Speaker 1: Hey, Daniel, how old do you think our listeners are?
Speaker 2: You know, I think this is a really wide range.
Speaker 2: I've heard from parents who listen with their little kids,
Speaker 2: and there are some very elderly retired engineers out there.
Speaker 1: Interesting. I guess everyone is curious about the universe. But
Speaker 1: who do you think asks the hardest questions?
Speaker 2: That's tricky, you know. I think grown ups ask more
Speaker 2: technical questions, but the kids ask the hardest philosophical questions.
Speaker 1: So are you saying we're all born philosophers, but then
Speaker 1: we grow up to become elderly engineers.
Speaker 2: Yeah, I'm not sure if that's a good outcome or
Speaker 2: a cautionary tale.
Speaker 1: Definitely a good one. Definitely a good one. So if
Speaker 1: you're still a philosopher, does that mean you still need
Speaker 1: to grow up?
Speaker 2: Yeah? Or maybe it means all engineers are cynical.
Speaker 1: What if you have a doctorate in philosophy, does that
Speaker 1: mean you're you'll never grow up?
Speaker 2: You're Peter Pan of Academia.
Speaker 1: I guess I have a PhD in engineering. So where
Speaker 1: does that leave me? I'm like an old baby. I
Speaker 1: am hooorhand May, cartoonist and the author of Oliver's Great
Speaker 1: Big universe.
Speaker 3: Hi.
Speaker 2: I'm Daniel. I'm a particle physicist and a professor at
Speaker 2: u C Irvine, and I love getting questions from our
Speaker 2: youngest listeners and then sometimes even meeting them.
Speaker 1: Mmmm, you don't love getting the questions from the older listeners.
Speaker 2: I didn't say that.
Speaker 1: You were very selective there in your preference.
Speaker 2: I love getting questions from everybody, but I feel a
Speaker 2: little bit more responsibility when I hear from the younger listeners,
Speaker 2: because I might end up influencing the path of their
Speaker 2: lives in some way.
Speaker 1: WHOA, that is a big responsibility. I would feel the
Speaker 1: same if I knew that kids remember things beyond what
Speaker 1: they did last week.
Speaker 2: Well. I recently heard from a listener who is coming
Speaker 2: to UC Irvine next year to be a physics major,
Speaker 2: and she's been listening to our podcast since she was
Speaker 2: in the seventh grade.
Speaker 1: WHOA, she's a super fan. Is she going to major
Speaker 1: in physics? Oh?
Speaker 2: Yeah, wow?
Speaker 1: Are you gonna have her in your class?
Speaker 2: Maybe set her up for some real disappointment.
Speaker 1: Yeah, if you have to give her a bad grade.
Speaker 2: That's what I mean. I feel a real sense of
Speaker 2: responsibility with these young folks.
Speaker 1: Or is she gonna pull the I'm a big fan
Speaker 1: card and then you're gonna give her all a pluses.
Speaker 2: Yeah, I'm a softy. Anyway, I give her pretty good grades.
Speaker 1: I'm sure she's gonna do great and get all a
Speaker 1: pluses on her own. But anyways, welcome for our podcast,
Speaker 1: Daniel and Jorge Explain the Universe, a production of iHeartRadio,
Speaker 1: in which we try.
Speaker 2: To guide the young and the old alike to an
Speaker 2: understanding of the mysteries of the universe. We encourage everybody
Speaker 2: out there to put their brain to the difficult task
Speaker 2: of trying to wrangle the universe. Who make it make
Speaker 2: sense to you? As much as that is possible, We
Speaker 2: want to help guide you along the journey. That's the
Speaker 2: goal of this podcast.
Speaker 1: That's right. As the universe gets older and older, so
Speaker 1: does are understanding of how things work and why things
Speaker 1: are the way they are, and what we know about
Speaker 1: the universe from its early days as a baby universe
Speaker 1: to its now rebellious teenage years. I think.
Speaker 2: Fortunately I had no hand in guiding the infant universe
Speaker 2: along its path, so I can't be held responsible for
Speaker 2: its cold and old state today.
Speaker 1: I think. But other are parts of the universe that
Speaker 1: are warm and young, still.
Speaker 2: Warm, maybe not so young. Everything's pretty old out there.
Speaker 2: But everything we have learned about the universe comes from
Speaker 2: people asking questions. People out there in the street, people
Speaker 2: looking at the night sky, people in laboratories, trying to
Speaker 2: understand the way the universe works. It all begins with
Speaker 2: curiosity and asking questions, trying to make it all make
Speaker 2: sense in your mind.
Speaker 1: Yeah, our understanding of the universe is also growing and
Speaker 1: getting wiser hopefully. And as you said, it all starts
Speaker 1: with asking questions. Everybody ask questions.
Speaker 2: Everybody certainly does, and we encourage you to send those
Speaker 2: questions to us. We answer questions from everybody all across
Speaker 2: the world, the young people, old people, engineers, non engineers,
Speaker 2: even philosophers. Just write to us to questions at Danielandjorge
Speaker 2: dot com. You'll get a response.
Speaker 1: Yeah, and sometimes we'd like to take those questions and
Speaker 1: answer them on the podcast.
Speaker 2: That's right. Pretty often I'll get a question and think, ooh,
Speaker 2: I bet a lot of people have this question, or
Speaker 2: this one's pretty tricky. I need extra time to dig
Speaker 2: into it, so we'll talk about it right here on
Speaker 2: the podcast.
Speaker 1: So do they On the podcast, We'll be tackling listener
Speaker 1: questions number fifty seven, and these are real questions from listeners.
Speaker 2: These are real questions from real listeners. I mean, I
Speaker 2: assume they're not AI generated. I haven't actually checked.
Speaker 1: That would be pretty interesting. But wouldn't the AI already
Speaker 1: know the answer?
Speaker 2: How do I know the answer? It doesn't know anything.
Speaker 2: We don't know. It's just like a distillation of human knowledge.
Speaker 1: Well, or I guess why would it ask you a
Speaker 1: question if it knows everything you know?
Speaker 2: Well, AIS don't really think and Louison right, So they
Speaker 2: might be able to generate simulations of questions, but they
Speaker 2: aren't actually curious. They're not actually asking questions.
Speaker 1: Not yet, Daniel, not yet, not yet.
Speaker 2: Absolutely, yeah, but.
Speaker 1: Yeah, we do like to answer questions here on the podcast.
Speaker 1: And so today we have three great questions about why
Speaker 1: the universe is the way it is, about quantum fields
Speaker 1: and quantum particles, and about particle decay. A lot of
Speaker 1: great questions, some tough questions too. Ooh, do we get
Speaker 1: to grade you then if you fail to answer them?
Speaker 2: You do that every time. Sometimes you're like, that's not
Speaker 2: an explanation, that's just a description.
Speaker 1: Yeah, Well, you know, we gotta have our BS detectors
Speaker 1: up on high alert here.
Speaker 2: Oh yeah, absolutely, it's on every time.
Speaker 1: That's what I'm Well, let's dig into our first question,
Speaker 1: and this one comes from a nine year old Peter.
Speaker 1: Why is the universe the way it is?
Speaker 2: And could it be any different?
Speaker 1: All right, a short but powerful question here from Peter.
Speaker 2: Yes, and I think we might just have to give
Speaker 2: a short and not very powerful answer.
Speaker 1: No, no, no, Peter's nine years old might be influencing
Speaker 1: his entire future life.
Speaker 2: Well, that's exactly what I mean. Nine year old's ask
Speaker 2: sometimes the hardest questions because they're philosophical. Peter is asking
Speaker 2: us not just to look out in the universe and
Speaker 2: try to make sense of it, but to understand what
Speaker 2: that means about the universe. When we figure out the
Speaker 2: laws and the rules that run the universe, we then
Speaker 2: also need to explain why they are that way and
Speaker 2: not some other way. That's not a simple question.
Speaker 1: Well, this is a pretty deep question from a nine
Speaker 1: year old. So the question is why is the universe
Speaker 1: the way it is? And could it be any different?
Speaker 1: So it seems like a two part question here, like
Speaker 1: do physicists know why the universe is the way it is.
Speaker 2: The short answer is we do not. I mean, it
Speaker 2: might be that there's only one way to make a universe,
Speaker 2: that universes like have to be mathematically consistent and follow
Speaker 2: mathematical laws, and that there's only just one way to
Speaker 2: do it, even if we don't yet understand what that
Speaker 2: way is. It might be that there's that kind of requirement,
Speaker 2: but we don't know.
Speaker 1: Wait, what do you mean? It depends on the math.
Speaker 1: Like maybe at the fundamental level of the universe, the
Speaker 1: deepest level, it's all math and logic.
Speaker 2: I mean that the current program is basically try to
Speaker 2: write down a bunch of equations that explain everything that's happening,
Speaker 2: and then make those equations as simple as possible. Right, Like,
Speaker 2: it's not hard to write down a bunch of stuff
Speaker 2: that explains everything that's happening. You could just write down everything,
Speaker 2: you see. The goal of physics is to take a
Speaker 2: long list of observations and describe it with a simple,
Speaker 2: compact explanation. That's really what an explanation is. That's what
Speaker 2: makes it an explanation and not just a description. Right
Speaker 2: That it carries this like predictive power and its compact
Speaker 2: more economical than just saying everything you're seeing. So we
Speaker 2: try to do that mathematically, and we try to make
Speaker 2: that as simple as possible. And imagine sometime far in
Speaker 2: the future when we figured that all out and we've
Speaker 2: been able to explain everything we see, and now we're
Speaker 2: looking at the math of the universe, we can still ask,
Speaker 2: and this is basically what Peter's asking, why this math
Speaker 2: and not some other math. There are some times that
Speaker 2: we can argue why some kinds of math are not allowed,
Speaker 2: you know, like we require this symmetry, or we require
Speaker 2: to base this property or something. Some kind of math
Speaker 2: just wouldn't work, you know, they would give nonsense answers.
Speaker 2: And so I think one possible outcome of that eventual
Speaker 2: journey is that we get to a single equation and
Speaker 2: we understand why it has to be that equation. It's
Speaker 2: the only equation it could possibly be, because no other
Speaker 2: equations work. But another possible outcome is, oh, well, we
Speaker 2: get to an explanation and you know what, it could
Speaker 2: have been something else, Like we have no reason to
Speaker 2: think that there couldn't have been another set of laws
Speaker 2: that create a universe. So number one, we're not close
Speaker 2: to figuring out what the laws of the universe, and
Speaker 2: number two, we don't really know yet how to interpret
Speaker 2: what it means when we do.
Speaker 1: Are you saying, maybe the only way we'll ever know
Speaker 1: why the universe is the way it is is through math.
Speaker 2: That's currently the only way we're getting in the understanding.
Speaker 2: But you know, to make this even more complicated and fuzzy,
Speaker 2: we're also not guaranteed that math, or that our math
Speaker 2: is sufficient to explain the universe. We could also run
Speaker 2: into an obstacle where we were like, hmm, well we
Speaker 2: can't use our math to explain the universe. That doesn't
Speaker 2: mean that the universe can't be explained. It might just
Speaker 2: be that our math is not sufficient. Maybe there's kinds
Speaker 2: of math we haven't invented yet, or there's some fundamental
Speaker 2: assumption and the way we're doing math that prevents us
Speaker 2: from describing the universe. Or maybe we're just not smart enough.
Speaker 2: There could be math that's beyond our mental capability that's
Speaker 2: required to explain the universe. Or maybe the universe just
Speaker 2: isn't mathematical, you know, maybe math is just like a
Speaker 2: language in our minds, not something that's fundamental to the universe.
Speaker 2: There are lots of philosophical rabbit holes there.
Speaker 1: But do you think maybe the universe has to be
Speaker 1: math mathematically consistently. Can you imagine a scenario where the universe,
Speaker 1: like we dig it deep into the nature of the
Speaker 1: universe and we find that the universe is not mathematically consistent?
Speaker 1: What would that mean?
Speaker 2: That certainly is possible. You know, a lot of the
Speaker 2: universe is very difficult for us to describe mathematically. You know, take,
Speaker 2: for example, something that's simple. You drop a ball and
Speaker 2: you describe how it falls. We can do that. Cool.
Speaker 2: Now take that ball and make it a leaf. Well,
Speaker 2: that's more complicated because the leaf depends on the air
Speaker 2: and the currents now. Make it like a thousand leaves
Speaker 2: and add a bunch of fans. It's way too complicated
Speaker 2: for us to describe using our mathematics. And it might
Speaker 2: also be that it can't be described with our mathematics.
Speaker 2: There are philosophers out there that say that these complex
Speaker 2: regions that are very challenging for us to describe might
Speaker 2: not even be governed by physical laws. There could be
Speaker 2: no mathematical explanation for it. It's kind of a fringe
Speaker 2: view in philosophy, But it's definitely a possibility.
Speaker 1: Meaning like you might get to a place down into
Speaker 1: the deep levels of the universe where there's not even math,
Speaker 1: like the idea of logic doesn't make any logical sense.
Speaker 2: Yeah, it could certainly be. I think a lot of
Speaker 2: people have in their minds the idea that the universe
Speaker 2: follows a very basic, simple set of laws, and that
Speaker 2: everything we experience emerges from that, the way that like
Speaker 2: molecules emerge from how protons and neutrons and electrons come together.
Speaker 2: But it could also be that the universe is quite
Speaker 2: different from that, that we have like islands of simplicity
Speaker 2: that we can understand with our mathematical laws, but that
Speaker 2: the rest is chaotic and undescribable, because fundamentally we don't
Speaker 2: understand why anything is understandable, why simplicity ever emerges, why
Speaker 2: there are scenarios that you can describe with pretty simple
Speaker 2: mathematical laws, even though there's a lot of stuff going
Speaker 2: on underneath. So we're not guaranteed to be able to
Speaker 2: understand the universe, or that the universe even is understandable
Speaker 2: or sensible.
Speaker 1: I wonder if you could also maybe get to a
Speaker 1: point where we figure out that math doesn't work the
Speaker 1: way we think it does. Like, for example, I'm thinking,
Speaker 1: like we learn in school that all the angles inside
Speaker 1: of a triangle have to add up to a one
Speaker 1: hundred and eighty degrees, and you just take that as
Speaker 1: a rule. That's just the way geometry in math works.
Speaker 1: But that rule doesn't work if you draw a triangle
Speaker 1: like on the surface of a ball, for example, like
Speaker 1: the angles add up to more than one eighty degrees.
Speaker 1: I wonder if what we think of as math is
Speaker 1: really just like one version of math, or it doesn't
Speaker 1: always work yea and one plus one maybe is not
Speaker 1: always two?
Speaker 2: Yeah, exactly. We might need some new creative generalizations of
Speaker 2: our kind of math in order to describe the universe.
Speaker 2: And we've already seen that several times. You're absolutely right,
Speaker 2: Like going from just real numbers two complex numbers was
Speaker 2: a huge mental step and allowed us crucially to develop
Speaker 2: the tools that explain quantum mechanics. We talked in the
Speaker 2: podcast once about developing quaternions, which are like complex numbers
Speaker 2: with one real and three imaginary numbers, and octonians with
Speaker 2: seven numbers, and we haven't even figured out what they're
Speaker 2: useful for So there could certainly be kinds of math
Speaker 2: we haven't invented yet that we need to explain the universe.
Speaker 2: M Well.
Speaker 1: The other part of Peter's question was could the universe
Speaker 1: be any different? Like could we maybe have the same
Speaker 1: rules but then have a totally different universe?
Speaker 2: Yeah, that depends a little bit on what you mean
Speaker 2: by rules. You know, you can mean, for example, the
Speaker 2: values of all the physical constants, like what is the
Speaker 2: mass of the electron and what is the mass of
Speaker 2: the proton and all this kind of stuff that we
Speaker 2: think could be different because that just depends on the
Speaker 2: energy in the Higgs field, which is set as the
Speaker 2: universe cools very very early on, and that could be different.
Speaker 2: Or you could be talking about more fundamentally, like the
Speaker 2: actual laws of quantum fields. Could those be different? And
Speaker 2: that's also possible. There's some theories of our early universe
Speaker 2: that say that, like, our entire universe is just one
Speaker 2: bubble in a huge multiverse filled with universe bubbles, and
Speaker 2: in each of them the physical laws could be different.
Speaker 2: We don't understand how the universe started or where the
Speaker 2: first hot, dense state initiated, and so it could be
Speaker 2: that each of those came into being from some previous state,
Speaker 2: and as they cool and create these bubble universes, that
Speaker 2: some random physical laws are created, and so there could
Speaker 2: be different laws.
Speaker 1: Well, I think that brings up maybe the real question
Speaker 1: about Peter's question, which is is it even possible to
Speaker 1: know why the universe is the way it is or
Speaker 1: whether it could be any different? Like, as you said,
Speaker 1: there might be other universes out there with different rules,
Speaker 1: but maybe by definition we can never get to them
Speaker 1: or communicate with them, or actually figure out if they exist.
Speaker 2: Yeah, I think we'll never experience those other universes if
Speaker 2: they do exist. This idea is called eternal inflation, and
Speaker 2: in that model, these bubble universes are expanding away from
Speaker 2: each other much much faster than the speed of life
Speaker 2: forever and so essentially impossible for us to ever experience
Speaker 2: them or communicate with them. But you know, we can
Speaker 2: think about the multiverse, even if we're only in our universe.
Speaker 2: We can think about other universes and whether they could
Speaker 2: possibly exist. We might get some clues from the structure
Speaker 2: of our universe and the laws that define it that
Speaker 2: give us an idea for how you might change those
Speaker 2: things like if we look at the fundamental laws of
Speaker 2: physics and there's a couple of arbitrary numbers in them,
Speaker 2: like a seven or a three or one point two four,
Speaker 2: then you can make arguments like, well, that could have
Speaker 2: been anything else. That could have been some other number,
Speaker 2: and so you could imagine another universe where that number
Speaker 2: is just different, or it could be we get to
Speaker 2: the fundamental law of the universe and there are no
Speaker 2: numbers and in no arbitrary choices, there's only one that
Speaker 2: makes mathematical sense. Then you might argue that any universe
Speaker 2: that's created has to be the same because there's only
Speaker 2: one choice for those set of laws.
Speaker 1: Right, we can always maybe imagine a different universe with
Speaker 1: different numbers, or maybe a universe where the laws where differently,
Speaker 1: or where math doesn't work at all. I guess what
Speaker 1: I'm trying to say is, since we can never experience
Speaker 1: or even tap into these other universes, does that mean
Speaker 1: we'll never get confirmation of these theories or these ideas
Speaker 1: that we have.
Speaker 2: We definitely can't do it definitively by experiencing those other universes.
Speaker 2: One way we could try to get maybe a hint
Speaker 2: about it, is to talk to aliens about science. Imagine
Speaker 2: if aliens come and we talk to them about science
Speaker 2: and they have a completely different theory of the universe,
Speaker 2: one that works just as well as ours, then what
Speaker 2: we thought was the way the universe is isn't actually
Speaker 2: the way the universe is. It's just like our description
Speaker 2: of it. That tells you that the whole philosophical question
Speaker 2: is really more about us than about the universe.
Speaker 1: Yeah, but these other aliens would also be trapped in
Speaker 1: the same universe we're in, so they would never also
Speaker 1: maybe be able to actually know for sure or get
Speaker 1: experimental evidence that the universe could have been some other way,
Speaker 1: or even why the universe is the way it is exactly.
Speaker 2: That's a scenario where nobody would know how the universe
Speaker 2: actually is, because it suggests that all of our physical
Speaker 2: theories ours the aliens. Anybody's peters are just descriptions. They're
Speaker 2: not revealing the truth about the universe. But on the
Speaker 2: other hand, if those aliens do have the same theories
Speaker 2: of physics, and we meet like five hundred other alien
Speaker 2: races and they all have exactly the same theories of physics,
Speaker 2: that suggests that maybe there is something about these maybe
Speaker 2: we have uncovered some truth and maybe we can learn
Speaker 2: something about the way the universe actually is and whether
Speaker 2: it could be different.
Speaker 1: I don't know. It seems like we're all stuck in
Speaker 1: the same universe, so we all have the same limited view.
Speaker 2: Yes, absolutely, this is just one way to measure like
Speaker 2: whether we're actually learning something about the universe or we
Speaker 2: all just reflecting the way our minds work. But it's
Speaker 2: definitely not a way to see other universes or to
Speaker 2: really understand There are some other hints in current theories
Speaker 2: of modern physics, like one of the leading candidates for
Speaker 2: a fundamental theory of the universe is string theory. And
Speaker 2: one issue in string theory is that there's like ten
Speaker 2: to the five hundred different string theories, all of which
Speaker 2: lead to different universes. And among those theories, one of
Speaker 2: them corresponds to our universe, and people wonder, like, are
Speaker 2: all those other universes also possible? Are they out there?
Speaker 2: People are working on this problem trying to figure out, like,
Speaker 2: are those other universes really possible or is it just
Speaker 2: something we haven't learned about them yet? But that's an
Speaker 2: example of a clue of looking at the fundamental theory
Speaker 2: and saying like, oh, there's lots of different options here,
Speaker 2: could have been very different.
Speaker 3: Hmmm.
Speaker 1: All right, well, I guess the answer for Peter is
Speaker 1: grow up to be an engineer.
Speaker 2: Yeah, Peter, it's a good question, it's a deep question.
Speaker 2: The answer is we don't know. We might never know.
Speaker 1: All right, Thank you, Peter. Now let's get to our
Speaker 1: other questions. We have questions here about quantum fields and
Speaker 1: quantum particles and about how particles decay, So let's get
Speaker 1: to those. But first let's take a quick break. All right,
Speaker 1: we're answering listener questions here today, and our next question
Speaker 1: comes from Ann.
Speaker 3: Hi, Daniel and Horse. Hey, my name is Ann. My
Speaker 3: question is this, does looking at the rules and the
Speaker 3: unanswered questions of physics from the perspective of quantum fields
Speaker 3: rather than particles, yield any new insights. I'm wondering about this,
Speaker 3: particularly with regard to how the various quantum fields interact
Speaker 3: with one another. For example, does thinking about entropy and
Speaker 3: the rules of particle decay from the perspective of the
Speaker 3: interaction of quantum fields give us any new insights into
Speaker 3: why of those phenomena? Thank you?
Speaker 1: Oh boy, I feel like we're getting a lot of
Speaker 1: philosophical questions and a lot of particle physics questions. Daniel,
Speaker 1: I wonder how we came to pick these questions.
Speaker 2: Maybe because we have a podcast about particle physics and
Speaker 2: I often digress into philosophy.
Speaker 1: Yeah, it could be maybe maybe. Yeah, I sense that
Speaker 1: little bias praaths.
Speaker 2: Oh, I see, you think I'm not randomly sampling the
Speaker 2: questions that we get. I'm definitely not randomly sampling the
Speaker 2: questions that we get.
Speaker 1: Oh no, I thought you answered all the questions.
Speaker 2: Oh I answered them all, I just don't put them
Speaker 2: all on the podcast. Retired engineers who send me their
Speaker 2: theories of everything, those don't make it on the podcast.
Speaker 1: Oh maybe we should. Let's have an episode where where
Speaker 1: we tackle all these theories that people send you.
Speaker 2: All right, let's do it. Everybody out there with your
Speaker 2: personal theory of the universe. Send it to me. I'll
Speaker 2: pick the best three and we will go through them
Speaker 2: on the podcast.
Speaker 1: All right, challenge issue, let's hear from you. All right, Well,
Speaker 1: this question, I'm not quite sure I understand it, but
Speaker 1: it's sort of about the different ways to look at
Speaker 1: the universe from a quantum perspective. One of them is
Speaker 1: thinking about the universe as quantum fields, and the other
Speaker 1: one is is quantum particles?
Speaker 2: Right, yeah, exactly. There are sort of two ways to
Speaker 2: think about the universe in terms of fields or in
Speaker 2: terms of particles. I think most people intuitively think about
Speaker 2: the universe in terms of particles, little bits of stuff
Speaker 2: flying through space, bouncing into each other and interacting. But
Speaker 2: on the podcast, we're often talking about things in turn
Speaker 2: of fields and the things and is wondering how do
Speaker 2: you think about the universe in terms of fields and
Speaker 2: whether that makes things.
Speaker 1: Easier easier than thinking about them is particles, right, yeah, exactly. Okay,
Speaker 1: So then what's the difference between looking at the universe
Speaker 1: as fields versus looking at it as particles?
Speaker 2: Well, particles are the things we see. When you see
Speaker 2: a flash of light on your retina, you're seeing a photon.
Speaker 2: When you have a screen and you're shooting electrons and stuff,
Speaker 2: those little dots electrons leave, those are particles you're seeing.
Speaker 2: So particles are like things we observe. And when people
Speaker 2: talk about like particles versus waves, what they really mean
Speaker 2: there by Particles are observations, our measurements are things we're
Speaker 2: directly seeing, and so in that sense, particles are like
Speaker 2: immediate there are experience of the universe. Fields are kind
Speaker 2: of something we imagine. They're part of our description of
Speaker 2: why things happen. Like when you have two particles flying
Speaker 2: through space, how do they interact with each other? Well,
Speaker 2: we imagine that each of them has a field, Like
Speaker 2: two electrons both have electric fields, and that's what the
Speaker 2: using the push and pull on each other. And then
Speaker 2: we can go even further and imagine, well, those particles
Speaker 2: are also just part of a field. Like instead of
Speaker 2: thinking about particles as little dots of stuff, think about
Speaker 2: them as little ripples, special kinds of waves in a
Speaker 2: special field and an electron field. And in that picture
Speaker 2: you have like an electron field which also creates an
Speaker 2: electromagnetic field, different thing which then can push on other
Speaker 2: bits of the electron field. So there's sort of two
Speaker 2: different ways of thinking about the universe, Like start with
Speaker 2: the observations that think about the particles or think about
Speaker 2: the fields.
Speaker 1: Right, But I guess the question is like what is
Speaker 1: exactly a field? Is it actually like a physical thing
Speaker 1: that exists in the universe, or is it just like
Speaker 1: a mathematical description of a physical effect between two things
Speaker 1: in the universe.
Speaker 2: Boom. You are officially a philosopher, Jorge.
Speaker 1: I know, I have a doctor in a philosophy, Daniel.
Speaker 2: That is a great question nobody knows the answer to.
Speaker 2: We do not know if fields are physical things that
Speaker 2: exist when physicists are not thinking about them, or if
Speaker 2: they're just calculational tools in our minds. That's the essence
Speaker 2: of the question of philosophy, of science, of physicalism. You know, essentially,
Speaker 2: are all these ideas real or are they just our descriptions.
Speaker 2: And the thing is that we can ever see fields directly.
Speaker 2: We only ever see fields impact on particles. How do
Speaker 2: you measure an electric field? You're put an electron in
Speaker 2: it and you see the effect on the electron. Same
Speaker 2: with magnetic fields. So we don't know if fields are real.
Speaker 2: There's even a guy who suggested that fields are made
Speaker 2: up and we don't need them, and he invented a
Speaker 2: whole new kind of science that didn't even require mathematics.
Speaker 2: It's called science without numbers. He's a philosopher, and ironically
Speaker 2: his last name is Fields.
Speaker 1: Maybe he should study irony ines.
Speaker 2: That Professor Fields proves there are no.
Speaker 1: Fields but I guess maybe I wonder if you can
Speaker 1: make an argument that fields are tangible or not that
Speaker 1: they're not tangible, Like do fields have energy inherent in
Speaker 1: them or mass or does this energy that particles and
Speaker 1: the massive particles have does it come into existence when
Speaker 1: the particles are created.
Speaker 2: Fields themselves definitely have energy. They can have potential energy,
Speaker 2: and that can have kinetic energy, and they can oscillate.
Speaker 2: So if they are real, then they're out there, you know,
Speaker 2: swishing and slashing around and doing things and some kinds
Speaker 2: of oscillations we observe as particles even when we're not
Speaker 2: observing them. They can have energy, like the Higgs field
Speaker 2: has a bunch of potential energy stored in it, and
Speaker 2: that potential energy affects how other fields oscillate, and so
Speaker 2: those fields definitely have energy.
Speaker 1: But where is that energy? I guess, like is it
Speaker 1: floating out there in space? Is it in between my particles?
Speaker 1: Or does that energy come into existence when that field
Speaker 1: gets activated? You know what I mean? Like, does it
Speaker 1: come from somewhere or does it just get magically created
Speaker 1: when you need it?
Speaker 2: It doesn't just get magically created, though, I would love
Speaker 2: that while I'm going to create a power plant that
Speaker 2: relies on magical creation of energy. That sounds awesome.
Speaker 1: Well, that is what's happening in the universe, though, isn't it.
Speaker 1: As the universe expands, the energy is coming out and nothing.
Speaker 2: No, you're absolutely right. As space is expanding, energy is
Speaker 2: increases and it's not coming from anywhere, it's not coming
Speaker 2: out of nothing. It just increases. And that tells you
Speaker 2: that energy is not actually a fundamental quantity in the universe.
Speaker 2: That's sort of a complication. You can also imagine flat
Speaker 2: space that's not expanding, and in that situation energy is served.
Speaker 2: And we could talk about how energy flows between fields,
Speaker 2: and I think that's something and was sort of asking about,
Speaker 2: like to get a picture of how energy is flowing.
Speaker 2: If you have the picture of the universe is all fields,
Speaker 2: you know, you're asking like, where's that energy come from?
Speaker 2: And so start with the photon. For example, a photon
Speaker 2: is a pulse in the electromagnetic fields. It's a traveling wave,
Speaker 2: it's a ripple in that field, and that's energy it's
Speaker 2: flying through the universe. Now, imagine that photon then converts
Speaker 2: into an electron and a positron, so two particles that
Speaker 2: actually have mass. Right, You've gone from a massless photon,
Speaker 2: which is a special kind of ripple in the electromagnetic field,
Speaker 2: into two matter particles. While that energy flows from the
Speaker 2: electromagnetic field into the electron field and creates two special
Speaker 2: ripples in the electron field. That energy has flowed into
Speaker 2: the electron field.
Speaker 1: Does it technically flow from one field to the other
Speaker 1: or does it get annihilated and then it somehow gets
Speaker 1: created in the other field.
Speaker 2: I guess I'm not sure what the distinction is there.
Speaker 2: Mathematically we talk about these fields interacting. They couple together,
Speaker 2: so energy is transferred from one field to the other.
Speaker 2: It never exists in some sort of in between state,
Speaker 2: not in any fields, either in this field or in
Speaker 2: that field.
Speaker 1: All right, Well, maybe a part of the question that
Speaker 1: Ann is asking, or at least that I have about
Speaker 1: Ann's question, is like, why do we have to pick
Speaker 1: between a field's view and a particle view of the universe?
Speaker 1: Aren't they all part of the same view. Aren't particles
Speaker 1: just ripples and the fields and aren't fields just what
Speaker 1: ripples to make a particle?
Speaker 2: Yeah, it's a great question. They are fundamentally different views
Speaker 2: of what's the basic stuff in the universe. The particle
Speaker 2: of view is saying particles are the fundamental building blocks
Speaker 2: of everything. Everything is a particle. And in that description,
Speaker 2: when two electrons are flying along and they're pushing on
Speaker 2: each other, there's no field between them. They're shooting virtual
Speaker 2: particles back and forth, and so there just are no
Speaker 2: fields in that picture. It's all particles. And in the
Speaker 2: field's picture, the fields are the fundamental building block of
Speaker 2: the universe. They are at the root of everything, and
Speaker 2: particles are just ripples in those fields, including photons and
Speaker 2: including electrons and including everything. Now, both of these theories work.
Speaker 2: They give exactly the same predictions for all experiments. They're
Speaker 2: mathematically equivalent. An infinite number of virtual particles is the
Speaker 2: same as a field that has exactly the same effect.
Speaker 2: You get exactly the same answer.
Speaker 1: Wait, did you say an infinite number of particles? What
Speaker 1: do you mean?
Speaker 2: The version of the story where you have virtual particles
Speaker 2: instead of fields requires an infinite number of virtual particles
Speaker 2: to give the same explanation as you get from fields.
Speaker 1: Like an infinite number in the universe, or like in
Speaker 1: my hand.
Speaker 2: An infinite number for every interaction, every electron pushing against
Speaker 2: another electron technically involves an infinite number of possible virtual
Speaker 2: particles because they're not observed, and so like that virtual
Speaker 2: photon could have had this momentum or that momentum or
Speaker 2: slightly different momentum. It's the sort of path integral version
Speaker 2: of quantum mechanics. We integrate over every unobserved possibility.
Speaker 1: But I guess could the answer be just like it's both.
Speaker 2: Well, that sort of goes to your question, like what's
Speaker 2: really happening out there in the universe. Fundamentally it's a
Speaker 2: philosophy question because the physics works either way. But we
Speaker 2: want to know, or we want to know the truth
Speaker 2: about the universe, like what's really happening out there? And
Speaker 2: only one of those at most is true. It could
Speaker 2: be that they're both wrong. It's neither particles nor fields.
Speaker 2: It's something else quigly knows, or something right, or some
Speaker 2: other idea. But I like to believe that there is
Speaker 2: a truth that something is happening out there in the
Speaker 2: universe and it could be described, and I'd like to
Speaker 2: know which it is. So if particles or fields, if
Speaker 2: one of those makes more sense somehow is more compact,
Speaker 2: then maybe it's more likely to be what's really happening
Speaker 2: out there in the universe. But it's a great example
Speaker 2: of what we were talking about a minute ago about
Speaker 2: how you can have multiple explanations for the universe and
Speaker 2: not know what's really.
Speaker 1: Happening, right right, Like, I wonder if you can ask,
Speaker 1: does the universe actually care?
Speaker 2: I care, and I'm part of the universe.
Speaker 1: Like maybe the universe doesn't care. Maybe there isn't a
Speaker 1: need in the universe for things to make one thing
Speaker 1: to make more sense than the other in.
Speaker 2: This little corner of the universe that I call Daniel Whitson,
Speaker 2: there's a strong need for the universe to make sense.
Speaker 1: Well, I guess that makes sense because you are a physicist.
Speaker 2: We're all philosophists out there, right, and philosophers we all
Speaker 2: want to know how the universe works and what it means, right, Peter, right.
Speaker 1: Right, we all need to grow up polluted or not.
Speaker 1: All right, Well, thank you Ann for that awesome question.
Speaker 1: Now let's get to our last question of the day,
Speaker 1: and this one is about how particles decay. So let's
Speaker 1: get to that. But first, let's take another quick break. Right,
Speaker 1: we're tackling listener questions, and so Our next question comes
Speaker 1: from Alchilan, a twelfth grade student in India.
Speaker 4: Hello, I'm a twelfth grade student in India. So here's
Speaker 4: my question. In negative beta decay, a neutron is converted
Speaker 4: into a proton, an electron, and an anti neutrino. We
Speaker 4: know that a neutron is made of quirks, So where
Speaker 4: did the anti neutrino and the electron come from?
Speaker 3: Really?
Speaker 1: All right, pretty basic question, Daniel. How does it work?
Speaker 1: How does anything work?
Speaker 2: How does the universe all work? Anyway? Yeah? Cool question,
Speaker 2: And it's a fun question because it gives you a
Speaker 2: little bit of a window into the history of physics
Speaker 2: because what we thought about beta decay changed over the
Speaker 2: last hundred years as our understanding of fundamental physics changed. Like,
Speaker 2: we've seen beta d K for a long time. These days,
Speaker 2: we have an explanation of it in terms of quarks,
Speaker 2: but we've been studying and thinking about beta decay long
Speaker 2: before we even knew about quarks.
Speaker 1: Well, me, let's take a step back and tell what
Speaker 1: exactly is beta decay?
Speaker 2: Yeah, so betak's when you have a neutron and it
Speaker 2: turns into a proton. Not because charge is concerned in
Speaker 2: the universe. You can't just turn a neutral neutron into
Speaker 2: a positively charged proton. You have to also create something
Speaker 2: else to balance the charge. So a neutron decays, it
Speaker 2: produces a proton plus an electron, and then, because the
Speaker 2: universe doesn't allow you to just make electrons, it keeps
Speaker 2: track of the number of electrons in the universe, you
Speaker 2: have to also make something to balance the number of electrons. Fortunately,
Speaker 2: electron neutrinos also count as electrons, so if you make
Speaker 2: an anti electron neutrino, then you balance all the accounting.
Speaker 2: So neutron turns into a proton, an electron, and an
Speaker 2: anti electron neutrino.
Speaker 1: Wow, this is a very specific event. Why do they
Speaker 1: call it a decay in the first place.
Speaker 2: They call it a decay because a neutron is turning
Speaker 2: into something else, and decay is just what we mean
Speaker 2: when particles transform. Really we call it decay. It sounds
Speaker 2: like they're breaking up out of old age or something,
Speaker 2: but it's really just an interaction of transformation.
Speaker 1: Yeah, it sounds like they're you know, like rotten.
Speaker 2: Yeah, exactly, like I bought this thing.
Speaker 1: Well, I'm trying to say, is doesn't the proton, the electron,
Speaker 1: and the anti neutrino feel offended that they're the product
Speaker 1: of a decay.
Speaker 2: What's offensive about being a decay product? You know, that's great.
Speaker 2: I'm a product of my parents and then my parents decay, right,
Speaker 2: I don't know, it's just the way of the universe.
Speaker 1: No, But what if I say, like, you're the product
Speaker 1: of your parents decaying.
Speaker 2: I don't know how to feel about that. Yeah, exact
Speaker 2: protons don't have any feelings. I don't think they care
Speaker 2: unless you believe in panpsychism.
Speaker 1: Well, so is this beta decay an important interaction or
Speaker 1: transformation that happens in particle physics? Does it happen a lot?
Speaker 1: Is it significant? Is it important for any sort of
Speaker 1: big process?
Speaker 2: I think it's really important because it reveals a lot
Speaker 2: about the way the universe works, and historically it's been
Speaker 2: the source of a lot of discoveries. So neutrons are
Speaker 2: actually unstable in general. Like you have a neutron out
Speaker 2: there in the universe, it'll lasts for like about eleven
Speaker 2: minutes on its own before it beta decays into a proton,
Speaker 2: electron and an anti neutrino, And it reveals something about
Speaker 2: the universe, like the reason we discovered neutrinos was because
Speaker 2: of beta decay. People were looking at neutrons and they
Speaker 2: saw them break up into protons and electrons, but the
Speaker 2: neutrino was invisible. Neutrinos hardly ever interact, and so nobody
Speaker 2: saw the neutrino. And it's only because they noticed that
Speaker 2: the momentum didn't add up like you had the momentum
Speaker 2: of the experiment before and after the decay, and they
Speaker 2: didn't equal each other. People were wondering, hmm, is momentum
Speaker 2: not conserved in the universe or is there some little
Speaker 2: invisible particle carrying off that momentum? And that's how the
Speaker 2: neutrino was first postulated.
Speaker 1: Interesting now, I guess maybe a question I have is
Speaker 1: how do you even get a neutron on its own
Speaker 1: to see it decay?
Speaker 2: I think you can just order them on Amazon, right.
Speaker 1: Can you really? Next day? Is it free shipping because
Speaker 1: technically it's neutral.
Speaker 2: No, you cannot just order neutrons because they're unstable. So
Speaker 2: unless Amazon can deliver them to you in less than
Speaker 2: eleven minutes, you're going to get a box of proutons, electrons,
Speaker 2: and neutrino.
Speaker 1: Well they have. They just put them in a cooler.
Speaker 1: Isn't that how it works?
Speaker 2: Yeah, right exactly. Or you can accelerate them near the
Speaker 2: speed of light so their time is dilated or.
Speaker 1: I guess I mean like in those early days, in
Speaker 1: those experiments, how did they isolate a neutron to see
Speaker 1: what it decayed into?
Speaker 2: Yeah, good question. We actually have a whole episode about
Speaker 2: the discovery of the neutron. It's a little bit subtle
Speaker 2: because the neutron is neutral, but there's some really fascinating
Speaker 2: early experiments to prove that the neutron exists and has
Speaker 2: a different math a the proton. But basically the neutron
Speaker 2: is produced in radioactive decay. So in big heavy nuclei
Speaker 2: I break apart, they often produce neutrons in the process
Speaker 2: because you start out with like a huge pile of
Speaker 2: protons and neutrons, sometimes more than one hundred, and you
Speaker 2: make lighter atoms and you don't need always all those neutrons,
Speaker 2: and so some of them fly out. So if you
Speaker 2: have like uranium or other radioactive substances, they will just
Speaker 2: produce neutrons and you can use them to study well.
Speaker 1: I see, they just like emanate neutrons, like they just
Speaker 1: shoot off neutrons in all directions.
Speaker 2: Yeah, exactly, Yes, so they're sources of neutrons all right.
Speaker 1: Then Aileen's question was how does it work? Like, how
Speaker 1: does I guess? How does any decay work, or how
Speaker 1: does any of these particle transformations work. I feel like
Speaker 1: that's what he's trying to get at, you know, is
Speaker 1: like what's actually happening. Does it actually transform or does
Speaker 1: it annihilate into pure energy or does it go into
Speaker 1: the void of the universe and then come back. It's
Speaker 1: a different thing. What's going on?
Speaker 2: Yeah? I think something Aline is trying to get at
Speaker 2: is like, were the neutro trino and the electron inside
Speaker 2: the neutron? Like if a neutron breaks up into a proton,
Speaker 2: electron and neutrino, does that mean it was made of
Speaker 2: those things? That's sort of what we expect in chemistry.
Speaker 2: For example, when you take water and you make it
Speaker 2: into hydrogen and oxygen, that tells you water was made
Speaker 2: of hydrogen and oxygen. But that's not true in particle physics.
Speaker 2: It's something very very different going on. As you say,
Speaker 2: new particles can be created from the energy of the
Speaker 2: other particles sexually related to what we were talking about
Speaker 2: a minute ago. The energy can slide from one kind
Speaker 2: of field into another kind of field. So he's asking
Speaker 2: where did the neutrino and the electron come from. They
Speaker 2: weren't inside the neutron. They were made from the energy
Speaker 2: that was stored inside.
Speaker 1: The neutron, meaning like the neutron became pure energy and
Speaker 1: then that energy manifested itself as other particles close.
Speaker 2: And that's actually what Fermi's theory was. Fermi didn't know
Speaker 2: what was going on inside the neutron, so he had
Speaker 2: this idea that maybe neutrons of protons are fundamental particles,
Speaker 2: and the neutron is disappearing, and then that energy is
Speaker 2: turning into a proton, electron and anti neutrino. These days,
Speaker 2: we know that's not actually true. We have a more
Speaker 2: detailed understanding what's happening. As Achilon says, these particles are
Speaker 2: made of quarks, So the proton is three quarks up,
Speaker 2: up and down. So a neutron is three quarks and
Speaker 2: up and two down quarks, and beta decay is when
Speaker 2: one of those two down quarks flips to being an upquark.
Speaker 2: So you go from up down down to up up down.
Speaker 2: That's going from neutron to proton.
Speaker 1: Wait, what do you mean it flips like just randomly
Speaker 1: or does it read something on the internet and then
Speaker 1: decided to switch sides.
Speaker 2: Well, this is particle decay. Neutrons are unstable. Sometimes randomly
Speaker 2: they will convert into a proton, electron and anti neutrino
Speaker 2: because that's what the universe likes to do. It likes
Speaker 2: to spread its energy out. The neutron is sort of
Speaker 2: like a high energy combination of these particles, and the
Speaker 2: universe likes to decay down to lower energy states because
Speaker 2: there are more possibilities there. It's essentially entropy at the
Speaker 2: particle level. We have a whole podcast about why particles
Speaker 2: decay at all.
Speaker 1: So then these new arrangement of particles that are created
Speaker 1: are less energy than the neutron.
Speaker 2: Yeah, exactly. The proton is lower energy than the neutron,
Speaker 2: and that's why the proton is stable and doesn't decay
Speaker 2: into a neutron because the neutron is a higher energy
Speaker 2: combination of these particles, and that energy gets turned temporarily
Speaker 2: into a w boson. A w boson then turns into
Speaker 2: the electron and anti neutrino, so that energy.
Speaker 1: Wait, why do you need this intermediate step?
Speaker 2: Why do you need that intermediate step? Is a great question.
Speaker 2: This is a description of what's happening in the universe.
Speaker 2: This is only mathematically consistent and accurate description of what
Speaker 2: we see. Could you invent a universe without a w
Speaker 2: boson where this happens directly, maybe that would be a
Speaker 2: different universe. We definitely know that there is a w
Speaker 2: boson made.
Speaker 1: Like, how do you know there is an intermediate step?
Speaker 1: How do you know it isn't just converting directly?
Speaker 2: Yea, it's a great question. And when people came up
Speaker 2: with this theory, they predicted that the w boson was
Speaker 2: a thing, and if it was, we should be able
Speaker 2: to see it in high energy colliders. And we built
Speaker 2: a large electron positron collider at Cerne and Carlo Rubia
Speaker 2: discovered the w boson there. He made it and show
Speaker 2: that it is a real thing and got the Nobel
Speaker 2: Prize for it. It was a very nice description and
Speaker 2: it made a prediction which was then proven correct.
Speaker 1: So then what would be your answer for alan that
Speaker 1: things just sort of convert into pure energy, or that
Speaker 1: these energies are slashing between fields.
Speaker 2: I would say that what's really happening is a down
Speaker 2: cork is decaying into an upcork, and this extra energy
Speaker 2: left over, and that's where the electron and neutrino come from.
Speaker 2: That energy then ends up in the electron and neutrino
Speaker 2: fields if you like the field picture. The electron and
Speaker 2: neutrino were never inside the neutron. They're made from the
Speaker 2: extra energy as it decays.
Speaker 1: But I guess you sound very confident about this. But
Speaker 1: and also the possibility that maybe all of these things
Speaker 1: that we call fundamental particles like quarks and electrons, maybe
Speaker 1: they're made out of even smaller lego blocks or smaller
Speaker 1: tiny particles, in which case maybe these interactions are sort
Speaker 1: of like chemistry, where you know, things are not transforming
Speaker 1: into energy, they're just breaking up into their smaller pieces,
Speaker 1: and those smaller pieces are rearranging themselves into these other particles.
Speaker 2: Yes, you're absolutely right, and my description is just what
Speaker 2: we currently think is happening, which of course is limited
Speaker 2: because we don't know fundamentally what's really happening and what's
Speaker 2: inside these particles, if anything, and even in just the
Speaker 2: last seventy years, or so that's changed, right, Fermi, describe
Speaker 2: this in terms of a neutron proton as fundamental particles.
Speaker 2: And now, as you say, we have a deeper picture
Speaker 2: of what's going on inside those particles, and that might change.
Speaker 2: It might be that our theory only works up to
Speaker 2: a certain energy, and beyond that we need to describe
Speaker 2: it in terms of even smaller particles. But this is
Speaker 2: our current picture.
Speaker 1: Because we don't know if those tiny building blocks exist.
Speaker 2: But they could, right, They certainly could. Yes, they very
Speaker 2: likely do, because it would explain a lot of weird stuff.
Speaker 2: We see patterns that are unexplained in the current particles
Speaker 2: that probably are due to the way heinier things inside
Speaker 2: the electron and neutrino and quarks are clicking together to
Speaker 2: make the particles that we see and study.
Speaker 1: Wait, so then if these tiny, smaller particles exist, does
Speaker 1: that mean that the electron field doesn't really exist?
Speaker 2: I mean, the proton definitely exists as a thing, even
Speaker 2: if it's not a fundamental particle. It's made of quarks,
Speaker 2: but it's a bound state of those quarks. If the
Speaker 2: electron is not a fundamental particle, it means that the
Speaker 2: electron field is a useful mathematical description of something that's
Speaker 2: not fundamental but instead is a bound state of other
Speaker 2: fields interacting in a way that looks just like an
Speaker 2: electron field when you sort of zoom out right right,
Speaker 2: it wouldn't exist for real. It's not fundamental, but like
Speaker 2: you exist. You're not fundamental, you're made of smaller things.
Speaker 2: But I still think you exist.
Speaker 1: Yeah, I exist in as an arrangement of things.
Speaker 2: Yes, Jorge exists, but the Joorge field doesn't. I guess
Speaker 2: it's what you're saying.
Speaker 1: That's what I mean. Unless my last name is Field.
Speaker 2: Then you'd really be a philosopher.
Speaker 1: All right, Well, I think the answers Ahinan's question. I
Speaker 1: think for the third time today the answer is nobody knows,
Speaker 1: not even philosophers or elderly engineers, which I think now
Speaker 1: technically I fall into that category.
Speaker 2: I think we have a pretty good picture of what's
Speaker 2: going on in terms of our current understanding of the universe.
Speaker 2: But of course we expect and hope and look forward
Speaker 2: to the day that understanding is upended for a deeper understanding.
Speaker 1: Well, and in the meantime, let's keep asking questions. Don't
Speaker 1: forget to be curious about the universe, to think of questions,
Speaker 1: and to share those questions with others. We hope you
Speaker 1: enjoyed that. Thanks for joining us. See you next time.
Speaker 2: For more science and curiosity, come find us on social
Speaker 2: media where we answer questions and post videos. We're on Twitter, Discorg, Insta,
Speaker 2: and now TikTok. Thanks for listening, and remember that Daniel
Speaker 2: and Jorge Explain the Universe is a production of iHeartRadio.
Speaker 2: For more podcasts from iHeartRadio, visit the iHeartRadio app, Apple Podcasts,
Speaker 2: or wherever you listen to your favorite shows.