Can fast-moving potatoes become black holes?

Daniel and Kelly try to unravel some popular mis-explanations about the wonders of special relativity, potatoes and photons. See omnystudio.com/listener https://omnystudio.com/listener for privacy information.

Speaker names marked ? are inferred from speaking time and the show’s known hosts — they are not voice-verified.

• 0:00Daniel Whiteson?

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• 2:19Daniel Whiteson?

  The world out there is a wonderful, intriguing puzzle. Sometimes it feels like it makes little sense, constantly refusing to obey our intuition or behave the way that we expect it to. Quantum mechanics tells us electrons don't follow smooth paths. Relativity tells us time doesn't flow the same way for everyone. And yet, we can make some sense of it. We have math that describes it and predicts it. It's incredible that the universe is so finely balanced. It's complicated enough that it's taking us thousands of years to unravel its truths. But it's simple enough that our tiny brains can make progress year after year. So let's keep hoping that trend continues. But even when we have wrangled a bit of math that seems to work,

• 3:03Daniel Whiteson?

  it doesn't mean our intuition goes along for the ride. Sometimes when we translate the math into popular science, intuition and dramatic clickbait, the reality is lost. Maybe you've heard that a potato approaching the speed of light can turn into a black hole, or that photons don't experience time. Unfortunately, neither of those things are accurate. Today, we're going to try to untangle some of these widespread misconceptions about special relativity and show you that the truth of the universe is plenty weird and wonderful without clickbait. Do photons experience time? Does a potato become a black hole if it goes fast enough? Welcome to Daniel and Kelly's extraordinary, but amazingly comprehensible universe.

• 3:57Kelly Weinersmith?

  Hello, I'm Kelly Wiener-Smith. I'm a biologist and I am super excited to let Daniel be the wet blanket today.

• 4:05Daniel Whiteson?

  Hi, I'm Daniel. I'm a particle physicist, and I'm not going to throw a wet blanket on the universe. I'm going to show you how it's even weirder than what you've been told.

• 4:14Kelly Weinersmith?

  Yeah, that's what I do all the time also, Daniel. It's all about packaging the idea.

• 4:19Daniel Whiteson?

  That's right, exactly. Make it sound positive.

• 4:23Kelly Weinersmith?

  That's right. So my question for you today is when you were a kid and you watched physicsy kinds of movies, were you concerned with whether or not they were accurate? Or did kid Daniel just enjoy whatever he was watching?

• 4:36Daniel Whiteson?

  Hey, there's an implication there that adult Daniel can't enjoy movies. I don't appreciate that. That's not true.

• 4:43Kelly Weinersmith?

  Go ahead and tell us about the trajectory of your life and how it has evolved with movie watching.

• 4:48Daniel Whiteson?

  You know, when I watched movies like that as a kid, I was just amazed and awed. I thought it was fantastic to think about these things and to push against the edge of our knowledge. Could we live in four dimensional space? Could aliens be six dimensional beings? Is it possible to travel through time? I thought those movies were wonderful because they pushed us past the edge of our current knowledge and imagined how the universe could be different. And now, of course, as a grown up scientist, I know something about what we do and don't know and which of those ideas are possible and which of those ideas are not really possible. But I appreciate the creativity in that. I think it's important that we push past that and that we try to break outside of the box of our current ideas.

• 5:26Kelly Weinersmith?

  So you could watch a movie that clearly had an incorrect physics concept and straight up enjoy it. Is that right?

• 5:34Daniel Whiteson?

  You know, if they're going to embrace life in a different universe with different laws, that's fine. Go for it. But if they're going to pretend to be in this universe and then they drop a bunch of like pop sign nonsense to make it sound like they talked to a physicist when they didn't. And they're all Higgs boson this and quantum fluctuation that, then yeah, that's annoying. Because like, hey, reach out to a scientist. It's not so hard to get like actual realistic scientific babble instead of pure nonsense from your chat GPT. Like, come on, email me, I'll answer. I'll help you get actual science into your movie.

• 6:04Kelly Weinersmith?

  I think the one time where I was like, maybe I'm going to ask for my money back. What was the movie? It was with John Cusack and I loved John Cusack, but it was like the neutrinos have mutated. And I was like, oh, can I get past this? I don't think I can. It was one of those like end of the world disaster movies.

• 6:23Daniel Whiteson?

  The neutrinos are going to kill us all.

• 6:25Kelly Weinersmith?

  That's right. I was like, they're neutral, guys. It's all right. Anyway.

• 6:30Daniel Whiteson?

  Yeah, I mean, if people want to embrace something awesome and new, that's fantastic. And I think that being creative that way is cool. But if you want to use real physics, like, reach out to a real scientist. There's so many folks who would happily help you make the science in your show real. And, you know, then it's even better because the people who are listening and know something are then like not jerked out of their experience by the bizarre nonsense you just injected into their brains.

• 6:55Kelly Weinersmith?

  We would all love to be involved in TV shows and movies. That makes us like the cool kid in the room. So like, give us the chance to be the cool kid, man.

• 7:03Daniel Whiteson?

  Yeah, Christopher Nolan, write to me. Come on.

• 7:05Kelly Weinersmith?

  That's right. That's right. And there's gotta be a bunch of parasite movies that people could be, you know, talking to me about. But all right. Well, today we're focusing on two very specific ideas that are often wrong in PopSci.

• 7:17Daniel Whiteson?

  Yeah, that's right, because there's a lot of popular science descriptions of special relativity. What happens as you approach the speed of light and what's it like to be a photon and all this kind of stuff. And some of it sounds really cool and is really fun to read about, but is actually kind of nonsense. And the worst part is that it's obscuring the reality, the awesomeness of our universe. And the truth is always so much weirder than the nonsense, which I love. And so because people write in quite often asking these kinds of questions, I thought it'd be fun to try to disentangle some of the common misconceptions about special relativity. But before we dig into those particular topics, I was curious what people thought were the most popular misconceptions about special relativity, the things that people didn't

• 8:01Daniel Whiteson?

  understand about it. So I went out and asked our listeners, if you would like to join our group of volunteers, please don't be shy, write to us, two questions at danielandkelly.org.

• 8:11Kelly Weinersmith?

  We were going through and Daniel and I released a survey, which you can get on our website, danielandkelly.com. And I was going through some of the answers.

• 8:18Daniel Whiteson?

  No, no, danielandkelly.org. Unless you're a guest at Daniel and Kelly's wedding, in which case go to danielandkelly.com. Congratulations, you two lovebirds.

• 8:26Kelly Weinersmith?

  Thank you for the correction. Yeah, I was looking through the answers and somebody wrote to say that they would like to hear a lot more female voices for this question and answer session. And so if you are a woman who is on that list, we would really love to hear from you. Or if you're a woman who would like to answer these questions, we would really love to hear from you. I had a journalist reach out to me the other day and I told them, oh, sorry, I'm not an expert in that area. So I'm gonna pass. And they wrote back and they said, men never pass. Women are the ones who are like, oh, I'm not quite sure I'm an expert in this. And so what I'm saying is, ladies, let's go all in on the confidence and just answer it. And if the answer is, I don't know, that's fine, too. Let's get your voice out there.

• 9:06Daniel Whiteson?

  Absolutely. Ladies, please chime in. All right. Without further ado, here's what our listeners had to say.

• 9:14Speaker 04

  Whether I'm thinking of special relativity or general relativity.

• 9:17Speaker 05

  A time dilation.

• 9:18Speaker 06

  If you put a gun to my head, I couldn't tell you the difference between special and general relativity.

• 9:24Speaker 07

  Time dilation, that if you somehow get into a ship and approach the speed of light, or close to the speed of light, that your clock will run slower.

• 9:32Speaker 01

  The speed of light is constant for all observers regardless of their motion or location or whatever. Why does the speed of light always appear to be at the speed of light regardless of my speed?

• 9:46Daniel Whiteson?

  Well, I'm ashamed to say I can't remember the difference between special and general relativity.

• 9:52Speaker 01

  How to become special enough to be recognized by the special relativity crew?

• 9:58Speaker 05

  The visualizations of invisible fabrics as well as two dimensional sheets used to explain four dimensional curvature makes space time more confusing.

• 10:07Speaker 01

  Why is it special? There's more photons than anything else, so wouldn't that kind of be a general thing? How observers can see events in different orders. That if you exceed light speed, that time will run backwards. I've never understood why we say the universe is about fourteen billion years old, but a photon traveling at the speed of light since the big bang has experienced no change in time. The odd fact of the speed of light. Why is the speed of light three times ten to the eighth meters per second and not some other number? I don't understand how, despite the variables, light can never exceed three hundred thousand kilometers per second.

• 10:52Speaker 01

  That the speed of light is constant, no matter where you're observing it from or how fast you're going. It's the fact that the speed of light is a constant. Misunderstood is E equals mc squared, because most people think it's got something to do with relativity. That there is no god beside the universe with an absolute clock who judges who is right.

• 11:14Speaker 04

  Fixed speed in a vacuum, no matter what your speed is.

• 11:18Kelly Weinersmith?

  All right, some great answers. And I gotta say, every time we have a conversation, I get closer to understanding relativity, but not all of it sticks. And so I'm looking forward to being reminded of the difference between special and general relativity today.

• 11:32Daniel Whiteson?

  Right. So today, we are only digging into special relativity. General relativity is a whole other hairy beast. We are not even going to try to tackle today because special relativity, even though it's simpler than general relativity, is plenty confusing. It already requires you to distort how your brain works and accept that time flows differently for people in different parts of the universe. Briefly, special relativity is physics in flat space where there's no curvature, there's no masses, no gravity. It's just like beams of light and clocks and things moving fast. And it tells us how time flows and how things are relative, even outside of like black holes and all that weirdness.

• 12:10Kelly Weinersmith?

  So this is not dealing with any bending of space or time?

• 12:13Daniel Whiteson?

  That's right. Yeah, exactly. Imagine space is purely flat and we got a bunch of physics nerds doing experiments with lasers and clocks and cats and all sorts of stuff, but we got no black holes, no gravity, nothing like that.

• 12:26Kelly Weinersmith?

  All right, great. I think I can wrap my head around that. Where do we start then?

• 12:30Daniel Whiteson?

  Well, my favorite thing about special relativity is that it lets you dig deep into your understanding of like the very fabric of reality. And I know that sounds like pompous and grandiose, but it's true because that's what it's dealing with. It's describing space and time and helping us grapple with like what that really means. And you know, philosophically, it's awesome that you can say, hey, here's a mathematical model that describes what's happening out there in the universe. And if it works, if it describes the universe faithfully, then I can look at that model and say, hmm, maybe I can learn something about the universe by studying this model. If I have a mathematical description of the universe, does that description reveal something about reality? To me, that's the juice in all of this physics. And you know,

• 13:11Daniel Whiteson?

  one of the most important things to understand in special relativity are very basic things like location, like velocity, like acceleration, like what do these things mean in special relativity? And how are they different from like how new? Newton or Archimedes or Aristotle thought about these very basic concepts.

• 13:29Kelly Weinersmith?

  A while back, we had two topics that I think would be helpful intros to this. If anybody wants to go back and get some more background, we had an episode on what is time and what is space? And as I was looking at your outline, I thought, oh, that's helpful background information for this discussion.

• 13:41Daniel Whiteson?

  Yeah. And so the headlines for special relativity are that location and velocity are purely relative. There's no absolute measure of location and velocity, but acceleration is not. Acceleration is an absolute quantity. So let's start with location. What do we mean when we say location is relative? It just means that your location can only be described relative to other stuff. There's no like set of markers in the universe, no like axes glowing in space where you can say, my location is in this quadrant. It's always like, I am five kilometers from that, or I am two meters from this. That's the only way to define your location in space.

• 14:23Daniel Whiteson?

  There's no reference points. Another way to think about this is that location is a property of a pair of points, not a single object. Like a single object doesn't have a location. Two objects have a distance between them, but there's no meaning to say, my coffee is at this location. You can say, my coffee is a meter from the ground, or my coffee is 6,000 kilometers from the center of the earth, but my coffee has no location on its own.

• 14:49Kelly Weinersmith?

  And there's no greater question than where is my coffee?

• 14:55Kelly Weinersmith?

  So thank you physicists.

• 14:58Daniel Whiteson?

  Exactly. I mean, I'm trying to be practical here, you know?

• 15:00Kelly Weinersmith?

  Yeah.

• 15:00Daniel Whiteson?

  It's not all spaceships and cats flying through space. And this is sort of hard for a lot of people to wrap their minds around because they think of locations as absolute, the way Newton did, right? Newton thought of space as absolute. He thought even if there's nothing in the universe, there is still space. But you know, we think of space as just the distance between things. And that's a really important framework for understanding general relativity if you get there, because the bending of space can be understood not as like the curvature of space relative to some other external metric. There is no other external metric, but just the changing distances. Between things because that's all we have. So it's important to remember that distances are just relative, right? Your location is just relative.

• 15:43Daniel Whiteson?

  And that's also true about velocity. Velocity also purely a relative quantity. This one, I think, is even harder for people to grapple with.

• 15:52Kelly Weinersmith?

  So you said there's no like grid. And this is a stupid question, but like, would our understanding of location change if we had infinite money? And we put a grid in space? And like, you know, every one light year, we put like a blinking buoy like in the ocean. How would we still be in the same position, even if we had that grid?

• 16:11Daniel Whiteson?

  Yeah, if we had infinite money, I wouldn't recommend spending it on that grid. Because it wouldn't change our relationship with space. Like, you could still define your location relative to a point on that grid. That's fine. But now you've created an object, you've put it there and you said, I'm going to create axes at this location. And therefore I can define my distance from this buoy or from that buoy or from the other thing. That's no different from saying, here I am relative to my coffee or relative to the center of the earth. But you haven't anchored those buoys to like space itself, right? You could shift all of space over and nothing would change in your measurements. Because space itself doesn't have a location, there's no frame to space itself. Right? You can't say, my buoys are here relative to space. That means nothing, right? Space has no frame.

• 16:56Kelly Weinersmith?

  You just saved us all a lot of money.

• 17:00Daniel Whiteson?

  I'd like to take 5% of that infinite dollars and divert it to my own research.

• 17:05Kelly Weinersmith?

  You might need it. All right, so let's move on to velocity and acceleration. And I'm going to be honest, I often forget the definition of velocity and the definition of acceleration. So let's just start there.

• 17:16Daniel Whiteson?

  Okay, cool. Well, velocity in principle is very simple. It's how is your location changing?

• 17:21Kelly Weinersmith?

  Okay.

• 17:22Daniel Whiteson?

  Location is in units of like distance, meters, kilometers, whatever. Velocity is distance per time, right? So meters per second. How is your location changing? So if you're in a car on the ground, your location is where are you relative to your house? For example, and your velocity is how quickly is that location changing? Right? So that's why you measure it in like meters per second or kilometers per hour or something.

• 17:47Kelly Weinersmith?

  Okay, so the way you just said it, it's also relative to something. You don't have an absolute velocity.

• 17:53Daniel Whiteson?

  Exactly. You always measure relative to something because there are no absolute references, right? How could you measure it in an absolute sense if space itself is not absolute? If there's nothing to grab onto on space, nothing everybody can agree on. So you and I can measure the speed of a passing baseball and we can disagree because maybe you're in a car and I'm on the ground. And so you measure the baseball traveling at one speed and I measure it traveling at another speed. The baseball has no speed inherently. It has a speed relative to you and a speed relative to me. I think that makes sense to people, but it tells us that speeding is not a property of the object. It's a property of a pair of objects. And I think most people are totally cool with that. And I see you nodding. But then you get a lot of people talking about what happens when you're moving

• 18:38Daniel Whiteson?

  near the speed of light. My question is always near the speed of light relative to what? There is no I'm moving near the speed of light or I'm not moving near the speed of light. You're already moving near the speed of light relative to particles that are shooting at the earth. If those particles are moving towards the earth and near the speed of light, the earth is moving towards them at near the speed of light. So you're already moving near the speed of light. You're also moving at zero velocity relative to your shoes, right? Which are probably, I hope, attached to you or to your head. Let's say your head, for example. So you have multiple speeds. You have speeds relative to any potential observer. So it makes no sense to say, I'm moving near the speed of light, or I'm not moving near the speed of light. You're moving at any speed relative to any observer that

• 19:23Daniel Whiteson?

  could be observing you.

• 19:25Kelly Weinersmith?

  I didn't realize I could claim that I was going so fast. I'm gonna go ahead and cross the exercise box off of my New Year's resolution list. I am speeding around this universe.

• 19:34Daniel Whiteson?

  I always tell people, you're very quick.

• 19:36Kelly Weinersmith?

  Yes, thanks. Yeah, you're very quick, too. We're all very quick. It depends on what you're comparing to.

• 19:41Daniel Whiteson?

  Yeah, exactly. And this is an amazing and confusing thing about special relativity because time depends on this speed, right? What we say in special relativity is that moving clocks run slow. So if there's a spaceship zooming past the earth and it has high speed relative to the earth, right? People write in with relativity questions and they say, a spaceship is moving near Speed of light. And I say, you know, the speed of light relative to who, right? Relative to what? In this case, the spaceship is moving near the speed of light relative to the earth. The earth sees the spaceship's clocks as running slowly. That might make sense. People are cool with that. But then because it's symmetric, because the spaceship also sees the earth as moving near the speed of light, because hey, we just told you velocity is relative, right?

• 20:27Daniel Whiteson?

  That means that the spaceship sees the earth's clocks as running slow. And that's the amazing thing about special relativity. If you really grasp the relativity of velocity, it means that you can't have the same clock everywhere, that everybody doesn't have to agree about how time flows. I'm right that the spaceship's clocks are running slow. The spaceship is right that my clocks are running slow. That's both true, because we don't have to have the same story about what's happening in the universe. Special relativity tells us there's no absolute space. There's no absolute time. There is no absolute history of the universe. Boom.

• 21:02Kelly Weinersmith?

  Boom. Now, that does seem like a good place to start a movie or a sci fi novel. So I can see why this comes up so often.

• 21:08Daniel Whiteson?

  Right. So keep that in mind when we're later talking about whether potatoes can turn into black holes or what it's like to be a photon. But there is one thing in the universe which weirdly, amazingly, fascinatingly is absolute about the universe. And that's acceleration. So we started with location. That's just like, where are you relative to some arbitrary grid? Where you anchor it at some object, you know, distance from my coffee cup or distance from my toes or distance from the center of the sun. That's location. Velocity is how is your location changing? Acceleration is how is your velocity changing? So for the math nerds out there, we're now two derivatives in, right? Velocity is the slope or derivative of your location.

• 21:50Daniel Whiteson?

  If you're plotting where is your location versus time, then velocity is the slope of that plot. If you then plot your velocity, acceleration is the slope of the velocity plot. So it's just like, how much is velocity changing? Velocity is how much is location changing?

• 22:04Kelly Weinersmith?

  Got it. I kind of liked calculus.

• 22:09Daniel Whiteson?

  I love the connection between calculus and physics, right? Like, knowing calculus makes physics so simple and straightforward. You're like, oh, acceleration is just the derivative of velocity, which is just the derivative of location. So I can just like derive my equations of motion from one fact, like a constant acceleration, boom, I know the acceleration's a motion. Just integrate twice to get the position. Boom, you're done.

• 22:31Kelly Weinersmith?

  Elementary.

• 22:35Kelly Weinersmith?

  Maybe not quite that easy, but.

• 22:36Daniel Whiteson?

  I had this great moment because my son is taking physics right now, and he's also taking calculus. And so he knows these tools and he was learning about equations of motion. And I was like, dude, you can just integrate this twice and get that answer. And he was like, oh, and that's why it's one half at squared. I get it. Cool. And he had this like moment where I clicked in his mind. And I was like, dude, math and physics dancing together to explain the universe.

• 22:59Kelly Weinersmith?

  Oh, that must have been a proud moment as a father to be able to observe that.

• 23:04Daniel Whiteson?

  It was 20 years in the making, but it was cool.

• 23:06Kelly Weinersmith?

  Sometimes you gotta wait a long time for the payoff, but you got there.

• 23:09Daniel Whiteson?

  But the amazing thing about acceleration is that it is absolute. It's the one thing which does belong to you, right? Your location is relative. It's a property of a pair of objects. Your velocity is relative. It only has meaning in relation to something else you're measuring with respect to. Acceleration is something you own. Your acceleration is just your own. You don't need to measure it relative to anything else. And this is Einstein's famous thought experiment, right? In a box, you can't tell where you are or how fast you're going, because those things only have meaning relative to stuff outside the box. But inside the box, you can measure your acceleration.

• 23:45Kelly Weinersmith?

  My first question is, so is it because the reference point is now what you were doing like a second ago? And because that's like an internal comparison, that's why it's not relative? Silences, I always think, was this a great question or a really dumb question? Daniel was trying to figure out, how do I not insult Kelly's intelligence?

• 24:02Daniel Whiteson?

  No, not at all. The fun moments for me in teaching are hearing somebody's question and then trying to work backwards to what is going on in your mind that made you ask that question so that my answer is most helpful. And for me, like, that's the fun part about teaching. That's always the puzzle.

• 24:18Kelly Weinersmith?

  I enjoy giving you lots of those opportunities, Daniel.

• 24:24Daniel Whiteson?

  You know, it's a really amazing property of the universe. And it's not something I think we understand philosophically. It's just something we observe. Like, this is our description of the universe as we experience it. We know that you cannot measure your velocity or your location, but you can measure your acceleration. So fundamentally, this is a description of something we see in the universe. And this is one of those moments where you can say, okay, this is the description of the universe. What does it mean about the universe that velocity is relative and acceleration is not? And it's actually one of the connections to general relativity, because acceleration can be seen as equivalent to curvature. Acceleration has all the same effects on the motion of an object as curvature.

• 25:06Daniel Whiteson?

  In fact, we describe curvature sometimes as a pseudo-force, right? That's what gravity is. Curvature is gravity, and gravity is a pseudo-force that generates apparent acceleration. So that's actually a much more complex topic and connects special and general relativity. So I think for the purposes of today's conversation, let's just say this is something we observe in the universe and that we do our best to describe it. And I think the best way to get your handle on intuition for acceleration is to imagine like, well, how would you measure it? I told you, you can't measure your velocity except relative to other stuff. And you can imagine like being in a box flying through space where you don't have access to anything outside. How would you measure your velocity? There's no experiment you can come up with that can measure your velocity, because you need access to stuff outside,

• 25:50Daniel Whiteson?

  because that's the only way to define your velocity. But you can measure your acceleration inside that box.

• 25:55Kelly Weinersmith?

  And how would I do that? Like, say I had a, I was standing in there with a ball. Would that help me?

• 25:59Daniel Whiteson?

  Yes, absolutely. Just drop the ball. See what happens, right? Now, if you're not accelerating, the ball will just hang there with you. If you are accelerating, then the ball will move, because there'll be a pseudo-force generated by your acceleration. And we do this all the time. You feel this every time you drive somewhere, right? If you're driving the car and somebody hits the accelerator, right? Then what happens? You feel pressed back into your seat. If you dropped a ball right then, the ball would fly backwards. If somebody hits the brakes, which is also an acceleration, then you feel pushed forward, right? There's a pseudo-force there as you're pushed. If you dropped a ball, it would fly forwards. Right? The reason you have a seatbelt is because of this effect. So it's very easy to tell whether you're accelerating.

• 26:42Daniel Whiteson?

  Just bring a ball or bring a scale, right? A scale, it literally is measuring acceleration. That's why, for example, when you stand on a scale in space, you measure nothing because you're in free fall. There is no acceleration. Whereas if you stand on the surface of the earth, you do measure acceleration. You're measuring the earth accelerating up and out to keep you from falling towards the center of the earth.

• 27:04Kelly Weinersmith?

  Well, we are recording this pretty close to the end of the holidays, so I'm going to stick with the ball instead of the scale. Let's take a break. And when we get back from the break, we are going to talk about whether or not potatoes turn into black holes if they're going fast enough.

• 27:28Speaker 01

  That sound? That's the National Squash League. Pro teams, the world's best players, and rallies so fast you'll forget to breathe. Season four is in full swing, and every match streams free on YouTube. Big hits, bigger rivalries, and a front row seat from wherever you are. Watch every match for free on YouTube. Search National Squash League and hit subscribe or follow live updates on Instagram at NSL.Sport.

• 27:56Daniel Whiteson?

  Hey, it's Nile Rodgers, host of Before the Moment, a Lincoln original series. I'm driving across the country, meeting some of today's most fascinating artists. We're exploring the stories before the moment that changed everything. This week, I'm joined by my friend, John Ledge. How does music actually enter your mind? I'm not sure why or how the music comes to me, but I think people who love music and write music, our brains- Things are just filled with music. Right. Like, we have listened to so much music. We've been a part of so much music. I think of the story that I want to tell, the mood that I want to create with the music. Start playing chords, see where they lead me.

• 28:40Daniel Whiteson?

  Sometimes I'm just not even thinking about music, right? And I hear this little thing and I go, oh, that could be this. You know, you just have to be ready for when the inspiration hits. It comes. Yeah. Experience before the moment. The Lincoln Original Series on the iHeart Radio app, YouTube, or wherever you get your podcasts.

• 29:03Speaker 01

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• 29:40Kelly Weinersmith?

  Okay, Daniel, so here's my question for you. Do things change their mass as you approach the speed of light?

• 29:48Daniel Whiteson?

  Yeah, right. And this question was inspired by a listener who wrote in and heard on another podcast that potatoes, if they approach the speed of light, would turn into black holes. And like, I won't comment on whether you might turn into a black hole if you eat too many potatoes after the holidays, but I do want to dig into this question of what happens to a potato. I hope immediately your eyebrows scrunch up when you hear this question, because even the question like, what happens to a potato when it approaches the speed of light? You might think like, well, the speed of light relative to what, right? Because velocity is not the property of a potato. So it doesn't make sense to even talk about a potato having a speed. Is it moving at that speed relative to the earth, relative to a spaceship, relative to some particle? The question itself already doesn't make sense.

• 30:33Daniel Whiteson?

  And that tells you that the answer can't be yes.

• 30:35Kelly Weinersmith?

  And we're done.

• 30:37Daniel Whiteson?

  I mean, for example, like, take a potato, maybe you have a potato in your kitchen. What is the velocity of that potato? Well, it's moving at zero relative to your kitchen, probably. It's already moving near the speed of light relative to anything that's moving towards the earth and near the speed of light. And there's lots of stuff moving towards the earth at near the speed of light. There's particles shooting from space at super high energies at 99.999999% of the speed of light. Your potato is moving near the speed of light relative to that particle. Is your potato a black hole? No. Everybody who has a potato is doing this experiment right now. So we know your potato is not turning into a black hole.

• 31:18Daniel Whiteson?

  And the amazing thing about black holes is that they are observer independent. Some of the things we talked about earlier are observer dependent. Like, I see your clock is slowing down if I see you moving quickly. And that's observer dependent because it depends on my velocity relative to you. But black holes are not observer dependent. They exist in every frame if they exist at all. So it's not like I can see the potato as a black hole because it's moving fast relative to me, but you don't see the potato as a black hole because it's sitting next to you. Everybody has to agree whether it's a black hole or not.

• 31:53Kelly Weinersmith?

  So if we assumed that when they were talking about the speed of the potato, it was relative to earth, does that solve it because we all have the same frame of reference?

• 32:01Daniel Whiteson?

  No, because you can always postulate some observer moving with the potato.

• 32:04Kelly Weinersmith?

  Somewhere else.

• 32:04Daniel Whiteson?

  Yeah, exactly. And there's always some particle there to do that observing. And the root of this comes from a historically sort of fascinating idea about mass. You often hear that mass increases as you approach the speed of light. And again, I hope your ears turn up at that and go like, hmm, who's measuring the speed in that case? And though this is often quoted, it makes little sense, right? Because it doesn't make sense for mass to be observer dependent. If you're moving past me near the speed of light, does it make sense for me to measure mass as larger than somebody else to measure your mass, right? Mass can't be observer dependent if it has consequences like if you have enough of it, you turn into a black hole, right? And we know that's not a

• 32:47Daniel Whiteson?

  Observer dependent. So what's going on here is an old concept in relativity, which you're sort of picked up on and propagated and been repeated over and over and over again, even though it doesn't really make much sense.

• 32:59Kelly Weinersmith?

  What is the old idea that's being repeated?

• 33:01Daniel Whiteson?

  So this is basically all Einstein's fault because when Einstein was developing relativity, he had to think about like how some of these basic concepts change in this new notion, in this new perspective of the universe, right? And so he was thinking about speed and momentum and energy and mass. And you know, some of these things are the same for Newton and some of these things are different. Right? Velocity is similar, but it has a maximum value now. And so that changes. And what does that mean about changing energy and changing momentum? Because like energy doesn't have a maximum value. You can have an infinite amount of energy, even if your speed only approaches a certain value. So like the relationship between these quantities have to change. And so Einstein had to reimagine what these quantities were.

• 33:44Daniel Whiteson?

  And for a moment, he came up with this idea of relativistic mass, saying like, well, let's treat an object as if it had more mass if its velocity is greater. And so in his early writing, he came up with this concept and he wrote the equations for mass increasing with velocity.

• 34:01Kelly Weinersmith?

  So anyone who was confused a moment ago about whether or not mass changes with velocity can feel good knowing that Einstein was making the same mistake.

• 34:08Daniel Whiteson?

  Yes, exactly. And you know, it's fair, like you're exploring these new concepts. You're wondering like, how do we generalize? We went from one idea to another. What gets changed? What doesn't get changed? What's the most sensible way for things to change? And it's fine for your first idea to not be the best idea. The problem with relativistic mass is that it doesn't really make sense and it's not really necessary. Doesn't really make sense because it means that your mass now depends on your velocity. So like the potato would have more mass or less mass based on who's measuring it. And also it would have different masses in different directions, right? Like what does happen to the potato as we see it approach the speed of light relative to us is that it gets harder to accelerate in one direction and not in others.

• 34:54Daniel Whiteson?

  Like if the potato is already going at 99% of the speed of light as it whizzes by us, then it's harder for us to increase its velocity in the direction it's already moving. Right? Because it's already going near the speed of light in that direction. It's easier for me to push it perpendicular to its motion because it's not already moving at a very high velocity.

• 35:13Kelly Weinersmith?

  It's easier for you to push it perpendicular because it's not already moving at a high velocity.

• 35:17Daniel Whiteson?

  Yeah. So in relativity, velocity has this weird maximum, right? Nothing can go faster than the speed of light relative to anything else. And as you approach the speed of light relative to something, you can pour additional energy into that object. You can give it a push without increasing its velocity as much. Like if I apply the same force to a potato that's at zero meters per second relative to me, it's going to speed up. And if I apply that same force to a potato that's already 99.99% of the speed of light relative to me, it's not going to speed up as much. There's just like not room for it to speed up as much. So I can pour energy into it without getting the same velocity return.

• 35:56Kelly Weinersmith?

  Sure. But what was the perpendicular part?

• 35:59Daniel Whiteson?

  So if you try to think of that as, oh, the potato has additional mass. It's harder to accelerate because it's more massive. Then you might think initially, okay, that makes sense. I can describe this as additional mass. It's harder to accelerate the potato if it's always already going really fast. So the same force doesn't give the same increase in velocity. That kind of makes sense, right? Except it only makes sense in the direction the potato is going. Because the potato can have no velocity in other directions, right? So I'm free to apply a force to the potato in another direction and I get the same boost as I always did. And so now the potato has to have like a mass in this direction because it's hard to speed it up in that direction and a mass in other directions where it's easier to speed it up.

• 36:43Daniel Whiteson?

  And so now mass has to have like directionality to it, right? Instead of just being like a property of the object.

• 36:51Kelly Weinersmith?

  I feel like I just felt the pieces click like in my head there. Okay, let's keep going.

• 36:55Daniel Whiteson?

  And so there is a way that could make sense if you're willing to have mass be this weird directional thing. But Einstein was like, okay, actually this doesn't make any sense. And you don't need it because you already have a concept of energy. The total energy of the object already captures this behavior. So you don't need this new weird directional relativistic. Mass, it doesn't give you anything, it doesn't help you at all. Let that be part of energy. And then Einstein and others decided, well, let's just keep mass to be a number. And it'll be the amount of energy something has when it's at rest. So it's like the rest energy of the object. And that makes it invariant, because you defined it to be the amount at rest. And so this is what we call invariant mass, and it means that energy is now nicely broken up into two parts.

• 37:40Daniel Whiteson?

  The energy you have at rest, which we call the invariant mass. So take for example, an electron. It has a mass even if you're holding it in your hand, right? That's what we call the invariant mass. That's the rest mass of the object. And it can also have energy if it's in motion. So that's its momentum. So energy now has two components, the rest mass, the invariant mass, and the motion part, right? The energy of its motion. So those are two separate things, and the invariant mass, by definition, doesn't grow with velocity because you measure it when it's at rest. So you might think, hmm, that's just defining stuff. You're just defining it to be invariant.

• 38:15Kelly Weinersmith?

  Physics tricks.

• 38:15Daniel Whiteson?

  Yeah. Yes, that's true. We're defining it to be at rest. But that's really what mass is, and we're free to invent these quantities to be useful and to make sense to us, because hey, we're the audience of it, right?

• 38:26Kelly Weinersmith?

  Right. We're creating tools that help us with stuff, so why not?

• 38:29Daniel Whiteson?

  Yeah. And if you're following along, remember, our original question is, does a potato turn into a black hole near the speed of light? And our answer so far is, let's be careful when we talk about energy of mass and energy of momentum. Energy momentum is relative, energy of mass is not. So listeners following along might be like, okay, Daniel's told us about the definition of energy and how it might be mass and how it might be momentum. But in general relativity, we know that curvature of space depends just on energy, right? It doesn't depend only on mass. It depends on more complex notions of energy, because like photons can help bend space and they have no mass. So why don't potatoes create enough curvature, if they have enough velocity, if they have enough momentum?

• 39:14Daniel Whiteson?

  Why can't that energy density then create black holes? And I have two answers to that. One is, this is a really, really complicated calculation to do, because In general relativity, it's not just like a number. It's not like Newton's gravity where you have mass and more mass means more gravity. Einstein's equations are tensor equations, which means they're matrices. There's all sorts of complicated stuff and different kinds of energy enter in different ways. So, energy of mass enters differently from energy of velocity. And so, it's a really complicated calculation. And we know that the answer has to be the same for a potato at rest and a potato in motion, because black holes are not observer-dependent. That's just like a bedrock fact in general relativity.

• 39:56Daniel Whiteson?

  So, instead of doing a really complicated calculation where the potato is in motion, we know we'll get the same answer when the potato is at rest. And if the potato at rest doesn't give you a black hole, then the potato in motion can't give you a black hole. And I can't go through all the complicated math here on the podcast, but that's the sort of the end run around having to do all that math. We know a potato can't turn into a black hole if it's not already a black hole in your kitchen.

• 40:20Kelly Weinersmith?

  So, I don't have to live in fear of my potatoes. That is a relief.

• 40:26Daniel Whiteson?

  Well, potatoes can hurt you in lots of ways, but they're not going to turn into black holes.

• 40:30Kelly Weinersmith?

  That's right. All right, so we have struck down one misconception about potatoes and black holes, which I'm sure everybody woke up this morning thinking that they'd hear about potatoes and black holes. When we get back, we're going to ask, do photons experience time?

• 40:54Speaker 01

  That sound? That's the National Squash League. Pro teams, the world's best players, and rallies so fast you'll forget to breathe. Season four is in full swing and every match streams free on YouTube. Big hits, bigger rivalries, and a front row seat from wherever you are. Watch every match for free on YouTube. Search National Squash League and hit subscribe or follow live updates on Instagram at NSL.Sport.

• 41:23Speaker 01

  Hey, it's Niall Rogers, host of Before the Moment, a Lincoln original series. I'm driving across the country, meeting some of today's most fascinating artists. We're exploring the stories before the moment that changed everything.

• 41:39Daniel Whiteson?

  This week, I'm joined by rising star Sienna Spider.

• 41:43Kelly Weinersmith?

  I love the 60s. I feel really jealous that I wasn't alive for it. I'd be interested, like, knowing what that was like and seeing the way culture and art has progressed today. How do you find it?

• 41:52Daniel Whiteson?

  Wait a minute.

• 41:53Kelly Weinersmith?

  Sorry, I have so many questions. Sorry.

• 41:56Daniel Whiteson?

  You're not nervous, are you?

• 41:57Kelly Weinersmith?

  I am nervous.

• 41:58Daniel Whiteson?

  You are?

• 41:58Kelly Weinersmith?

  I am. I feel, like, insecure about my experience. I know I shouldn't, but, you know, I'm 20. I haven't really lived my life yet. And then sitting in front of somebody that has lived an enormous life is intimidating. And sometimes I feel like talking about myself is just not as interesting. So that's why I feel a bit nervous. I'll try and ignore it, then.

• 42:18Daniel Whiteson?

  Please do. Experience Before the Moment, a Lincoln original series on the iHeart Radio app, YouTube, or wherever you get your podcasts.

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• 43:07Kelly Weinersmith?

  All right, Daniel. You know, I've often heard it said that light doesn't experience time. Is that right?

• 43:18Daniel Whiteson?

  Have you heard it said that photons experience our podcast and enjoy it? Are they faithful listeners?

• 43:23Kelly Weinersmith?

  I mean, Daniel, how could they not? Right? Everything from superorganisms down to the smallest particles enjoy D K E U. How could they not?

• 43:32Daniel Whiteson?

  Exactly. And we're so good-looking, right? And what do photons do if not appreciate our looks, right?

• 43:38Kelly Weinersmith?

  Sure. I think we're getting on some thin ice here, but let's move forward.

• 43:43Daniel Whiteson?

  All right, before we undermine our credibility too far. Yes, this is something you see in popular science all the time. Photons fly through the universe, not experiencing time. So let's try to understand where this comes from. And then let's talk about what we actually know about it.

• 43:58Kelly Weinersmith?

  All right, where does this come from?

• 44:00Daniel Whiteson?

  So it's a not unreasonable extrapolation of what we know about special relativity. We say that moving clocks run slow. So I put Kelly and her potato on a spaceship with a clock. And I tell them to accelerate. They're going now near the speed of light relative to me. I look at their clock through a telescope. I see that it ticks more slowly than a clock sitting next to me. So I have two clocks. One has no velocity relative to me, taking one second per second. And Kelly's clock near the speed of light relative to me, ticking at one second per year or something. And that's cool. That's fascinating. That's amazing, right?

• 44:36Kelly Weinersmith?

  Whoop. Though I'll note, if you have Kelly and a potato, pretty soon you're only going to have Kelly. But, but all right, fascinating and amazing.

• 44:43Daniel Whiteson?

  Yeah, and special relativity tells me how to calculate that. It says, okay, Kelly's moving fast. I can calculate how quickly her clock is ticking. And I can also go to Kelly's reference frame, because Kelly has a reference frame. She has a potato, she's a clock. She is sitting in her spaceship, sipping her coffee. I can go from her reference frame to my reference frame. And that's really the core of special relativity is it tells you how to translate from one reference frame to another, right? I create mine. We said there is no absolute space, but I can create a reference frame and say, here's my origin, here's location equals zero, here's location equals one. I can measure location and velocity relative to my reference frame. Like if we spent a zillion dollars building your grid, that would be Kelly's reference frame. It wouldn't be special or absolute in any way, but it'd be yours and it'd be wonderful,

• 45:28Daniel Whiteson?

  I'm sure.

• 45:29Kelly Weinersmith?

  That would make it special.

• 45:32Daniel Whiteson?

  It'd be special to me and special to you, but not special to the universe. All right, they wouldn't change the laws of physics in any way. And so I have a reference frame, you have a reference frame. And special relativity tells us how to transform between these different reference frames. And special relativity tells us that as the velocity of two reference frames grows to near the speed of light, which is the maximum, the time that they see each other's clock Ticking goes to zero. If you're at 99% of the speed of light, I see your clock ticking at like one second per day. If you go to 99.99% of it, I see your clock ticking as one second per year. If you go at 99.9999999 whatever percent of the speed of light, maybe I see your clock ticking

• 46:13Daniel Whiteson?

  one second every thousand years. So it's tempting to extrapolate this and say, well, what happens if you go at the speed of light? Do I see your time as stopping? That's where this comes from because photons, we know, move at the speed of light. And so people imagine, okay, put a photon in a spaceship. Take that spaceship to the speed of light. If the photon has a little clock next to it, what does that clock read? Well, it's very tempting to say at the speed of light, time stops.

• 46:40Kelly Weinersmith?

  All right. So is this going to be a speed of light relative to something? I'm not going to try to jump the gun. What do we talk about next, Daniel?

• 46:48Daniel Whiteson?

  So it's very fun to say that time stops with that photon, but it's not really true because that photon doesn't have a reference frame, right?

• 46:55Kelly Weinersmith?

  Oh, that's what I was trying to get at. I'm brilliant. All right. Sorry. Go ahead. PhD in physics.

• 47:00Daniel Whiteson?

  Yeah, because photons don't have a reference frame. Photons move at the speed of light relative to every observer. So I see them move at the speed of light. You see them move at the speed of light. You have this confusing scenario where you're in your spaceship, moving really fast. You turn on a flashlight. You see the photons moving relative to you at the speed of light. I see the photons moving relative to you at the speed of light, even though I also see you moving at 99% of the speed of light. It's very confusing. But the thing about photons, the reason they move at the speed of light relative to everybody is that you can never catch them. You can't like zoom up next to a photon and say like, hey, look, there's a photon, the way you can relative to a potato, for example, or relative to Kelly's ship. This weird fact that two observers always see light

• 47:41Daniel Whiteson?

  moving at the speed of light, even if they have a high velocity relative to each other, this is not like a little detail. It's the whole foundation of special relativity. From this one fact and the assumption that the laws of physics are the same everywhere, you can derive all of special relativity, time dilation, length contraction, Lorentz transformations, all of that depends on this.

• 48:03Daniel Whiteson?

  Why is that the case? Why is there a universe this way? Well, we aren't actually sure, but it is an observed fact. We have verified with experiments and everything flows from it. And it has all of these weird consequences, including that you can't catch up to a photon. You can't ever join a photon in its reference frame and say, hey, what's it like to be a photon? And that's kind of the short answer is that photons have no reference frame. And so it makes no sense to say, what does a photon experience? Does a photon experience time? Photons don't experience anything the way like lumps of coal don't have political views. Right. It's sort of like a category error to even ask the question, unfortunately.

• 48:45Kelly Weinersmith?

  Okay, I'm taking a second to wrap my head around the fact that photons have no reference frame, because essentially for any reference frame you pick, they're always moving at the speed of light.

• 48:55Daniel Whiteson?

  Yes, exactly. In special relativity, this calculation on which this whole idea is based can only translate between reference frames. It says my potatoes reference frame, Kelly's reference frame, my coffee's reference frame, my cat's reference frame. I can tell you how clocks in any of those reference frame appear in my reference frame. Or I can tell you how my clocks appear in those reference frames. But photons don't have a reference frame. There is no axes moving with the photon where the photon is at rest. There is no special set of buoys for that photon that move along with it where it has no velocity. Right? No matter what set of buoys you build, photons will always be moving at the speed of light relative to those buoys. So there is no reference frame. So you can't use special relativity to calculate what it like to be a photon.

• 49:40Kelly Weinersmith?

  I think my brain feels like physics should be intuitive because I exist in this universe and feel like I understand it. But the more I talk to you, the more I feel like it's not necessarily intuitive, which makes it all the more amazing that we have figured it out. And so I totally get why people jumped to photons don't experience time because intuitively that does feel right to me. I'll be sleeping tonight thinking about photons not having a reference frame.

• 50:05Daniel Whiteson?

  Yeah.

• 50:05Kelly Weinersmith?

  Is this intuitive to you or is this, it makes sense now because you've been thinking about it for so long?

• 50:10Daniel Whiteson?

  It makes sense mathematically. Intuitively, it's always a struggle to make sense of the universe. The way I think about it is that there's a very tempting intuitive path, which is wrong, which is to think about photons as the extrapolation of what happens when you go really, really fast because they're moving at the speed of light and we can go almost to the speed of light. And so it seems like they're right there, like at the end of that curve, right? But they're not. They're really in a different category. So even though you might want to organize them at like, at the end of that curve, they're similar to a spaceship moving really, really fast. They're not. They're really in a completely different regime because they have no mass, right? So you can't like build a clock in this photon's reference frame.

• 50:51Daniel Whiteson?

  You can't build a clock out of pure photons. There's nothing it's like to be a photon. It's really a completely different kind of object than anything that does have mass. So think about two different categories. Has mass, doesn't have mass. Special relativity can tell you about the experience and how time clicks for anything that has mass. Anything that doesn't have mass, there's no reference frame there. So special relativity has no handle on it. It can't tell you at all what it's like to be a photon. Does that mean photons don't have an experience? You know, maybe alien philosophers, when they come and they tell us about how the universe works, will have some way of thinking about what it's like to be a photon. You know, the way Thomas Nagel struggled with what it's like to be a bat. I don't want to totally rule it out. And, you know, maybe there are crazy aliens

• 51:35Daniel Whiteson?

  out there whose minds are just made out of photons somehow, or ripples in electromagnetism. And so I don't want to piss them off either.

• 51:43Kelly Weinersmith?

  You're really hedging your bets here, Daniel.

• 51:46Daniel Whiteson?

  Hey, you know, like at the beginning of the podcast, we've got to be open minded and we don't want to be full of hubris and declare that we know everything about the universe. So I think the crispest thing we can say is that special relativity can't say anything about what it's like to be a photon. It certainly doesn't tell us that photons experience zero time. And you know that already because if you take that idea to its logical conclusion, then there's all sorts of confusing contradictions. Like a photon that's emitted instantly is across the universe, right? Like, doesn't that feel like it violates all sorts of principles and transformation of information? And you get quickly into paradoxes and confusion about causality. It really doesn't make sense at all. And for those of you who are students of special relativity, photons do take time to fly through

• 52:31Daniel Whiteson?

  the universe. They have this thing called a spacetime interval, which is zero, which just means that they follow the shortest path through spacetime. But they still take time to move through space. And so, you know, special relativity is our best description of how space works. And it tells us a lot about the nature of space and the nature of velocity and the nature of acceleration even. But it doesn't tell us what it's like to be a photon.

• 52:54Kelly Weinersmith?

  Got it. All right. Just like we'll never know what the bees see with the colors that they can see and we can't. We'll never know what it's like to be a photon. I gotta be honest, I'm a little sad that I'll never know what it's like to be a bee, but I can live without knowing what it's like to be a photon. But maybe this is a fundamental difference between biologists and physicists.

• 53:10Daniel Whiteson?

  But hey, if you're a photon and you've been listening to this podcast and we offended you, write in. Tell us, what is it like to be a photon and be pissed off at the podcast? I want to know. Also, if you're a bee, write in, because Kelly wants to hear from you.

• 53:24Kelly Weinersmith?

  That's right, and we'll have you on the show.

• 53:25Daniel Whiteson?

  And if you're not a photon and you're not a bee and you're somehow a human listening to this podcast, we still want to hear from you. Did this make sense to you? Did this help you understand why potatoes are not black holes and what it's like to be a photon? Did we just confuse you? Send us some feedback. Send us some love. Send us some grumpy emails, whatever. We love to hear from you. Write to us to danielandkelly.org. Don't send hard physics questions to danielandkelly.com. I don't think they know the answers.

• 53:52Kelly Weinersmith?

  They might just might not appreciate it. A lot of work goes into planning a wedding. They're very busy people.

• 53:56Daniel Whiteson?

  That's right. Yeah, exactly. They got a full spreadsheet. They don't need your question on top of their to-do list.

• 54:02Kelly Weinersmith?

  Good luck, Daniel and Kelly.

• 54:04Daniel Whiteson?

  Congratulations.

• 54:12Kelly Weinersmith?

  Daniel and Kelly's Extraordinary Universe is produced by iHeartRadio. We would love to hear from you.

• 54:17Daniel Whiteson?

  We really would. We want to know what questions you have about this extraordinary universe.

• 54:23Kelly Weinersmith?

  We want to know your thoughts on recent shows, suggestions for future shows. If you contact us, we will get back to you.

• 54:30Daniel Whiteson?

  We really mean it. We answer every message. Email us at [email protected].

• 54:36Kelly Weinersmith?

  Or you can find us on social media. We have accounts on X, Instagram, Blue Sky, and on all of those platforms you can find us at D and K Universe.

• 54:46Daniel Whiteson?

  Don't be shy. Write to us.

• 54:53Speaker 01

  That sound? That's the National Squash League. Pro teams, the world's best players, and rallies so fast you'll forget to breathe. Season four is in full swing and every match streams free on YouTube. Big hits, bigger rivalries, and a front row seat from wherever you are. Watch every match for free on YouTube. Search National Squash League and hit subscribe or follow live updates on Instagram at NSL.Sport.

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• 55:51Daniel Whiteson?

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  Don't share needles or pens, or reuse needles. Don't take if allergic. Or if you or someone in your family had medullary thyroid cancer, or if you've had multiple endocrine neoplasia syndrome type 2, tell your doctor if you get a lump or swelling in your neck. Stop Zepbound and call your doctor if you have severe stomach pain or a serious allergic reaction. Severe side effects may include inflamed pancreas or gallbladder problems. Tell your doctor if you experience vision changes before scheduled procedures with anesthesia. If you're nursing, pregnant, plant to be, or taking birth control pills. Taking Zepbound with a sulfonylurea or insulin may cause low blood sugar. Side effects include nausea, diarrhea, and vomiting, which can cause dehydration and worsen kidney problems. Talk to your doctor.

• 57:15Daniel Whiteson?

  Call 1-800-545-5979 or visit zepbound.lily.com. This is an iHeart Podcast. Guaranteed Human.