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

Episode Date: September 24, 2026

Daniel and Kelly answer listener questions about special relativity, organisms that eat plastic, and whether the future is already determined.See omnystudio.com/listener for privacy information.

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Bruce Lee's daughter, Brandon Lee's sister, and my friend Shannon Lee. Back to your initial point of stewarding my father's legacy and giving my energy. to that. You're lending your life to stewarding somebody else's life. Listen to Who's With Me with me with W. Kmartbell on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. You're not incurable. You're not broken. You're having a normal human experience, and we have a solution for that.

And that solution is our podcast, free therapy. I'm Ben. And I'm Kevin. And every week, we talk to leading therapists in the country about relationships, work, family dynamics, and all of life's headaches. If you're trying to get rid of anxiety, you're actually fueling more anxiety. So listen to free therapy because therapy is expensive. But our podcast is free! Listen to free therapy with Ben and Kevin on the IHeartRadio app, Apple Podcasts, or wherever you get your podcast. Photons slow down when they approach space with a curve.

Is that real or just some illusion we observe? If plastic waste were edible, humans would all eat like kings. Can any species fill this niche? plastic eating things? If you and I disagree on what's now in the space time sea, does tomorrow already exist? Or is it still up to me? Whatever questions keep you up at night, Daniel and Kelly's answers will make it right. Welcome to Daniel and Kelly's extraordinary universe of listener curiosity.

Episode number 51. 51. We do. I don't know that it adds anything, but I enjoy it. I just enjoy hearing the big number. Like, wow, think about all the questions we've answered. Yeah, I mean, that's like 150 questions from listeners that we've, like, it's 150 things that have been shared with us. That's exciting.

Exactly. Well, hello, everyone. I'm Daniel Whiteson. I'm a particle physicist and I write books about aliens and the nature of science. And I'm Kelly Weiner-Smith. I study parasites and space and I'm interested in medical history this week. Not that we're talking about that today, but that's what's on my mind. Well, speaking of interest in the Wiener Smith household, I have a question for you, Kelly.

Oh, go for it. I hope it's about my goats. I'll make it about your goats. All right, so my question for you is, have your husband or your goats considered starting their own podcast? That is such a great question. You know, my goats have a strong desire to be heard. And the listeners want to hear from your goats. So there's a built-in audience.

We've had requests. Yeah, but I don't know that they're going to want to hear that more than once. Because they all have very distinct voices, which I think is interesting. I can hear one of them call and I'm like, oh, Leah's head is stuck in the fence again. Like, I just, I know them by their voices. But I don't think there's a big audience for that. However, my amazing husband, he's really into AI. Every morning we have coffee together and it's pretty much 30.

solid minutes of Zach AIing at me. And he is always reading about the newest things that's going on, the new math problems that's been solved, thinking about what this means for the future of humanity. Cool. Cool. And it turns out his brother, Marty Weiner, also

thinks about AI a lot. And so does Chris Slow, who's the current chief technical officer at Reddit. And Zach's brother, Marty, would probably want you to know that he's not just Zach's brother. He also was the chief technical officer at Reddit. and was one of the early engineers over at Pinterest.

He's like a, he's a big Silicon Valley dude. But anyway, they have a podcast about AI called Last Humans in the Loop. And I think they've got like five or six episodes. They've just started. And it is a fascinating look at AI. You too can hear Zach Weiner Smith talk about AI. So if you are not satisfied just hearing Kelly throw shade at Zach, you can also hear Zach throw shade at Kelly.

Get more Weiner Smith in your ear. There you go. Yes, I highly recommend it. And they do video, so you can see all of them responding in real time. Marty had this really great bit where you can now download voices of some actors. And he had, I think it was he downloaded the voice of Kermit the Frog reading a particularly violent scene in The Odyssey and he did it with a puppet at the same time on the show. Anyway, most of it is serious, but that cracked me up. And anyway, yes, highly recommended for shenanigans and for real serious AI news. Wow. So that's an application of AI that's really going to change everybody's life. I can see they really put their finger on the important issues, haven't they? They've done a mixture of things. I think at the end they talk about sort of frivolous, funny AI stuff as like, you know, a closer. And that was a bit of closer.

All right. Well, today we are not just here to talk about the things that the Wiener Smiths are excited about. Though partially we are. We're here to address questions that you have because we're going to. curious about the universe, and so are you. And we want to know about that curiosity. We want to understand where it takes you and especially where you get stuck. What ideas are not working together in your head? What concepts don't make sense? What have we talked about that didn't quite connect? Or what did you hear on another podcast, maybe with other weiner-smiths that didn't make sense to you, and you need Daniel and Kelly treatment? Please send us your questions and your curiosity to questions at

Daniel and Kelly.org. So let's jump right in with our first question. This first question is from Lincoln, from Florida, and Lincoln makes a pretty strong case for Florida. So let's go ahead and listen. Hello, it's Lincoln here from the best of the 50 states, Florida. If you don't agree, check the tourist count. According to special relativity,

the velocity of light always appears to us as C. However, as the object approaches a black hole, it appears to any observer to slow down and stop before reaching. the event horizon. Does this phenomenon actually occur? If so, could this be used in the distant future to study late and potentially begin to understand its fundamental nature? Thank you for providing a place for questions that make my friends stare blankly. Best regards from Lincoln. I like that Lincoln is using data to answer questions, you know? He's not just making wild claims about what state is best. Money talks, I guess. And there's a lot of money talking

in Florida, I guess. Well, I was just in Florida this week, and there's other data, I think, that points in the other direction, like the humidity and the temperature together points very negatively towards Florida being the best state. But hey, you know, pick your metric. But you made the mistake of mentioning the other day that Los Angeles was the most humid location on the planet last week or something, right? In the country, yes. In the go. In the country. But it was pretty sticky in L.A. last week. And that was a complaint. I was not bragging. You know, I was like, things are going downhill because California is approaching Florida or approaching Virginia levels of stickiness. Not good. All right. All right. Let's get back to the science.

Let's get back to the science. So we're talking about special relativity here. Give me the background on special relativity. So we're talking about special and general relativity here because he's asking a question about the speed of light near a black hole. But let's start with special relativity because the issue at the heart of this question is a constant. between what you often hear from special relativity and what we've learned from general relativity about how light moves. So let's start with special relativity. And the big fact at the heart of special relativity is that light always moves at the same speed. So if you have a flashlight and you click it on,

light is zooming out of your flashlight at the speed of light. If you happen to be on a train, moving at half the speed of light, somebody on the ground is going to see you moving at half the speed of light. And when they measure the speed of your flashlight beam, it's not going to be one and a half half times the speed of light, it's still going to be the speed of light. So that flashlight beam moves at the speed of light relative to you on the train, relative to the guy on the ground, relative to a particle moving through space, relative to somebody sunning themselves on the beach of Florida and getting skin cancer, relative to all of those people. It's constant. Unlike humidity in L.A., which seems to go up and down a lot, the speed of light is constant. Right. Okay. And that's

not you all just getting something wrong, right? That's real. That's right. That's real. That's something we've measured. It's fascinating. It's counterintuitive. It was a big surprise experimentally. It took forever for people to really absorb it and accept it. But it's real. And it leads to all the consequences of special relativity. The fact that there's no universal now that we'll talk about later in the program.

And the fact that things get shorter as they get faster, the time slows down, all comes from the same basic fact that light moves at the same speed, no matter what, whoever is measuring it. Right. And that's true no matter what your frame of references. is, right? If you're in motion relative to the earth, or if you're not, or if you're pointing in this direction, a point in that direction. And this is often said very, very absolutely, like the speed of light always moves or the speed of light, but there is a very important asterisk that's usually ignored that's going to be really crucial today. Okay. And that

asterisk is that this is true that the speed of light is the speed of light no matter what, as long as you are operating in flat space. What? So space is not curved. So if space is is flat and from here to the end of the universe, space is flat, then you can make this claim and you can measure velocity, and this is all true. But once space gets curved, you need general relativity to describe what's going to happen and how time flows and how things move. Special relativity no longer applies when space is curved. And that's what happens near black holes. So how much of space is flat and how much of space is curved? Do you just get curves near black holes or more info? Amazing question. Yeah, great question. So,

on the whole, the universe is flat. Like if you measure the curvature of the whole universe, it's on average flat. But on average flat doesn't mean locally flat. Like, you know, if the temperature on average in the United States is 75 degrees, that doesn't mean that it's 75 degrees in Florida. In fact, it's probably not. It's never 75 degrees in Florida. It's always 95. Anyway, near black hole, space is very, very curved or near the earth space is gently curved. However, space is always flat near you. There's always some neighborhood around you where space is approximately flat. And how big that neighborhood is depends on the amount of curvature.

So if you're in a part of the universe where there really are no masses, then space is flat in a really broad neighborhood. Even if you're falling into a black hole and space is really, really curved, there's always like a tiny little neighborhood in your vicinity where you can say, all right, but around here within like a meter or so, space is really curved. there's always like a tiny little neighborhood in your vicinity where you can say, all right, but around here within like a meter or so, space is close enough to flat for me to say that it's flat. So it's always flat in your little neighborhood. Okay, got it. It's like how the earth is round, but it doesn't look round to me because it's flat in my little area. Exactly, because you can only see a little bit of it, and so it looks basically flat. If you zoomed down and consider the whole Earth, you'd see the curvature. But it's a good approximation to say the Earth is flat around you, right? Okay. All right. So Lincoln is saying, hold on. I hear that the velocity of light is always see, right, no matter what, but near a black hole, time slows down and even stops as things approach the event horizon. What happens to a photon is it approaches the black hole? And does that break the rule of special relativity, right? And the answer is both really unsatisfying and also really deeply revealing about something really basic and intuitive that we don't often think about, which is how to measure velocity.

So the brief answer, which is really unsatisfying, is that you cannot measure the velocity of things outside your immediate neighborhood. Like the velocity of things that are far away is not even well defined. It's not even a quantity we really know how to talk about. And so the answer is you can't talk about the speed of photons that are far away from you in curved space. If they're in your neighborhood, then they're basically in your little flat bubble and you can measure their speed and you always get C. If space is curved and the photons are not in your flat bubble, there's like a lot of curvature between you and them, then there's no way to even define their velocity. Okay. Do you think one day we'd figure out how to do it or it's just impossible?

It's just impossible, right? And general relativity tells us why. And I love this kind of thing in relativity because it forces you to revisit something which sounds simple and obvious and think about the assumptions that go into it and then realize those are broken. And so you might be wondering, like, what does he talk? about how can you not measure something's velocity. Velocity is just like, I'm measuring the distance and I'm seeing how that changes with time, right? Duh. Obviously, you can still make those measurements. That's what I was thinking, duh. Well, let's think in a little bit more detail about what happens when we measure velocity, right? Technically, what we do is we compare two vectors.

Take a simple example. We have two people, they're running next to each other, right? You have Daniel versus Usain Bolt, right? And you might think, what do we do? How do we measure the velocities, well, we just see how they move across the earth and we measure the distance versus time, and that's the answer. And it's true that we get the distance versus time for each person, and that gives us two vectors, you know, a length in a direction for Usain Bolt and a length in a direction for Daniel, and then we compare them, right? And because Daniel and Usain Bolt are running in the same direction and right next to each other, the comparison is obvious. One's really big, one's not so big. Usain Bolt is faster than Daniel. Easy to do. All right. But what if Daniel can't

Usain Bolt to come and race against him right here. He can't get him to come to Southern California. Instead, Usain Bolt is running on a track on the other side of the planet than Daniel. Okay. Okay. How do we do it now? Well, we still have to compare vectors, but Usain Bolt's vector is now pointing in a different direction than Daniels, right?

Because the earth is curved. And imagine he's like on the opposite side of the earth and he's running in the other direction. So how do you compare the two vectors now? And you're thinking, okay, easy. Still, you just like bring one vector over to the other. and line them up so you can compare them, right? Duh.

Duh. And that works if space is flat. But the problem is that when you move a vector through curved space, there's a lot of different ways you can do it. And the choice that you make of how to do it gives you a different answer, right? But it's flat in your area. And Usain Bolt is running in a little flat bit. Why can't we compare the vectors?

You can do an approximation. you said, I'm just going to take the length of the vector, right? But really, velocity is a 3D object, and so you have to do a complete comparison. And so let me walk you through this example of what I mean by the vectors change through curved space. So say, for example, you're at the North Pole, and you have a spear, okay? And your job is to go on a little walk across the Earth and keep the spear pointed in the same direction. Okay. So it's parallel to the ground. You're starting at the North Pole and maybe you point your spear towards London. Okay. Okay. So it's pointing south, right? Yes. I'm menacingly walking towards London. Yes. All right. So you walk towards London with shaking

your spear, keeping it peril to the ground. It's still pointing south. Now you walk past London, you get all the way to the equator. Okay. Still pointing south. Now you walk along the equator, maybe like a quarter of the way around the planet. Your spear is still pointing south, right? Okay. Now you walk back towards the North Pole. Okay. Spears still pointing south. Has your spear changed direction? I rotate my hand. But is your spear pointing the same direction it was originally? No, not if I'm walking back north again.

Yeah, exactly. It's now like 90 degrees relative to where it was before. So you have taken a vector and you've moved it along a curved surface and you've come on a complete path and you've never turned your vector, right? And yet it's not pointing in the same direction as when you started. This is geometrically what we mean by curvature. If you take a vector and you take a journey and you come back and it's not pointing in the same direction, then that space is curved.

That's what we mean by curvature in some sense geometrically. So if you want to compare two vectors that are separated, in flat space it makes sense. In curved space, it does not make sense because you have to bring the vector over close to you in order to measure it, and that changes the vector. It can change the direction, it can change the length of the vector. And so that's why velocity for distant objects is not well defined in curved space because different people can choose differently. Like, I'm going to bring that photon's distant vector over to me this way. Somebody else can bring it over here this way.

And if space is curved, they can get different answers. And so there's not one definition for what that velocity is. And so the cop-out answer that simultaneously, I think, reveals something cool about the assumptions we make when we talk about velocity is, you can't talk about the velocity of really distant objects. For example, when we say distant galaxies are recessing at faster than the speed of light, isn't that breaking the rules of special relativity? Yeah, because that velocity is not actually meaningful. It's a way we talk about velocity to give people a sense for it,

but in general relativity, you can't really talk about the velocity of those distant galaxies. What's really happening is space is expanding between us and them. For example, those galaxies are not experiencing any. the acceleration, right? No accelerometers in those distant galaxies are indicating that they're accelerating relative to us. So the right way to think about that is space is expanding. And the right way to think about this is that space is curved between you and that photon. So you can't really measure the velocity. You can measure an apparent velocity. You can keep track of where it's going at various intervals and you can calculate what we call a coordinate velocity. Like here are the measurements I made.

Here's what I would call the velocity. But it's not the same velocity as somebody else would measure. and it's not just observer dependent. It depends on the choices you make of coordinates, which are arbitrary in general relativity. And so it's not well defined, unfortunately. So the story you hear when they say a photon as it approaches a black hole slows down is not bogus. It's just that it's an extension of these concepts beyond where they're really physical. And so Lincoln is asking, does that phenomenon actually occur? And I would say no. And the reason is that if you moved your observer to close to that photon? Like if you zoomed in and stood near the edge of the event horizon, what would you see? Well, if you're near the photon, you're going to see it moving by you at the

speed of light. And if you fall into a black hole, you don't see time slow down. You've just fall into a black hole and you move through the event horizon and towards the singularity. So this apparent slowdown is not a real physical phenomenon. It's an artifact of being distant and of there being a lot of curvature between you and the object. And unfortunately, there is no solid answer to what is the velocity of a distant object outside of your little flat neighborhood. Wow. All right. Lincoln, that was a lot, man. But there are definitely days where I'm like, oh, that's going to take me a week to think more about. But it was a great explanation. Physics is not always intuitive. It isn't, yeah. And so Lincoln, what do you think?

What do you think of, Lincoln? Do you think that's the first time he's heard that? You couldn't just let me have that, huh? No, that's not how you and I roll. Hello again from the greatest state, Florida. And may I point out that the humidity and the heat is normal to us? And you're just not a Floridian. Thank you so much for a clear and conceivable answer to my question. Although it is a little disappointed, at least now I can.

can understand how special relativity is just Einstein flexing. Thank you for the answer, and may you always understand why Florida is the best state. Also, that's like the fourth time I've heard Lincoln thinking this week. All right, we're back and we're answering questions from listeners, And as is tradition, apparently on today's episode, we are making lots of references to other podcasts on today's episode because we know you listen to other podcasts and that's cool. We do too. We don't expect an exclusive relationship. We want to know what else you're excited about.

Daniel, what podcast do you listen to as soon as it comes out? Oh, great question. I listen to this American life pretty regularly and almost immediately. I listen to hyperfixed quite often. I listen to heavyweight. Heavyweight is an excellent, amazing podcast. I love that one. And my guilty pleasure while driving is if books could kill because it makes me laugh and doesn't require me to think too much. Excellent.

Have it too. The rest is history and the underworld podcast. Nice. Those are, yeah, those are my two go-tos. But everyone's listening to the best podcast ever right now. And so let's focus on our podcast and answer a Discord question from Yard. Yarthfar the true. And we are continuing by tradition of not remembering to get first names from Discord listeners before we answer their question on the show. I'm sure that's the name on the driver's license, Kelly. Yarthvar the true. Why would you assume otherwise?

My mistake. My mistake. Let's hear what True comma Yarthfar has to ask. Hi, this is Mr. True comma Yarthvar, middle name the, with a question in the form of a statement mainly for Kelly. I would be interested in learning more about bacteria, or maybe other life forms. They're evolving to digest plastic. I think that I heard Katie Golden of Creature Feature Podcast mention a study on larvae eating styrofoam, for example. Thanks to the great question, Mr. True. Yeah, so this is a big problem, like the fact that there is all of this plastic waste all over the world. This could be a huge food source for animals that could figure out how to do.

to eat it. And so to try to understand the scale of plastics that we are putting in the universe, I found one site that said that we produce 360 million tons of plastic waste each year. And another that said we produce 450 million tons of plastic waste each year. So we are producing hundreds of millions of tons of plastic waste each year. And I guess plastic waste is like plastic we produce and then want to throw away because there's a lot of plastic we produce that we keep and cherish forever. That's right. That's right. No, waste, I think, definitely implies this is stuff that you have thrown either into the recycling bin or into the trash, but you are done with it. And chemically, like, what is a plastic?

I have this vague notion that it's like you take oil and you process it through chemistry and you get plastic. Is that basically what's happening? Yeah, that's basically what's happening. But the important thing to note is that that oil has a bunch of carbon in it. And a lot of the, like, things that we eat have carbon in it. I like carbon. I love carbon. Right.

There's crunchy bits and you've cooked something a little bit too long, as Katrina calls the cancer ends. I love the cancer ends of stuff. Yeah, I love the cancer ends of stuff too. Just to try not to eat too many. You can enjoy them sometimes. But if you can cut those carbon chains in different ways, you can make different compounds. And this is chemistry. That's my best definition of chemistry there.

But so the question is, can you take carbon chains in plastic and cut them into ways that produce things that are edible? I see. And it appears that some bacteria, some fungi, and some worms have figured out how to do that. And the first time we sort of recognized that this was happening in nature that I could find was in 2016, there's bacteria in a recycling plant in Japan. that was found breaking down the plastic. And in particular, the kind of plastic we're talking about is P-E-T. This is found in a lot of water bottles, found in a lot of different kinds of like jugs. It makes polyester.

Your clothes have a lot of this kind of plastic in it. It's a very common plastic. And this bacteria was producing an enzyme that has been named P-E-T-Aase. Okay. And A's is something we often refer to in chemistry for like, it's an enzyme that helps. catalyze something or make some reaction happen? So my first Google result, National Institutes of Health, is apparently the reference. It says enzymes are biological catalysts usually made of proteins that speed up chemical reactions

and living things. Cool. And no surprise that it's a microbe that first does this. Katrina is always saying microbes learn how to eat anything. Yep, yep. And we heard, like, from your friend who's an expert in the deep underwater vents, like microbes are down there eating crazy stuff. Yeah.

So thank you, microbes for pioneering everything, basically. And what we're going to get to is that we are trying to figure out how to use this for our own purposes to try to break down a lot of the plastics. And so the bacteria that they discovered, it looks like it actually has two reactions that it does. Like the first one uses that P.A.T.A.s. And then it breaks those products down into two smaller carbon chains. One is teraphthalic acid and the other is ethylene glycol. And what you need to know there are two things that I, I think I'm getting correct here. One is that at this stage, the bacteria can start eating those things and using the carbon.

And two, these are also ingredients that we use to make more PET. So once this reaction has happened, if you can collect the products that were made by the bacteria, you can then start making new plastic products, which could be very helpful in, like, recycling plants and stuff. So you're saying the microbes have this enzyme in them, which breaks. down the plastic into stuff that their metabolism knows how to ingest. Yep. And also produces stuff that we can use to make, yay, more plastic. That's amazing.

And are they making this P-E-T-A's, or did they, like, find it, or is it occurring naturally? Or, like, is it expressed in their genome? So I think the best guess is that it evolved from feralic acid esterases. Who cares? The answer, what you want to know is that this is something that they use to break down plant walls. So this was something that they were using to get into plants. And with a little bit of tinkering, it can be used to start breaking down plastic.

So this isn't something that the bacteria had to, like, you know, evolve out of nothing. This is something that they already had that it turns out if you change it a little bit. You know, for example, you've got, you know, billions of bacteria, maybe trillions, quadrillions in a recycling plant. You know, some of them had a mutation in this thing that's breaking down plant walls. And then it actually turned out that that helped them break down the plastics. and now they've got this like head start on a new food source. Yeah, that's a great example of evolution, right? You have something which does a different job

and you randomly evolve to do something new, which unlocks an enormous new food source since you can see why that would help those populations survive. I guess I'm surprised they didn't happen faster. Yeah, right. Well, and it's actually not happening super efficiently yet. Like another thing to understand for evolution is that like, you know, if a mutation happens and suddenly something that was breaking down plant wall

is now helping to break down plastic, you don't necessarily get the most efficient version of that enzyme, right? Right. For that enzyme to get better over time, you need to have, you know, for example, more random mutations that need to get, like, tried out as they change the way the enzyme works, and then the individuals that have the slightly more efficient enzyme

or the ones that have more babies, and, like, it's a very long, slow process that depends often on random things happening along the way. And so there are some labs that are specifically taking, like, the code for these enzymes and are mutating it to much more quickly move through all of the different ways, all of the different shapes that this enzyme could take and see if any of them are actually much more efficient

if you essentially speed up evolution in the lab. Uh-oh. But then, like, what if you release these things? And they, like, dissolve all the plastic in the world in five seconds. Yeah, right. So that's something that people joke about a lot. I mean, they're still going to have to compete with all the other bacteria on the planet. They will have this massive new food source.

Maybe this is something we need to work. about? I didn't find a lot of people panicking about it. What do you think? How much would you worry? How much would Katrina worry about this? That's what I need to know. I mean, I don't think I'm even aware of the role the plastics play in my life. Like, imagine all plastics on the planet were instantly deleted. Like, I guess my glasses would fall apart and my computer probably would fall apart. And probably my car wouldn't work. Yeah, we'd be poned. I don't think we're ready for that. So be careful, biologists.

Yeah, right. It's not just physicists who can destroy the world. Well, so we will get to, in just a second, we'll get to the ways that people are trying to be a little bit careful about this. Okay. But I just wanted to note real quick that there's a company called, I think, Carbios. And they are essentially, they're the ones that are like doing this, you know, evolution in the lab thing to try to find more efficient enzymes. And they're trying to break down preexisting plastics. And they have some, like, deals with companies that make makeup.

make up containers, and they are trying to upcycle it back into more plastics, which is kind of cool. So a lot of stuff would be staying out of the landfill or like coming out of the recycling plants more quickly. So, okay, but so then the question is, if you have, for example, done something in the lab and genetically modified an organism, like for example, maybe you decide that these enzymes it would be better if they were made by E. coli than if they were made by the bacteria we first found them in, because it's just easier to manipulate E. coli. So you put the genes for this enzyme in E. you probably don't want to release that into the environment because people are very uncomfortable about genetically modified organisms. And if you're the person that makes it so that all the plastic gets digested, you're not going to have a lot of friends.

And so what they're doing is they are working on ways to, for example, make E. coli. And by they, I mean like different groups, not necessarily the Carbios group. But anyway, they're working on trying to get E. coli or other bacteria to produce enzymes in large quantities in the large quantities in the large. lab, and then they release those enzymes into places where plastic needs to get broken down. So they're cutting the bacteria out, but they're releasing the enzymes. And like your laundry detergent has enzymes in it. That's cold-blooded, man. Why is that cold-blooded? You're getting the bacteria to produce this enzyme. They evolved so they can eat, and you're using it to break down the plastics without letting the bacteria have lunch. That seems

cold. They're probably feeding the bacteria because they want them to keep surviving and making this enzyme. I guess it depends on do you have to kill the bacteria to get the enzyme or do the, can you make the bacteria excrete the enzyme in some way? We should have invited Katrina today. The bacterias should unionize, man. They own the means of production here, right? They have nothing to lose but their chains. That's right. That's right. Getting political. But I guess I'm a little confused. I would have thought this is something you wanted to introduce into a landfill so that the plastic and The landfill like degrades more quickly, turns back into soil, all that good stuff. But it sounds like you're saying we want to like collect plastic out of this waste stream and isolate it

and then break it down so we can like reuse it to make more plastic and stuff. Isn't there like a big energy cost to recycling and taking these things out of the waste stream? Is that really worth it? So it depends on who you're talking to what the goals are. So there are some groups that would like to take plastic that's already going to a recycling plant, for example. and use that to make new plastic stuff. And so essentially just make the recycling process a lot simpler. There are other folks who are, for example,

taking plastics maybe from a recycling plant, and then they're trying to turn it into things like vanelin, which is the chemical that gives vanilla its taste. And apparently you can make that by breaking down plastics and then just tinkering with it a little bit. What? You can make vanilla flavor from plastics? Yeah, yeah.

Apparently, we already make vanilla flavor from petroleum stuff. What? And so the, like, scientist that was, you know, answering questions was a little bit defensive, presumably because this has been asked of them many times. But if you get synthetic vanilla flavoring, it might have a bit of a petroleum background. All those folks out there who defend vanilla ice cream is like a legitimate flavor and a competitor to actual chocolate ice cream? Like, yeah, I don't think so. Yeah, I agree. They're bad people.

Wow. I was trying to be choice in my words, but that's what you hear for, Kelly. Unleash it on everyone. That's right. That's right. I was obviously joking. But then there's other groups that are, for example, trying to put these enzymes into bacteria that can survive in saltwater environments so that then you could release those organisms like, I don't know, into the giant trash patch in the ocean. I actually think there's many giant trash patches because we're a great species. We're wonderful. We're at the best. And you could release them into the ocean and then let the bacteria start breaking down those trash patches. So there's some people who are talking about like wanting to release this stuff into the environment.

I think a lot of people have very complicated feelings about genetically modified organisms. And so I think there'd be a lot of people you'd have to convince that that was a good idea if you wanted to go forward with that. Right. But Mr. True wanted to know if there were other organisms that do this.

It looks like fungi do it as well. They have an enzyme. that breaks cutin down, and this is a part of plants again. And so fungi here again have a thing that they were using to break down plants, but it turns out with a little bit of tinkering, it can break down plastic. And so some fungus can do this as well. And some wax worms appear to be able to do this. So there was a scientist who had some beehives,

and these worms are really bad for beehives. And she started taking them out of the beehive, and then she put them in a plastic bag, and she noticed that not only were they eating their way out of the bag, but anywhere their saliva had touched, the bag started to degrade. And so I think the follow-up work suggested that to some extent this is stuff being produced by their microbiome. So it goes back to bacteria again. But there are some worms that seem to be able to, some like grubby things that seem to be able to live on plastic as well.

Wow. Fascinating. Yeah. So anyway, maybe we will be able to harness biology to fix a massive problem that we have caused, but we're going to have to wait and see. It does feel like biology has these tools, or at least it's better at adapting. I mean, the whole process of, like, evolution is just such an incredibly parallel way to search for new techniques, right? You have, like, quadrillions of bacteria constantly trying new things and evolving in new ways and the chances that we could, like, find a new solution faster than a zillion bacteria all

in parallel seems ridiculous. But it's cool that you then isolated and fine-tune it and then are hopefully careful about how you implement it. Yep, we can be inspired by biology in a lot of different ways. All right, let's see what Mr. True has to say, or Ms. True. I didn't realize that Yarthvar could also be a lady listener. So anyway, Mix, MX, True, what do you have to say? Hi, Yarthbar again. Thanks for the informative and complete answer.

I don't have any follow-up questions, but I do have a couple of comments. First, I echo your concern with releasing these organisms into the environment. I would hope that we only take such a bold step after conducting our due diligence with the utmost of rigor. Second, even though there is a grain of hope that these organisms might break down some of our plastic waste, I think that we still need to limit the amount of plastic that we allow into the environment. And finally, Yarthfar actually is my name, though in a different language. It's Edward in Old Norse, the medieval language of my Scandinavian ancestors. It might sound funny to the modern ear, but I prefer it to my other ancestral option.

Old English is idewird or it twirred. Anyway, thanks again. I appreciate you both and wish good health and happiness to all. All right, and we're back, and our last question of the day is from Sebastian. Daniel hinted earlier in the show that this would have something to do about the speed of light and time. Let's go ahead and hear the question. Hi, I've been trying to wrap my head around the block universe for a while. For my understanding, you always see a different slice of space time depending on your speed and direction.

So if you and I are traveling in different directions at high speeds, we would have a different view on what is now. What does that say about the future being unwritten? or is the future already determined in this theory? If so, what are arguments for or against the block universe? Thank you. Love the show. I remember that you and I once had an episode where we were checking out like sci-fi books and movies and how they dealt with like space and time and time travel.

And at the end, I was like, well, this was a Daniel is a wet blanket episode, which is out of the ordinary, but you know, very refreshing. And so I'm looking forward to what you have to say here. This is a really fun question because it gets at the heart of like, what does it mean that special relativity breaks our ideas of now? And, you know, do we still have free will or is the future somehow determined because maybe somebody else can see more of it than we can or something? So let's dig into it first and remind ourselves what exactly special relativity says

and doesn't say about time and about now and the future. Okay. So special relativity says that light always moves at the speed of light, regardless of the observer or your velocity as long as it's nearby, right, in a little flat neighborhood. And that breaks our sense of whether things have to happen at the same time or not. And the classic example is Kelly's on a train and she has two flashlights, and she shines a flashlight forward and a flashlight backwards. And because she's standing in the center of the train car, she sees the light beams. hitting the front and the back of the train at the same time, right? Makes perfect sense.

They go the same distance and the same amount of time. Of course they hit the front and the back at the same time. But Zach is not in the train with Kelly. He's on the ground. He's eating his breakfast cereal or whatever. He's watching Kelly on the train do this experiment. What does he see? Well, he sees the back of the train moving towards where the light was emitted

and the front of the train moving away from where the light was emitted. and because the light moves at the same speed relative to Zach, he sees the light hit the back of the train first and the front of the train later. That would not be true for sound waves, for example, because sound waves don't move at the same speed for all observers. They move at the same speed relative to their medium. So, for example, if Kelly shouted instead of using light beams,

then Zach would see the shout moving slower going backwards and faster going forwards, because it's moving at the same speed relative to the light beams. the air, which is moving relative to him. But light doesn't work that way. Light moves at the speed of light no matter what. And so he sees it hit the back of the train before he sees it hit the front of the train. So Kelly says these two things happen at the same time. And Zach says, no, they don't. And somebody else going the other direction sees the opposite, sees it hit the front of the train before the back of the train. What's going on? Is the universe broken? No, what's going on? Is it

that special relativity tells us that there is no global now. It's not like there's one clock for the whole universe and the universe ticks forward one step at a time and everybody can agree on what time we're at and what's happening at the same time. Instead, like the listener asked, we all see like a different slice of space time depending on our speed and our direction. So there's as many moments of now as there are locations in the universe and velocities in the universe. So if you're not at the same location and you don't have the same velocity, then you see time flowing in a different way. And you can even disagree about the order in which stuff happens. And so are we like mostly talking about little things like, you know, you're a second or two off about when the light hits the

train or could, are we talking about you could be a year or two different? I guess it depends on how far the thing has traveled. Like if you're looking at how far light traveled across the universe and you got different results. Yeah. How big of a time? I'm very confused. It can be a big difference. You know,

if somebody gets on a spaceship and they're moving 99% of the speed of light away from us for a long time, then their clock can differ by years from our clocks. So it can be a huge difference. And that's actually nice if you're going to travel to like Alpha Centauri, you know, then it might take a long time on Earth clocks for you to get there, but it doesn't take that much time on your clock on the ship, which is nice because you're the one on the ship. So it can be a big deal for sure. And for people who wonder, like, hold on a second, how can the order of events be changed? You know, like, if somebody shoots an arrow at an apple, can somebody else, like, see the apple get hit before they shoot the arrow? Does this break causality? The answer is no, there are limits. Special relativity can, reorder events, but only ones that are causally disconnected. I think we're living in a simulation by somebody who wrote a fictional world that has kind of crazy rules, but we have to follow them.

And this just is very counterintuitive. Yeah. Events that are close enough in space and time where light can move between them are causally connected because you can like send a message from one to the other. And those events, you cannot reorder using special relativity. Only things that are causally disconnected where they're far. enough apart that light can't go between the events. Those things, you can't send any message from one event to the other. So those kind of events can be reordered based on your velocity. All right.

So what does that say about the flow of time, right? Are different people seeing into the future or different futures? Like, definitely what I consider to be now is different from what you consider to be now. And it's tempting to imagine that, like, you know, Zach versus Kelly are seeing different slices of the future and that what they're doing is just revealing slices of an already determined future. And your speed through the universe is just determining which slice of the pre-existing space-time block you're getting. It's tempting. And that's the theory of the block universe that says that the past, the present, and the future all exists simultaneously within some four-dimensional space-time structure. What do we mean by four dimensions? Well, you know what we mean by three dimensions? of space and time. You have X, Y, and Z, three directions you can move in space. Now, if you imagine that

to be a 4D structure, that just means that, like, through time, stuff is happening in space. And so you can't, like, stack up 3D spaces on top of each other in a 3D space. You have to imagine it, like, changing as you move the arrow of time. And so in this block universe theory, the past, the present, the future are already fixed, right? Like, the future exists as much as the past exists and the present exists. The way, like, when you go to watch the Spider-Man movie, the ending is already determined. You're just happening to watch a certain frame of it. You haven't seen the ending, but the past, the present, and the future in the movie are already fixed. So the block universe theory says that that's our universe, that the past, the present,

and the future are already set, and we're just like, we're having a certain slice through it. And the special relativity version of that is the slice you see of the universe depends on your location and your velocity. So this is a no free will theory. Is that right? Exactly. It's a no free will kind of a theory. And so Sebastian's question is, does special relativity imply the block universe? And I would say no, it's compatible with the block universe, the idea that special relativity gives you a different slice of that block universe. But as you say, the block universe is a deterministic theory. It says the future is already set. But special relativity doesn't require that. Special relativity says, that the past, the present, and the future are different for everybody.

Like, we disagree about what now means, but it doesn't mean that you don't have choices to make. You can still have a universe where the laws are probabilistic, for example, like quantum mechanical, right, where the outcome of an experiment is determined by random probability, and not fully determined by the past. So the past might determine the probability of something happening, but not the actual outcome. And so the past doesn't determine the future. in our universe, for example, because we think the universe is quantum mechanical, and so the universe is not fully deterministic, and so it's not consistent with the block universe.

So special relativity just means that now is local. It doesn't mean that the future is determined. You know, it says something weirder. It says that you don't get a unique universal answer to the question, what is happening everywhere right now? But it doesn't say that the future is determined. And remember those cones we talked about, like where you can influence and things that are causally linked to you or not causally linked to you. Special relativity doesn't say that like Kelly has seen my future because she's moving at a different velocity or whatever. You know, you can rearrange certain events, but only things that are not causally linked

together. So it's not like Kelly can see what I've decided to do, right? Kelly can't rearrange the future in a way that changes my chain of cause. Oh, that's too bad. Does that make sense? Yeah, it makes sense, but it's disappointing. I mean, you can influence the decisions I make, and you certainly do. Make a good argument. Make a funny joke. You're definitely going to influence the path of Daniel's life, but not by getting on a train at half the speed of light.

Okay, got it. All right. And so if you didn't already predict that answer, Sebastian, in your block universe, then I'm curious how our answer determines your response. Hi, Daniel and Kelly. I think that clears it up. So free will still has a chance. All right. Thank you, everybody, for sharing your amazing questions with us today. As a unfortunate reminder, Kelly is still on an email hiatus and probably will be till

2027 because I have about six months of amazing questions from you all to work from still. So hold on to your great questions. I still am going to want them at some point, but I'm working through the stack as we go. All right. Thanks, everybody. We really love hearing from you, hearing about your curiosity, hearing your questions. and we love being a part of your journey of curiosity. Thanks so much for taking us along for the ride.

Thanks for listening. Thanks everybody for listening. Please go and do us a favor and rate the show on whatever podcast app you're using. It really helps people find us. Daniel and Kelly's Extraordinary Universe is edited by the amazing Matt Kesselman. He really is a wizard.

You can also find us online on Blue Sky, Instagram, and X. D&K Universe. Come engage with us. You can email us at questions at Daniel and Kelly.org. We really do want to hear from you. And you can find our website, www. Daniel and Kelly.org, where you'll also find an invitation to join our Discord where everybody comes and talks about the amazing universe.

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