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