Latest / Daniel and Kelly’s Extraordinary Universe / Why do we think dark matter is made of particles?

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Why do we think dark matter is made of particles? · Daniel and Kelly’s Extraordinary Universe

0:01
Speaker 1: Hey, it' Jorhan Daniel here, and we want to tell
0:03
Speaker 1: you about our new book. It's called Frequently Asked Questions
0:06
Speaker 1: about the Universe because you have questions about the universe,
0:09
Speaker 1: and so we decided to write a book all about them.
0:12
Speaker 1: We talk about your questions, we give some answers, we
0:14
Speaker 1: make a bunch of silly jokes as usual, and we
0:17
Speaker 1: tackle all kinds of questions, including what happens if I
0:20
Speaker 1: fall into a black hole? Or is there another version
0:22
Speaker 1: of you out there that's right? Like usual, we tackle
0:25
Speaker 1: the deepest, darkest, biggest, craziest questions about this incredible cosmos.
0:29
Speaker 1: If you want to support the podcast, please get the
0:31
Speaker 1: book and get a copy not just for yourself, but
0:34
Speaker 1: you know, for your nieces and nephews, cousins, friends, parents, dogs, hamsters,
0:39
Speaker 1: and for the aliens. So get your copy of Frequently
0:42
Speaker 1: Asked Questions about the Universe is available for pre order now,
0:46
Speaker 1: coming out November two. You can find more details at
0:49
Speaker 1: the book's website, Universe f a Q dot com. Thanks
0:53
Speaker 1: for your support, and if you have a hamster that
0:55
Speaker 1: can read, please let us know. We'd love to have
0:57
Speaker 1: them on the podcast. Hey Daniel, do you think we'll
1:14
Speaker 1: figure out what dark matter is one day. Yeah. I
1:16
Speaker 1: have faith in our human intelligence. I think we're going
1:18
Speaker 1: to crack this puzzle. Oh wow, I didn't figure you
1:21
Speaker 1: to be an optimist. But do you think, like, if
1:24
Speaker 1: we ever find out what it is it might be
1:26
Speaker 1: like disappointing. I don't know. I don't see how that's possible.
1:29
Speaker 1: It's it's one of the greatest mysteries of science. Yeah,
1:32
Speaker 1: but what if the answer is kind of like not
1:34
Speaker 1: that interesting? Do you mean, like it's just a bunch
1:35
Speaker 1: of dark chocolate floating out in space and he had
1:38
Speaker 1: a lot of delicious matter out there. No, I mean, like,
1:41
Speaker 1: what if it's just like one kind of particle that
1:44
Speaker 1: does nothing interesting, Like it's a very simple particle. I
1:47
Speaker 1: think that no matter what the answer is, it's going
1:49
Speaker 1: to be satisfying to finally know after so many years
1:52
Speaker 1: of wondering. It seems kind of dangerous to have such
1:54
Speaker 1: high expectations. The universe has never disappointed me so far.
1:58
Speaker 1: Just wait till the end of this episode, though. Ye
2:15
Speaker 1: Hi am or handmade cartoonists and the creator of PhD Comics. Hi.
2:18
Speaker 1: I'm Daniel. I'm a particle physicist and a professor at
2:21
Speaker 1: U c Irvine, and I believe the universe has lots
2:24
Speaker 1: of crazy, fun adventures in store for us. Wow, you
2:27
Speaker 1: have a lot of high expectations for the thrill factor
2:30
Speaker 1: of the universe. I do, but it's also rooted in data.
2:33
Speaker 1: I mean, look at all the times we've discovered amazing, crazy,
2:36
Speaker 1: bonkers things about the universe. It keeps surpassing our expectations.
2:40
Speaker 1: It keeps even outstripping our science fiction authors in terms
2:43
Speaker 1: of creative ways the universe could be organized. Does that
2:46
Speaker 1: mean like every time you sit down and work at
2:48
Speaker 1: your office, it's like strapping on on a roller cluster ride.
2:52
Speaker 1: You're like, I don't know what's gonna happen, but it's
2:54
Speaker 1: gonna be an amazing thrill. Well, there's definitely always a
2:56
Speaker 1: question mark, you know, you never know in research if
2:59
Speaker 1: today is going to be the day you discover something
3:01
Speaker 1: incredible that changes history in the way we think about
3:04
Speaker 1: universe and life, or it's just gonna be another day
3:07
Speaker 1: of finding bugs in your code and you should have
3:09
Speaker 1: a seatbelt on your office chair. Justin king, I wear
3:12
Speaker 1: a helmet. Yeah, But anyways, welcome to our podcast. Daniel
3:14
Speaker 1: and Jorge explain the Universe a production of I Heart
3:17
Speaker 1: Radio and welcome to the roller coaster ride that is
3:20
Speaker 1: the discovery of our universe. We have just started to
3:23
Speaker 1: crank on up the tracks. We are that part of
3:25
Speaker 1: the roller coaster. We are gaining elevation, and you know
3:28
Speaker 1: that thrills are coming because most of the universe remains
3:32
Speaker 1: a mystery to us, and our job on the podcast
3:35
Speaker 1: here today and every day is to ask questions about
3:38
Speaker 1: all of those mysteries, to wonder what else is out there,
3:41
Speaker 1: how does it work? And are we gonna lose our
3:42
Speaker 1: hats when we find out? That's right? Don't raise your arms,
3:45
Speaker 1: wint in physics. It makes it more exciting. Do you
3:47
Speaker 1: think the roller coaster physics would be like a series
3:50
Speaker 1: of couches trapped into some wheels I see with physics
3:55
Speaker 1: taking naps on them. Yeah, there you go, and it
3:58
Speaker 1: just goes really slowly and slowly upside down and then
4:03
Speaker 1: the coffee spills out. You don't sound very excited. Don't
4:06
Speaker 1: forget that there are big adventures in physics. There are
4:09
Speaker 1: times in our history when we've had to throw away
4:11
Speaker 1: everything we thought we knew and completely reorient the way
4:14
Speaker 1: we think about the universe. So I don't know if
4:16
Speaker 1: those are drops or twists or turns or skeletons jumping
4:19
Speaker 1: out of the hodded house, but there's definitely some thrills
4:22
Speaker 1: on this ride. Yeah, it is a pretty interesting and
4:24
Speaker 1: amazing universe, full of surprises, and it's also full of giant,
4:29
Speaker 1: enormous mysteries, like, for example, the question of what is
4:32
Speaker 1: the universe made out of? That's right, We've been spending
4:35
Speaker 1: a lot of time trying to think about what we
4:36
Speaker 1: are made out of and what you are made out of,
4:39
Speaker 1: what that rock over there is made out of, what
4:41
Speaker 1: the rock himself is made out of. But it turns
4:44
Speaker 1: out the most to the universe is not made out
4:46
Speaker 1: of that kind of stuff. Most of the universe is
4:48
Speaker 1: something weird and different and new we only recently discovered
4:51
Speaker 1: even exists. Yeah, it's not just a little bit of
4:54
Speaker 1: the universe. It's a whopping third of the universe. It's
4:57
Speaker 1: something we totally don't know. And it's not just a
4:59
Speaker 1: third of the uni verse. It's like five times the
5:02
Speaker 1: amount of regular stuff in the universe, the stuff that
5:05
Speaker 1: you and I are made out of. Yeah, and I
5:06
Speaker 1: love how we call our stuff regular stuff, even though
5:09
Speaker 1: it's the unusual stuff. You know, it's it's the weird
5:12
Speaker 1: stuff in the universe. Most of the universe, the matter
5:15
Speaker 1: in the universe is this other weird stuff that's called
5:18
Speaker 1: dark matter. We are the sprinkles on top of the cupcake.
5:21
Speaker 1: We are not the cupcake. I guess I'm in regular
5:23
Speaker 1: as in, you know, like your bowel movements, boy, I mean,
5:29
Speaker 1: the rest of the universe is constipated. I don't know
5:31
Speaker 1: if anything's gonna be associated with bowel movements. I think
5:34
Speaker 1: it would be dark matter. Yeah, because it's dark. You know.
5:37
Speaker 1: My wife studies the biological dark matter, which is most
5:41
Speaker 1: of the stuff in the human genome and in the
5:43
Speaker 1: viral genome that we don't know. So it turns out
5:45
Speaker 1: that there's lots of things we don't know about the
5:47
Speaker 1: universe inside and outside of us. Yeah, they say a
5:50
Speaker 1: big part of our biology is a sort of unknown.
5:53
Speaker 1: And also just the very things that the universe is
5:56
Speaker 1: made out of. I mean not just us and you
5:58
Speaker 1: and me, but like all the rocks, all the us
6:00
Speaker 1: out there, all the dust, every planet out there is
6:02
Speaker 1: mad at of stuff that is not common in the universe.
6:05
Speaker 1: That's right, and that's unsatisfying, right. We want to know
6:08
Speaker 1: what the university is made out of, which means we
6:10
Speaker 1: want to understand everything that's out there, not just a
6:13
Speaker 1: tiny bit. If you wanted to study elephants, you wouldn't
6:16
Speaker 1: just look at their trunk, or you wouldn't just take
6:18
Speaker 1: a close look at your ear. You want to understand
6:20
Speaker 1: the whole elephant. And in the same way, we want
6:22
Speaker 1: to tackle the entire universe. We think ambitiously. We ask
6:25
Speaker 1: big questions and we demand big answers. Yeah, and so
6:28
Speaker 1: whopping of the universe? Is dark matter? This thing that
6:32
Speaker 1: we call dark matter because we don't actually know what
6:34
Speaker 1: it is, right, We only call it dark matter because
6:36
Speaker 1: it's dark because it doesn't interact with light, so you
6:39
Speaker 1: can't see it. And we know it's matter because it
6:42
Speaker 1: feels or it has gravitational effects, and so we call
6:45
Speaker 1: it matter, but we don't actually know what it is.
6:47
Speaker 1: It could be anything. Yeah, it could be a lot
6:49
Speaker 1: of things. There's basically a short list of things it
6:52
Speaker 1: can't be that we've ruled out, but otherwise it could
6:54
Speaker 1: be a lot of different stuff. That's right. It can
6:57
Speaker 1: be bald movement. It cannot be bald move unless you
7:00
Speaker 1: have really really strange bat movements, and I don't know
7:03
Speaker 1: what you've been eating. It's not a crappy universe, No,
7:05
Speaker 1: it's not. But you know, if you hear physicists talk
7:08
Speaker 1: about dark matter, they mostly talk about dark matter in
7:10
Speaker 1: terms of some particle is dark matter, of this particle
7:13
Speaker 1: is dark matter that particle. And that's the kind of
7:15
Speaker 1: thing physicists due because they don't know any better, right,
7:18
Speaker 1: they know the universe that we're familiar with is made
7:21
Speaker 1: of particles, and they sort of just like extrapolate from
7:23
Speaker 1: what we do know into the unknown. And you know,
7:26
Speaker 1: that's how science works. You build from what you know
7:29
Speaker 1: and you explore out into the unknown using the language
7:32
Speaker 1: and the constructs that you have in your mind. Right,
7:34
Speaker 1: I guess that makes sense. Right. You gotta go with
7:36
Speaker 1: what do you know currently, and if that doesn't work,
7:38
Speaker 1: then you know, you have to look for something else.
7:40
Speaker 1: And so we have episodes where we talked about dark
7:42
Speaker 1: matter and also how we know it's there, what it is,
7:45
Speaker 1: and we've talked about some of the things it could be.
7:48
Speaker 1: But in particular, it seems that physicists have sort of
7:50
Speaker 1: narrowed down or at least are mostly leaning on the
7:54
Speaker 1: idea that dark matter is some kind of particle, some
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Speaker 1: kind of particle that we just haven't really seen because it,
8:00
Speaker 1: I guess doesn't interact with electromagnetic forces. That's right. Physicists
8:05
Speaker 1: really like this idea. They like the idea that dark
8:07
Speaker 1: matter might be a particle. It's sort of the way
8:09
Speaker 1: they think. It's like if you ask a carpenter to
8:10
Speaker 1: build a house, he's going to make it for you
8:12
Speaker 1: out of wood, because that's what they're used to. And
8:14
Speaker 1: so physicists are sort of in a rut here thinking
8:17
Speaker 1: about dark matter in terms of particles. And on the
8:19
Speaker 1: podcast a few times we've talked about this, like is
8:22
Speaker 1: that justified? What evidence do we have that it's a particle?
8:24
Speaker 1: What arguments do we have that it might not be
8:26
Speaker 1: a particle? And we sort of glossed over this question.
8:29
Speaker 1: I think what you're saying is that physicists are very particular,
8:33
Speaker 1: they have a certain wave of doing things. But yeah,
8:36
Speaker 1: we've never really sort of dug into this idea of
8:38
Speaker 1: dark matter as a particle, like why do we think
8:41
Speaker 1: it could be a particle or and what do we
8:43
Speaker 1: know about this potential dark matter particle? Yeah, and there
8:45
Speaker 1: was a moment in early dark matter thought where people
8:49
Speaker 1: have this idea, this argument for why dark matter should
8:52
Speaker 1: be a particle, and it goes by the name of
8:54
Speaker 1: the whimp miracle. This is where you que in the
8:57
Speaker 1: angelic sounds, the whim miracle, the dark matter whim miracle. Yeah,
9:04
Speaker 1: and you know, this is really fun because it tells
9:06
Speaker 1: you something about human side of doing physics. You know,
9:09
Speaker 1: it's like somebody was doing calculations and they saw these
9:12
Speaker 1: numbers come together on the paper that really suggested that
9:15
Speaker 1: dark matter should be a particle. Almost like these numbers
9:18
Speaker 1: were a miracle. You know, this this moment when you're
9:21
Speaker 1: doing even theoretical physics, even when you're exploring the possibilities,
9:24
Speaker 1: when things just sort of like click together beautifully and
9:26
Speaker 1: you're like, wait, maybe that's the answer. It works so
9:29
Speaker 1: well that you almost have like a religious experience as
9:32
Speaker 1: a physicist. Yeah, and you wonder like, either this is
9:36
Speaker 1: a coincidence and it's just sort of strange and you know,
9:38
Speaker 1: almost miraculous, or it's the way things really work. And
9:42
Speaker 1: so those moments when you feel like maybe you've cracked something,
9:45
Speaker 1: maybe you've learned something deep about the universe that nobody
9:48
Speaker 1: else is known. I don't know if it's a religious experience,
9:50
Speaker 1: but it's definitely a powerful moment. But it is a
9:53
Speaker 1: pretty interesting concept and it might explain why dark matter
9:57
Speaker 1: is a particle. So to be on the program, we'll
9:59
Speaker 1: be asking the question, and why do physicists think dark
10:06
Speaker 1: matter is a particle? And not all physicists right to
10:10
Speaker 1: use a favorite social media response, a lot of physic
10:13
Speaker 1: this thing that dark matter is a particle. There's a
10:15
Speaker 1: vocal minority out there, and we'll talk about it that
10:17
Speaker 1: are pretty sure it's not. But I like how you
10:19
Speaker 1: phrased it a little earlier. You said the physicists have
10:22
Speaker 1: dark matter thoughts. They have dark thoughts. That seems very
10:26
Speaker 1: brudy and cool. Well, you know, you've got to suffer
10:28
Speaker 1: for your art, right, sometimes you gotta suffer for your physics. Also,
10:31
Speaker 1: you have to have a little existential ank, you know,
10:34
Speaker 1: to get the right idea sometimes, or maybe you need
10:36
Speaker 1: to physics a little to get your suffering. But anyways,
10:40
Speaker 1: as usually, we were wondering how many people out there
10:42
Speaker 1: had heard of this interesting concept of the whim miracle,
10:46
Speaker 1: and so Daniel went out there to ask people on
10:48
Speaker 1: the internet this question. So thanks everyone who game. We
10:51
Speaker 1: played along and answered random questions from an Internet physicist.
10:54
Speaker 1: If you'd like to participate and you're on the verge,
10:57
Speaker 1: please just sit down right to me. Send me an
10:59
Speaker 1: email to questions at Daniel and Jorge dot com. I
11:03
Speaker 1: know you want to think about it for a second.
11:05
Speaker 1: What do you think is the whimp miracle? Here's what
11:08
Speaker 1: people had to say. I have no idea what that is.
11:10
Speaker 1: I have never heard of that before. But the word
11:13
Speaker 1: whimp does maybe make me think of something that isn't strong,
11:20
Speaker 1: So maybe some sort of force that is not very strong.
11:24
Speaker 1: I'm not sure. Well, a whimp is a weekly interactive
11:27
Speaker 1: massive particle, I think, But what a mayor police? I
11:32
Speaker 1: really don't know. Or could it be that if we
11:35
Speaker 1: actually find a whimp, it will explain all our physics problems.
11:40
Speaker 1: That would be a miracle, wouldn't it a jeez? I
11:44
Speaker 1: don't know. Um, the whimp is, if I remember right,
11:50
Speaker 1: weekly weekly interacting, massive particle, weekly interacting. I feel a
12:00
Speaker 1: little more confident about the miracle, though I am. I
12:06
Speaker 1: am not sure. Maybe the miracle is that they can
12:12
Speaker 1: even exist with such weak interactions. I'm really not sure,
12:17
Speaker 1: al right. Not a very miraculous response here on the
12:21
Speaker 1: recognition of a WHIM miracle. No, I think this is
12:24
Speaker 1: something that's sort of buried inside academic physics, and I
12:27
Speaker 1: want to bring it out. I don't see people talking
12:28
Speaker 1: about this a lot online or in popular literature, but
12:32
Speaker 1: I think it's a really interesting and important idea because
12:34
Speaker 1: it really has shaped the way we look for dark matter,
12:37
Speaker 1: the way we think about dark matter, the whole sort
12:39
Speaker 1: of direction that academic physics has taken in exploring this
12:43
Speaker 1: largest of all mysteries. No, I can't believe something called
12:47
Speaker 1: the miracle hasn't caught on with the rest of the population.
12:51
Speaker 1: I guess. And I just realized that we talk about
12:53
Speaker 1: what WHIM stands for. It's an acronym. Yeah, exactly, it's
12:56
Speaker 1: an acronym. We've been confusing people for the last ten minutes, right,
13:00
Speaker 1: so let's explain it. A WHIMP is a weekly interacting
13:03
Speaker 1: massive particle, so w I m P weekly interacting massive particle.
13:08
Speaker 1: And what that means is that it's a particle. Right.
13:11
Speaker 1: It's massive. It's pretty heavy, something like a hundred g
13:14
Speaker 1: v or like a hundred times the mass of a proton,
13:17
Speaker 1: and weekly interacting means that it does not have any
13:20
Speaker 1: very strong interactions weekly there means like feebly interacting, like
13:24
Speaker 1: not very powerfully interacting. Right, it's like a whimpy particle
13:27
Speaker 1: out there, right, Like it's out there, but it's not
13:29
Speaker 1: very strong, doesn't have strong opinions, it doesn't really stand
13:32
Speaker 1: up for itself a whole lot. That's right, And it's
13:34
Speaker 1: sort of the standard in the literature for like the
13:37
Speaker 1: basic theory of dark matter, the vanilla theory, the most
13:40
Speaker 1: common one, the one that sort of fits all the
13:42
Speaker 1: constraints and is the simplest explanation we have. Al Right, well,
13:45
Speaker 1: let's recapt a little bit for people what dark matter
13:48
Speaker 1: is and how we know it's there and why whimp
13:51
Speaker 1: is one of the theories for it. Right, So we
13:53
Speaker 1: know the dark matter is out there because we've seen
13:56
Speaker 1: its effect on the universe. Right, we can tell that
13:59
Speaker 1: there's something out there that's creating gravitational forces that we
14:03
Speaker 1: otherwise cannot explain. When we look at how galaxies rotate,
14:06
Speaker 1: we see that they're rotating really really fast, but there
14:09
Speaker 1: isn't enough gravity to hold them together. Something else, invisible,
14:13
Speaker 1: something that we cannot see, must be in these galaxies
14:16
Speaker 1: keeping them together. And we look back at the history
14:19
Speaker 1: of the universe. We can tell that there was a
14:21
Speaker 1: lot of gravity that shaped the structure, that created like
14:24
Speaker 1: little gravitational wells from matter to forming for galaxies to
14:28
Speaker 1: come together. We wouldn't have galaxies in our universe at
14:31
Speaker 1: this point if we didn't have dark matter sort of
14:33
Speaker 1: tugging on everything and squeezing it together. And everywhere we
14:37
Speaker 1: look we see evidence for this kind of matter that's
14:39
Speaker 1: out there, So we know that it's a matter, We
14:42
Speaker 1: know that it's a source of gravity. We just don't
14:44
Speaker 1: know what it is. Yeah, we sort of know it's there,
14:47
Speaker 1: and we know it has substance to it, right, because
14:49
Speaker 1: it's sort of like its presence is affecting things in
14:52
Speaker 1: very large ways, right, like you said, with the galaxies
14:55
Speaker 1: and with the Big Bang, And it's not just a
14:57
Speaker 1: little bit of stuff out there, it's a lot, right.
14:59
Speaker 1: It's like of the matter in the universe, that's right,
15:02
Speaker 1: it's eighty percent of the matter. So when you look
15:04
Speaker 1: at a galaxy, you're seeing only the bright bits, right,
15:07
Speaker 1: You're not seeing most of the galaxy. Most of it
15:10
Speaker 1: is actually dark matter. And something that throws people off
15:13
Speaker 1: sometimes it's thinking about where the dark matter is. The
15:15
Speaker 1: dark matter is mostly in the same places where the
15:18
Speaker 1: normal matter is because of gravity. Gravity pulls all this
15:21
Speaker 1: stuff together, so it's not like dark matters out there
15:23
Speaker 1: in deep space. There's a big halo of it that
15:26
Speaker 1: surrounds our galaxy. It's sort of like our galaxy is
15:29
Speaker 1: in a big bubble of dark matter. And while there's
15:32
Speaker 1: more dark matter out there in the universe than there
15:34
Speaker 1: is normal matter, it's not as condensed, right, It doesn't
15:37
Speaker 1: stick together as much, so it's sort of spread out
15:39
Speaker 1: evenly through our galaxy. So all normal matter clumps into
15:42
Speaker 1: like stars and planets. Dark matters spread out also between
15:46
Speaker 1: the stars. So in a random cube of space in
15:48
Speaker 1: our Solar system there might be more normal matter than
15:51
Speaker 1: dark matter. But then out there between the stars, this
15:53
Speaker 1: more dark matter the normal matter. It's like some big
15:56
Speaker 1: mysterious blob out there and that we can't see because
15:59
Speaker 1: it's dark and it doesn't reflect or transmit light. But
16:02
Speaker 1: we know it's there. But there are some things we
16:04
Speaker 1: sort of know about it, right, Like we know it's
16:06
Speaker 1: not made out of atoms. That's right. We know it's
16:08
Speaker 1: not made out of our kind of matter. It's not
16:10
Speaker 1: built out of atoms. And the way we know that
16:13
Speaker 1: it is really kind of awesome. It comes from a
16:15
Speaker 1: story from the very beginning of the universe. You know, atoms,
16:18
Speaker 1: of course are built out of quarks, and we know
16:21
Speaker 1: something about how many quarks were made sort of per
16:25
Speaker 1: cubic light year in the very early universe. What like,
16:29
Speaker 1: we know how many quarks were made in the Big Bang. Yeah,
16:31
Speaker 1: we can tell how many quarks were made because the
16:34
Speaker 1: density of corks determines what elements are formed later, Like
16:38
Speaker 1: if you have more quirks and you end up with
16:40
Speaker 1: heavier elements like lithium and helium, and if you have
16:44
Speaker 1: fewer quirks, you end up with more hydrogen and less
16:46
Speaker 1: like lithium and helium. So this is called Big Bang nucleosynthesis.
16:50
Speaker 1: The creation of heavier elements in during the Big Bang
16:54
Speaker 1: is very sensitive to the density of quarks. So we
16:57
Speaker 1: can tell essentially how many quarks there were, and then
17:00
Speaker 1: we can add them up and ask like, well, did
17:02
Speaker 1: we know where they all went? And you know, we
17:04
Speaker 1: don't know where every single exact quirk went, but we
17:07
Speaker 1: can tell that roughly they're all accounted for. And so
17:10
Speaker 1: dark matter is like, you know, a huge open mystery
17:14
Speaker 1: in this accounting book of the universe, So quarks definitely
17:17
Speaker 1: cannot explain it. It's like somebody's going to accounting jail.
17:21
Speaker 1: Let's hope the universe doesn't get audited. Who's gonna do
17:24
Speaker 1: the auditing. Maybe that's the miracle. Don't you know that
17:27
Speaker 1: it's not mad? Of course, because if it was made
17:29
Speaker 1: out of corks, you would be able to see it,
17:31
Speaker 1: like quarks interact with light, right exactly, we know a
17:33
Speaker 1: lot about how this stuff doesn't interact. And quarks have
17:37
Speaker 1: electric charge or either two thirds charged or negative one
17:40
Speaker 1: third chart, which means that they reflect photons and they
17:43
Speaker 1: give off photons and dark matter. You know, people say
17:46
Speaker 1: it's dark, That doesn't mean it's black. Like if you
17:48
Speaker 1: had a cloud of dark matter in front of you,
17:50
Speaker 1: you could see right through it. It's more like invisible matter.
17:53
Speaker 1: And that's because light passes right through it. And as
17:55
Speaker 1: you say, quarks interact with matter. But you know that's
17:57
Speaker 1: not as strong an argument, because you can all will
18:00
Speaker 1: make things that are transparent out of quarks. Right, glass,
18:03
Speaker 1: for example, is made out of quarks, but light passes
18:05
Speaker 1: right through it, and so to say that it doesn't
18:07
Speaker 1: interact with corks is not as strong an argument as
18:10
Speaker 1: to say, look, we know where all the quarks were.
18:12
Speaker 1: There just aren't enough corks to make the dark matter interesting.
18:15
Speaker 1: Like dark matter could be just like dark crystals out
18:18
Speaker 1: there or dark sharts of glass. But you know it
18:21
Speaker 1: can be because you you've accounted for all the courts
18:23
Speaker 1: that were made in the Big Bang precisely. Otherwise you'd
18:26
Speaker 1: have to consider maybe it's some weird combination of quirks,
18:29
Speaker 1: but there just aren't any quarks left in the budget.
18:31
Speaker 1: Once you've made the planets and the stars and the
18:33
Speaker 1: galaxies in the dust, you've used up all your quarks.
18:35
Speaker 1: You know, you have to make dark matter out of
18:37
Speaker 1: something else. Or maybe they were smuggled from another universe.
18:40
Speaker 1: That's my new theory. Somebody smuggled a whole bunch of
18:45
Speaker 1: dark crystals. You're like particle ice, right, show me your
18:49
Speaker 1: papers corks. Well, it's all around this dark matter, and
18:52
Speaker 1: it's pulling our galaxy together, keeping things all nice and cozy,
18:56
Speaker 1: and it's also keeping things pretty cool in the universe.
18:59
Speaker 1: So let's not a little bit more about dark matter
19:01
Speaker 1: and also why we think it could be a particle.
19:04
Speaker 1: But first, let's take a quick break. All right, we're
19:18
Speaker 1: talking about dark matter and the whimp miracle, which is
19:22
Speaker 1: not a food product. It's not like a miracle whimp.
19:25
Speaker 1: I do not recommend you put it on your tast
19:27
Speaker 1: but it is an interesting concept, is whip miracle, which
19:30
Speaker 1: could explain what dark matter is because it's dark matter?
19:33
Speaker 1: Is this big mystery out there and we know a
19:35
Speaker 1: few things about dark matter. We talked about it not
19:38
Speaker 1: being made at Adams, We talked about it being a
19:40
Speaker 1: sort of a key part of the Big Bang. But
19:42
Speaker 1: there are a couple of other things we know about it,
19:44
Speaker 1: right Doniel, Like we know it's not hot. Yeah, exactly.
19:48
Speaker 1: If you put dark matter up on my hot or
19:50
Speaker 1: not on the internet, you're definitely gonna get not because
19:53
Speaker 1: dark matter is quite cold. And some people wonder, you know,
19:56
Speaker 1: like why is and dark matter just neutrinos? Neutrinos are
19:59
Speaker 1: not made out of quarks and they don't interact very much,
20:01
Speaker 1: and we know that there's a lot of them. How
20:02
Speaker 1: do we know dark matter isn't just a bunch of neutrinos,
20:05
Speaker 1: like a huge number of neutrinos. And as much as
20:09
Speaker 1: I like to imagine a universe that's like mostly neutrinos,
20:12
Speaker 1: Also because neutrinos hardly weigh anything, and so if they're
20:15
Speaker 1: like eighty percent of the matter in the universe, then
20:17
Speaker 1: the would just be a ridiculous number of them, you know,
20:19
Speaker 1: like trillions and trillions and quadrillions of them. But we
20:23
Speaker 1: know that it's not just neutrinos. And the reason is
20:25
Speaker 1: that neutrinos have so little masks, so they move really quickly.
20:29
Speaker 1: Most of the neutrinos in the universe are zipping around everywhere.
20:32
Speaker 1: And we think that dark matter is cold, that it's
20:34
Speaker 1: slow moving, and we can tell because the way it
20:36
Speaker 1: clumps and clusters and falls into these gravitational wells that
20:39
Speaker 1: shape galaxies. If dark matter was neutrinos, then they would
20:43
Speaker 1: have spread out a lot more, they wouldn't have tended
20:44
Speaker 1: to form these clumps, and we wouldn't have the same
20:47
Speaker 1: sort of shape to the universe and clumpiness and clusters
20:49
Speaker 1: that we see today. So we're pretty sure dark matter
20:51
Speaker 1: is not neutrinos. It's some sort of slow moving object.
20:55
Speaker 1: Couldn't they be slow moving neutrinos like slow neutrinos. It
20:59
Speaker 1: could be, But what make slow neutrinos? You know, neutrinos
21:01
Speaker 1: are produced in stars and when they come out there
21:03
Speaker 1: pretty fast, and neutrinos I have such a small amount
21:07
Speaker 1: of mass that even very low energy neutrinos are moving
21:10
Speaker 1: near the speed of light. But if these were made
21:12
Speaker 1: at the beginning of the universe, maybe they've had time
21:15
Speaker 1: to slow down. But the beginning the universe was really fast.
21:17
Speaker 1: And if neutrinos hardly interact, then how are they going
21:19
Speaker 1: to slow down? Right? Where's all that energy going to go?
21:22
Speaker 1: Maybe they're just tired, it's been fourteen billion years running around.
21:27
Speaker 1: Maybe they just want to break, Or maybe neutrinos have
21:30
Speaker 1: been building up stamina for fourteen billion years, so they're
21:32
Speaker 1: going to go the distance. They're the underdogs. That's right,
21:37
Speaker 1: Go neutrinos go. But no, we're sure that they're not
21:39
Speaker 1: the dark matter. Dark matter is something else. So you know,
21:42
Speaker 1: we know it's dot atoms, we know it's not neutrinos,
21:45
Speaker 1: but that doesn't actually tell you what it is, right,
21:47
Speaker 1: we know a lot about what dark matter isn't none
21:49
Speaker 1: of this tells you about what dark matter actually is. Yeah,
21:52
Speaker 1: and so if we talked about in another episode about
21:54
Speaker 1: how it could be like some sort of weird new
21:55
Speaker 1: kind of liquid or in weird new kind of sort
21:57
Speaker 1: of matter, but it seems like the big ends out
22:00
Speaker 1: there sort of maybe points to dark matter being a particle. Yeah,
22:04
Speaker 1: there's an argument that was made about twenty years ago
22:07
Speaker 1: that commenced a lot of people that dark matter was
22:10
Speaker 1: probably a particle. And you know, we call it the
22:12
Speaker 1: whip miracle because it's this sort of like funny coincidence
22:15
Speaker 1: of numbers that fell out of equations that all would
22:17
Speaker 1: just work really, really nicely if dark matter was a
22:20
Speaker 1: weekly interacting massive particle, it would just sort of make
22:23
Speaker 1: a lot of sense and tie up a lot of
22:25
Speaker 1: loose ends all the same time. So that's why it
22:27
Speaker 1: was called the whimp miracle, like it would ma rexously
22:30
Speaker 1: come in and explain what dark matter is and all
22:32
Speaker 1: these numbers and evidence that you have, Yeah, exactly. And
22:35
Speaker 1: the argument is actually really interesting because it takes you
22:38
Speaker 1: back to the very beginning of universe when dark matter
22:41
Speaker 1: was made. We know how much dark matter there was
22:43
Speaker 1: in the very very early universe because we see its
22:45
Speaker 1: effect on the shape of the universe. We just did
22:48
Speaker 1: an episode where we talked about the universe ringing with
22:51
Speaker 1: sound and how those waves propagated through the universe. Those
22:54
Speaker 1: waves are affected by the dark matter in the universe.
22:58
Speaker 1: How much dark matter is. They're creating graphity to create
23:01
Speaker 1: the situation for those waves to propagate. So we can
23:03
Speaker 1: tell how much dark matter there was in the very
23:05
Speaker 1: early universe, and we can tell how much dark matter
23:08
Speaker 1: there is today. And there's a lot less today than
23:11
Speaker 1: there was in the very early universe. Most of it
23:13
Speaker 1: is gone. What we used to have more dark matter
23:17
Speaker 1: but then it went away. Yes, we used to have
23:19
Speaker 1: a lot more dark matter than we do today. Like
23:21
Speaker 1: the density of dark matter in the universe now is
23:23
Speaker 1: much lower than it was early on. Well, I guess
23:26
Speaker 1: maybe stepping back first, you said dark matter was made
23:28
Speaker 1: during the Big Bang. That's pretty cool. Like, I guess
23:31
Speaker 1: things were just like mostly energy at the very very beginning,
23:34
Speaker 1: and then it became dark matter. Just like it, you know,
23:37
Speaker 1: corks and other regular matter came to suddenly pop into existence.
23:41
Speaker 1: Dark matter also popped into existence. Yeah, you have this
23:44
Speaker 1: incredible moment where the universe is so hot and so
23:47
Speaker 1: dense that all the fields have so much energy in
23:50
Speaker 1: them that doesn't even really make sense to talk about
23:52
Speaker 1: individual particles. You know, it's like looking at the ocean
23:55
Speaker 1: and asking how many drops there are like drops are
23:58
Speaker 1: not the right way to talk about oceans. So in
24:00
Speaker 1: the very early universe, there was so much energy in
24:03
Speaker 1: all the quantum fields that like particles aren't even really
24:05
Speaker 1: a reasonable thing to talk about. But then as things
24:08
Speaker 1: cooled right and things got more dilute, and as the
24:11
Speaker 1: Big Bang went on, then there was a moment when
24:13
Speaker 1: these particles sort of like became the way to think
24:16
Speaker 1: about the universe, you know, And all this touches on
24:18
Speaker 1: something I think is really interesting, which is, like, what
24:20
Speaker 1: is the story we're telling about the universe? In every
24:23
Speaker 1: case we're like thinking about this in human terms and
24:26
Speaker 1: trying to find the right language to use to describe
24:28
Speaker 1: the universe. None of this is like fundamentally true. If
24:31
Speaker 1: we met aliens, they would be very confused by our
24:34
Speaker 1: description of the universe. And this is how we think
24:36
Speaker 1: about it. You think about the very early universe in
24:38
Speaker 1: terms of like fields filled with energy, and then later
24:40
Speaker 1: on it's reasonable to talk about it in terms of particles.
24:43
Speaker 1: And when that happened, when the transition happened, from like
24:46
Speaker 1: just fields filled with energy, then the energy spread out
24:49
Speaker 1: into all the different fields and made lots of different
24:51
Speaker 1: kinds of particles, corks and electrons and neutrinos, and also
24:54
Speaker 1: dark matter. So before like dark matter and regular matter,
24:57
Speaker 1: we're all just one kind of then it's sort of
25:00
Speaker 1: split into dark matter and regular matter. Yeah, you can
25:03
Speaker 1: think about it that way. And in the very early
25:04
Speaker 1: universe a lot of dark matter was made. And you know,
25:07
Speaker 1: we don't know again what dark matter is or what
25:09
Speaker 1: that field is, but we can measure how much there
25:11
Speaker 1: was because we see the evidence in the cosmic marcrowave
25:14
Speaker 1: background and in the structure of the universe. So where
25:17
Speaker 1: did all that dark matter go? Well, we're not sure.
25:19
Speaker 1: You know, it might have snuck back out into the
25:21
Speaker 1: other universe that I got smuggled in from, for example,
25:24
Speaker 1: re exported. But we think the theory is that dark
25:27
Speaker 1: matter has some way to interact with itself, right, Like,
25:31
Speaker 1: what can dark matter do? We know that it feels gravity,
25:33
Speaker 1: we've never seen it have any other force. We've never
25:36
Speaker 1: seen it interact with electromagnetism, or with the nuclear weak force,
25:40
Speaker 1: or with a strong force. But that doesn't mean there
25:42
Speaker 1: isn't some other force out there that dark matter particles
25:45
Speaker 1: feel some dark force. So imagine this some force where
25:49
Speaker 1: like if two dark matter particles bump into each other,
25:51
Speaker 1: they can annihilate. For example, maybe have a dark matter
25:54
Speaker 1: particle and in its antiparticle and they annihilate and they
25:57
Speaker 1: can turn into a photon or some other particle which
26:00
Speaker 1: can then turn into regular matter. So we have more
26:03
Speaker 1: regular matter than we had at the very beginning of
26:05
Speaker 1: the universe and less dark matter. So we think that
26:07
Speaker 1: some of it converted through this process from dark matter
26:10
Speaker 1: to regular matter. Oh, I see, because if you had
26:13
Speaker 1: more dark matter before, the only way it can sort
26:16
Speaker 1: of transform into something else is through some sort of
26:19
Speaker 1: interaction with itself, right, because it kind of interact with
26:22
Speaker 1: anything else. So it must have like, you know, two
26:25
Speaker 1: random bits of dark matter was crashing each other, turned
26:29
Speaker 1: into energy and then converted into regular matter exactly, And
26:33
Speaker 1: that would be like a portal for converting dark matter
26:36
Speaker 1: into regular matter. There'd be some kind of interaction there
26:39
Speaker 1: that we don't know about yet, some new dark force.
26:41
Speaker 1: So now we're talking about a new kind of matter
26:43
Speaker 1: and a new kind of force in the universe. But
26:47
Speaker 1: you know where else could the dark matter have gone?
26:49
Speaker 1: Somebody needs to restore balance in the force and the
26:52
Speaker 1: balance between light and dark. That's right, This all came
26:55
Speaker 1: out of the writing of young George Lucas. He was
26:57
Speaker 1: a physicist before he was a toymaker. Yeah, the whip
27:01
Speaker 1: Miracle was actually his first name for Star Wars, actually
27:04
Speaker 1: star Whimps. Yes, it fit the logo just as well,
27:07
Speaker 1: but then he thought war would sell more. Yeah, he
27:10
Speaker 1: was gonna call them whimps instead of Jedies, but it
27:12
Speaker 1: didn't work well in focus groups anyway. So this is
27:14
Speaker 1: something you can tell about that you don't just have
27:16
Speaker 1: to say, well, there must be some force. You can
27:18
Speaker 1: figure out how strong that force has to be, like
27:21
Speaker 1: how powerful is that force? How strong is that interaction?
27:24
Speaker 1: Because you know how much stuff there was in the
27:26
Speaker 1: early universe, you know how much of it got converted
27:28
Speaker 1: into stuff now, and you know how much time there was.
27:31
Speaker 1: And you could also play games like, well, you know,
27:34
Speaker 1: below a certain density, dark matter won't find itself anymore,
27:37
Speaker 1: it won't bang into itself to cause these interactions. So
27:40
Speaker 1: you put in a certain number for how strong this
27:42
Speaker 1: interaction is, and it tells you like how the dark
27:45
Speaker 1: matter turns into normal matter, like how many dark matter
27:48
Speaker 1: particles you should have per cubic light year today? But
27:52
Speaker 1: I guess you know here you're assuming that dark matter
27:54
Speaker 1: is a particle. So, like, you know, starting with that,
27:56
Speaker 1: you assume that dark matter is a particle and that
27:59
Speaker 1: these particles interact with themselves. And I think you're saying that,
28:02
Speaker 1: you know, if you sort of do all of the
28:03
Speaker 1: accounting about where all that energy and mass go, then
28:08
Speaker 1: you get a certain number for like the density of
28:10
Speaker 1: dark matter, yeah, the number of dark matter particles left over.
28:14
Speaker 1: And so if, for example, you say, well, this interaction
28:17
Speaker 1: is very very strong, it's very likely to happen, then
28:20
Speaker 1: you end up with less dark matter today. And if
28:22
Speaker 1: you say, oh, well this interaction is very very super
28:24
Speaker 1: duper weak, you end up with more dark matter left today,
28:27
Speaker 1: because that interaction isn't as good at turning dark matter
28:30
Speaker 1: into normal matter. So then you can ask the question, well,
28:33
Speaker 1: what number d you need to get the dark matter
28:36
Speaker 1: we see today, And so you can figure out what
28:38
Speaker 1: that number is, and when you do that calculation, you
28:41
Speaker 1: get a number, and that number is almost exactly the same.
28:45
Speaker 1: Strength is our favorite force, the weak interaction. And so
28:49
Speaker 1: people like, wait a second, that's interesting. Like you know,
28:52
Speaker 1: it's like if I, you know, saw a license plate
28:55
Speaker 1: on the getaway car and then I went over to
28:57
Speaker 1: your house for dinner and you had the same license plate.
28:59
Speaker 1: I'm like, in just in coincidence, Oh, I see. It's like,
29:03
Speaker 1: you know, there's dark matter missing in the universe, so
29:05
Speaker 1: it must be sort of volatile in some way, right,
29:07
Speaker 1: Like it must be. It must attempt to evaporate almost
29:10
Speaker 1: in a way. And if you sort of calculate how
29:13
Speaker 1: volatile it is, you get almost the same volatility kind
29:17
Speaker 1: of of the what we call the weak force, which
29:19
Speaker 1: is one of the four fundamental forces exactly, and we
29:22
Speaker 1: only have a few of these fundamental forces, and the
29:24
Speaker 1: weak force is kind of weird, right, It's really strangely weak.
29:27
Speaker 1: It's not like a you know, a basic simple force
29:30
Speaker 1: that has a strength. We understand. It's a very strange
29:33
Speaker 1: weak force. And so to find out that, in order
29:36
Speaker 1: to explain how much dark matter has disappeared from the universe,
29:39
Speaker 1: you need a force with basically exactly the same strength.
29:41
Speaker 1: That's one of the forces we already have. You're like,
29:43
Speaker 1: that's an interesting clue. So then you thought, all right,
29:46
Speaker 1: we'll assume that dark matter is a particle, and so
29:48
Speaker 1: it needs to interact through some kind of force. And hey,
29:50
Speaker 1: the force it seems to be interacting with is in
29:53
Speaker 1: the same like range as the weak force. So then
29:56
Speaker 1: you thought, maybe this particle that dark matter is is
30:00
Speaker 1: a weakly interacting particle exactly. And then you get to
30:04
Speaker 1: the massive parts. That's only like half of the whip miracle.
30:07
Speaker 1: The other half is the mass. Because this interaction strength
30:10
Speaker 1: the one that tells you, like how much dark matter
30:12
Speaker 1: is disappearing, That just tells you like how many dark
30:15
Speaker 1: matter particles are left over, like per cubic volume of
30:18
Speaker 1: the universe. Now you need to pick a mass right,
30:20
Speaker 1: like how massive is this particle? And if you pick
30:22
Speaker 1: a hundred g v, you know, a hundred times the
30:25
Speaker 1: mass of the proton, which is like how much mass
30:27
Speaker 1: all the weak particles have, the W, the z, the Higgs,
30:31
Speaker 1: Then you get exactly the right mass density for the universe.
30:34
Speaker 1: So the interaction strength gives you the right number density,
30:38
Speaker 1: like how many of these particles there are per cubic volume.
30:42
Speaker 1: And then if you pick the weak scale mass, you
30:44
Speaker 1: get exactly the right mass density. So it's like two
30:47
Speaker 1: miracles that line up perfectly. Interesting. It's like, according to
30:50
Speaker 1: your calculations, a particle that is heavy and interact with
30:54
Speaker 1: the weak force would fit the evidence of dark matter perfectly. Yeah,
30:59
Speaker 1: and you need both of the things to explain it. Like,
31:01
Speaker 1: if we had less dark matter today, then you need
31:05
Speaker 1: a higher cross section or you need a smaller mass.
31:07
Speaker 1: If we had more dark matter in our universe today,
31:10
Speaker 1: you need a lower cross section or a higher mass.
31:13
Speaker 1: So we just happen to have the right amount of
31:15
Speaker 1: dark matter left over in our universe that could be
31:18
Speaker 1: explained by a particle with the weak scale mass interacting
31:23
Speaker 1: at the weak scale interaction strength. Isn't that assuming you
31:26
Speaker 1: know kind of what happened in the Big Bang. Yeah,
31:28
Speaker 1: that's assuming that we know how much dark matter was
31:30
Speaker 1: made in the very early universe. But we're pretty sure
31:33
Speaker 1: about that. That doesn't require you to know anything about
31:35
Speaker 1: whether it's a particle or not. That's just from looking
31:38
Speaker 1: at its gravitational effects on things in their early universe,
31:41
Speaker 1: the cosmic microwy background, these very on acoustic costellations, the
31:45
Speaker 1: whole structure of the universe. So that's an independent measurement
31:48
Speaker 1: how much dark matter there was in the early universe.
31:51
Speaker 1: But this whole thing is a hypothesis, is saying, let's
31:53
Speaker 1: see if it works out if you assume dark matter
31:56
Speaker 1: as a particle, Like can we make this work? You
31:58
Speaker 1: know again, this is not wrecked evidence that it must
32:01
Speaker 1: be a particle. It's like, let's try it out and
32:03
Speaker 1: see if it fits. And then it like clicks in
32:05
Speaker 1: the place perfectly. And then it clicks in the place
32:07
Speaker 1: perfectly over there. You're like, WHOA, that seems compelling. I
32:11
Speaker 1: see you had like this big mystery and suddenly you
32:14
Speaker 1: have clues that tell you like, hey, this kind of particle,
32:17
Speaker 1: a weekly interacting massive particle whimp would fit just the
32:21
Speaker 1: bill for what we see. And that's why you called
32:23
Speaker 1: it a miracle. Yeah, because in two ways it just
32:27
Speaker 1: happened to fit the bill. And so people have this
32:29
Speaker 1: moment they're like wow, they're like got chills, you know,
32:32
Speaker 1: like the universe is talking to us, you know, like
32:36
Speaker 1: they had a religious experience, Like I figured it out.
32:38
Speaker 1: I I have godlike powers to figure this out. Do
32:41
Speaker 1: you think it's a religious experience? Every time you get chills,
32:44
Speaker 1: like if your kids turn on the A C too strongly,
32:46
Speaker 1: you're like, oh, I feel my faith coming back. I
32:49
Speaker 1: definitely do some cursing, for sure, but don't smite anybody.
32:54
Speaker 1: Or but yeah, there is a moment there where you
32:56
Speaker 1: feel like you have an insight or you've seen something
32:59
Speaker 1: clearly which used to be confusing, and so you know,
33:02
Speaker 1: maybe you're a spiritual person or not, but like that
33:05
Speaker 1: feels like maybe you've understood something. I think it's just
33:07
Speaker 1: like when you're cracking a case. You know, when you
33:09
Speaker 1: find a clue and it points exactly the direction that
33:12
Speaker 1: makes sense to you, you find another clue that confirms
33:14
Speaker 1: and and you're like, Okay, this is all coming together.
33:16
Speaker 1: Mm I see. So what you call the whip miracle
33:18
Speaker 1: is more like, hey, it's a miracle we figured it out. Yeah,
33:23
Speaker 1: it's a miracle that these numbers happen to be exactly
33:26
Speaker 1: what you would need for this particle to explain it.
33:29
Speaker 1: And you know, because whimps are a very very common
33:32
Speaker 1: thing in particle theories, like coming from the other direction.
33:36
Speaker 1: We have all these theories about what other particles might
33:39
Speaker 1: be out there, and one of the most common is
33:41
Speaker 1: this thing called supersymmetry, which is this theory that there
33:44
Speaker 1: are all these other particles out there, copies of the
33:47
Speaker 1: particles that we know and love, And in all of
33:50
Speaker 1: those theories they predict a particle just like this, they
33:53
Speaker 1: predict a whimp. A particle around a hundred giga electron
33:56
Speaker 1: volts that interacts about this strong and so that was
33:59
Speaker 1: an exciting moment. All right. So you had this big
34:02
Speaker 1: mystery of dark matter. You were looking for a solution,
34:04
Speaker 1: you were stumped, and then suddenly some people figured out
34:07
Speaker 1: that this idea of a whimp, a weekly interacting massive particle,
34:11
Speaker 1: is sort of like a miracle. It would totally describe
34:13
Speaker 1: what dark matter is. And so let's get into whether
34:16
Speaker 1: or not the whimp is a miracle and whether it
34:18
Speaker 1: does explain dark matter. That's a big mystery in itself.
34:21
Speaker 1: But first let's take a quick break. All right. We're
34:36
Speaker 1: talking about miracle whimp, which is I'm a different part
34:39
Speaker 1: of the grocery store as miracle whip. That's right. It's
34:42
Speaker 1: more than digestive section, right, Digestive aids to supplement for
34:48
Speaker 1: your dark matter so that it's not as as cold,
34:51
Speaker 1: so it moves a little faster. Yeah, heat have your
34:53
Speaker 1: dark matter, get it moving, all right. So we have
34:56
Speaker 1: this apparently miraculous theory about dark matter. It could be
34:59
Speaker 1: a weak the interacting massive particle, meaning like a heavy
35:02
Speaker 1: kind of particle that's slow, that's cool, but that interacts
35:05
Speaker 1: with itself and maybe other things through the weak force,
35:09
Speaker 1: which is one of the fundamental forces. Yeah, and so
35:11
Speaker 1: this became like the standard bearer, you know, all the
35:14
Speaker 1: ideas of what dark matter could be, particles, not particles,
35:17
Speaker 1: weird crazy stuff, dark chocolate floating out in space. This
35:20
Speaker 1: became like the favorite theory. And you know, the way
35:23
Speaker 1: physics works is you have like usually a mainstream idea
35:26
Speaker 1: and then you get the you know, the fringe ideas
35:28
Speaker 1: of other people working on different things that aren't really
35:30
Speaker 1: like the mainstream. But this very rapidly sort of took
35:33
Speaker 1: over the mainstream of physics, and people just were like assuming,
35:36
Speaker 1: all right, this is what dark matter is, or like,
35:38
Speaker 1: we don't know necessarily what that it's this, but this
35:41
Speaker 1: is a good candidate. So it makes sense to invest
35:44
Speaker 1: in like experiments that can look for this and to
35:46
Speaker 1: build complicated theories that include this. And so a lot
35:50
Speaker 1: of work was done because of this wid miracle assuming
35:53
Speaker 1: that dark matter was a whim because it's such a
35:56
Speaker 1: compelling theory, right, like it miraculously fits all the all
36:00
Speaker 1: the evidence we have about dark matter. It did at
36:02
Speaker 1: least it did. Okay, there's a whimp plot to us here,
36:06
Speaker 1: so I guess that was a leading theory, and so
36:08
Speaker 1: people went out there sort of looking for dark matter,
36:11
Speaker 1: assuming that it interacted with the weak force, and so
36:14
Speaker 1: do design experiments kind of along those lines. Yeah, the
36:17
Speaker 1: dominant experiments looking for dark matter as a particle are
36:20
Speaker 1: these big tanks of zenon underground or very very cold semiconductors,
36:26
Speaker 1: and they're all designed to look for a particle that's
36:28
Speaker 1: around a hundred g ev and interacts at the strength
36:32
Speaker 1: of the weak force and would like bump into a
36:34
Speaker 1: nucleus of zenon or nucleus of one of these semiconductors
36:39
Speaker 1: and give you a little signal. So they're like out
36:41
Speaker 1: there trying to catch this wind of dark matter that
36:44
Speaker 1: they thought the Earth was moving through, this wind of whimps.
36:47
Speaker 1: That's a George R. R. Martin book. I think the
36:50
Speaker 1: song of whimps, the song of particles, a song of
36:53
Speaker 1: particles and quarks, the winds of whimper. Yeah. I think
36:56
Speaker 1: we've had episodes where we talk about these dark matter
36:59
Speaker 1: hunt experiments, and yeah, they involved these giant tanks of
37:03
Speaker 1: cool liquid and you kind of hope that the dark
37:05
Speaker 1: matter cloud that the Earth is passing through somehow knocks
37:09
Speaker 1: some of those cold gas atoms around. That's right, And
37:12
Speaker 1: we don't know that dark matter has any interactions at all,
37:15
Speaker 1: you know. The only evidence we have that dark matter
37:17
Speaker 1: has some interactions is this argument that a bunch of
37:20
Speaker 1: it has disappeared since the real universe, and so there
37:23
Speaker 1: must be some interaction there if it's a particle, to
37:25
Speaker 1: convert it into normal matter. And so that was the
37:28
Speaker 1: basis for looking for these things and said, well, let's
37:31
Speaker 1: try to create a big tank of normal matter and
37:33
Speaker 1: hope that dark matter and bumps into it. That uses
37:35
Speaker 1: that same interaction that allows it to annihilate should also
37:39
Speaker 1: allow it to bump into normal matter very very occasionally. Right.
37:43
Speaker 1: It's not something like you're gonna see all the time.
37:45
Speaker 1: It's a very weak interaction. So you need a huge
37:48
Speaker 1: tank of stuff, you need to wait years, and when
37:50
Speaker 1: it bumps into the gas atom or particle, they'll create
37:53
Speaker 1: a little electron that you then sort of measure and
37:55
Speaker 1: you can say, hey, something bumped into my xenon gas.
37:59
Speaker 1: It must be dark matter. Yeah. It's sort of like
38:01
Speaker 1: putting a camera underground for five years and expecting, you know,
38:05
Speaker 1: just black images and then seeing a flash of light
38:08
Speaker 1: and you're like, oh, well, something was here, and we
38:10
Speaker 1: try to shield it from everything else, from muance and
38:13
Speaker 1: from radio active sources in the rock, and they do
38:15
Speaker 1: really careful job, like these are really tour to force
38:18
Speaker 1: experiments to try to make this liquid super quiet, so
38:21
Speaker 1: if you do see something, you're pretty sure it could
38:23
Speaker 1: be dark matter. And so we have episodes where you
38:25
Speaker 1: sort of take a deep dive into these Xenon experiments.
38:28
Speaker 1: But they they've been sort of going around for a
38:30
Speaker 1: while and what have they found since they haven't found anything, unfortunately,
38:35
Speaker 1: So they've been looking for this stuff, and you know,
38:36
Speaker 1: at first they're developed in the technology and then making
38:39
Speaker 1: them bigger and bigger, and they were at the point
38:41
Speaker 1: where they didn't expect to see it like they would
38:43
Speaker 1: have seen it if it happened to interact much more
38:45
Speaker 1: strongly than a whimp, if it happened to have some
38:48
Speaker 1: big surprise, they would have seen it the first experiments.
38:51
Speaker 1: But now these experiments are bigger and they've been running longer,
38:54
Speaker 1: and it's to the point where if the whimp existed
38:57
Speaker 1: and it did have this kind of interaction we're talking
38:59
Speaker 1: about the one that satisfies the whim miracle. We should
39:02
Speaker 1: have seen it already. So these experiments that basically ruled
39:05
Speaker 1: out the kind of particle that would perfectly satisfy the
39:08
Speaker 1: Whip miracle, like you've given up basically, Like people were
39:11
Speaker 1: waiting around to see if they found it and nothing,
39:13
Speaker 1: and so you're hanging up your coat. We're not turning
39:17
Speaker 1: off the lights, and you know, we're not like shut
39:19
Speaker 1: things down and you know, mothballing everything and going home
39:22
Speaker 1: to find new careers as cartoonists or something. I mean,
39:24
Speaker 1: that's bonkers. Yeah, that please don't do that yet. There
39:28
Speaker 1: are plenty of cartoons already. Know. It just means that,
39:30
Speaker 1: you know, the our simplest idea that there was one
39:33
Speaker 1: particle to explain all the dark matter and had a
39:35
Speaker 1: weak interaction, that idea doesn't work anymore. So we can
39:38
Speaker 1: modify the idea. We can try to keep the whip
39:41
Speaker 1: miracle by adjusting it a little bit. You know, we
39:43
Speaker 1: can find reasons why we wouldn't have seen it in
39:46
Speaker 1: these experiments. Maybe it only interacts with other kinds of matter,
39:49
Speaker 1: or we could say maybe dark matter is actually a
39:51
Speaker 1: few different kinds of things and they have like different
39:54
Speaker 1: interaction rates, and it's sort of just like all adds
39:57
Speaker 1: up to give us the explanation we have from the
39:59
Speaker 1: early universe. So people are being a bit more creative
40:01
Speaker 1: now in trying to find ways to keep the whimp
40:04
Speaker 1: and also avoid these experimental constraints. I guess I'm a
40:07
Speaker 1: little confused because I feel like it was only recently
40:09
Speaker 1: where we talked about some of these dark matter experiments.
40:12
Speaker 1: Are you saying that sort of in very recent times
40:15
Speaker 1: people have sort of concluded now that it's not a whimp. Yeah,
40:18
Speaker 1: these results are pretty recent. You know. People have been
40:20
Speaker 1: building up and building up and building up and thinking like, okay,
40:23
Speaker 1: around twenty twenties and when we're gonna have sensitivity to
40:25
Speaker 1: like the whim theory, you know, And now we've seen
40:29
Speaker 1: those results, and it seems pretty clear it's not a whimp.
40:32
Speaker 1: You know, we can keep looking for it. It might
40:33
Speaker 1: be something that interacts more weakly than the weak force.
40:38
Speaker 1: Might be like a very super weakly interacting massive particle
40:41
Speaker 1: that wouldn't satisfy the whim miracle. You need some other
40:44
Speaker 1: way to explain why you didn't get left over with
40:46
Speaker 1: extra dark matter in the universe if that interaction is
40:49
Speaker 1: so weak. But you know, their physicists so they got
40:51
Speaker 1: creative ideas to explain it. You know, none of the
40:53
Speaker 1: ideas are clicked together quite as nicely as the Wi Miracle.
40:56
Speaker 1: But the Wi Miracle didn't turn out to be right, right,
40:59
Speaker 1: Maybe it's light miracle whim left fat all right, So
41:03
Speaker 1: then if it's not a whimp, like if we're pretty
41:05
Speaker 1: sure it's not the whimp we thought it was, the
41:07
Speaker 1: miracle we thought it was, then what are some of
41:09
Speaker 1: these things that it could still be. Yeah, well, there's
41:12
Speaker 1: still lots of other fun theories of dark matter. And
41:14
Speaker 1: there's sort of been two categories. One is other particles,
41:18
Speaker 1: and we talked, for example, about whether dark matter is
41:20
Speaker 1: an axon. An axon is a really weird particles sort
41:23
Speaker 1: of like a heavy photon and interacts very differently than
41:27
Speaker 1: a whimp, and their experiments out there looking for that,
41:29
Speaker 1: so sort of a very different category of possibility for particles.
41:33
Speaker 1: It's also possible that dark matter isn't a particle at all.
41:37
Speaker 1: You know, this entire concept, this whole framing of the
41:40
Speaker 1: question assumes that the rest of the universe is similar
41:43
Speaker 1: to the part of the universe we've been studying for
41:44
Speaker 1: all these years, that regular matter is like a good
41:47
Speaker 1: pattern to start with, but it might not be. Remember,
41:51
Speaker 1: regular matter is unusual in the universe, so extrapolating from
41:54
Speaker 1: it to the rest of the universe seems not so justified.
41:57
Speaker 1: It could be that the rest of the universe, the
41:59
Speaker 1: other matter is something very weird and different. Could not
42:02
Speaker 1: necessarily even be a particle, right, It could be not matters,
42:05
Speaker 1: So it could be just like dark stuff or dark things. Yeah,
42:09
Speaker 1: there are crazy ideas, you know, things called un particles
42:12
Speaker 1: where the particles don't have a specific mass, and this
42:15
Speaker 1: is sort of like weird continuum of stuff where the
42:17
Speaker 1: more you zoom into it, it doesn't resolve into tiny
42:20
Speaker 1: little bits. It just like looks the same no matter
42:22
Speaker 1: how much you zoom into it, which would be really
42:25
Speaker 1: weird and awesome. And then we've talked to the podcast
42:27
Speaker 1: about one of my favorite theories that maybe dark matter
42:29
Speaker 1: is a huge number of tiny black holes left over
42:32
Speaker 1: from the Big Bang. We call them primordial black holes.
42:35
Speaker 1: That theory is under stress a little bit because we've
42:38
Speaker 1: looked for those and we haven't seen them, and there's
42:40
Speaker 1: ways that they can evade our telescopes. But you know,
42:42
Speaker 1: it's sort of less popular theory these days. But the
42:45
Speaker 1: point is we just really don't know. You know, our
42:47
Speaker 1: best theory, our best understanding, our best hypothesis that all
42:50
Speaker 1: clicked together nicely, that seems so promising, turned out to
42:53
Speaker 1: not be the theory of nature. It wasn't a miracle.
42:56
Speaker 1: You debunked America. Physicists once again kill the magic of
43:00
Speaker 1: the universe, prove there are no miracles in this world.
43:03
Speaker 1: That's right, downers since the hundreds. Or like you said,
43:08
Speaker 1: maybe it is a whim, but it's like a modified whim,
43:11
Speaker 1: right like, maybe it's a super a swimp, a super
43:13
Speaker 1: weekly interacting massive particle, or like a weekly interacting super
43:17
Speaker 1: massive particle with some Yeah, all those possibilities is still
43:23
Speaker 1: out there either way. It's all a big mystery and
43:25
Speaker 1: people are still looking for it. I guess kudo is
43:27
Speaker 1: still to those people who built those experiments and look
43:30
Speaker 1: for it, right Like, that's an important way to do
43:31
Speaker 1: progress in science. Absolutely it is. So there's a lot
43:34
Speaker 1: of criticism, you know, people out there say it's ridiculous
43:37
Speaker 1: that we spent tens of millions of dollars on this
43:39
Speaker 1: one idea for dark matter that some people never thought
43:43
Speaker 1: was very convincing. After all, you know, and so you
43:46
Speaker 1: see criticism of this online a lot of like I
43:49
Speaker 1: told you so, Yeah, a lot of I told you
43:51
Speaker 1: those you know, And but you never know with research, right,
43:54
Speaker 1: you'd never know are you going to discover something amazing
43:56
Speaker 1: or are you gonna gonna see nothing? And that's what
43:59
Speaker 1: explorer issue is. That's what research is. Fundamentally, it's exploration.
44:03
Speaker 1: If you knew the answers in advance, it wouldn't be
44:05
Speaker 1: as exciting to make the discoveries. There's no pending on
44:07
Speaker 1: the bag. That's just wagging out the fingers. All right, Well,
44:11
Speaker 1: I guess that's kind of what happens sometimes in signs.
44:13
Speaker 1: Sometimes you come up with an idea that seems to
44:15
Speaker 1: fit perfectly, it seems miraculous. Then you're pretty sure it's
44:18
Speaker 1: going to explain things. But the universe has other ideas.
44:21
Speaker 1: The universe always has a plot twist, The universe always
44:24
Speaker 1: has something out there to surprise us. And it's not
44:26
Speaker 1: like the universe was designed to surprise us. I think
44:29
Speaker 1: that's the issue, that it wasn't designed for us. That
44:32
Speaker 1: we have to adapt our minds to the reality of
44:35
Speaker 1: the universe, and the way we think the universe works
44:37
Speaker 1: is very different from the way it actually does, and
44:40
Speaker 1: so it's a continual readjustment which leads for lots of
44:42
Speaker 1: exciting surprises and plot twists. I guess maybe that is
44:45
Speaker 1: the miracle of the universe. The fact that it's full
44:47
Speaker 1: of surprises and keeps us on our toes and then
44:51
Speaker 1: we can understand any of it at all, frankly, is
44:53
Speaker 1: amazing to me. Or that we can talk about it
44:55
Speaker 1: for an hour twice a week, four hundreds of episodes,
45:00
Speaker 1: that's the real miracle. The fact that you're here listening
45:03
Speaker 1: to us. Yeah, thanks everybody for supporting us on this journey.
45:06
Speaker 1: We hope you enjoyed that. Thanks for joining us, See
45:09
Speaker 1: you next time. Thanks for listening, and remember that Daniel
45:19
Speaker 1: and Jorge explained. The Universe is a production of I
45:22
Speaker 1: Heart Radio or more podcast For my heart Radio, visit
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Speaker 1: the I heart Radio app, Apple Podcasts, or wherever you
45:29
Speaker 1: listen to your favorite shows.