Speaker 1: Or Hey, did you have a good snack before you
Speaker 1: just hit record? I did. I just finished the banana, actually,
Speaker 1: And is that banana enough energy to power you for
Speaker 1: a whole hour? Depends on what I'm doing that hour.
Speaker 1: You know, procrastination doesn't take much energy. Well, it's amazing
Speaker 1: to me that you can turn bananas into physics podcasts.
Speaker 1: That amazes you as a physicist. Isn't all energy conserved?
Speaker 1: Shouldn't be possible from a physics point of view? Yeah,
Speaker 1: it might even be possible to do the opposite, right,
Speaker 1: to turn physics podcasts back into bananas. What wouldn't that
Speaker 1: violate the laws I don't know of physics, because imagine
Speaker 1: all those thousands of people out there with this podcast
Speaker 1: turning this into a banana. There must be some loss, though,
Speaker 1: I think they would end up with a smaller banana
Speaker 1: than the when you started with, or overly ripe banana.
Speaker 1: Maybe that's a good way to describe podcast. Maybe you
Speaker 1: can think of I heart media is basically amplifying your
Speaker 1: original banana. That's bananas, Daniel. At least you're feeding your
Speaker 1: mind as well as your body. I am more handmade
Speaker 1: cartoonists and the creator of PhD comics. Hi, I'm Daniel.
Speaker 1: I'm a particle of physicist and a professor at UC Irvine,
Speaker 1: and I am sending you all physics energy, physics vise
Speaker 1: or knowledge is knowledge energy? Daniel, there's a question about
Speaker 1: whether information has mass. So if it does, the information
Speaker 1: would have energy and knowledge is information, So in some
Speaker 1: weird theories of the universe, maybe it does. Wait what
Speaker 1: information might have mass? So all those people listening to this,
Speaker 1: we're increasing their mass only if we actually put some
Speaker 1: information into this podcast. So far, it's just banana jokes,
Speaker 1: basic cholesterol. You know, there's good information and there's bad information.
Speaker 1: Which one is healthier for you? Scientists are still debating it. Yeah,
Speaker 1: stay tuned as they gather more information to answer this question.
Speaker 1: But anyways, welcome to our podcast, Daniel and Jorge Explain
Speaker 1: the Universe, a production of I Heart Radio in which
Speaker 1: we try to sift through all the information humanity has
Speaker 1: gathered about the crazy universe that's out there. We try
Speaker 1: to systematize, we tried to organize, We tried to educate
Speaker 1: you on what we do know and what we don't
Speaker 1: know about this crazy universe, how it works, how things
Speaker 1: slosh and flow around, how it comes together to make
Speaker 1: this incredible, beautiful and dangerous universe that we all love. Wait,
Speaker 1: are you saying that our job here is to take
Speaker 1: everything that's beautiful in the universe, chew it up, eat it,
Speaker 1: and then regurgitated back to people as information edible information.
Speaker 1: I'm not sure which side it comes out, but yeah,
Speaker 1: we consume it and then produce it. It's not a
Speaker 1: pretty picture either way, is it. I like to think
Speaker 1: of it as all part of the information food web.
Speaker 1: You know, don't think so much about who is eating
Speaker 1: who as much as you know information is flowing from
Speaker 1: person to purses. We're all just stardust and predigested information. Yeah,
Speaker 1: although maybe you are the information super predator. You're the
Speaker 1: apex information consumer. Oh I really huh? And nobody has
Speaker 1: ever called me the apex anything. Well, think about it.
Speaker 1: You talked to lots of scientists, and you distill from
Speaker 1: all of them little bits of crucial science knowledge. Wow,
Speaker 1: maybe that's why I'm so full all the time. It's
Speaker 1: a lot of bananas to keep that. Or you're just
Speaker 1: consuming all those scientists brains effectively. That makes you so
Speaker 1: like a science zombie. I'm not sure now, zombie too.
Speaker 1: Oh my goodness. First I was regurgitating. Now I'm stumbling
Speaker 1: around half dead. Actually that that is pretty accurate these days,
Speaker 1: at this time in the morning. You do a good
Speaker 1: zombie impression. Now you told me zombies don't always stumble
Speaker 1: is sometimes zombies are fast moving and even articulate. Yeah, yeah,
Speaker 1: it's kind of zombies. Yeah, then the new kinds of
Speaker 1: zombies are now fast and furious. We've got a lot
Speaker 1: of response from the Zombie Star episode, people writing in
Speaker 1: recommending zombie movies that they thought I might enjoy. Oh good,
Speaker 1: are you gonna watching? Do you need an honest answer
Speaker 1: to that question? Why? Well, why not? There's too many
Speaker 1: things out there to watch. So they're on my list,
Speaker 1: but I might not make it. I see, that's the
Speaker 1: political answer, got it, got it. But thank you everyone
Speaker 1: for your suggestions. I will get to them eventually. Well
Speaker 1: I'm curiously know what's on that list. But today we're
Speaker 1: talking about something a little bit different than Zombie Stars.
Speaker 1: That's right. We are venturing into the border between physics
Speaker 1: and philosophy. We are not just trying to understand how
Speaker 1: the universe work, We're trying to understand what it means,
Speaker 1: because physics is more than just a list of laws.
Speaker 1: It's an attempt to get some deep intuitive understanding into
Speaker 1: how the universe works, to reach those ah ha moments
Speaker 1: where you feel I get it. I understand something now
Speaker 1: about how the universe is doing it that I didn't
Speaker 1: understand before. Wait. Wait, wait, wait, we're going into philosophical
Speaker 1: territory here. Can we go back to the zombies? Well,
Speaker 1: we can talk about philosophical zombies if you like. That's
Speaker 1: one of my favorite topics, or the philosophy of zombies.
Speaker 1: M like, is a zombie still a person or not? No,
Speaker 1: that's philosophy by zombies. You know, they have whole journals
Speaker 1: that only zombies, right for Oh no, it is kind
Speaker 1: of a half that discipline. Anyways, you know, the the
Speaker 1: overlap between physics and philosophy is very healthy, very vibrant,
Speaker 1: really fascinating, and for me, one of the motivating aspects
Speaker 1: of physics. One reason we do physics is to help
Speaker 1: answer questions, which, in the end our philosophical what does
Speaker 1: it mean to be alive? Why are we here? What
Speaker 1: should we do with our lives? How do we make
Speaker 1: sense of this cosmos? Those aren't science questions, but the
Speaker 1: answers to science questions can help us understand how to
Speaker 1: tackle those other more difficult philosophical questions. Yeah, because I
Speaker 1: guess it is a pretty incredible universe, and even though
Speaker 1: we may want to understand how it all works, there's
Speaker 1: still sort of the questions that you can ask beyond that,
Speaker 1: beyond physics, right, like what does it mean? Or why
Speaker 1: are we here? And some of those questions are really
Speaker 1: simple signing questions, the kind of questions you often ask
Speaker 1: me when I start talking about something complicated and you're like,
Speaker 1: hold on, back up, what are we even talking about?
Speaker 1: Can you give me a definition of space or mass?
Speaker 1: What are these things we're talking about? Do we really
Speaker 1: understand them? Yeah, because I guess you know, you grew
Speaker 1: up in this universe and maybe you become a physicist
Speaker 1: or not, but you still kind of study it, and you,
Speaker 1: you know, you start to take things a little bit
Speaker 1: for granted, you know, in a way, you know, you know,
Speaker 1: we think about the fact that we walk around on
Speaker 1: this planet, but why are we stuck to this planet
Speaker 1: at all and not floating out there in space. Yeah,
Speaker 1: it's a really important exercise to take a step back
Speaker 1: and say, what is this thing we're talking about, What
Speaker 1: does it really mean? What do we know about it?
Speaker 1: What can we learn about the nature of the universe
Speaker 1: from what we know about how these physical processes happen. Yeah,
Speaker 1: it always amazes me that there are basic concepts and
Speaker 1: physics that physicists don't really have a good definition for
Speaker 1: or a good explanation for. You know, we've covered a
Speaker 1: lot of them in our book. We have No Idea
Speaker 1: a guide to the Unknown Universe. But it's still amazing
Speaker 1: that there are things that even we didn't cover in
Speaker 1: the book that physicists still struggle to define. You don't
Speaker 1: have to know what you're talking about to sometimes accomplish
Speaker 1: something in physics. The most famous example is quantum mechanics.
Speaker 1: Nobody really understands what it means, but we can do
Speaker 1: really complicated, really accurate calculations and predictions using quantum mechanics,
Speaker 1: even if we don't quite grasp what exactly is going on. Yeah,
Speaker 1: and maybe out of all those basic concepts about the universe,
Speaker 1: there are maybe none more basic than the idea of energy.
Speaker 1: That seems like a super duper basic concept in physics.
Speaker 1: It is, in fact, and it's something a lot of
Speaker 1: listeners over the years have written in to ask us
Speaker 1: to talk about so to the on the podcast will
Speaker 1: be tackling the question what is energy? And where can
Speaker 1: we get some more of it? Yeah? That's not coming
Speaker 1: from a coffee cup maybe or dead plants underground. But
Speaker 1: it is kind of sort of an interesting question, I
Speaker 1: think because it's so short, right, Like, this is one
Speaker 1: of the shortest questions we've tackled in a long time
Speaker 1: on this podcast. It's just three words, what is energy?
Speaker 1: Maybe we should add a fourth one man, what is energy? Man?
Speaker 1: What is energy? Anyway? Or maybe what? I guess we
Speaker 1: could go deeper, we go what is Eventually we'll just
Speaker 1: be asking the question what. Maybe that's all physics and
Speaker 1: philosophy is just responding to the universe and going what. Yeah,
Speaker 1: but then we will, you know, like a Marvel movie
Speaker 1: will find another sequel. We'll go with where or Speechless
Speaker 1: the new seel. But it is a really simple sounding
Speaker 1: question with a lot of subtle nuances, which is why
Speaker 1: it took us a little while to figure out how
Speaker 1: to attack it. It's a short question without an the
Speaker 1: simple answer. Yeah, I was thinking about this word and
Speaker 1: it's kind of interesting. Because I think everyone you know
Speaker 1: knows the word obviously energy and has something you know,
Speaker 1: some some intuitous sense attached to it. But you know,
Speaker 1: if you sort of think about what is it, it's
Speaker 1: kind of hard to define. Yeah, you're used to talking
Speaker 1: about it, you think about it in your life, you
Speaker 1: pay for it, you use it. But if you sit
Speaker 1: on your couch late at night and wonder, like, what
Speaker 1: is it? Has seems to have so many forms, they
Speaker 1: can transform back and forth into each other. It's a
Speaker 1: vital part of the universe. It feels like it should
Speaker 1: be something fundamental. But is a physical thing? Is it
Speaker 1: just a calculation that we do? Is it a philosophical question?
Speaker 1: It's a really hard thing to grapple with. Yeah, and
Speaker 1: even physicists in their textbooks have sort of a hard
Speaker 1: time pinning this down right. I mean, there is sort
Speaker 1: of an official definition of it, right as the capacity
Speaker 1: to do work. Yeah, there is that definition. But then
Speaker 1: you look at the official definition of work and its
Speaker 1: energy transfer a lot, it moves back on itself, like inception, Yeah, exactly,
Speaker 1: deaf nisition ce definition. So energy is defined in terms
Speaker 1: of work, and work is defined in terms of energy,
Speaker 1: So like, what is this thing we're talking about. Wow. Interesting, Yeah,
Speaker 1: because I guess that's the only way we know how
Speaker 1: to define it. Kind of maybe, sort of, And you
Speaker 1: have to grapple with the subtlety between physics definitions like
Speaker 1: what we technically mean by work and our intuitive understanding
Speaker 1: of these concepts, because physics often repurposes a word that
Speaker 1: everybody uses a normal language to mean something very specific
Speaker 1: and technical. For physics, that's true for example for work. Interesting. Well,
Speaker 1: let's start to dig into this, but first, as usually,
Speaker 1: we're wondering how many people out there have thought about
Speaker 1: this very basic question and how many people out there
Speaker 1: think they know the answer to this. So thanks very
Speaker 1: much to everybody who volunteered to answer difficult, random questions
Speaker 1: from an internet physicist. I really appreciate your work. And
Speaker 1: if you're out there and have been listening to the
Speaker 1: podcast and want to put your roove always to these questions,
Speaker 1: please don't be shy. Send me an email two questions
Speaker 1: at Daniel and Jorge dot com. Think about it for
Speaker 1: a second. What do you think energy is or how
Speaker 1: would you explain it? Here's what people had to say. Um,
Speaker 1: I remember learning in maybe high school physics that energy
Speaker 1: is the ability for something to do work. UM. I
Speaker 1: think that that's probably not nuanced enough of a definition.
Speaker 1: More nuanced way to look at it might be it's
Speaker 1: um something's ability to affect change, which doesn't necessarily have
Speaker 1: to be work, and sort of like the classic physics definition.
Speaker 1: I think energy is truly just a vibration, and the
Speaker 1: energy potential is dictated by the field the vibration or
Speaker 1: string sits with him. I've asked this question to someone
Speaker 1: who knew a lot about physics before, and their answer
Speaker 1: was not useful to me. What I came away with
Speaker 1: is like energy is potential for things to happen, and
Speaker 1: concentrations of that potential, and it's expressed in a lot
Speaker 1: of ways. This feels like it should be one of
Speaker 1: those like really easy questions to answer fifth graders should
Speaker 1: know this or something, but I'm having trouble explaining it.
Speaker 1: It is a force like but needed to create force.
Speaker 1: I mean, I think of going down to like the
Speaker 1: atomic level. Energy is like the movement of electrons. Intuitively,
Speaker 1: when I think of energy, I think about vibrating particles
Speaker 1: and the fast of their vibrating more energy they have.
Speaker 1: But I guess at a more fundamental level energy is
Speaker 1: about probably fields and like how much energy is in
Speaker 1: a certain field, dictating what kind of particle is and
Speaker 1: what that particle is doing. I think energy is just
Speaker 1: like tiny movement of particles that gets passed along from
Speaker 1: particle to particle. Energy is the opposite side of the
Speaker 1: coin is mass. But my us as you're referring to
Speaker 1: the fundamental building blocks of energy, and I'm not sure
Speaker 1: what those could be. All Right, interesting answers um pretty
Speaker 1: deep ones to a lot of people are like, it's
Speaker 1: a vibe, man, it's a mood. Yeah, And some people
Speaker 1: giving examples of what energy is and some people talking
Speaker 1: about the different forms of it. It's the really interesting
Speaker 1: answers here. Thanks everyone. Yeah, and some people even sort
Speaker 1: of went with the official definition, which is that it's
Speaker 1: related to your ability to do work or to make
Speaker 1: work or change work. But did did you follow up
Speaker 1: with them? Then? What does work mean? No? I don't
Speaker 1: actually have live conversations with these folks. It's just the email.
Speaker 1: When I do interviews on campus, then I can ask
Speaker 1: fun follow up questions like does that scare you? Are
Speaker 1: you worried about that? But here I just give them
Speaker 1: the one shot I see, I see, I see. You're
Speaker 1: trying to still fear in them. No, I try to
Speaker 1: be friendly and not instill fear in them over email
Speaker 1: in person. Yeah, absolutely, I'll put them on the spot.
Speaker 1: All right, Well, it's a tricky subject, and I think
Speaker 1: I will find out it's something that has some deep
Speaker 1: mysteries about it, right, It's not an easy answer answer.
Speaker 1: All right, Well, Daniel step us through. What are some
Speaker 1: of the first things that physicists think of when they
Speaker 1: think of energy? So right off the bat, we should
Speaker 1: just admit that we don't fundamentally know what energy is. Wait,
Speaker 1: what we're done with the podcast? Nobody knows that's it.
Speaker 1: You know some things about it, We figured some things out.
Speaker 1: You can use those to piece together a picture of
Speaker 1: what it might be and what that means, But fundamentally
Speaker 1: it remains a philosophical mystery what energy is. First, maybe
Speaker 1: I should put the question back on you and ask, like,
Speaker 1: what kind of answer do people expect? Like what kind
Speaker 1: of answer would be satisfying? Where is the sort of
Speaker 1: nature of the question we're even asking? Do you want
Speaker 1: to know if energy is like a thing that flows
Speaker 1: or if it's made out of little energy ons? Or
Speaker 1: just like a concise definition of what this thing is. Well,
Speaker 1: I mean you sort of give it away. He kind
Speaker 1: of spoiled the answer for me here and seem to
Speaker 1: not want to try. I mean, if you guys don't
Speaker 1: know what it is, what I know. But it's kind
Speaker 1: of an interesting question. I think, you know, at the
Speaker 1: base of it, I think most people think of energy
Speaker 1: is like the opposite of of not moving, you know
Speaker 1: what I mean, Like it's the opposite of standing still
Speaker 1: and not doing anything. Like if you have energy, then
Speaker 1: you're doing something, You're doing work, I guess, yeah. And
Speaker 1: I think that a lot of the concepts about energy
Speaker 1: start from examples. I think some of the difficulty comes
Speaker 1: from the fact that you can put lots of different
Speaker 1: kinds of examples together and then wonder, like what do
Speaker 1: they all have in common? You know, the mass is
Speaker 1: energy or this is energy, Then what do they all
Speaker 1: have in common? And so maybe we should start with
Speaker 1: sort of like the history of the idea of the
Speaker 1: development of energy, how people discover different forms of energy
Speaker 1: and then talk about the common thread between them. Yeah, yeah, sure,
Speaker 1: well I was thinking kind of it's kind of like
Speaker 1: maybe the opposite of the phrase nothing happens. Like if
Speaker 1: nothing happens, ever, then there's no energy, but if things happen,
Speaker 1: then there's energy. It's like maybe related to the word happening,
Speaker 1: that's possibly true, but there are subtle wrinkles there, like
Speaker 1: you can have a universe with a lot of energy
Speaker 1: but no free energy, like the heat death of the universe.
Speaker 1: Nothing can really happen. But there is a lot of
Speaker 1: energy in the universe, there's just none available to do
Speaker 1: work because there's no energy gradients. So there are different
Speaker 1: kinds of energy, different kinds of energy. And fundamentally, the
Speaker 1: game we're playing here is that we're looking around in
Speaker 1: the universe and we're coming up with ways to do calculations,
Speaker 1: and we're wondering do those mean anything? And energy in
Speaker 1: that sense isn't like something physical. It's an observation we
Speaker 1: make about the universe. Like I can look at a
Speaker 1: physical system, you know, the Earth moving around the Sun,
Speaker 1: and I can do a calculation that could say, well,
Speaker 1: I'm going to define some quantity. I call it energy,
Speaker 1: And here's how I calculated. I take the velocity I'm
Speaker 1: multiplied by the mass. I add this, I add that
Speaker 1: that's the something I invented call it energy. And most
Speaker 1: of the time, if you just invent a quantity, it's
Speaker 1: not interesting or useful, doesn't reveal anything about the universe.
Speaker 1: But sometimes it does, and it was especially when it
Speaker 1: seems like it might be conserved when you've constructed this
Speaker 1: quantity which seems to like not change as time goes
Speaker 1: on through the universe. Mm hmmmm. Well, that's an interesting
Speaker 1: concept to think about. How they came up how humans
Speaker 1: came up with the word, right, Like, did we come
Speaker 1: up with that word for energy before science even you
Speaker 1: know what I mean? Like that? I wonder if Caveman
Speaker 1: had a phrase or a word for this idea of
Speaker 1: things happening or energy. I think Caveman had teenagers, and
Speaker 1: teenagers didn't get out of the cave very early in
Speaker 1: the morning, and people wondered if they needed more energy.
Speaker 1: I'm sure that you know the intuitive concept of feeling
Speaker 1: like you have energy or you're tired. That's an age
Speaker 1: old idea for sure. M So we probably had a
Speaker 1: word for it, and then people started to use it
Speaker 1: in physics. Yeah, and scientifically, one of the first concepts
Speaker 1: that was developed was kinetic energy. So you've got to
Speaker 1: go back to people like Leibnitz. It was Newton's contemporary
Speaker 1: and you know, also developed calculus, and like Newton, he
Speaker 1: also did a bit of physics, right, And the Leibnitz
Speaker 1: note us that things moved, that there's motion. And he
Speaker 1: came up with this quantity mass times velocity times velocity again,
Speaker 1: so MV squared, And he said, this thing seems to
Speaker 1: be conserved. He called this thing vis visa, like a
Speaker 1: living force, and so he essentially stumbled across the definition
Speaker 1: of kinetic energy and said, hey, here's a quantity which
Speaker 1: is interesting because it seems to be conserved. It seems
Speaker 1: like as time passes and you recalculate this quantity, it
Speaker 1: doesn't change, right. But I guess maybe a question is
Speaker 1: how did he noticed that it was conserved? Like why
Speaker 1: did he pick MV squared? As the quantity that was
Speaker 1: concerned was just something specific he was studying. He didn't
Speaker 1: know why. He was just sort of like playing around.
Speaker 1: You know, it's sort of like a discovery in mathematics,
Speaker 1: But what do you mean it playing around around with
Speaker 1: what you know? At that time, people didn't understand motion.
Speaker 1: Newton hadn't developed his laws yet, so people would just
Speaker 1: like multiplying random stuff together and seeing what it could do.
Speaker 1: You know, there's not that many ways to combine basic
Speaker 1: quantities mass and velocity in these things, and so it's
Speaker 1: not that hard to study them. You know, across the
Speaker 1: English channel, Newton was studying momentum, mass, time, velocity. So
Speaker 1: likeness has just multiplied it by velocity one more time.
Speaker 1: I'm sure he studied other quantities like mass squared times
Speaker 1: of loss that didn't have any interesting properties. You make
Speaker 1: it sound like a bunch of monkeys in a in
Speaker 1: an infinite room piping that typewriter. It's a bunch of
Speaker 1: grass students in an infinite room, and they all come
Speaker 1: with one quantity and they're like, oh, this one's not interesting.
Speaker 1: Oh look at this one. This one seems to be conserved.
Speaker 1: I wonder what that means, but I guess, I mean, like,
Speaker 1: what did he see it conserved in? Do you know
Speaker 1: what I mean? Like he calculated in for one thing
Speaker 1: and then for another, and then he saw that it
Speaker 1: was the same. I guess, But what was that thing? Yes, So,
Speaker 1: for example, physicists of this age like to do calculations
Speaker 1: about billiard balls. Right now, billiards is a very very
Speaker 1: old game. So you can take the kinetic energy of
Speaker 1: the first ball and then it hits another one, maybe
Speaker 1: it has a different mass, but you notice that the
Speaker 1: kinetic energy is conserved, and so you can do simple
Speaker 1: calculations there and see that kinetic energy is conserved in
Speaker 1: these systems, so like after a collision. Then they noticed
Speaker 1: that this quantity seems to stay the same, Like you
Speaker 1: added up at the beginning for the two balls, and
Speaker 1: then you added up at the end for the two balls,
Speaker 1: and it seemed to be the same. Is that what happened,
Speaker 1: because if you look at the velocities, the velocities don't
Speaker 1: stay the same. That's right. The velocities do not stay
Speaker 1: the same unless the two masses are the same. But
Speaker 1: like the really slow moving massive ball bumps into a
Speaker 1: very light ball, a low mass ball, that low mass
Speaker 1: ball will fly off at higher speeds, and so you're write,
Speaker 1: velocity isn't conserved. But this weird combination of mass and
Speaker 1: velocity squared did seem to be conserved. So that was
Speaker 1: sort of like an experimental discovery that lenn has made.
Speaker 1: And you know, this idea of conservation means it might
Speaker 1: be something important, It might be something like fundamental to
Speaker 1: the universe. It's like, there's the philosophy aspect to it. Right,
Speaker 1: just because something is conserved, why do we care? Because
Speaker 1: it reveals something about the inner workings of the universe.
Speaker 1: I think about this sometimes an analogy to other systems,
Speaker 1: like economics, or like the water system. You know, like
Speaker 1: water goes through lots of different forms. It rains into
Speaker 1: the ocean and evaporates back up in the clouds, that
Speaker 1: flows down rivers, but in the end, the water is
Speaker 1: the water. It's changing, it's transforming, but it's flowing through
Speaker 1: the system. The amount of water isn't changing. So that
Speaker 1: tells you that, like water is deeply important to this
Speaker 1: whole cycle. Right, if you identify a quantity which is
Speaker 1: conserved in physical processes, you get the sense that maybe
Speaker 1: it's important, right. I think what you're saying is that
Speaker 1: sometimes we notice that there are things that sort of
Speaker 1: don't disappear, like you're saying water. In the water cycle,
Speaker 1: water it changes shape and it changes forms and it
Speaker 1: changes states, but it's still sort of like you know,
Speaker 1: the water, the molecules don't disappear. And maybe in the
Speaker 1: case of the billiard balls that you notice that this quantity,
Speaker 1: like if you computed, it's there in the beginning, and
Speaker 1: it's there at the end, and somehow it got like transform.
Speaker 1: So maybe it's like a thing itself. Yeah, because it's
Speaker 1: easy to think of counter examples, like the number of bananas. Right,
Speaker 1: the number of bananas is not constant in the universe.
Speaker 1: You can make more bananas, you can eat bananas, right,
Speaker 1: They can disappear, they can be destroyed, they can be created. Right.
Speaker 1: The number of bananas is not fundamentally interesting to the verse,
Speaker 1: even if it might be personally interesting to various people.
Speaker 1: Well that you know, if right, Daniel, Like maybe they're
Speaker 1: I you haven't starved the whole universe. Maybe every time
Speaker 1: someone needs a banana here, bananas born in another planet
Speaker 1: somewhere in the universe. Right, you don't know exactly. And
Speaker 1: if you discovered that to be true, that would mean
Speaker 1: something deep about bananas and the relationship to the universe.
Speaker 1: That would be a huge discovery. That would be crazy,
Speaker 1: wouldn't it, Like somehow the universe likes to keep the
Speaker 1: same number of bananas all the time. That would be weird. Right,
Speaker 1: And if you eat a banana here or destroy it
Speaker 1: or make a bananas movie, another banana is born somewhere,
Speaker 1: that would be really strange. That would be very strange,
Speaker 1: and it would be a big clue. It would say
Speaker 1: the universe is kind of banana or bananas are fundamental
Speaker 1: to the universe. So when you discover a conserved quantity
Speaker 1: something the universe maintains, then you're seeing something about the
Speaker 1: inner workings of the universe. It's revealing to you what's important,
Speaker 1: just like how water is important in the water cycle,
Speaker 1: whereas clouds are not. So if kinetic energy is conserved,
Speaker 1: liveness thought, well, this must be an important thing, you know.
Speaker 1: I think if you tell anyone these days, like hey,
Speaker 1: energy is conserved or waters conserved, nobody would blink and
Speaker 1: I but if you tell them, like, hey, did you
Speaker 1: know the universe conserves bananas, that would be a big
Speaker 1: revelation about the universe, just like how we should look
Speaker 1: at energy and water as being kind of a big deal. Right. Yeah,
Speaker 1: And just in case anybody is being misled, as far
Speaker 1: as we know, the universe does not conserve bananas, as
Speaker 1: far as we know. Yes, as far as we know.
Speaker 1: For example, I'm pretty sure there were billions of years
Speaker 1: in which they were exactly zero bananas in the universe
Speaker 1: that you know of that I know of, Yes, But
Speaker 1: maybe all the bananas that are appearing on Earth mean
Speaker 1: that they're anti bananas being created on alien world somewhere
Speaker 1: else to balance that. Or I think you're saying what
Speaker 1: happened before the Earth with four maybe there were other
Speaker 1: planets with bananas. I'm just saying, keep an open mind.
Speaker 1: You're saying bananas could predate the Earth. Yeah, that's my
Speaker 1: theory of bananas. Well, I think your philosophy is bananas. Yeah.
Speaker 1: But anyways, I think obviously trying to make the point
Speaker 1: that you know, we should be sort of amaze and
Speaker 1: awed at the act that energy seems to be conserved
Speaker 1: in that water and for example, that water cycle is
Speaker 1: conserved because it doesn't have to write. I think that's
Speaker 1: what you're saying to You can come up with all
Speaker 1: sorts of quantities, you can define them, and most of
Speaker 1: them are not conserved. So when you find one that
Speaker 1: is that tells you you're onto something, it's a really
Speaker 1: interesting clue. All right, So then I guess that leapness
Speaker 1: called this energy. Did he coined the phrase or was
Speaker 1: he the first one to use it? On envy square.
Speaker 1: Did he call it kinetic energy? Also know, he called
Speaker 1: it vis visa, which is I think Latin for like
Speaker 1: a living force. And you know, now we know the
Speaker 1: kinetic energy on its own isn't actually conserved. I mean,
Speaker 1: under certain assumptions it is. In elastic collisions, we don't
Speaker 1: break things up, kinetic energy is conserved, but on its own,
Speaker 1: kinetic energy more generally isn't conservative. Course, And I think
Speaker 1: Newton was mostly looking at momentum, right, because that one
Speaker 1: is conserved in most collisions. Yeah, momentum is actually conserved.
Speaker 1: So Newton's combination of kinematic variables mass times velocity, momentum,
Speaker 1: this thing actually is conserved. But again, at the time,
Speaker 1: nobody knew why. It wasn't until we had a great
Speaker 1: mathematical genius a couple hundred years later who told us
Speaker 1: about the connections between conservation laws and symmetries, how these
Speaker 1: conservation laws revealed deep symmetries of the universe. Well, I
Speaker 1: mean that's what they thought, was that the fundamental law
Speaker 1: of the universe, right, the momentum is conserved. Yeah, the
Speaker 1: momentum conservation was discovered before we understood what it meant
Speaker 1: and why we have it. What symmetry of the universe created.
Speaker 1: We just did a whole podcast episode about why momentum
Speaker 1: is conserved. It's really fun and deep topic. Okay, so
Speaker 1: that's one kind of energy. What were some of the
Speaker 1: other kinds of energy we've discovered? So there is a
Speaker 1: second kind of energy, potential energy, which is a different
Speaker 1: kind of energy from kinetic energy and something I've never
Speaker 1: really been comfortable with. Wait, what potential energy makes you uncomfortable?
Speaker 1: You don't like the idea of potential I don't want
Speaker 1: any surprises. Just give me straight up energy. Yeah, potential
Speaker 1: energy is weird and confusing. It's definitely a different kind
Speaker 1: of energy than kinetic energy, but it's also closely related
Speaker 1: to kinetic energy because while kinetic energy by itself isn't conserved,
Speaker 1: some kinetic plus potential that is conserved in the universe. Mm. Interesting. Well, okay,
Speaker 1: let's get into the details of that, and I want
Speaker 1: to know why it makes you uncomfortable. But first, let's
Speaker 1: take a quick break. Wright. We're talking about energy, and
Speaker 1: it's been a very energetic discussion here. Daniel talked about
Speaker 1: how you know humans when we start to try to
Speaker 1: understand the world, we came up with the idea of
Speaker 1: energy because it seems to be conserved in some circumstances,
Speaker 1: and that was kinetic energy. But there's also potential energy,
Speaker 1: which is kind of a weird concept in physics, right,
Speaker 1: it makes you uncomfortable. Yeah, it is a weird concept
Speaker 1: in physics, but it's also something sort of intuitive. Like
Speaker 1: let's say you have a banana on the top of
Speaker 1: a bookshelf and it's just sitting there right not doing anything,
Speaker 1: and you bump it and it falls off before it
Speaker 1: hits the ground. It's going pretty fast, so it has
Speaker 1: kinetic energy. Where did that kinetic energy come from? Right?
Speaker 1: It came from its height. It came from the fact
Speaker 1: that it was sitting high up above the ground, and
Speaker 1: it turned that height in the gravitational field into energy.
Speaker 1: So that's the potential energy of the banana getting turned
Speaker 1: into kinetic energy of the banana. So it's definitely energy
Speaker 1: because you can transform it into kinetic energy into motion.
Speaker 1: But it's sort of weird because it's energy of its location.
Speaker 1: It's energy of its configuration, right right. I think that's
Speaker 1: where the name potential comes from. Like, it doesn't really
Speaker 1: have energy right now, it's just sitting on the table.
Speaker 1: It doesn't really it's not really moving, but it has
Speaker 1: a potential to move along. Yeah. I think that's tempting
Speaker 1: to describe it that way, but it really is energy.
Speaker 1: Potential energy is not just like the potential to have energy.
Speaker 1: It comes from energy of a potential. Potential is the
Speaker 1: way we describe how a field impacts a force on
Speaker 1: an object, Like an electron moving through a potential you know,
Speaker 1: feels a force, right. But I think you're getting mixed up,
Speaker 1: you know, kind of tripped up here because you're saying
Speaker 1: it's in a potential because it has the potential to move,
Speaker 1: to cause it to move, you know what I I mean.
Speaker 1: It's like a circular definition. Yeah, it has the potential
Speaker 1: to move exactly. So we don't really know what this
Speaker 1: stuff is. Potential energy. I always found it really strange.
Speaker 1: Mostly it makes me uncomfortable because it doesn't really have
Speaker 1: a value in itself. It's relational like the banana. How
Speaker 1: much potential energy does it have at the top of
Speaker 1: the bookshelf. We don't know. There's no number, but it
Speaker 1: has more potential energy than at the bottom of the bookshelf.
Speaker 1: Potential energy is only important in differences, and you can
Speaker 1: add an arbitrary number to the potential energy of the
Speaker 1: banana at the bookshelf. Doesn't matter. The only thing that
Speaker 1: matters is how much more potential energy it has the
Speaker 1: top in the bottom right. Like it's a relative quantity
Speaker 1: kind of like it depends on where you measure, and
Speaker 1: if you measure it from the floor, it's one thing.
Speaker 1: If you measure it from the table, it's zero. Yeah.
Speaker 1: It's sort of like velocity in that sense. It's no
Speaker 1: meaning to say you're moving at a certain speed. You're
Speaker 1: only moving at a certain speed relative to something else.
Speaker 1: The banana has pential energy relative to the floor. And
Speaker 1: something that's fascinating is that it's very easy to see
Speaker 1: kinetic energy and potential energy slashing back and forth into
Speaker 1: each other. If you have, for example, a ball, and
Speaker 1: you drop it, then it's potential energy is getting turned
Speaker 1: into kinetic energy, and then it gets turned around when
Speaker 1: it hits the floor, and it's kinetic energy then gets
Speaker 1: turned back into potential energy as it climbs back up
Speaker 1: to your hand. And if there wasn't friction or air resistance,
Speaker 1: then it would just go on forever, smoothly sliding back
Speaker 1: between the two different forms of energy, right, Like, if
Speaker 1: it was jumping on an infinite trampoline kind of like
Speaker 1: a perfect trampoline, this energy would, like the kinetic energy
Speaker 1: would appear and disappear, appear and disappear, and the pinetial
Speaker 1: energy would also appear and disappear, but it would always
Speaker 1: add up to the same thing. It would always added
Speaker 1: to the same thing. And a trampoline is a great
Speaker 1: example because it's basically like a spring. Springs have potential
Speaker 1: energy in them also, right, You squeeze a spring that
Speaker 1: takes energy, and now the energy you put into squeezing
Speaker 1: it is somehow stored in the spring, in the arrangement
Speaker 1: of the spring, the compactification of the as bonds that
Speaker 1: would prefer to be relaxed, And so that's the same
Speaker 1: kind of energy. You can put it into a gravitational field,
Speaker 1: you can put it into a spring, you can put
Speaker 1: it into a squeezing of a ball, which is basically
Speaker 1: another spring. And so all these things are potential energy, right,
Speaker 1: And in that sense, you can sort of think of
Speaker 1: it as a thing. Right, it's just the thing that
Speaker 1: changes from being kinetic to being potential, Like it's somehow
Speaker 1: there and it's always conserved. But is it a thing?
Speaker 1: When you say a thing, I think something physical, you know,
Speaker 1: like water is flowing. And for a long time people
Speaker 1: who are wondering, like is energy a thing to like
Speaker 1: flow from one thing to another? Is it made of
Speaker 1: little energy particles? But here because potential energy is a
Speaker 1: kind of energy, and it's just an arrangement of other things.
Speaker 1: And is it itself a thing or is it just
Speaker 1: the arrangement of other things. It's complicated, you mean, like
Speaker 1: does it have a physical embodiment or is it just
Speaker 1: I don't know, like a label we put on other things. Yeah,
Speaker 1: that's a deep question. I'm not sure the answer to
Speaker 1: the same question can be asked, like you know makes
Speaker 1: you you? You were made of the same particles as
Speaker 1: I am, you just arranged a different way. So the
Speaker 1: units is in the arrangement of the particles, the same way.
Speaker 1: Potential energy comes from configuration of particles together, not the
Speaker 1: particles themselves. The potential energy isn't stored in the particle,
Speaker 1: It's in the relationship between the particles, right right, unless
Speaker 1: you're a zombie, in which case your body is arrangement.
Speaker 1: Is the decay? Well, I guess, but what about mass?
Speaker 1: You know, like, we know that mass is the same
Speaker 1: as energy kind of in a way, right, according to
Speaker 1: equals empty squared is mass energy. Then I'm going to
Speaker 1: take probably surprising and weird philosophical position here, which is
Speaker 1: that mass is not its own kind of energy. Mass
Speaker 1: is just a representation of how much energy is stored
Speaker 1: inside something, how much kinetic and potential energy is in something.
Speaker 1: What do you mean like things don't have inherent mass,
Speaker 1: Like don't particle from the fundamental particles, don't they have
Speaker 1: you know, mass, Like the electron has mass? Right, yeah,
Speaker 1: so let's break it down, Like the electron fundamentally doesn't
Speaker 1: have mass on its own. Its mass comes from its
Speaker 1: interactions with the Higgs field. So that's the kinetic and
Speaker 1: potential energy of the Higgs field, which changes how the
Speaker 1: electron moves through the universe as if it did have mass.
Speaker 1: But if you listen to our episode on like what
Speaker 1: is renormalization, what is the electron's true mass and charge?
Speaker 1: Discover that fundamentally, truly, the electron and the other particles
Speaker 1: have no mass on their own, It's all in their energy, right,
Speaker 1: Because I guess even the electron it's it's not like
Speaker 1: that has a little bit of stuff in the middle.
Speaker 1: It just has the potential to interact with the Higgs field.
Speaker 1: And that's what we call its mass. That's what we
Speaker 1: call its mass. I act to truck because we're doing
Speaker 1: this podcast, but really because we wrote a chapter on
Speaker 1: it for our second book. Frequently asked questions about the universe. Yeah,
Speaker 1: and if you think about composite particles like a proton,
Speaker 1: and proton is made out of quarks, those corks have
Speaker 1: almost no mass, but the proton has a good bit
Speaker 1: of mass. Where does that come from? It comes from
Speaker 1: the energy that binds those corks together. So the protons
Speaker 1: mass some other weird kind of mass in the universe,
Speaker 1: not like you're converting kinetic energy into some sort of substance.
Speaker 1: It just comes from its internal stored energy. So the
Speaker 1: way I think about mass is sort of like an
Speaker 1: indicator tells you how much energy is internally stored inside
Speaker 1: this thing. In the end, it's all just energy. Mass
Speaker 1: isn't its own form of energy. It just reflects how
Speaker 1: much energy is inside something. You're basically saying, all masses
Speaker 1: just potential energy, potential and kinetic energy. Right, some of
Speaker 1: the protons. Mass comes from the kinetic energy of those
Speaker 1: gluons and quarks slashing around, So not just potential energy
Speaker 1: but also kinetic all right. So I think what you're
Speaker 1: saying is that we're trying to define energy. One way
Speaker 1: to do it is to look at its different kinds,
Speaker 1: and there are really toward fens that there's only two
Speaker 1: kinds of energy, kinetic energy and potential energy. There are
Speaker 1: no other other kinds, right, are there? I mean there's
Speaker 1: dark energy. Wow, way to secure us with our own
Speaker 1: terrible names. You totally right, But we don't know what
Speaker 1: dark energy is. One theory is that it's like the
Speaker 1: fundamental quantum potential energy of all of these fields, in
Speaker 1: which case it would be a kind of potential energy.
Speaker 1: But we really just don't know what dark energy is.
Speaker 1: It's a big mystery, all right. So ignore the scent
Speaker 1: of the universe that is dark energy for this discussion
Speaker 1: and let's just focus on the small bit of it
Speaker 1: that we like to talk about. No, it's a great point,
Speaker 1: but when we do figure out what dark energy is,
Speaker 1: either it will be kinetic energy or to be potential energy,
Speaker 1: or it'll be some new kind of bonkers energy. And
Speaker 1: I'll be wrong, in which case I'll be the first
Speaker 1: to celebrate. Well, yeah, basically, like I said, let's just
Speaker 1: ignore of the universe that is dark energy. And uh,
Speaker 1: you know, for our for what impacts is there's really
Speaker 1: only two kinds of energy. You're saying, kinetic energy and
Speaker 1: potential energy. And that's it, right, And that's kind of
Speaker 1: what goes into your basic equations of the universe, right, Like,
Speaker 1: that's basically the definition of the equations of the universe.
Speaker 1: That's right. The Shortinger equation has kinetic energy plus potential
Speaker 1: energy in it. Hamiltonian mechanics is built on that principle,
Speaker 1: you know, Classical mechanics is based on the principle of
Speaker 1: least action, and action in the end is defined in
Speaker 1: terms of these two quantities, kinetic and potential energy. And
Speaker 1: the deep mystery really is if these two things independently
Speaker 1: are not conserved potential and kinetic energy, but together they are,
Speaker 1: what does that mean about what they have in common?
Speaker 1: And what is that commonality? I think that in the
Speaker 1: end is the question what is energies? What do these
Speaker 1: two things together, what larger picture do they make up? Right?
Speaker 1: Because I think maybe that's something that maybe a lot
Speaker 1: of people don't know. Is that when you know, in physics,
Speaker 1: say oh, the laws of the universe or the equations
Speaker 1: that define the universe, Really what you're talking about is
Speaker 1: basically the idea that kinetic energy and potential energy is conserved,
Speaker 1: because that's what you assume when you formulate the laws
Speaker 1: of physics. Right, you start with, hey, let's assume that
Speaker 1: kinetic and potential energy is conserved, you know, and then
Speaker 1: let's see what kind of rules that gives us. I
Speaker 1: think it actually goes the opposite direction. You can make
Speaker 1: up laws to a universe that don't have conservation of energy.
Speaker 1: If those laws, for example, are changing in time, then
Speaker 1: they don't conserve energy. And one of the greatest insights
Speaker 1: into this relationship between conservation laws and symmetries came when
Speaker 1: people were asking about general relativity. They're like, hold on
Speaker 1: a second, does general relativity conserve energy? That seems like
Speaker 1: it should be important. So we actually derived the laws
Speaker 1: from other places and then ask like, hold on a second,
Speaker 1: is energy conserved? What does that mean about these things?
Speaker 1: I guess I mean, like, you know, like the Hamiltonian
Speaker 1: that's that's basically you're you saying Hey, the sum of
Speaker 1: kinetic and potential energy should always stay the same, and
Speaker 1: then from that you derive some of these other equations. Right, Well,
Speaker 1: there's very non satisfactory physics definition. The answer to that,
Speaker 1: which is that once you define the Hamiltonian, then energy
Speaker 1: is defined to be the thing that's conserved if these
Speaker 1: rules don't change in time. So you sort of start
Speaker 1: from the Hamiltonian and and you figure out what is
Speaker 1: the energy of the system from that, I guess what
Speaker 1: I'm saying is um that it's It's a very fundamental
Speaker 1: concept in in how theoretical physics works. Right. It's not
Speaker 1: like you assume, like, hey, let's assume it's changing. What
Speaker 1: does that give us? It's like you'd assume that it's
Speaker 1: not changing. Kind of. I think there are different ways
Speaker 1: to formulate the theories of the universe. And you can
Speaker 1: either start from the assumption that energy is conserved to
Speaker 1: figure out what rules are allowed, or you can just
Speaker 1: start building laws and figuring out what the consequences are,
Speaker 1: which ones actually describe our universe, and then noticing that
Speaker 1: in the ones that describe our universe, this quantity we
Speaker 1: call energy seems to be conserved. There's some different orders
Speaker 1: you could use there. All right, well, I guess for
Speaker 1: our discussion, the basic idea is that, you know, physicists
Speaker 1: sort of describe or define energy as the sum of
Speaker 1: kinetic energy plus potential energy. But what you're saying is
Speaker 1: that that's kind of a weird thing to do, because, like,
Speaker 1: how do you know kinetic energy and potation energy have
Speaker 1: to be related to each other exactly? They seem like
Speaker 1: very different things, right, What does it mean that these
Speaker 1: two very different things are closely related? Like if you discovered, well,
Speaker 1: the number of bananas in the universe isn't conserved, but
Speaker 1: bananas plus apples that's conserved. That would be really interesting
Speaker 1: connection between bananas and apples. You're like, it turns out
Speaker 1: to have more in common than I thought. Right, then
Speaker 1: they have a kids song together, apples and bananas. I
Speaker 1: think we need to hear a snippet of it. Go ahead,
Speaker 1: all right, can you play it for us? Um, I
Speaker 1: don't have my kazoo here otherwise I would. Well, I
Speaker 1: think I think what you're saying is that it's kind
Speaker 1: of weird to put them together. But if you put
Speaker 1: it together, then it seems to be constant in the universe.
Speaker 1: And it seems to give us these equations that seem
Speaker 1: to work and seems to like predict where particles are
Speaker 1: going to go and what's going to happen to them,
Speaker 1: and what kinds there are even exactly. And what that
Speaker 1: means is that they really do have something in common.
Speaker 1: They're part of the same thing. They're not the same thing.
Speaker 1: They're like two halves of a puzzle that clicked together
Speaker 1: perfectly to make something new. And then we have to
Speaker 1: ask the question, what does that mean where they have
Speaker 1: in common? What is this larger thing that they're a
Speaker 1: part of? All right? So then are they conserved? Because
Speaker 1: I know sometimes they're not conserved. So they are conserved
Speaker 1: in the case where the laws of physics do not change.
Speaker 1: So the laws of physics you're using are the same
Speaker 1: now and the same in ten minutes and the same
Speaker 1: in a thousand years, then kinetic energy plus potential energy
Speaker 1: is conserved. That's absolutely true. Now in our universe, the
Speaker 1: laws of physics are almost the same from moment to moment.
Speaker 1: They're usually the same. You can do the experiment the
Speaker 1: Large Hadron Collider today and tomorrow and next year and
Speaker 1: get the same measurements. But there is one way in
Speaker 1: which those laws are changing, which is that space itself
Speaker 1: is expanding. As you mentioned, dark energy is accelerating the
Speaker 1: expansion of the universe, making it bigger and bigger and
Speaker 1: changing the distances between things, and that technically is a
Speaker 1: change in the laws of physics as a function of time,
Speaker 1: meaning that energy is not technically conserved. It's not really
Speaker 1: relevant for balls rolling down planes, or banana is falling
Speaker 1: off of bookshelves, or any experiment we are going to do.
Speaker 1: But you want the deepest understanding of energy. That turns
Speaker 1: out in our universe it's not technically conserved but almost
Speaker 1: right right. Well, I've feel like you're maybe cheating a
Speaker 1: little bit here. I feel like you're saying that we
Speaker 1: have these laws that we think described the universe, and
Speaker 1: in them energy is conserved unless our laws are wrong,
Speaker 1: in which case they doesn't. Does that Does that make sense?
Speaker 1: I feel I feel like maybe what's really happening is
Speaker 1: that we don't have the right laws of the universe,
Speaker 1: Like we only have laws that seemed to work for
Speaker 1: you know, moment to moment, or that doesn't take into
Speaker 1: account to six seven of the universe. That's that's making
Speaker 1: it expand really we just kind of maybe don't have
Speaker 1: the right laws. It might also be that the laws
Speaker 1: really are a function of time, right, that the way
Speaker 1: things work changes as the universe goes on. That's just
Speaker 1: the way the universe is. Wait, what you mean like
Speaker 1: it's a function of something, But it's not a function
Speaker 1: of anything. It could be a function of time, right,
Speaker 1: But based on what law, the laws themselves could just
Speaker 1: be a function of time, you know why. For example,
Speaker 1: are constants constant? If the gravitational constant changed as a
Speaker 1: function of time, then you can get free energy. If
Speaker 1: gravity disappeared every Tuesday morning for an hour, then I could,
Speaker 1: with no energy, take a big box of bananas and
Speaker 1: put it on a bookshelf, and then when gravity came back,
Speaker 1: I could knock it off and extract the energy from it.
Speaker 1: So I'd have an infinite energy machine. If the gravitational
Speaker 1: constant wasn't constant. So if these constants are changing, then
Speaker 1: energy is not concerned, right, right, But it isn't that
Speaker 1: I mean that idea what you're saying, like, hey, let's
Speaker 1: just give up and start asking questions. Isn't that sort
Speaker 1: of a lot of what you talk against about, right? Like,
Speaker 1: you know, if you discovered that the laws of the
Speaker 1: universe are changing for some unknown reason, wouldn't you want
Speaker 1: to know what that reason was? Oh? Absolutely yes, And
Speaker 1: doesn't mean you can't find an explanation. Right. The laws
Speaker 1: can be changing, and those laws can be changing for
Speaker 1: a good reason. It could be like only one consistent
Speaker 1: way for the universe to be, and it requires these
Speaker 1: constants to change. Right, It's still following some system which
Speaker 1: is governing how those constants change. But the constants themselves,
Speaker 1: the ones that describe the motion of things and how
Speaker 1: you get equations of motion, if those are changing, then
Speaker 1: this quantity we call energy is not conserved right, Right,
Speaker 1: But I guess I'm saying, if there's a system that
Speaker 1: is determining how the laws of the universe are changing,
Speaker 1: then maybe that system is the real true you know,
Speaker 1: a set of equations that that governed the universe. Sure, absolutely,
Speaker 1: and they could be like the true system that governs
Speaker 1: these laws. But the ones that determine how things move, right,
Speaker 1: that determine motion of things through the universe. If those
Speaker 1: laws are a function of time because they're controlled by
Speaker 1: some super deep metal laws. Right, If those laws that
Speaker 1: determine how things move through the universe. If those are changing,
Speaker 1: then energy is not conserved. Well, I think we're getting
Speaker 1: a little bit lost because we're talking about energy. I
Speaker 1: think what you're saying is that energy is conserved if
Speaker 1: you look at it locally, like our little you know,
Speaker 1: what we've seen of the universe and what laws we've
Speaker 1: coupled together. But if you look at the big, big picture,
Speaker 1: energy is not conserved, which kind of makes you wonder,
Speaker 1: like what it is right exactly, or throws into question
Speaker 1: even more our ideas of it and points of the
Speaker 1: fact that we don't really know what it is because
Speaker 1: it's not even conservad like we thought it was exactly,
Speaker 1: And it also questions like how important is it? One
Speaker 1: of the reasons we thought it was important because it's
Speaker 1: because we thought it was conserved and we thought it
Speaker 1: was a deep truth in the universe. It revealed something fundamental.
Speaker 1: If it's not actually conserved, you mean, it's maybe not
Speaker 1: as important as we thought, right right, It points like
Speaker 1: maybe it's just the pawn in the meadow law of
Speaker 1: the universe that we have no idea about so far exactly.
Speaker 1: It's just like a lowly fruit, like a cherry instead
Speaker 1: of the regal banana instead of the legal banana, exactly,
Speaker 1: the all important banana. Yes, all right, well let's get
Speaker 1: into a little bit more about what we don't know
Speaker 1: about the definition of energy and what it could all mean. Man,
Speaker 1: But first let's take another quick break. All right, welcome
Speaker 1: back to Daniel and Jorge argue about energy when one
Speaker 1: of us is a physicist and the other one is
Speaker 1: not clearly, but I guess I'm getting the picture that,
Speaker 1: you know, we kind of thought we knew what energy was.
Speaker 1: We thought it was this fundamental thing that always seems
Speaker 1: to be conserved. But it turns out that it's not
Speaker 1: always conserved. So now maybe it's not only do we
Speaker 1: not know what it is, but maybe it's not even fundamental. Yeah,
Speaker 1: that's right, And it's sort of disappointing because even a
Speaker 1: small amount of non conservation means it's just not conserved.
Speaker 1: You know, there's like two things, things are conserved and
Speaker 1: things that are not. There's a whole bunch of categories
Speaker 1: of things that are not conserved, and being almost conserved
Speaker 1: means I guess you're important, but not really truly fundamental.
Speaker 1: All right, Well, then what would you say energy is then?
Speaker 1: I would say, I wish I knew, and it's something
Speaker 1: definitely deep and interesting in the universe, right, It's something
Speaker 1: that is almost conserved, and it can slash back and
Speaker 1: forth between these two different kind of things that feel very,
Speaker 1: very different. What is energy? The philosophical question really is
Speaker 1: what do kinetic and potential energy have in common? What
Speaker 1: are they part of when you put them together in
Speaker 1: the same way that like you can put electricity and
Speaker 1: magnetism together into a holistic thing and get an understanding
Speaker 1: of electromagnetism, You're like, oh, that explains this and that
Speaker 1: and brings all these ideas together. You have a feeling
Speaker 1: of having an answer. If we understood how kinetic energy
Speaker 1: and potential energy you fit together into one holistic thing,
Speaker 1: we'll be able to grapple better with this question. I
Speaker 1: feel like you're saying, like, maybe even the word energy
Speaker 1: is a little distracting from the real question, which is
Speaker 1: like why is there a relationship between you know, motion
Speaker 1: and potential in a way, or even like why does
Speaker 1: potential exists at all? Exactly? And you can try to
Speaker 1: tease it apart by looking at the equations of motion
Speaker 1: and thing like what is it that defines how things
Speaker 1: move and why can this weird quantity slash back and forth.
Speaker 1: And one way to get a little bit of insight
Speaker 1: into it is to understand that potential really is also
Speaker 1: about motion, Like potential energy is what causes forces. Right,
Speaker 1: the reason that the banana falls off the book shelf
Speaker 1: and accelerates towards the floor is because there's a gravitational
Speaker 1: force there. There's a force there because there's a difference
Speaker 1: in the potential. So you can think about in terms
Speaker 1: of kinetic energy and potential energy. You can also think
Speaker 1: about it in terms of like motion and forces. Like
Speaker 1: a particle just flying through the universe, it just has
Speaker 1: kinetic energy. Now add other particles interacting with it, putting
Speaker 1: forces on it. Those are creating potential energy for that particle.
Speaker 1: In some sense, it's not kinetic energy and potential energy.
Speaker 1: It's kinetic energy and other forces changing its kinetic energy.
Speaker 1: I think what you're saying is that maybe there's really
Speaker 1: only motion and potential motion, Like there's only motion in
Speaker 1: the universe, and then there's what happens when two things
Speaker 1: that have motion kind of bump into each other somehow,
Speaker 1: for some reason, they interact in a way that creates potential,
Speaker 1: but really you're just talking about motion and what happens
Speaker 1: in that interaction exactly. And this is the philosophical process
Speaker 1: of sort of stumbling towards a deeper concept or trying
Speaker 1: to understand what these things have in common and generalize
Speaker 1: it into an idea that really fits together that can
Speaker 1: hold as a bucket all these different concepts that we
Speaker 1: consider energy and its properties. And it's connected to this
Speaker 1: other question we talked about, like our fields. Real well,
Speaker 1: it sort of sounds like you're saying that maybe there's
Speaker 1: only really kinetic energy, right, Like, there's only kinetic energy,
Speaker 1: and there's also what happens when two things that have
Speaker 1: kinetic energy interact with each other, right, Like, it sounds
Speaker 1: like maybe potential energy is really just about motion and interactions,
Speaker 1: and so you've got to ask, like, why does the
Speaker 1: universe have motion and why does it have interactions? Like
Speaker 1: right right, if it didn't have interactions, everyone would just
Speaker 1: fly around by themselves. They would just be kinetic energy
Speaker 1: and that would never change. But it changes because we
Speaker 1: have these interactions in the universe. And that goes to
Speaker 1: like an even more abstract question, which is like why
Speaker 1: do you consider things is interacting. That assumes that there's
Speaker 1: different things that you can say, like there's this one
Speaker 1: thing and the other thing, Well, how do you draw
Speaker 1: the line between them? Right, it's like one half of
Speaker 1: the earth interacting with the other half of the earth.
Speaker 1: How do you slice that? Why do you call the
Speaker 1: earth one thing and not two things? And anytime your
Speaker 1: ideas are based on totally arbitrary designations like that, like
Speaker 1: this is a thing, but that's not a thing, or
Speaker 1: this is two things, then you know that you're looking
Speaker 1: at it the wrong way. I think the work that's
Speaker 1: left to be done is to understand this as one
Speaker 1: holistic thing. You know, what is it really that's flowing
Speaker 1: between two objects where one is in motion and then
Speaker 1: another one is in motion. How is that flowing? Is
Speaker 1: it really changing into a different kind of energy? Or
Speaker 1: is there one holistic, super kind of idea there that
Speaker 1: you can understand connects these two things right? Right, Like
Speaker 1: maybe there aren't humans and zombies. Maybe maybe we're all
Speaker 1: just human and zombies just have the potential to eat humans. Exactly.
Speaker 1: Maybe before you eat the banana, the banana is already
Speaker 1: kind of party, you you know, or hey, plus banana
Speaker 1: is already the thing before you eat the banana. I
Speaker 1: think what you're saying is that, you know, we talk
Speaker 1: about kinnetic energy and potential energy, but really maybe there's
Speaker 1: just part of the same thing, like motion plus interactions. Right.
Speaker 1: If I zoom in on a particle on like a proton,
Speaker 1: and say, oh, look, those quirks have kinnectic energy inside
Speaker 1: of them. But if I zoom out and just look
Speaker 1: at the proton, I'm like, oh no, the proton is
Speaker 1: at rest. It has no kinetic energy. So how much
Speaker 1: kinetic energy there is depends on what I'm defining to
Speaker 1: be a thing or not. It seems sort of arbitrary,
Speaker 1: and I think that's the biggest clue that will lead
Speaker 1: us to a deeper understanding of energy, but I don't
Speaker 1: have that understanding today. Well, let's touch a little bit
Speaker 1: into that the scenario that you mentioned earlier in the episode,
Speaker 1: which is the end of the universe, and that maybe
Speaker 1: one potential end of the universe is the heat death
Speaker 1: of the universe, where you know, everything has energy, but
Speaker 1: nothing can happen everything. You know, particles are moving like
Speaker 1: a giant gas, and so there's definitely energy there, but
Speaker 1: no potential energy is that what you're saying that there's
Speaker 1: it's an scenario where there's no potential energy left in
Speaker 1: the universe. Yeah, there's useful energy, and then there's sort
Speaker 1: of useless energy. Useful energy is energy you can use
Speaker 1: to do work, to like move something up a potential
Speaker 1: for example. And you know if you have energy in
Speaker 1: a battery, you can take that energy and use it
Speaker 1: to power and engine and it can like push your
Speaker 1: banana up off the floor back to the top of
Speaker 1: the bookshelf. That's useful energy, and that only happens when
Speaker 1: you have energy localized somewhere, right, when you have low entropy,
Speaker 1: when there's organization of stuff. Opposite of that is useless energy.
Speaker 1: Energy like heat. If everything is just hot and everything
Speaker 1: is the same temperature, there's no temperature difference, there's no
Speaker 1: energy gredients. You can't use that to power and engine.
Speaker 1: Like if you have an engine and you're in a
Speaker 1: universe where everything is smooth but hot, there's no way
Speaker 1: to take that energy in those motions of the particles
Speaker 1: and turn that into something useful. So the key idea
Speaker 1: there's entropy. Entropy, right, Yeah, there's like everything is that
Speaker 1: a hot mess? What you're saying a bland, hot mess.
Speaker 1: But wouldn't I guess even invest in an area, wouldn't
Speaker 1: gravity eventually kind of bring stuff together, creating potential energy?
Speaker 1: Or like, how does gravity disappear in this scenario? And
Speaker 1: gravity doesn't disappear, but it can't do anything in that
Speaker 1: scenario because everything is smooth and homogeneous. Gravity requires some
Speaker 1: clump to get things started. Like in the early universe,
Speaker 1: we didn't have a smooth and homogeneous blob of stuff
Speaker 1: in the very beginning. We had little quantum fluctuations, little
Speaker 1: bits of over density and under density that gravity grabbed
Speaker 1: onto and exaggerated. But if you have the true heat
Speaker 1: death of the universe, where everything is spread out equally,
Speaker 1: then every particle feels the same gravitational pull in every direction,
Speaker 1: so it basically cancels out. What is this idea of entropy?
Speaker 1: How does that impact our definition of energy? Like maybe
Speaker 1: it's not real or something. Well, folks who love and
Speaker 1: understand them, dynamics have different definitions of energy. There's energy
Speaker 1: in general, and then there's free energy, which is sort
Speaker 1: of like an energy available to do useful work. And
Speaker 1: then there's also discount of energy and energy on sale.
Speaker 1: And then there's free lunch, which apparently doesn't even exist
Speaker 1: that we know of. But you, as you said, the
Speaker 1: universe is changing, Daniel. Maybe it will be free lunch
Speaker 1: in the future for everyone. That's right, And these topics
Speaker 1: always make me uncomfortable. Thermodynamics is the topic of physics
Speaker 1: that I avoided as much as possible when I was
Speaker 1: taking class. Is right? That and zombie movies? Or maybe
Speaker 1: they're about the same thing, right, Zombies are about decay
Speaker 1: and things breaking down. Maybe maybe this is all turned
Speaker 1: out to be a deep psychological journey into daniel psyche.
Speaker 1: That's right, but we're understanding the conservation of Daniel's decisions.
Speaker 1: Zombies and entropy make you uncomfortable. Maybe we should dig
Speaker 1: deeper into that day and did something happen in your childhood? Yes,
Speaker 1: a zombie came an intropute in my bedroom when I
Speaker 1: was a kid that I'm scared. No. Thermodynamics to me
Speaker 1: is complicated because you're just so many particles. It's all
Speaker 1: about statistical statements of large systems of particles. For me,
Speaker 1: it's easier to grapple with one particle bouncing off another particle,
Speaker 1: because I would like to get down to the microscopic
Speaker 1: picture what's really happening, and there amo dynamics is about
Speaker 1: like zooming out and trying to make like broad statements
Speaker 1: about systems. It's not the same as philosophy though, Yeah,
Speaker 1: but philosophy nobody has any wrong answers. That's right, it's
Speaker 1: not verifiable, how convenient. Well, I think the overall picture
Speaker 1: I'm getting is that to answer the question what is energy,
Speaker 1: it's it's tough. You know, we have different labels for it.
Speaker 1: There's kinetic energy, that it's potential energy. That seems to
Speaker 1: be all about there is to it, but that's not
Speaker 1: the full picture. Like it seems to be conserved, but
Speaker 1: it's not really conserved in the universe, and so maybe
Speaker 1: it's not even an important thing, or maybe it's not
Speaker 1: even a thing. Like maybe in the future aliens will
Speaker 1: be like, why do you guys were thinking about energy?
Speaker 1: That's like thinking about the ether or thinking about you know,
Speaker 1: the soul or something like. That's that's a that's the
Speaker 1: thing that doesn't make sense. Yeah, it definitely is driven
Speaker 1: from an intuitive experience of the world, and then try
Speaker 1: to extrapolate that to physics and understand if it makes
Speaker 1: sense and it's sort of kind of seems like it does,
Speaker 1: but maybe it doesn't quite. We definitely still have work
Speaker 1: to do. And you know, if you look into a
Speaker 1: physics book or google this question, you might find some
Speaker 1: confusing answers. Some of them are things like energy is
Speaker 1: the quantity that's conserved if the laws of physics don't change,
Speaker 1: So they're like defining it to be the conserved thing,
Speaker 1: which doesn't really tell you like what it is. It
Speaker 1: just tells you how Nuther's theorem impacts these laws of physics.
Speaker 1: Doesn't really tell you like what it is. I think
Speaker 1: we're still struggling to figure out exactly what energy is, right,
Speaker 1: it might need to be redefined now that we sort
Speaker 1: of know and this is the only reason that we
Speaker 1: know that the universe is changing and the laws of
Speaker 1: physics are not constant. Ye, so the history of this
Speaker 1: scene over a few hundred years is like discovery of
Speaker 1: kinetic energy that seems to be conserved. Oops, no, it's
Speaker 1: not only kinetic energy plus potential energy is conserved. And
Speaker 1: then Einstein's general relativity as a whole new system for
Speaker 1: the universe and not there says hold on a second,
Speaker 1: that doesn't guarantee conservation of energy, so people like, oops,
Speaker 1: better patch that up, make sure conserve energy, and then
Speaker 1: we discover actually, it doesn't conserve energy. The universe disagrees
Speaker 1: with that whole idea. So it's been a lot of
Speaker 1: back and forth. Yeah, I'm amazing you guys still have
Speaker 1: the energy to keep at it. Well, somebody keeps eating bananas,
Speaker 1: and so we keep asking questions. Right, maybe we've been
Speaker 1: as our concerned. Well, it seems like maybe we won't
Speaker 1: define it any time soon. But I think it sort
Speaker 1: of points to the idea that there are these deep
Speaker 1: relationships in the universe between motion and and potential and fields,
Speaker 1: and we're still trying to figure out what those relationships
Speaker 1: are because that kind of tells that's what's going to
Speaker 1: tell us what the true nature of the universe is. Yeah,
Speaker 1: and one of the deepest goals in physics is to
Speaker 1: come up with a concise, mathematical story about how the
Speaker 1: universe works in a way that makes sense to us.
Speaker 1: And that's what we're struggling with here, is connecting these
Speaker 1: mathematical concepts with intuitive ideas that gel with us, that
Speaker 1: tell us something about the nature of the universe more
Speaker 1: than just looking at the black and white equations on
Speaker 1: a page. And that's what it's all about, jelling with
Speaker 1: the universe and eat a banana and Jill and chill
Speaker 1: out exactly, But don't eat the last banana because it's
Speaker 1: a fixed number of them in the universe. And if
Speaker 1: you eat the last one or he can't, and then
Speaker 1: we won't have any more partner. Know, it's an ever
Speaker 1: green quantity, right, that's what I thought. That's what we concluded. No,
Speaker 1: I see, eat all the bananas you want, ran because
Speaker 1: somewhere or some unknown process is recreating them. That's a
Speaker 1: nice universe to live in. Yeah, pretty bananas. All right. Well,
Speaker 1: we hope you enjoyed that discussion. Thanks for joining us,
Speaker 1: see you next time. Thanks for listening, and remember that
Speaker 1: Daniel and Jorge explained. The universe is a production of
Speaker 1: I Heart Radio. For more podcast for my heart Radio,
Speaker 1: visit the I heart Radio app, Apple Podcasts, or wherever
Speaker 1: you listen to your favorite shows. Yeah,