Latest / Daniel and Kelly’s Extraordinary Universe / Listener Questions 37: quantum cats, heat death and dark multiverses!

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Listener Questions 37: quantum cats, heat death and dark multiverses! · Daniel and Kelly’s Extraordinary Universe

0:08
Speaker 1: Hey, Daniel, you own a cat, right? You know we
0:10
Speaker 1: used to have a cat, but no longer. Oh no,
0:13
Speaker 1: what happened local pack of coyotes? I'm afraid? Whoa where
0:16
Speaker 1: do you live? And to the wild. We have colonized
0:20
Speaker 1: the wild and turned it into suburbs. Yeah, it is
0:23
Speaker 1: a concrete jungle out there. But I wonder is that
0:25
Speaker 1: really the whole story or is there more to it?
0:28
Speaker 1: What do you mean? What are you accusing me of?
0:30
Speaker 1: I don't know. I think cats and physicists. It never
0:32
Speaker 1: seems to go, well, did you do some kind of
0:35
Speaker 1: crazy experiment on the cat? I did have a cat,
0:37
Speaker 1: and I did have a box. Whether or not I
0:39
Speaker 1: did that experiment, I'd rather not say. Maybe you did
0:42
Speaker 1: and maybe you didn't both at the same time. Now
0:45
Speaker 1: I'm feeling boxed in. But you know, if we live
0:47
Speaker 1: in a multiverse, technically there are probably cat physicists out there,
0:52
Speaker 1: maybe experimenting on human pets or what did the aliens
0:56
Speaker 1: that come to visit Earth are cats? What are you
0:58
Speaker 1: gonna do? Maybe the coyotes will protect us. That's like
1:00
Speaker 1: the idea for an animated movie. Cats versus coyotes versus physicists.
1:19
Speaker 1: Hi I'm Jory mccartoonists and the creator of PhD Comics. Hi.
1:23
Speaker 1: I'm Daniel. I'm a particle physicist and a professor at
1:25
Speaker 1: UC Irvine, and I really do miss my cats. Oh
1:29
Speaker 1: you had multiple cats? Is it starting to feel like
1:32
Speaker 1: a trend here, like a string of clues? Not just
1:35
Speaker 1: one cat in multiple superpositions, but two cats at the
1:38
Speaker 1: same time, which we've lost both the same summer. Oh, no,
1:42
Speaker 1: to coyotes, both of them, I'm afraid. So we had
1:44
Speaker 1: indoor outdoor cats in Chicago, where it's pretty safe, very
1:48
Speaker 1: few coyotes, but when we moved to Irvine, they didn't
1:51
Speaker 1: really last very long. We tried to keep them inside
1:53
Speaker 1: for a while, but it just wasn't possible. You need
1:56
Speaker 1: to get coyotes for pets, you know, just move up
1:58
Speaker 1: the food chain. Coyotes and raccoons. Yeah, those are great ideas.
2:05
Speaker 1: I mean, that's kind of what dogs are, sort of.
2:07
Speaker 1: What's the difference between a kyote and a dog? I
2:09
Speaker 1: think several thousands of years of breeding that can come
2:14
Speaker 1: in handy. But anyways, welcome to our podcast, Daniel and
2:17
Speaker 1: Jorge Explain the Universe, a production of iHeartRadio in which
2:20
Speaker 1: we do our best to tame the wild universe out
2:23
Speaker 1: there with all of its crazy feral physics, everything that's
2:26
Speaker 1: happening out there in the universe, the crazy quantum frothing
2:29
Speaker 1: foam all the way up to the huge black holes
2:32
Speaker 1: sucking up enormous amounts of gas and dust. We want
2:35
Speaker 1: to tame all of that and try to bring it
2:38
Speaker 1: under human understanding. We want to build an explanation of
2:41
Speaker 1: it that makes sense to our human minds, and that
2:43
Speaker 1: lets us think about what else we could do in
2:46
Speaker 1: this universe. It's right, the universe is a gigantic jungle
2:49
Speaker 1: of amazing information and facts, of incredible things that are
2:53
Speaker 1: happening out there in the cosmos between the galaxies and
2:56
Speaker 1: the supercluster of galaxies, and also here on Earth inside
2:59
Speaker 1: of our molecules. Scientists are there to explore and to
3:02
Speaker 1: map out everything and us in it. That's right. We
3:05
Speaker 1: are hacking our way through the jungle of the universe,
3:08
Speaker 1: trying to figure out where everything is, what does the
3:10
Speaker 1: landscape look like underneath, how has everything worked together? Though
3:13
Speaker 1: our goal, of course, is not to pave over it
3:16
Speaker 1: with suburbs, but just to understand it, to describe it,
3:19
Speaker 1: to appreciate its magnificence and beauty. We're here to pave
3:23
Speaker 1: it over with knowledge, I guess right, and curiosity. I
3:27
Speaker 1: don't want to pave over anything, really, I mean, I
3:29
Speaker 1: don't want to come to some alien planet and just
3:31
Speaker 1: like cover it and concrete and Starbucks unless is pretty
3:34
Speaker 1: inhospitable in the first place. Isn't concrete and Starbucks better
3:38
Speaker 1: than like the serves of Venus right now? I suppose,
3:41
Speaker 1: But you know, let Venus be Venus. Maybe there's some
3:43
Speaker 1: kind of life form that loves sulfuric acid clouds and
3:47
Speaker 1: super high pressures and temperatures and would be pretty offended
3:50
Speaker 1: or even exterminated by the presence of concrete and Starbucks.
3:54
Speaker 1: Or maybe it's just because they haven't discovered a nice
3:56
Speaker 1: spice latting, you know, and they'd be like, oh, thank
3:59
Speaker 1: you so much for opening my eyes to the true
4:02
Speaker 1: wonders of the universe. Maybe it wasn't fosphine in their atmosphere,
4:05
Speaker 1: it was pumpkin spice, after all, the beginning of a
4:09
Speaker 1: downfall of any civilization. We've discovered Starbucks on Venus, But
4:14
Speaker 1: it is a pretty wild universe out there, full of
4:17
Speaker 1: undiscovered things that we can discover and learn about and
4:20
Speaker 1: ponder about to get a better perspective of how the
4:22
Speaker 1: universe works. And the way to get these answers is
4:25
Speaker 1: to explore, to go out there and try to find
4:27
Speaker 1: things that don't make sense to us, things that are new,
4:30
Speaker 1: things that our brains can't quite yet grapple with that
4:33
Speaker 1: our mathematical stories do not yet include, or sometimes we
4:36
Speaker 1: try to take those mathematical stories and apply them to
4:38
Speaker 1: things we thought we understood. But the common thread there
4:41
Speaker 1: is asking questions. In the end, it all comes down
4:44
Speaker 1: to people being curious and wanting to understand how the
4:48
Speaker 1: universe works, applying our understanding to it, and asking questions
4:51
Speaker 1: when it doesn't quite work out in their minds. That's right.
4:54
Speaker 1: We are all explorers in this jungle of a universe,
4:56
Speaker 1: and I guess there are our main tool for hacking
4:59
Speaker 1: our weights through all of this mystery, our questions, Right,
5:02
Speaker 1: questions are kind of the machete of physicists. Yeah, some
5:06
Speaker 1: people might say the experiments are the machete, but questions
5:09
Speaker 1: are the first step. Right. That's how you decide what
5:12
Speaker 1: you're going to look for, That's how you decide what
5:14
Speaker 1: experiments you're going to do. That's how you frame the
5:16
Speaker 1: possible answers you might get to your crazy scientific questions.
5:20
Speaker 1: So in the end, it's questions and curiosity that is
5:23
Speaker 1: driving all of human science and maybe alien science and
5:26
Speaker 1: coyote science. I guess you just have to make sure
5:29
Speaker 1: that your questions are sharp, right, Like, if you had
5:31
Speaker 1: dull questions, that wouldn't get you very far. Yeah, you
5:34
Speaker 1: wouldn't slice through very much science jungle with a dull question.
5:37
Speaker 1: But questions people ask, and questions scientists ask in questions
5:41
Speaker 1: we ask here on the podcast, and sometimes we even
5:43
Speaker 1: answer them for listeners. That's right. We want you to
5:46
Speaker 1: be an active participant in this podcast, not just sitting
5:49
Speaker 1: back and listening to me and Jorge joke about bananas
5:52
Speaker 1: and talk about science, but to engage your brain, because
5:55
Speaker 1: our goal is not just entertain you, but to really
5:57
Speaker 1: bring a level of understanding into your mind. We want
6:00
Speaker 1: to put these pieces into your brain and teach you
6:03
Speaker 1: how to manipulate them so you can use them to
6:05
Speaker 1: answer new questions, your own questions. And so we love
6:08
Speaker 1: when listeners do that, and then they come back to
6:10
Speaker 1: us with things that didn't quite make sense to them
6:12
Speaker 1: that let us unravel a little bit of misunderstanding or
6:14
Speaker 1: help them get a clear picture for how things work.
6:17
Speaker 1: So today on the podcast we'll be tackling listener questions
6:26
Speaker 1: number thirty seven. This is our thirty seventh listener question episode.
6:30
Speaker 1: Absolutely and if you have a question that you have
6:33
Speaker 1: been wondering about, please don't be shy right to us
6:36
Speaker 1: to questions at Daniel d Jorge dot com. We really
6:39
Speaker 1: do write back emails to all of our listener questions
6:42
Speaker 1: and some of them get put here on the podcast
6:44
Speaker 1: for us to talk about. Just don't ask about Daniel's cats.
6:47
Speaker 1: Don't ask too many questions about that, because this whole
6:49
Speaker 1: coyote theory is a little suspicious. You know, there's only
6:53
Speaker 1: so many answers the universe can provide. There's a quantum
6:55
Speaker 1: uncertainty to everything. Sounds like a great criminals there. It
7:00
Speaker 1: sounds like even practicing that that's right. On advice of counsel,
7:03
Speaker 1: I would like to invoke the Heisenberg on certainty principle.
7:06
Speaker 1: Oh that would be a funny courtroom scene. And then
7:08
Speaker 1: the lawyer, the opposing articles all drat, they got us,
7:11
Speaker 1: he got us. He can't do anything against the Heisenberg defense. Well,
7:15
Speaker 1: you have the Boeian attack. Right, I got a little
7:17
Speaker 1: too deep for me. Yeah, we'd like to answer listener
7:19
Speaker 1: questions here on the podcast at people send in and
7:22
Speaker 1: people still send you questions, right, Daniel, Oh, absolutely, I
7:25
Speaker 1: get dozens of questions every day, and I enjoy reading
7:28
Speaker 1: all of them because they show me what people understand
7:31
Speaker 1: and what people don't understand. You know, as a teacher
7:33
Speaker 1: and educator, the actual material that I'm teaching isn't always
7:36
Speaker 1: terribly exciting to me because I've been doing it for
7:38
Speaker 1: decades and decades. What's always a really fun puzzle is
7:41
Speaker 1: what confuses people, What got people to some point in
7:44
Speaker 1: their understanding that they ask a certain question. The question
7:48
Speaker 1: always reveals how they got there and the misstep they took.
7:50
Speaker 1: So for me, it's a fun puzzle to go from
7:52
Speaker 1: the question to understanding where they went wrong and then
7:55
Speaker 1: helping them find a path to clarity. You enjoy seeing
7:59
Speaker 1: their confus sort of like a cat plays with its praying. Well,
8:05
Speaker 1: that's very confrontational approach, But yeah, I do enjoy seeing
8:08
Speaker 1: where people got confused. It helps me sharpen my explanations. Yeah. Cool, Well,
8:12
Speaker 1: today we have three awesome questions from listeners. One of
8:15
Speaker 1: them is about Schrodinger's cat, another one is about the
8:19
Speaker 1: heat death of the universe, and the last one is
8:22
Speaker 1: about parallel universes and dark matter and are those two
8:26
Speaker 1: things tied together? So we'll jump right into our first question,
8:30
Speaker 1: and this one comes from Nils, who's fourteen years old
8:33
Speaker 1: and comes from Sweden. Hi, my name is Nieves Pasel.
8:36
Speaker 1: I'm a Swedish fourteen year old very interested in both
8:39
Speaker 1: physics and philosophy. And my name's Jacob and I'm Niel's dad.
8:43
Speaker 1: I'm an ICU nurse currently working on my PhD in
8:46
Speaker 1: clinical neuroscience and I share my son's passion for physics
8:50
Speaker 1: and philosophy. The other day we had a discussion about
8:53
Speaker 1: Schrodinger's cat and we would absolutely love it if you
8:56
Speaker 1: guys shed some light on this Shuliess cat is well
9:00
Speaker 1: a cat and therefore a quite intelligent and curious creature.
9:04
Speaker 1: Couldn't this cat itself be considered to be an observer
9:08
Speaker 1: inside the box? And if there is an observer inside
9:12
Speaker 1: the box, wouldn't that collapse the quantum uncertainty immediately upon
9:16
Speaker 1: being observed by this cat? We would love to hear
9:19
Speaker 1: your thoughts outside as well as inside the Box on
9:22
Speaker 1: this and thank you for a great podcast. All Right,
9:24
Speaker 1: that's an awesome question. I would say that's a pretty
9:27
Speaker 1: awesome question. Categorically speaking, it is awesome and especially awesome
9:32
Speaker 1: to hear parents and kids talking about science and philosophy together.
9:36
Speaker 1: That's wonderful. So thank you very much to all the
9:38
Speaker 1: parents out there encouraging your kids to think about science. Yeah.
9:42
Speaker 1: We get a lot of kids asking questions with their
9:44
Speaker 1: parents sometimes. Yeah, and we hear from people who listen
9:47
Speaker 1: to the podcast with their kids and talk about it.
9:50
Speaker 1: And while that's a dream come true for me, awesome. Well,
9:52
Speaker 1: the question is an interesting one. They're asking us to
9:55
Speaker 1: basically sort of explain what Shroudinger's cat is. Yeah, And
9:58
Speaker 1: Shroudinger's cat is a really fun thought experiment that puts
10:01
Speaker 1: its finger or I guess it's paw or its claw
10:04
Speaker 1: on a big problem in quantum mechanics and at the
10:07
Speaker 1: intersection of physics and philosophy. Yeah. And their question then
10:11
Speaker 1: gets very specifically about the nature of an observer in
10:14
Speaker 1: a quantum experiment and what that means and whether cats
10:17
Speaker 1: are smart. I guess that's where those part of the
10:19
Speaker 1: question that might take up the whole episode though our
10:23
Speaker 1: cats as smartest people, and does that solve the quantum
10:25
Speaker 1: mechanics measurement problem. In the end, you're gonna have to
10:28
Speaker 1: continue this with Katie to talk about cats. But Yees
10:33
Speaker 1: steps through Daniel. What is Schrodinger's cat Shortinger's Cat is
10:36
Speaker 1: a thought experiment that tries to expose a conflict in
10:40
Speaker 1: quantum theory. Right, So, for hundreds of years, we had
10:43
Speaker 1: a classical theory of the universe, one that said that
10:47
Speaker 1: you know, objects have locations and that they have velocities,
10:50
Speaker 1: that there is a reality out there that has infinite
10:53
Speaker 1: information and can be knowable, and that an object is
10:56
Speaker 1: in one place and in no other place. But then
10:59
Speaker 1: we developed quantum theory when we discovered that tiny little
11:02
Speaker 1: objects like photons and electrons don't follow those same rules.
11:05
Speaker 1: They don't have trajectories where they have a specific location
11:09
Speaker 1: and a velocity at every point in time. Instead, they
11:12
Speaker 1: can have multiple possibilities. The electron could be here and
11:15
Speaker 1: it could also be there at the same time, so
11:18
Speaker 1: we call this a superposition of possibilities. So we had
11:22
Speaker 1: new quantum rules for quantum stuff, and we had classical
11:25
Speaker 1: rules for classical stuff. Because like me and you and
11:29
Speaker 1: baseballs and cats don't seem to be able to do
11:32
Speaker 1: that thing that quantum objects can do have a possibility
11:35
Speaker 1: of being in multiple places at once. So there's this
11:38
Speaker 1: weird conflict between the classical rules and the quantum rules
11:41
Speaker 1: and where they overlap. So Schroedinger's cat is a thought
11:44
Speaker 1: experiment that tries to put its finger on this conflict
11:46
Speaker 1: and raise difficult questions. Okay, so then the basic conflict
11:51
Speaker 1: here between quantum mechanics and classical physics, it's kind of
11:54
Speaker 1: this idea of certainty, right like in classical there's nothing
11:59
Speaker 1: uncertain about the baseball flying through the air. You sort
12:02
Speaker 1: of know where it's going to land, and when you're
12:04
Speaker 1: holding in your hand, it's like it's there, there's no
12:06
Speaker 1: question that it's there. But in quantum mechanics there's no
12:09
Speaker 1: such thing kind of as certainty, right Like you can't
12:11
Speaker 1: hold a photon or an electron in your hand. You
12:15
Speaker 1: only can only sort of know where it could be.
12:18
Speaker 1: There's a lot of uncertainty about where it actually is.
12:20
Speaker 1: That's right, And in the classical case, we can't have
12:24
Speaker 1: uncertainty about where the baseball is. But that uncertainty is
12:27
Speaker 1: just our lack of knowing the information does exist. The
12:30
Speaker 1: baseball is in one particular location, it has one particular velocity,
12:34
Speaker 1: we just might not know it. In the quantum case,
12:37
Speaker 1: we think that information doesn't actually exist, Like when the
12:40
Speaker 1: particle is going through the double slit experiment, it really
12:42
Speaker 1: has the possibility to go through both slits at the
12:45
Speaker 1: same time, or the electron really could be here and
12:47
Speaker 1: it really also could be there, not just that we
12:50
Speaker 1: don't know the answer, but that it really isn't determined.
12:53
Speaker 1: And then the conflict is what happens when classical stuff
12:55
Speaker 1: and quantum stuff interact. Right, when you, as a classical
12:59
Speaker 1: object act look for an electron and say, hey, I
13:02
Speaker 1: want to know which slit the electron went through. What happens, right,
13:06
Speaker 1: and so at that interface is the really awkward part,
13:08
Speaker 1: because classical objects can't be in two different states, but
13:11
Speaker 1: quantum objects kind of canm Well, I guess, first of all,
13:14
Speaker 1: thanks for calling me classy. A lot of people do that.
13:18
Speaker 1: So then you were saying that Schrodinger's cat is sort
13:20
Speaker 1: of an example or like a thought experiment that doesn't
13:23
Speaker 1: it's not there to explain what happens between quantum and
13:27
Speaker 1: classical physics. It's more there to like kind of like
13:30
Speaker 1: a point a finger to it, or illustrate this conflict. Yeah,
13:34
Speaker 1: there are a lot of these great thought experiments in
13:35
Speaker 1: quantum mechanics that say, hey, look what you're saying about
13:37
Speaker 1: reality is kind of ridiculous. Here's a ridiculous outcome if
13:41
Speaker 1: what you're saying is true. And Shortinger's cat is a
13:43
Speaker 1: great example of it, and it tries to put its
13:45
Speaker 1: finger on this question of like what happens when something
13:48
Speaker 1: classical touches something quantum. If you're observing a quantum particle,
13:51
Speaker 1: you don't observe it to be in two places at once.
13:54
Speaker 1: Somehow it collapses into just one choice. If the electron
13:57
Speaker 1: could be spin up or could be spin down when
14:00
Speaker 1: you observe it, you just get one or the other.
14:02
Speaker 1: How does that work? What is the distinction between a
14:05
Speaker 1: quantum object and a classical object? When does the classical
14:08
Speaker 1: object know to collapse? So Shortinger thought this was fairly ridiculous,
14:12
Speaker 1: So he came up with this example where you have
14:14
Speaker 1: a box and inside the box is some quantum process
14:17
Speaker 1: like an atom that decays radioactively, and so it might
14:20
Speaker 1: decay sooner or might decay later. Based on quantum mechanics.
14:23
Speaker 1: But now that's linked to something classical like a cat.
14:26
Speaker 1: So when the atom decays, for example, it's linked to
14:28
Speaker 1: some mechanism that releases a poison gas and kills the cat.
14:32
Speaker 1: So if the atom has decayed, the cat is dead.
14:34
Speaker 1: If the atom has not decayed, then the cat is alive.
14:37
Speaker 1: And this is a fascinating thought experiment because before you
14:40
Speaker 1: look in the box, you can say that the atom
14:43
Speaker 1: is in a superposition of having decayed and not having decayed.
14:46
Speaker 1: It's not one or the other, has a probability of both,
14:49
Speaker 1: which means that the cat in that same sense, has
14:52
Speaker 1: a probability of being alive and the probability of being
14:54
Speaker 1: dead at the same time. I see. So then the
14:57
Speaker 1: cat is inside and it could be alive or it
15:00
Speaker 1: could be dead, depending on the outcome of some quantum process.
15:04
Speaker 1: But I guess the name question that Neils and Jacob
15:06
Speaker 1: were asking is that you know the cat is alive
15:09
Speaker 1: and dead only to us from the outside of the box, right, Yeah,
15:14
Speaker 1: that's exactly right. And what they're asking is why doesn't
15:16
Speaker 1: the cat collapse? The uncertainty, right, if the cat is
15:19
Speaker 1: a big, curious creature and a classical object. It can't
15:22
Speaker 1: be in multiple states. It can't be dead and alive
15:25
Speaker 1: at the same time. Then why doesn't it collapse the
15:27
Speaker 1: possibilities and force this atom to either decay or not decay.
15:31
Speaker 1: That's essentially their question, right because to us, technically the
15:35
Speaker 1: cat is alive and dead according to quantum mechanics. But
15:37
Speaker 1: to the cat, the cat knows if it's alive or dead.
15:40
Speaker 1: I think that's what they're kind of asking, right, Like,
15:42
Speaker 1: the cat is a somewhat conscious creature, and it knows
15:46
Speaker 1: whether it's sort of it's observing things, right, it's looking
15:49
Speaker 1: at things inside and it's it knows if it's breathing
15:52
Speaker 1: or not. So does that mean that the cat definitely
15:56
Speaker 1: is alive or dead for the cat, But it's alive
15:59
Speaker 1: and dead for us outside of the box. So the
16:01
Speaker 1: answer depends on which interpretation or quantum mechanics you prefer, right,
16:06
Speaker 1: Because we can't know without opening the box. So you
16:08
Speaker 1: can't make a definite statement about what really happens when
16:11
Speaker 1: you don't open the box. All we can do is
16:13
Speaker 1: say what we think might happen and what it means.
16:16
Speaker 1: So we're in the era of philosophy because we don't
16:18
Speaker 1: have experiments we can do to distinguish between these various ideas,
16:22
Speaker 1: And one of the key problems is that we don't
16:24
Speaker 1: have a good distinction between what counts as quantum, what
16:27
Speaker 1: is allowed to be described by quantum rules can have uncertainty,
16:30
Speaker 1: and what counts as classical. Right, And the Copenhagen interpretation
16:34
Speaker 1: is sort of standard interpretation or quantum mechanics that's taught
16:36
Speaker 1: to physics majors doesn't define these things. It leaves it uncertain,
16:41
Speaker 1: and so there's no clear distinction like when does a
16:43
Speaker 1: wave function collapse and when does it not? It's not
16:46
Speaker 1: defined or maybe it's only defined or respect to an observer, right,
16:51
Speaker 1: what counts is a classical observer that has classical interactions,
16:53
Speaker 1: and what counts is a quantum observer that can have
16:56
Speaker 1: quantum interactions without collapsing the wave function. That's not to
17:00
Speaker 1: I guess. I mean it's like it feels like, you know,
17:02
Speaker 1: it definitely collapse for the cat, but for us outside
17:05
Speaker 1: of the box where we have like zero information exchange,
17:09
Speaker 1: the cat is still alive and dead to us. So
17:11
Speaker 1: that's a specific interpretation of quantum mechanics. Carlo Rovelli would
17:15
Speaker 1: totally agree with you, because he's a proponent of relational
17:17
Speaker 1: quantum mechanics, which says that the collapse is relative, it
17:21
Speaker 1: depends on who's doing the observing. Carlo would say that
17:24
Speaker 1: the cat collapses the way function, but for us outside
17:27
Speaker 1: the box, it's not yet collapsed. That this question of
17:30
Speaker 1: whether or not you are collapsed is everything relative between
17:33
Speaker 1: an observer and the observed, and not everybody has to
17:36
Speaker 1: agree on it. The same way we don't have to
17:38
Speaker 1: agree about velocity, because you can have different velocities for
17:42
Speaker 1: different objects, he thinks, and relational quantum mechanics suggests that
17:46
Speaker 1: collapse is not a universal thing, that you don't have
17:49
Speaker 1: to collapse for everybody. You can only collapse for some
17:51
Speaker 1: observers and not yet for others. M I see. It
17:54
Speaker 1: seems so like philosophy Option one is that it's collapse
17:58
Speaker 1: for the cat. The cat knows it's alive or dead,
18:00
Speaker 1: but for us it's alive and did that's philosophy option one.
18:04
Speaker 1: Philosophy option B or two is that nobody knows. Right,
18:08
Speaker 1: it's like it's alive and dead for everybody, even for
18:11
Speaker 1: the dead cat. That's right. So relational quantum mechanics would
18:14
Speaker 1: say the cat has collapsed the wave function, but we
18:16
Speaker 1: have not. Copenhagen sort of orthodox quantum mechanics doesn't even
18:20
Speaker 1: really have an agreed upon answer. Essentially, how you define
18:23
Speaker 1: the difference between what collapses and what doesn't is something
18:27
Speaker 1: people agree on for every experiment. It's like, let's call
18:30
Speaker 1: this the observer or let's not call that the observer.
18:32
Speaker 1: It's even fuzzier than like not to find. It's like,
18:34
Speaker 1: you know, let's just have a consensus for everything and
18:37
Speaker 1: define where this cut is between quantum and classical. And
18:40
Speaker 1: so even people who believe in Copenhagen might disagree about
18:43
Speaker 1: how to interpret this experiment. Some might say, look, the
18:46
Speaker 1: cat is a classical object. It collapses the way of function,
18:49
Speaker 1: there's no question. And other people might say, I just
18:51
Speaker 1: view the whole box is a quantum object, and the
18:53
Speaker 1: cat is just like a big quantum object and it's
18:55
Speaker 1: not yet collapsed until we open it. So even people
18:58
Speaker 1: who believe in Copenhagen interpret, I think, would disagree about
19:01
Speaker 1: what's happening in this experiment. Well, I feel like maybe
19:04
Speaker 1: there's an option see for philosophy in the philosophy here,
19:07
Speaker 1: which is kind of this idea of the quantum multiverse, right,
19:10
Speaker 1: like maybe nothing ever collapses at all, Like maybe there's
19:14
Speaker 1: no such thing as collapse, and things just kind of
19:17
Speaker 1: stay uncertain for everyone forever, and you get all these
19:20
Speaker 1: different multiple universes, right, like maybe the cat is alive
19:24
Speaker 1: and dead inside the box, and we us outside of
19:27
Speaker 1: the box. There are two universes, one in which if
19:30
Speaker 1: I open the box, it's going to be alive, and
19:32
Speaker 1: one which if I open the box is going to
19:34
Speaker 1: be dead, and so we are also kind of in
19:35
Speaker 1: a state of superposition. Yeah. Absolutely, And that's the many
19:39
Speaker 1: worlds interpretation of quantum mechanics. So Sean Carroll would probably
19:42
Speaker 1: agree with you. The question there is when does the
19:44
Speaker 1: universe split. Does it split when the cat is looking
19:47
Speaker 1: at the atom with a Harry eyeball wondering if it's
19:49
Speaker 1: about to kill it, or when you open the box
19:51
Speaker 1: and observe it. But you're right, in this many worlds view,
19:54
Speaker 1: there is no collapse. It says. Collapse is nonsense. It's
19:57
Speaker 1: not consistent with the Shortener equation, it's not consistent with
19:59
Speaker 1: every anything we know about quantum mechanics. That information is
20:02
Speaker 1: preserved because it's collapsed, like violates the conservation of quantum information.
20:06
Speaker 1: It makes no sense mathematically, and so they say, let's
20:09
Speaker 1: just have the shorting your equation dictate everything. And what
20:12
Speaker 1: happens when you observe something as the wave function gets
20:14
Speaker 1: two branches, one for each slice of them multiverse, and
20:17
Speaker 1: now you're in one of them, so you only see
20:19
Speaker 1: one and not the other. I've always found that a
20:20
Speaker 1: little bit unsatisfying because it doesn't really answer the question
20:23
Speaker 1: of why you're in one of those branches and not
20:25
Speaker 1: the other branches. You're supposed to believe those other branches
20:28
Speaker 1: are at the same philosophical level as yours, even though
20:31
Speaker 1: you're in this one. But mathematically it's a very pretty view,
20:36
Speaker 1: all right. Then what's the answer for Niels and Jacob then,
20:38
Speaker 1: is that there's a superposition of answers here and they're
20:42
Speaker 1: all true and false at the same time. Yeah. Absolutely,
20:45
Speaker 1: And there's even philosophy option D, which is that there
20:48
Speaker 1: is no randomness. Right. Boemian mechanics believes the quantum mechanics
20:51
Speaker 1: isn't even random at all. It's deterministic, and either the
20:55
Speaker 1: cat is dead or it is alive, and it was
20:57
Speaker 1: determined before anything happened that went into the box. Maybe
21:00
Speaker 1: even by the Big Bang. So the answer for Neils
21:03
Speaker 1: and Jacob is that this is not something we're going
21:05
Speaker 1: to answer today on the podcast. Nobody knows where it
21:07
Speaker 1: really happens. None of our views of quantum mechanics really
21:11
Speaker 1: answered this question satisfactorily. No, no, no, Daniel, let's just
21:14
Speaker 1: collapse the question itself and let's just pick an answer,
21:17
Speaker 1: and that's the universe that we live in, and a
21:18
Speaker 1: quarter of the time will be right. Well, then I
21:20
Speaker 1: want the cat to be alive so that it can
21:21
Speaker 1: survive and then later get eaten by coyotes. I don't
21:27
Speaker 1: know what's worse to die in a physic experiment or
21:30
Speaker 1: to be eaten by coyotes. Well, you know, my cats
21:32
Speaker 1: had the option to be stuck in the box of
21:34
Speaker 1: my home or to live outside and enjoy the outdoor
21:38
Speaker 1: life of a cat, and that's what they chose, and
21:40
Speaker 1: they paid the price. Wow, now we're getting into free
21:43
Speaker 1: will and feline free will. We're gonna eat the not
21:46
Speaker 1: just katies, some kind of philosopher in here too. And
21:48
Speaker 1: for those of you worried about outdoor birds, we also
21:51
Speaker 1: worried about them, and we put very loud bells on
21:53
Speaker 1: the cats. Though that might not have been helpful when
21:55
Speaker 1: it came to the coyotes. All right, well, I think
21:57
Speaker 1: that's the as for Neils and Jacob, which is at
22:00
Speaker 1: it kind of depends and the very nature, the philosophical
22:04
Speaker 1: nature of the universe. It could be that they're right,
22:06
Speaker 1: that the cat collapses inside of the box and we
22:09
Speaker 1: just have to open it to find out what happened.
22:11
Speaker 1: It could be that the cat is alive and dead
22:13
Speaker 1: inside of the box and we just don't know it.
22:16
Speaker 1: And it could be that we're all in some kind
22:18
Speaker 1: of multiverse where every decision gets played out in a
22:21
Speaker 1: whole different plane of existence. That's right. If you want
22:23
Speaker 1: to go further down the philosophical rabbit hole, I recommend
22:25
Speaker 1: you read about Vigner's friends experiment, where you have people
22:29
Speaker 1: inside the box, and then the whole experiment inside another box,
22:32
Speaker 1: and then that whole experiment inside another box, etc. Etc. Oh, man,
22:36
Speaker 1: now you're gonna experiment with rabbits and humans. Let's not
22:41
Speaker 1: open that box. All right, Well, thank you Nielson Jacob
22:43
Speaker 1: for this question. Let's get to some of our other
22:46
Speaker 1: questions about the heat death of the universe and also
22:49
Speaker 1: dark matter and parallel universes. But first, let's take a
22:53
Speaker 1: quick break. All right. We are answering listener questions here
23:08
Speaker 1: today from curious listeners who have amazing questions. One question
23:13
Speaker 1: we didn't quite answer in the last segment, Daniel was
23:15
Speaker 1: about Truedinger's cat, which is, what's the origin of Trudinger's cat?
23:19
Speaker 1: The Truedinger really have a cat? Schroedinger is actually quite
23:23
Speaker 1: a colorful figure, and now a controversial one. It's not
23:27
Speaker 1: really that nice a dude. It turns out the kind
23:29
Speaker 1: of things he got into is not the kind of
23:31
Speaker 1: things we should dig into on a family friendly podcast.
23:33
Speaker 1: So I don't know what that says about the likelihood
23:36
Speaker 1: that he was nice to his cat. But I guess
23:37
Speaker 1: maybe what I'm asking is like, did he come up
23:39
Speaker 1: with this example of the Schulinger's cat maybe based on
23:42
Speaker 1: a cat you may or may not have had, or
23:44
Speaker 1: did somebody else come up with the cat in the
23:46
Speaker 1: box idea and just assigned it the Schroedinger. Oh no,
23:49
Speaker 1: it was very much Schroedinger's example. Yes, it is his
23:53
Speaker 1: idea of the cat in the box. M interesting, and
23:56
Speaker 1: he naended my cat. He's a here's an experiment, it's
24:00
Speaker 1: my cat. I don't know, maybe he hated cats, and
24:02
Speaker 1: that's why I put a cat in the boxing's trying
24:03
Speaker 1: to protect theoretical rabbits and theoretical dogs. I don't know,
24:06
Speaker 1: oh Man physicists or I just get to a second
24:10
Speaker 1: question here, and this one comes from Mattis. Hello, Daniel,
24:13
Speaker 1: and I have a question for the podcast. If all
24:16
Speaker 1: energy a movement stops at the heat that of the universe,
24:18
Speaker 1: which things still be moving at a quantum level? Thanks
24:22
Speaker 1: for answering, all right, nice and brief. I like that
24:25
Speaker 1: He's like, here's my question. Bam. He's got that very
24:29
Speaker 1: efficient Dutch attitude. He probably recorded this wall he was
24:32
Speaker 1: on his bicycle writing past some windmills, probably next to
24:36
Speaker 1: assume tulips eating at m cheese. I've seen the Dutch
24:39
Speaker 1: folks do things on bikes I've never imagined, like they
24:42
Speaker 1: bike away from the train station with a rolling suitcase
24:45
Speaker 1: next to them on the bicycle. It's amazing. Nice. Well,
24:48
Speaker 1: Mattie's question here is about the heat death of the universe,
24:52
Speaker 1: and I guess what it really means and whether or
24:54
Speaker 1: not quantum things still apply at the end of the
24:57
Speaker 1: universe if it dies by heat death. Yeah, this is
24:59
Speaker 1: a great question and one that I'm very hambid I
25:01
Speaker 1: talked about on the podcast today because there's a common
25:04
Speaker 1: misconception about what the heat death of the universe is.
25:07
Speaker 1: The heat death of the universe does not mean when
25:09
Speaker 1: everything is zero temperature and totally frozen at absolute zero.
25:14
Speaker 1: The heat death of the universe instead means when all
25:16
Speaker 1: the heat is smoothed out, when everything is the same temperature,
25:20
Speaker 1: when there's no more energy flow in the universe, basically
25:23
Speaker 1: when everything is in perfect thermodynamic equilibrium. Let's take a
25:27
Speaker 1: step back here and maybe talk about what is the
25:30
Speaker 1: heat death of the universe. It's it's kind of an
25:31
Speaker 1: idea about how the universe might end, right, and it
25:35
Speaker 1: comes from this idea that if the universe keeps expanding
25:38
Speaker 1: and expanding and further and further, eventually it's going to
25:40
Speaker 1: get to a point which, you know, some people might
25:43
Speaker 1: call it the end of the universe. Some people might
25:44
Speaker 1: just call it like the universe getting stuck, but they
25:47
Speaker 1: call it the heat death of the universe, even though
25:49
Speaker 1: it has nothing to do well, it won't be very hot,
25:53
Speaker 1: but it does have something to do with heat because
25:55
Speaker 1: it is a thermodynamic analysis and it's basically just trying
25:59
Speaker 1: to predict the future of the universe. You're right, because
26:01
Speaker 1: something we notice in the universe is that energy likes
26:04
Speaker 1: to even itself out. You have a hot spot on
26:07
Speaker 1: your counter, that energy is going to bleed out to
26:09
Speaker 1: the rest of your counter, and it's going to even out.
26:11
Speaker 1: You put an ice cube in a hot cup of coffee,
26:12
Speaker 1: you come back five minutes later, you don't still have
26:14
Speaker 1: an ice cube. You don't have half the coffee being
26:17
Speaker 1: hot and half of it being cold. You have it
26:19
Speaker 1: all about the same temperature. And so what we notice
26:22
Speaker 1: in the universe is that things tend to basically smooth
26:25
Speaker 1: themselves out in terms of temperature and in terms of energy.
26:28
Speaker 1: And so if you extrapolate that really far in the future,
26:31
Speaker 1: then you end up with universe that's sort of smooth
26:34
Speaker 1: that way, where there's no hot spots and no cold spots.
26:37
Speaker 1: And that would be a bummer because we kind of
26:39
Speaker 1: rely on energy flow to do most of the things
26:41
Speaker 1: we do, like living. I see. So it's kind of
26:44
Speaker 1: the idea that if you just leave the universe out
26:47
Speaker 1: on your coffee table, eventually, right now it has a
26:50
Speaker 1: lot of hot spots and cold spots. Right there's the
26:53
Speaker 1: Sun that's really hot. There's the center of the galaxy
26:55
Speaker 1: that's really hot, and some pots spots that are really cold.
26:57
Speaker 1: Like if you leave your universe out on the table
26:59
Speaker 1: for or you know, a few trillions of years, eventually
27:03
Speaker 1: it's all going to smooth out and just be like
27:05
Speaker 1: a room temperature universe. Yeah, exactly. It's sort of like
27:08
Speaker 1: the battery runs out on the universe, you know, batteries
27:11
Speaker 1: and any other sort of technique we have to extract
27:14
Speaker 1: energy from the universe relies on energy flowing, right, maybe
27:18
Speaker 1: water is flowing downhill, or steam is rising to turn
27:21
Speaker 1: a turbine or something that relies on energy flows, and
27:24
Speaker 1: so if the energy is not flowing anymore, you can't
27:27
Speaker 1: extract any more energy from the universe. So it's sort
27:29
Speaker 1: of like if you put ice in your drink and
27:31
Speaker 1: you come back later, it's all the same temperature. You
27:34
Speaker 1: can't do anything with that because there's no energy moving around.
27:37
Speaker 1: Even if there still is energy inside that drink, there's
27:41
Speaker 1: no useful energy. So there's a distinction there between useful
27:44
Speaker 1: energy and actual energy temperature in the universe. You can
27:48
Speaker 1: get to a place where the universe is totally smooth,
27:51
Speaker 1: everything is the same temperature, so you can't do anything
27:54
Speaker 1: without that temperature actually being zero, right, And maybe just
27:57
Speaker 1: for our listeners, maybe paint a picture of how that happens.
28:00
Speaker 1: Like right now, we have hot spots, like, for example,
28:02
Speaker 1: the Sun or like the core of the Earth. It's
28:04
Speaker 1: pretty hot. But I guess I should just like run
28:06
Speaker 1: the clock forward to what happens. I guess eventually the
28:09
Speaker 1: Sun will go out, they'll run out of fuel, and
28:13
Speaker 1: then it'll be sit there hot and then but then
28:15
Speaker 1: eventually all that heat will sort of radiate out into
28:18
Speaker 1: the universe, right, and it will just get cold. That's right.
28:21
Speaker 1: There's a lot of energy stored in the Sun, but
28:23
Speaker 1: that energy is not going to be stored there forever.
28:25
Speaker 1: It's getting released. That's what the Sun is doing. It's
28:27
Speaker 1: blasting its energy out into the rest of the universe.
28:30
Speaker 1: But the Sun will not last forever, and so that
28:33
Speaker 1: energy will fly out in terms of photons and get
28:35
Speaker 1: absorbed by other stuff. But energy likes to move around.
28:38
Speaker 1: If those photons heat something up, then that thing will
28:40
Speaker 1: also emit photons on its own. It will emit black
28:43
Speaker 1: body radiation to sort of heat up the stuff around it.
28:46
Speaker 1: So the energy in the whole universe just sort of
28:48
Speaker 1: spreads out. And this is a basic rule of thermodynamics.
28:52
Speaker 1: It's because entropy has to increase in the universe, and
28:55
Speaker 1: the way to increase entropy is to spread the energy
28:58
Speaker 1: out because it increases like the number of possible micro
29:01
Speaker 1: states you can have going on inside the thing, like
29:04
Speaker 1: for example, the Earth, Like the Earth is pretty warm
29:06
Speaker 1: at the center now, but eventually, over time it's just
29:08
Speaker 1: going to turn into a cold rock, and all that
29:11
Speaker 1: energy is going to go out into space and maybe
29:13
Speaker 1: hit other things. But eventually those think everything's going to
29:16
Speaker 1: kind of reach room temperature. Yeah, not quite room temperature,
29:18
Speaker 1: like comfortable temperature for us, but sort of like universe
29:22
Speaker 1: room temperature, which is going to be like a couple
29:24
Speaker 1: degrees above absolute zero. And you might wonder, like, how
29:27
Speaker 1: is the Earth going to lose that energy? It's not
29:29
Speaker 1: glowing like the sun, But actually it is right, everything
29:33
Speaker 1: is glowing. The Earth actually is glowing, just not in
29:35
Speaker 1: the visible light. If you looked at the Earth with
29:38
Speaker 1: an infrared camera, you would see it glowing just in
29:40
Speaker 1: a spectrum that's too long wavelength for our eyeballs to see.
29:45
Speaker 1: So we can see other planets out there glowing with
29:47
Speaker 1: a James Web infrared telescope. That's one way that they
29:50
Speaker 1: can discover exoplanets, for example. So everything out there in
29:53
Speaker 1: the universe is shedding its energy, and as time goes
29:56
Speaker 1: on and energy tends to smooth out more and more
29:59
Speaker 1: and more, and the heat death is just extrapolate that
30:02
Speaker 1: really really far out in the future where all the
30:05
Speaker 1: energy has managed to leak out and spread around. Yeah,
30:08
Speaker 1: so then now you kind of have to imagine the
30:10
Speaker 1: future of the universe where you know, the Earth is cold,
30:13
Speaker 1: the Sun has gone out and it's cold. Everything's cold.
30:16
Speaker 1: All the stars in the entire universe are cold, and
30:19
Speaker 1: now maybe even like pulverized, and it's all sort of
30:22
Speaker 1: this kind of basically super cold place. There's no energy
30:26
Speaker 1: stored in any one place for there to spark a
30:29
Speaker 1: new sun for example. Right, that's right, But even a
30:31
Speaker 1: cold Earth does have some energy stored inside of it.
30:34
Speaker 1: So you've got to go even deeper into the future
30:37
Speaker 1: when everything falls into the supermassive black holes at the
30:40
Speaker 1: hearts of galaxies and then is radiated back out by
30:43
Speaker 1: a Hawking radiation. So now everything has basically been converted
30:47
Speaker 1: to whatever is inside a black hole and then radiated
30:49
Speaker 1: back out sort of like fed through these cosmic shredder.
30:53
Speaker 1: Now the whole universe is just sort of bathed in
30:55
Speaker 1: Hawking radiation, so there's no like hard lumps of cold
30:59
Speaker 1: Earth or any thing I see. Eventually, even the cold
31:01
Speaker 1: Earth and the cold Sun will collapse, right because orbits
31:04
Speaker 1: don't last forever. Eventually everything's going to collapse, the galaxy
31:07
Speaker 1: of cold stars and planets, it's all going to collapse
31:09
Speaker 1: into a black hole. But then you're saying the black
31:11
Speaker 1: hole evaporates at some point, even if it's super gigantic massive,
31:15
Speaker 1: it's going to evaporate eventually right into what light. Well,
31:19
Speaker 1: Hawking radiation can be light, but it can also be
31:21
Speaker 1: other particles. It's really fascinating because it's sort of democratic,
31:24
Speaker 1: meaning it can create any kind of particle that's out there,
31:28
Speaker 1: which is a really awesome kind of tool because you
31:30
Speaker 1: want to study like what particles are out there in
31:32
Speaker 1: the universe. You can just go like observe the edge
31:34
Speaker 1: of a black hole and it'll basically show you all
31:36
Speaker 1: of nature's menu, which is amazing. Though that's technically quite
31:39
Speaker 1: difficult to do, and we've never actually observed hawking radiation.
31:42
Speaker 1: But in theory, all black holes, even the really really
31:45
Speaker 1: big ones, do emit hawking radiation because they have an entropy,
31:49
Speaker 1: they have a temperature, and everything in the universe with
31:51
Speaker 1: a temperature does emit some kind of radiation. And so
31:55
Speaker 1: then if you keep fast forwarding, these black holes will
31:58
Speaker 1: evaporate out, and so now universe is what just filled
32:01
Speaker 1: with flying photons and tiny matter particles. And the idea
32:07
Speaker 1: is that everything is perfectly spread out, so there's no
32:09
Speaker 1: like hot clumps of matter, there's no overdensities, there's no
32:13
Speaker 1: under densities. This is sort of like the very deep future.
32:16
Speaker 1: And we're not talking about like twenty fifty or five
32:19
Speaker 1: thousand years from now, or ten million years from now
32:22
Speaker 1: or ten trillion years from now. We're talking so far
32:26
Speaker 1: deep in the future it's hard to even really wrap
32:28
Speaker 1: your mind around the time we're talking about. It's like
32:31
Speaker 1: ten to the one hundred years in the future. But
32:34
Speaker 1: I guess maybe a question is if black holes do
32:36
Speaker 1: evaporate into matter particles, when of these matter particles flying
32:40
Speaker 1: around eventually like stick together or be attracted to each
32:43
Speaker 1: other by gravity, and then then you get more stuff,
32:46
Speaker 1: and then suddenly you have like new planets and new stars.
32:50
Speaker 1: So this is really the hard I think of Matthias's question, Right,
32:52
Speaker 1: it's like, what's going on with that stuff? Do you
32:54
Speaker 1: still have quantum frothiness or not? And you still do
32:58
Speaker 1: have particles and they are still flying around own and
33:00
Speaker 1: photons will still interact with electrons, right, Just like when
33:03
Speaker 1: your drink cools down to an even temperature because you
33:06
Speaker 1: put ice in it, you still have particles in that
33:09
Speaker 1: drink that are moving around. There's still motion, there's still
33:11
Speaker 1: interactions that are happening. It's not like everything is stuck
33:14
Speaker 1: and frozen. It's just that everything is smooth and even
33:17
Speaker 1: so nothing can get started, Like gravity in order to
33:20
Speaker 1: get started requires some overdensity. If you had a perfectly
33:23
Speaker 1: smooth universe, gravity couldn't do anything. Gravity can accentuate lumps,
33:27
Speaker 1: but it can't start lumps. Right, Well, you're assuming you
33:31
Speaker 1: start with like a universe where every particle standing still
33:34
Speaker 1: and it's a perfectly equal distance from all other particles.
33:38
Speaker 1: But that's not kind of like it. It seems very
33:40
Speaker 1: unlikely that we'll get to that point, you know what
33:42
Speaker 1: I mean? Like, if there are black holes evaporating, wouldn't
33:44
Speaker 1: they have you know, wouldn't the particles have some velocity
33:47
Speaker 1: coming out of the black hole, and then wouldn't those
33:49
Speaker 1: mixed with other things, and you know, wouldn't gravity eventually
33:53
Speaker 1: take hole somewhere? Like what's the scenario in which we
33:55
Speaker 1: suddenly everything suddenly freezes and is at the same distance
33:58
Speaker 1: from each other everywhere? Right, that's not the picture that
34:00
Speaker 1: we're painting. We are painting the picture where things are
34:02
Speaker 1: still flying around and still frothing. And so what thermodynamic
34:05
Speaker 1: says is that the most likely outcome is that things
34:08
Speaker 1: stay smooth. But this is just statistics. It just says
34:11
Speaker 1: it's the most likely. There's, of course, quantum randomness. Things
34:14
Speaker 1: can fluctuate. It's quantum mechanics, and so things can accidentally
34:18
Speaker 1: bump into each other and start to form a hot, spotted,
34:20
Speaker 1: denser spot that then collects stuff. Right, We actually talked
34:24
Speaker 1: about the probability of this kind of thing happening in
34:26
Speaker 1: our Boltspin Brain episode, Like, if you had a perfectly
34:29
Speaker 1: smooth universe, what's the possibily fluctuating an atom or a
34:33
Speaker 1: star or a brain out of that sort of quantum
34:35
Speaker 1: frothing void. Now in our universe, we got a head start,
34:39
Speaker 1: because we had inflation. We had tiny little quantum fluctuations
34:43
Speaker 1: that got blown up to much bigger fluctuations that then
34:46
Speaker 1: gravity you could grab a hold of. But yes, absolutely,
34:49
Speaker 1: even in this heat death scenario, you could have random
34:52
Speaker 1: quantum fluctuations that lead to overdensities and then do lead
34:55
Speaker 1: to the formation of structure. Thermodynamics doesn't say it's impossible.
34:59
Speaker 1: It just says it's un likely because that would effectively
35:01
Speaker 1: be decreasing entropy. Well, I wonder if in a way,
35:04
Speaker 1: gravity is kind of like the anti entropy. You know,
35:07
Speaker 1: like I understand this theory of entropy and that if
35:09
Speaker 1: you had a perfectly smooth liquid it wouldn't start collapsing.
35:14
Speaker 1: But I feel like maybe gravity is there to counteract that, right, Like,
35:18
Speaker 1: first of all, you need an infinitely sized universe for
35:22
Speaker 1: that to work, otherwise gravity would bring everything together. But
35:25
Speaker 1: I feel like, yeah, I feel like gravity somehow counteracts
35:29
Speaker 1: this idea that entropy always wins. Well, gravity definitely obeys
35:32
Speaker 1: the same laws of thermodynamics. I mean, gravity also wants
35:36
Speaker 1: things to like roll downhill. It doesn't like things having
35:39
Speaker 1: a lot of potential energy, for example. It likes to
35:42
Speaker 1: balance things. So I think it follows the same rules.
35:44
Speaker 1: Black holes, for example, which are gravitationally very dense objects,
35:47
Speaker 1: do contain an enormous amount of entropy. Entropy is not
35:51
Speaker 1: just like order versus disorder, right, It's about how many
35:55
Speaker 1: ways you can arrange the microphysical states and represent the
35:58
Speaker 1: same macroscopic object. Yeah, I guess it does get a
36:01
Speaker 1: little bit philosophical. But just to answer mat Tis this question,
36:04
Speaker 1: I guess the answer is. What you're saying is that, yes,
36:07
Speaker 1: even in a heat death of the universe, things are
36:09
Speaker 1: going to be moving at the quantum level, which maybe
36:12
Speaker 1: we'll end up kind of breaking the heat death of
36:14
Speaker 1: the universe exactly. There will always be quantum dancing. These
36:17
Speaker 1: quantum fields can never go down to zero energy. There
36:20
Speaker 1: will always be some energy and so some fluctuations, and
36:23
Speaker 1: so it's possible for the universe to get totally smooth
36:26
Speaker 1: and ten to the one hundred years and then fluctuate
36:28
Speaker 1: some new spot around which structure forms again. And some
36:32
Speaker 1: people even think maybe that's the story of our universe. Yeah. Well,
36:35
Speaker 1: I think you're saying two things. One is that they
36:37
Speaker 1: maybe things fluctuate and maybe they'll start clumping again together.
36:40
Speaker 1: But you're also saying maybe they'll fluctuates so crazily like
36:43
Speaker 1: suddenly the universe will just going to flip over and
36:46
Speaker 1: start over again. Yeah, randomly exactly, But we all have
36:49
Speaker 1: to wait ten to the one hundred years to find out.
36:51
Speaker 1: I think I'll just watch the recap episode for that.
36:54
Speaker 1: Who has time to binch that? Make sure you're not
36:57
Speaker 1: watching it while you're on your bicycle. All right, let's
36:59
Speaker 1: get to our last question here about dark matter and
37:02
Speaker 1: parallel universes. But first let's take a quick break. All right.
37:19
Speaker 1: We're answering listener questions about all kinds of things in
37:23
Speaker 1: the universe, including cats, rabbits, and ethically questionable physicists, at
37:29
Speaker 1: least in thought experiments. And our last question here comes
37:32
Speaker 1: from Craig, who hails from Ontario. Hi, Danielle and Horry,
37:36
Speaker 1: This is Craig from Ontario, Canada. Thanks for such an
37:39
Speaker 1: awesome pod. I was wondering about dark matter. Is there
37:43
Speaker 1: any chance that what we experience is dark matter in
37:46
Speaker 1: our universe could actually be stuffed with mass in an
37:50
Speaker 1: adjacent universe lending its gravity to us. Thank you guys
37:54
Speaker 1: for the pod, and I wish you both all the best.
37:56
Speaker 1: Whoa mind blown Craig just blue my mind. Also, I
38:01
Speaker 1: think I heard a cat in the background of Craig's recording.
38:04
Speaker 1: Did you really think I did? I think there's a
38:06
Speaker 1: meal there. Or maybe you're just hearing it in your head, Daniel,
38:09
Speaker 1: maybe your cats are haunting you. I'm just saying I'm
38:13
Speaker 1: looking for new subjects for thought experiments, and Craig, maybe
38:15
Speaker 1: you want to volunteer thought experiment or psychological experiments. Can't
38:20
Speaker 1: it be both? I guess all psychological experiments are thought experiments.
38:24
Speaker 1: That's right, And I'm gonna push back and defend physicist
38:26
Speaker 1: a little bit there. We do have a lot of
38:28
Speaker 1: crazy thought experiments, like a person in a box out
38:31
Speaker 1: in deep space and you got to wonder, how did
38:33
Speaker 1: this person sign a consent for him? Is somebody going
38:36
Speaker 1: to rescue them? Or they do they have a bathroom
38:38
Speaker 1: and water and this kind of stuff. But that's why
38:39
Speaker 1: these are just thought experiments and not experiments anybody's ever
38:43
Speaker 1: actually going to do right, right, Like you would never
38:46
Speaker 1: like build a giant ring Niva, and you know, you know,
38:50
Speaker 1: shooting things in incredible energy and then put people on
38:52
Speaker 1: top of it, or put an exco city or anything
38:54
Speaker 1: like that, right, that would be totally ethically you're RESPONSI, well,
38:57
Speaker 1: for example, we would never accelerate cats near the speed
38:59
Speaker 1: of light and collide them. Absolutely not. But protons don't
39:03
Speaker 1: have the same rights. You're categorically against them. But anyways, Craig,
39:07
Speaker 1: whether or not you have a cat, you have an
39:09
Speaker 1: interesting question here about dark matter adjacent universes, which is
39:13
Speaker 1: an interesting phrase, and so I think his question, and
39:16
Speaker 1: I have to say, I think I told you this
39:19
Speaker 1: theory a long time ago. I remember we were driving
39:22
Speaker 1: somewhere for our book tour and I was like, hey, Daniel,
39:24
Speaker 1: I have a theory about dark matter, and I think
39:26
Speaker 1: it was exactly this theory, which means Craig is a genius,
39:31
Speaker 1: or it means Craig should be a cartoonist. Yeah, maybe
39:35
Speaker 1: maybe you'll find more success in that like I did.
39:38
Speaker 1: But yeah, it's kind of an interesting question, like because
39:40
Speaker 1: we don't know there's dark matter in this universe. We
39:42
Speaker 1: notice it's there, but we don't know what it is.
39:45
Speaker 1: And so his idea, or I guess I should say
39:48
Speaker 1: our idea, the Craig cam theory about dark matter, that
39:54
Speaker 1: maybe what we feel as dark matter is actually like
39:57
Speaker 1: mass in a parallel universe at some how leaking over
40:01
Speaker 1: that somehow we can see through gravity. M Yeah, and
40:05
Speaker 1: I love this idea. It's really clever. But let's take
40:08
Speaker 1: a step back because you said there's dark matter in
40:10
Speaker 1: our universe. But I think Craig's question is asking us
40:13
Speaker 1: to reconsider that, because really, what do we observe. We
40:16
Speaker 1: observe gravity. We see something is contributing gravity to how
40:22
Speaker 1: galaxies spin, and how the large scale structure the universe formed,
40:26
Speaker 1: and how the ripples in the early universe plasma were
40:29
Speaker 1: created and propagated. What we see is gravity that we
40:32
Speaker 1: cannot explain. We attribute that to dark matter. We say
40:35
Speaker 1: there must be some missing mass in our universe we
40:37
Speaker 1: never observed before. It's basically what we say dark matter is.
40:41
Speaker 1: But what we actually observe is the gravity. So I
40:44
Speaker 1: think Craig's question is, like, how do we know that's
40:46
Speaker 1: mass in our universe and not just gravity leaking in
40:49
Speaker 1: from some other universe where that mass is right? Right,
40:52
Speaker 1: Although you're kind of parsing hare is here, because like
40:55
Speaker 1: if there is another universe and leaking into ours, then
40:57
Speaker 1: there's like overlap, right, I mean that universe is partly
41:01
Speaker 1: in our universe, right, and so it's technically kind of
41:05
Speaker 1: in our universe too, exactly. And that is the hair
41:07
Speaker 1: I think we are splitting here today, which is what
41:09
Speaker 1: does it mean to be in an adjacent universe? Right?
41:13
Speaker 1: If this mass is in another universe and we don't
41:15
Speaker 1: interact with it except through gravity, is it really in
41:18
Speaker 1: another universe? If we can interact with it, is it
41:21
Speaker 1: in another universe? I mean, I'm interacting with my chair
41:23
Speaker 1: and my desk right now. So we say that they're
41:25
Speaker 1: part of the universe. Could you say they're in another
41:28
Speaker 1: universe but we can still somehow interact with them. I
41:31
Speaker 1: don't know. I would say that things in another universe
41:34
Speaker 1: are things you cannot interact with. And so if we're
41:36
Speaker 1: interacting with this stuff, if we're feeling it's gravity, then
41:39
Speaker 1: it's in our universe. And that's not like a physics
41:42
Speaker 1: argument or philosophy argument. It's really just sort of like semantics.
41:45
Speaker 1: It's like, what do you call a universe? Yeah, and
41:48
Speaker 1: we never argue semantics here on this podcast. Well, I
41:52
Speaker 1: think there's kind of two interesting ideas here in Craig's question, right,
41:55
Speaker 1: Like one like maybe in our universe there's a whole
41:59
Speaker 1: other universe on top of us of particles that our
42:02
Speaker 1: particles don't interact with. There's like planets and suns and
42:05
Speaker 1: stars and photons and things like that that just don't
42:08
Speaker 1: like interact with us, our kind of particles. So that's
42:11
Speaker 1: why we don't see it, but they're there. They're like
42:13
Speaker 1: it's like a ghost universe on top of ours, but somehow,
42:16
Speaker 1: like the gravity, we do kind of feel its presence.
42:19
Speaker 1: It's gravity, and that's what maybe we see as dark matter.
42:22
Speaker 1: Then there's the other idea that maybe it is another universe,
42:25
Speaker 1: like maybe it's the multiverse or the quantum multiverse or
42:29
Speaker 1: you know these quantum foam bubble universes. It would be
42:31
Speaker 1: considered by some as a totally different universe that somehow
42:34
Speaker 1: leaks into hours. And so those are kind of two
42:37
Speaker 1: different ideas, right, that's like maybe we share the same
42:40
Speaker 1: space or maybe we don't share the same space. Yeah,
42:42
Speaker 1: those are two different ideas and they're really fun. The
42:44
Speaker 1: first one I think is beautiful because it's sort of
42:47
Speaker 1: our current conception of the universe, suggesting that there is
42:51
Speaker 1: all this matter out there that we can't interact with
42:53
Speaker 1: except through gravity. Gravity is like the great unifier because
42:56
Speaker 1: it interacts with everything. Anything that has mass or energy,
43:00
Speaker 1: regardless of any other quantum properties, it has gravity will
43:03
Speaker 1: talk to it. So if there's anything else out there
43:06
Speaker 1: in the universe, even if we can't interact with it,
43:08
Speaker 1: even if it has like weird particles and weird forces
43:11
Speaker 1: that are not overlapping at all with ours, we would
43:14
Speaker 1: know it because of its gravity. And you can sort
43:16
Speaker 1: of think of that as like another universe, as you say,
43:18
Speaker 1: like a ghost universe. You can imagine all these particles
43:21
Speaker 1: out there with new dark forces and dark charges and
43:24
Speaker 1: dark physics and doing their dark stuff, maybe making dark
43:27
Speaker 1: planets or completely different emerging dark phenomena that we can't
43:31
Speaker 1: even imagine because fundamentally they're very different physics at their core,
43:35
Speaker 1: and how that bubbles up to creating ice cream or
43:38
Speaker 1: not depends on that fundamental physics. So even that is
43:41
Speaker 1: fascinating to me. That's sort of like being another universe
43:44
Speaker 1: on top of ours, because it says that we are
43:46
Speaker 1: only experiencing a slice of this universe, and we already
43:50
Speaker 1: know that's true. We already know there's lots of stuff
43:52
Speaker 1: out there. We can't see neutrinos and stuff, though we
43:54
Speaker 1: can detect them through some quantum interactions. But gravity is
43:58
Speaker 1: this awesome way to say if there's something else, anything
44:00
Speaker 1: else in our space, then we will see it. And
44:03
Speaker 1: so the other idea which you bring up is like,
44:05
Speaker 1: maybe there's another universe that gravity can somehow interact with,
44:09
Speaker 1: Like maybe there is other matter, and if it were
44:12
Speaker 1: in our space, we would interact with it and we
44:14
Speaker 1: would see it. Right, it is sort of normalish matter.
44:17
Speaker 1: It's just like in some other space. But yet gravity
44:20
Speaker 1: is connecting our space and their space. It's sort of
44:23
Speaker 1: like the other idea you proposed, And that's a little
44:26
Speaker 1: bit theoretically problematic because remember gravity is about space. Gravity
44:30
Speaker 1: says when you have mass in space, it bends, and
44:33
Speaker 1: so if this mass is bending our space, then it's
44:36
Speaker 1: sort of in our space. There's no other way for
44:40
Speaker 1: that mass to bend our space without being in our space.
44:44
Speaker 1: You're saying like, if there is another universe out there
44:46
Speaker 1: that's separate from ours, and I like that this you made,
44:49
Speaker 1: like if it were in our universe, we would interact
44:52
Speaker 1: with it. But it is in a different kind of
44:54
Speaker 1: space or phase or whatever, and so therefore it's another universe.
44:57
Speaker 1: But you're saying, like, if we do feel it somehow,
45:00
Speaker 1: and there is a connection which means you should lump
45:02
Speaker 1: both of our universe together into one word called the universe. Yeah, exactly,
45:07
Speaker 1: if it's bending our space, then it's in our space.
45:10
Speaker 1: By definition, it can't both be bending our space and
45:13
Speaker 1: not be in our space, right, Like if I take
45:16
Speaker 1: a tunnel from my house to your house, suddenly it's
45:19
Speaker 1: my house too, it's our house. I guess, let's part
45:26
Speaker 1: the legalism of that put all the work into the tunnel,
45:31
Speaker 1: I suppose. So there are other interesting wrinkles here though, because,
45:33
Speaker 1: for example, it's possible that gravity acts in ways different
45:37
Speaker 1: from all the other interactions. Like it might be that
45:40
Speaker 1: the universe has multiple dimensions, right the ways that we
45:44
Speaker 1: can move x, y, and z, there might be more
45:46
Speaker 1: of those, And one theory is that gravity can operate
45:49
Speaker 1: in those other dimensions and the other forces cannot. So
45:52
Speaker 1: it's possible there are other quantum objects and quantum forces
45:55
Speaker 1: that can operate in those other dimensions that we can't
45:59
Speaker 1: operate in. Gravity would be sort of unifying. It would
46:02
Speaker 1: still be in our universe, right, but we wouldn't be
46:04
Speaker 1: able to see them or interact with them, but they'd
46:06
Speaker 1: be moving through sort of like other dimensions instead of
46:09
Speaker 1: the three that we have. So I guess maybe it
46:11
Speaker 1: all depends on how you define the universe, right, I mean,
46:14
Speaker 1: physics came up with the cause of the word multiverse
46:17
Speaker 1: for kind of a reason, right, to describe kind of
46:19
Speaker 1: like a collection of mini universes. And there's a whole
46:23
Speaker 1: set of different multiverses as like a multi multiverse, but
46:26
Speaker 1: in all of them there's no way to interact. Like
46:29
Speaker 1: there's the quantum multiverse that we just talked about in
46:31
Speaker 1: terms of the Shooting verse cat Well, there's two different
46:33
Speaker 1: branches of the universe reflecting different possibilities, but the branches
46:37
Speaker 1: can never interact with each other gravity and one doesn't
46:39
Speaker 1: leaked into the other. There's the bubble multiverse that suggests
46:43
Speaker 1: the bubbles of normal space were popped out of inflationary matter,
46:47
Speaker 1: but these would be separated by inflating matter, so that'd
46:50
Speaker 1: be so far away we can never interact with them.
46:53
Speaker 1: And all these different multiverse theories, you cannot interact with
46:56
Speaker 1: the other universes in the multiverse. That's only something in
47:00
Speaker 1: a Marvel cinematic universe that is possible, and that all
47:03
Speaker 1: that stuff is real too anyways, Right, Well, it's making
47:07
Speaker 1: real money, that's for sure. Well, I think maybe the
47:11
Speaker 1: answer for Craig here to this question of whether dark
47:14
Speaker 1: matter is just stuff that we feel from another universe.
47:17
Speaker 1: I feel like the answer is, yes, it's possible it
47:20
Speaker 1: could be the case. But then a physicist like you,
47:24
Speaker 1: Daniel will come in and say, well, technically, if we're
47:26
Speaker 1: feeling it, then it's part of our universe, and sort
47:29
Speaker 1: of try to cancel out the question. I would say,
47:32
Speaker 1: if we're feeling it, it's in our universe. Yeah, absolutely,
47:35
Speaker 1: But I guess the main main idea is that it
47:38
Speaker 1: could be that dark matter is just kind of part
47:40
Speaker 1: of this whole set of things that exists out there
47:43
Speaker 1: that we just don't mostly notice. And I think the
47:46
Speaker 1: spirit of Craig's question is that there's the possibility of
47:49
Speaker 1: a much wider and broader kind of reality than the
47:52
Speaker 1: one we experience and that we think about. And that's
47:55
Speaker 1: the cool thing about dark matter and about gravity is
47:58
Speaker 1: that it lets us explore. It gives us a poor
48:00
Speaker 1: to everything that's out there in every part of our
48:02
Speaker 1: universe because gravity is universal, and so that's the really
48:07
Speaker 1: exciting thing about it to me is not only the
48:09
Speaker 1: universe could be very different from the universe we experience
48:12
Speaker 1: and we've imagined, but that we have a way to
48:15
Speaker 1: discover it and explore it. So gravity is really this
48:18
Speaker 1: wonderful handle on everything that's out there. Interesting. Yeah, it's
48:23
Speaker 1: sort of like a universal currency for the multiverse exactly.
48:26
Speaker 1: It's pretty hard to exist without any gravity. All right, Well,
48:29
Speaker 1: I think that answers correct questions and all of our
48:31
Speaker 1: questions today. Those were really great questions. Thank you for
48:34
Speaker 1: taking them in. Yes, thank you everybody who's thinking about
48:37
Speaker 1: the universe and being curious. And if you have questions
48:40
Speaker 1: and have been too shy to send them in, please
48:42
Speaker 1: don't hold back or right to us two questions at
48:44
Speaker 1: Daniel and Jorge dot com. The only thing we ask
48:46
Speaker 1: is that you were ethical in your thought experiments, or
48:49
Speaker 1: at least to them in another universe. Then then you
48:51
Speaker 1: can do whatever you want, right, No, man, Other universes
48:54
Speaker 1: have feelings too, though. I guess if we're feeling them,
48:57
Speaker 1: then they're in our universe by my rule. Yeah, you
49:00
Speaker 1: just canceled your own question. I guess I did. All right. Well,
49:03
Speaker 1: we hope you enjoyed that. Thanks for joining us, see
49:06
Speaker 1: you next time. Thanks for listening and remember that. Daniel
49:17
Speaker 1: and Jorge Explain the Universe is a production of iHeartRadio.
49:20
Speaker 1: For more podcast from my heart Radio, visit the iHeartRadio app,
49:25
Speaker 1: Apple Podcasts, or wherever you listen to your favorite shows.