Latest / Daniel and Kelly’s Extraordinary Universe / Listener Questions 64: Phase of the Universe, particle interactions and Universe-sized black holes!

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Listener Questions 64: Phase of the Universe, particle interactions and Universe-sized black holes! · Daniel and Kelly’s Extraordinary Universe

• 0:07
  Speaker 1: Hey, Daniel, how many questions do we get about black holes?
• 0:10
  Speaker 2: Oh?
• 0:10
  Speaker 3: Man, maybe like half of all of our questions are
• 0:13
  Speaker 3: about black holes.
• 0:14
  Speaker 1: Wow, So even after we've talked about it for so much,
• 0:16
  Speaker 1: people still have questions, you know.
• 0:18
  Speaker 3: I think there's just like a never ending curiosity about
• 0:21
  Speaker 3: black holes.
• 0:22
  Speaker 1: There's like a black hole of curiosity about black holes.
• 0:26
  Speaker 3: Maybe all of our answers are just going into a
• 0:28
  Speaker 3: black hole somewhere.
• 0:29
  Speaker 1: Or maybe we're in a black hole if people can't
• 0:31
  Speaker 1: listen to our answers, in.
• 0:33
  Speaker 3: Which case those people should just jump into the black
• 0:35
  Speaker 3: hole with us and then they can hear all of
• 0:37
  Speaker 3: our explanations.
• 0:38
  Speaker 1: That's why we could all be trapped in a black
• 0:40
  Speaker 1: hole together.
• 0:43
  Speaker 3: Knowing the truth, but never able to escape.
• 0:45
  Speaker 1: But at least they can hang out with us.
• 1:02
  Speaker 2: Hi.
• 1:02
  Speaker 1: I am hooorgem made cartoonist and the author of Oliver's
• 1:04
  Speaker 1: Great Big Universe.
• 1:06
  Speaker 2: Hi.
• 1:06
  Speaker 3: I'm Daniel. I'm a particle physicist and a professor at
• 1:09
  Speaker 3: UC Irvine, and I've pretty much accepted the fact that
• 1:11
  Speaker 3: we may never see inside a black hole.
• 1:14
  Speaker 1: Well, I think that's definitely true, right, Like, if you're
• 1:16
  Speaker 1: inside of a black hole, can you even see.
• 1:18
  Speaker 3: If you're inside a black hole, you can see things
• 1:20
  Speaker 3: from outside the universe, and general relativity tells us we
• 1:24
  Speaker 3: can never see inside a black hole. But you know,
• 1:26
  Speaker 3: quantum mechanics opens a little door there we might one
• 1:30
  Speaker 3: day be able to crack open. But maybe not. There
• 1:32
  Speaker 3: might just be some secrets of the universe forever hidden
• 1:35
  Speaker 3: from us. But everything else will figure out, right, Wow,
• 1:43
  Speaker 3: that's so optimistic. Everything else, definitely. How to get a
• 1:47
  Speaker 3: good night's sleep, definitely, sure. How to raise kids without conflicts?
• 1:51
  Speaker 3: Oh yeah, we'll figure all that stuff out, I'm sure.
• 1:54
  Speaker 1: Yeah. I mean compared to black holes, that stuff is easy, right, Compared.
• 1:59
  Speaker 3: To black holes, stuff is actually hard because there doesn't
• 2:02
  Speaker 3: necessarily have to be an answer. At least with black holes.
• 2:05
  Speaker 3: There's something in there. There is a truth. That's the
• 2:09
  Speaker 3: thing I like about science questions as opposed to like
• 2:11
  Speaker 3: philosophy or you know, moral questions, where there isn't always
• 2:15
  Speaker 3: even an answer. At least science you know there is
• 2:17
  Speaker 3: a truth even if you don't know it. What if
• 2:20
  Speaker 3: you can't know it, like, what if it's impossible to know?
• 2:23
  Speaker 3: In which case isn't that the same as there not
• 2:26
  Speaker 3: being an answer? Well, now you're asking a philosophical question
• 2:30
  Speaker 3: to which there is no answer, which.
• 2:33
  Speaker 1: Are even harder questions than black holes.
• 2:36
  Speaker 3: Would it like to be a bat inside a black hole?
• 2:38
  Speaker 3: Nobody will ever know?
• 2:40
  Speaker 1: What's it like to be a banana? That's an even
• 2:42
  Speaker 1: harder question, more supery subject.
• 2:45
  Speaker 3: Well, some fraction of you is bananas, so you could
• 2:47
  Speaker 3: speak to that question. Wait what I'm saying. You are
• 2:50
  Speaker 3: what you eat, and you eat a lot of bananas,
• 2:52
  Speaker 3: so you are some fraction of banana.
• 2:54
  Speaker 1: But anyways, welcome to our podcast Daniel and Jorge Explain
• 2:57
  Speaker 1: the Universe, a production of iHeart Radio.
• 3:00
  Speaker 3: In which we believe, without justification, that the universe is understandable,
• 3:05
  Speaker 3: that with our little minds we can somehow build models
• 3:08
  Speaker 3: to explain how it all works out there, that our
• 3:11
  Speaker 3: little mathematical tools can give us some insight into what's
• 3:14
  Speaker 3: going on inside black holes, the early universe, the far
• 3:17
  Speaker 3: future of the universe, and everything in between. We think
• 3:22
  Speaker 3: that colliding questions and answers is like matter and antimatter annihilation,
• 3:26
  Speaker 3: producing huge explosions of understanding. And we encourage you to
• 3:31
  Speaker 3: think about the universe with us and come along for
• 3:33
  Speaker 3: the journey.
• 3:33
  Speaker 1: That's right, We like to track here humanities were they
• 3:37
  Speaker 1: attempt at trying to understand everything around us works and
• 3:41
  Speaker 1: why it came to be the way it is, and
• 3:43
  Speaker 1: to look into the darkest corners of the universe to
• 3:46
  Speaker 1: ask questions and figure out what's going on even in
• 3:49
  Speaker 1: black holes.
• 3:50
  Speaker 3: And while most of us don't get paid to think
• 3:52
  Speaker 3: about these things about the universe, it is something that
• 3:55
  Speaker 3: belongs to all of us and something that everybody can enjoy.
• 3:59
  Speaker 3: We should all be thinking about the fundamental nature of
• 4:01
  Speaker 3: our reality and wondering about it, trying to piece it
• 4:04
  Speaker 3: together in our minds, and when something doesn't make sense,
• 4:08
  Speaker 3: asking questions, why is it this way? How does this work?
• 4:11
  Speaker 3: How does this fit with that thing? We'd love to
• 4:14
  Speaker 3: encourage you to ask those questions, and specifically to ask
• 4:17
  Speaker 3: them to us. Write to us to questions at Danielandjorghe
• 4:21
  Speaker 3: dot com or straight to me find my email address
• 4:24
  Speaker 3: everywhere online. We will answer your questions. Everybody gets an answer.
• 4:29
  Speaker 1: That's right, because we believe everyone is part of science.
• 4:32
  Speaker 1: Science is a group effort here with humanity because we
• 4:35
  Speaker 1: all have questions about how everything works, why we're here,
• 4:39
  Speaker 1: and what the true nature of the universe is.
• 4:42
  Speaker 3: Yes, science is democratic, is by the people and for
• 4:45
  Speaker 3: the people. I'm not sure if it's of the people
• 4:47
  Speaker 3: or not, or of the bananas, but science is about people.
• 4:51
  Speaker 3: It's about people, some of it, yeah, sometimes sometimes, Yeah,
• 4:55
  Speaker 3: there are scientific questions about people. And encourage everybody to
• 4:58
  Speaker 3: play a role because it's your curiosity that drives all
• 5:01
  Speaker 3: of signs forward and that allows us to do research
• 5:05
  Speaker 3: at the cutting edge and figure out the answers to
• 5:07
  Speaker 3: fundamental questions about the universe. So please send us your questions.
• 5:11
  Speaker 3: Sometimes I'll get a question and I think, oh, we
• 5:13
  Speaker 3: should answer this one on the podcast, and I'll ask
• 5:15
  Speaker 3: you to record yourself asking it so we can talk
• 5:18
  Speaker 3: about it here on the pod. Yeah.
• 5:20
  Speaker 1: Sometimes we'd like to answer listener questions, and so today
• 5:23
  Speaker 1: on the podcast, we'll be tackling listener questions Number sixty four.
• 5:33
  Speaker 1: It's a special Power of two edition, Oh sixty four.
• 5:36
  Speaker 3: Yeah.
• 5:36
  Speaker 1: I think there are a lot of numbers that are
• 5:38
  Speaker 1: the power of Oh.
• 5:40
  Speaker 3: Yeah, but as you go up, they're fewer and fewer.
• 5:42
  Speaker 3: We're not going to get to another one for a while.
• 5:45
  Speaker 1: Does that mean we ignore number thirty two.
• 5:49
  Speaker 3: We didn't commemorate. Yes, Unfortunately we missed those opportunities. But
• 5:52
  Speaker 3: I didn't want to let another one slide by unmentioned.
• 5:56
  Speaker 1: Yes, we need to double our efforts here exactly, But
• 5:59
  Speaker 1: I wonder if you've been makes sense to keep counting these,
• 6:02
  Speaker 1: you know, I think I've raced this before, but we
• 6:04
  Speaker 1: seem to be doing these pretty often.
• 6:05
  Speaker 3: Yeah, we've been getting a lot more questions from listeners,
• 6:08
  Speaker 3: and I feel bad about the backlog, and so we
• 6:10
  Speaker 3: should be going through these. But it's helpful to have
• 6:13
  Speaker 3: a number because then I can point people to them
• 6:15
  Speaker 3: and let them know when their question is going to
• 6:17
  Speaker 3: be answered. But if you prefer, we can give them
• 6:19
  Speaker 3: a name. This can be Listener Questions Samantha or something. Bob, Doug,
• 6:26
  Speaker 3: Welcome to Listener Questions, Alfonso.
• 6:29
  Speaker 1: Well, we have some awesome questions here today, whether they're
• 6:32
  Speaker 1: from Samantha, Bob or Alfonso, and they are about really
• 6:35
  Speaker 1: interesting topics. We have some questions here about the beginning
• 6:38
  Speaker 1: of the universe, about matter and antimatter, and of course
• 6:43
  Speaker 1: about black holes. What percentage of our questions are about
• 6:47
  Speaker 1: black holes, Daniel.
• 6:49
  Speaker 3: The ones that come in maybe like fifty percent, but
• 6:52
  Speaker 3: I can't put them all on the pod.
• 6:54
  Speaker 1: Sounds like we need like an offshoot podcast just about
• 6:57
  Speaker 1: black holes. But anyways, let's jump into it. Our first
• 7:00
  Speaker 1: question comes from Dale, who lives in Washington.
• 7:03
  Speaker 2: Hi, Daniel and Jrage. My name is Dale and I
• 7:06
  Speaker 2: live in and I have a question for you. You
• 7:10
  Speaker 2: often say that at the beginning of our universe, physics
• 7:13
  Speaker 2: was different when things were really dense and hot, and
• 7:16
  Speaker 2: that our universe had to cool off and dilute a
• 7:18
  Speaker 2: bit for things to settle down to the way we
• 7:20
  Speaker 2: see it now, all that in the future things will
• 7:24
  Speaker 2: get so cool and alude that physics we see now
• 7:27
  Speaker 2: won't work the same way, not just the heat death
• 7:30
  Speaker 2: of our universe, but possibly gravity or time or whatever
• 7:34
  Speaker 2: just stops working as we understand it. Time to answer
• 7:38
  Speaker 2: my question, love the podcast.
• 7:40
  Speaker 1: All Right, an interesting question kind of about the beginning
• 7:43
  Speaker 1: of the universe, but also about the end of the
• 7:45
  Speaker 1: universe or the future of the universe.
• 7:48
  Speaker 3: Yeah, and I picked this question to talk about on
• 7:50
  Speaker 3: the podcast because I think it raises a really important
• 7:54
  Speaker 3: and kind of subtle issue about the physics that we're
• 7:57
  Speaker 3: doing and what we know about how the universe works.
• 8:01
  Speaker 3: Has to do with how things emerge from the fundamental
• 8:04
  Speaker 3: rules of the universe, whether we know those fundamental rules,
• 8:08
  Speaker 3: and whether the emergence. Stuff can change over time.
• 8:11
  Speaker 1: Yeah, it kind of raises the idea that maybe the
• 8:14
  Speaker 1: rules of the universe can change, right, because the idea
• 8:17
  Speaker 1: that scientists haves that maybe the rules of the universe
• 8:21
  Speaker 1: have changed or they can change from the beginning of
• 8:24
  Speaker 1: the universe.
• 8:25
  Speaker 3: Yeah, and that is probably confusing to people because they think, well,
• 8:27
  Speaker 3: the universe follow some rules, and how could those rules change.
• 8:32
  Speaker 3: So I think in your mind it's important to draw
• 8:34
  Speaker 3: a distinction between like the fundamental laws of the universe
• 8:37
  Speaker 3: sort of at the base level of reality. We don't
• 8:40
  Speaker 3: know where that is or what that is, or what
• 8:42
  Speaker 3: those laws are, but imagine that they exist as some
• 8:45
  Speaker 3: sort of like foundational firmament, the basic bits of the universe,
• 8:49
  Speaker 3: how they interact with each other. We think probably those
• 8:51
  Speaker 3: don't change. Those were true always and they will always
• 8:55
  Speaker 3: be true. But how those manifest themselves depends on sort
• 8:59
  Speaker 3: of like the temperture in the conditions of the universe
• 9:02
  Speaker 3: the same way that you experience like in our everyday life.
• 9:05
  Speaker 3: Take for example, a glass of water. You know, you
• 9:08
  Speaker 3: can describe the fluid dynamics of a glass of water
• 9:10
  Speaker 3: when it's liquid, but those laws don't really apply anymore.
• 9:14
  Speaker 3: If you freeze it or if you turn it into steam.
• 9:16
  Speaker 3: It's still the same basic rules describing like water molecules
• 9:19
  Speaker 3: and how they interact. Those haven't changed, but the effective laws,
• 9:23
  Speaker 3: what actually helps you describe what you're seeing, does change
• 9:27
  Speaker 3: as the conditions change, and we think that probably is
• 9:30
  Speaker 3: also true for particle physics. We think that the laws
• 9:34
  Speaker 3: we have now are not the fundamental laws of the universe.
• 9:37
  Speaker 3: They're more like the fluid dynamics or the crystal structures
• 9:40
  Speaker 3: of water, or the ideal gas law for steam. They're
• 9:44
  Speaker 3: an effective description of some emergent phenomena that has bubbled
• 9:48
  Speaker 3: up from the fundamental.
• 9:49
  Speaker 1: Laws, meaning they're sort of like f equals in MA.
• 9:52
  Speaker 1: Like it helps you throw baseball, it helps you launch
• 9:55
  Speaker 1: a projectile, but it may not necessarily help you put
• 9:58
  Speaker 1: too particles together.
• 9:59
  Speaker 3: Yeah, that's exactly right. F equals MA is an effective law.
• 10:03
  Speaker 3: You know, A more fundamental description of a baseball is
• 10:05
  Speaker 3: thinking about the quantum mechanical wave function of all of
• 10:08
  Speaker 3: those particles, and that's really hard to do. It's much
• 10:11
  Speaker 3: more useful to talk about the emergent phenomena, the simplicity
• 10:15
  Speaker 3: that somehow emerges from the chaos. That's going on underneath.
• 10:19
  Speaker 3: And the crucial thing to know is that that's really
• 10:21
  Speaker 3: really hard to do. You can't always start from the
• 10:24
  Speaker 3: tiny little bits and blobs toing and froing and derive
• 10:28
  Speaker 3: the emergent phenomena. You mostly just have to observe them
• 10:30
  Speaker 3: and say, oh, look, there is some simplification here.
• 10:34
  Speaker 1: So when you say that, do you have some effective
• 10:36
  Speaker 1: laws in particle physics, what are those laws?
• 10:39
  Speaker 2: Like?
• 10:39
  Speaker 1: How would you describe the laws we have right now?
• 10:41
  Speaker 3: So we have laws at many, many different layers. You know,
• 10:44
  Speaker 3: for example, we can talk about chemistry. Chemistry are effective laws.
• 10:48
  Speaker 3: You want to talk about how hydrogen and oxygen come
• 10:50
  Speaker 3: together to make water. Chemists have all sorts of rules
• 10:53
  Speaker 3: about how that happens. Those are not the fundamental laws
• 10:56
  Speaker 3: of the universe. They're effective laws. You want to drill
• 10:59
  Speaker 3: down into it. Atomic physics, talk about like the structure
• 11:02
  Speaker 3: of the hydrogen atom. There are rules and laws there
• 11:05
  Speaker 3: we can follow. Those are not the fundamental laws. Then
• 11:08
  Speaker 3: you want to drill down into nuclear physics. We can
• 11:10
  Speaker 3: do calculations. There's all these different layers at which you
• 11:13
  Speaker 3: can do calculations. None of those are fundamental laws. Even
• 11:17
  Speaker 3: the most basic level that we do understand quarks and
• 11:20
  Speaker 3: leptons the standard model of particle physics. We sometimes describe
• 11:24
  Speaker 3: those as the fundamental laws of the universe, but we're
• 11:26
  Speaker 3: pretty sure they're not. We know, for example, as Dale mentions,
• 11:30
  Speaker 3: that they don't describe the very early universe, that there's
• 11:33
  Speaker 3: a moment before which our laws cannot describe, and so
• 11:36
  Speaker 3: we know they have to be effective.
• 11:38
  Speaker 1: They're not fundamental, right, And I think the idea that
• 11:42
  Speaker 1: these laws it can change or are different. It's not
• 11:44
  Speaker 1: necessarily that they change, but it's more like they only
• 11:47
  Speaker 1: apply to certain conditions, right, like ef equals. They may
• 11:50
  Speaker 1: work for a baseball and a cannon ball, but doesn't
• 11:52
  Speaker 1: work for little tiny particles, just like maybe your particle
• 11:57
  Speaker 1: physics laws don't work under certain conditions, but they don't
• 12:00
  Speaker 1: work maybe under extreme conditions, like maybe the time we
• 12:03
  Speaker 1: had at the beginning of the universe.
• 12:05
  Speaker 3: Yeah, the laws themselves don't change. The conditions change, and
• 12:09
  Speaker 3: then which laws are relevant changes. Just like if you're
• 12:13
  Speaker 3: floating in water, you're going to use a certain set
• 12:15
  Speaker 3: of laws, and then if somebody boils that into steam,
• 12:17
  Speaker 3: you're not going to use the fluid dynamics anymore. Now
• 12:20
  Speaker 3: you're going to use your understanding of how gases work.
• 12:23
  Speaker 3: And so the universe is changing because the universe is cooling.
• 12:26
  Speaker 3: It started off very very hot and dense in a
• 12:28
  Speaker 3: state that we can't describe using our current laws because
• 12:31
  Speaker 3: gravity and quantum mechanics were both important and we don't
• 12:34
  Speaker 3: know how to unify them. And then it cooled to
• 12:36
  Speaker 3: a place where we could do those calculations because mostly
• 12:39
  Speaker 3: gravity and quantum mechanics don't intermingle and aren't both relevant.
• 12:42
  Speaker 3: So we know how to do those calculations, and the
• 12:44
  Speaker 3: universe has been cooling ever since. And Dale's question is,
• 12:48
  Speaker 3: are we going to pass into some new phase where
• 12:51
  Speaker 3: there are some new effective laws in the future of
• 12:54
  Speaker 3: the universe, so that these effective laws aren't really relevant anymore.
• 12:58
  Speaker 1: Right, because like at the beginning of the universe, thinks
• 13:00
  Speaker 1: are so hot and dance dead. I know we mentioned
• 13:03
  Speaker 1: this in the podcast that the quantum fields were sort
• 13:06
  Speaker 1: of different. They hadn't settled yet.
• 13:08
  Speaker 3: Yeah, there's sort of two different regimes there. One is
• 13:10
  Speaker 3: before we can even really talk about quantum fields, where
• 13:14
  Speaker 3: we're in a regime of quantum gravity, because quantum fields
• 13:17
  Speaker 3: can't describe everything because they ignore the gravitational effects. So
• 13:21
  Speaker 3: before that, not even quantum fields are relevant. Then there's
• 13:24
  Speaker 3: a period the very beginning of the universe that we
• 13:26
  Speaker 3: can describe using quantum fields. But the quantum fields have
• 13:30
  Speaker 3: so much energy that doesn't really make sense to talk
• 13:32
  Speaker 3: about like individual particles. The fields themselves are just frothing
• 13:35
  Speaker 3: with energy. Then as the universe cools, particles start to
• 13:39
  Speaker 3: be a useful thing to talk about because the energy
• 13:41
  Speaker 3: in the fields has spread out and matter has diluted
• 13:44
  Speaker 3: enough that you have these individual pockets that are useful
• 13:46
  Speaker 3: to talk about. So fields emerge first and then particles.
• 13:50
  Speaker 1: But isn't there a point set of where physicists talk
• 13:53
  Speaker 1: about the Higgs field, sort of settling or finding a
• 13:55
  Speaker 1: right spot.
• 13:56
  Speaker 3: Yeah. As the universe cools all these fields, their energy dissipates,
• 14:00
  Speaker 3: and a lot of them go towards zero, none of
• 14:02
  Speaker 3: them actually to zero, and the Higgs field gets stuck
• 14:05
  Speaker 3: at a particularly high value of potential energy unlike a
• 14:09
  Speaker 3: lot of the other fields, And that's the process of
• 14:12
  Speaker 3: the whole universe cooling. But again Dale's question is about,
• 14:14
  Speaker 3: like the far future, are things going to change again
• 14:17
  Speaker 3: so that we might need a new set of effective
• 14:20
  Speaker 3: laws to describe what's going.
• 14:21
  Speaker 1: To happen, right, I guess the question is, like, is
• 14:23
  Speaker 1: the universe going to change or do you foresee the
• 14:27
  Speaker 1: conditions of the universe changing enough so that our current
• 14:30
  Speaker 1: laws don't even work.
• 14:32
  Speaker 3: Yeah, it's a good question. What we do think is
• 14:34
  Speaker 3: the universe will keep expanding, which means it's going to
• 14:37
  Speaker 3: keep cooling. And the current average temperature of the universe
• 14:39
  Speaker 3: is about two point seven calvin. That's the temperature of
• 14:42
  Speaker 3: the cosmic microwave background radiation that fills the universe. It's
• 14:46
  Speaker 3: been red shifted down to two point seven calvin. So
• 14:48
  Speaker 3: we're not that far from zero. Right, We've gone a
• 14:51
  Speaker 3: long way from very high temperature the early universe down
• 14:54
  Speaker 3: to approaching zero. There's not much room left. But what
• 14:58
  Speaker 3: we don't know is what the future holds.
• 15:00
  Speaker 1: Isn't it all sort of relative though?
• 15:01
  Speaker 3: Yeah, exactly, it's all sort of relative. We don't know
• 15:04
  Speaker 3: what the future holds.
• 15:05
  Speaker 1: What seems like to us is a small change from
• 15:07
  Speaker 1: zero to two point zero point seven or two point seven.
• 15:11
  Speaker 1: It could be a big difference. We don't know, right,
• 15:14
  Speaker 1: We don't know.
• 15:14
  Speaker 3: It could be very rich with interesting new physics on
• 15:17
  Speaker 3: very different timescales. Like say, nothing fundamentally changes. Maybe the
• 15:21
  Speaker 3: Higgs field doesn't collapse and nothing else fundamentally changes. As
• 15:25
  Speaker 3: we approach the heat death of the universe, things spread
• 15:27
  Speaker 3: out and keep cooling. It could be that there are
• 15:30
  Speaker 3: new emergent phenomena that come about. You know, the same
• 15:33
  Speaker 3: particles we know about now moving very very slowly. The
• 15:36
  Speaker 3: universe is very cold. There could be interesting things that
• 15:39
  Speaker 3: happen instead of over microseconds or milliseconds or even seconds,
• 15:43
  Speaker 3: over like centuries or millennia, new emergent phenomena.
• 15:47
  Speaker 1: Wait, wait, are particles actually going to be moving slower?
• 15:51
  Speaker 1: They're not right?
• 15:51
  Speaker 3: Why do you say that?
• 15:52
  Speaker 1: Meaning like you might say that the temperature is getting lower,
• 15:55
  Speaker 1: meaning like the average velocity of the particles per square
• 15:58
  Speaker 1: cubic meter or something is getting smaller. But in the
• 16:02
  Speaker 1: video particles are they necessarily going to be going slower?
• 16:05
  Speaker 3: Well, the energy in the universe is decreasing as it expands.
• 16:08
  Speaker 3: Things do get red shifted. So for example, photons lose
• 16:11
  Speaker 3: energy right as the universe expands and they get stretched,
• 16:14
  Speaker 3: they get red shifted.
• 16:15
  Speaker 1: So like let's say a natrina flying through space. I
• 16:18
  Speaker 1: think we talked about this recently. If it's just flying
• 16:20
  Speaker 1: through space, and space is stretching, it's going to slow down.
• 16:23
  Speaker 3: So photons do not slow down, they lose energy. Particles
• 16:26
  Speaker 3: with mass do get red shifted, though I know you
• 16:29
  Speaker 3: objected to the ease of the word red on that,
• 16:32
  Speaker 3: and so they do lose energy. I think an intuitive
• 16:34
  Speaker 3: way to think about it is think about expansion as
• 16:37
  Speaker 3: the opposite of compression. If you compress things, they heat up,
• 16:41
  Speaker 3: right Why because you're confining them to a box, or
• 16:44
  Speaker 3: something hits the edge of the box, you're turning it around,
• 16:46
  Speaker 3: you're squeezing them. Expansion is the opposite process, and so
• 16:50
  Speaker 3: that's why things cool down when they expand.
• 16:53
  Speaker 1: So particles do slow down, you're saying, as they fly
• 16:56
  Speaker 1: through expanding space.
• 16:57
  Speaker 3: Yeah, and so you might imagine that in the future,
• 17:00
  Speaker 3: if particles are all moving very slowly, there could still
• 17:02
  Speaker 3: be really interesting things that happen. Like think about glaciers.
• 17:06
  Speaker 3: Glaciers move super duper slowly, but there's interesting effects from
• 17:09
  Speaker 3: glaciers right valleys and mountains and all sorts of geological
• 17:13
  Speaker 3: effects that are super duper slow but that emerge over
• 17:17
  Speaker 3: long periods of time. It could be that the universe
• 17:20
  Speaker 3: in some future state is a cold soup that seems
• 17:23
  Speaker 3: like it's not doing anything interesting in our scale. Some
• 17:25
  Speaker 3: new emergent laws could come about that are really fascinating
• 17:29
  Speaker 3: and even lead to like complexity and life even over
• 17:32
  Speaker 3: like much much longer time scales.
• 17:35
  Speaker 1: Hmmm, that would be interesting, although it is a little
• 17:38
  Speaker 1: bit slow. I wonder if something more dramatic could happen
• 17:41
  Speaker 1: as things stretch out, Like could maybe the Higgs field
• 17:44
  Speaker 1: collapse again, or could maybe the electromagnetic field collapse suddenly.
• 17:49
  Speaker 3: It's certainly possible that the Higgs field collapses. Right, the
• 17:51
  Speaker 3: Higgs field didn't cool like everything else the energy, and
• 17:54
  Speaker 3: it got stuck because the Higgs field is different from
• 17:57
  Speaker 3: the other fields. It has a different kind of potential energy.
• 17:59
  Speaker 3: It's not forward for it to go down to zero.
• 18:02
  Speaker 3: It sort of like gets stuck in a little valley
• 18:04
  Speaker 3: on a hill instead of just rolling down the hill.
• 18:06
  Speaker 3: It got stuck in this little valley that's sort of
• 18:08
  Speaker 3: embedded on the side of a hill, and it's not
• 18:11
  Speaker 3: easy for it to go down to lower energy. But
• 18:13
  Speaker 3: if possible, we don't actually know how stable that little
• 18:16
  Speaker 3: value is. It could get kicked out of there and
• 18:18
  Speaker 3: then roll down the hill, in which case the universe
• 18:21
  Speaker 3: would be in a very very different sort of effective
• 18:23
  Speaker 3: phase because all these particles would lose their mass, and
• 18:26
  Speaker 3: again the effective laws of physics would be different. The
• 18:29
  Speaker 3: fundamental laws from the very very grounding of the universe
• 18:32
  Speaker 3: wouldn't have changed, but the conditions of the universe will
• 18:35
  Speaker 3: have changed, and so the effective laws might.
• 18:38
  Speaker 1: Maybe in one of the other fields somehow collapse to
• 18:41
  Speaker 1: or get stuck.
• 18:42
  Speaker 3: The other fields have a different structure, and so they
• 18:43
  Speaker 3: already naturally gravitate towards zero. They're not at zero, and
• 18:47
  Speaker 3: it can't be at zero because quantum mechanics prevents them
• 18:50
  Speaker 3: from ever actually minimizing to zero. So the Higgs fields
• 18:53
  Speaker 3: is the only one with what we call a vacuum
• 18:55
  Speaker 3: expectation value because the structure of its potential energy is different.
• 19:00
  Speaker 3: These fields are weird. We're talking about like energy in
• 19:02
  Speaker 3: the fields. What does that mean, however, that these fields
• 19:04
  Speaker 3: can oscillate. They can vibrate the way string vibrates. Right,
• 19:07
  Speaker 3: we have values of the field, and the fields can
• 19:09
  Speaker 3: have kinetic energy, which is the oscillation of the field.
• 19:12
  Speaker 3: They can also have potential energy, which means like some
• 19:15
  Speaker 3: configuration of the field has more energy than another configuration.
• 19:18
  Speaker 3: Of the field the way like pulling on a guitar
• 19:21
  Speaker 3: string or a spring can give it energy just because
• 19:23
  Speaker 3: of its configuration, and so these fields can store energy.
• 19:26
  Speaker 1: So it's possible for these fields to suddenly work in
• 19:29
  Speaker 1: a different way.
• 19:29
  Speaker 3: Yeah, it is possible. And also, as you've pointed out
• 19:32
  Speaker 3: many times, we don't know that these fields actually describe
• 19:35
  Speaker 3: fundamental things. You know, we used to think of the
• 19:37
  Speaker 3: proton as having a field. We now know it actually
• 19:40
  Speaker 3: is the field of various quarks, and the proton fields
• 19:43
  Speaker 3: is just an effective description that sometimes works and sometimes doesn't.
• 19:47
  Speaker 3: And so could be that the fields we're talking about
• 19:49
  Speaker 3: are not even the fundamental fields of the universe. They're
• 19:51
  Speaker 3: bubbling up from some tinier, little squiggly on fields that
• 19:54
  Speaker 3: are the real description. And the conditions for the squigglyons
• 19:58
  Speaker 3: could change, and the fields we're looking at could change.
• 20:01
  Speaker 3: You know, we've tested them under all sorts of conditions.
• 20:04
  Speaker 3: We pretty confident that they work in the range of
• 20:07
  Speaker 3: the temperature of the universe today and probably to the
• 20:09
  Speaker 3: far future, because cold conditions are not hard to test
• 20:12
  Speaker 3: in the lab. Really really hot conditions are much harder
• 20:15
  Speaker 3: to test. But again, we don't know.
• 20:18
  Speaker 1: What about Dale's part of the question where you ask
• 20:20
  Speaker 1: if maybe gravity or time can stop working or work
• 20:23
  Speaker 1: in a different ways as possible as the universe expands.
• 20:26
  Speaker 3: It certainly is possible because we don't understand gravity over time,
• 20:31
  Speaker 3: and these things are closely related to the expansion of
• 20:34
  Speaker 3: the universe, and our current description of the expansion of
• 20:37
  Speaker 3: the universe comes from general relativity, which tells us how
• 20:39
  Speaker 3: it expands or contracts as you have matter density and
• 20:42
  Speaker 3: radiation density and dark energy density. But most of that
• 20:46
  Speaker 3: is dark energy, which is something we don't understand, and
• 20:48
  Speaker 3: we also don't think general relativity is the correct description
• 20:51
  Speaker 3: of the universe because it ignores quantum mechanics, and so
• 20:55
  Speaker 3: you have a lot of possibility there for surprises. Dark
• 20:58
  Speaker 3: energy could be very different from what we expect. You
• 21:00
  Speaker 3: could do something different from what our naive extrapolations suggest,
• 21:03
  Speaker 3: and gravity could turn out to be very different from
• 21:06
  Speaker 3: what we expect. You know, there could be additional dimensions
• 21:08
  Speaker 3: of space and time, and those could like unravel as
• 21:11
  Speaker 3: time goes on. You never know.
• 21:14
  Speaker 1: All right, Well, it sounds like the answer for a
• 21:16
  Speaker 1: Dale is that, yes, it is possible that in the
• 21:18
  Speaker 1: future maybe physics will work differently maybe something will happen
• 21:22
  Speaker 1: to the fields. The fields might snap or change, or
• 21:24
  Speaker 1: gravity might unravel, as you say. And also maybe we'll
• 21:28
  Speaker 1: get to see new kinds of physics because there'll be
• 21:31
  Speaker 1: super extra colt conditions we have never maybe seen before
• 21:34
  Speaker 1: in the universe exactly.
• 21:36
  Speaker 3: So eat blueberries and bananas, stay healthy so you can
• 21:39
  Speaker 3: be around to see the loss of physics changing.
• 21:42
  Speaker 1: Do you want to see the laws of physics changing?
• 21:45
  Speaker 3: Absolutely?
• 21:45
  Speaker 1: Do you want to see the Higgs field collapse? I
• 21:47
  Speaker 1: don't think we would get to see that experience that
• 21:50
  Speaker 1: for very long.
• 21:51
  Speaker 3: Would No, we would not experience it for very long.
• 21:53
  Speaker 3: But one of my dreams is to be around as
• 21:55
  Speaker 3: humanity unravels. Some of these puzzles we talk about so
• 21:58
  Speaker 3: many times be frustrating to pass on before we figure
• 22:02
  Speaker 3: it out.
• 22:02
  Speaker 1: It sounds like eating a lot of chocolate. Maybe it's
• 22:04
  Speaker 1: not going to help you with that con I'm conflicted.
• 22:10
  Speaker 1: Some things might not be worth it all. Right, Well,
• 22:12
  Speaker 1: let's get to our next questions. We have a question
• 22:15
  Speaker 1: here about matter and antimatter, and a question about black
• 22:19
  Speaker 1: holes and also about matter, So we'll get to those,
• 22:23
  Speaker 1: but first, let's take a quick break. Right, We're answering
• 22:38
  Speaker 1: listening our questions here today and our next question comes
• 22:40
  Speaker 1: from James from Colorado.
• 22:43
  Speaker 4: Hi, Daniel and Jorgey. This is James from Colorado. Thank
• 22:46
  Speaker 4: you for your wonderful show and explanation. I still have
• 22:50
  Speaker 4: a question I can't figure out. It has to do
• 22:52
  Speaker 4: with annihilating anti matter and matter. When I think of
• 22:55
  Speaker 4: two particles being in the same place, I thought that
• 22:58
  Speaker 4: wasn't allowed, like a poly exclusive principle. But when I
• 23:01
  Speaker 4: think of two particles as wait on, it feels like
• 23:04
  Speaker 4: they're always touching. So how is it that anti matter
• 23:07
  Speaker 4: and matter don't annihilate sometimes but do annihilate other times?
• 23:11
  Speaker 4: How close does antimatter have to get to matter before
• 23:14
  Speaker 4: it annihilates? I look forward to the explanation. It's chocolate
• 23:18
  Speaker 4: and bananas.
• 23:19
  Speaker 1: Bye. All right, interesting question. It's sort of a question
• 23:23
  Speaker 1: and an anti question in itself, sort of a statement
• 23:27
  Speaker 1: but also a question.
• 23:28
  Speaker 3: Yeah, and he definitely wants to hear about chocolate and bananas,
• 23:31
  Speaker 3: so he's even on brand for our jokes this episode.
• 23:34
  Speaker 1: Oh, he must be a faithful listener.
• 23:36
  Speaker 3: Thanks very much, James.
• 23:38
  Speaker 1: Oh ye, that's right, he said. He hopes it didn't. Well,
• 23:39
  Speaker 1: I was chocolate and banana. I feel like that's a challenge.
• 23:44
  Speaker 3: All right, I'll bring the chocolate.
• 23:46
  Speaker 1: Can white chocolate and dark chocolate exist at the same time?
• 23:50
  Speaker 3: If you annihilate dark and white chocolate, do you get bananas.
• 23:54
  Speaker 1: Or do you get plantains? You never know they're quantum bananas.
• 24:00
  Speaker 3: They are.
• 24:01
  Speaker 1: Well, let's jump into it. Well, here's how I interpret
• 24:04
  Speaker 1: the question. We've talked about before, how if you get
• 24:07
  Speaker 1: antimatter together with matter, they annihilate and disappear. But then
• 24:11
  Speaker 1: we've also talked about how like two particles can coexist
• 24:14
  Speaker 1: in the same spot at the same time. So I
• 24:17
  Speaker 1: think that's what's confusing James.
• 24:18
  Speaker 3: Yeah, exactly. And I think what's going on in James's
• 24:21
  Speaker 3: mind is that he's imagining that matter and anti matter
• 24:26
  Speaker 3: have to like touch or overlap in some physical way
• 24:30
  Speaker 3: in order to annihilate. I think he's thinking about like
• 24:32
  Speaker 3: two tiny grains of sand coming together and touching or
• 24:35
  Speaker 3: overlapping and then turning into a flash of light. But
• 24:39
  Speaker 3: instead we should think about matter antimatter annihilation.
• 24:42
  Speaker 1: Is he already fail? Danny? You could have said a banana,
• 24:46
  Speaker 1: but you went with a grain of sand.
• 24:48
  Speaker 3: An absolutely tiny banana.
• 24:50
  Speaker 1: I mean, that's such an easy, easy fruit to pick.
• 24:52
  Speaker 1: They're a little hanging fruit like bananas, but you went
• 24:56
  Speaker 1: with the grains of sand.
• 24:57
  Speaker 3: Do you imagine that people think about particles as tiny
• 24:59
  Speaker 3: banana I was thinking tiny particles, like tiny specks of.
• 25:04
  Speaker 1: Matter, but we've always said they're not little balls. Maybe
• 25:07
  Speaker 1: their little banana scape.
• 25:09
  Speaker 3: Yeah, particles. So when you have these two tiny bananas,
• 25:12
  Speaker 3: how do they actually annihilate? I think the useful thing
• 25:15
  Speaker 3: is to remember that particle annihilation is just another kind
• 25:18
  Speaker 3: of particle interaction. You know, when two particles come and
• 25:21
  Speaker 3: bump against each other and change direction or something. They
• 25:25
  Speaker 3: can change direction. They can also change what particles there are. So,
• 25:29
  Speaker 3: for example, an electron and a positron can come near
• 25:33
  Speaker 3: each other and turn into a photon. So now you've
• 25:35
  Speaker 3: changed the kind of particles there are. You can also
• 25:38
  Speaker 3: have an electron just like emit a photon, so now
• 25:41
  Speaker 3: you have changed what kind of particles there are. And
• 25:44
  Speaker 3: you can even wonder like, is the electron that came
• 25:46
  Speaker 3: out of that the same as the electron that went
• 25:48
  Speaker 3: into it. The point is just that matter antimatter annihilation
• 25:52
  Speaker 3: is just another kind of interaction of particles, and for
• 25:56
  Speaker 3: particles to interact. They don't have to actually touch or
• 25:58
  Speaker 3: overlap each other. Do that at a distance using their fields.
• 26:03
  Speaker 1: But I guess what is it about Let's say an
• 26:05
  Speaker 1: electron and a positron, which is an antimatter electron. What
• 26:09
  Speaker 1: is it about them that makes them want to interact
• 26:12
  Speaker 1: with each other? Like an electron and another electron don't
• 26:14
  Speaker 1: interact with each other? Do they? Or do they interact
• 26:17
  Speaker 1: the same way? They just can't get them close enough together.
• 26:19
  Speaker 3: They definitely interact with each other. Absolutely, two electrons will
• 26:22
  Speaker 3: push against each other. Right where else does that repulsion
• 26:25
  Speaker 3: come from? It comes from the interaction of those two electrons.
• 26:29
  Speaker 1: But not just pushing against each other, but sort of
• 26:31
  Speaker 1: like transforming into something else.
• 26:33
  Speaker 3: Yeah. Well, you know, you can ask the philosophical question
• 26:35
  Speaker 3: of whether the electrons that came out of that interaction
• 26:38
  Speaker 3: are the same as the electrons that went into the interaction.
• 26:41
  Speaker 3: It's possible for those interactions to keep the same kinds
• 26:44
  Speaker 3: of particles as they come out, but you know, it's
• 26:45
  Speaker 3: a new momentum, it's a different direction. You could also
• 26:48
  Speaker 3: say it's sort of like the incoming electrons disappear and
• 26:51
  Speaker 3: you get new electrons coming out. But in the case
• 26:55
  Speaker 3: of electrons and positrons annihilating and turning into a photon,
• 26:58
  Speaker 3: it's much clearer that you don't have this same kinds
• 27:00
  Speaker 3: of particles coming in as going out. But again, you
• 27:03
  Speaker 3: don't need matter antimatter annihilation to do that. For example,
• 27:05
  Speaker 3: you can have an electron come in and interact with
• 27:08
  Speaker 3: a neutrino and give you a w boson. So now
• 27:11
  Speaker 3: the electron and the neutrino are gone, but the electron
• 27:14
  Speaker 3: and the neutrino are not matter antimatter pairs.
• 27:16
  Speaker 1: Would you say they annihilated each other.
• 27:18
  Speaker 3: You wouldn't say they annihilate, because that's only a special
• 27:20
  Speaker 3: word we use for matter antimatter interactions. But the point
• 27:24
  Speaker 3: I'm making is that that's really just a subset of
• 27:26
  Speaker 3: particle interactions, and it's possible to change the kind of
• 27:29
  Speaker 3: particles that exist without matter antimatter annihilations, just like a
• 27:33
  Speaker 3: special little subset. But to understand how it works, it's
• 27:36
  Speaker 3: easiest to think about in terms of the broader category
• 27:39
  Speaker 3: of just particles interacting with each other when they get
• 27:41
  Speaker 3: near each other, which doesn't require them to actually overlap
• 27:44
  Speaker 3: and touch.
• 27:45
  Speaker 1: Whoa wha wha woa, Hold on, Hold on, You just
• 27:47
  Speaker 1: got into word definitions there, and I have to force
• 27:51
  Speaker 1: a little stop. Sure, so you're saying that you only
• 27:55
  Speaker 1: use the word annihilation when it's matter and antimatter interacting
• 27:58
  Speaker 1: with each other. But do other particles interact and they
• 28:02
  Speaker 1: totally disappear, just like the matter and antimatter, and they
• 28:05
  Speaker 1: become something else. You don't call that annihilation? Why not?
• 28:07
  Speaker 3: I don't call that annihilation. That's just an interaction, you know.
• 28:11
  Speaker 1: But the same thing happens rights the exact same thing.
• 28:14
  Speaker 1: You're just choosing the word annihilation for one another the other.
• 28:18
  Speaker 3: Yeah, I don't actually like the word annihilation. I think
• 28:21
  Speaker 3: of all these things as an interaction. I know that
• 28:24
  Speaker 3: there's this word annihilation that's used to describe matter and antimatter,
• 28:27
  Speaker 3: and so we can do that. But the point I'm
• 28:29
  Speaker 3: making is that that's just a subset of broader category
• 28:32
  Speaker 3: of interactions, some of which also include particles disappearing. And
• 28:36
  Speaker 3: in fact, the point I was making earlier is you
• 28:38
  Speaker 3: could argue every interaction involves the initial particles disappearing and
• 28:41
  Speaker 3: new particles coming out. It's just in some of those
• 28:44
  Speaker 3: the new particles are the same type, and some of
• 28:46
  Speaker 3: those they're not. But in every case it's sort of
• 28:48
  Speaker 3: like the particles of theseus. You know, is it the
• 28:50
  Speaker 3: same particle that came in and went out?
• 28:54
  Speaker 1: You're saying like all particle interactions are annihilation, kind.
• 28:57
  Speaker 3: Of saying every time you have a particle interaction, you
• 29:01
  Speaker 3: could view the final particles not the same as the
• 29:04
  Speaker 3: initial particle. Sometimes it has some things in common, like oh,
• 29:07
  Speaker 3: it's an electron also like the initial particle was, but
• 29:10
  Speaker 3: it's also different in some ways. It's going in a
• 29:11
  Speaker 3: new direction as a new energy. So yeah, the initial
• 29:15
  Speaker 3: states disappear and the final states appear. Sometimes they have
• 29:18
  Speaker 3: something in common, but they don't always have to.
• 29:21
  Speaker 1: But isn't there something special about matter and antimatter interactions
• 29:24
  Speaker 1: or slash annihilation, which is that they release a lot
• 29:27
  Speaker 1: of energy? So why do we think of those as
• 29:30
  Speaker 1: releasing a lot of energy? But maybe not the others
• 29:33
  Speaker 1: releasing a lot of energy.
• 29:34
  Speaker 3: They don't really release energy. They just transform it, you know,
• 29:37
  Speaker 3: like when an electron and positron interact in a way
• 29:40
  Speaker 3: to produce a photon, they've transformed matter into the energy
• 29:44
  Speaker 3: of a photon, and we sometimes say into pure energy,
• 29:47
  Speaker 3: but you know, there's no such thing as pure energy.
• 29:49
  Speaker 3: Energy has to be in some form. In this case,
• 29:51
  Speaker 3: it can be a photon or an electron, and positron
• 29:53
  Speaker 3: can also annihilate into a z boson, and so we
• 29:56
  Speaker 3: talk about that because there is a flash of light
• 29:59
  Speaker 3: if you do that. If you take for example, a
• 30:01
  Speaker 3: raisin and an anti raisin and they interact with each
• 30:03
  Speaker 3: other and convert into a bunch of photons, that is
• 30:05
  Speaker 3: a lot of energy because there is a lot of
• 30:07
  Speaker 3: energy stored in the mass of that reason and anti raisin,
• 30:11
  Speaker 3: so there's a lot of energy available to transform into photons,
• 30:15
  Speaker 3: which is why like matter antimatter engines would be very
• 30:18
  Speaker 3: very powerful with very small amounts of fuel, just because
• 30:21
  Speaker 3: there's so much energy stored in mass because equals mc
• 30:25
  Speaker 3: squared C squared is a big number.
• 30:27
  Speaker 1: Well, I wonder if maybe the real explanation is that,
• 30:30
  Speaker 1: you know, when you have an electron and an anti electron,
• 30:33
  Speaker 1: like one thing that they can do is interact and
• 30:36
  Speaker 1: turn into photons, which is going to be a lot
• 30:39
  Speaker 1: But maybe if I have an electron and another electron,
• 30:41
  Speaker 1: that's not a possible interaction that can happen between the
• 30:45
  Speaker 1: two of them.
• 30:45
  Speaker 3: Yeah, exactly. There's a lot of rules in particle physics
• 30:48
  Speaker 3: about what can happen and what can't happen. And so
• 30:51
  Speaker 3: that's why, for example, you can't have an electron and
• 30:54
  Speaker 3: a proton turn into a photon, right because there's a
• 30:57
  Speaker 3: rule against that. There's actually two different rules against that.
• 31:00
  Speaker 3: The universe says you can't just delete electrons. It keeps
• 31:03
  Speaker 3: track of the number of electrons, and so you can't
• 31:06
  Speaker 3: just delete an electron from the universe. It also keeps
• 31:09
  Speaker 3: track of the number of baryons. Proton is a kind
• 31:12
  Speaker 3: of baryon, so you can't just delete a baryon from
• 31:15
  Speaker 3: the universe. So that's why you can do electron positron
• 31:18
  Speaker 3: annihilation because a positron counts as a negative electron. So
• 31:21
  Speaker 3: you can destroy an electron if you also destroy it
• 31:24
  Speaker 3: anti electron.
• 31:25
  Speaker 1: But I think maybe James's question was more, how does
• 31:29
  Speaker 1: this annihilation and interaction interact with what I think we've
• 31:32
  Speaker 1: talked about before, which is maybe the poly exclusion principle,
• 31:35
  Speaker 1: which is, you know, the certain rules that say you
• 31:38
  Speaker 1: can't have two particles super close to each other they
• 31:41
  Speaker 1: repel each other kind of naturally, like in a neutron
• 31:44
  Speaker 1: star for example.
• 31:45
  Speaker 3: Yeah, and that's a good question and remember the poly
• 31:47
  Speaker 3: exclusion principle applies to identical particles. So two electrons cannot
• 31:52
  Speaker 3: be in the same state at the same time.
• 31:54
  Speaker 1: Why not?
• 31:55
  Speaker 3: Why can they not be in the same state at
• 31:56
  Speaker 3: the same time. Yeah, particles that have spin one half
• 32:00
  Speaker 3: follows certain quantum rules, and if you try to write
• 32:03
  Speaker 3: down a solution to the rules of quantum mechanics for
• 32:06
  Speaker 3: two spin one half particles in exactly the same state,
• 32:10
  Speaker 3: the math just doesn't work. It's incompatible. The only way
• 32:12
  Speaker 3: to satisfy the equations is for that state to not exist.
• 32:16
  Speaker 3: So mathematically it's just incoherent like there are no solutions
• 32:20
  Speaker 3: to those equations. We actually answer this on the podcast
• 32:23
  Speaker 3: in some more detail another time, talking about the spin
• 32:25
  Speaker 3: statistics theorem, which is what determines this. So particles of
• 32:28
  Speaker 3: spin one or spin zero behave differently in quantum mechanics,
• 32:32
  Speaker 3: and they can exist on top of each other and
• 32:34
  Speaker 3: have solutions to the equations. But you can't do that
• 32:36
  Speaker 3: with spin one half particles like electrons. You can with photons,
• 32:40
  Speaker 3: as many photons as you like can lie on top
• 32:42
  Speaker 3: of each other.
• 32:43
  Speaker 1: So can an electron and an anti electron be in
• 32:45
  Speaker 1: the same spot at the same time.
• 32:47
  Speaker 3: They can be in the same spot at the same time.
• 32:49
  Speaker 3: Because they're not identical particles, right, there's already something to
• 32:52
  Speaker 3: distinguish them. The point of the poly exclusion principle is
• 32:55
  Speaker 3: something has to distinguish them. You can have two electrons
• 32:57
  Speaker 3: at different energy levels, or at different locations, or different
• 33:00
  Speaker 3: something else's different spins, or you can have two different particles.
• 33:04
  Speaker 3: An electron and a positron can be on top of
• 33:06
  Speaker 3: each other and be identical in every other way. The
• 33:09
  Speaker 3: poly exclusion principle does not prevent that.
• 33:12
  Speaker 1: So I guess that's basically the answer for James, which
• 33:15
  Speaker 1: is that the exclusion principle only applies to particles that
• 33:19
  Speaker 1: are the same. Yeah, identical matter and antimatter are not
• 33:21
  Speaker 1: the same.
• 33:22
  Speaker 3: They are not the same. Yeah.
• 33:23
  Speaker 1: In fact, they're sort of anti each other.
• 33:26
  Speaker 3: Yeah, they're also sort of very closely connected.
• 33:28
  Speaker 2: You know.
• 33:28
  Speaker 3: The electron's closest cousin is the positron. It's just like
• 33:31
  Speaker 3: another thing that the same field can do. There's only
• 33:34
  Speaker 3: one field that makes the electron and the positron. It's
• 33:37
  Speaker 3: just two different ways that it can wiggle.
• 33:41
  Speaker 1: What But they have opposite charge, So the same field
• 33:44
  Speaker 1: can make the same wiggle, but they have different charge.
• 33:47
  Speaker 3: Yeah, exactly. There's no positron field in the universe. It's
• 33:50
  Speaker 3: just an electron field. It can wiggle like an electron,
• 33:52
  Speaker 3: or can wiggle like a positron. It's two different wiggles
• 33:56
  Speaker 3: the same field can do. It's like the way you
• 33:57
  Speaker 3: can do more than one dance, right, I hope, I assume.
• 34:00
  Speaker 3: I don't know. I've never seen you dance.
• 34:04
  Speaker 1: Yeah, that's a shame.
• 34:07
  Speaker 3: It might annihilate my eyeballs. I don't know.
• 34:10
  Speaker 1: Yeah, Or I mean, just interact with your eyeballs.
• 34:13
  Speaker 3: You go. James also asks how close do they have
• 34:16
  Speaker 3: to get before they annihilate? Remember that these things happen
• 34:19
  Speaker 3: via fields, and particles never have to be on top
• 34:22
  Speaker 3: of each other in order to interact or to annihilate.
• 34:26
  Speaker 3: So an electron and a positron can annihilate with each
• 34:28
  Speaker 3: other turn into a photon at some distance. In fact,
• 34:31
  Speaker 3: it always happens at some distance because in our theory,
• 34:35
  Speaker 3: these particles are point particles, and so they really have
• 34:38
  Speaker 3: no size that we can determine.
• 34:41
  Speaker 1: Well, I mean, there's something a little bit more to it, though, right,
• 34:44
  Speaker 1: Because like an electron and an anti electron, they have
• 34:47
  Speaker 1: opposite charges, so they actually attract each other.
• 34:49
  Speaker 3: Right, absolutely, they do. They will pull towards each other.
• 34:53
  Speaker 3: If you have an electron and a positron alone in
• 34:55
  Speaker 3: the universe, eventually they will come together and annihilate.
• 35:00
  Speaker 1: Are really close to each other that they're going to
• 35:01
  Speaker 1: be pulling each other even closer, which then raises even
• 35:05
  Speaker 1: the probability that they'll annihilate and interact.
• 35:08
  Speaker 3: Exactly, and the word used was very precise. There probabilities.
• 35:11
  Speaker 3: These things are quantum mechanical, and so there's always a
• 35:13
  Speaker 3: probability for these things to happen. And as the electron
• 35:17
  Speaker 3: and positron get closer and closer, the probability of turning
• 35:20
  Speaker 3: into a photon increases, But it's always a probability. It's
• 35:23
  Speaker 3: always the universe rolling a die, or if there's no observation,
• 35:26
  Speaker 3: maintaining all those probabilities in parallel in superposition.
• 35:30
  Speaker 1: Right, So, I wonder if it's possible for an electron
• 35:32
  Speaker 1: and an anti electron to attract each other, pull each
• 35:35
  Speaker 1: other in, and even though it's improbable that have them
• 35:38
  Speaker 1: not interact until they're right on top of each other,
• 35:41
  Speaker 1: is that possible?
• 35:42
  Speaker 3: It's possible, except I'm not sure what you mean by
• 35:44
  Speaker 3: riot on top of each other if we're thinking about.
• 35:47
  Speaker 1: Right on top of each other occupying the exact same space.
• 35:50
  Speaker 3: Yeah, well, that depends on whether space has infinite resolution
• 35:54
  Speaker 3: and whether electrons are infinitely small. I's so, then it
• 35:57
  Speaker 3: might be impossible for them to be literally in the
• 35:59
  Speaker 3: same location. Two infinitely precise numbers can never be exactly
• 36:03
  Speaker 3: the same.
• 36:04
  Speaker 1: Well, well, there's sort of point particles right.
• 36:05
  Speaker 3: In our theory, we suspect they're probably not. They actually
• 36:08
  Speaker 3: do have some extent and substructure even but in our
• 36:11
  Speaker 3: theory they are currently point particles.
• 36:13
  Speaker 1: Yeah, so could they exist in the same point.
• 36:17
  Speaker 3: It's like asking if two infinitely long strings of numbers
• 36:20
  Speaker 3: are the same, right, can they ever be exactly the
• 36:23
  Speaker 3: same two physical things?
• 36:24
  Speaker 1: Could they? The answers yes, right.
• 36:26
  Speaker 3: You're asking a lot of philosophy questions here on the
• 36:28
  Speaker 3: pot today.
• 36:32
  Speaker 1: I do have a PhD.
• 36:33
  Speaker 3: Ban exactly, you're a doctor of philosophy, and it shows.
• 36:36
  Speaker 1: I can't cure your philosophy though, or prescribe any medication
• 36:41
  Speaker 1: for it. I can only record a podcast.
• 36:44
  Speaker 3: Well, in order to satisfy James, how much chocolate and
• 36:47
  Speaker 3: bananas does it take to cure somebody of philosophy.
• 36:50
  Speaker 1: M well, if you even enough chocolate, you'll definitely be
• 36:52
  Speaker 1: cured of many things, including living, having working hard. But yeah,
• 36:58
  Speaker 1: let's try to bring it back to chocolates. And so,
• 37:00
  Speaker 1: I think what you're saying is that this rule in
• 37:04
  Speaker 1: the universe that says that two things can mean the
• 37:05
  Speaker 1: same spot at the same time only applies to things
• 37:08
  Speaker 1: that are the same. So you can't have two bananas
• 37:10
  Speaker 1: at the same in the same spot, or two chocolate
• 37:12
  Speaker 1: shape bananas in the same spot. But it doesn't apply
• 37:14
  Speaker 1: to things very different. So you can have a banana
• 37:17
  Speaker 1: on top of a chocolate.
• 37:18
  Speaker 3: Yeah, and only two spin one half particles. Right, So photons,
• 37:20
  Speaker 3: for example, can be in exactly the same spot even
• 37:23
  Speaker 3: if they have the same energy, etcetera. There's no limitation there.
• 37:26
  Speaker 3: They're bosons.
• 37:27
  Speaker 1: Wait, what what else is like light? Does only light
• 37:32
  Speaker 1: have none spin one half?
• 37:35
  Speaker 3: No, all the force particles have integed your spin. The
• 37:37
  Speaker 3: Higgs boson is spin zero, the Z and the W
• 37:40
  Speaker 3: are spin one. The graviton, if it exists, is spin two.
• 37:44
  Speaker 3: So all the force particles have integer spin and all
• 37:47
  Speaker 3: the matter particles have half into your spin spin one half.
• 37:51
  Speaker 1: All right, So then the answer is if the rule
• 37:53
  Speaker 1: applies to you. It only applies if you're the same part. Yeah,
• 37:56
  Speaker 1: for the same kind of snack. Yeah, all right, well,
• 38:01
  Speaker 1: thanks James for that question. Let's get to our last question,
• 38:04
  Speaker 1: and it's about kind of all the things black holes, matter,
• 38:08
  Speaker 1: the universe and what's inside. So let's get to it.
• 38:12
  Speaker 1: But first let's take another quick break where we're answering
• 38:27
  Speaker 1: listener questions, and our last question here is about, of course,
• 38:32
  Speaker 1: black holes. This is a question about the size of
• 38:37
  Speaker 1: a black hole. So if you add up all.
• 38:43
  Speaker 5: Of the matter, so dark matter and matter matter, real
• 38:50
  Speaker 5: matter in the universe, and apply the schwartz Child's equation,
• 39:00
  Speaker 5: how big would the resulting black hole be?
• 39:05
  Speaker 1: All Right, Basically I think the question here is what's
• 39:08
  Speaker 1: the biggest black hole you can make?
• 39:11
  Speaker 3: Yeah, and stead of asking like is our universe a
• 39:14
  Speaker 3: black hole? If not, why not? It's a really interesting
• 39:18
  Speaker 3: question and it comes down to some pretty simple mathematics
• 39:21
  Speaker 3: that predicts when you get a black hole and when
• 39:24
  Speaker 3: you don't, which is what Rebecca's referring to when she
• 39:26
  Speaker 3: mentions the short styled equation.
• 39:29
  Speaker 1: Right right, that's the equation that tells you, like, if
• 39:31
  Speaker 1: you condense a matter stuff and energy into a certain sphere,
• 39:36
  Speaker 1: then you get a black hole. If you don't, you
• 39:38
  Speaker 1: don't get a black hole.
• 39:39
  Speaker 3: Yeah, exactly. And the equation is very simple. It says,
• 39:43
  Speaker 3: if you have a certain amount of mass, then if
• 39:45
  Speaker 3: you contain all that mass in a radius of less
• 39:48
  Speaker 3: than two times the gravitational constant times the mass divided
• 39:52
  Speaker 3: by the speed of light squared, then that's a black hole.
• 39:55
  Speaker 3: So it's called the short stiled radius. Well, it's weird
• 39:58
  Speaker 3: how it's so simple, isn't it. It's amazing, it's really
• 40:00
  Speaker 3: kind of beautiful.
• 40:01
  Speaker 1: So it's just the mass times some constant divided by
• 40:06
  Speaker 1: the speed of light.
• 40:07
  Speaker 3: Yeah, and it's linear in mass, which is really interesting, right,
• 40:10
  Speaker 3: which means twice as much mass means the radius grows
• 40:13
  Speaker 3: by two. Right, ten times as much mass, the radius
• 40:16
  Speaker 3: grows by ten. Which is why we talked about one
• 40:18
  Speaker 3: time on the podcast how black holes that are larger
• 40:21
  Speaker 3: technically are lower density because if the mass doubles, the
• 40:25
  Speaker 3: radius doubles, which means a volume octoples.
• 40:30
  Speaker 1: So I guess Rebecca's question here then, is what if
• 40:33
  Speaker 1: you took everything that we know about in the universe.
• 40:35
  Speaker 1: I guess everything in the observable universe and you squeeze
• 40:38
  Speaker 1: it down into a black hole. What's the maximum size
• 40:42
  Speaker 1: of this black hole can be?
• 40:44
  Speaker 3: Yeah, and the answer is going to be sort of
• 40:46
  Speaker 3: weird and shocking because as black holes get larger, their
• 40:50
  Speaker 3: radius gets larger very quickly.
• 40:52
  Speaker 1: Well, first of all, how much stuff and energy is
• 40:55
  Speaker 1: there in the universe? Do we have a number for that?
• 40:57
  Speaker 3: Yeah, So we can calculate that for the absorbservable universe,
• 41:01
  Speaker 3: for the part of the universe that we can see.
• 41:03
  Speaker 3: So the observable universe is about forty six billion light
• 41:06
  Speaker 3: years across. And we know a lot about the density
• 41:10
  Speaker 3: of energy in the universe because we've measured the curvature
• 41:13
  Speaker 3: of it, and we can calculate the mass of galaxies
• 41:16
  Speaker 3: and stars and dark matter and even dark energy, and
• 41:19
  Speaker 3: that comes out to be a pretty small number. It's
• 41:22
  Speaker 3: like ten to the minus thirty grams per cubic centimeter.
• 41:26
  Speaker 3: But that lets us calculate the total effective mass of
• 41:28
  Speaker 3: the universe.
• 41:29
  Speaker 1: And when you say mass, you also mean energy, right,
• 41:32
  Speaker 1: Like you're also counting all the light and are you
• 41:34
  Speaker 1: also counting the dark matter and dark energy?
• 41:37
  Speaker 3: Yes, all the energy in the universe, including dark matter
• 41:40
  Speaker 3: and dark energy. We can treat it as if it
• 41:42
  Speaker 3: was just mass. Equivalent mass of that egles mc square.
• 41:46
  Speaker 3: Take the energy acts as if it was mass.
• 41:48
  Speaker 1: But I feel like, you know, the mass of stars
• 41:51
  Speaker 1: and planets and rocks and even dark matter. You could
• 41:54
  Speaker 1: technically squeeze that down if you move it. But could
• 41:57
  Speaker 1: you move or squeeze the dark energy the universe?
• 42:00
  Speaker 3: Turns out you're not going to need to.
• 42:02
  Speaker 1: What do you mean?
• 42:03
  Speaker 3: So wait for it. I'll walk through the calculation. The
• 42:06
  Speaker 3: total mass contained in the observable universe is something like
• 42:09
  Speaker 3: ten to the fifty seven grams, which is huge, But
• 42:12
  Speaker 3: the Schwartz Child radius for that is four hundred and
• 42:15
  Speaker 3: seventy five billion light years. That's pretty weird. That says,
• 42:20
  Speaker 3: if you have a bunch of stuff, which is the
• 42:21
  Speaker 3: mass of the observable universe, you only need to squeeze
• 42:24
  Speaker 3: it down into a size much much bigger than the
• 42:27
  Speaker 3: observable universe before it becomes a black hole.
• 42:29
  Speaker 1: Wait what that means to someone outside of our observable universe?
• 42:35
  Speaker 1: We are a black hole.
• 42:36
  Speaker 3: That's the interpretation on the face of it, right, That's
• 42:38
  Speaker 3: what it seems like. There's important kyats in that calculation.
• 42:43
  Speaker 3: We're not sure that the swart Child radius calculation applies
• 42:45
  Speaker 3: in this scenario.
• 42:46
  Speaker 1: Oh wait, let me see if I get this raight.
• 42:48
  Speaker 1: This so you're saying the density of energy and mass
• 42:50
  Speaker 1: in the observable universe is higher than it is in
• 42:54
  Speaker 1: a black hole.
• 42:55
  Speaker 3: In a black hole of the radius of the observable universe. Remember,
• 42:59
  Speaker 3: the density of black black holes gets very very low
• 43:01
  Speaker 3: as they get big, because the radius grows with the mass,
• 43:06
  Speaker 3: but the volume goes as mass cubed. Right, So as
• 43:08
  Speaker 3: black holes get very very large, their density actually becomes
• 43:11
  Speaker 3: very very low. And so even though our observable universe
• 43:15
  Speaker 3: is very low energy density, you know, averaged over all
• 43:18
  Speaker 3: the vast reaches of space, it's actually larger energy density
• 43:23
  Speaker 3: than a black hole of that radius.
• 43:26
  Speaker 1: But does that mean that, like, let's say I was
• 43:28
  Speaker 1: a giant you know, I don't know if you know
• 43:30
  Speaker 1: the comic book character Galactus. Like, let's say you're being
• 43:34
  Speaker 1: that's bigger than the observable universe, and I held the
• 43:37
  Speaker 1: observable universe in my hand, would I just be looking
• 43:40
  Speaker 1: at a black hole?
• 43:42
  Speaker 3: It depends on a couple of things, right, So if
• 43:45
  Speaker 3: the rest of the universe is empty and the observable
• 43:48
  Speaker 3: universe has no electric charge and no spin, then yes,
• 43:51
  Speaker 3: if you took as much stuff as there is in
• 43:53
  Speaker 3: the observable universe and crammed it into the radius of
• 43:56
  Speaker 3: the observable universe, it would be a black hole. That
• 43:59
  Speaker 3: does don't mean that our universe is a black hole,
• 44:03
  Speaker 3: because we don't know what's outside of it. This calculation,
• 44:06
  Speaker 3: the Schwartzil radius calculation, it's a simple, beautiful equation because
• 44:09
  Speaker 3: it's making a bunch of important approximations that might not
• 44:13
  Speaker 3: apply to our universe. Number one, it assumes that everything
• 44:16
  Speaker 3: has no spin, that everything has no electric charge, right,
• 44:20
  Speaker 3: and that there's nothing outside of it. When Schwartzeul did
• 44:23
  Speaker 3: his calculation, like how do you make a black hole?
• 44:26
  Speaker 3: He did it in a very simplified situation. He imagined
• 44:28
  Speaker 3: an empty universe with nothing else in it, and then
• 44:32
  Speaker 3: a blob of matter, and he calculated how much you
• 44:34
  Speaker 3: would have to squeeze that down to make a black hole.
• 44:37
  Speaker 1: How o there being stuff elsewhere affect whether or not
• 44:40
  Speaker 1: you make a black hole or not?
• 44:42
  Speaker 3: Well, the general relativity stuff is a little bit complicated
• 44:44
  Speaker 3: to think about. To gain some intuition, we can think
• 44:46
  Speaker 3: about a sort of Newtonian point of view, like, just
• 44:48
  Speaker 3: think about gravity as a force. You know, if you
• 44:51
  Speaker 3: have a universe filled with stuff, are you going to
• 44:54
  Speaker 3: get black holes? Even if the energy dency is really
• 44:57
  Speaker 3: really high, even if you're exceeding the Swartzile radius, will
• 45:00
  Speaker 3: you get black holes? No, because everything is tugging on stuff, right,
• 45:04
  Speaker 3: Having stuff outside will prevent anything from collapsing and falling in.
• 45:08
  Speaker 3: And so there is gravity from stuff outside that affects
• 45:11
  Speaker 3: what's going to happen inside. And so what you really
• 45:15
  Speaker 3: need in order to have a black hole is a
• 45:17
  Speaker 3: region of high energy density surrounded by a region of
• 45:20
  Speaker 3: low energy density. That's why, for example, in the early universe,
• 45:24
  Speaker 3: when everything was filled with energy, it didn't just collapse
• 45:27
  Speaker 3: into one big black hole because it was mostly uniform.
• 45:31
  Speaker 3: And so that's why it's crucial part of that calculation
• 45:34
  Speaker 3: that the stuff is surrounded by an empty universe so
• 45:37
  Speaker 3: it can collapse into a black hole.
• 45:39
  Speaker 1: I think I'm starting to understand here. It's sort of
• 45:41
  Speaker 1: like that analogy that they're use in physics class a
• 45:44
  Speaker 1: lot about gravity, which is like a giant rubber sheet,
• 45:47
  Speaker 1: and if you place a planet or a bowling ball,
• 45:50
  Speaker 1: it creates an indentation, and that's sort of like gravity.
• 45:53
  Speaker 1: I think what you're saying is that you basically need
• 45:56
  Speaker 1: a flat sheet of rubber in order to poke a
• 45:58
  Speaker 1: hole in it, or to press down into enough to
• 46:00
  Speaker 1: create a black hole. But if, like you know, you
• 46:04
  Speaker 1: put a bazillion bowling balls into this rubber sheet, then
• 46:07
  Speaker 1: not one ball is going to create enough of an
• 46:09
  Speaker 1: inventation to make a black hole. The whole basic rubber
• 46:12
  Speaker 1: sheet just bows down.
• 46:14
  Speaker 3: Yeah, there are many flaws in the rubber sheet analogy
• 46:17
  Speaker 3: which can be misleading, but in some cases it can
• 46:19
  Speaker 3: be useful. And here, yeah, think of a black hole
• 46:22
  Speaker 3: not as some absolute stretching of the sheet, but a
• 46:25
  Speaker 3: relative stretching right a place where things are stretched much
• 46:28
  Speaker 3: more than the surroundings. And so if you put an
• 46:31
  Speaker 3: InFine number of bowling balls, you get no black holes.
• 46:34
  Speaker 3: Rather than an infinite number of black holes, you need
• 46:37
  Speaker 3: one bowling ball to stretch the sheet relative to the surroundings.
• 46:40
  Speaker 1: You need like a mega bowling ball amidst all of
• 46:43
  Speaker 1: the other bowling bulls.
• 46:44
  Speaker 3: Exactly. So, if you're the Galacticus giant and the galactus, sorry,
• 46:48
  Speaker 3: if you're the galactus giant.
• 46:50
  Speaker 1: We don't want to get hate mail from Marble fans.
• 46:52
  Speaker 3: If the only mass in the universe is inside the
• 46:54
  Speaker 3: observable universe, then yes, it satisfied to wart Style's condition,
• 46:58
  Speaker 3: and it is a black hole. But if the observable
• 47:01
  Speaker 3: universe is just one scoop of a potentially much larger,
• 47:04
  Speaker 3: maybe infinite universe, and like you know, fifty billion light
• 47:08
  Speaker 3: years over, there's just as much stuff as there is here,
• 47:11
  Speaker 3: then no, none of it's going to be a black hole.
• 47:13
  Speaker 3: And so it really depends what's going on outside the
• 47:15
  Speaker 3: observable universe whether our universe is a black hole or not.
• 47:20
  Speaker 1: Right, like, the observable universe is a bowling ball, and
• 47:23
  Speaker 1: if the rest of the universe is just a flatsheet
• 47:25
  Speaker 1: of rubber with nothing in it, then yes, we are
• 47:27
  Speaker 1: living inside of a black hole. But if the rest
• 47:29
  Speaker 1: of the universe is just more bowling balls, then we're
• 47:32
  Speaker 1: not a black hole.
• 47:33
  Speaker 3: Yeah, exactly does.
• 47:34
  Speaker 1: That mean that if you're inside of a black hole
• 47:36
  Speaker 1: you can things sort of look normal?
• 47:39
  Speaker 3: We really just don't know. It could be that inside
• 47:42
  Speaker 3: a black hole that it's very very low density, that
• 47:45
  Speaker 3: a lot of interesting things can still happen. It can
• 47:48
  Speaker 3: take time for that to collapse into a singularity. Another
• 47:51
  Speaker 3: crucial thing about Schwartzou's calculation is that he was not
• 47:55
  Speaker 3: taking into account and expanding universe right in his calculation,
• 47:59
  Speaker 3: he did not have dark energy, and dark energy completely
• 48:02
  Speaker 3: changes the general relativity of it. So an expanding universe
• 48:05
  Speaker 3: also violates short silence calculation. And we don't know how
• 48:07
  Speaker 3: to calculate what happens to masses in an expanding universe,
• 48:10
  Speaker 3: whether they make black holes or not. That equations are
• 48:13
  Speaker 3: too complicated, So I don't know the answer to that question.
• 48:17
  Speaker 1: M But I feel like maybe the takeaway here is
• 48:19
  Speaker 1: that we could be living in a black hole and
• 48:22
  Speaker 1: not know it.
• 48:22
  Speaker 3: We could be living in a black hole and not
• 48:24
  Speaker 3: know it. To me, I think it's unlikely because it
• 48:26
  Speaker 3: would require the rest of the universe to somehow magically
• 48:29
  Speaker 3: have no stuff in it.
• 48:31
  Speaker 1: That's the kind of thing someone living in a black
• 48:32
  Speaker 1: hole would think to be, like, how can the rest
• 48:36
  Speaker 1: of the universe not be a blood the same as here? Yeah,
• 48:39
  Speaker 1: it's like the whole fish in a fishbole analogy. You're like,
• 48:42
  Speaker 1: you're a fish in a fishball. Must think the whole
• 48:44
  Speaker 1: universe is made out of water.
• 48:45
  Speaker 3: Yeah, it's possible, And if the rest of the universe
• 48:47
  Speaker 3: is vacuum. Then there's nobody in that vacuum wondering why
• 48:49
  Speaker 3: they're in a vacuum. There are only people in not
• 48:52
  Speaker 3: vacuum thinking the rest of the universe is not vacuum.
• 48:54
  Speaker 3: So you're right, and we don't know.
• 48:56
  Speaker 1: But it doesn't have to be a vacuum, does it.
• 48:57
  Speaker 1: It could just be like empty space or that's dense space.
• 49:01
  Speaker 3: Yeah, exactly, that's what I mean. I don't mean no space,
• 49:03
  Speaker 3: I mean empty space by the vacuum. But we also
• 49:07
  Speaker 3: again don't know how to calculate what happens to very
• 49:10
  Speaker 3: dense mass in an expanding universe. So the expansion of
• 49:14
  Speaker 3: the universe might prevent it from turning into a black
• 49:16
  Speaker 3: hole in that scenario. Also, you know, our prediction for
• 49:19
  Speaker 3: what happens to our cosmos currently is that all the
• 49:22
  Speaker 3: galacta clusters collapse into black holes, which are then separated
• 49:26
  Speaker 3: by dark energy. And so it could be that super
• 49:29
  Speaker 3: duper huge black holes in expanding space don't have a
• 49:32
  Speaker 3: singularity to have a bunch of singularities inside of them
• 49:36
  Speaker 3: that are separated by expanding space. Maybe we just don't
• 49:39
  Speaker 3: know how to calculate those things in general relativity, so
• 49:41
  Speaker 3: we don't even know what would happen.
• 49:44
  Speaker 1: I see, and then what would happen to the shortshout
• 49:47
  Speaker 1: equation if you didn't take into account chocolate and bananas?
• 49:50
  Speaker 1: Would it still be the same word?
• 49:53
  Speaker 3: Depends on the fraction of the universe that is chocolate
• 49:55
  Speaker 3: and bananas, which is decreasing as we go on in
• 49:59
  Speaker 3: time because of our contributions.
• 50:01
  Speaker 1: That's right, that's right, because we're eating it and turning
• 50:04
  Speaker 1: into a different kind of dartt All right, Well, I
• 50:08
  Speaker 1: think that's the answer for Rebecca, which is a super
• 50:10
  Speaker 1: interesting question, which is that, Yeah, if you look at
• 50:13
  Speaker 1: the density of the universe, we should be living in
• 50:15
  Speaker 1: a black hole. But who knows. It depends on what
• 50:19
  Speaker 1: is outside of the observable universe.
• 50:21
  Speaker 3: Yeah, that's right. And remember that a lot of the
• 50:23
  Speaker 3: calculations we do in general relativity are for very specific,
• 50:26
  Speaker 3: simplified situations and cannot be applied to more realistic situations.
• 50:31
  Speaker 1: Wait, wait, do you mean general relativity? It doesn't apply
• 50:33
  Speaker 1: to the general case.
• 50:34
  Speaker 3: It applies to the general case, but we don't know
• 50:36
  Speaker 3: how to solve it in the general case. Only a
• 50:39
  Speaker 3: few solutions have ever been found for very highly simplified
• 50:42
  Speaker 3: situations like a universe filled equally smooth with stuff, or
• 50:45
  Speaker 3: an empty universe or a dota matter in the universe.
• 50:48
  Speaker 3: We can't even solve it for like our solar system.
• 50:51
  Speaker 3: So it's very complicated, and so be very careful applying
• 50:54
  Speaker 3: simplified solutions to more general cases.
• 50:57
  Speaker 1: Man, that is just bananas.
• 51:00
  Speaker 3: Go have some chocolate and feel better.
• 51:01
  Speaker 1: Just trying to bring it back for James. I'm just
• 51:03
  Speaker 1: trying to satisfy James's request here, all right, Well, those
• 51:07
  Speaker 1: are three awesome questions. Thank you to our question askers.
• 51:10
  Speaker 1: I think another great reminder of how there are things
• 51:13
  Speaker 1: in this universe that we don't know and may never know.
• 51:16
  Speaker 1: Will the universe change its rules? Are we living in
• 51:18
  Speaker 1: a black hole?
• 51:19
  Speaker 3: Will you die first if you eat too many bananas
• 51:21
  Speaker 3: or too much.
• 51:22
  Speaker 1: Chocolate, or if you annihilate the dark chocolate and bananas
• 51:27
  Speaker 1: is not going to kill you faster? Probably, let's find
• 51:30
  Speaker 1: out that's fine. No, it's not fine enough, or you
• 51:34
  Speaker 1: find out and then you will report it to the podcast.
• 51:36
  Speaker 3: Sounds good, humously, I'll do my homework.
• 51:39
  Speaker 2: All right.
• 51:39
  Speaker 1: Well, thanks again everyone for asking these questions. We hope
• 51:42
  Speaker 1: you enjoyed that. Thanks for joining us. See you next.
• 51:46
  Speaker 3: Time for more science and curiosity. Come find us on
• 51:53
  Speaker 3: social media, where we answer questions and post videos. We're
• 51:57
  Speaker 3: on Twitter, Discord, Instant and now. Thanks for listening, and
• 52:01
  Speaker 3: remember that Daniel and Jorge Explain the Universe is a
• 52:04
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• 52:13
  Speaker 3: favorite shows.