Latest / Daniel and Kelly’s Extraordinary Universe / Listener Questions #51

Transcript

Listener Questions #51 · Daniel and Kelly’s Extraordinary Universe

• 0:07
  Speaker 1: Photons slow down when they approach space with a curve.
• 0:11
  Speaker 1: Is that real or just some illusion we observe?
• 0:14
  Speaker 2: If plastic waste were edible, humans would all eat like kings.
• 0:19
  Speaker 3: Can any species fill this niche? Are there plastic eating things?
• 0:23
  Speaker 1: If you and I disagree on what's now in the
• 0:26
  Speaker 1: space-time sea, does tomorrow already exist or is it still
• 0:31
  Speaker 1: up to me?
• 0:32
  Speaker 2: Whatever questions keep you up at night, Daniel and Kelly's
• 0:36
  Speaker 2: answers will make it right.
• 0:38
  Speaker 1: Welcome to Daniel and Kelly's Extraordinary Universe of Listener Curiosity.
• 0:43
  Speaker 3: Episode number 51.
• 0:44
  Speaker 2: 51!
• 0:45
  Speaker 4: That's a new thing we do. I don't know that
• 1:01
  Speaker 4: it adds anything.
• 1:02
  Speaker 3: But I enjoy it.
• 1:04
  Speaker 1: I just enjoy hearing the big number, like, wow, think
• 1:07
  Speaker 1: about all the questions we've answered.
• 1:08
  Speaker 2: Yeah, I mean, that's like 150 questions from listeners that we've, like,
• 1:13
  Speaker 2: it's 150 things that have been shared with us.
• 1:15
  Speaker 3: That's exciting.
• 1:16
  Speaker 1: Exactly. Well, hello, everyone. I'm Daniel Whiteson. I'm a particle physicist,
• 1:21
  Speaker 1: and I write books about aliens and the nature of science.
• 1:25
  Speaker 2: And I'm Kelly Wienersmith. I study parasites and space, and
• 1:29
  Speaker 2: I'm interested in medical history this week. Not that we're
• 1:33
  Speaker 2: talking about that today, but that's what's.
• 1:35
  Speaker 5: On my mind.
• 1:37
  Speaker 1: Well, speaking of interest in the Wienersmith household, I have
• 1:40
  Speaker 1: a question for you, Kelly.
• 1:41
  Speaker 3: Oh, go for it. I hope it's about my goats.
• 1:46
  Speaker 1: I'll make it about your goats. All right. So my
• 1:48
  Speaker 1: question for you is, have your husband or your goats
• 1:52
  Speaker 1: considered starting their own podcast?
• 1:55
  Speaker 2: That is such a great question.
• 1:57
  Speaker 3: You know, my goats have a strong desire to be heard.
• 2:00
  Speaker 1: Mm-hmm. And the listeners want to hear from your goats.
• 2:03
  Speaker 1: So there's a built in audience. We've had requests.
• 2:06
  Speaker 2: Yeah, but I don't know that they're going to want
• 2:07
  Speaker 2: to hear that more than once because they all have
• 2:10
  Speaker 2: very distinct voices, which I think is interesting. I can
• 2:13
  Speaker 2: hear one of them call and I'm like, oh, Leia's
• 2:15
  Speaker 2: head is stuck in the fence again. Like, I just
• 2:17
  Speaker 2: I know them by their voices. But I don't think
• 2:19
  Speaker 2: there's a big audience for that.
• 2:21
  Speaker 3: However.
• 2:22
  Speaker 1: Really?
• 2:22
  Speaker 6: Yeah.
• 2:23
  Speaker 2: My amazing husband, he's really into AI. Every morning we
• 2:27
  Speaker 2: have coffee together and it's pretty much 30.
• 2:30
  Speaker 3: Solid minutes of Zach AI-ing at me.
• 2:33
  Speaker 2: And he is always reading about the newest things that's
• 2:37
  Speaker 2: going on, the new math problems that's been solved, thinking
• 2:40
  Speaker 2: about what this means for the future of humanity.
• 2:41
  Speaker 4: Cool.
• 2:42
  Speaker 1: Cool.
• 2:43
  Speaker 2: And it turns out his brother, Marty Wiener, also thinks
• 2:46
  Speaker 2: about AI a lot. And so does Chris Slow, who's
• 2:49
  Speaker 2: the current chief technical officer at Reddit. And Zach's brother, Marty,
• 2:53
  Speaker 2: would probably want you to know that he's not just
• 2:55
  Speaker 2: Zach's brother. He also was the chief technical officer at
• 3:00
  Speaker 2: Reddit and was one of the early engineers over at Pinterest.
• 3:02
  Speaker 2: He's like a big Silicon Valley dude. But anyway, they
• 3:06
  Speaker 2: have a podcast about AI called Last Humans in the Loop.
• 3:10
  Speaker 3: And I think they've got like five or six episodes.
• 3:12
  Speaker 3: They've just started.
• 3:12
  Speaker 2: And it is a fascinating look at AI. You too
• 3:17
  Speaker 2: can hear Zach Wienersmith talk about AI.
• 3:21
  Speaker 1: So if you are not satisfied just hearing Kelly throw
• 3:24
  Speaker 1: shade at Zach, you can also hear Zach throw shade
• 3:26
  Speaker 1: at Kelly. Get more Wienersmith in your ear.
• 3:29
  Speaker 2: There you go. Yes, I highly recommend it. And they
• 3:32
  Speaker 2: do videos, so you can see all of them responding
• 3:35
  Speaker 2: in real time. Marty had this really great bit where
• 3:38
  Speaker 2: you can now download voices of some actors, and he had...
• 3:41
  Speaker 2: I think it was he downloaded the voice of Kermit
• 3:44
  Speaker 2: the Frog reading a particularly violent scene in the Odyssey,
• 3:47
  Speaker 2: and he did it with a puppet at the same
• 3:49
  Speaker 2: time on the show.
• 3:51
  Speaker 3: Anyway, most of it is serious, but that cracked me up.
• 3:54
  Speaker 2: And anyway, yes, highly recommend it for shenanigans and for
• 3:58
  Speaker 2: real serious AI news.
• 3:59
  Speaker 1: Wow. So that's an application of AI that's really going
• 4:02
  Speaker 1: to change everybody's life. I can see they really put
• 4:05
  Speaker 1: their finger on the important issues, haven't they?
• 4:07
  Speaker 3: They've done a mixture of things.
• 4:11
  Speaker 2: I think at the end they talk about sort of frivolous,
• 4:13
  Speaker 2: funny AI stuff as like, you know, a closer.
• 4:16
  Speaker 3: And that was a bit of closer.
• 4:18
  Speaker 7: All right.
• 4:18
  Speaker 1: Well, today we are not just here to talk about
• 4:20
  Speaker 1: the things that the Wienersmiths are excited about, though partially
• 4:24
  Speaker 1: we are. We're here to address questions that you have
• 4:28
  Speaker 1: because we're curious about the universe and so are you.
• 4:31
  Speaker 1: And we want to know about that curiosity. We want
• 4:33
  Speaker 1: to understand why. where it takes you, and especially where
• 4:37
  Speaker 1: you get stuck. What ideas are not working together in
• 4:40
  Speaker 1: your head? What concepts don't make sense? What have we
• 4:43
  Speaker 1: talked about that didn't quite connect? Or what did you
• 4:46
  Speaker 1: hear on another podcast, maybe with other wienersmiths, that didn't
• 4:49
  Speaker 1: make sense to you and you need a Daniel and
• 4:52
  Speaker 1: Kelly treatment? Please send us your questions and your curiosity
• 4:56
  Speaker 1: to questions at danielandkelly.org.
• 4:58
  Speaker 2: So let's jump right in with our first question. This
• 5:00
  Speaker 2: first question is from Lincoln from Florida, and Lincoln makes
• 5:04
  Speaker 2: a pretty strong case for Florida.
• 5:06
  Speaker 3: So let's go ahead and listen.
• 5:08
  Speaker 7: Hello, it's Lincoln here from the best of the 50 states, Florida.
• 5:13
  Speaker 7: If you don't agree, check the tourist count. According to
• 5:17
  Speaker 7: special relativity, the velocity of light always appears to us
• 5:20
  Speaker 7: as C. However, as the object approaches a black hole,
• 5:23
  Speaker 7: it appears to any observer to slow down and stop
• 5:26
  Speaker 7: before reaching the event horizon. Does this phenomenon actually occur?
• 5:31
  Speaker 7: If so, could this be used in the distant future
• 5:33
  Speaker 7: to study light and potentially begin to understand its fundamental nature?
• 5:38
  Speaker 7: Thank you for providing a place for questions that make
• 5:41
  Speaker 7: my friends stare blankly. Best regards, from Lincoln.
• 5:46
  Speaker 1: I like that Lincoln is using data to answer questions.
• 5:49
  Speaker 1: You know, he's not just making wild claims about what
• 5:52
  Speaker 1: state is best.
• 5:53
  Speaker 2: Money talks, I guess. And there's a lot of money
• 5:56
  Speaker 2: talking in Florida, I guess.
• 5:58
  Speaker 1: Well, I was just in Florida this week, and there's
• 6:01
  Speaker 1: other data, I think, that points in the other direction,
• 6:04
  Speaker 1: like the humidity and the temperature together points very negatively
• 6:08
  Speaker 1: towards Florida being the best state. But hey, you know,
• 6:11
  Speaker 1: pick your metric.
• 6:12
  Speaker 2: But you made the mistake of mentioning the other day
• 6:14
  Speaker 2: that Los Angeles was the most humid location on the
• 6:17
  Speaker 2: planet last week or something, right?
• 6:19
  Speaker 1: In the country, yes. Oh, in the country. But it
• 6:23
  Speaker 1: was pretty sticky in L.A. last week. And that was
• 6:25
  Speaker 1: a complaint. I was not bragging. I was like, things
• 6:28
  Speaker 1: are going downhill because California is approaching Florida or approaching
• 6:32
  Speaker 1: Virginia levels of stickiness. Not good.
• 6:35
  Speaker 2: All right.
• 6:36
  Speaker 3: All right. Let's get back to the science. Let's get
• 6:39
  Speaker 3: back to the science.
• 6:39
  Speaker 2: So we're talking about special relativity here.
• 6:42
  Speaker 3: Give me the background on special relativity.
• 6:44
  Speaker 1: So we're talking about special and general relativity here because
• 6:47
  Speaker 1: he's asking a question about the speed of light near
• 6:50
  Speaker 1: a black hole. But let's start with special relativity because
• 6:54
  Speaker 1: the issue at the heart of this question is a
• 6:56
  Speaker 1: conflict between what you often hear from special relativity and
• 7:00
  Speaker 1: what we've learned from general relativity about how light moves.
• 7:03
  Speaker 1: So let's start with special relativity. And the big fact
• 7:06
  Speaker 1: at the heart of special relativity is that light always
• 7:08
  Speaker 1: moves at the same speed. So if you have a
• 7:11
  Speaker 1: flashlight and you click it on, light is zooming out
• 7:13
  Speaker 1: of your flashlight at the speed of light. If you
• 7:16
  Speaker 1: happen to be on a train moving at half the
• 7:18
  Speaker 1: speed of light, somebody on the ground is going to
• 7:20
  Speaker 1: see you moving at half the speed of light. And
• 7:22
  Speaker 1: when they measure the speed of your flashlight beam, it's
• 7:25
  Speaker 1: not going to be one and a half times the
• 7:27
  Speaker 1: speed of light. It's still going to be the speed
• 7:29
  Speaker 1: of light. So that flashlight beam moves at the speed
• 7:31
  Speaker 1: of light relative to you on the train, relative to
• 7:34
  Speaker 1: the guy on the ground, relative to a particle moving
• 7:37
  Speaker 1: through space, relative to somebody sunning themselves on the beach
• 7:40
  Speaker 1: of Florida and getting skin cancer, relative to all of
• 7:42
  Speaker 1: those people.
• 7:43
  Speaker 3: I went dark.
• 7:43
  Speaker 1: It's constant. Unlike humidity in LA, which seems to go
• 7:47
  Speaker 1: up and down a lot, the speed of light is constant.
• 7:50
  Speaker 3: Right. Okay. And that's not you all just getting something wrong, right?
• 7:53
  Speaker 3: That's real?
• 7:54
  Speaker 1: That's right. That's real. That's something we've measured. It's fascinating.
• 7:57
  Speaker 1: It's counterintuitive. It was a big surprise experimentally. It took
• 8:01
  Speaker 1: forever for people to really absorb it and accept it,
• 8:04
  Speaker 1: but it's real. And it leads to all the consequences
• 8:07
  Speaker 1: of special relativity. The fact that there's no universal now
• 8:10
  Speaker 1: that we'll talk about later in the program, and the
• 8:13
  Speaker 1: fact that things get shorter as they get faster, the
• 8:16
  Speaker 1: time slows down, all comes from the same basic fact
• 8:19
  Speaker 1: that light moves at the same speed, no matter what,
• 8:22
  Speaker 1: whoever is measuring it, right? And that's true no matter
• 8:25
  Speaker 1: what your frame of reference is. If you're in motion
• 8:28
  Speaker 1: relative to the Earth, or if you're not, or if
• 8:30
  Speaker 1: you're pointing in this direction or pointing in that direction.
• 8:33
  Speaker 1: And this is often said very, very absolutely, like the
• 8:35
  Speaker 1: speed of light always moves at the speed of light.
• 8:38
  Speaker 1: But there is a very important asterisk that's usually ignored
• 8:41
  Speaker 1: that's going to be really crucial today.
• 8:43
  Speaker 3: Okay.
• 8:44
  Speaker 1: And that asterisk is that this is true, that the
• 8:47
  Speaker 1: speed of light is the speed of light no matter what,
• 8:50
  Speaker 1: as long as you are operating in flat space.
• 8:54
  Speaker 3: What?
• 8:54
  Speaker 1: So space is not curved. So if space is flat
• 8:57
  Speaker 1: and from here to the end of the universe, space
• 8:59
  Speaker 1: is flat, then you can make this claim and you
• 9:01
  Speaker 1: can measure velocity. And this is all true. But once
• 9:04
  Speaker 1: space gets curved, you need general relativity to describe what's
• 9:07
  Speaker 1: going to happen and how time flows and how things move.
• 9:11
  Speaker 1: Special relativity no longer applies when space is curved. And
• 9:15
  Speaker 1: that's what happens near black holes.
• 9:17
  Speaker 2: So how much of space is flat and how much
• 9:19
  Speaker 2: of space is curved? Do you just get curves near
• 9:21
  Speaker 2: black holes or more info?
• 9:23
  Speaker 1: Amazing question. Yeah, great question. So on the whole, the
• 9:28
  Speaker 1: universe is flat. Like if you measure the curvature of
• 9:31
  Speaker 1: the whole universe, it's on average flat. But on average
• 9:34
  Speaker 1: flat doesn't mean locally flat. Like, you know, if the
• 9:37
  Speaker 1: temperature on average in the United States is 75 degrees,
• 9:41
  Speaker 1: that doesn't mean that it's 75 degrees in Florida. In fact,
• 9:43
  Speaker 1: it's probably not. It's never 75 degrees in Florida. It's
• 9:48
  Speaker 1: always 95. Anyway, near black holes, space is very, very curved.
• 9:53
  Speaker 1: Or near the Earth, space is gently curved. However, space
• 9:57
  Speaker 1: is always flat near you. There's always some neighborhood around
• 10:02
  Speaker 1: you where space is approximately flat. And how big that
• 10:06
  Speaker 1: neighborhood is depends on the amount of curvature. So if
• 10:08
  Speaker 1: you're in a part of the universe where there really
• 10:10
  Speaker 1: are no masses, then space is flat in a really
• 10:12
  Speaker 1: broad neighborhood. Even if you're falling into a black hole
• 10:16
  Speaker 1: and space is really, really curved, there's always like a
• 10:18
  Speaker 1: tiny little neighborhood in your vicinity where you can say,
• 10:21
  Speaker 1: all right, but around here within like a meter or so,
• 10:25
  Speaker 1: space is close enough to flat for me to say
• 10:27
  Speaker 1: that it's flat. So it's always flat in your little neighborhood.
• 10:31
  Speaker 3: Okay, got it.
• 10:31
  Speaker 2: It's like how the earth is round, but it doesn't
• 10:34
  Speaker 2: look round to me because it's flat in my little area.
• 10:36
  Speaker 1: Exactly, because you can only see a little bit of it.
• 10:38
  Speaker 1: And so it looks basically flat. If you zoom down
• 10:40
  Speaker 1: and consider the whole earth, You'd see the curvature. But
• 10:43
  Speaker 1: it's a good approximation to say the Earth is flat
• 10:45
  Speaker 1: around you, right?
• 10:46
  Speaker 7: Okay.
• 10:46
  Speaker 1: All right. So, Lincoln is saying, hold on. I hear
• 10:49
  Speaker 1: that the velocity of light is always C, right? No
• 10:51
  Speaker 1: matter what. But near a black hole, time slows down
• 10:56
  Speaker 1: and even stops as things approach the event horizon. What
• 10:59
  Speaker 1: happens to a photon as it approaches the black hole?
• 11:01
  Speaker 1: And does that break the rule of special relativity, right?
• 11:04
  Speaker 1: And the answer is … is both really unsatisfying and
• 11:09
  Speaker 1: also really deeply revealing about something really basic and intuitive
• 11:13
  Speaker 1: that we don't often think about, which is how to
• 11:15
  Speaker 1: measure velocity. So the brief answer, which is really unsatisfying,
• 11:20
  Speaker 1: is that you cannot measure the velocity of things outside
• 11:23
  Speaker 1: your immediate neighborhood. Like the velocity of things that are
• 11:27
  Speaker 1: far away is not even well-defined. It's not even a
• 11:30
  Speaker 1: quantity we really know how to talk about. And so
• 11:34
  Speaker 1: the answer is, You can't talk about the speed of
• 11:36
  Speaker 1: photons that are far away from you in curved space.
• 11:39
  Speaker 1: If they're in your neighborhood, then they're basically in your
• 11:41
  Speaker 1: little flat bubble and you can measure their speed and
• 11:44
  Speaker 1: you always get C. If space is curved and the
• 11:47
  Speaker 1: photons are not in your flat bubble, there's like a
• 11:49
  Speaker 1: lot of curvature between you and them, then there's no
• 11:52
  Speaker 1: way to even define their velocity.
• 11:54
  Speaker 3: Okay. You think one day we'd figure out how to
• 11:57
  Speaker 3: do it or it's just impossible?
• 11:59
  Speaker 1: It's just impossible, right? And general relativity tells us why.
• 12:03
  Speaker 1: And I love this kind of thing in relativity because
• 12:05
  Speaker 1: it forces you to revisit something which sounds simple and
• 12:08
  Speaker 1: obvious and think about the assumptions that go into it
• 12:11
  Speaker 1: and then realize those are broken. And so you might
• 12:13
  Speaker 1: be wondering, like, what is he talking about? How could
• 12:16
  Speaker 1: you not measure something's velocity? Velocity is just like I'm
• 12:20
  Speaker 1: measuring the distance and I'm seeing how that changes with time, right? Duh. Obviously,
• 12:24
  Speaker 1: you can still make those measurements.
• 12:26
  Speaker 3: That's what I was thinking.
• 12:27
  Speaker 2: Duh.
• 12:29
  Speaker 1: Well, let's think in a little bit more detail about
• 12:31
  Speaker 1: what happens when we measure velocity, right? Technically, what we
• 12:34
  Speaker 1: do is we compare two vectors. Take a simple example.
• 12:37
  Speaker 1: We have two people. They're running next to each other, right?
• 12:40
  Speaker 1: You have Daniel versus Usain Bolt, right? And you might think,
• 12:44
  Speaker 1: what do we do? How do we measure their velocities? Well,
• 12:46
  Speaker 1: we just see how they move across the earth, and
• 12:48
  Speaker 1: we measure the distance versus time, and that's the answer.
• 12:51
  Speaker 1: And it's true that we get the distance versus time
• 12:53
  Speaker 1: for each person, and that gives us two vectors, a
• 12:57
  Speaker 1: length and a direction for Usain Bolt and a length
• 12:59
  Speaker 1: and a direction for Daniel, and then we compare them, right?
• 13:02
  Speaker 1: And because Daniel and Usain Bolt are running in the
• 13:04
  Speaker 1: same direction right next to each other, the comparison is obvious.
• 13:07
  Speaker 1: One's really big. One's not so big. Usain Bolt is
• 13:10
  Speaker 1: faster than Daniel. Easy to do. All right. But what
• 13:14
  Speaker 1: if Daniel can't get Usain Bolt to come and race
• 13:16
  Speaker 1: against him right here? He can't get him to come
• 13:18
  Speaker 1: to Southern California. Instead, Usain Bolt is running on a
• 13:22
  Speaker 1: track on the other side of the planet than Daniel. Okay. Okay.
• 13:25
  Speaker 1: How do we do it now? Well, we still have
• 13:27
  Speaker 1: to compare vectors, but Usain Bolt's vector... is now pointing
• 13:30
  Speaker 1: in a different direction than Daniel's, right? Because the Earth
• 13:33
  Speaker 1: is curved. And imagine he's like on the opposite side
• 13:36
  Speaker 1: of the Earth and he's running in the other direction.
• 13:38
  Speaker 1: So how do you compare the two vectors now? And
• 13:40
  Speaker 1: you're thinking, okay, easy still. You just like bring one
• 13:44
  Speaker 1: vector over to the other and line them up so
• 13:46
  Speaker 1: you can compare them, right?
• 13:47
  Speaker 3: Duh.
• 13:48
  Speaker 1: Duh. And that works if space is flat. But the
• 13:53
  Speaker 1: problem is that when you move a vector through curved space,
• 13:57
  Speaker 1: there's a lot of different ways you can do it.
• 13:59
  Speaker 1: And the choice that you make of how to do
• 14:01
  Speaker 1: it gives you a different answer, right?
• 14:03
  Speaker 2: But it's flat in your area and Usain Bolt is
• 14:09
  Speaker 2: running in a little flat bit.
• 14:11
  Speaker 3: Why can't we compare the vectors?
• 14:14
  Speaker 1: You can do an approximation. You've said, I'm just going
• 14:15
  Speaker 1: to take the length of the vector, right? But really
• 14:18
  Speaker 1: velocity is a 3D object. And so you have to
• 14:20
  Speaker 1: do a complete comparison. And so let me walk you
• 14:23
  Speaker 1: through this example of what I mean by the vectors
• 14:25
  Speaker 1: change through curved space.
• 14:27
  Speaker 3: Okay.
• 14:27
  Speaker 1: So say, for example, you're at the North Pole and
• 14:31
  Speaker 1: you have a spear, okay? And your job is to
• 14:34
  Speaker 1: go on a little walk across the earth and keep
• 14:37
  Speaker 1: the spear pointed in the same direction, okay? So it's
• 14:40
  Speaker 1: parallel to the ground. You're starting at the North Pole
• 14:42
  Speaker 1: and maybe you point your spear towards London, okay? Okay.
• 14:46
  Speaker 1: So it's pointing south, right?
• 14:47
  Speaker 7: Yes.
• 14:47
  Speaker 3: I'm menacingly walking towards London.
• 14:49
  Speaker 5: Yes.
• 14:50
  Speaker 6: All right.
• 14:50
  Speaker 1: So you walk towards London with shaking your spear, keeping
• 14:53
  Speaker 1: it parallel to the ground.
• 14:54
  Speaker 2: Okay.
• 14:54
  Speaker 1: It's still pointing south. Now you walk past London, you
• 14:57
  Speaker 1: get all the way to the equator. Okay, still pointing south.
• 15:01
  Speaker 1: Now you walk along the equator, maybe like a quarter
• 15:04
  Speaker 1: of the way around the planet. Your spear is still
• 15:06
  Speaker 1: pointing south, right?
• 15:07
  Speaker 3: Okay.
• 15:07
  Speaker 1: Now you walk back towards the North Pole.
• 15:10
  Speaker 7: Okay. Okay.
• 15:10
  Speaker 1: Spear still pointing south. Has your spear changed direction?
• 15:15
  Speaker 3: I rotate my hand.
• 15:16
  Speaker 1: But is your spear pointing the same direction it was originally?
• 15:19
  Speaker 3: No, not if I'm walking back north again.
• 15:22
  Speaker 1: Yeah, exactly. It's now like 90 degrees relative to where
• 15:25
  Speaker 1: it was before. So you have taken a vector and
• 15:27
  Speaker 1: you've moved it along a curved surface and you've cut
• 15:30
  Speaker 1: them on a complete path and you've never turned your vector, right?
• 15:34
  Speaker 1: And yet it's not pointing in the same direction as
• 15:36
  Speaker 1: when you started. This is geometrically what we mean by curvature.
• 15:41
  Speaker 1: If you take a vector and you take a journey
• 15:43
  Speaker 1: and you come back and it's not pointing in the
• 15:44
  Speaker 1: same direction, then that space is curved. That's what we
• 15:48
  Speaker 1: mean by curvature in some sense geometrically. So if you
• 15:51
  Speaker 1: want to compare two vectors that are separated, in flat space,
• 15:55
  Speaker 1: it makes sense. In curved space, it does not make
• 15:58
  Speaker 1: sense because you have to bring the vector over close
• 16:01
  Speaker 1: to you in order to measure it, and that changes
• 16:04
  Speaker 1: the vector. It can change the direction. It can change
• 16:06
  Speaker 1: the length of the vector. And so that's why velocity
• 16:10
  Speaker 1: for distant objects is not well-defined in curved space because
• 16:14
  Speaker 1: different people can choose differently. Like, I'm going to bring
• 16:17
  Speaker 1: that photon's distant vector over over to me this way.
• 16:19
  Speaker 1: Somebody else can bring it over here this way. And
• 16:22
  Speaker 1: if space is curved, they can get different answers. And
• 16:24
  Speaker 1: so there's not one definition for what that velocity is.
• 16:28
  Speaker 1: And so the cop-out answer that simultaneously, I think, reveals
• 16:31
  Speaker 1: something cool about the assumptions we make when we talk
• 16:34
  Speaker 1: about velocity is you can't talk about the velocity of
• 16:37
  Speaker 1: really distant objects. For example, when we say distant galaxies
• 16:42
  Speaker 1: are recessing at faster than the speed of light, right?
• 16:45
  Speaker 1: Isn't that breaking the rules of special relativity? Yeah, because
• 16:48
  Speaker 1: that velocity is not actually meaningful. It's a way we
• 16:50
  Speaker 1: talk about velocity to give people a sense for it.
• 16:54
  Speaker 1: But in general relativity, you can't really talk about the
• 16:56
  Speaker 1: velocity of those distant galaxies. What's really happening is space
• 17:00
  Speaker 1: is expanding between us and them. For example, those galaxies
• 17:04
  Speaker 1: are not experiencing any acceleration, right? No accelerometers in those
• 17:07
  Speaker 1: distant galaxies are indicating that they're accelerating relative to us.
• 17:11
  Speaker 1: So the right way to think about that is space
• 17:13
  Speaker 1: is expanding. And the right way to think about this
• 17:15
  Speaker 1: is that space is curved between you and that photon.
• 17:18
  Speaker 1: So you can't really measure the velocity. You can measure
• 17:20
  Speaker 1: an apparent velocity. You can keep track of where it's
• 17:23
  Speaker 1: going at various intervals. And you can calculate what we
• 17:25
  Speaker 1: call a coordinate velocity. Like here are the measurements I made.
• 17:28
  Speaker 1: Here's what I would call the velocity. But it's not
• 17:30
  Speaker 1: the same velocity somebody else would measure. And it's not
• 17:33
  Speaker 1: just observer dependent. It depends on the choices you make
• 17:37
  Speaker 1: of coordinates. which are arbitrary in general relativity. And so
• 17:40
  Speaker 1: it's not well defined, unfortunately. So the story you hear
• 17:44
  Speaker 1: when they say a photon, as it approaches a black hole,
• 17:47
  Speaker 1: slows down, It's not bogus. It's just that it's an
• 17:50
  Speaker 1: extension of these concepts beyond where they're really physical. And
• 17:54
  Speaker 1: so Lincoln is asking, does that phenomenon actually occur? And
• 17:58
  Speaker 1: I would say no. And the reason is that if
• 18:01
  Speaker 1: you moved your observer too close to that photon, like
• 18:04
  Speaker 1: if you zoomed in and stood near the edge of
• 18:06
  Speaker 1: the event horizon, what would you see? Well, if you're
• 18:09
  Speaker 1: near the photon, you're going to see it moving by
• 18:11
  Speaker 1: you at the speed of light. And if you fall
• 18:13
  Speaker 1: into a black hole, you don't see time slow down.
• 18:16
  Speaker 1: You just fall into a black hole and you move
• 18:18
  Speaker 1: through the event horizon and towards the singularity. So this
• 18:21
  Speaker 1: apparent slowdown is not a real physical phenomenon. It's an
• 18:25
  Speaker 1: artifact of being distant and of there being a lot
• 18:27
  Speaker 1: of curvature between you and the object. And unfortunately, there
• 18:32
  Speaker 1: is no solid answer to what is the velocity of
• 18:35
  Speaker 1: a distant object outside of your little flat neighborhood.
• 18:38
  Speaker 6: Wow.
• 18:39
  Speaker 3: All right. Lincoln, that was a lot, man.
• 18:43
  Speaker 2: But there are definitely days where I'm like, oh, that's
• 18:46
  Speaker 2: going to take me a week to think more about.
• 18:50
  Speaker 2: But it was a great explanation. Physics is not always intuitive.
• 18:53
  Speaker 1: It isn't, yeah.
• 18:54
  Speaker 3: And so, Lincoln, what do you think?
• 18:57
  Speaker 1: What you thinking, Lincoln?
• 18:59
  Speaker 3: Do you think that's the first time he's heard that?
• 19:04
  Speaker 1: You couldn't just let me have that, huh?
• 19:06
  Speaker 3: No, that's not how you and I roll.
• 19:09
  Speaker 7: Hello again from the greatest state, Florida. And may I
• 19:13
  Speaker 7: point out that the humidity and the heat is normal
• 19:17
  Speaker 7: to us, and you're just not a Floridian. Thank you
• 19:20
  Speaker 7: so much for a clear and conceivable answer to my question.
• 19:26
  Speaker 7: Although it is a little disappointing, at least now I
• 19:32
  Speaker 7: can understand how special relativity is just Einstein flexing. Thank
• 19:38
  Speaker 7: you for the answer, and may you always understand why
• 19:42
  Speaker 7: Florida is the best state. Also, that's like the fourth
• 19:46
  Speaker 7: time I've heard Lincoln thinking this week.
• 20:09
  Speaker 1: All right, we're back and we're answering questions from listeners.
• 20:12
  Speaker 1: And as is tradition, apparently on today's episode, we are
• 20:15
  Speaker 1: making lots of references to other podcasts on today's episode
• 20:19
  Speaker 1: because we know you listen to other podcasts and that's cool.
• 20:22
  Speaker 1: We do too. We don't expect an exclusive relationship. We
• 20:26
  Speaker 1: want to know what else you're excited about.
• 20:28
  Speaker 3: Daniel, what podcast do you listen to as soon as
• 20:30
  Speaker 3: it comes out?
• 20:31
  Speaker 1: Oh, great question. I listen to This American Life pretty
• 20:34
  Speaker 1: regularly and almost immediately. I listen to Hyperfixed quite often.
• 20:39
  Speaker 1: I listen to Heavyweight. Heavyweight is an excellent, amazing podcast.
• 20:43
  Speaker 1: Love that one. And my guilty pleasure while driving is
• 20:46
  Speaker 1: If Books Could Kill because it makes me laugh and
• 20:49
  Speaker 1: doesn't require me to think too much.
• 20:52
  Speaker 3: Excellent.
• 20:53
  Speaker 1: Have it too.
• 20:54
  Speaker 3: The rest is history. And the Underworld podcast.
• 20:58
  Speaker 1: Nice.
• 20:59
  Speaker 2: Those are, yeah, those are my two go-tos. But everyone's
• 21:02
  Speaker 2: listening to the best podcast ever right now. And so
• 21:04
  Speaker 2: let's focus on our podcast and answer a Discord question
• 21:09
  Speaker 2: from Yarthfar the True. And we are continuing my tradition
• 21:14
  Speaker 2: of not remembering to get first names from Discord listeners
• 21:17
  Speaker 2: before we answer their question on the show.
• 21:19
  Speaker 1: I'm sure that's the name on the driver's license, Kelly.
• 21:22
  Speaker 3: Yarthvar the True.
• 21:24
  Speaker 1: Why would you assume otherwise?
• 21:26
  Speaker 3: My mistake. My mistake. Let's hear what True, Yarthvar has
• 21:31
  Speaker 3: to ask.
• 21:32
  Speaker 6: Hi, this is Mr. True, Yarthvar, middle name The, with
• 21:37
  Speaker 6: a question in the form of a statement, mainly for Kelly.
• 21:40
  Speaker 6: I would be interested in learning more about bacteria, or
• 21:43
  Speaker 6: maybe other life forms, that are evolving to digest plastic.
• 21:47
  Speaker 6: I think that I heard Katie Golden of Creature Feature
• 21:49
  Speaker 6: Podcast mention a study on larvae eating styrofoam, for example.
• 21:54
  Speaker 1: Thanks for the great question, Mr.
• 21:55
  Speaker 2: True.
• 21:59
  Speaker 3: Yeah, so this is a big problem.
• 22:01
  Speaker 2: Like the fact that there is all of this plastic
• 22:03
  Speaker 2: waste all over the world. This could be a huge
• 22:06
  Speaker 2: food source for animals that could figure out how to
• 22:10
  Speaker 2: eat it. And so to try to understand the scale
• 22:13
  Speaker 2: of plastics that we are putting in the universe, I
• 22:15
  Speaker 2: found one site that said that we produce 360.
• 22:19
  Speaker 3: Million tons of plastic waste each year.
• 22:22
  Speaker 2: And another that said we produce 450 million tons of
• 22:26
  Speaker 2: plastic waste each year. So we are producing hundreds of
• 22:29
  Speaker 2: millions of tons of plastic waste each year.
• 22:31
  Speaker 1: And I guess plastic waste is like plastic we produce
• 22:34
  Speaker 1: and then want to throw away because there's a lot
• 22:36
  Speaker 1: of plastic we produce that we keep and cherish forever.
• 22:38
  Speaker 3: That's right. That's right.
• 22:39
  Speaker 2: No, waste, I think, definitely implies this is stuff that
• 22:42
  Speaker 2: you have thrown either into the recycling bin or into
• 22:45
  Speaker 2: the trash, but you are.
• 22:46
  Speaker 3: Done with it.
• 22:47
  Speaker 1: And chemically, like, what is a plastic? I have this
• 22:50
  Speaker 1: vague notion that it's like You take oil and you
• 22:53
  Speaker 1: process it through chemistry and you get plastic. Is that
• 22:55
  Speaker 1: basically what's happening?
• 22:57
  Speaker 3: Yeah, that's basically what's happening.
• 22:58
  Speaker 2: But the important thing to note is that that oil
• 23:00
  Speaker 2: has a bunch of carbon in it. And a lot
• 23:03
  Speaker 2: of the like things that we eat have carbon in it.
• 23:06
  Speaker 1: I like carbon.
• 23:08
  Speaker 3: I love carbon.
• 23:09
  Speaker 5: Big fan.
• 23:09
  Speaker 1: There's crunchy bits when you've cooked something a little bit
• 23:12
  Speaker 1: too long, as Katrina calls the cancer ends. I love
• 23:16
  Speaker 1: the cancer ends of stuff.
• 23:17
  Speaker 2: Yeah, I love the cancer ends of stuff too. Just
• 23:20
  Speaker 2: try not to eat too many. You can enjoy them sometimes.
• 23:23
  Speaker 2: But if you can cut those carbon chains in different ways,
• 23:28
  Speaker 2: you can make different compounds.
• 23:30
  Speaker 3: And this is chemistry.
• 23:32
  Speaker 2: That's my best definition of chemistry there. So the question is,
• 23:38
  Speaker 2: can you take carbon chains in plastic and cut them
• 23:42
  Speaker 2: into ways that produce things that are edible?
• 23:45
  Speaker 5: I see.
• 23:46
  Speaker 2: And it appears that some bacteria, some fungi, and some worms.
• 23:52
  Speaker 3: have figured out how to do that.
• 23:54
  Speaker 2: And the first time we sort of recognized that this
• 23:56
  Speaker 2: was happening in nature that I could find was in 2016.
• 24:00
  Speaker 2: There's bacteria in a recycling plant in Japan that was
• 24:04
  Speaker 2: found breaking down the plastic. And in particular, the kind
• 24:08
  Speaker 2: of plastic we're talking about is PET. This is found
• 24:11
  Speaker 2: in a lot of water bottles, found in a lot
• 24:13
  Speaker 2: of different kinds of like jugs. It makes polyester. Your
• 24:16
  Speaker 2: clothes have a lot of this kind of plastic in it.
• 24:19
  Speaker 2: It's a very common plastic. And this bacteria was producing
• 24:23
  Speaker 2: an enzyme that has been named PETase.
• 24:26
  Speaker 1: Okay. And ASE is something we often refer to in
• 24:30
  Speaker 1: chemistry for like, it's an enzyme that helps catalyze something
• 24:34
  Speaker 1: or make some reaction happen.
• 24:35
  Speaker 2: So my first Google result, National Institutes of Health, is
• 24:38
  Speaker 2: apparently the reference. It says, enzymes are biological catalysts usually
• 24:42
  Speaker 2: made of proteins that speed up chemical reactions in living things.
• 24:46
  Speaker 7: Cool.
• 24:46
  Speaker 2: Cool.
• 24:46
  Speaker 1: And no surprise that it's a microbe that first does this.
• 24:49
  Speaker 1: Katrina is always saying microbes learn how to eat anything.
• 24:52
  Speaker 3: Yep, yep.
• 24:53
  Speaker 1: And we heard from your friend who's an expert in
• 24:55
  Speaker 1: the deep underwater vents that microbes are down there eating
• 24:59
  Speaker 1: crazy stuff.
• 24:59
  Speaker 2: Yep.
• 25:00
  Speaker 1: So thank you, microbes, for pioneering everything, basically.
• 25:03
  Speaker 2: And what we're going to get to is that we
• 25:05
  Speaker 2: are trying to figure out how to use this for
• 25:08
  Speaker 2: our own purposes to try to break down a lot
• 25:10
  Speaker 2: of the plastics. And so the bacteria that they discovered,
• 25:13
  Speaker 2: it looks like it actually has two reactions that it does.
• 25:17
  Speaker 2: Like the first one uses that PATase and then it
• 25:20
  Speaker 2: breaks those products down into two smaller carbon chains. One
• 25:25
  Speaker 2: is terephthalic acid and the other is ethylene glycol. And
• 25:30
  Speaker 2: what you need to know there are two things that
• 25:33
  Speaker 2: I think I'm getting correct here. One is that at
• 25:35
  Speaker 2: this stage, the bacteria can start eating those things and
• 25:38
  Speaker 2: using the carbon. And two, these are also ingredients that
• 25:42
  Speaker 2: we use to make more PET. So once this reaction
• 25:46
  Speaker 2: has happened, if you can collect the products that were
• 25:49
  Speaker 2: made by the bacteria, you can then start making new
• 25:53
  Speaker 2: plastic products, which could be very helpful in like recycling
• 25:57
  Speaker 2: plants and stuff.
• 25:58
  Speaker 1: So you're saying the microbes have this enzyme in them
• 26:02
  Speaker 1: which breaks down the plastic into stuff that their metabolism
• 26:06
  Speaker 1: knows how to ingest.
• 26:08
  Speaker 7: Yep.
• 26:08
  Speaker 1: And also produces stuff that we can use to make, yay,
• 26:11
  Speaker 1: more plastic. That's amazing. And are they making this PETA?
• 26:15
  Speaker 1: So did they like find it or is it occurring
• 26:17
  Speaker 1: naturally or like is it expressed in their genome?
• 26:20
  Speaker 2: So I think the best guess is that it evolved
• 26:23
  Speaker 2: from ferulic acid esterases.
• 26:26
  Speaker 3: Who cares?
• 26:27
  Speaker 2: The answer, what you want to know is that this
• 26:30
  Speaker 2: is something that they used to break down plant walls.
• 26:33
  Speaker 2: So this was something that they were using to get
• 26:35
  Speaker 2: into plants. And with a little bit of tinkering, it
• 26:38
  Speaker 2: can be used to start breaking down plastic. So this
• 26:41
  Speaker 2: isn't something that the bacteria had to like.
• 26:43
  Speaker 3: You know, evolve out of nothing.
• 26:45
  Speaker 2: This is something that they already had that it turns
• 26:48
  Speaker 2: out if you change it a little bit, you know,
• 26:50
  Speaker 2: for example, you've got, you know, billions of bacteria, maybe trillions,
• 26:54
  Speaker 2: quadrillions in a recycling plant. You know, some of them
• 26:57
  Speaker 2: had a mutation in this thing that's breaking down plant walls.
• 27:00
  Speaker 2: And then it actually turned out that that helped them
• 27:01
  Speaker 2: break down the plastics. And now they've got this like
• 27:04
  Speaker 2: headstart on a new food source.
• 27:05
  Speaker 1: Yeah, that's a great example of evolution, right? You have
• 27:08
  Speaker 1: something which does a different job And you randomly evolve
• 27:11
  Speaker 1: it to do something new, which unlocks an enormous new
• 27:14
  Speaker 1: food source, since you can see why that would help
• 27:17
  Speaker 1: those populations survive. I guess I'm surprised it didn't happen faster.
• 27:21
  Speaker 7: Yeah, right.
• 27:22
  Speaker 2: Well, and it's actually not happening super efficiently yet. Like
• 27:26
  Speaker 2: another thing to understand for evolution is that like, you know,
• 27:29
  Speaker 2: if a mutation happens and suddenly something that was breaking
• 27:31
  Speaker 2: down plant wall is now helping to break down plastic,
• 27:34
  Speaker 2: you don't necessarily get the most efficient version of that enzyme, right?
• 27:38
  Speaker 7: Right.
• 27:38
  Speaker 2: For that enzyme to get better over time, you need
• 27:40
  Speaker 2: to have... you know, for example, more random mutations that
• 27:43
  Speaker 2: need to get like tried out as they change the
• 27:45
  Speaker 2: way the enzyme works. And then the individuals that have
• 27:48
  Speaker 2: the slightly more efficient enzyme are the ones that have
• 27:50
  Speaker 2: more babies. And like, it's a very long, slow process
• 27:53
  Speaker 2: that depends often. on random things happening along the way.
• 27:57
  Speaker 2: And so there are some labs that are specifically taking
• 28:00
  Speaker 2: the code for these enzymes and are mutating it to
• 28:04
  Speaker 2: much more quickly move through all of the different ways,
• 28:07
  Speaker 2: all of the different shapes that this enzyme could take
• 28:09
  Speaker 2: and see if any of them are actually much more
• 28:12
  Speaker 2: efficient if you essentially speed up evolution in the lab.
• 28:15
  Speaker 6: Uh-oh.
• 28:16
  Speaker 1: But then what if you release these things and they
• 28:18
  Speaker 1: dissolve all the plastic in the world in five seconds?
• 28:21
  Speaker 3: Yeah, right, so that's something that people joke about a lot.
• 28:24
  Speaker 2: I mean, they're still gonna have to compete with all
• 28:26
  Speaker 2: the other bacteria on the planet. They will have this
• 28:29
  Speaker 2: massive new food source. Maybe this is something we need
• 28:31
  Speaker 2: to worry about. I didn't find a lot of people
• 28:34
  Speaker 2: panicking about it.
• 28:35
  Speaker 3: What do you think? How much would you worry? How
• 28:37
  Speaker 3: much would Katrina worry about this? That's what I need
• 28:39
  Speaker 3: to know.
• 28:40
  Speaker 1: I mean, I don't think I'm even aware of the
• 28:42
  Speaker 1: role the plastics play in my life. Like, imagine all
• 28:45
  Speaker 1: plastics on the planet were instantly deleted. Like, I guess
• 28:48
  Speaker 1: my glasses would fall apart. Same.
• 28:51
  Speaker 3: Our microphones.
• 28:51
  Speaker 1: And my computer probably would fall apart. And probably my
• 28:55
  Speaker 1: car wouldn't work.
• 28:57
  Speaker 3: Yeah, we'd be pwned.
• 29:01
  Speaker 1: I don't think we're ready for that.
• 29:02
  Speaker 5: No.
• 29:03
  Speaker 1: Be careful, biologists.
• 29:05
  Speaker 3: Yeah, we're right.
• 29:06
  Speaker 1: It's not just physicists who can destroy the world.
• 29:09
  Speaker 2: Well, so we will get to, in just a second,
• 29:11
  Speaker 2: we'll get to the ways that people are trying to
• 29:12
  Speaker 2: be a little bit careful about this.
• 29:14
  Speaker 1: Okay.
• 29:14
  Speaker 2: But I just wanted to note real quick that there's
• 29:16
  Speaker 2: a company called, I think, Carbios. And they are essentially,
• 29:20
  Speaker 2: they're the ones that are, like, doing this, you know,
• 29:23
  Speaker 2: evolution in the lab thing to try to find more
• 29:24
  Speaker 2: efficient enzymes. And they're trying to break down pre-existing plastics.
• 29:28
  Speaker 2: And they have some, like, deals with companies that make
• 29:31
  Speaker 2: makeup and makeup containers and And they are trying to
• 29:34
  Speaker 2: upcycle it back into more plastics, which is kind of cool.
• 29:38
  Speaker 2: So a lot of stuff would be staying out of
• 29:39
  Speaker 2: the land. or like coming out of the recycling plants
• 29:42
  Speaker 2: more quickly.
• 29:43
  Speaker 3: So, okay.
• 29:43
  Speaker 2: But so then the question is, If you have, for example,
• 29:47
  Speaker 2: done something in the lab and genetically modified an organism, like,
• 29:50
  Speaker 2: for example, maybe you decide that these enzymes, it would
• 29:53
  Speaker 2: be better if they were made by E. coli than
• 29:55
  Speaker 2: if they were made by the bacteria we first found
• 29:57
  Speaker 2: them in, because it's just easier to manipulate E.
• 29:59
  Speaker 7: Coli.
• 29:59
  Speaker 3: So you put the genes for this enzyme in E. coli.
• 30:02
  Speaker 2: You probably don't want to release that into the environment
• 30:05
  Speaker 2: because people are very uncomfortable about genetically modified organisms.
• 30:09
  Speaker 3: And if you're the.
• 30:10
  Speaker 2: Person that makes it so that all the plastic gets digested,
• 30:13
  Speaker 2: you're not going to have a lot of friends. And
• 30:16
  Speaker 2: so what they're doing is they are working on ways to,
• 30:19
  Speaker 2: for example, make E.
• 30:20
  Speaker 3: Coli.
• 30:21
  Speaker 2: And by they, I mean like different groups, not necessarily
• 30:24
  Speaker 2: the carbios group. But anyway, they're working on trying to
• 30:26
  Speaker 2: get E. coli or other bacteria to produce enzymes in
• 30:30
  Speaker 2: large quantities in the lab. And then they release those
• 30:34
  Speaker 2: enzymes into places where plastic needs to get broken down.
• 30:37
  Speaker 2: So they're cutting the bacteria out, but they're releasing the enzymes.
• 30:41
  Speaker 2: And like your laundry detergent has enzymes in it.
• 30:45
  Speaker 1: That's cold-blooded, man.
• 30:46
  Speaker 3: Why is that cold-blooded?
• 30:48
  Speaker 1: You're getting the bacteria to produce this enzyme. They evolved
• 30:52
  Speaker 1: so they can eat, and you're using it to break
• 30:55
  Speaker 1: down the plastics without letting the bacteria have lunch. That
• 30:59
  Speaker 1: seems cold.
• 31:00
  Speaker 2: They're probably feeding the bacteria because they want them to
• 31:03
  Speaker 2: keep surviving and making this enzyme. I guess it depends on,
• 31:06
  Speaker 2: do you have to kill the bacteria to get the enzyme,
• 31:08
  Speaker 2: or can you make the bacteria excrete the.
• 31:10
  Speaker 3: Enzyme in some way? We should have invited Katrina today.
• 31:13
  Speaker 2: Yeah.
• 31:14
  Speaker 1: The bacteria should unionize, man. They own the means of
• 31:16
  Speaker 1: production here, right? They have nothing to lose but their chains.
• 31:20
  Speaker 3: That's right. That's right. Getting political.
• 31:23
  Speaker 1: But I guess I'm a little confused. I would have
• 31:24
  Speaker 1: thought this is something you wanted to introduce into a
• 31:27
  Speaker 1: landfill so that the plastic in the landfill degrades more quickly,
• 31:31
  Speaker 1: turns back into soil, all that good stuff. But it
• 31:34
  Speaker 1: sounds like you're saying we want to collect plastic out
• 31:38
  Speaker 1: of this waste stream and and isolate it, and then
• 31:41
  Speaker 1: break it down so that we can reuse it to
• 31:43
  Speaker 1: make more plastic and stuff. Isn't there a big energy
• 31:46
  Speaker 1: cost to recycling and taking these things out of the
• 31:49
  Speaker 1: waste stream? Is that really worth it?
• 31:50
  Speaker 2: So it depends on who you're talking to, what the
• 31:52
  Speaker 2: goals are. So there are some groups that would like
• 31:55
  Speaker 2: to take plastic that's already going to a recycling plant,
• 31:58
  Speaker 2: for example, and use that to make new plastic stuff.
• 32:02
  Speaker 2: And so essentially just make the recycling process a lot simpler.
• 32:06
  Speaker 4: Mm-hmm.
• 32:07
  Speaker 3: There are other folks who are, for.
• 32:08
  Speaker 2: Example, taking plastics maybe from a recycling plant and then
• 32:12
  Speaker 2: they're trying to turn it into things like vanillin, which
• 32:16
  Speaker 2: is the chemical that gives vanilla its taste. And apparently
• 32:20
  Speaker 2: you can make that by breaking down plastics and then
• 32:22
  Speaker 2: just tinkering with it a little bit.
• 32:24
  Speaker 1: What? You can make vanilla flavor from plastics?
• 32:27
  Speaker 3: Oh my gosh.
• 32:28
  Speaker 5: Yep, yep.
• 32:28
  Speaker 2: Apparently we already make vanilla flavor from petroleum stuff. And
• 32:33
  Speaker 2: so the scientist that was you know, answering questions was
• 32:36
  Speaker 2: a little bit defensive, presumably because this has been asked
• 32:39
  Speaker 2: of them many times. But if you get synthetic vanilla flavoring,
• 32:43
  Speaker 2: it might have a bit of a petroleum background.
• 32:46
  Speaker 1: All those folks out there who defend vanilla ice cream
• 32:49
  Speaker 1: is like a legitimate flavor and a competitor to actual
• 32:52
  Speaker 1: chocolate ice cream. Like, yeah, I don't think so.
• 32:56
  Speaker 3: Yeah, I agree. They're bad people.
• 32:57
  Speaker 1: I was trying to be choice in my words, but
• 33:02
  Speaker 1: That's what you're here for, Kelly. Unleash it on everyone.
• 33:05
  Speaker 3: That's right. That's right. I was obviously joking.
• 33:08
  Speaker 2: But then there's other groups that are, for example, trying
• 33:11
  Speaker 2: to put these enzymes into bacteria that can survive in
• 33:15
  Speaker 2: saltwater environments so that then you could release those organisms like,
• 33:19
  Speaker 2: I don't know, into the giant.
• 33:21
  Speaker 3: Trash patch in the ocean.
• 33:23
  Speaker 2: I actually think there's many giant trash patches because we're
• 33:26
  Speaker 2: a great species.
• 33:27
  Speaker 1: We're wonderful.
• 33:28
  Speaker 3: We're at the best. And you could release them.
• 33:30
  Speaker 2: Into the ocean and then let the bacteria start breaking
• 33:32
  Speaker 2: down those trash patches. So there's some people who are
• 33:35
  Speaker 2: talking about wanting to release this stuff into the environment.
• 33:39
  Speaker 2: I think a lot of people have very complicated feelings
• 33:41
  Speaker 2: about genetically modified organisms. And so I think there'd be
• 33:44
  Speaker 2: a lot of people you'd have to convince that that
• 33:46
  Speaker 2: was a good idea if you wanted to go forward
• 33:47
  Speaker 2: with that.
• 33:48
  Speaker 3: But Mr.
• 33:49
  Speaker 2: True wanted to know if there were other organisms that
• 33:53
  Speaker 2: do this.
• 33:53
  Speaker 3: It looks like.
• 33:54
  Speaker 2: Fungi do it as well. They have an enzyme that
• 33:57
  Speaker 2: breaks genes. cuten down and this is a part of
• 34:00
  Speaker 2: plants again and so fungi here again have a thing
• 34:04
  Speaker 2: that they were using to break down plants but it
• 34:07
  Speaker 2: turns out with a little bit of tinkering it can
• 34:09
  Speaker 2: break down plastic and so some fungus can do this
• 34:12
  Speaker 2: as well And some wax worms appear to be able
• 34:15
  Speaker 2: to do this. So there was a scientist who had
• 34:19
  Speaker 2: some beehives and these worms are really bad for beehives.
• 34:22
  Speaker 2: And she started taking them out of the beehive and
• 34:25
  Speaker 2: then she put them in a plastic bag and she
• 34:26
  Speaker 2: noticed that not only were they eating their way out
• 34:28
  Speaker 2: of the bag, but anywhere their saliva had touched, the
• 34:31
  Speaker 2: bag started to degrade. And so I think the follow-up
• 34:34
  Speaker 2: work suggested that to some extent, this is stuff being
• 34:38
  Speaker 2: produced by their microbiome. So it goes back to bacteria again.
• 34:43
  Speaker 2: But there are some worms that seem to be able
• 34:45
  Speaker 2: to some like grubby things that seem to be able
• 34:47
  Speaker 2: to live on plastic as well.
• 34:49
  Speaker 1: Wow. Fascinating.
• 34:51
  Speaker 7: Yeah.
• 34:51
  Speaker 2: So anyway, maybe we will be able to harness biology
• 34:54
  Speaker 2: to fix a massive problem that we have caused. But
• 34:58
  Speaker 2: we're going to have to wait and see.
• 35:00
  Speaker 1: It does feel like biology has these tools, or at
• 35:03
  Speaker 1: least it's better at adapting. I mean, the whole process
• 35:06
  Speaker 1: of evolution is just such an incredibly parallel way to
• 35:10
  Speaker 1: search for new techniques, right? You have quadrillions of bacteria
• 35:14
  Speaker 1: constantly trying new things and evolving in new ways. And
• 35:18
  Speaker 1: the chances that we could find a new solution faster
• 35:21
  Speaker 1: than a zillion bacteria all in parallel seems ridiculous. But
• 35:26
  Speaker 1: it's cool that you then isolate it and fine-tune it.
• 35:28
  Speaker 1: and then are hopefully careful about how you implement it.
• 35:32
  Speaker 2: Yep, we can be inspired by biology in a lot
• 35:34
  Speaker 2: of different ways. All right, let's see what Mr. True
• 35:36
  Speaker 2: has to say, or Miss True. I didn't realize that
• 35:39
  Speaker 2: Yarthvar could also be a lady listener. So anyway, MX True,
• 35:48
  Speaker 2: what do you have to say?
• 35:50
  Speaker 6: Hi, Yarthvar again. Thanks for the informative and complete answer.
• 35:55
  Speaker 6: I don't have any follow-up questions, but I do have
• 35:57
  Speaker 6: a couple of comments. First, I echo your concern with
• 36:01
  Speaker 6: releasing these organisms into the environment. I would hope that
• 36:04
  Speaker 6: we only take such a bold step after conducting our
• 36:06
  Speaker 6: due diligence with the utmost of rigor. Second, even though
• 36:10
  Speaker 6: there is a grain of hope that these organisms might
• 36:12
  Speaker 6: break down some of our plastic waste, I think that
• 36:15
  Speaker 6: we still need to limit the amount of plastic that
• 36:17
  Speaker 6: we allow into the environment. And finally, Yartvar actually is
• 36:22
  Speaker 6: my name, though in a different language. It's Edward in
• 36:25
  Speaker 6: Old Norse, the medieval language of my Scandinavian ancestors. It
• 36:29
  Speaker 6: might sound funny to the modern ear, but I prefer
• 36:32
  Speaker 6: it to my other ancestral option. Old English is eidwyrd
• 36:35
  Speaker 6: or eithwyrd. Anyway, thanks again. I appreciate you both and
• 36:40
  Speaker 6: wish good health and happiness to all.
• 37:01
  Speaker 4: All right.
• 37:02
  Speaker 3: And we're back. And our last question of the day
• 37:04
  Speaker 3: is from Sebastian.
• 37:05
  Speaker 2: And Daniel hinted earlier in the show that this would
• 37:08
  Speaker 2: have something to do about the speed of light and time.
• 37:13
  Speaker 2: Let's go ahead and hear the question.
• 37:14
  Speaker 5: Hi. I've been trying to wrap my head around the
• 37:17
  Speaker 5: block universe for a while. From my understanding, you always
• 37:20
  Speaker 5: see a different slice of space-time depending on your speed
• 37:23
  Speaker 5: and directions. So if you and I are traveling in
• 37:26
  Speaker 5: different directions at high speeds, we would have a different
• 37:29
  Speaker 5: view on what is now. What does that say about
• 37:32
  Speaker 5: the future being unwritten? Or is the future already determined
• 37:35
  Speaker 5: in this theory? If so, what are arguments for or
• 37:39
  Speaker 5: against the block universe? Thank you. Love the show.
• 37:43
  Speaker 2: I remember that you and I once had an episode
• 37:47
  Speaker 2: where we were checking out like sci-fi books and movies
• 37:51
  Speaker 2: and how they dealt with like space and time and
• 37:54
  Speaker 2: time travel. And at the end I was like, well,
• 37:57
  Speaker 2: this was a Daniel is a wet blanket episode, which
• 38:00
  Speaker 2: is out of the ordinary, but you know, very refreshing.
• 38:04
  Speaker 2: And so I'm looking forward to what you have to
• 38:06
  Speaker 2: say here.
• 38:07
  Speaker 1: This is a really fun question because it gets the
• 38:11
  Speaker 1: heart of like, what does it mean that special relativity
• 38:14
  Speaker 1: breaks our ideas of now and And do we still
• 38:18
  Speaker 1: have free will, or is the future somehow determined because
• 38:21
  Speaker 1: maybe somebody else can see more of it than we
• 38:22
  Speaker 1: can or something? So let's dig into it first and
• 38:26
  Speaker 1: remind ourselves what exactly special relativity says and doesn't say
• 38:30
  Speaker 1: about time and about now and the future. So special
• 38:34
  Speaker 1: relativity says that light always moves at the speed of light,
• 38:38
  Speaker 1: regardless of the observer or your velocity, as long as
• 38:42
  Speaker 1: it's nearby, in a little flat neighborhood. And that breaks
• 38:46
  Speaker 1: our sense of whether things have to happen at the
• 38:49
  Speaker 1: same time or not. And the classic example is Kelly's
• 38:53
  Speaker 1: on a train and she has two flashlights and she
• 38:56
  Speaker 1: shines a flashlight forward and a flashlight backwards. And because
• 39:00
  Speaker 1: she's standing in the center of the train car, she
• 39:02
  Speaker 1: sees the light beams hitting the front and the back
• 39:04
  Speaker 1: of the train at the same time, right? Makes perfect sense.
• 39:08
  Speaker 1: They go the same distance and the same amount of time.
• 39:10
  Speaker 1: Of course they hit the front and the back at
• 39:12
  Speaker 1: the same time. But Zach is not in the train
• 39:15
  Speaker 1: with Kelly. He's on the ground. He's eating his breakfast
• 39:18
  Speaker 1: cereal or whatever. He's watching Kelly on the train do
• 39:21
  Speaker 1: this experiment. What does he see? Well, he sees the
• 39:25
  Speaker 1: back of the train moving towards where the light was
• 39:28
  Speaker 1: emitted and the front of the train moving away from
• 39:31
  Speaker 1: where the light was emitted. And because the light moves
• 39:34
  Speaker 1: at the same speed relative to Zach, he sees the
• 39:38
  Speaker 1: light hit the back of the train first and the
• 39:40
  Speaker 1: front of the train later. That would not be true
• 39:43
  Speaker 1: for sound waves, for example. because sound waves don't move
• 39:46
  Speaker 1: at the same speed for all observers. They move at
• 39:49
  Speaker 1: the same speed relative to their medium. So for example,
• 39:52
  Speaker 1: if Kelly shouted instead of using light beams, then Zach
• 39:55
  Speaker 1: would see the shout moving slower going backwards and faster
• 39:59
  Speaker 1: going forwards, because it's moving at the same speed relative
• 40:02
  Speaker 1: to the air, which is moving relative to him. But
• 40:05
  Speaker 1: light doesn't work that way. Light moves at the speed
• 40:08
  Speaker 1: of light no matter what. And so he sees it
• 40:11
  Speaker 1: hit the back of the train before he sees it
• 40:12
  Speaker 1: hit the front of the train. So Kelly says these
• 40:15
  Speaker 1: two things happen at the same time, and Zach says, no,
• 40:19
  Speaker 1: they don't. And somebody else going the other direction sees
• 40:23
  Speaker 1: the opposite, sees it hit the front of the train
• 40:25
  Speaker 1: before the back of the train. What's going on? Is
• 40:29
  Speaker 1: the universe broken? No, what's going on is that special
• 40:33
  Speaker 1: relativity tells us that there is no global now. It's
• 40:36
  Speaker 1: not like there's a one clock for the whole universe.
• 40:39
  Speaker 1: And the universe ticks forward one step at a time
• 40:42
  Speaker 1: and everybody can agree on what time we're at and
• 40:45
  Speaker 1: what's happening at the same time. Instead, like the listener asked,
• 40:49
  Speaker 1: we all see like a different slice of space-time depending
• 40:52
  Speaker 1: on our speed and our direction. So there's as many
• 40:55
  Speaker 1: moments of now as there are locations in the universe
• 40:59
  Speaker 1: and velocities in the universe. So if you're not at
• 41:02
  Speaker 1: the same location and you don't have the same velocity,
• 41:05
  Speaker 1: then you see time flowing in a different way and
• 41:07
  Speaker 1: you can even disagree about the order in which stuff happens.
• 41:12
  Speaker 2: And so are we like mostly talking about little things like,
• 41:18
  Speaker 2: you know, you're a second or two off about when
• 41:20
  Speaker 2: the light hits the train or could, are we talking
• 41:23
  Speaker 2: about you could be a year or two different? I
• 41:27
  Speaker 2: guess it depends on how far the thing has traveled.
• 41:30
  Speaker 2: Like if you're looking at how far light traveled across
• 41:34
  Speaker 2: the universe, And you got different results.
• 41:37
  Speaker 3: Yeah. How big of a time? I'm very confused.
• 41:42
  Speaker 1: It can be a big difference. You know, if somebody
• 41:44
  Speaker 1: gets on a spaceship and they're moving 99% of the
• 41:46
  Speaker 1: speed of light away from us for a long time,
• 41:49
  Speaker 1: then their clock can differ by years from our clocks.
• 41:52
  Speaker 1: So it can be a huge difference. And that's actually
• 41:55
  Speaker 1: nice if you're going to travel to like Alpha Centauri,
• 41:57
  Speaker 1: you know, then it might take a long time on
• 42:00
  Speaker 1: Earth clocks for you to get there, but it doesn't
• 42:02
  Speaker 1: take that much time on your clock on the ship.
• 42:05
  Speaker 1: which is nice because you're the one on the ship.
• 42:07
  Speaker 1: So it can be a big deal for sure. And
• 42:10
  Speaker 1: for people who wonder like, hold on a second, how
• 42:12
  Speaker 1: can the order of events be changed? You know, like
• 42:16
  Speaker 1: if somebody shoots an arrow at an apple, can somebody
• 42:19
  Speaker 1: else like see the apple get hit before they shoot
• 42:22
  Speaker 1: the arrow? Does this break causality? And the answer is no,
• 42:25
  Speaker 1: there are limits. Special relativity can reorder events, but only
• 42:29
  Speaker 1: ones that are causally disconnected.
• 42:32
  Speaker 2: I think we're living in a simulation by somebody who
• 42:34
  Speaker 2: wrote a fictional world that has kind of crazy rules,
• 42:36
  Speaker 2: but we have to follow them. And this just is
• 42:40
  Speaker 2: very counterintuitive.
• 42:41
  Speaker 1: Yeah. Events that are close enough in space and time
• 42:44
  Speaker 1: where light can move between them are causally connected because
• 42:48
  Speaker 1: you can like send a message from one to the other.
• 42:51
  Speaker 1: And those events you cannot reorder using special relativity. Only
• 42:55
  Speaker 1: things that are causally disconnected where they're far enough apart
• 42:58
  Speaker 1: that light can't go between the events are Those things,
• 43:01
  Speaker 1: you can't send any message from one event to the other.
• 43:03
  Speaker 1: So those kinds of events can be reordered based on
• 43:07
  Speaker 1: your velocity. All right. So what does that say about
• 43:11
  Speaker 1: the flow of time, right? Are different people seeing into
• 43:14
  Speaker 1: the future or different futures? Like definitely what I consider
• 43:18
  Speaker 1: to be now is different from what you consider to
• 43:21
  Speaker 1: be now. And it's tempting to imagine that like, you know,
• 43:25
  Speaker 1: Zach versus Kelly are seeing different slices of the future
• 43:29
  Speaker 1: and that what they're doing is just revealing slices of
• 43:32
  Speaker 1: an already determined future. And your speed through the universe
• 43:36
  Speaker 1: is just determining like which slice of the preexisting space-time
• 43:40
  Speaker 1: block you're getting. It's tempting. And that's the theory of
• 43:44
  Speaker 1: the block universe that says that the past, the present,
• 43:47
  Speaker 1: and the future all exist simultaneously within some like four-dimensional
• 43:52
  Speaker 1: space-time structure. What do we mean by four dimensions? Well,
• 43:56
  Speaker 1: you know what we mean by three dimensions of space
• 43:58
  Speaker 1: and time. You have X, Y, and Z, three directions
• 44:01
  Speaker 1: you can move in space. Now, if you imagine that
• 44:03
  Speaker 1: to be a 4D structure, that just means that through time,
• 44:07
  Speaker 1: stuff is happening in space. And so you can't stack
• 44:11
  Speaker 1: up 3D spaces on top of each other in a
• 44:14
  Speaker 1: 3D space. You have to imagine it changing as you
• 44:17
  Speaker 1: move the arrow of time. And so in this block
• 44:20
  Speaker 1: universe theory, the past, the present, the future are are
• 44:23
  Speaker 1: already fixed, right? Like the future exists as much as
• 44:27
  Speaker 1: the past exists and the present exists. The way like
• 44:30
  Speaker 1: when you go to watch the Spider-Man movie, the ending
• 44:34
  Speaker 1: is already determined. You're just happening to watch a certain
• 44:36
  Speaker 1: frame of it. You haven't seen the ending, but the past,
• 44:39
  Speaker 1: the present, and the future in the movie are already fixed.
• 44:42
  Speaker 1: So the block universe theory says that that's our universe,
• 44:45
  Speaker 1: that the past, the present, and the future are already
• 44:48
  Speaker 1: set and we're just like, we're having a certain slice
• 44:50
  Speaker 1: through it And the special relativity version of that is
• 44:53
  Speaker 1: the slice you see of the universe depends on your
• 44:57
  Speaker 1: location and your velocity.
• 44:58
  Speaker 3: So this is a no free will theory. Is that right?
• 45:02
  Speaker 1: Exactly. It's a no free will kind of a theory.
• 45:05
  Speaker 1: And so Sebastian's question is, does special relativity imply the
• 45:09
  Speaker 1: block universe? And I would say no. It's compatible with
• 45:12
  Speaker 1: the block universe. The idea that special relativity gives you
• 45:14
  Speaker 1: a different slice of that block universe. But as you say,
• 45:18
  Speaker 1: the block universe is a deterministic theory. It says... The
• 45:21
  Speaker 1: future is already set, but special relativity doesn't require that.
• 45:25
  Speaker 1: Special relativity says that the past, the present, and the
• 45:28
  Speaker 1: future are different for everybody. Like we disagree about what
• 45:32
  Speaker 1: now means, but it doesn't mean that you don't have
• 45:35
  Speaker 1: choices to make. You can still have a universe where
• 45:38
  Speaker 1: the laws are probabilistic, for example, like quantum mechanical. where
• 45:42
  Speaker 1: the outcome of an experiment is determined by random probability
• 45:46
  Speaker 1: and not fully determined by the past. So the past
• 45:50
  Speaker 1: might determine the probability of something happening, but not the
• 45:53
  Speaker 1: actual outcome. And so the past doesn't determine the future
• 45:57
  Speaker 1: in our universe, for example, because we think the universe
• 45:59
  Speaker 1: is quantum mechanical. And so the universe is not fully deterministic.
• 46:04
  Speaker 1: And so it's not consistent with a block universe. So
• 46:07
  Speaker 1: special relativity just means that now is local. It doesn't
• 46:10
  Speaker 1: mean that the future is determined. You know, it says
• 46:14
  Speaker 1: something weirder. It says that you don't get a unique,
• 46:17
  Speaker 1: universal answer to the question, what is happening everywhere right now?
• 46:22
  Speaker 1: But it doesn't say that the future is determined. And
• 46:25
  Speaker 1: remember those cones we talked about, like where you can
• 46:29
  Speaker 1: influence and things that are causally linked to you or
• 46:31
  Speaker 1: not causally linked to you. Special relativity doesn't say that
• 46:35
  Speaker 1: like Kelly has seen my future because she's moving at
• 46:38
  Speaker 1: a different velocity or whatever. You know, you can rearrange
• 46:42
  Speaker 1: certain events, but only things that are not causally linked together.
• 46:46
  Speaker 1: So it's not like Kelly can see what I've decided
• 46:49
  Speaker 1: to do, right? Kelly can't rearrange the future in a
• 46:52
  Speaker 1: way that changes my chain of causality.
• 46:55
  Speaker 3: No, that's too bad.
• 46:55
  Speaker 1: Does that make sense?
• 46:56
  Speaker 3: Yeah, it makes sense, but it's disappointing.
• 46:59
  Speaker 1: I mean, you can influence the decisions I make, and
• 47:01
  Speaker 1: you certainly do. Make a good argument, make a funny joke.
• 47:05
  Speaker 1: You're definitely going to influence the path of Daniel's life,
• 47:07
  Speaker 1: but not by getting on a train at half the
• 47:09
  Speaker 1: speed of light.
• 47:10
  Speaker 3: Okay, got it.
• 47:11
  Speaker 1: All right, and so if you didn't already predict that answer, Sebastian,
• 47:14
  Speaker 1: in your block universe, then I'm curious how our answer
• 47:18
  Speaker 1: determines your response.
• 47:20
  Speaker 5: Hi, Daniel and Kelly. I think that clears it up,
• 47:23
  Speaker 5: so Free World still has a chance.
• 47:26
  Speaker 6: All right.
• 47:27
  Speaker 2: Thank you, everybody, for sharing your amazing questions with us today.
• 47:30
  Speaker 2: As a unfortunate reminder, Kelly is still on an email
• 47:34
  Speaker 2: hiatus and probably will be till 2027 because I have
• 47:37
  Speaker 2: about six months of amazing questions from you all to
• 47:40
  Speaker 2: work from still. So hold on to your great questions.
• 47:43
  Speaker 2: I still am going to want them at some point,
• 47:45
  Speaker 2: but I'm working through the stack as we go.
• 47:47
  Speaker 1: All right. Thanks, everybody. We really love hearing from you,
• 47:50
  Speaker 1: hearing about your curiosity, hearing your questions, and we love
• 47:53
  Speaker 1: being a part of your journey of curiosity. Thanks so
• 47:57
  Speaker 1: much for taking us along for the ride.
• 47:58
  Speaker 3: Thanks for listening.
• 48:06
  Speaker 1: Thanks everybody for listening. Please go and do us a
• 48:08
  Speaker 1: favor and rate the show on whatever podcast app you're using.
• 48:12
  Speaker 1: It really helps people find us.
• 48:14
  Speaker 2: Daniel and Kelly's Extraordinary Universe is edited by the amazing
• 48:18
  Speaker 2: Matt Kesselman.
• 48:19
  Speaker 1: He really is a wizard. You can also find us
• 48:22
  Speaker 1: online on Blue Sky, Instagram, and X, D & K Universe.
• 48:27
  Speaker 1: Come engage with us.
• 48:29
  Speaker 2: You can email us at questions at danielandkelly.org. We really
• 48:33
  Speaker 2: do want to hear from you.
• 48:34
  Speaker 1: And you can find our website, www.danielandkelly.org, where you'll also
• 48:39
  Speaker 1: find an invitation to join our Discord, where everybody comes
• 48:43
  Speaker 1: and talks about the amazing universe.
• 48:45
  Speaker 2: And we also have the most amazing moderators. This is
• 48:49
  Speaker 2: an iHeart podcast.
• 48:51
  Speaker 3: Thanks for joining us.