Daniel and Kelly’s Extraordinary Universe - What if the speed of light were slower?

Episode Date: April 11, 2022

Daniel and Jorge answer listener questions about ice ages, black holes and the speed of light. Learn more about your ad-choices at https://www.iheartpodcastnetwork.comSee omnystudio.com/listener for privacy information.

This is an I-Heart podcast. December 29th, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System

On the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want or gone.

Hold up. Isn't that against school policy? That seems inappropriate. Maybe find out how it ends by listening to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. Why are TSA rules so confusing? You got a hood of you. I take it all. I'm Mani. I'm Noah. This is Devin. And we're best friends and journalists with a new podcast called No Such Thing, where we get to the bottom of questions like that. Why are you screaming it?

I can't expect what to do. Now, if the rule was the same, go off on me. I deserve it. You know, lock him up. Listen to No Such Thing on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. No such thing. Do we really need another podcast with a condescending finance brof trying to tell us how to spend our own money? No, thank you.

Instead, check out Brown Ambition. Each week, I, your host, Mandy Money, gives you real talk, real advice with a heavy dose of I feel you, sis, like on Fridays when I take your questions for the BAQA. Whether you're trying to invest for your future, navigate a toxic workplace, I got you. Listen to Brown Ambition on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. Hey, Jorge, when did you move to California? Ooh, it was a long time ago. So was it like before or after the last ice age?

How old do you think I am, Daniel? Or do you mean like the time that the temperature dropped below 60 degrees here in Los Angeles? We call that the California Ice Age. Well, I mean, that begs the question. Did you move to California for the weather? Kind of. I mean, I moved here for grad school and I actually had to choose between Stanford and Berkeley. Is there much of a weather difference on the other side of the bay?

There is, actually. There's a big difference, at least on the day that I made the decision. and it was much sunnier at Stanford. I see. So you're saying Berkeley is cooler. I'm saying Berkeley is icier and more frigid. Well, everybody who went to Stanford is definitely hot. Yeah, it's a hot place.

Hi, I'm Horham A cartoonist and the creator of PhD comics. Hi, I'm a cartoonist. I'm a particle physicist and a professor at UC Irvine, and I will always support Berkeley over Stanford. Ooh, what about Berkeley over Irvine? Don't make me go there, man. Are you pro, what is it, Ardvarks or Bears? Like, which one would win in a fight, do you think?

A bear or an art vart? Well, bears sleep a lot, so I think, you know, while they're snoozing, the ardvark could just, like, slip in there and lick their face with its long tongue. Anyway, it's an ant-eater, not an artwork. Oh, right. Is there a difference? Is there a difference?

Oh, my gosh. Welcome to Creature Feature, the podcast about Hard Marks. Yeah, and or college mascots, one of the two. But anyways, welcome to our podcast, Daniel and Jorge, Explain the Universe, a production of I-Hard Radio. In which we take you on a tour of the universe, regardless of where you went to college or if you went to college, the goal of this podcast is to get everybody on board with this journey of exploration,

to wonder how the universe works, how it might have been, why it is the way that it is, and can it make sense to all of us? That's right, because it is a pretty mysterious universe full of interesting phenomena for us to look at and gape and wonder about and very importantly ask questions about. I have a question for you,

which is, you know, if Berkeley is the golden bear and Irvine is the anteater, what is Stanford's mascot? Is it a tree? It's Silicon Valley money, I think. Piles of cash. Yeah, piles of Bitcoins probably these days.

Yeah. Well, we're not going to let this go, are we? The Stanford Berkeley thing on this episode. Oh, no, and Berkeley over Stanford all day, every day. Maybe we should discuss our after grad school school. So I went to Caltech and you went to UC Irvine. After grad school, I actually went to University of Pennsylvania, which is a private school. And yeah, then I did go to UC Irvine.

And I've bounced back and forth between public and private institutions. But in the end, my heart really is in public institutions because they say, serve the public. And to get out the jokes for a moment, like I really do believe in the mission of educating the public and providing a path of mobility for people. The California public college system from the Cal States all the way up to the University of California's, they do an incredible public service. And I think that this podcast is part of that. We want to reach out and educate everybody about the mysteries of the universe, not just those that have piles of cash or stacks of Bitcoin. Yeah. And that's why you renounced your undergraduate institution, right?

No comment? I'm just kidding. But it is a pretty amazing universe full of things to discover that are there for everyone to wonder and to look at it and to have questions about because people have questions. People do have questions and they write to us with their questions. And the cross-section of folks who write to us is just incredible. From seven-year-old wondering about black holes to night guards at hospitals who listen to our podcast while they walk the halls to pro bono attorneys from Alabama who listen to our podcast is a break from the craziness of their lives. Everybody out there wonders about the nature of the universe and how it works and whether it's possible for it all to make sense to

them. Yeah, that is pretty incredible to think that there are so many people listening to this and kind of thinking about the same topics at the same time. It makes us all sort of feel connected in a way. Like we're all wondering about the universe at the same time together. Yeah, we are all wondering about the universe. And I hope that means that we're also connected to like alien scientists who I think are probably wondering about the same universe. I like to fantasize about a whole galactic community of scientists wondering about the nature of this crazy cosmos. And we're just a tiny little piece of it. Well, I feel like you just stepped it up the notch of there. I was going for some sort of human grandeur, but you took it to the galactic level. Oh, that's what we do on this

podcast, man. Take it to the galactic level every time. I don't know if I want to mind melt with aliens necessarily, though. Do you think we've enjoyed that experience? Well, you know, that's sort of the Berkeley approach, you know, we're all one with the universe man. Do I have to take any particular substances to kind of reach that state that I can purchase maybe at Berkeley? Banana peels for sure, yeah. But yeah, people definitely have questions. And sometimes we get those questions here on the podcast.

People send them to us over email or through social media. That's right. So if you have questions about the nature of the universe or there's something we said on the podcast that you didn't quite understand or there's just been something bugging you that you really need to get explained. Please don't be shy. Write to us to questions at Danielanhorpe.com.

We answer every single question. We will answer your question. Yeah. And sometimes the questions are so interesting that Daniel picks them to answer on the podcast. Yeah. Sometimes the questions make me go off

and do a bit of a dive or research to get a solid answer. And sometimes I think it's a question that other people might want to hear the answer to. And sometimes I think, hmm, this would just be fun to laugh with Jorge about it.

Make fun of or to laugh about it? What are your plans here? Well, you know, I try to be nice to Stanford grads who, you know, went to a junior college after all. That's right, yes, who are not physicists, I guess. So today on the podcast, we'll be tackling. Listener questions, number 25, and also titled Horan Daniel, keep fighting about Berkeley and Stanford. You're the one who seems to be bringing it up more. No, I think that's probably true.

I think Berkeley folks probably feel the Berkeley Stanford. rivalry more than Stanford folks who are like, what? Who cares? Little academic chip on the shoulder, huh? I think so, probably. We're the public university that could. I think the more interesting question is, is an art bark the same as an ant eater? I think the question is, how did you get a Stanford education and not know the answer to that? Well, I was in the engineering department.

It didn't take zoology 101. Right. Don't you like look to nature for inspiration? Well, I felt like the straw was already invented, so I didn't need to, like, copy the ant-eater's trunk. Oh, I see. All right. That's true. To invent something, yeah.

And there's not much of a market for an ant-eating robot anyway, I guess. Or an ant-eating straw. But anyways, we're here to answer questions from listeners. And this is the 25th episode that we've done this. And I feel like we don't do this enough, Daniel. I really like these episodes. Oh, good. Well, let's do some more of them.

I think these are a lot of fun also. And today, we have a question inspired by one of our first. previous listener question episodes. Whoa, what? We're going inception here. We are deep diving like a question within a question episode. Yeah, well, that's the wonderful thing about questions is that the answers just raise more questions. They make people think in a way they hadn't before.

They make people's brains go places they hadn't gone before without needing to buy anything on Telegraph Avenue. Yeah. But that's optional, I guess. I mean, it might make the podcast actually more interesting to some people. Exactly. That's what we've been talking about bananas the whole time. But we have three pretty awesome questions here today from listeners, and they have to do with the Ice Age here on planet Earth

about how photons move near black holes, and also what would happen if the speed of light changed. So thanks to those listeners who sent in their questions, and also were willing to record their audio. And don't forget, if you have a question, you can also get an answer right to questions at danielanhorpe.com. All right, the first question we have here is, from Carson, who has a question about the Ice Age.

So I listened to the podcast about the asteroid and the dinosaurs, and I was wondering what would happen if the Ice Age hadn't happened. Thanks for answering all my questions. Pretty cool question. Thank you, Carson. I guess Carson has a question, kind of like a what-if question. Like, how different would the Earth be if certain things hadn't happened? Yeah, it's a really fun question.

And it gets to the heart of how our entire, existence depends on so many tiny little factors, just like if an asteroid hadn't hit the earth or if the earth hadn't warmed or cooled, so many chaotic events, which could have been different, were crucial to us being here right now. And so it's really fun to imagine alternative Earths, different scenarios, where things might have turned out very differently. Yeah, I think Carson just wants us to talk about dinosaurs. But, you know, you can't blame them. You know, what young person doesn't want to talk about dinosaurs. Yeah, or maybe Carson's thinking about where to go to college and is wondering, you know, like Berkeley, Stanford? I don't know. Why, you're really not

dropping this? Well, Carson, I have to tell you, if there is another ice age, Berkeley's going to freeze first before Stanford, just letting you know that it is a little bit more north and on the other side of the bay, which gets colder. And therefore, it'll have a larger snowpack and better water reserves that lasted through the summer. What? Because we're not next to the Bay area? I'm not sure where you're going with this. Sounds like Berkeley thinking to me. This question is really fascinating because there are a lot of connections between ice ages and the physics of the solar system. That is, you know, how the earth goes around the sun and the variations in the Earth's orbit really do have a strong impact on how much sun we get

and how much ice there is on the Earth. Yeah, it's pretty interesting the connection there. And it's amazing that Carson had been thinking about the ice age. I guess we've had several ice ages throughout the ages. We have had several ice ages. And if you cast your mind back like really deep far into the history of the Earth, it's incredible how different the Earth looked. Like around 650 million years ago, we were in the depths of an ice age so cold that they think that ice reached all the way down to the equator. Like it was basically a snowball Earth. Whoa. Yeah.

Like if you took a picture of it, you would just see a big white ball. Kind of like when you look at, you know, some of the ice planets. So if you're an alien scientist visiting Earth for an interstellar physics conference, and you arrived, you know, 600 million years too early, you wouldn't find anybody to talk to. And you would think, oh, that's just a frozen wasteland. Or you might think, great skiing here. Hello.

Yeah, I hope that one day we like unthaw some big block of ice and find an alien skier in it. That would be an incredible discovery. But then, you know, wouldn't their snowboards hover also? I mean, if they made it all the way here for a ski vacation. I wonder what would be in that flask. But anyways, ice ages are interesting, as you said, because they are connected to kind of the physics of our planet and the physics of our planet revolving around the sun. Like it's heavily tied to the orbit and the tilt of the planet, right?

There are a lot of factors that affect ice ages from climate to continental drift, all sorts of things. And scientists don't have a complete understanding of what causes these things. There are still lots of big open questions. But one thing that we do know is that changes in how the. the Earth orbits the Sun, for example, whether the Earth's orbit is circular or whether it's become more elliptical and changes in the Earth's tilt, these things can affect how much solar radiation falls on the Earth, and that affects the temperature for sure. Wow. Well, first of all, I guess maybe this is something I hadn't thought about is, is the Earth's orbit

not constant? Isn't it like a perfect circle or slight oval? And are you saying there's some variations in that trajectory? There are definitely variations in that trajectory. And it goes from being like almost a perfect circle to being more elliptical. And it becomes elliptical by having the semi-minor axis get a little shorter. So it's not like the Earth gets further from the Sun, but during parts of its orbit, it then gets closer to the Sun. Wait, what? So what determines these changes in our orbit? So if the Earth was alone in the solar system, it would have a very simple, stable orbit around the Sun. But it's not. And there are other things in the solar system, Like Jupiter and other gravitational bodies, these things have very gentle tugs on the Earth's orbit.

We're going to do a whole episode soon about spin resonances and tidal locking. The whole solar system is like an incredibly complicated Swiss watch. But it means that there are these cycles that change how the Earth tilts and also how the Earth orbits as it goes around the sun based on these little gentle tugs from things other than the sun. Wow. I guess there's still pretty small changes maybe. Like if you looked at the picture of it, maybe you couldn't tell the difference between the sun. the different orbits. Yeah, the orbital changes are not huge, right?

If you're looking from a distance, you definitely couldn't see anything. But you know, small changes in how much the Earth tilts towards the Sun or how far away it is from the Sun, you really can have a strong impact on the amount of solar radiation. For example, if you look back over the last 20 or 100,000 years, you see variations of up to 20% in the amount of solar radiation that hits the Earth based on these cycles. Wow. Yeah, I guess you can sort of look at the record, right? Like you can look at ice layers and rock layers and you can see that it used to be sunnier before or not.

Yeah, they do these core samples where they dig down in layers of ice in Greenland or in other parts of the world and they can see the global temperatures and there really is variation. And they do these calculations based on, you know, solar system models and to understand the variations in the Earth's tilt and orbit. And there's a really nice alignment between these global temperatures and these Earth's orbital changes. Wow. And it's crazy because it's like small, even time. little changes can basically change the weather. Like if the earth tilts three degrees or two degrees this way or that way a little bit more, then suddenly we have an ice age. It really is incredible,

but this is just one effect that's important to understand. Other things like atmospheric effects can drown them out. For example, if we hadn't been pumping CO2 into our atmosphere, scientists predict we'd be due for like a big glaciation stage in about 50,000 years. Now that's sort of off the table because the amount of CO2 that we pumped into the atmosphere. atmosphere. So we can override these effects with larger effects like the greenhouse effect. Wow, that's incredible. So we can actually like change the destiny of the earth. Like we could totally ruin it perhaps even. Yeah, exactly. And so I just don't want anybody out there to think that all of the change in the atmosphere is due to natural effects from the Earth's orbit. This is

an effect and it has contributed to glaciation and to ice ages, but it's not the only effect. And it doesn't even have to be the dominant effect. And it also sort of impact, as you said, how much radiation we get. Like if our orbit flies a little bit closer to the sun, it's going to get a little hotter on Earth, too. Yeah. And some of these things can be sort of dramatic. Like you have different cycles based on the orbit and the tilt and all of these things.

There are different cycles there, which have different periods, like 20 or 40 or 100,000 years. Sometimes they all come together and happen all at the same time. You can get pretty dramatic shifts in temperature, like about 13,000 years. years ago, when temperatures dropped dramatically in just a few decades. And then 1,300 years later, temperatures spiked like 10 degrees Celsius within just a few years. It's like all of the effects swung one way and then swung the other way. These things can have really big effects on the Earth's climate. 10 degrees is huge. It seems like it's not totally unpredictable, right?

Like we have a certain model of the solar system and our atmosphere. And so, you know, we should believe the scientists when they say what's going to happen next. Yeah, this part is pretty predictable because we have good models for how the Earth's orbit is affected by the tug of Jupiter, et cetera, et cetera. The other parts, you know, climate resonances and what happens with greenhouse gases, that's something we're working on is not as well understood and can be more dramatic. You know, something I didn't realize was that the climate is even affected by the flow of the continents. You know, as the continents move over the surface of the Earth, they change how water flows. Is there a water channel between the two continents or not, for example?

and that affects how the atmosphere moves. And that can have significant effects on the climate as well. Wow. There's a lot going on. It's a big complicated system with a huge number of feedback cycles, you know. So if you get it a little bit wrong, then you can get it a lot wrong. But, you know, climate scientists are doing a great job at modeling this stuff. Well, I guess Carson's question is what would have happened if we hadn't had the last ice age?

And so let's talk maybe about how an ice age impacts the earth. Yeah. So the most recent ice age, scientists say lasted from about two and a half million years ago till about 12,000 years ago. Wait, it lasted millions of years? Yeah, these ice ages can last millions of years and sometimes hundreds of millions of years. But within an ice age, there are more variations than they call these glacial periods where things can then, the glaciers can retreat and come back.

And so the most dramatic and the one that really affects sort of life on Earth and the way we live it is the last glacial period, which lasted from about 100,000. years ago to about 12,000 years ago. So that's the most recent impact on sort of like human development and migration. Because I guess the northern parts of the and southernmost parts of the earth got more covered in ice than usual, but not completely. You said that we only got completely covered millions of years ago. That's right. During this last glacial period, we had like Canada was an ice sheet. Most of the northern United States was an ice sheet. There were lots of glaciers around the world at high altitudes, but you know, it's not like the whole

was an ice sheet. But, you know, it affected humanity. Humanity, for example, mostly lived at lower latitudes during this stage until the ice retreated and then they could migrate to Eurasia and more northern latitudes. Like it was still sunny in the equator? Yes, it was still sunny in the equator. And hot or a cooler? It was cooler than it is today, but obviously it was hotter at the equator than it was at the pole still. What about Berkeley? Berkeley will always be cool, man. very chill not as chill as you see santa cruz right they're the chill ones yep nobody can chill like banana slugs all right well let's get a little bit more into the impacts of the ice age on earth and the last ice age on earth and what would happen if we hadn't had that ice age first let's take a quick break

December 29th, 1979, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently, the explosion, actually, impelled metal, glad.

The injured were being loaded into ambulances, just a chaotic, chaotic scene. In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and Order Criminal Justice System is back. In season two, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order. criminal justice system on the iHeart radio app apple podcasts or wherever you get your podcasts

my boyfriend's professor is way too friendly and now i'm seriously suspicious well wait a minute sam maybe her boyfriend's just looking for extra credit well dakota it's back to school week on the okay story time podcast so we'll find out soon this person writes my boyfriend has been hanging out with his young professor a lot he doesn't think it's a problem but i don't trust her now he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate.

Well, according to this person, this is her boyfriend's former professor and they're the same age. And it's even more likely that they're cheating. He insists there's nothing between them. I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts or wherever you get your podcast.

Hola, it's Honey German. And my podcast, Grasias Come Again, is back. This season, we're going even deeper into the world of music and entertainment with raw and honest conversations with some of your favorite Latin artists and celebrities. You didn't have to audition? No, I didn't audition. I haven't audition in like over 25 years. Oh, wow.

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of Family Secrets. Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, we are answering questions from listeners. And our first question was from Carson, who asked what would have happened if we hadn't had the, I guess, the last Ice Age. That's probably the one that Carson is most wondering about. And, you know, the Ice Age has big impacts on geology because the glaciers can like grind mountains and create valleys. It also has a big impact on the flora and fauna that develop to adapt to that climate. And specifically, it had a pretty big impact on where humans ended up and how we evolved.

Yeah, it's sort of an interesting effect that maybe when I was younger I hadn't thought about that like glaciers can really kind of like smooth over a landscape. I think a lot of the, like, the eastern United States has, you know, more rolling hills rather than dramatic mountains because the glaciers basically like, you know, crunch them all down. I'm not actually sure about that. I think that smoother mountains are just older mountains. They have been worn down by wind and rain and cycles of weather. Rockies, for example, are sharper because they're younger. It's incredible. And the history of this science is really fascinating. As people realized that there was this incredible, powerful, dramatic force that happened very. very, very slowly on Earth. These moving of these glaciers can really shape valleys and distribute boulders. It was the presence of these boulders that tip people off.

People in the Alps were like, how did this rock get here? It's from much more northern climates. People were wondering how to explain where all the rocks were. And very slowly they put together this crazy story about sheets of ice moving over the earth and changing its shape. It's kind of bonkers. And like boulders hitching a ride or like surfing the glacier wave?

Mm-hmm, yeah. glaciers break boulders off of mountains and then can carry them for hundreds of miles and deposit them somewhere else. Wow. Yeah. And is that how Stonehenge got built? I think that was graffiti from the alien skiers, actually. The alien snowboarders who came to a snowboard and piled some rocks like a tourist usually do?

I think that's another divide we don't want to get into skiers versus snowboarders. But yeah, like you said, it really affects the trajectory, not just of the land. but also life on earth. Like if most of the earth is covered in ice, it's going to, you know, determine what kinds of animals survive and which ones don't. And, you know, the kind of flora and fauna that we have, you know, the fact that we have like horses and cows

and a lot of the grains we eat are basically evolved grasses. That's due to the climate that we had. If we hadn't had an ice age, for example, the whole earth might be wetter and it might be warmer and it might be more covered in jungles and rainforests than grassy, planes. And so the kind of farming practices we develop could have been totally different. Oh, interesting. So that's one way, one specific way that Ice Age has, you know, impacted us is

we would have less fewer horses and cows and grasses, grasslands. And the whole concept of agriculture could be very different. A farm could be basically a piece of forest. You know, it's hard to imagine how civilization and how agriculture might have developed in the context of basically everybody living in the Amazon. Interesting. Yeah. Because it might have also affected huge. human development, right? Absolutely. There are some theories that the harsh living conditions during the Ice Age basically forced humans to develop cognition, to evolve bigger brains so that we could

work together and develop tools, hunt woolly mammoths, this kind of stuff. It certainly had an impact on humans, although there's always the alternative reality game there. Like, sure, that might have played a role. We don't really know what would have happened to humanity in other situations. Maybe we would have been even smarter. I see. The theory is sort of like because it was, we had.

these long winters, it kind of force humans to plan ahead and to think about like crops and strategizing, which kind of pushed us to be smarter and to be and to be less procrastinators. Exactly. But these are always just explanatory stories, right? There aren't really testable theories. It's very easy to look at a series of events and say, oh, this makes sense and I think this is why it happened to really know you'd have to run alternatives. You'd have to say, well, let's see what happens if I change things. And that's sort of a fascinating question. but one will never know the answer to because we only have this one universe and we only see what happens to this earth one time.

Yeah, we need like a control earth for every single conceivable experiment. We do. We need the multiverse for that reason so we can see, you know, what would happen if I had gone to Stanford? Would I be a different person today? You'd definitely be much cooler, maybe. And or richer, apparently. Maybe you would have invented TikTok, Daniel.

If I had, it would have been a lot more boring than it is today. It would have been physics talk. Exactly. All right, well, I think that answers Carson's question. If we hadn't had the ice age, things would be really different. Well, first of all, it sort of depends a lot on our trajectory in space and how close we get to the sun and how tilted we are. But if we hadn't had the last one, maybe we would be eating different kinds of plants

and fruits and animals and or we might be a little bit different ourselves. Yeah, we might all be roasting banana slugs over the fire. And we might all be procrastinating. instead of just some of us being procrastinators. Speaking of procrastination, let's get into our next question, and this one comes from Chris, who has a question about photons moving near black holes. Hi, Daniel and Jorge.

Thank you so much for your show. I look forward to it every week. All right, here's my question about photons. So let's say we are on Miller's planet, like the one in interstellar, and we look up at the sky and we can see a star. So the photons coming off that sun, let's say some of the photons miss the gravity of the planet and continue on to their destination. But a few of those photons get trapped or caught into the gravity of the planet.

So from the perspective of somebody that's not in the gravity of the planet, doesn't that photon travel slower than the other photons that moved on that didn't get caught in the gravity of the planet? Kind of confusing. All right, thanks. Kind of confusing, for sure. That's where we're here. I think there's a good summary of general relativity right there. Kind of confusing, yes. Special relativity.

Chris says it's kind of confusing. But it's a really excellent question. He's asking a really difficult and subtle question about what it looks like to see a photon go near a very massive object to be sucked into the gravity well of a black hole or a very dense planet. Right, because we're, We talked about on this podcast how when you have a lot of mass, like in a black hole or just like a heavy planet, it kind of bends the space time around it and it actually sort of slows down time.

I think that's maybe what he's trying to connect. Yeah, it can slow down time. And also it changes the path of these particles. It changes the fundamental geometry of space, the way the particles move and these to really confusing and sort of paradoxical ideas. Like one thing we say in the podcast a lot and the people talk about in physics a lot is light always. moves at the speed of light no matter who's measuring it, right? We say that a lot. On the other hand, we also say that like photons can't escape a black hole. And people might be puzzling about that. Like, what does that mean? How fast is a photon moving when he's trying to climb out of that gravity

well? Doesn't it eventually get stopped by the gravity of the black hole? How do you reconcile those two ideas? Yeah, it's kind of confusing for sure. But I think maybe the scenario he is, I think he was trying to paint is that like, let's say a star shoots off two-fold. And one photon just goes clear through space, no, nothing in its path. But the other one flies like close to a heavy planet or close to a black hole. Like if you were looking at these two photons, with the one that goes near the black hole, would that one go slower? Yeah.

Would you see a photon moving at less than the speed of light? And your instinct, physics-wise, is to say, no, absolutely, that can never happen. Problem is, that's not exactly true. Because when we say photons always travel at the speed of light, there's a qualifier. There's a caveat that we almost never mentioned that's important in this particular case. And that caveat is that it's true that photons always travel at the speed of light, but that's only true if space is flat. That is, if there's no curvature to space and only true for nearby observers.

So the full statement is that photons only travel at the speed of light as measured locally by people nearby in flat space. If space is curved and you're far away, away from an object, the rule that photons have to travel at the speed of light no longer holds. Interesting. I think what you're saying is that like photons have to travel at the speed of light in space, right? Like to the photon, it's always going at the same speed. But you're saying you can't sort squish and bend space itself, which might to a, someone who's looking from far away, might make it actually go faster or slower than the speed of light. Yeah. And it goes one step deeper than

that. And remember that you can't talk about velocity without talking about pairs of pairs of objects. Velocity is not a property of an object. A ball flying through space doesn't have a speed. It only has a speed relative to observers. So whenever you talk about velocity, you can't think about a ship traveling near the speed of light. You always have to say a ship traveling at whatever speed relative to Earth, for example. So in this case, we're talking about photons relative to an observer nearby versus photons relative to an observer far away. The problem is that in general relativity, that is the theory that tells us how to think about the universe as it curves and bends in response to mass, there is no well-defined definition of velocity for something that's far away. It's like you can't even really sensibly talk about the speed of a photon that is very far away from you.

Wait, what? What do you mean? Like I can see it in one spot from a distance and then I see it in another spot from a distance from a distance, a short time. later, I can, you know, measure the distance between those two things and divide by the time. That would get me the speed. Yeah, that sounds straightforward. But the problem is that you were using your local inertial reference frame to measure the path of something that's moving through curved space far away. So you're assuming that space is flat between here and there. And if it isn't, if space is curved, then the reference frame of someone else nearby those photons would be very different.

And your measurement of velocity and theirs won't agree. For example, a distant observer will see light near a black hole travel at all sorts of crazy speeds from less than the speed of light all the way down to zero. But a local observer near the black hole and near that photon will always measure that light moving at the speed of light. But this is more than just different reference frames having different values. We have that in special relativity and we know how to translate and compare. But because space is curved, there are many different ways to compare those measurements. of velocities in general relativity. So to translate between two different reference frames

and curved space, now why is that? What you need to do in that case is compare its velocity to your own, right? You need relative velocity. And so you're making those measurements. And so really what you're doing is you're comparing two different vectors there, like your velocity and its velocity. And that's something you can do if space is flat,

but it's not something that we know how to do if space is curved. And it's useful to think about. an analogy like making a measurement on the surface of the earth. Say, for example, you have two runners and they're running a race. If they're next to each other, it's very simple to see who's faster. They're literally next to each other. Now imagine you take one of the runners and one of them is in Paris and the other one is in Cape Town, South Africa or something. So they're like on different places in the earth. Now they're not really running in the same direction, right? Because the earth

is curved. One is running in one direction. The other one is running sort of in a different direction. So how do you compare their velocities, right? Well, one thing you can do is to say, well, I'm going to take the velocity vector of the Cape Town Runner and I'm going to bring it over to Paris. I'm going to sort of like transport it over to Paris and then I'm going to compare the two velocities. I mean, like if I'm floating in a space station looking at these two runners from space. You just want to compare these two, right? It doesn't matter really where you are from that perspective. You've got to bring those vectors close to each other. But why do I have to do that, I guess? Couldn't I just, for example, from

space in my space station, measure the length of the track that the American runner is in, and then measure from space the length of the track that the South African runner is in, and then, you know, as I see, I start the clock when they both start running, and then I measure how long it took to get to the other side of the track. Yeah, you could do that. You could ignore the courage of the earth and just measure their velocity relative to somebody in space. That's like, again, assuming everyone is in your local inertial frame, and that space is flat. But we put people in this example on a curved surface as an analogy for what happens when space is curved. But when we're running a race, we really want the velocity along the earth, right,

not the velocity through space. What you want is the answer of if I brought the Cape Town runner to Paris, who would win this race? Right. And so the curvature of the earth makes a difference there. You can't just ignore it. Oh. All right. So you're saying that it's hard to measure or compare velocities in curved space because things kind of get kind of wonky because because space time is being curved. That's right. And the problem is that how you compare those two vectors depends on how you bring one vector close to the other vectors.

This is called parallel transport in geometry. You want to compare two vectors, you're going to bring them near each other. In flat space, that's not a big deal, because if you move the vector from there and here, it doesn't change. In curved space, the vector changes as it moves through that curved space.

And so there's an infinite number of different ways you can do it. And the answer you get depends on the path. So if you bring the Cape Town guide to Paris along one path, his vector will be in one direction. If you do it on another path, his vector will be in a different direction. And so this is all really important because it means that you can't define the difference between those two velocity vectors across curved space. And so that means that you can't talk about the relative velocity of things that are really,

really far apart. You can't define what happens to a photon. And that means that the rules of special relativity no longer apply. So a photon moving around a black hole could appear to have a velocity, not the speed of light, all the way down to apparently zero velocity as it tries to climb out of that gravity well. Right. I think what you're saying is that if we were to run the experiment that Chris wants us to run, which is like shoot two photons and have one go into a black hole, like we would see one of them just fly through space away.

And the other one we would see actually like kind of stop at the black hole kind of like, right? Like it would just stop from our point of view. From our point of view and according to our decision about how to measure that velocity. somebody else looking from another perspective might have a different definition of like well here's how I'm to bring those velocity vectors together to compare them they might get a different answer what do you mean like if I'm moving maybe at a different speed but if I just stand on the other side of the black hole I'm probably going to see the same thing right I'm going to see one photon keep flying off and the other one stop at the black hole right but in order to measure the velocity of that photon you need to talk about how to bring its velocity vector into your local space and there's an infinite number of ways to do that and the choice you you make about how to transport that vector changes the answer. So you and I could be right next to each other looking at the same photon, but if you have a different definition of basically velocity in general relativity than I do, we could get

different answers. So that's why people say it's not well defined because there's an infinite number of arbitrary choices you can make that do affect your answer. All right. Well, then what would be the answer for Chris? So would you see that photon move slower, the one that goes near the heavy mass? You would see it move slower, exactly. no matter where you are.

You would see it move slower than the speed of light, almost no matter where you are. And this might be confusing to people if they think, well, how can we not define the velocity of objects that are far away? Like we talk about galaxies moving really, really fast away from us, and other galaxies are very far away. That's one of the reason we can talk about who galaxies moving away from us faster than the speed of light. One way to think about it is that space is expanding between us and those galaxies.

Another totally reasonable way to think about that is to attribute that velocity actually to the objects and not to the motion of space itself. Those are both arbitrary but reasonable choices. And that's why we say like the velocity of objects isn't well defined in GR because it requires an arbitrary choice. It's kind of like how we've always said or said often on this podcast in our books. It's like if Hussein Bolt can only run so fast on land, but if there's like new land being made between us and him, he's going to look like he's going faster than what he can actually run or if there's if like the continent he's on is actually moving towards us he might appear to be moving slower exactly and that's the standard choice in cosmology to think of the universe as

expanding in a certain way and to think of motion relative to that expanding space and that's a totally reasonable choice and that's what we usually do when we talk about the expansion of the universe and the velocity of really distant objects but you could make other choices that's an arbitrary choice is just sort of the one people typically make you could make other choices which is why these velocities of very distant objects, technically not well defined. And that's why you can end up in situations where you say things like, oh, light is moving slower than the speed of light. It's because velocity of faraway objects is not really well defined. If you're near a photon, it will always be moving at the speed of light relative to you. Right, right. Yeah, like if you're

falling into the black hole with the photon, the photon would just look like it's moving at the speed of light. But that's because also your time frame is also being slowed down, right? Exactly. It's near you. And so locally, space is always flat near you. And so if you're with the photon, it's moving through flat space at the speed of light. A distant observer, that's where the problem comes in because the definition of velocity for distant objects

is funky in general relativity. Whereas Chris says, kind of confusing. I think that's the real answer for Chris here to his question. It's kind of confusing. All right, well, let's get into our last question, and this one is a little bit related. It's another question about light and its speed. So let's get into that.

But first, let's take another quick break. December 29, 1975, 1975, LaGuardia Airport. The holiday rush, parents hauling luggage, kids gripping their new Christmas toys. Then, at 6.33 p.m., everything changed. There's been a bombing at the TWA terminal. Apparently, the explosion actually... impelled metal, glass. The injured were being loaded into ambulances, just a chaotic, chaotic scene.

In its wake, a new kind of enemy emerged, and it was here to stay. Terrorism. Law and Order Criminal Justice System is back. In Season 2, we're turning our focus to a threat that hides in plain sight. That's harder to predict and even harder to stop. Listen to the new season of Law and Order Criminal justice system on the iHeart radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly, and now I'm seriously suspicious.

Well, wait a minute, Sam, maybe her boyfriend's just looking for extra credit. Well, Dakota, it's back to school week on the OK Storytime podcast, so we'll find out soon. This person writes, my boyfriend has been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want her gone. Now, hold up. Isn't that against school policy? That sounds totally inappropriate. Well, according to this person, this is her boyfriend's former professor and they're the same age. It's even more likely that they're cheating. He insists there's nothing between them.

I mean, do you believe him? Well, he's certainly trying to get this person to believe him because he now wants them both to meet. So, do we find out if this person's boyfriend really cheated with his professor or not? To hear the explosive finale, listen to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get your podcast. Hey, sis, what if I could promise you you never had to listen to a condescending finance bro? Tell you how to manage your money again. Welcome to Brown Ambition. This is the hard part when you pay down those credit cards.

If you haven't gotten to the bottom of why you were racking up credit or turning to credit cards, you may just recreate the same problem a year from now. When you do feel like you are bleeding from these high interest rates, I would start shopping for a debt consolidation loan, starting with your local credit union, shopping around online, looking for some online lenders because they tend to have fewer fees and be more affordable. Listen, I am not here to judge. It is so expensive in these streets.

I 100% can see how in just a few months you can have this much credit card debt when it weighs on you. It's really easy to just like stick your head in the sand. It's nice and dark in the sand. Even if it's scary, it's not going to go away just because you're avoiding it. And in fact, it may get even worse. For more judgment-free money advice, listen to Brown Ambition on the IHeart Radio app, Apple Podcast, or wherever you get your podcast. Your entire identity has been fabricated.

Your beloved brother goes missing without a trace. You discover the depths of your mother's illness, the way it has echoed and reverberated throughout your life, impacting your very legacy. Hi, I'm Danny Shapiro. And these are just a few of the profound and powerful stories I'll be mining on our 12th season of Family Secrets. With over 37 million downloads,

we continue to be moved and inspired by our guests and their courageously told stories. I can't wait to share 10 powerful new episodes with you, stories of tangled up identities, concealed truths, and the way in which family secrets almost always need to be told. I hope you'll join me and my extraordinary guests for this new season of Family Secrets. Listen to Family Secrets Season 12 on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. All right, we are answering listener questions

and also debating Berkeley versus Stanford, apparently. There's no debate, man. I mean, it's just talking about it. I see. Well, I think there's a debate about whether there is a debate, anyway. I think there's only really one side of that debate. No, we're answering listener questions. And our last question here comes from Dennis,

who has a question about the speed of light. Hello, Daniel and Jorge. First of all, love your podcast. I was wondering, what is the minimal speed of light to sort of hold a universe together? And what would happen if light would only have 1,000 kilometers per second of speed?

What would happen then? Okay, thank you. All right, awesome question from Dennis here about the speed of speed. of light. And I guess this question is sort of like, because we've talked about on this podcast before and in our book also about how the speed of light is a little bit arbitrary. Like you can, it could have, it's like 300 million meters per second, but it could have been something different. It could have been three meters per second or three billion meters per second. And

you could maybe still have like a functioning universe. Yeah, we don't really know if it could have been something else, but we don't know why it is what it is. We have no explanation for it being that number in particular. And that suggests, that maybe it could have been something else. And there's lots of really interesting philosophical wrinkles there. Like, are there other versions of the universe out there in the multiverse with different speeds of light, et cetera, et cetera? And it's a really great question to ask, like, what speeds are allowed?

Could the universe work if the speed of light was different? Yeah, pretty cool. And something I think we discussed recently in a podcast episode that was a little mind-blowing for me was that you told me that the speed of light is not actually a fundamental, like, unit or value of the universe. That's right. The speed of light has units to it, right? Meters per second.

And so the actual number is really arbitrary because it depends on the units. So when we talk about the construction of the universe and the parameters that influence the way that it is, we try to focus on numbers that don't have units to them, dimensionless numbers, numbers like the cosmological constant, which affects the expansion of the universe or the ratio of masses of the electron to the muon, for example. And the speed of light does factor in because it's part of what we call the fine structure constant, which combines a bunch of these different constants, planks constant, the speed of light, the strength of electromagnetic force.

Yeah, like a ratio, right? Like the speed of light divided by how quickly Berkeley students think. Two really big numbers. But I think the idea is that generally speaking, like, you know, how fast, light travels through space is sort of like a fundamental property of the universe that we currently can't really explain. Like it seems arbitrary. Yeah. And it might be that it bubbles up from a deeper understanding of the nature of space time. You know, if space, for example, is a quantum foam of little space pixels linked together by tiny wormholes, it could be that some property of those wormholes

influences how information propagates from one space pixel to the other. And that determines the speed of light. We just don't know. It's a sketch for maybe how you could get an answer. to what the speed of light is. Or it could just be a totally arbitrary. It could be that as universes are created, there's some random process that sets these parameters, and this is the one that we got. I think you get 300 million meters per second.

You get 20 meters per second. Exactly. And it's fun to think about what the universe would look like. And I love the way Dennis posed this question, which is like, could the universe come together with the minimum speed of light for a universe to function? Yeah, it seems like he has a two-part question, actually. the first part is like, could we have a universe with a slower speed of light and what would be the

slowest speed of light that a universe would still hold together, which is sort of an interesting way to put it like, could, would the universe fall apart if the speed of light was slower? Well, you know, the way I think about this is in terms of light cones, something we talked about in the podcast once, which tells you what portion of the future of the universe you can influence and which portion of the past of the universe influences you. Because we have this maximum speed of information. It means that, for example, you can't affect things in a neighboring galaxy that are happening right now. If you made a decision about something you wanted to happen in Andromeda, it would take millions of years for that decision to have any effect. That's your

light cone, a fraction of the universe in the future that you can influence. And the size of that cone, the slope of that cone is determined by the speed of light. So if the speed of light was much, much faster, then you could influence Andromeda maybe tomorrow. If the speed of light was much, much slower, it might take billions of years to affect Andromeda instead of millions. And so the size of that cone, the narrowness of that cone is determined by the speed of light. Yeah, I mean, it definitely would change the universe. But I think his maybe question was more like, is there something in the equations of the universe that we know about right now, that if I, you know, start dialing the speed of light down, would at some point the equations fail or become incoherent or illogical?

Or is it really the fact that, you know, the speed of light could be one centimeter percent? second and you could still have a functioning universe. Yeah, as far as I know, there is no minimum speed. You would have completely different kind of universe. It would feel very, very different. And it might affect the structure of matter. You know, the orbits of the electrons, for example, are affected by the speed of light. And so you might not get hydrogen.

You might get weird other forms of matter. But you would still have a universe even with a much slower or much faster speed of light. I see. Like if you change the rules, the atoms and the corks and all that would just, play differently, but they could still play. They could still play, exactly. And they would play differently. And the consequences that are really hard to imagine and difficult to calculate also.

We don't really even have a great theory for like how corks come together to make protons and neutrons because it involves the strong force, which is a real pain to calculate. And so if the balance of all those forces changes, then a lot of things that are difficult to calculate would be different. So the whole universe could be very different. But, you know, if the universe doesn't change that much, if the speed, of light goes down by 50% or something, I think you'd largely get the same universe, but it would feel different. Like you could see less of the universe out there. Like our little bubble, the observable

universe, also depends on the speed of light. Right. Well, but I think it's also maybe deeper, perhaps, than just what we can see because the speed of light doesn't just affect light and photons. It also sort of determines how fast some of these fundamental particles can move, right? And also kind of like the range of their effect, right? Like I'm thinking some of the four. particles, if they could move faster or slower, then they wouldn't be a strong, perhaps. That's certainly true. The speed of light, I think, most directly affects the strength of the electromagnetic interaction, because it goes directly into the fine structure constant, which appears in the coupling of photons to electrons and photons to other charged particles. So the

speed of light was different. It would change also sort of the relative strength of electromagnetism to the other forces. All right. So you said it would be different. So what are some of the ways is that the universe would be different if the speed of light was slower. Well, if the universe was different, if the speed of light was slower, we couldn't have as large a structure forming in the universe. Like, in order to have a structure form, you need to have information go back and forth across it. You know, for a planet, for example, to coalesce gravitationally, you need information to propagate from one side of the planet to the other,

for it to be like a single object. You mean like gravity, even the force of gravity has the speed limit, and that speed limit is the same as the speed of light. Yeah. So if we're talking about like the speed of information through the universe, then if you're cutting the speed of information down, then gravity also transmits its information more slowly. Right.

You would be basically slowing down gravity too. Yeah, you would be slowing down gravity and you would be limiting gravity in the size of the thing that it can build. You know, we think that there's like a biggest structure that can exist in the universe because it takes time for gravity to pull things together. and the universe hasn't existed for that long. So, you know, the universe has been around 14 billion years.

That means you can't have a structure that's like 50 billion light years wide because it just hasn't been time for like one side of it to coordinate with the other side and like come into equilibrium with it. So there's a limit there on the biggest thing you can make and that depends on the speed of light. Right. It's like trying to bring your kids together if you're a really slow person. You can't. Like if you slow down gravity like gravity would be trying to pull all those distant galaxies.

together, but maybe by the time it acts, the galaxies are long gone. Yeah. Or say, for example, you're trying to organize a family reunion. You can get in touch with much more distant relatives if you can email them rather than having to send snail mail or send a pony. If you can only send a pony, then you can organize a much more local family reunion. Whereas if you can email people, you can get people from Singapore and people from Australia to come to your party. And so in that way, the universe would be sort of more local if the speed of light was smaller. Right.

Although I do know you, Daniel, and I know that a family reunion, you would organize it with ponies so that it may be a wouldn't hold together as well. I mean, like, I put it on the back of an anteater. What's the problem? You didn't get the invitation? I don't get it.

Should it put it on the back of a tree. A banana slug. But it's not just sort of, it doesn't just affect the structure of the universe, right? Like if you slow down gravity, it would also affect relativity too, right? Yeah, a lot of the really weird effects from relativity, time slowing down and things getting contracted, all that kind of stuff.

We never see those effects because they only happen when you're going at very, very high speeds relative to something else. So that's why it took us a long time to even discover that it's part of reality. But if the speed of light was slower, if it was like closer to human speeds or speeds we could achieve on earth, then we might have noticed these things because you would be able to see them and we might have like intuition for relativity would like make sense to us. in a way that right now it doesn't. Well, I wonder, though, like, if you slow down gravity and light and basically how everything can propagate in the universe,

wouldn't sort of time also slow down, or wouldn't it feel slower as well? To the point where, you know, it's almost like if you're near a black hole, your time is moving slower, but you don't notice it. It's a great question, and this sort of goes to the heart of why we talk about dimensionless constants instead of dimension full constants like the speed of light. Because, for example, you could change the speed of light, But then if you tweaked a bunch of other numbers at the same time, nothing effectively would change in the universe.

I think that's what you're talking about. If you tweaked a bunch of these numbers in such a way that none of the dimensionless constants changed, for example, if you change the speed of light, but you also change planks constant and you changed the strength of the electromagnetic force, and you wouldn't notice anything because you have no absolute ruler to compare it to. It's sort of like if you got bigger and your ruler got bigger, you wouldn't notice any difference, right? Yeah, I think you know what I mean. it's like if you slow down the speed of light and slow down gravity, wouldn't that also maybe affect how fast you can think? Like would you technically be thinking slower?

Oh, your perception of time. Oh, that's fascinating from a neurobiological point of view. That's a great question. I don't know that our thinking, though, is limited by the speed of light. I think it's more affected by whether you went to Berkeley or Stanford. No, that's a great question. I don't know the answer to that, whether the speed of your brain is actually affected by the speed of light. whether our internal sense of time is affected by the speed of light. I suspect that it isn't, that the biological processes are very, very slow. But I'm really just speculating there.

Well, but, I mean, chemical reactions in your brain depend on the electromagnetic force, right? Which would be slower as well. Yeah, that's true. Those bonds would have a different strength. We'll ask Katie Golden next time she's on since she's an expert. Yeah, did she go to Stanford? No, she went to Harvard. Oh.

East Coast, West Coast. It just got complicated. All right, well, at least Team West Coast is representing today. That's right. We should unite against the true enemy, Daniel, the East Coasters. Exactly. All right, well, it also might have a very direct impact on our everyday lives if the speed of light was slower, specifically as you're listening to this podcast, right?

Yeah, the Internet would be slower if the speed of light was slower. We rely these days on being able to, like, stream HD videos from around the world, downloading gigabyte files from Australia, etc. But the internet moves at the speed of light. And so like the bandwidth would be the same, but the latency would be longer. Like if you wanted to ping a computer in Australia and the speed of light was 1,000 kilometers per second instead of 300 million meters per second, then you would notice a different. Wow. I bet half of our listeners are going, and that's not a universe I want to live in.

Forget it. Let's not even dwell on that. Everybody wants to live in the universe where the speed of light is faster and they get their downloads more quickly. Yeah, we all want optical fiber. at the current speed. All right. Well, I think that answer is a question for Dennis. There is no minimum speed of light

that would hold the universe together. It could literally be like 0.000,0001 meters per second. And you could still have a universe. It just would be super duper different. Yes, in ways that are probably impossible to predict. So, hey, let's give it a try and find out. No, I want my fast internet, Daniel. I want my family reunions tomorrow.

All right, well, thank you to all of our question askers. We hope that was interesting for all of us. I think it was interesting for all of us. It makes you kind of think about, you know, how the universe could have been different and the earth could have been different. All these interesting what if questions. And sometimes the hardest questions,

the deepest ones, the most insightful ones, are the ones that everybody asks. You don't have to be an academic physicist or a working cartoonist to think deeply about the universe and ask fascinating questions. So please engage your brain and think about the universe. And if you have a question you don't know the answer to,

don't be shy to write to us to questions at Daniel and Jorge.com. Yes, and those are your questions, even if they are a little confusing. We hope you enjoyed that. Thanks for joining us. See you next time. Thanks for listening,

and remember that Daniel and Jorge Explain the Universe is a production of IHeartRadio. For more podcasts from IHeartRadio, visit the IHeartRadio app, Apple Podcasts, or wherever. you listen to your favorite shows. Ah, come on.

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so you can work, create, and boost productivity all on one device. December 29th, 1975, LaGuardia Airport. The holiday rush. Parents hauling luggage, kids gripping their new Christmas toys. Then everything changed. There's been a bombing at the TWA terminal. Just a chaotic, chaotic scene.

In its wake, a new kind of enemy emerged, terrorism. Listen to the new season of Law and Order Criminal Justice System on the IHeart Radio app, Apple Podcasts, or wherever you get your podcasts. My boyfriend's professor is way too friendly. Now I'm seriously suspicious. Wait a minute, Sam. Maybe her boyfriend's just looking for extra credit. Well, Dakota, luckily, it's back to school week on the OK Storytime podcast, so we'll find out soon.

This person writes, my boyfriend's been hanging out with his young professor a lot. He doesn't think it's a problem, but I don't trust her. Now he's insisting we get to know each other, but I just want her gone. Hold up. Isn't that against school policy? That seems inappropriate. Maybe find out how it ends by listening to the OK Storytime podcast on the IHeart Radio app, Apple Podcasts, or wherever you get. your podcast. This is an IHeart podcast.