Speaker 2: that it's moving, the way it oscillates between energy levels,

644
00:31:11,000 --> 00:31:14,160
Speaker 2: is completely controlled by quantum processes. This is not a

645
00:31:14,200 --> 00:31:16,760
Speaker 2: clock that you could have in a perfectly classical universe.

646
00:31:17,000 --> 00:31:19,360
Speaker 2: You know, if we lived in a universe where electrons

647
00:31:19,400 --> 00:31:21,880
Speaker 2: really were tiny little balls that went to orbits and

648
00:31:21,880 --> 00:31:25,000
Speaker 2: had smooth classical paths the way planets do, then this

649
00:31:25,080 --> 00:31:27,760
Speaker 2: clock could not exist. And so that's when we meet

650
00:31:27,800 --> 00:31:28,880
Speaker 2: by quantum clock.

651
00:31:29,120 --> 00:31:31,239
Speaker 1: But I guess, if it's a quantum clock, doesn't it

652
00:31:31,280 --> 00:31:34,640
Speaker 1: have a certain amount of uncertainty to it or unknowability?

653
00:31:34,880 --> 00:31:38,360
Speaker 1: How can it be precise? If there's the Heisenberg uncertainty principle.

654
00:31:39,640 --> 00:31:42,960
Speaker 2: Yeah, you're right, there's no absolutely precise quantum clock. But

655
00:31:43,160 --> 00:31:45,600
Speaker 2: this is about as regular as it gets. And amazingly,

656
00:31:45,680 --> 00:31:49,200
Speaker 2: these quantum clocks are more precise than mechanical clocks, which

657
00:31:49,200 --> 00:31:51,960
Speaker 2: of course also have uncertainty in them, because no mechanical

658
00:31:52,000 --> 00:31:55,120
Speaker 2: device is perfectly created, right, And so this is as

659
00:31:55,160 --> 00:31:57,520
Speaker 2: accurate as they've been able to make them, and recently

660
00:31:57,600 --> 00:32:01,000
Speaker 2: they've been even able to make them small and transportable.

661
00:32:01,240 --> 00:32:03,400
Speaker 2: You might think of an atomic clock as like some

662
00:32:03,560 --> 00:32:06,880
Speaker 2: huge device in the basement of a laboratory in Colorado

663
00:32:07,160 --> 00:32:09,600
Speaker 2: that weighs like ten tons and fills a room. But

664
00:32:09,680 --> 00:32:11,920
Speaker 2: actually these things can be made quite small.

665
00:32:12,200 --> 00:32:14,760
Speaker 1: So a quantum clock is really just an atomic clock,

666
00:32:14,880 --> 00:32:17,280
Speaker 1: or is there another kind that doesn't use atoms?

667
00:32:17,320 --> 00:32:19,560
Speaker 2: There's no atomic clock that's not a quantum clock. So

668
00:32:19,640 --> 00:32:22,360
Speaker 2: quantum clock is just a fancier sounding name for atomic clock.

669
00:32:22,440 --> 00:32:24,880
Speaker 1: Yes, can you have a quantum clock that maybe doesn't

670
00:32:24,960 --> 00:32:27,840
Speaker 1: use an atom, that maybe just relies on electrons or

671
00:32:28,000 --> 00:32:28,880
Speaker 1: quarks or something.

672
00:32:29,040 --> 00:32:31,920
Speaker 2: Yeah, sure, you're not limited to atoms. You can imagine

673
00:32:32,000 --> 00:32:35,320
Speaker 2: quantum clocks made out of like photons interacting or splitting

674
00:32:35,440 --> 00:32:38,800
Speaker 2: or bouncing or something like that. In some sense, lego

675
00:32:39,080 --> 00:32:42,400
Speaker 2: is a clock because it's measuring the time for photons

676
00:32:42,440 --> 00:32:45,760
Speaker 2: to travel along its legs, right, It's just converting that

677
00:32:45,800 --> 00:32:48,520
Speaker 2: to a distance measurement, and so you could have other

678
00:32:48,600 --> 00:32:51,040
Speaker 2: quantum clocks that are not based on atoms. Yes, And

679
00:32:51,120 --> 00:32:53,200
Speaker 2: one day, when we discover dark matter, maybe we could

680
00:32:53,200 --> 00:32:54,240
Speaker 2: build a clock.

681
00:32:53,960 --> 00:32:56,880
Speaker 1: Out of dark matter, which may or may not tell

682
00:32:56,920 --> 00:32:57,600
Speaker 1: you the time.

683
00:32:58,200 --> 00:32:59,960
Speaker 2: And may or may not smell like flatulin.

684
00:33:00,360 --> 00:33:02,040
Speaker 1: Well, I guess, maybe give us an example of like,

685
00:33:02,120 --> 00:33:05,880
Speaker 1: what's a typical or popular or a commonly used quantum

686
00:33:05,880 --> 00:33:06,960
Speaker 1: clock and how does it work.

687
00:33:07,240 --> 00:33:10,000
Speaker 2: Well, the most precise quantum clock is based on the

688
00:33:10,000 --> 00:33:13,120
Speaker 2: caesium one thirty three atom. That's the one that's actually

689
00:33:13,200 --> 00:33:16,440
Speaker 2: used to define what a second is. And so here

690
00:33:16,480 --> 00:33:19,480
Speaker 2: we have two states of electrons. There's a small splitting

691
00:33:19,520 --> 00:33:22,200
Speaker 2: in an energy state here. It's called a hyper fine

692
00:33:22,240 --> 00:33:24,920
Speaker 2: splitting because the difference is very very small, and when

693
00:33:24,920 --> 00:33:26,760
Speaker 2: the electron sits in there, it sort of goes back

694
00:33:26,800 --> 00:33:28,959
Speaker 2: and forth between the two different states.

695
00:33:29,200 --> 00:33:32,480
Speaker 1: Meaning like, this is an electron that's orbiting around the

696
00:33:32,520 --> 00:33:33,320
Speaker 1: caesium atom.

697
00:33:33,560 --> 00:33:35,600
Speaker 2: Yeah, I wouldn't say orbiting if we want to be

698
00:33:35,640 --> 00:33:38,440
Speaker 2: really really technical. But it's captured by the caesium atom.

699
00:33:38,640 --> 00:33:40,880
Speaker 1: And you're saying it's switching energy levels. Why would it

700
00:33:40,920 --> 00:33:41,960
Speaker 1: switch energy levels?

701
00:33:42,160 --> 00:33:44,360
Speaker 2: So you have this caesium atom and you embed the

702
00:33:44,360 --> 00:33:46,920
Speaker 2: whole thing in some microwave radiation that can lift those

703
00:33:46,920 --> 00:33:49,800
Speaker 2: electrons up from the lower state to the higher state.

704
00:33:50,000 --> 00:33:52,000
Speaker 1: Meaning you like put it in a microwave or you

705
00:33:52,040 --> 00:33:53,640
Speaker 1: shoot it with this like a light gun.

706
00:33:54,600 --> 00:33:56,880
Speaker 2: There's not a difference, right, that's what a microwave is.

707
00:33:56,920 --> 00:34:00,120
Speaker 2: A microwave is shooting microwave radiation at your food, and

708
00:34:00,160 --> 00:34:03,720
Speaker 2: microwaves are lights. Though basically a microwave is a light gun.

709
00:34:03,960 --> 00:34:06,320
Speaker 1: Sounds hot. So then you have this atom and you

710
00:34:06,320 --> 00:34:07,360
Speaker 1: you stick it in the microwave.

711
00:34:07,400 --> 00:34:09,719
Speaker 2: Uh huh, yeah, So you stick in the microwave and

712
00:34:09,760 --> 00:34:11,959
Speaker 2: you measure how often it jumps up and then down

713
00:34:12,000 --> 00:34:13,320
Speaker 2: and then up and then down.

714
00:34:13,320 --> 00:34:16,160
Speaker 1: Because the light, as the light passes through it, it

715
00:34:16,400 --> 00:34:18,400
Speaker 1: knocks the electron up and down or what.

716
00:34:18,640 --> 00:34:21,400
Speaker 2: Yeah, the light is tuned to exactly the frequency for

717
00:34:21,440 --> 00:34:24,720
Speaker 2: the electron to jump up into the higher energy level. Remember,

718
00:34:24,800 --> 00:34:27,000
Speaker 2: electrons can go from a lower to a higher energy

719
00:34:27,040 --> 00:34:29,600
Speaker 2: level if a photon of the right energy comes along.

720
00:34:29,960 --> 00:34:33,400
Speaker 2: So they've tuned this microwave to exactly that energy level.

721
00:34:33,600 --> 00:34:36,400
Speaker 2: So electrons and the lower level can absorb these photons

722
00:34:36,440 --> 00:34:38,720
Speaker 2: jump up to the higher level, but then they'll naturally

723
00:34:38,719 --> 00:34:42,160
Speaker 2: decay down because the universe likes to spread energy out,

724
00:34:42,400 --> 00:34:44,960
Speaker 2: and so the time of these oscillations turns out to

725
00:34:45,000 --> 00:34:48,080
Speaker 2: be very very regular, Like an electron will do this

726
00:34:48,280 --> 00:34:52,239
Speaker 2: nine point one nine to two billion times per second.

727
00:34:52,080 --> 00:34:54,399
Speaker 1: And it doesn't depend on the frequency of the light,

728
00:34:54,560 --> 00:34:54,959
Speaker 1: or it does.

729
00:34:55,080 --> 00:34:57,000
Speaker 2: It definitely depends on the frequency of the light. If

730
00:34:57,000 --> 00:34:59,279
Speaker 2: the frequency of the light is not correct, then it

731
00:34:59,280 --> 00:35:01,120
Speaker 2: won't even abso, right, it won't happen.

732
00:35:01,400 --> 00:35:04,160
Speaker 1: Oh but then don't you need to make that frequency

733
00:35:04,280 --> 00:35:05,040
Speaker 1: super precise?

734
00:35:05,200 --> 00:35:07,680
Speaker 2: Yeah, exactly, And this is one source of uncertainty in

735
00:35:07,719 --> 00:35:11,080
Speaker 2: these clocks, right, making those accurate. And you can measure

736
00:35:11,080 --> 00:35:13,279
Speaker 2: these things, like you build two independent ones, you can

737
00:35:13,320 --> 00:35:16,319
Speaker 2: see how their counts drift relative to each other. And

738
00:35:16,760 --> 00:35:19,080
Speaker 2: that's how you measure the accuracy of clocks. In general.

739
00:35:19,120 --> 00:35:21,359
Speaker 2: There's no absolute standard by which you can tell like, oh,

740
00:35:21,360 --> 00:35:23,200
Speaker 2: this clock is off or that clock is off. You

741
00:35:23,320 --> 00:35:24,799
Speaker 2: just build a few of them and you measure them

742
00:35:24,840 --> 00:35:27,239
Speaker 2: relative to each other. And this is something that we

743
00:35:27,360 --> 00:35:29,719
Speaker 2: know well enough. We know how to design the middle

744
00:35:29,719 --> 00:35:32,160
Speaker 2: of the physics and the engineering that you can build

745
00:35:32,200 --> 00:35:36,200
Speaker 2: these things so that atomic clocks in independent locations agree

746
00:35:36,600 --> 00:35:39,640
Speaker 2: to like zero point three nanoseconds per day. It's really

747
00:35:39,760 --> 00:35:40,920
Speaker 2: very incredibly precise.

748
00:35:41,400 --> 00:35:44,080
Speaker 1: WHOA, so what are you measuring? How are you measuring

749
00:35:44,120 --> 00:35:46,080
Speaker 1: whether these electrons are going up and down?

750
00:35:46,120 --> 00:35:48,960
Speaker 2: When the electron goes back down, it emits radiation, right,

751
00:35:49,000 --> 00:35:50,560
Speaker 2: and so you can gather that as.

752
00:35:50,400 --> 00:35:53,080
Speaker 1: Well, like it shoots off light, like it will blink.

753
00:35:52,840 --> 00:35:54,880
Speaker 2: Basically exactly little flash.

754
00:35:55,000 --> 00:35:57,120
Speaker 1: All right. So then, and you're saying you can build

755
00:35:57,200 --> 00:35:59,560
Speaker 1: these things now to be the size of a toaster

756
00:35:59,840 --> 00:36:02,240
Speaker 1: or or a microwave oven.

757
00:36:02,800 --> 00:36:05,840
Speaker 2: A quantum toaster. They have them now and they've deployed

758
00:36:05,840 --> 00:36:08,560
Speaker 2: them out in space. They actually built the Deep Space

759
00:36:08,600 --> 00:36:11,439
Speaker 2: Atomic Clock Mission and they sent an atomic clock out

760
00:36:11,480 --> 00:36:13,879
Speaker 2: into space to see, like, hey, can we operate one

761
00:36:13,880 --> 00:36:16,120
Speaker 2: of these things out in space? And you might wonder

762
00:36:16,200 --> 00:36:18,400
Speaker 2: like is this just a bunch of nerds trying to

763
00:36:18,400 --> 00:36:20,080
Speaker 2: do something that seems cool?

764
00:36:20,360 --> 00:36:22,759
Speaker 1: Yes? Is always the answer, Like can we shoot a

765
00:36:22,800 --> 00:36:26,480
Speaker 1: microwave into space and will it still heat up my burrito?

766
00:36:26,600 --> 00:36:29,000
Speaker 1: My seizing Burritoah? Is that the challenge?

767
00:36:29,040 --> 00:36:31,239
Speaker 2: That's the challenge. But also if we want to do

768
00:36:31,360 --> 00:36:35,160
Speaker 2: things like navigate in space, navigation needs timing. You need

769
00:36:35,200 --> 00:36:37,560
Speaker 2: to know like how long you're going in one direction.

770
00:36:37,760 --> 00:36:39,400
Speaker 2: If you want to do dead reckoning, you want to

771
00:36:39,400 --> 00:36:42,520
Speaker 2: know where you are. Timing is absolutely crucial. Or if

772
00:36:42,560 --> 00:36:46,240
Speaker 2: you want to use like nearby pulsars to triangulate your position,

773
00:36:46,520 --> 00:36:49,120
Speaker 2: my whole episode about how that works, you also need

774
00:36:49,280 --> 00:36:51,800
Speaker 2: very accurate timing so you can measure the time between

775
00:36:51,800 --> 00:36:54,680
Speaker 2: the pulses. So this was like a technological challenge that's

776
00:36:54,680 --> 00:36:57,879
Speaker 2: going to lay the groundwork for all sorts of cool innovations.

777
00:36:58,239 --> 00:37:01,440
Speaker 2: And this was totally successful, this deep space atomic clock mission.

778
00:37:01,640 --> 00:37:04,120
Speaker 1: Well, let's get into how you would actually use these

779
00:37:04,320 --> 00:37:07,840
Speaker 1: and how the timing might tell you where dark matter

780
00:37:07,960 --> 00:37:11,800
Speaker 1: is within our Solar system and maybe even within the Earth.

781
00:37:11,960 --> 00:37:14,360
Speaker 1: So let's dig into that. But first let's take another

782
00:37:14,440 --> 00:37:30,040
Speaker 1: quick break. All right, we're talking about using a microwave

783
00:37:30,160 --> 00:37:33,200
Speaker 1: stuck inside of a microwave to detect dark matter so

784
00:37:33,239 --> 00:37:36,440
Speaker 1: you can win a Tierra for being the prettiest scientist.

785
00:37:37,120 --> 00:37:39,560
Speaker 2: Yeah, exactly. Does it take longer to heat up your

786
00:37:39,560 --> 00:37:41,480
Speaker 2: burrito when there's dark matter around?

787
00:37:41,800 --> 00:37:44,200
Speaker 1: So the idea is that you take these atomic or

788
00:37:44,480 --> 00:37:47,120
Speaker 1: basically an atomic clock, which is a quantum clock, but

789
00:37:48,000 --> 00:37:50,840
Speaker 1: it seems like the most popular ones use atoms, and

790
00:37:50,920 --> 00:37:52,920
Speaker 1: so you shrink them down to the size of a

791
00:37:52,960 --> 00:37:54,920
Speaker 1: toaster or microwave and then you shoot them in space,

792
00:37:54,960 --> 00:37:57,080
Speaker 1: and then how does that help you measure dark matter?

793
00:37:57,840 --> 00:37:59,720
Speaker 2: Well, there were a bunch of physicists who thought, okay,

794
00:37:59,760 --> 00:38:02,000
Speaker 2: this is that's cool because now we not only have

795
00:38:02,280 --> 00:38:05,440
Speaker 2: all some super precise atomic clocks, but now we have

796
00:38:05,520 --> 00:38:08,000
Speaker 2: them spread out through the Solar System, like in principle

797
00:38:08,280 --> 00:38:10,160
Speaker 2: the way we like scent devices near the Sun with

798
00:38:10,200 --> 00:38:12,839
Speaker 2: a Parker solar probe. People are, what if we built

799
00:38:12,840 --> 00:38:14,719
Speaker 2: a bunch of these things and we spread them out

800
00:38:14,719 --> 00:38:17,040
Speaker 2: in the Solar system, could they give us a picture

801
00:38:17,080 --> 00:38:19,600
Speaker 2: of where the dark matter is in the Solar system

802
00:38:20,120 --> 00:38:23,400
Speaker 2: if they operate differently when there's dark matter around, like

803
00:38:23,440 --> 00:38:26,279
Speaker 2: if they're sensitive to the dark matter density, Like if

804
00:38:26,280 --> 00:38:29,680
Speaker 2: your atomic clock gets off if it drifts when there's

805
00:38:29,719 --> 00:38:32,360
Speaker 2: more or less dark matter around, than having a bunch

806
00:38:32,360 --> 00:38:35,120
Speaker 2: of these atomic clocks spread out through the Solar system

807
00:38:35,280 --> 00:38:37,440
Speaker 2: could give you a picture for where in the Solar

808
00:38:37,440 --> 00:38:38,759
Speaker 2: System the dark matter is.

809
00:38:39,400 --> 00:38:42,560
Speaker 1: But I guess what's the mechanism by which dark matter

810
00:38:42,600 --> 00:38:44,920
Speaker 1: would affect the timing of these clocks.

811
00:38:45,120 --> 00:38:47,960
Speaker 2: Yeah, so mostly it wouldn't. For many theories of dark matter,

812
00:38:48,080 --> 00:38:51,240
Speaker 2: dark matter is just some wimp. It's a massive particle

813
00:38:51,320 --> 00:38:54,480
Speaker 2: that only interacts gravitationally, and so it has essentially no

814
00:38:54,600 --> 00:38:58,360
Speaker 2: effect on these clocks except for gravitational time dilation. We

815
00:38:58,400 --> 00:39:01,279
Speaker 2: know the areas with greater mass more curvature, and a

816
00:39:01,360 --> 00:39:04,000
Speaker 2: curvature causes time dilation, but that would be very, very

817
00:39:04,040 --> 00:39:06,560
Speaker 2: difficult to measure even with these quantum clocks.

818
00:39:06,640 --> 00:39:08,200
Speaker 1: But wait, wait, why would it be difficult.

819
00:39:08,239 --> 00:39:11,239
Speaker 2: You can measure gravitational time dilation with quantum clocks, and

820
00:39:11,280 --> 00:39:13,400
Speaker 2: we've done that. You can do it on the surface

821
00:39:13,440 --> 00:39:15,360
Speaker 2: of the Earth, for example, and you could put a

822
00:39:15,400 --> 00:39:18,440
Speaker 2: quantum clock one meter above another one and you can

823
00:39:18,480 --> 00:39:21,080
Speaker 2: see the difference between them because one of them is

824
00:39:21,120 --> 00:39:24,240
Speaker 2: deeper in the curvature than the other. Super duper awesome,

825
00:39:24,480 --> 00:39:26,480
Speaker 2: but that's because the Earth has a huge amount of

826
00:39:26,520 --> 00:39:30,240
Speaker 2: gravity and this significant curvature. Here. Dark matter doesn't contribute

827
00:39:30,280 --> 00:39:34,000
Speaker 2: significantly to the curvature because it's pretty spread out, and

828
00:39:34,120 --> 00:39:36,960
Speaker 2: we would already know if dark matter wasn't pretty spread out,

829
00:39:37,120 --> 00:39:39,640
Speaker 2: because we would have seen deviations and like Jupiter's orbit

830
00:39:39,680 --> 00:39:42,399
Speaker 2: and whatever. So in principle you can, but we don't

831
00:39:42,400 --> 00:39:44,120
Speaker 2: think it's going to be very sensitive. If you had

832
00:39:44,120 --> 00:39:46,560
Speaker 2: a lot of quantum clocks and there were much more sensitive,

833
00:39:46,719 --> 00:39:50,239
Speaker 2: then you could probably detect dark matter local density variations

834
00:39:50,520 --> 00:39:51,000
Speaker 2: using that.

835
00:39:51,000 --> 00:39:54,640
Speaker 1: Principle, meaning these clocks would take at a different frequency

836
00:39:55,400 --> 00:39:58,799
Speaker 1: depending on how close it was to big sources of

837
00:39:58,880 --> 00:40:02,040
Speaker 1: mass or even sources of mass, because that's just how

838
00:40:02,120 --> 00:40:02,960
Speaker 1: relativity works.

839
00:40:03,080 --> 00:40:05,279
Speaker 2: Yeah, that's how relativity works. Remember, in relativity, it is

840
00:40:05,320 --> 00:40:08,200
Speaker 2: two kinds of time dilation. One is based on speed.

841
00:40:08,239 --> 00:40:10,680
Speaker 2: If you see a clock moving quickly, then you see

842
00:40:10,680 --> 00:40:14,120
Speaker 2: it ticking slowly, and that's very confusing because it's relative,

843
00:40:14,160 --> 00:40:16,560
Speaker 2: and so it depends on two observers. But there's another

844
00:40:16,680 --> 00:40:20,160
Speaker 2: kind of time dilation, gravitational, which is absolute. It just

845
00:40:20,160 --> 00:40:23,680
Speaker 2: says anybody in curvature their clock is going to tick slowly,

846
00:40:23,840 --> 00:40:25,759
Speaker 2: no matter who's looking at it, and everybody's going to

847
00:40:25,800 --> 00:40:29,280
Speaker 2: agree about whose clock is ticking slowly. So that's very powerful,

848
00:40:29,560 --> 00:40:32,080
Speaker 2: and that's something you can use to measure just like

849
00:40:32,160 --> 00:40:35,239
Speaker 2: how much stuff is there in general, because clocks tick

850
00:40:35,360 --> 00:40:38,360
Speaker 2: slower near stuff. Really kind of an awesome feature of

851
00:40:38,440 --> 00:40:39,560
Speaker 2: the universe.

852
00:40:39,239 --> 00:40:41,280
Speaker 1: Meaning like if I had two of these atomic clocks

853
00:40:41,280 --> 00:40:42,800
Speaker 1: and one of them is out there in the middle

854
00:40:42,840 --> 00:40:45,120
Speaker 1: of empty space, and the other one is near a

855
00:40:45,120 --> 00:40:47,319
Speaker 1: big blob of dark matter. The one near the blob

856
00:40:47,360 --> 00:40:50,480
Speaker 1: of dark matter would take slower.

857
00:40:50,160 --> 00:40:51,960
Speaker 2: Right, Yeah, that's exactly right.

858
00:40:52,000 --> 00:40:54,120
Speaker 1: And so you might like start them out in the

859
00:40:54,160 --> 00:40:57,840
Speaker 1: same spot. But then after being for a while and

860
00:40:57,880 --> 00:40:59,600
Speaker 1: two different spots, one near the dark matter, and you

861
00:40:59,719 --> 00:41:01,640
Speaker 1: run a back, you would see that one of them

862
00:41:02,000 --> 00:41:03,400
Speaker 1: take more ticks than the other.

863
00:41:03,640 --> 00:41:03,799
Speaker 3: Yeah.

864
00:41:03,920 --> 00:41:06,640
Speaker 2: So now imagine like a grid, you have a quantum

865
00:41:06,719 --> 00:41:09,799
Speaker 2: clock every ten meters in the solar system, right, you

866
00:41:09,800 --> 00:41:11,480
Speaker 2: start them all out at the same time, and then

867
00:41:11,520 --> 00:41:13,759
Speaker 2: you monitor it, and by measuring the difference in that

868
00:41:13,920 --> 00:41:16,560
Speaker 2: number of ticks after a year on your reference clock,

869
00:41:16,600 --> 00:41:19,120
Speaker 2: the one that's hanging out with you, you can tell where

870
00:41:19,160 --> 00:41:21,200
Speaker 2: stuff is in the solar system.

871
00:41:21,040 --> 00:41:24,759
Speaker 1: Like which spots in the solar system have slower time.

872
00:41:24,680 --> 00:41:28,520
Speaker 2: Yes, exactly, because slower time means more matter, more curvature,

873
00:41:28,600 --> 00:41:29,600
Speaker 2: more energy density.

874
00:41:29,640 --> 00:41:31,960
Speaker 1: Really, I guess, on top of what you already know

875
00:41:32,080 --> 00:41:35,239
Speaker 1: about the Solar system right like right now, even if

876
00:41:35,239 --> 00:41:38,399
Speaker 1: we didn't have dark matter, a clock near the Sun

877
00:41:38,400 --> 00:41:40,520
Speaker 1: would take slower than a clock here exactly.

878
00:41:40,680 --> 00:41:43,040
Speaker 2: And we've done some basic version of this, as I

879
00:41:43,040 --> 00:41:46,319
Speaker 2: said earlier, If a few clocks on Earth at different altitudes,

880
00:41:46,719 --> 00:41:48,920
Speaker 2: those are different distances from the matter of the Earth

881
00:41:48,960 --> 00:41:52,239
Speaker 2: and the ones closer do ticks more slowly, and satellites

882
00:41:52,320 --> 00:41:55,800
Speaker 2: up in space their clocks tick faster than atomic clocks

883
00:41:55,800 --> 00:41:57,120
Speaker 2: here on the surface of the Earth. And you've got

884
00:41:57,120 --> 00:42:00,000
Speaker 2: to take that new account famously when you're doing GPS,

885
00:42:00,000 --> 00:42:00,439
Speaker 2: et cetera.

886
00:42:00,600 --> 00:42:03,760
Speaker 1: But you're saying, we're not going to be using this effect,

887
00:42:03,960 --> 00:42:07,200
Speaker 1: this time dilation from relativity to measure dark matter. Dark

888
00:42:07,200 --> 00:42:08,319
Speaker 1: matter is just too weak.

889
00:42:08,480 --> 00:42:10,160
Speaker 2: Dark matter is too weak, and we think it's not

890
00:42:10,239 --> 00:42:12,360
Speaker 2: cluppy enough to really detect that, though it would be

891
00:42:12,400 --> 00:42:15,680
Speaker 2: super awesome. There's a special kind of dark matter which

892
00:42:15,880 --> 00:42:18,880
Speaker 2: might give much larger effects, which would be much easier

893
00:42:18,920 --> 00:42:22,280
Speaker 2: to discover. And this is a theory called fuzzy dark matter.

894
00:42:22,680 --> 00:42:27,439
Speaker 1: Sounds fuzzy. But wait, so you're saying, like this idea

895
00:42:27,480 --> 00:42:30,520
Speaker 1: of using atomic clocks to measure dark matter would only

896
00:42:30,560 --> 00:42:37,160
Speaker 1: work for a certain theoretical meaning guessie type of dark matter,

897
00:42:37,320 --> 00:42:39,279
Speaker 1: which we don't know whether it's true or not or

898
00:42:39,280 --> 00:42:42,320
Speaker 1: exists or not. M So this is a huge sources

899
00:42:42,360 --> 00:42:45,839
Speaker 1: in white scheme that you don't really know if it's

900
00:42:45,840 --> 00:42:46,279
Speaker 1: going to work.

901
00:42:46,360 --> 00:42:48,279
Speaker 2: You know, you were talking about nomenclature and now you're

902
00:42:48,320 --> 00:42:51,080
Speaker 2: using the words guess and scheme. You know, really kind

903
00:42:51,080 --> 00:42:53,279
Speaker 2: of undermine the credibility of science, but you know, this

904
00:42:53,480 --> 00:42:55,719
Speaker 2: is good faith stuff. This is like, hey, what if

905
00:42:55,800 --> 00:42:58,640
Speaker 2: dark matter is this other weird particular thing. How could

906
00:42:58,719 --> 00:43:01,320
Speaker 2: we see that and yet be best if we had experiments

907
00:43:01,320 --> 00:43:03,880
Speaker 2: which could detect any kind of dark matter. But you know,

908
00:43:03,920 --> 00:43:05,719
Speaker 2: there might be kinds of dark matter which we could

909
00:43:05,760 --> 00:43:08,360
Speaker 2: only detect in certain ways or easier to spot in

910
00:43:08,400 --> 00:43:10,279
Speaker 2: some ways. And so it's good to be creative and

911
00:43:10,320 --> 00:43:13,399
Speaker 2: think about how we could detect specific kinds of dark

912
00:43:13,440 --> 00:43:15,719
Speaker 2: matter as well, even though we don't know what dark

913
00:43:15,719 --> 00:43:17,600
Speaker 2: matter is. And if this theory is at.

914
00:43:17,440 --> 00:43:20,280
Speaker 1: All correct, well, I'm just trying to understand the scheme.

915
00:43:22,440 --> 00:43:24,680
Speaker 1: So are you saying there's a theoretical kind of dark

916
00:43:24,680 --> 00:43:26,880
Speaker 1: matter called fuzzy dark matter? So what is it? So?

917
00:43:27,040 --> 00:43:30,800
Speaker 2: Fuzzy dark matter suggests that maybe dark matter isn't very massive,

918
00:43:31,200 --> 00:43:33,640
Speaker 2: like some people suggest that dark matter could be like

919
00:43:33,719 --> 00:43:36,360
Speaker 2: one hundred GeV like the mass of a w or

920
00:43:36,360 --> 00:43:39,000
Speaker 2: a z boson, like one hundred times the mass of

921
00:43:39,040 --> 00:43:42,440
Speaker 2: a proton, a pretty hefty particle, almost as massive as

922
00:43:42,440 --> 00:43:45,439
Speaker 2: a Higgs. That's sort of the classic strategy, and there's

923
00:43:45,480 --> 00:43:48,359
Speaker 2: reasons for that. There's something called the wimp miracle check

924
00:43:48,400 --> 00:43:51,640
Speaker 2: in our podcast about that, which argues strongly that dark

925
00:43:51,680 --> 00:43:54,200
Speaker 2: matter should be around one hundred gv based on how

926
00:43:54,320 --> 00:43:56,560
Speaker 2: much of it there is in the universe. But people

927
00:43:56,600 --> 00:43:58,120
Speaker 2: are like, well, maybe that's all wrong, and there's an

928
00:43:58,120 --> 00:44:01,399
Speaker 2: assumption there that's wrong. What if dark matter super duper light,

929
00:44:01,680 --> 00:44:04,680
Speaker 2: like a trilliance the mass of an electron. So now

930
00:44:04,719 --> 00:44:07,840
Speaker 2: there's an enormous number of these dark matter particles, so

931
00:44:08,080 --> 00:44:10,520
Speaker 2: many more than you could even imagine, because you have

932
00:44:10,560 --> 00:44:13,480
Speaker 2: to somehow make like a big fraction of the mass

933
00:44:13,480 --> 00:44:16,320
Speaker 2: of the universe out of particles that are a tiny

934
00:44:16,360 --> 00:44:19,200
Speaker 2: fraction of the mass of the electron, which is already

935
00:44:19,320 --> 00:44:20,080
Speaker 2: very very light.

936
00:44:20,280 --> 00:44:22,440
Speaker 1: Well, first of all, I think this whole podcast is

937
00:44:22,440 --> 00:44:26,360
Speaker 1: a wimp miracle, Daniel. But I think you're saying, like

938
00:44:26,600 --> 00:44:29,760
Speaker 1: this version of dark matter, instead of being maybe marble

939
00:44:29,840 --> 00:44:33,560
Speaker 1: sized particles, they're like super tiny bb sized particles. And

940
00:44:33,600 --> 00:44:34,880
Speaker 1: some of that makes it fuzzier.

941
00:44:35,000 --> 00:44:37,200
Speaker 2: Yeah, it makes it fuzzier because if they're very very

942
00:44:37,239 --> 00:44:40,839
Speaker 2: low mass, then their wavelengths are more spread out. Some

943
00:44:40,920 --> 00:44:43,120
Speaker 2: of these things can have a wavelength like the size

944
00:44:43,120 --> 00:44:43,880
Speaker 2: of the galaxy.

945
00:44:44,120 --> 00:44:45,120
Speaker 1: What do you mean a wavelength?

946
00:44:45,320 --> 00:44:47,759
Speaker 2: The wavelength of a particle is like the distance on

947
00:44:47,800 --> 00:44:51,640
Speaker 2: which these quantum interference effects appear, and so you can

948
00:44:51,680 --> 00:44:54,879
Speaker 2: calculate this quantity. It's called the Debrogely wavelength. You'll see

949
00:44:54,960 --> 00:44:58,520
Speaker 2: wave like effects for a particle when you interact over

950
00:44:58,560 --> 00:45:01,760
Speaker 2: these kinds of distances, and that's the wavelength of a particle.

951
00:45:01,480 --> 00:45:03,680
Speaker 1: Meaning sort of like the size of it kind of right.

952
00:45:03,640 --> 00:45:05,799
Speaker 2: Sort of, Yeah, it's when it stops acting like a

953
00:45:05,840 --> 00:45:08,920
Speaker 2: blob like a particle and starts acting more like a wave.

954
00:45:09,080 --> 00:45:12,600
Speaker 2: Things that have wavelike behaviors. Really, it's always acting like

955
00:45:12,640 --> 00:45:14,200
Speaker 2: a wave. It's just that when you zoom out you

956
00:45:14,200 --> 00:45:15,840
Speaker 2: can approximate it as a particle.

957
00:45:15,960 --> 00:45:18,719
Speaker 1: Because they have low mass. What's the relationship between having

958
00:45:18,760 --> 00:45:21,320
Speaker 1: low mass and being having big wavelengths.

959
00:45:21,600 --> 00:45:24,200
Speaker 2: Well, the wavelength depends on your momentum and your mass,

960
00:45:24,400 --> 00:45:28,120
Speaker 2: So lower mass just means a larger wavelength because it's

961
00:45:28,160 --> 00:45:31,000
Speaker 2: really like a ratio between the momentum and the mass.

962
00:45:31,040 --> 00:45:33,160
Speaker 2: When things have a lot of kinetic energy relative to

963
00:45:33,160 --> 00:45:35,840
Speaker 2: their mass, they act more like light because light is

964
00:45:35,960 --> 00:45:38,640
Speaker 2: pure kinetic energy. When things have very small amounts of

965
00:45:38,680 --> 00:45:41,520
Speaker 2: energy relative to their mass, they're stationary, so they act

966
00:45:41,560 --> 00:45:44,680
Speaker 2: more like bits of sand, like particles, and so it's

967
00:45:44,680 --> 00:45:47,120
Speaker 2: just sort of a rough way to understand where that

968
00:45:47,120 --> 00:45:48,120
Speaker 2: transition happens.

969
00:45:48,440 --> 00:45:50,360
Speaker 1: Okay, So, then if dark matter is this kind of

970
00:45:50,440 --> 00:45:53,280
Speaker 1: fuzzy kind of dark matter, you're saying that each particle

971
00:45:53,280 --> 00:45:56,239
Speaker 1: would be super duper light, and it would also have

972
00:45:56,440 --> 00:45:59,920
Speaker 1: huge variations in their size. That's what you mean by fuzzy.

973
00:46:00,000 --> 00:46:01,960
Speaker 1: It's like they might be some of them might be

974
00:46:01,960 --> 00:46:03,640
Speaker 1: super big and somewhere might be super small.

975
00:46:03,880 --> 00:46:06,399
Speaker 2: Yeah. Well, the wavelengths could be very very large, which

976
00:46:06,400 --> 00:46:09,040
Speaker 2: means they can interact over long distances. But the fascinating

977
00:46:09,080 --> 00:46:11,600
Speaker 2: thing is that in simulations of this dark matter, it

978
00:46:11,680 --> 00:46:14,520
Speaker 2: predicts like a mini halo of dark matter in our

979
00:46:14,600 --> 00:46:17,560
Speaker 2: Solar system, essentially that this stuff would be clumped up

980
00:46:17,600 --> 00:46:20,560
Speaker 2: in and near the Sun. That most of the dark

981
00:46:20,600 --> 00:46:23,520
Speaker 2: matter in the Solar System might be like clumped up

982
00:46:23,600 --> 00:46:26,120
Speaker 2: near the Sun. It might be like hiding in the Sun.

983
00:46:26,719 --> 00:46:28,719
Speaker 1: And if it wasn't this kind of fuzzy dark matter,

984
00:46:28,800 --> 00:46:29,320
Speaker 1: it wouldn't.

985
00:46:29,560 --> 00:46:31,880
Speaker 2: Now, this kind of fuzzy dark matter is the kind

986
00:46:31,920 --> 00:46:33,440
Speaker 2: we think would clump up like a.

987
00:46:33,400 --> 00:46:35,840
Speaker 1: Halo near the Sun, and the other kinds wouldn't.

988
00:46:35,920 --> 00:46:38,359
Speaker 2: Yeah, the other kinds wouldn't necessarily, I mean, I've heard

989
00:46:38,400 --> 00:46:40,960
Speaker 2: of other theories of dark matter clumping in the Sun.

990
00:46:40,960 --> 00:46:44,200
Speaker 2: There's all sorts of theories, but this particular one tends

991
00:46:44,239 --> 00:46:47,120
Speaker 2: to make a halo near the Sun and would affect

992
00:46:47,120 --> 00:46:50,440
Speaker 2: the operation of quantum clocks because of its special fuzziness.

993
00:46:50,600 --> 00:46:53,960
Speaker 2: It can also slightly interact with electrons through sort of

994
00:46:54,000 --> 00:46:56,560
Speaker 2: like a back door in quantum mechanics, which would change

995
00:46:56,600 --> 00:46:59,120
Speaker 2: the way a quantum clock operates. It's like it changes

996
00:46:59,160 --> 00:47:02,680
Speaker 2: the electrons math and how it responds to photons because

997
00:47:02,719 --> 00:47:06,480
Speaker 2: of oscillations in this fuzzy dark matter field, and so

998
00:47:06,640 --> 00:47:10,239
Speaker 2: effectively it changes the frequency of these clocks. And so

999
00:47:10,320 --> 00:47:13,360
Speaker 2: you can detect in principle whether you're near a dense

1000
00:47:13,440 --> 00:47:16,640
Speaker 2: blob of this ultra light dark matter by looking at

1001
00:47:16,640 --> 00:47:19,560
Speaker 2: a quantum clock and counting its ticks very carefully. And

1002
00:47:19,600 --> 00:47:21,520
Speaker 2: this would be a bigger effect than the effect we

1003
00:47:21,800 --> 00:47:24,000
Speaker 2: talked about earlier, the gravitational curvature.

1004
00:47:24,120 --> 00:47:26,680
Speaker 1: But I thought that dark matter couldn't interact with regular

1005
00:47:26,719 --> 00:47:29,280
Speaker 1: matter only through it could only do it through gravity.

1006
00:47:29,400 --> 00:47:31,800
Speaker 2: Yeah, it could only do it through gravity in general,

1007
00:47:31,840 --> 00:47:34,080
Speaker 2: But this one takes a back door through the Higgs field.

1008
00:47:34,400 --> 00:47:36,640
Speaker 2: It like interacts with the Higgs field and it changes

1009
00:47:36,640 --> 00:47:39,280
Speaker 2: how the Higgs field works, and so near the presence

1010
00:47:39,280 --> 00:47:41,960
Speaker 2: of this ultra light dark matter, electrons effectively have a

1011
00:47:42,000 --> 00:47:42,840
Speaker 2: different mass.

1012
00:47:43,800 --> 00:47:46,080
Speaker 1: But I guess if that was true, wouldn't we see

1013
00:47:46,280 --> 00:47:49,200
Speaker 1: it effect regular matter on a larger scale.

1014
00:47:49,280 --> 00:47:51,200
Speaker 2: You would see it happen, but it's a subtle effect,

1015
00:47:51,360 --> 00:47:53,400
Speaker 2: and so you need to be near a dense clump

1016
00:47:53,480 --> 00:47:56,319
Speaker 2: of it. So the idea is, take something that's very

1017
00:47:56,360 --> 00:47:58,920
Speaker 2: very sensitive to the electron mass, like a quantum clock,

1018
00:47:59,120 --> 00:48:01,160
Speaker 2: and try to put it near a dense clump of

1019
00:48:01,160 --> 00:48:04,160
Speaker 2: this special ultra light dark matter, maybe near the Sun.

1020
00:48:04,800 --> 00:48:06,640
Speaker 2: So that's the idea is, like launch a bunch of

1021
00:48:06,719 --> 00:48:09,279
Speaker 2: quantum clocks, have them orbit near the Sun, and look

1022
00:48:09,320 --> 00:48:12,560
Speaker 2: for deviations in their timekeeping, and see if that's evidence

1023
00:48:12,680 --> 00:48:15,920
Speaker 2: for ultra light dark matter interfering with the masses of

1024
00:48:15,960 --> 00:48:17,880
Speaker 2: the electrons in these quantum clocks.

1025
00:48:18,040 --> 00:48:19,959
Speaker 1: We mean that you would maybe like throw a bunch

1026
00:48:19,960 --> 00:48:22,719
Speaker 1: of the sun, have them kind of form a half

1027
00:48:22,840 --> 00:48:25,719
Speaker 1: ring around the Sun to see if time changes there,

1028
00:48:25,880 --> 00:48:28,399
Speaker 1: sort of like a giant tirra, like.

1029
00:48:28,440 --> 00:48:31,280
Speaker 2: A giant tr a quantum cosmic tira.

1030
00:48:31,560 --> 00:48:33,600
Speaker 1: All right, But I guess which one would you be proving?

1031
00:48:33,640 --> 00:48:36,640
Speaker 1: Would you be proving that dark matter is fuzzy, or

1032
00:48:36,719 --> 00:48:39,680
Speaker 1: would you be proving that it's there? Or are they

1033
00:48:39,719 --> 00:48:40,320
Speaker 1: both related?

1034
00:48:40,520 --> 00:48:41,360
Speaker 2: They're both related.

1035
00:48:41,400 --> 00:48:41,600
Speaker 4: Though.

1036
00:48:41,680 --> 00:48:43,920
Speaker 2: You know, if we saw this thing, there would instantly

1037
00:48:43,960 --> 00:48:46,719
Speaker 2: be like fifty other theories to explain it as well.

1038
00:48:47,000 --> 00:48:49,719
Speaker 2: It probably wouldn't be a unique prediction of this kind

1039
00:48:49,760 --> 00:48:52,320
Speaker 2: of dark matter. Theories are very very clever people, and

1040
00:48:52,360 --> 00:48:54,640
Speaker 2: they'll always come up with another way to explain the

1041
00:48:54,719 --> 00:48:57,440
Speaker 2: data that we were seeing. But it's cool because it's

1042
00:48:57,440 --> 00:48:59,719
Speaker 2: a prediction that this theory makes and we go out

1043
00:48:59,760 --> 00:49:02,160
Speaker 2: and we see it. That's really fascinating, and then we

1044
00:49:02,200 --> 00:49:04,760
Speaker 2: can think about ways to distinguish all the different ideas

1045
00:49:04,760 --> 00:49:08,120
Speaker 2: that might also explain this kind of observation. It would

1046
00:49:08,200 --> 00:49:10,640
Speaker 2: just be cool to see something different. Currently, all of

1047
00:49:10,640 --> 00:49:14,279
Speaker 2: our dark matter experiments basically see nothing. It would be

1048
00:49:14,320 --> 00:49:15,760
Speaker 2: cool to have a signal somewhere.

1049
00:49:16,680 --> 00:49:18,880
Speaker 1: So you're thinking, hey, let's put a bunch of microways

1050
00:49:18,880 --> 00:49:21,280
Speaker 1: in space and see if it sticks exactly.

1051
00:49:21,360 --> 00:49:23,240
Speaker 2: Let's see if one burrito is a little bit colder

1052
00:49:23,280 --> 00:49:23,760
Speaker 2: than another.

1053
00:49:24,040 --> 00:49:26,680
Speaker 1: All right, Well, an interesting idea for how we could

1054
00:49:26,760 --> 00:49:31,600
Speaker 1: maybe possibly crack sort of a theoretical version of one

1055
00:49:31,600 --> 00:49:33,360
Speaker 1: of the biggest mysteries in the universe.

1056
00:49:33,560 --> 00:49:35,840
Speaker 2: That's right. Physicists are being very creative and trying to

1057
00:49:35,840 --> 00:49:38,200
Speaker 2: come up with new theories of dark matter and new

1058
00:49:38,239 --> 00:49:42,000
Speaker 2: ways to discover them, including using super duper sets in

1059
00:49:42,160 --> 00:49:46,040
Speaker 2: quantum clocks distributed through the solar system, which also would

1060
00:49:46,080 --> 00:49:46,839
Speaker 2: just be fun to do.

1061
00:49:47,120 --> 00:49:49,920
Speaker 1: You just want to parade, Daniel, I just want a Tiara?

1062
00:49:50,120 --> 00:49:51,560
Speaker 2: Is that too much to ask?

1063
00:49:53,600 --> 00:49:55,120
Speaker 1: How about we just buy you a Tiara?

1064
00:49:55,600 --> 00:49:57,440
Speaker 2: Is it made of dark matter? Are you using your bitcoin?

1065
00:49:57,600 --> 00:49:59,440
Speaker 1: It can be, but in any way that you want.

1066
00:50:00,480 --> 00:50:03,759
Speaker 1: But if it's saves tax dollars billions of dollars, you know,

1067
00:50:03,800 --> 00:50:05,000
Speaker 1: it would be a pretty good investment.

1068
00:50:05,040 --> 00:50:07,239
Speaker 2: Yeah, there we go. That was my scheme the whole time.

1069
00:50:07,400 --> 00:50:10,640
Speaker 1: Yeah, to get us to buy you at tiara without

1070
00:50:10,680 --> 00:50:12,480
Speaker 1: actually having to run in a beauty contest.

1071
00:50:13,920 --> 00:50:14,560
Speaker 2: I'm busted.

1072
00:50:15,600 --> 00:50:19,520
Speaker 1: Well, you are the most beautiful podcaster with a show

1073
00:50:19,560 --> 00:50:23,040
Speaker 1: called Daniel Jorge Explaining the Universe. So whose name is Daniels?

1074
00:50:23,160 --> 00:50:25,319
Speaker 2: I'll take very highly qualified compliments, thank you.

1075
00:50:26,680 --> 00:50:30,719
Speaker 1: It's a very specific tiara based on a very theoretical

1076
00:50:31,440 --> 00:50:33,080
Speaker 1: model of the universe.

1077
00:50:33,080 --> 00:50:34,839
Speaker 2: Fuzzy compliments from Morehey, all.

1078
00:50:34,800 --> 00:50:37,319
Speaker 1: Right, well we hope you enjoyed that. Thanks for joining us.

1079
00:50:37,880 --> 00:50:38,680
Speaker 1: See you next time.

1080
00:50:43,480 --> 00:50:46,680
Speaker 2: For more science and curiosity, come find us on social media,

1081
00:50:46,760 --> 00:50:51,360
Speaker 2: where we answer questions and post videos. We're on Twitter, Discord, Instant,

1082
00:50:51,440 --> 00:50:55,240
Speaker 2: and now TikTok. Thanks for listening, and remember that Daniel

1083
00:50:55,239 --> 00:50:58,600
Speaker 2: and Jorge Explain the Universe is a production of Iheartworting.

1084
00:50:59,000 --> 00:51:04,160
Speaker 2: For more podcast from iHeartRadio, visit the iHeartRadio app, Apple Podcasts,

1085
00:51:04,239 --> 00:51:06,600
Speaker 2: or wherever you listen to your favorite shows.