Latest / Daniel and Kelly’s Extraordinary Universe / The most common listener questions!

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The most common listener questions! · Daniel and Kelly’s Extraordinary Universe

• 0:08
  Speaker 1: Hey, Daniel, how's our email inbox looking these days? Is happening?
• 0:12
  Speaker 1: There are so many fun questions, and there's so many
• 0:15
  Speaker 1: people wondering about the mysteries of the universe. Well, do
• 0:18
  Speaker 1: you know if any patterns or trends or maybe frequently
• 0:22
  Speaker 1: asked questions? Oh for sure. Actually most of the questions
• 0:25
  Speaker 1: we get, our questions we have seen before. Yeah. Really
• 0:28
  Speaker 1: a lot of people have the same questions. Yeah, just
• 0:31
  Speaker 1: the same concepts tend to trip up a lot of people.
• 0:34
  Speaker 1: So if you still don't understand quantum mechanics or relativity,
• 0:39
  Speaker 1: you're not the only one. No, In fact, you're in
• 0:41
  Speaker 1: very good company because I'm still confused about it. May
• 0:44
  Speaker 1: you should submit it as a question to our podcast.
• 0:46
  Speaker 1: And who's going to answer it? Not me? I am
• 1:06
  Speaker 1: more handmade cartoonists and the creator of PhD Comics. Hi,
• 1:09
  Speaker 1: I'm Daniel. I'm a particle physicist and I've never stopped
• 1:12
  Speaker 1: asking questions about the universe. And welcome to our podcast,
• 1:16
  Speaker 1: Daniel and Jorge Explain the Universe, a production of I
• 1:19
  Speaker 1: Heart Radio in which we dive deep into your questions
• 1:22
  Speaker 1: about the universe and two scientists questions about the universe
• 1:25
  Speaker 1: into everybody's questions about the universe. How does it work?
• 1:29
  Speaker 1: What is it made of? Why does it work this
• 1:31
  Speaker 1: way and not that way? Why don't I have a
• 1:33
  Speaker 1: taco stand around my corner? Every deep and important question
• 1:37
  Speaker 1: about the universe handled on one podcast. Have you actually
• 1:40
  Speaker 1: checked all four corners? I do a scan every day
• 1:43
  Speaker 1: for taco chucks, and there's still not one on my corner.
• 1:47
  Speaker 1: You live in southern California and you have trouble finding
• 1:49
  Speaker 1: a taco truck. You need to get out more man. Yes,
• 1:52
  Speaker 1: that's definitely my problem. Yeah, we all have questions, and
• 1:56
  Speaker 1: it seems to be kind of a innate part of
• 1:58
  Speaker 1: human nature to be cure us about what's going on
• 2:01
  Speaker 1: around them and how things work. And fortunately the universe
• 2:05
  Speaker 1: is happy to provide mysteries and strange things for us
• 2:09
  Speaker 1: to ask questions about. Yeah, we're lucky that the universe
• 2:11
  Speaker 1: is both amazing, beautiful and mysterious. Yet it also seems
• 2:16
  Speaker 1: to be discoverable that we have this incredible technique for
• 2:19
  Speaker 1: divining knowledge from the universe by asking questions and then
• 2:23
  Speaker 1: answering them in a structured way. So we're fortunate to
• 2:26
  Speaker 1: be surrounded by amazing but accessible mystery yeah, especially you,
• 2:30
  Speaker 1: I guess, because you know the universe was simple and
• 2:33
  Speaker 1: easy to understand, we might be out of a job, Daniel,
• 2:35
  Speaker 1: that's right, especially if the whole field of physics lasted
• 2:38
  Speaker 1: like ten minutes of human history. They're like, let's knock
• 2:41
  Speaker 1: that off before lunch. We we've done it, we've done it.
• 2:45
  Speaker 1: Fire all the physicists put them to work somewhere else
• 2:48
  Speaker 1: doing Mataga trunk. You're right, there is a sort of
• 2:51
  Speaker 1: exquisite balance there. Physics was too easy, it'd be done
• 2:54
  Speaker 1: too soon. If it was too hard, nobody would give
• 2:56
  Speaker 1: us any money because we weren't making any progress. So
• 2:58
  Speaker 1: it's got to be just part of to be worth doing.
• 3:01
  Speaker 1: And so physicists, as part of their jobs, ask questions
• 3:04
  Speaker 1: about the universe, and they all have. They have all
• 3:06
  Speaker 1: kinds of amazing questions about how things work. And the
• 3:09
  Speaker 1: public also has a lot of questions. And sometimes those
• 3:11
  Speaker 1: questions are one and the same. That's right, and we
• 3:13
  Speaker 1: on this podcast do our best to answer those questions,
• 3:17
  Speaker 1: to dig deep, to explain them to you in a
• 3:18
  Speaker 1: way that makes sense. But sometimes our explanations inspire more questions.
• 3:23
  Speaker 1: We'll talk about a topic like black holes and then
• 3:25
  Speaker 1: we'll get five or ten very similar questions about some
• 3:28
  Speaker 1: little wrinkle that we didn't cover or something we said
• 3:31
  Speaker 1: that didn't quite make sense to a few people, and
• 3:33
  Speaker 1: so we thought it'd be fun to dig into some
• 3:35
  Speaker 1: of those emails and answer those questions and iron out
• 3:38
  Speaker 1: those wrinkles. So today on the podcast, we'll be tackling
• 3:46
  Speaker 1: our most common listener questions. That's right. We have a
• 3:50
  Speaker 1: series of episodes on this podcast where we talk about
• 3:53
  Speaker 1: the most unusual and interesting listener questions, the ones that
• 3:55
  Speaker 1: are sort of tricky and hard and require me to
• 3:58
  Speaker 1: do a bunch of research. But there's a whole other
• 4:00
  Speaker 1: category of questions that we want to share with you,
• 4:03
  Speaker 1: and these are the common questions, the one that a
• 4:05
  Speaker 1: lot of people are asking. And so today will be
• 4:08
  Speaker 1: asking most of a lot of the top questions that
• 4:10
  Speaker 1: we get through email, through Twitter, through Instagram. Daniel, do
• 4:14
  Speaker 1: you check Instagram? Do you know what Instagram is? Do
• 4:17
  Speaker 1: we have a TikTok account too? I don't use grams
• 4:20
  Speaker 1: because you know, I'm an American, and so I use
• 4:23
  Speaker 1: instat pounds good. That sounds like a bad diet to
• 4:26
  Speaker 1: go on. I don't recommend it. Actually, that's the name
• 4:30
  Speaker 1: of my taco truck is instat pounds, so we put
• 4:33
  Speaker 1: sour cream on everything. Maybe it's good that you don't
• 4:36
  Speaker 1: have a taco truck. Then maybe that's why I don't
• 4:39
  Speaker 1: have a talk. Yeah. So we're gonna be asking all
• 4:42
  Speaker 1: these questions, and they're all great questions, and they have
• 4:44
  Speaker 1: to do with the dark matter and black holes and
• 4:47
  Speaker 1: particles and all kinds of things, even philosophical questions and
• 4:51
  Speaker 1: questions about life and how to get involved in physics.
• 4:54
  Speaker 1: So we'll dive right in. Our first question comes from
• 4:57
  Speaker 1: Thomas and he us a question about is there a
• 5:01
  Speaker 1: dark matter inside of black holes? And what about neutrinos? Now,
• 5:05
  Speaker 1: because he asking if there's a dark matter inside of
• 5:07
  Speaker 1: neutrinos or is he asking the neutrinos inside of black hole?
• 5:10
  Speaker 1: I think he's asking if he can get a side
• 5:12
  Speaker 1: of neutrinos with his tacos. Everyone has a side of
• 5:16
  Speaker 1: neutrinos and the tacos, don't they. Yeah. I think that
• 5:18
  Speaker 1: this question is basically asking, like what kind of stuff
• 5:21
  Speaker 1: gets sucked into a black hole? Dark matter, which we
• 5:24
  Speaker 1: know is out there, this invisible kind of matter giving
• 5:28
  Speaker 1: gravity to the universe, even though we can't see it,
• 5:31
  Speaker 1: does that also get sucked into black holes? And that's
• 5:34
  Speaker 1: I think also why he's asking about neutrinos, Like neutrinos
• 5:37
  Speaker 1: feel hardly anything and have almost no mask, Did they
• 5:40
  Speaker 1: also get sucked into black holes? So I think that's
• 5:42
  Speaker 1: the origin of the questions. Are black holes sort of
• 5:45
  Speaker 1: universal sucker ruppers or do they only eat regular matter
• 5:49
  Speaker 1: like the kind that we're made out of. Yeah, And
• 5:51
  Speaker 1: the other angle of this question is, you know, what
• 5:53
  Speaker 1: are the structures of dark matter? If dark matter is
• 5:55
  Speaker 1: here in the universe, is it just big fluffy clouds,
• 5:58
  Speaker 1: or is it making like dark plant? It's dark stars,
• 6:00
  Speaker 1: dark black holes, and dark podcasts a right, So is
• 6:04
  Speaker 1: there dark matter inside a black holes? Daniel almost certainly. Yes.
• 6:08
  Speaker 1: Black holes are basically just very strong sources of gravity,
• 6:11
  Speaker 1: and they can suck in anything anything that has mass.
• 6:14
  Speaker 1: It doesn't matter if you are moving very fast or
• 6:17
  Speaker 1: if you're moving very slow, if you're low mass or
• 6:20
  Speaker 1: high mass. All forms of energy are trapped by black holes,
• 6:24
  Speaker 1: even if they have no other kinds of interactions. Right.
• 6:27
  Speaker 1: That's the thing that makes dark matter unique is that
• 6:29
  Speaker 1: we think it has no other kinds of interactions that
• 6:32
  Speaker 1: we're aware of. But you can still get sucked into
• 6:34
  Speaker 1: a black hole, right, Yeah, I guess the question is
• 6:37
  Speaker 1: it can only interact with gravity. I think we have
• 6:40
  Speaker 1: a podcast that covers that what would keep it inside
• 6:42
  Speaker 1: of the black hole. Couldn't it escape if it wasn't
• 6:45
  Speaker 1: being crunched down by other stuff. It's not being crunched
• 6:48
  Speaker 1: down by the other stuff, but it's gravity that's holding
• 6:51
  Speaker 1: things inside a black hole. Remember, these days, we don't
• 6:53
  Speaker 1: think about gravity as a force, so you shouldn't think
• 6:56
  Speaker 1: about it like tugging on this stuff and keeping it
• 6:58
  Speaker 1: in the black hole. We think of gravity as the
• 7:01
  Speaker 1: bending of the shape of space. Einstein told us that
• 7:05
  Speaker 1: this is some crazy relationship where matter bends space and
• 7:08
  Speaker 1: then space tells matter how to move because of its curvature.
• 7:11
  Speaker 1: And a black hole is this crazy intense bending of
• 7:15
  Speaker 1: space such that essentially becomes one directional inside a black hole,
• 7:19
  Speaker 1: you can only move towards the center. Space is one
• 7:22
  Speaker 1: directional inside a black hole, sort of the way time
• 7:25
  Speaker 1: is one directional outside a black hole. Time only moves
• 7:28
  Speaker 1: forward outside a black hole. Space only moves towards the
• 7:31
  Speaker 1: center inside a black hole. So it doesn't really matter
• 7:34
  Speaker 1: what you are if you have any mass or energy.
• 7:36
  Speaker 1: You are moving towards the center of the black hole
• 7:38
  Speaker 1: once you fall in, right, But then once it gets
• 7:40
  Speaker 1: to the center, wouldn't it come out the other end
• 7:43
  Speaker 1: Once it gets to the center, gravity is going to
• 7:45
  Speaker 1: keep holding it at the center, right, I mean, unless
• 7:47
  Speaker 1: there's like a wormhole at the center attached to a
• 7:49
  Speaker 1: white hole or something crazy. But if you follow general relativity,
• 7:54
  Speaker 1: and you know, we think general relativity is correct, although
• 7:56
  Speaker 1: we don't think it works inside a black hole. But
• 7:58
  Speaker 1: if you're assuming the general relativity inside a black hole,
• 8:01
  Speaker 1: then once you fall in, you're moving towards a singularity,
• 8:04
  Speaker 1: even if you're dark matter. Interesting. I guess if that's
• 8:06
  Speaker 1: the case, then wouldn't we expect most black holes to
• 8:09
  Speaker 1: be mostly dark matter? Since there's five times more dark
• 8:13
  Speaker 1: matter in the universe and regular matter. It's a great question.
• 8:16
  Speaker 1: We don't know what fraction of the stuff inside a
• 8:19
  Speaker 1: black hole came from dark matter. But remember that dark
• 8:22
  Speaker 1: matter is much more diffuse, it's much more spread out
• 8:25
  Speaker 1: through the universe. It doesn't clump as much as normal
• 8:28
  Speaker 1: matter because it doesn't have those other kinds of interactions
• 8:31
  Speaker 1: like dark matter. These big swirling clouds of stuff that's
• 8:34
  Speaker 1: surround our galaxy. But it's harder for dark matter to
• 8:37
  Speaker 1: make dense structures because to make dense structures you need
• 8:40
  Speaker 1: other kinds of interactions. You need other kind of interactions
• 8:43
  Speaker 1: to hold stuff together, like the electromagnetic forces a thing
• 8:46
  Speaker 1: that's holding you together, not gravity, and you need those
• 8:50
  Speaker 1: interactions to sort of radiate away energy and fall in.
• 8:54
  Speaker 1: Like the reason something doesn't just orbit a black hole
• 8:56
  Speaker 1: forever is that it loses some of its energy and
• 8:59
  Speaker 1: falls in. To do that, you have to be able
• 9:01
  Speaker 1: to like radiate off a photon or a z or something,
• 9:04
  Speaker 1: and dark matter just can't do that. So dark matter
• 9:07
  Speaker 1: is much more spread out. So we don't think that
• 9:09
  Speaker 1: dark matter is sort of the primary seed for black holes.
• 9:13
  Speaker 1: But some of it must have eventually fallen in, but
• 9:16
  Speaker 1: maybe not as much as you might think, because it's
• 9:18
  Speaker 1: it's kind of hard for it to fall in. Yeah, precisely.
• 9:20
  Speaker 1: And if you take, for example, the volume of our
• 9:23
  Speaker 1: solar system, the volume of our solar system is mostly
• 9:26
  Speaker 1: filled with normal matter. There's a lot of dark matter
• 9:29
  Speaker 1: in there, and there's more dark matter in the universe,
• 9:31
  Speaker 1: but in the vicinity of our Solar system, it's mostly
• 9:34
  Speaker 1: normal matter. So if our star went black hole, it
• 9:37
  Speaker 1: would suck in some of the dark matter that's nearby,
• 9:40
  Speaker 1: But most of the matter in our solar system is
• 9:42
  Speaker 1: normal matter. And what about neutrinos? Can neutrinos fall into
• 9:46
  Speaker 1: a black hole? I guess anything. I think what you're
• 9:48
  Speaker 1: saying is that black hole has been space and time,
• 9:51
  Speaker 1: so it's more like a space trap rather than just
• 9:54
  Speaker 1: a gravity trap. Yeah, exactly, it's a space trap. It
• 9:56
  Speaker 1: space is gravity. Gravity is space, and so you're exactly right,
• 9:59
  Speaker 1: And anything can fall into a black hole and nothing
• 10:02
  Speaker 1: can escape. So the answer to your question, can X
• 10:05
  Speaker 1: fall into a black hole? Is always yes? Or any X?
• 10:09
  Speaker 1: Can the letter X daniel as a concept of fall
• 10:11
  Speaker 1: inside of a black hole? Oh? Man, can philosophical ideas
• 10:15
  Speaker 1: fall into a black hole? Well? There is this crazy
• 10:19
  Speaker 1: theory that information has mass, and you know that's never
• 10:22
  Speaker 1: really been proven, but so perhaps, yeah, you come up
• 10:25
  Speaker 1: with a crazenough idea that your head becomes a black hole,
• 10:27
  Speaker 1: and you were thinking about the letter X, then yeah,
• 10:30
  Speaker 1: Well I believe we renamed black holes to space traps.
• 10:34
  Speaker 1: I feel like that's more accurate and more descriptive. All right,
• 10:37
  Speaker 1: well we'll start using that on the podcast from now
• 10:39
  Speaker 1: on and we'll see if it catches on your space trap.
• 10:45
  Speaker 1: All right, well, I think that answers the questions forms contraras.
• 10:49
  Speaker 1: Thank you for asking the question. Our next question is
• 10:51
  Speaker 1: about the universe small topic and whether it's stretching and expanding.
• 10:57
  Speaker 1: So Steve slopeck as, if the universe is stretching and expanding,
• 11:01
  Speaker 1: what's it expanding into? Now you said, this is another
• 11:05
  Speaker 1: common question we get. This is a question we get
• 11:07
  Speaker 1: like once a week. People are hearing about how the
• 11:10
  Speaker 1: universe is getting bigger, and they're wondering, like, if the
• 11:13
  Speaker 1: universe is everything, how can it be getting bigger. Doesn't
• 11:16
  Speaker 1: that mean it's sitting inside something else that's holding it
• 11:19
  Speaker 1: that it's now like filling up. I think people are imagining, like,
• 11:22
  Speaker 1: you know, a blob of molecules inside an empty room
• 11:26
  Speaker 1: spreading out to sort of fill out all those corners.
• 11:28
  Speaker 1: I have that question, and it's an amazing question. But
• 11:32
  Speaker 1: the answer is no, that the universe is not expanding
• 11:35
  Speaker 1: into anything, because the expansion is not like relative to
• 11:39
  Speaker 1: some outside external space or metric right, The expansion is intrinsic.
• 11:45
  Speaker 1: It means that distances between points are getting larger. So
• 11:49
  Speaker 1: we don't have our space, you know, our three dimensional
• 11:52
  Speaker 1: space sitting inside some other box. It's just stretching, it's
• 11:56
  Speaker 1: creating new space between existing points. Well, I feel like
• 11:59
  Speaker 1: what you're saying is that there's nothing outside of space.
• 12:02
  Speaker 1: But isn't nothing something? There isn't anything outside of space,
• 12:06
  Speaker 1: so I avoid saying the word nothing. What do you
• 12:08
  Speaker 1: mean What makes you uncomfortable about the word nothing? Well,
• 12:11
  Speaker 1: it depends what you mean by space. I mean the
• 12:13
  Speaker 1: origin of space was sort of like the backdrop on
• 12:17
  Speaker 1: which things happen, you know, you like define distances and
• 12:21
  Speaker 1: you could have empty space and then stuff in it.
• 12:24
  Speaker 1: Sort of the origin of the concept of space originally.
• 12:27
  Speaker 1: But now we know that space is not like that.
• 12:29
  Speaker 1: Space is dynamic. It's flexible. It can shimmer and wiggle
• 12:32
  Speaker 1: and stretch and grow and bend. Right, But you're tempted
• 12:37
  Speaker 1: to put it in some now static, larger space. Right,
• 12:40
  Speaker 1: there's nothing on which this like goo of space actually sits.
• 12:44
  Speaker 1: But we don't have any evidence that that exists. We
• 12:46
  Speaker 1: don't know that there's some other external, true deep meta
• 12:50
  Speaker 1: space in which our space exists. It seems like all
• 12:54
  Speaker 1: the math is consistent with just our space bending relative
• 12:58
  Speaker 1: to itself. But I guess the question is if we
• 13:01
  Speaker 1: can expand I think maybe what trips people up is like,
• 13:05
  Speaker 1: what are we expanding into? If we're expanding into something,
• 13:09
  Speaker 1: then you must be able to measure it, And so
• 13:12
  Speaker 1: wouldn't it be like empty space kind of right that
• 13:15
  Speaker 1: you can measure. I think the confusion there is expansion, right.
• 13:18
  Speaker 1: We're not expanding into anything, We're expanding relative to ourselves.
• 13:22
  Speaker 1: So if you have two points in space and you wait,
• 13:26
  Speaker 1: you will notice, thanks to dark energy and the expansion
• 13:28
  Speaker 1: of the universe, that they are getting further and further apart.
• 13:31
  Speaker 1: So you can that's how you measure it. You don't
• 13:33
  Speaker 1: step outside of the universe and be like, hey, the
• 13:36
  Speaker 1: universe is fourteen inches wide and last year was thirteen
• 13:39
  Speaker 1: Look how much it's grown. You measure the points between
• 13:42
  Speaker 1: things in space because that's all you can do. You
• 13:44
  Speaker 1: can't step outside of space. It doesn't even really mean anything.
• 13:48
  Speaker 1: Maybe the way to think about it is that the
• 13:50
  Speaker 1: space is not growing. It's almost like it's stayed the
• 13:53
  Speaker 1: same size, but we're shrinking inside of it. You know. Actually,
• 13:57
  Speaker 1: Dan Hooper, who we've had on the program, a cosmologist,
• 13:59
  Speaker 1: likes to make that point that you can't actually tell
• 14:01
  Speaker 1: the difference between the expansion of space and the shrinking
• 14:05
  Speaker 1: of stuff that looks exactly the same. There you go.
• 14:10
  Speaker 1: So maybe that will help people from reading confused, because
• 14:13
  Speaker 1: you know, sort of just think about it more like
• 14:15
  Speaker 1: we're the same, space is the same, but we're shrinking.
• 14:18
  Speaker 1: I mean that invites lots of other questions, like if
• 14:20
  Speaker 1: I eat so many tacos, how could I possibly be
• 14:22
  Speaker 1: shrinking because the tacas are shrinking. Yeah, that's a that's
• 14:26
  Speaker 1: another way to think about it. And you know, remember
• 14:27
  Speaker 1: that we don't understand why the universe is expanding. It's
• 14:31
  Speaker 1: not something that we understand and can make sense of.
• 14:34
  Speaker 1: We don't know why it's happening, why it started happening
• 14:36
  Speaker 1: five billion years ago, whether it will continue to happen.
• 14:40
  Speaker 1: All we have are these observations that distances between things
• 14:43
  Speaker 1: in space are expanding and expanding at an accelerating rate.
• 14:47
  Speaker 1: So it's something we observe, and you have to just
• 14:49
  Speaker 1: go back to the root experiment, like what is it
• 14:51
  Speaker 1: we actually see, rather than you're trying to get tangled
• 14:54
  Speaker 1: up in the various theories of cosmological constants. It's almost
• 14:58
  Speaker 1: like the opposite of what happens when you grow up.
• 15:00
  Speaker 1: Like I feel like when you're a kid, distances seemed huge,
• 15:03
  Speaker 1: like sitting in the car for an hour, it takes forever.
• 15:07
  Speaker 1: But when you grow up and you're an adult, distance
• 15:10
  Speaker 1: this kind of shrink no way, right, like sitting in
• 15:13
  Speaker 1: an hour for I think that tour doesn't seem long
• 15:16
  Speaker 1: enough actually, and so it's kind of the opposite of that.
• 15:19
  Speaker 1: It's almost like relationship that matter has to space is changing.
• 15:22
  Speaker 1: And that's what this does mean by its expansion of
• 15:25
  Speaker 1: the universe. You're staying in the universe is just growing
• 15:27
  Speaker 1: up an eventual it's gonna have a midlife crisis, not
• 15:30
  Speaker 1: going down. It's pulling Benjamin button. Do you think for
• 15:34
  Speaker 1: the universe, like now a billion years just like flits
• 15:37
  Speaker 1: by in a moment, whereas when it was a kid
• 15:39
  Speaker 1: it took forever. Yeah, kind of in a way, right, yeah, yeah,
• 15:43
  Speaker 1: maybe that that explains time dilation. Man, Man relativity is
• 15:47
  Speaker 1: just about getting mature. I'll take the Nobel price right now,
• 15:51
  Speaker 1: I'll buy you a taco Alright. We have a lot
• 15:55
  Speaker 1: more of these most common questions that we get through
• 15:57
  Speaker 1: the inbox, but first let's take a quick break. All right.
• 16:14
  Speaker 1: I know we're answering our most common questions that we
• 16:18
  Speaker 1: get through the inbox and through Twitter, and we've answered
• 16:24
  Speaker 1: questions about black holes and the universe expanding, and we
• 16:27
  Speaker 1: also have questions about particles, which is kind of your
• 16:30
  Speaker 1: field of expertise particles and tacos. Don't forget, I'm quite
• 16:35
  Speaker 1: an expert talca particle, tacas or taco particles. Let's talk
• 16:40
  Speaker 1: about it. Is that what a takito is? That's right,
• 16:45
  Speaker 1: that's when your tacos exchanged particles with your friends takings. Well,
• 16:49
  Speaker 1: that's not that's a no no these days, but that's right.
• 16:52
  Speaker 1: Stay safe out there people, all right. So our next
• 16:54
  Speaker 1: question is asking about the charge of particles. For example,
• 16:59
  Speaker 1: me Brown asked, I was wondering how particles could be
• 17:02
  Speaker 1: charged and what that even means? Exclamation point question mark.
• 17:06
  Speaker 1: Oh man, I love this question because I have this
• 17:09
  Speaker 1: same question and we still don't really know what particle
• 17:13
  Speaker 1: charge is. It's very confusing. Yeah, I like how she asked,
• 17:15
  Speaker 1: what does that even mean? It's wonderful because you know,
• 17:20
  Speaker 1: it's something where that's very familiar. People think about charge
• 17:23
  Speaker 1: and electric charge and familiar with lightning and whatever. But
• 17:25
  Speaker 1: down at the particle level, like what does it mean
• 17:28
  Speaker 1: for a particle to have electric charge? Like is it
• 17:31
  Speaker 1: carrying something? Is they're charge like stuffed into it somewhere.
• 17:34
  Speaker 1: Why does some of them have it some of them don't.
• 17:36
  Speaker 1: It's a great deep question, Yeah, because I guess she's
• 17:39
  Speaker 1: really wondering, like because it seems arbitrary, like a particle
• 17:42
  Speaker 1: has charged or it doesn't have charge, or it has
• 17:44
  Speaker 1: positive charge, or it has a color charge. You know
• 17:47
  Speaker 1: what determines that and why do they have it? And
• 17:51
  Speaker 1: the answer is that we don't know, and we have
• 17:53
  Speaker 1: to just sort of root ourselves and what we have seen.
• 17:55
  Speaker 1: Remember that all of these ideas about particle physics and
• 17:58
  Speaker 1: the universe they come out of experiments that we've done,
• 18:02
  Speaker 1: things we've seen, and that we're trying to describe about
• 18:04
  Speaker 1: the universe. We don't always understand what's going on, and
• 18:07
  Speaker 1: we're just sort of trying to build a structure that
• 18:10
  Speaker 1: let's it all hang together. And for particle charge, the
• 18:13
  Speaker 1: root thing that we see is that some little bits
• 18:15
  Speaker 1: of matter, some particles, are affected by electric fields and
• 18:19
  Speaker 1: magnetic fields. Like you put electrons through an electric field,
• 18:23
  Speaker 1: they will get accelerated. You put other particles, you know,
• 18:26
  Speaker 1: particles that don't have electric charge through an electric field,
• 18:28
  Speaker 1: they don't get accelerated. That's what it means to have
• 18:31
  Speaker 1: electric charge. That's the root thing. We've seen that some
• 18:34
  Speaker 1: particles are pulled by electric fields and some particles are not.
• 18:38
  Speaker 1: That's really what a charge means. So you're saying it's
• 18:40
  Speaker 1: part of a philosophical answer, like they have charged because
• 18:43
  Speaker 1: we've seen them. I have charged, or at least Daniel
• 18:45
  Speaker 1: has seen them. They have charged. Yeah, Well, we see
• 18:48
  Speaker 1: that some particles are affected by electric fields, and so
• 18:50
  Speaker 1: we say, all right, let's say that those particles are different,
• 18:53
  Speaker 1: and we'll create this idea of charge, and we'll use
• 18:56
  Speaker 1: that as a description to say which particles are affected
• 18:59
  Speaker 1: by elect fields and which ones are not. And then
• 19:01
  Speaker 1: we'll look for patterns, and we'll look for trends, and
• 19:04
  Speaker 1: we'll look for symmetries, and we'll try to understand that
• 19:07
  Speaker 1: more deeply. But fundamentally, it's just really a label for
• 19:11
  Speaker 1: the things we've observed. Now, I wonder if what she's
• 19:14
  Speaker 1: trying to get at is whether charge is a property
• 19:18
  Speaker 1: of particles or the field that make up the particles,
• 19:22
  Speaker 1: You know what I mean, Like Is it something that
• 19:24
  Speaker 1: gets a sign when the particle pops up, or is
• 19:27
  Speaker 1: it something that's just like a property of the field
• 19:29
  Speaker 1: that they're part of. Yeah, that's a great question. Mathematically,
• 19:33
  Speaker 1: we sort of put it in the middle, like we
• 19:36
  Speaker 1: think of particles, you know, as fields. Mathematically we think
• 19:39
  Speaker 1: of it's sort of in the middle, like we write
• 19:42
  Speaker 1: these things into our theories. And we said that the
• 19:45
  Speaker 1: charge is the thing that connects the field with the particle.
• 19:49
  Speaker 1: So for example, the photon field only interacts with things
• 19:53
  Speaker 1: that have electric charge, and so it's really right there
• 19:56
  Speaker 1: in between is how the two talk to each other.
• 19:58
  Speaker 1: It's the thing that lets them talk to each other,
• 20:00
  Speaker 1: the field and the particle. So it's sort of a
• 20:03
  Speaker 1: property of their interaction. Oh, I see, it's kind of
• 20:06
  Speaker 1: maybe a property of both, kind of what you're saying, Yeah, exactly.
• 20:11
  Speaker 1: And you know, we have noticed some amazing interesting things
• 20:14
  Speaker 1: about charge, like charge is conserved. You know, you can't
• 20:18
  Speaker 1: create it or destroy it. No matter how many particles
• 20:21
  Speaker 1: you create or destroy, the total charge is unchanged. And
• 20:25
  Speaker 1: that tells us that it must be something interesting and
• 20:27
  Speaker 1: fundamental to the universe, sort of like energy. We think
• 20:30
  Speaker 1: energy isn't changed in these interactions, and so that tells
• 20:34
  Speaker 1: us it might be something deep, that it's connected somehow
• 20:37
  Speaker 1: to something really deep about the universe and particles and fields.
• 20:40
  Speaker 1: But the truth is we don't exactly know what. Like
• 20:43
  Speaker 1: it could be a thing itself, you know what I mean,
• 20:44
  Speaker 1: Like it's like something that's being conserved. So it's kind
• 20:46
  Speaker 1: of like something that can be quantified in a way.
• 20:49
  Speaker 1: It can definitely can be quantified, yeah, absolutely, And you know,
• 20:52
  Speaker 1: there are other kinds of charge also, right, as you
• 20:55
  Speaker 1: mentioned earlier, Like the strong force has its own equivalent
• 20:59
  Speaker 1: of charge. We call it color to be confusing and
• 21:02
  Speaker 1: attempting to be poetic, and it has a lot of
• 21:05
  Speaker 1: similar properties to electric charge, and that some particles have it,
• 21:08
  Speaker 1: some particles don't. And there's one for the weak force.
• 21:11
  Speaker 1: Some particles have it, some particles don't. Whi's one of
• 21:14
  Speaker 1: the deep mysteries of physics is of why some particles
• 21:17
  Speaker 1: have some of these charges and don't have other charges.
• 21:19
  Speaker 1: It's very confusing, and what we're trying to do is
• 21:22
  Speaker 1: make a unified vision understand how this all shook out
• 21:25
  Speaker 1: and why it's this way and not the other way.
• 21:27
  Speaker 1: But the truth is, we just really don't know, it
• 21:29
  Speaker 1: sounds like it's almost like that the language of the
• 21:31
  Speaker 1: universe is this charge, you know. Yeah, like some particles
• 21:35
  Speaker 1: speak like romannitism, so some don't, and that's how they
• 21:38
  Speaker 1: interact with the fields around them and other particles. Yeah,
• 21:40
  Speaker 1: but why right, Why do some particles feel this and
• 21:43
  Speaker 1: others don't? How did that happen? And what does that
• 21:45
  Speaker 1: even mean? What does that even mean? Question mark? Exclamation point.
• 21:49
  Speaker 1: That's like the reason I got into physics because I
• 21:50
  Speaker 1: love asking that question what does that even mean? You know,
• 21:53
  Speaker 1: we want to gather together these weird experiments we've seen
• 21:57
  Speaker 1: and get some sort of deep understanding, appeal back a
• 21:59
  Speaker 1: layer of reality, and reveal the way the universe like
• 22:02
  Speaker 1: actually works. Man, you guys used exclamation points and question
• 22:06
  Speaker 1: marks at the same time in your physics papers, only
• 22:09
  Speaker 1: in the best ones. All right, thanks for that question.
• 22:13
  Speaker 1: Our next question is another common question that we get,
• 22:16
  Speaker 1: and this one in particular came from Roger Grenna, and
• 22:20
  Speaker 1: the question goes, how do particles which I understand, how
• 22:22
  Speaker 1: zero volume make up matter? So that stuff has volume.
• 22:26
  Speaker 1: That's a great question. If particles have no volume, how
• 22:30
  Speaker 1: can we have volume? If the recipe for making of
• 22:32
  Speaker 1: you is a bunch of particles and that each have
• 22:34
  Speaker 1: zero volume, then why isn't your volume just the sum
• 22:37
  Speaker 1: of a bunch of zeros which is zero? Right? Right? Yeah?
• 22:40
  Speaker 1: Or I guess maybe is my volume kind of an illusion?
• 22:44
  Speaker 1: Kind of like if if you drill down and there's
• 22:46
  Speaker 1: no real volume to any of my particles, does that
• 22:49
  Speaker 1: mean that I am also devoid of volume? I'll avoid
• 22:55
  Speaker 1: a lot of bad jokes there. But if I eat
• 22:58
  Speaker 1: a taco, Daniel, how does that effect my volume? Where
• 23:03
  Speaker 1: does that taco actually go? Well? And there's lots of
• 23:06
  Speaker 1: ways to attack this problem, and the most philosophicals to ask,
• 23:09
  Speaker 1: like what do you mean by volume? And we had
• 23:11
  Speaker 1: a whole podcast episode about like how small are particles?
• 23:15
  Speaker 1: What do we mean by their size? Etcetera, etcetera. But
• 23:17
  Speaker 1: that's a whole rabbit hole. Let's put that aside and
• 23:19
  Speaker 1: say particles are points. Let's assume for now the particles
• 23:23
  Speaker 1: actually have zero volume. Right, it's a good point. Yeah,
• 23:27
  Speaker 1: So to try to get to the point here, the
• 23:29
  Speaker 1: idea is that you can build something with non zero
• 23:32
  Speaker 1: volume out of particles that have zero volume if you
• 23:36
  Speaker 1: have a way to space them. There's something keeping them
• 23:38
  Speaker 1: from overlapping from crunching on top of each other, and
• 23:42
  Speaker 1: you do, and they have forces. They have electric forces,
• 23:45
  Speaker 1: for example, And so the reason that, like when you
• 23:48
  Speaker 1: build a molecule, the atoms don't just lie on top
• 23:50
  Speaker 1: of each other is that there are electrons circling those
• 23:54
  Speaker 1: atoms that keep the nuclei apart, and the nuclei are
• 23:57
  Speaker 1: positively charged and they keep each other apart. So there
• 24:00
  Speaker 1: are forces there that creates sort of like a spacing,
• 24:02
  Speaker 1: like a lattice that keeps everything from collapsing into the
• 24:06
  Speaker 1: tiniest dunk. I guess that, yeah, you're ready. It does
• 24:08
  Speaker 1: depend on what you mean by volume, because if by
• 24:11
  Speaker 1: volume mean like when something is there and it's not there,
• 24:15
  Speaker 1: then particles almost have zero volume. But they're also kind
• 24:19
  Speaker 1: of infinite volume, right because you can feel a particle
• 24:22
  Speaker 1: all the way across the galaxy. Technically, yeah, yeah, technically,
• 24:25
  Speaker 1: And so you could also say that if you're made
• 24:28
  Speaker 1: of zero volume particles, even if they have spacing between them,
• 24:31
  Speaker 1: then your real volume is still just the sum of
• 24:34
  Speaker 1: all those zeros, even though they're distributed into sort of
• 24:36
  Speaker 1: a cloud. And you guy, it's like, well, where do
• 24:39
  Speaker 1: you stop if you're made of a bunch of particles
• 24:41
  Speaker 1: that are spaced apart, where do you stop. Do you
• 24:43
  Speaker 1: stop at the edge of the most like right most particle,
• 24:46
  Speaker 1: or where it pushes back, as you were saying, like
• 24:49
  Speaker 1: where it feels something and and where it pushes back.
• 24:52
  Speaker 1: Is also not very satisfying because then it depends on
• 24:55
  Speaker 1: what you're pushing with or against, yeah, or against. If
• 24:58
  Speaker 1: you push against dark matter, matter will pass right through
• 25:01
  Speaker 1: you like you're not there. If you push against neutrinos,
• 25:04
  Speaker 1: it will very lightly touch you. If you push against
• 25:07
  Speaker 1: you know, a regular object like a stick, then you're
• 25:09
  Speaker 1: pushing against the electromagnetic forces. So it depends on the
• 25:12
  Speaker 1: kind of thing you're probing with. So it's not really
• 25:15
  Speaker 1: very well defined. But if you just say, like, hey,
• 25:18
  Speaker 1: you can make a cloud out of non zero particles
• 25:21
  Speaker 1: that keep their spacing because of the forces between them,
• 25:24
  Speaker 1: then you get a pretty good sense for why you
• 25:27
  Speaker 1: aren't just a tiny dot. Yeah, I guess maybe, like
• 25:30
  Speaker 1: if you go by effect and technically we all have
• 25:33
  Speaker 1: infinite volume, like you know, if someone across the universe
• 25:36
  Speaker 1: feels me in a way and feels the forces that
• 25:38
  Speaker 1: like particles exert. But if you talk, if you call volume,
• 25:43
  Speaker 1: like where are the particles center that make up rhead?
• 25:47
  Speaker 1: Then because I have more than one, then you can
• 25:50
  Speaker 1: sort of define a range of space like a volume
• 25:53
  Speaker 1: of space, and that's maybe that's volume. Yeah, and so
• 25:56
  Speaker 1: it's a slippery topic volume, you know. Microscopically, it does
• 26:00
  Speaker 1: really have a great analog to the way we think
• 26:02
  Speaker 1: about it, like intuitively and macroscopically. And this is something
• 26:05
  Speaker 1: we struggle with all the time when we take our
• 26:08
  Speaker 1: common knowledge about how things work mass, volume, velocity, you know, time,
• 26:13
  Speaker 1: and we try to apply them to the microscopic where
• 26:15
  Speaker 1: the rules are really just totally different, and sometimes the
• 26:18
  Speaker 1: very ideas break down and don't really have a great analog.
• 26:22
  Speaker 1: All right, mind bending question. All right. Our next question
• 26:25
  Speaker 1: from our most common question pile is a bit of
• 26:28
  Speaker 1: a career question, and I'm curious that's why you get
• 26:32
  Speaker 1: this a lot. So the question goes, I've always loved
• 26:35
  Speaker 1: physics but studied something else. Is it too late for
• 26:38
  Speaker 1: me to learn physics for real? I'd like to for real.
• 26:42
  Speaker 1: At the end, we do get this question a lot,
• 26:45
  Speaker 1: and I think that that's because our podcast has attractive
• 26:48
  Speaker 1: folks who are really interested in questions of the universe.
• 26:51
  Speaker 1: And have a passion for understanding these things, but because
• 26:54
  Speaker 1: of whatever happened to them in life, didn't end up
• 26:56
  Speaker 1: studying physics. They studied computers or ended up in something
• 26:59
  Speaker 1: else in their life. And maybe this has reignited their
• 27:02
  Speaker 1: interest a little bit, and they're wondering, like, is the
• 27:04
  Speaker 1: door closed? Is there still a path for me to
• 27:06
  Speaker 1: like go back to school and get a degree in
• 27:09
  Speaker 1: physics and actually do physics for real? Yeah? And the
• 27:13
  Speaker 1: answer is no, Right, anyone can study physics even for real. Yeah,
• 27:18
  Speaker 1: it's never too late, And it depends on your life
• 27:21
  Speaker 1: and your personal situation, of course, and whether you have
• 27:23
  Speaker 1: the time available in the financial means to go back
• 27:26
  Speaker 1: to school. But there are lots of paths back into physics.
• 27:30
  Speaker 1: And something I think that a lot of people don't
• 27:32
  Speaker 1: understand is that you don't need like a formal physics
• 27:36
  Speaker 1: undergraduate degree from a fancy university to get back into physics.
• 27:41
  Speaker 1: I can tell the story of somebody here in Irvine
• 27:43
  Speaker 1: who was always interested in physics but ended up in
• 27:46
  Speaker 1: computers and working in software for fifteen years and then
• 27:50
  Speaker 1: came to me one day to my office and said, look,
• 27:52
  Speaker 1: I want to get back into physics. What can I do,
• 27:54
  Speaker 1: And he just ended up taking a bunch of classes
• 27:57
  Speaker 1: at u C I not as an enrolled student, just
• 27:59
  Speaker 1: like taking classes, which you can do at most universities
• 28:03
  Speaker 1: without getting into it like a degree program. You don't
• 28:05
  Speaker 1: need to apply to become a freshman. You just take
• 28:07
  Speaker 1: the classes you need. Then you can apply to graduate
• 28:10
  Speaker 1: schools and you can say, look, I've done these courses,
• 28:13
  Speaker 1: I've got reasonable grades in them. And that student, for example,
• 28:16
  Speaker 1: he's now a grad student at an Ivy League university
• 28:19
  Speaker 1: in physics. And so it's totally possible. If you have
• 28:23
  Speaker 1: the interest and you can do it in your spare
• 28:25
  Speaker 1: time and sort of build up the basic knowledge you need,
• 28:28
  Speaker 1: then you can jump right back in and the doors
• 28:31
  Speaker 1: can still be open. Yeah, you can still be like
• 28:33
  Speaker 1: a physicist at any point in your life. I mean,
• 28:36
  Speaker 1: people change careers all the time, And I mean I
• 28:38
  Speaker 1: know this one guy who was an engineer but then
• 28:41
  Speaker 1: he turned into a cartoonist. It sounds crazy, but you
• 28:45
  Speaker 1: can change careers. I heard he's now running a taco Chuck.
• 28:49
  Speaker 1: Isn't that true? Unfortunately it doesn't have a happy ending.
• 28:54
  Speaker 1: It's actually worse. He's doing a podcast. But the other
• 28:56
  Speaker 1: side to This is that you don't need to be
• 28:58
  Speaker 1: an official physicist with a hat p to ask interesting
• 29:02
  Speaker 1: questions about the universe and to think about it and
• 29:04
  Speaker 1: even to make progress. You know, there are lots of
• 29:06
  Speaker 1: people out there who have figured this stuff out on
• 29:09
  Speaker 1: their own, and physics is not owned by physics professors.
• 29:12
  Speaker 1: It belongs to everybody. Wondering and curiosity about the universe
• 29:16
  Speaker 1: belongs to everybody. So even if you aren't in a
• 29:18
  Speaker 1: situation in your life where you can't go back to
• 29:21
  Speaker 1: grad school in physics, you can still enjoy wondering about
• 29:24
  Speaker 1: the universe and learning about physics. Al Right, we have
• 29:27
  Speaker 1: a couple of more questions here from our most commonly
• 29:30
  Speaker 1: Asked Questions pile, and we'll get into them. They're about
• 29:33
  Speaker 1: black holes and gravitational waves. But first let's take another
• 29:37
  Speaker 1: quick break. All right, Daniel, we are going down our
• 29:52
  Speaker 1: list of most commonly asked questions to the podcast, and
• 29:56
  Speaker 1: our next question has to do with black holes. Question
• 29:59
  Speaker 1: goes do black holes move? And does this moving black
• 30:03
  Speaker 1: hole leave any trail quote unquote trail a stretched space?
• 30:08
  Speaker 1: And this is a question from a six year old
• 30:10
  Speaker 1: in particular. That's right, are you saying that a lot
• 30:13
  Speaker 1: of six year olds asked this question, or does this
• 30:15
  Speaker 1: six year old ask one of our most common questions. Yeah,
• 30:19
  Speaker 1: this six year old put his finger on a question
• 30:22
  Speaker 1: that we get a lot, which is, you know our
• 30:24
  Speaker 1: black holes sitting around or are they moving? And did
• 30:27
  Speaker 1: they leave with some sort of like wake in space
• 30:30
  Speaker 1: as they move the way like a boat leaves awake
• 30:32
  Speaker 1: in the lake. But I love that this question came
• 30:35
  Speaker 1: from a six year old thinking about black hole. So
• 30:38
  Speaker 1: congrats to is Sean and to his parents for encouraging
• 30:42
  Speaker 1: wonder and curiosity about the universe. Yes, so I guess
• 30:45
  Speaker 1: the question is, first of all, can black holes move
• 30:48
  Speaker 1: or are they so massive and monumental that they're basically
• 30:51
  Speaker 1: static in space? It's a great question, and we have
• 30:54
  Speaker 1: to remember, first of all that motion and position is
• 30:57
  Speaker 1: always relative, right, so there's no like absolute motion. You
• 31:01
  Speaker 1: can't ask is a black hole moving without saying what
• 31:04
  Speaker 1: is it moving relative to? The other side of that
• 31:07
  Speaker 1: is that black holes follow the same rules as everything else,
• 31:09
  Speaker 1: Stars and planets and galaxies, right, They all can move
• 31:13
  Speaker 1: through space or relative to each other, just like black holes.
• 31:16
  Speaker 1: And sometimes you'll see two black holes that are bound
• 31:20
  Speaker 1: to each other and orbiting each other. So yes, they
• 31:22
  Speaker 1: definitely can move through space just like everything else. Yeah,
• 31:26
  Speaker 1: and they can. I mean they basically add like any
• 31:28
  Speaker 1: other object in space to the things around them, right, Like,
• 31:33
  Speaker 1: you can have a black hole orbiting our solar system
• 31:36
  Speaker 1: for example. Yeah, you can't tell the difference gravitationally between
• 31:39
  Speaker 1: a black hole and another object of the same mass.
• 31:43
  Speaker 1: If you're at the same distance between those two, you
• 31:45
  Speaker 1: just can't tell the difference. They have the same gravitational effect.
• 31:48
  Speaker 1: So yeah, we could orbit a black hole the way
• 31:50
  Speaker 1: we orbit the Sun. We could have a tiny black
• 31:52
  Speaker 1: hole as part of our solar system that we wouldn't
• 31:55
  Speaker 1: even have noticed. In fact, there are those folks that
• 31:57
  Speaker 1: wonder about Planet nine whether it's a primordial hole that's
• 32:01
  Speaker 1: somehow stuck out there in the depth of our solar system.
• 32:04
  Speaker 1: So black holes can move through space, and you know,
• 32:07
  Speaker 1: there's even the possibility of black hole could move through
• 32:09
  Speaker 1: space and come disrupt our solar system. We did a
• 32:12
  Speaker 1: whole podcast episode about that. So yeah, they're not like
• 32:15
  Speaker 1: nailed in place there. They can move just like everything right. Yeah.
• 32:19
  Speaker 1: I wonder if what trips people up is that people
• 32:20
  Speaker 1: often talk about black holes or should I say, space
• 32:23
  Speaker 1: traps as being kind of these like holes punctured in
• 32:29
  Speaker 1: spacetime itself, or like these bubbles of space time. And
• 32:33
  Speaker 1: so maybe it's hard to think about it moving around
• 32:35
  Speaker 1: because it's I mean, when you punch a hole through
• 32:37
  Speaker 1: a piece of paper, it doesn't you can't move it.
• 32:40
  Speaker 1: That's a good point, but remember that's true for everything.
• 32:43
  Speaker 1: All kinds of matter change the shape of space, they
• 32:45
  Speaker 1: change the curvature they bend space, and where that is
• 32:50
  Speaker 1: just depends on your frame of reference, and whether it's
• 32:53
  Speaker 1: moving depends on whether you're moving. So if you can
• 32:56
  Speaker 1: move past a black hole, then a black hole can
• 32:58
  Speaker 1: move past you. There's no like absolute frame in which
• 33:02
  Speaker 1: these black holes are anchored. All right, Well, I guess
• 33:04
  Speaker 1: then the answer is yes, they can move. Space traps
• 33:08
  Speaker 1: can move, And so if you're out there in space,
• 33:11
  Speaker 1: watch out like you should look both ways before crossing
• 33:14
  Speaker 1: the Solar System lane. That's right. And the other part
• 33:17
  Speaker 1: of his question was whether or not they like leave
• 33:19
  Speaker 1: any trail behind them, and he like wake through space.
• 33:23
  Speaker 1: And we said earlier that the location of a black
• 33:25
  Speaker 1: hole and its velocity depends just on its frame of reference,
• 33:29
  Speaker 1: Like are you moving with respect to it. If so,
• 33:32
  Speaker 1: then it has velocity. But if a black hole is accelerating,
• 33:35
  Speaker 1: if it's changing its velocity, then it absolutely will leave
• 33:39
  Speaker 1: a wake through space the way a boat will when
• 33:42
  Speaker 1: it moves through a lake, and those weeks are called
• 33:44
  Speaker 1: gravitational waves. They will make these ripples in space. It's
• 33:48
  Speaker 1: like the change in velocity of something that is what
• 33:51
  Speaker 1: generates a gravitational wave. Yeah, exactly, because these frames of
• 33:56
  Speaker 1: reference are called inertial frames of reference, and you can't
• 33:59
  Speaker 1: tell the difference mean any of them as long as
• 34:01
  Speaker 1: they have no relative acceleration. But as soon as something
• 34:03
  Speaker 1: has an acceleration is changing its velocity, then it leaves
• 34:07
  Speaker 1: a signal through space. And those signals are these gravitational waves.
• 34:11
  Speaker 1: And that's what we've detected. In those underground detectors where
• 34:15
  Speaker 1: they have the long laser beams to measure the stretching
• 34:17
  Speaker 1: of space itself, they see two black holes, for example,
• 34:20
  Speaker 1: orbiting each other and leaving all these ripples in space,
• 34:24
  Speaker 1: which leads us to our next question. Speaking of gravitational waves,
• 34:27
  Speaker 1: another common question we get is our gravitational waves the
• 34:32
  Speaker 1: same as a graviton, meaning is a graviton a gravitational
• 34:36
  Speaker 1: wave or Can a gravitational wave be a graviton or
• 34:40
  Speaker 1: can just have a wave without a graviton. It's a
• 34:43
  Speaker 1: great question, and it's very natural because people think about
• 34:46
  Speaker 1: like electromagnetic waves, you know, they think about light, and
• 34:49
  Speaker 1: they know that light is made out of photons, these
• 34:51
  Speaker 1: little quantized units of electromagnetic radiation, and so it's very
• 34:55
  Speaker 1: natural to think about well, for gravity, if you have
• 34:58
  Speaker 1: gravitational waves, you know, is at the same thing as
• 35:00
  Speaker 1: a graviton, this whole particle wave duality. And the answer
• 35:04
  Speaker 1: is no. And the reason basically is that gravitational waves
• 35:07
  Speaker 1: are really really big. They're huge effects in gravity, and
• 35:11
  Speaker 1: gravitons if they exist, we expect them to be really
• 35:15
  Speaker 1: really really small. So a gravitational wave might be made
• 35:19
  Speaker 1: out of like zillions and zillions of gravitons the way,
• 35:22
  Speaker 1: for example, like a beam of light is made out
• 35:25
  Speaker 1: of lots and lots of photons, So they're not the
• 35:28
  Speaker 1: same thing. There are different scales and also gravitational waves,
• 35:31
  Speaker 1: and we know they exist. Gravitons still totally theoretic, right,
• 35:35
  Speaker 1: we don't know if they're actually real because we don't
• 35:37
  Speaker 1: know if gravity is quantum, that's right, The only theory
• 35:40
  Speaker 1: we have of gravity is this classical theory that says
• 35:43
  Speaker 1: that gravity is smooth and continuous. It's not like chopped
• 35:46
  Speaker 1: up into little units like everything else is. Like electromagnetic
• 35:50
  Speaker 1: waves are made out of little units we call photons.
• 35:52
  Speaker 1: You can't have an arbitrarily small size of them. They
• 35:55
  Speaker 1: come in discrete bits. And we don't know that about gravity.
• 35:58
  Speaker 1: We think probably it is because everything else is, but
• 36:01
  Speaker 1: we don't actually know that. We don't have a theory
• 36:03
  Speaker 1: for it. So the graviton is the particle you would
• 36:06
  Speaker 1: invent if you did have a theory of gravity. But
• 36:09
  Speaker 1: we know the gravitational waves are real. So those things
• 36:12
  Speaker 1: are out there, we've seen them. We don't know if
• 36:14
  Speaker 1: they're made out of tiny little gravitons. Right, it's kind
• 36:17
  Speaker 1: of like a water I guess, you know, like a
• 36:19
  Speaker 1: a wave in water. That's not the same as a
• 36:22
  Speaker 1: molecule of water. Yeah, we'd love to discover those water molecules.
• 36:26
  Speaker 1: We'd love to figure out if gravity is quantum and
• 36:28
  Speaker 1: if it's made out of gravitons. But we haven't seen
• 36:30
  Speaker 1: those yet. And it's really hard because even the gravitational
• 36:34
  Speaker 1: waves are hard to spot because gravity is really, really
• 36:37
  Speaker 1: weak compared to all the other forces. It's like billions
• 36:40
  Speaker 1: and trillions times weaker, which means it's very hard to
• 36:43
  Speaker 1: see it effects. And so to see a graviton would
• 36:46
  Speaker 1: be to see a even tinier little bit of gravity.
• 36:48
  Speaker 1: We're just not nearly sensitive enough, all right, So I
• 36:51
  Speaker 1: guess the answer is a gravitational wave is a gravity nut,
• 36:55
  Speaker 1: not necessarily graviton. All right. Then I think we have
• 36:59
  Speaker 1: time for one more of our most commonly asked question pile,
• 37:02
  Speaker 1: and I'm going to pick this one here, which says,
• 37:06
  Speaker 1: if he equals mc squared and a photon is massless,
• 37:10
  Speaker 1: then how does a photon have any energy? How can
• 37:13
  Speaker 1: a photon have energy if it's massless? Yeah, this is
• 37:16
  Speaker 1: a great question, and I love that people are doing
• 37:19
  Speaker 1: this thinking they're like, I have this one idea and
• 37:21
  Speaker 1: this other idea. Can I bring them together? Does this
• 37:23
  Speaker 1: make sense? And that's physics, right, that's doing physics. It's
• 37:26
  Speaker 1: saying I have this rule, where does it apply? Let
• 37:30
  Speaker 1: me check make sure that it applies everywhere I understand it.
• 37:33
  Speaker 1: And so it's great. Kudos to everybody who thinks about
• 37:35
  Speaker 1: this and to ask this question. This one came from
• 37:38
  Speaker 1: James Chad. And so the answer is that the formula
• 37:41
  Speaker 1: equals m C squared. It is not false, it's true,
• 37:44
  Speaker 1: but it's not the most general formula. It's only talking
• 37:47
  Speaker 1: about the energy that you get from mass. And there
• 37:50
  Speaker 1: are lots of forms of energy, right, there's energy and
• 37:52
  Speaker 1: mass is also energy of motion. Right, there's energy of rotation,
• 37:57
  Speaker 1: the energy of vibration. These are are other forms of energy, right,
• 38:01
  Speaker 1: But don't they all get lumped at the same energy
• 38:04
  Speaker 1: at the end, right, Like if I have a slow
• 38:07
  Speaker 1: moving particle and a fast moving particle, then the fast
• 38:10
  Speaker 1: moving particle has more energy and can transform into you know,
• 38:15
  Speaker 1: heavier particles. Yes, that's true. And so the most general
• 38:18
  Speaker 1: expression for energy is not E equals mc squared. That's
• 38:22
  Speaker 1: the expression you would use for a particle that's essentially
• 38:24
  Speaker 1: not moving. There's a more general expression that says E
• 38:27
  Speaker 1: equals mc squared plus momentum times the speed of light
• 38:31
  Speaker 1: P time c. So there's another term there. And so
• 38:36
  Speaker 1: for a photon, mass is zero. It doesn't have any
• 38:38
  Speaker 1: of this rest mass that the other particles have, but
• 38:41
  Speaker 1: it does have momentum. Photons are essentially are pure momentum.
• 38:46
  Speaker 1: There the wiggle of the electromagnetic field. There are pure motion,
• 38:50
  Speaker 1: there's no mass to them. But wait, it doesn't momentum
• 38:52
  Speaker 1: imply mass like it. Remember an engineering, when you study momentum,
• 38:55
  Speaker 1: it's M times V, so mass times velocity. That's the
• 38:59
  Speaker 1: non relativistic expression for momentum M times v. In relativity
• 39:04
  Speaker 1: we have a more general expression for momentum, and we
• 39:07
  Speaker 1: can dive deeper into that rabbit hole. But now you
• 39:09
  Speaker 1: do not have to have mass to have momentum, and
• 39:12
  Speaker 1: photons we know have momentum. We talked about for example,
• 39:15
  Speaker 1: solar sales. Photons themselves from the Sun can push on something.
• 39:19
  Speaker 1: When they bounce off of it, they transfer their momentum
• 39:22
  Speaker 1: to the solar sale. So we know physically empirically the
• 39:25
  Speaker 1: photons definitely do have momentum and they are essentially pure momentum.
• 39:30
  Speaker 1: And so equals mc squared is the best known formula,
• 39:33
  Speaker 1: but it's not the most general case, and imparticle physics,
• 39:36
  Speaker 1: we use equals mc squared plus pc and so for
• 39:40
  Speaker 1: the photon m equal zero and the energy is just
• 39:43
  Speaker 1: momentum times the speed of light p time c. So
• 39:45
  Speaker 1: it does have energy. Photons have energy, it just doesn't
• 39:49
  Speaker 1: come from it having mass. It just comes from its motion.
• 39:52
  Speaker 1: That's right. There are other ways to have energy, and
• 39:53
  Speaker 1: that's what photons do, and they're weird because they have
• 39:56
  Speaker 1: exactly zero mass. And it's more general. Formula applies to
• 39:59
  Speaker 1: me in you too, Like my energy is both how
• 40:03
  Speaker 1: much I wait, but also how much a movie? Yeah, exactly,
• 40:07
  Speaker 1: you have more energy if you're in motion then when
• 40:08
  Speaker 1: you're sitting on your couch. Who all right, Well, those
• 40:13
  Speaker 1: are some of our most common questions, Daniel. What do
• 40:16
  Speaker 1: you sort of make of all these questions? I make
• 40:19
  Speaker 1: that we have smart listeners, then that we have people
• 40:21
  Speaker 1: out there that are intrigued by the way the universe works,
• 40:24
  Speaker 1: and that this stuff is complicated, and that if you
• 40:27
  Speaker 1: try to download it into your brain and play around
• 40:30
  Speaker 1: with it, you'll find little rough edges that you don't
• 40:32
  Speaker 1: quite understand, or little bits that don't quite click together,
• 40:36
  Speaker 1: and that that's not unusual, and that there are a
• 40:38
  Speaker 1: lot of other people out there wondering about those same
• 40:40
  Speaker 1: tricky bits. So I hope that these answers have helped
• 40:43
  Speaker 1: a lot of people collect those pieces together, and if not,
• 40:47
  Speaker 1: feel free to write into us. We would love to
• 40:48
  Speaker 1: help you resolve little questions you have about your understanding
• 40:52
  Speaker 1: about the universe. Yeah, and in some cases I feel
• 40:54
  Speaker 1: like your answer was we don't know, which means that
• 40:57
  Speaker 1: these are questions that physicists are also asking themselves at
• 41:01
  Speaker 1: the forefront of science. Yeah. Basically, at the end of
• 41:04
  Speaker 1: every question, you could add and what does that even mean?
• 41:07
  Speaker 1: Exclamation point question mark? And we'll add a few more
• 41:11
  Speaker 1: question marks there at the end. Two. That should be
• 41:12
  Speaker 1: the alt title for our podcast exclamation point question mark
• 41:18
  Speaker 1: or maybe our next book, Daniel, what does that even mean?
• 41:21
  Speaker 1: Exclamation point question mark? To which the answer is the
• 41:25
  Speaker 1: title of our first book. We have no idea. It's
• 41:28
  Speaker 1: a recursive book. Really, that's right. Book three. Let's just
• 41:31
  Speaker 1: go get tacos. Go go back and read our first
• 41:34
  Speaker 1: book while eating some tacos and increasing your volume. That's
• 41:38
  Speaker 1: all right. Well, we hope you enjoyed that and maybe
• 41:41
  Speaker 1: connected a little bit more with people out there, because
• 41:44
  Speaker 1: we all have a lot of the same questions about
• 41:45
  Speaker 1: the universe and don't be shy about writing to us,
• 41:48
  Speaker 1: were engaging with us on Twitter at Daniel and Jorge
• 41:51
  Speaker 1: or sending us email to questions at Daniel and Jorge
• 41:54
  Speaker 1: dot com. We love your listener questions and we answer
• 41:57
  Speaker 1: all of our email. Yeah, and don't be shy but
• 41:59
  Speaker 1: ask questions and pursuing knowledge and even maybe getting a
• 42:03
  Speaker 1: physics degree late in life. Thanks for joining us, see
• 42:08
  Speaker 1: you next time. Thanks for listening, and remember that Daniel
• 42:18
  Speaker 1: and Jorge explained The Universe is a production of I
• 42:21
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• 42:28
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