I Don't Know About That - Time

Episode Date: May 3, 2022

In this episode, the team discusses time with theoretical physicist and host of the Mindscape podcast, Sean Carroll. Follow Sean on Twitter and Instagram @SeanMCarroll . Make sure to check out his podcast on Apple Podcasts, Spotify, or wherever you listen to podcasts! Our merch store is now live! Go to idontknowaboutthat.com for shirts, hoodies, mugs, and more! Subscribe to our Patreon at patreon.com/IDKAT for ad free episodes, bonus episodes, and more exclusive perks! Tiers start at just $2! Go to JimJefferies.com to buy tickets to Jim's upcoming tour, The Moist Tour.See omnystudio.com/listener for privacy information.

Okay. I wasn't ready. I thought I was ready, then I wasn't ready. I've got no words. You might find out. I don't know about that. With Jim Jefferies. Wow.

The prep work we do on this show. Jack looked over at me and went, are you ready? And then he's TV John Mayer, and I thought I'll go John Mayer, and then I couldn't think of another John, and then I almost said John Denver. I think I mentioned John Denver before. And so, yeah, twice. So I was like, ah, just bail out on this one.

I like how you're like, the prep work we do on this show. Just you. It was your goal to not have to do any prep work. The prep work that I do on the show. All right. I acknowledge that. I want to thank all the people at Calgary and Edmonton for coming out to the shows.

All four shows were fantastic. The crowds were great. It feels like we're all back in business now after COVID. I will say this about the tour that I don't know if it's because I'm sober or what it is, but all the shows have gone good. There's been varying degrees of goodness, you know, but there hasn't been a dud amongst them on this tour. All the audiences have been great.

Normally there's one show where you go, fuck. Yeah. Well, coming up this weekend. Coming up this weekend, we're in Cleveland and Detroit. So it has an opportunity to go badly. Anything can happen. Anything can happen. There's an extra show added in Detroit.

We added an extra show. So get on to those tickets. The last time we were in Detroit, we did two shows in one night. Yeah, I stopped doing that. Yeah, and then I started the second show. And I don't think whoever was in charge of us didn't check to see that the crowd was in our seats i think they just started it and it was a battle royale for me because we were justin martindale's there and he because he went first the first show i'll go first

this one and he was just standing on the side of the wings and he was like i'm so happy you at first because i was like all right they did there was some people in the front row that did the um uh the naked gun thing with the queen's box you know yeah There was some people in the front row that did the naked gun thing with the Queens box, you know? They were just sitting in the front row, five people, and then people came up with their tickets, and they're like, oh, I guess we're in the wrong front row. I was like, I guess we're not in the front row.

I guess we're in the second story, it turns out. That F looked like an A. No, they weren't even close. They went way to the back, and they were drunk as shit. And I was like, oh, it's going to be one of these shows. I got tickets at Dodgers Stadium and that happens all the time because, you know, people don't show up to their season tickets. There's 80-something games to see.

And so people are always very cool about it, though. You walk up and they go, yep. I'm going to get the fuck out of here. Yeah, good one. Lasted. Yeah, it's one of my favorite scenes in the Naked Gun go they're in the box where the queen would be sitting like oh yeah i guess these are silly us all right now you got anything to promote i have a show may 19th at sacramento it's at a place called harlows it's the starlet room at harlows and it's on my website

forshaw.net there's a ticket link there. May 19th in Sacramento. If you live anywhere near there, come on out. It's going to be fun. Also, I just announced a ton of new dates. So go to jimjeffries.com. There's loads of Canadian dates. Obviously, there's still some Australian dates that have tickets for sale.

Not many of the shows, but some of the shows do. Wollongong, I believe, and some of the shows in New Zealand. The rest of them are done. But apart from that, we've got cool gigs. We've got like Hawaii coming up, Maui, and Honolulu. How did I get on that gig? Yeah. Start doing stand-up now.

I fly the whole family out to the Hawaii gigs. I just say to my agents, I just have to break even. That's how much I like Hawaii. I don't even want to profit off you people. Just come and see the show and I'll be fucking sunbaking. I've never sunbaked in my life. I'll be eating and getting high. You stay in the hotel room and go, the beach looks nice.

I know. I've got my kids. I've got to take them down to the beach and fucking dig holes. That's all I ever used to do as a kid is a beach. You dig a hole. Make a mound. Yeah, you make a mound. And then you've got to protect the hole as the tide comes in.

Yes. Yeah, that's some good quality fun. We're all the same people. If you dig it too far out, then the water's never coming. You've just got yourself a hole. It's not fun. Too soon, too close to the shore. You get overtaken. So you've got to make a trench.

You make a trench, then you make a wall. Then you have to sit in there and see how fucking dry we can stay. And then you bucket out when the water comes. It's good stuff. It's good fun. Just goes to show you, no matter how successful you get, you always want to protect your hole. Yeah. Well, that came out.

I wasn't planning that. Oh, are you Well, that came out. That wasn't planned. Oh, are you sure that wasn't planned? It wasn't planned. You know what's fun to do on the beach? Right. Listen to our Patreon. Oh. It is.

Yes. Patreon.com slash IDCAT. And confirmed, you know, international shipping works for merch. So I don't know about that.com. And follow us on Instagram. International shipping. Yeah.

Man, I'm going to make some merch money like those people who made the April 18th t-shirts. There's someone who's made a million dollars off me. We could probably add April 18th shirts to our merch. I don't know. Someone's probably patented it by now. I don't think you can patent a date.

I don't know. It seems to happen every day. We'll trademark it. We'll figure it out. Yeah, trademark it. Coming soon. 4-20-69. April 18th hats.

Mugs. Shirts. Yeah, April 18th. Still coming. K, trademark advice. Coming soon. 4-20-69. April 18th hats, mugs, shirts. Yeah, April 18th. Toe bags. Still coming. Koozies. All right, let's start the podcast. Well, we started it. Yeah, let's- The real bit that people enjoy.

Let's introduce our guest. Yeah, let's introduce our guest. Let's introduce our guest. Please welcome our guest, Sean Carroll. G'day, Sean. Now it's time to play. Yes, no. Yes, no. Yes, no. Yes, no.

Yes, no. Yes, no. Judging a book by its cover. All right, I'm going to go out on a limb here. Are you a doctor, Sean? I am a doctor. Not a real doctor, but a PhD. Oh, yes, you said too much.

You said too much. Because what happened was when you came on offline, not on the podcast, I'm a bit mental today. My mouth's not working. But Forrest said, do we need to refer to you as a doctor? So I took that as a hint. Yeah, good clue. Add riddles today if you want.

No, I don't want a riddle yet. So he's not a doctor of medicine. He's got a printer. Yeah, yeah, yeah. So he'd obviously print things out. When are they going to make one of those that works? They don't have them right now. No.

Not one that works every time. I've never seen a product in mankind where we all just acknowledge it doesn't work 20% of the time. I've got mine. Brother. It's a brother. Alright, so here we go. He's got something French on his wall. It's not going to help me? No okay i don't see anything give me give me a riddle

give me a riddle oh he has photos he has loved ones okay so that's good it's always good well well done shows it down here's one okay i have two riddles here's the first one never head ever behind yet flying swiftly past for a a child, I last forever. For an adult, I've gone too fast. When am I? Oh, your life. Close. Here's another riddle.

What flies but has no wings? Jack's spirit. What the? No, I'm saying it flies. What flies but has no wings? What flies but has no wings. What flies but has no wings. What flies but has no wings. Yeah.

Fucking everything has wings that flies, man. It can go fast. It can go slow. You can have too much of it. Time, time, time, time, time. I love watches. They're the most pointless thing in the world. You pay thousands and thousands of dollars for a thing that you have to wind up yourself

and then you check your iPhone to make sure you got it correct. And you put your iPhone back in your pocket and you go, Aha, I've got this thing on my wrist now that isn't quite accurate because I didn't set it correctly. Well, let me introduce Sean. Sean Carroll is a theoretical physicist at Caltech. He received his PhD from Harvard University and his research covers quantum mechanics, cosmology, and space time. He is the author of several books, including

Something Deeply Hidden, Quantum Worlds, and the Emergence of Space Time, and also the host of the Mindscape podcast. You can find him on Twitter and Instagram at Sean M. Carroll. His last name is spelled C-A-R-R-O-L-L. So look him up, follow him on there. And Sean, can you tell us, I mean, this is a, you know, how did you get interested in this and end up in this world profession? You know, I'm one of those lucky people who got interested in what I do for a living when I was 10 years old. I was just reading in the local public library books about black holes and particles and general relativity, Einstein.

And I said, this is what I want to do for a living. And I did not have the imagination to change my mind ever since then. Hold up. You did this at 10? You didn't have any Hardy Boys books? Yeah. I'll tell you. I had those too, but I didn't want to do that.

I'll tell a very quick little story right so my son uh he's not he doesn't read for pleasure right but i try to make my son's nine so i go okay you should read for pleasure i think it's important man you don't either yeah but i don't either so how do i make him read for pleasure when i don't read for pleasure so what i do is now i have a book on the coffee table with a bookmark in it, and when I hear him coming downstairs, I turn the TV off and I act like I'm reading. When he comes down, I go, just a minute, Hank.

I go, yes, how can I help you? I'm sure he's fooled. Dad's reading and reading is cool now. Dad just reads in the house for pleasure. What a fucking weird guy. Well, is it working? No, but I've only just started it. I'm only about 10 days into this.

All right. Well, Sean, thank you for being here. Thanks for reading when you were young. Thanks for reading when you were young and being able to be here to talk about this today. What we're going to do is I'm going to ask Jim a bunch of questions. Clearly none of us read when we were young. That's why we do this today. What we're going to do is I'm going to ask Jim a bunch of questions. Clearly none of us read when we were young. That's why we do this podcast. I watch documentaries.

It's like reading. I was reading on the plane yesterday next to Jim. You weren't even paying attention. Alright, so I'm going to ask Jim a bunch of questions about time and then at the end of it, you're going to grade him 0 through 10. 10 is the best on his accuracy. Kelly's going to grade him on confidence. 0 through 10, you're going to grade him zero through 10 10 is the best on his accuracy uh kelly's going to grade him on confidence zero through 10 i'm going to grade

him on etc and here's the categories today jim they're all jokes about time so i want you to see if you anyone can chime in sean kelly here's the if you grow zero through 10 here's the joke what time is it this is the worst joke what time is it when an elephant sits on a clock time to get a new clock all right you got that one that's pretty good we all do that second worst joke very accurate so far 11 through 20 do you know when ducks wake up at the quack of dawn yeah i knew this well we're all out to try i don't know yeah i don't know okay i've never heard i'll give you the next punch line and i won't even ask for the joke. My dentist appointment is 2.30. That's what?

How did you know? That's the classic fucking time joke. That's what? Tell the future? Around what time do most people visit the dentist? That was really what's the last one. At 2.30. 2.30.

You say tooth-hurty. Tooth-hurty. How did you know that was it? Everyone knows that joke. We should just end the podcast now. Ten. I don't know any time jokes. I get a point for that, sure.

Okay. All right. And we're back. We're back. Here go the questions, Jim. Kelly's going to take some notes here, so we'll remind you of what his answers are, Sean, when we go back. How is time defined?

How is time defined? How is time defined? What do you mean? The measurements of it or what would be the. Like if you looked it up in the dictionary. The Oxford dictionary. Okay. Time. That's a good question.

How do you phrase this? I know what it is, but how do you phrase it? Time is the distance of existence. You just want to rhyme something? I mean, that's a cool phrase. If that's accurate, that's cool. Put that on a T-shirt and smoke it. What?

We got some new merch coming. Look, it makes sense. I know that's not going to be the answer, but that makes sense. I don't know. I don't know what the answer is. The distance of existence, man. That sounds cool. What is the arrow of time?

The arrow of time. That is pointing forward. Time's always moving forward. Time never moves backwards. What is entropy? Can you put it in a sentence? Yes. What is entropy?

Can you put it in a sentence? Yes. What is entropy? Entropy is when we invented the measurements of time. Are time and space related? Time and space are related, yes. Okay, great. Why is time different than space um well space yep is is the amount of space you

have i already warned him that you were going to try to do these words are hard though these are like the belly blocks space is the amount of volume in the world and time is the length that that volume travels i just want to say that i've we've done a hundred over a hundred podcasts now i believe these are the hardest questions yeah because you know you know what it means but you don't know how to say it's very hard it's very hard to answer these questions without using the word that you you were trying to answer with there you go what is presentism i have no idea what is eternalism eternalism is uh that time is eternal long after the universe implodes into a thing time will still be there time never ends time is eternal it keeps on ticking ticking ticking into the future here's one where you might get a point. What is the theory of relativity? Who created it and when? The theory of relativity. Who created it and when?

There's a point in here that I think you should get. E equals MC squared. Is that relativity? And that was Einstein. He invented that in the 1930s. Okay. What does it mean when people say time is an illusion? That's always some old bird who thinks she looks like she's 30 but she's really 50 and she's out and she goes time's just a number and you're like and look how do how do we measure time through wrinkles it depends you know tree stumps you cut them in half you count the rings otherwise we we measure time through uh with watches and stuff like that seconds 60 seconds make a minute 60 minutes make an hour and so for 24 hours in a day okay i've got five

more questions here oh another way to measure time is how long it takes for the planet to go around, the sun. These are things that we measure, you know, because months are an amount of time. Days are an amount of time. You know, years are an amount of time. So I would say through the solar system is a good way for us to measure time. But also through the sun rising,

the fact that people have had sundials since, you know, for a very long time. Define clock. Clock is a measuring tool on which to count time. And now name as many things that act as clocks as you can. You're kind of doing that. Watches, phones, sundials. Watches, phones, sundials um watches phones sundials big clocks like big clocks grandfather clocks uh what measures time uh years measure time weeks measure time

seconds i mean you are talking actual implements or? Name as many things that acts as clocks as you can. Acts as clocks. Fucking having kids, man, that measures time faster than anything. I tell you what, I never measured time before then. Yeah, kids. Can you slow down time? This is a trick question. The answer is no, you can't slow down time. But every now and again, there's something that happens

with the solar system going around and we lose a second. So there are certain years where we lose a second here and there. What about Superman? Superman flies backwards. It makes everything else he does irrelevant. Okay. He just can spin so fast that the planet goes backwards. Yeah, nothing would happen other than that.

To the planet going backwards, yeah. You can stop can stop time daylight savings that always springs up on you doesn't it yeah you're like oh i'm gonna have a lovely sleep no you're not here's a question i can't wait to hear the answer to why is the past different than the future oh uh because the past is no knowledge where the future is not wow because the past is no knowledge where the future is not. Wow. Because the past is known knowledge. That goes in the back of the existence. Distance of existence. Yeah, that's the other part of the answer.

That's not a bad answer. No, it's not. That's why it's going under the shirt. Last question. They don't teach the past in school. They don't teach the future in school. That's true. They teach the past.

Or the past sometimes. They teach history. They don't teach the future. What school? What past? Judah Friedlander has a joke where if he's asking someone in the audience, what do you teach? And he goes, history.

He goes, yeah, I teach the future. It's a lot more difficult. Last question. Is time travel possible slash real? I don't believe it is, but some people believe it is. The reason I don't believe it is, is because we would have been visited by somebody, a time traveller by now, but maybe time travel can only be invented from now

and then we can go backwards and not forwards and then maybe the forward world isn't existing yet. You get what I'm saying? No. I don't believe it is real, but people are going to say it is. And then there's the black holes. You can go into a black hole and shoot out somewhere else. So there is arguments that you can bend time and time travel is possible,

but I don't believe it is. Okay. Sean Carroll, how did Jim do on his knowledge of these questions and times? Zero through 10, 10's the best. You know what? I thought that he started a little slowly, stumbled out of the gate, but came on really strongly there at the end. So I'm going to give him an eight just for the brilliant answer on time travel.

I like that. I think the kid clock is what did it. It's the time travel answer because this joke that if time travel really existed, we'd be visited from historians from the future is exactly a joke made by Stephen Hawking. So if you're making the same joke to Stephen Hawking, then you know, you know what you're talking about. Actually,

you got it better because you, you also explained the loophole in the joke, which Hawking never did. Yeah. Wow. Jim, you must be smarter than you think. Okay.

How do you do on confidence? Kelly? Uh, four. Four. Okay. That's 12. I'm going to give you a 10 and et cetera for 22.

So around what time do most people visit the dentist? Tooth hearty. I do enjoy going online and watching some time-traveling videos where they think people have time-traveled. There's always just like a bloke, like in an Ed Hardy T-shirt in 1940. You know what I mean? But there's one that spins me out. It's during a Tyson fight in the early 90s.

There's someone with a camera phone in there with it, with an iPhone. It must've been something different, but it was a good one. Well, and that's the thing too. It's like photo. If,

if anybody ever approached you and said, Hey, I'm a time traveler and I came here from 3000, would you believe them or think they're fucking nuts? You would be like, okay, go away. I listened to everybody.

Do you know? I always like there's, go away. I listen to everybody. Do you? No. I always like, there's an advert for insuring in money or something like that, and there's like a guy walking down the street and then another guy walks up and goes, hey, I'm from the future, and I'm you from the future, and you should invest in these stocks and all that type of stuff. And the guy's like, wow. And he goes, by the way, your future wife's in that bar right there

and the guy just smiles i'd like the ad to end like this so run yeah he walks past the bar he's like not going to never go in that bar okay uh let's talk to sean here uh how is time defined jim said time is the distance of existence not bad man i man. I do like that. And a couple of times, Jim used the idea of thinking of time as a measure of distance, which actually was never done back in the day. Like if you're ancient Greek philosophy, we didn't talk that way. But post Einstein, when we think about space time as one kind of thing, we do think of time as a kind of a distance in space time. So I wouldn't, that's one way of thinking about it,

but I think it's perfectly valid. There's an Australian artist called Peter Allen, and he had a lyric that said, time is a traveler. And I believe time is a traveler. Do you want to know why? Right? Because when you move away from home and you go off to England or whatever I did for 10 years, and then you come back, fucking hell, everyone's old. Like you didn't really notice it. Like your

parents are like old people, all the newsreaders, like what the fuck happened to her? I used to wank off to her. She's old as balls now. Right? Yeah. Time's a traveler, man. So how would you define time then? Well, we use the word time to mean different things. One is just a way of locating ourselves in space time, right? If you say like, you know, meet me at seven o'clock, that's a coordinate. It's a label. It says, you know, at this particular reading of the clocks, I should go there and you'll be there.

But the other thing is that there is sort of a counting of things that happen, right? The number of heartbeats, the number of swings of a pendulum, the number of times the earth goes around the sun. The world happens over and over again. And time is the accumulation of all those things. That's why I was giving Jim some points for that. Did we always measure time in minutes, seconds, hours, weeks? Or was there another measurement back in the day where you look back at it like, what were they thinking? That was three whole grogs. Correct. No, I mean, astronomy was the first way of measuring time, right? Where's the Earth in the sky?

Where are the stars in the sky? The division into hours and minutes and seconds came with the Greeks. Before then, I just don't know what they did. Yeah, but they must have always known what a day was because of the sun. They must have always known a day. And we need a certain amount of sleep with every sun coming up. I need to sleep.

Yeah. And the weather. They certainly knew what the year was. You need to know what a year was to do farming. And they, instead of months, they knew where the moon was in the sky, right? The moon takes around a month to go from full moon to full moon again.

Right, right. So what is the arrow of to go from full moon to full moon again. Right, right. So what is the arrow of time? Jim said time is always moving forward. It never moves backwards. A lot of fortune cookie answers here at the beginning. That's not wrong. But the arrow of time is just the fact that the past and future are different from each other. The fact that there's an asymmetry there.

And it's kind of a mystery. Again, it was not a mystery back in the ancient world, but once we invented modern physics, the equations of physics from Isaac Newton through Einstein, et cetera, don't tell any difference between the past and the future. They treat them exactly the same. So there's a mystery within modern physics

as to why you have photographs of the past but you don't have any photographs of the future why history is easier than futurism and entropy as jim said when we invented the measurements of time yeah that's not right entropy is a measure of the randomness or disorderliness in a system. So, you know, if you have a deck of cards and it's perfectly in order to through a king through ace, then it's low entropy, it's orderly. And then when you shuffle it, the entropy goes up. So this is a general feature of the universe that entropy always goes up. If you count everything, things go from being orderly in the past to being more disorderly in

the future in that deck of cards is uh all set on time all on the calendar so there's 52 cards 52 weeks four seasons four decks of cards 12 things in a in a suit yeah it's all based on the calendar yeah the entropy thing's interesting because that's like i like to i like to keep my house really clean but then it always gets dirty immediately as soon as you're done cleaning it and like the whole universe is working against you keeping things it's a law of nature yeah what can you do yeah that's just not be such a slob when he eats i guess i'm not i'm pretty neat he lives by himself it's only you making it messy you like, I clean this place up and then it gets messy. I turn around. What? As soon as you vacuum, then some dust is coming down.

Yeah. I have OCD. I have OCD. Are time and space related? Jim said yes. And I said, why is time different than space? Well, space is the amount of volume in the world and time is the length of the volume travel. So let's talk about space and time, I guess.

Well, they're definitely related. They're both ways of finding yourself in the universe. Again, if you're going to meet somebody, say not only 7pm, but you got to tell them where, right? You got to give them that information. Back in the days of Isaac Newton, you just thought of them as two separate ways of finding yourself in the universe. time and space are both part of space time. And again, it becomes sort of a question as to why we all agree on which is time and which is space. Because if we were moving near the speed of light, that would not be so obvious. We would mix things up compared to each other. I got to tell you, you're doing a good job of explaining this, at least to someone that doesn't understand this. This is already easier than Bitcoin.

It just is um what is presentism jim said no idea no idea well you might have gotten it if you had asked the eternalism question first you know eternalism is the idea that all of the different moments in the history of the universe are equally real right it's not just that right now is real. So the past, present, and future are all real. We're just at any one moment. We only experience one moment, but that doesn't mean that there's no reality to the past or future. Whereas presentism is the opposite of that.

It says that just the present moment is real. The past is just a memory of that, and the future is just a hypothetical prediction. I would have gotten that, but Forrest fucked me on that one, didn't he? Because he did. He asked it the wrong way around. Do you believe in different lines of timelines, like in movies? Multiverse. Multiverses? I do, actually, but that's optional. We don't know for sure, but that's a quantum mechanics question. Within quantum mechanics, there's very good reasons to believe that whenever you measure a tiny microscopic quantum system, you branch the universe into different timelines with different measurement outcomes. And there again, they're all equally real.

show on Marvel? I did, but I don't think the Marvel Disney Channel shows are the best introduction to the multiverse, but you could do that, or you could buy my book. Either way. What movie would you say is the most accurate time-traveling movie where you go, if it does

exist, that's the way it would be done? Probably 12 Monkeys. Monkeys. I, Monkeys. I love that movie. I haven't seen that movie in years. The point is that if you could travel into the past, you still couldn't change it. This is the problem with all time travel movies.

You generally go into the past and you like fix something, right? But you probably can't do that. And if you look at the logic of 12 Monkeys, everything that is shown in the past is also reflected in the future very accurately it is almost the case in avengers endgame also i i have to admit and well i'm not just admitting it i'm bragging about it because i helped influence them i was a science consultant on that movie if you're going to travel to the past don't mess with it and and ant-man says that that's exactly right that Back to the Future is just bullshit you can't do that and that that takes

away any of the appeal of time travel really because isn't the point to go and fix things in the past but if you just have to go watch it it's got to check it out man it's got to check it out well you can't go back and kill your love yeah I don't think that that's the only point it's like saying why have detective TV shows because

they can't undo the crime it's still interesting to figure out what happens with the crime half the time yeah i i believe in in time travel if it exists would be more like the back of the future where you can only stay on the same plane that you're on like you i don't like time travel where you go i'm gonna go back to ancient greece in 1840. You know what I mean? Like you can't travel through time as well and space. You can't travel through time. Like the time machine, the original one where the guy just sat there and the candles go down.

I love that film when I was a kid. Which film? The time machine, the original one. And he had a big disc behind him and he sat in a chair and it went. Everything just started moving. HG Wells. Yes. I'm moving around him. Bit of fun. Wait, is it really complicated reason why you can't go back to the past and change things?

I'm kind of confused on that. Why you can't? It's not a complicated reason. It's an easy reason. It already happened. That's why you can't change it. If you're back there, can't you do the butterfly effect and then you do something and then the whole world changes? Everyone's always like, you go back in time,'t you do the butterfly effect and then you do something and then the whole world changes? The big one is kill Hitler.

Everyone's always like, you go back in time, you kill Hitler. Yeah, of course. The Holocaust doesn't happen. And then Bitcoin. Yeah. I just want to go back and tell my young self not to be a knob. Can I do that? Or is he always going to be a knob in every fucking timeline? No, that answers that question.

So you can't go back and kill hitler and then back in time you could do that well look if you did go back and change the past you might go back and change it so dramatically that you never came into existence in the future and then who was it who went back to fix things and the answer is you can't go back and change the past and that makes sense now because then you wouldn't be born and then you wouldn't. Yeah. What if you're just like stuck there? Oh, wait, wait.

So you can't go. You shouldn't go back and change the past. But if you did change things. You can't. You can't. It already happened. Can't do it, Jack. Answer me this question, Sean.

So why didn't Biff notice that his stepson looked like Marty McFly? Didn't Biff notice that his stepson looked like Marty McFly? Like that seems like that's a red flag right there. There's a Hollywood question, not a physics question. I can't help you with that. I don't want to get bogged down too much in movies, but you know what movie I like time travel on? And cause I'm into like chick flicks too, is the time traveler's wife.

I like that one a lot. Yeah. But she was always nagging. How long are you going to be here? What time are you going to be back? I'm going to be back in 1984. Shut up. Which side of presentism or eternalism are you on? Do you have a...

I'm an eternalist myself. I think that the past, present, and future are all equally real. I think there's a lot of things that are real out there that we don't get to go visit. Yeah. If you could travel in the future to anywhere at any time, where would you go and why? Well, you can

travel to the future. The joke is I did it yesterday and here I am today, right? The question is, can you travel to the future faster? And the answer is, again, yes. Einstein taught us how to do this. You zip out near the speed of light and you come back. What you can't do is return.

You cannot return back to the present day once you go to the future. Why can't you go at the speed of light backwards? Like when you're fast-forwarding too much and you go back a bit. Oh, I've gone back too far. Oh, they're out of sync. There is no reverse rewind button on the universe. It only goes so much. Why is there only a fast-forward then?

No, because it's like when you travel to Australia, you lose that time on the universe it only goes why is there only a fast forward then well because no because it's design flaw it's like when you travel to australia you lose that time on the airplane even though you're existing i'm a time traveler i've been to australia a lot even though you're existing on that airplane you're just on the airplane and then you go forward that day but when you come back you usually come back an hour earlier now you come back a little you come back a day yeah yeah something like that you lose a day you gain a day i never i don't know and did i get the theory of relativity right but isn't that's the next question that's splitting the out of right theory of relativity who created he said e equals mc squared einstein 1930s

so it was not the 1930s it was einstein and said there were other people involved and e equals mc squared is absolutely part of it it's not the only part it's the basic idea that space and time are glued together into space-time. That's what we call special relativity. And then there's general relativity. Special relativity was 1905. General relativity is 1915 and says that space-time is curved. And it's that curvature that we feel as gravity. When you see the Earth going around the sun or apples falling from trees, it's because gravity is curving space-time itself and things are doing their best to move on straight lines but they can't because they're in a curved four-dimensional space-time the apple falling out of the tree and hitting him on the

head everyone talks about that like it was a magical moment but didn't he see other things fall before it smashed him in the head this is an excellent question so the point is not that people had never seen apples fall from trees or didn't know what to do about it. What Newton's Isaac Newton's insight was that the explanation for apples falling from trees is the same as the explanations for planets moving around the sun. It's the same force of gravity that is responsible for both.

Here's a, as a theoretical physicist, have you ever written any sort of equation on a window because whenever i see it yeah why are you guys always writing on windows getting the hard to figure it out by getting a a pin board and putting a whole lot of red tape red string red string and crime yeah that's. You have to find out why he did it. It's a theoretical. It's a mystery.

It's a detective. This is more a Hollywood question than a physics question. But yes, I haven't done it actually. Certain places, just for aesthetic reasons, do have windows and clear things you can draw on. But most of the time it's blackboards and whiteboards. Yeah. And dry erase markers probably work well.

I'm going to ring up Russell Crowe and ask why he did it. I once had a joke about russell grow and then he asked me he goes like this he goes i heard you do a joke about me what's the joke and the joke was just before i ever met him was i went and saw the movie noah i'm not religious so what i did was i just thought it was a beautiful mind too. And the guy really grew on crazy. Oh no. What does it mean when people say time is an illusion? Jim said, that's just when some old bird who is 50, but thinks she looks 30.

Yeah. That's pretty accurate, man. That is not very accurate, but I don't agree. I do. I do. I don't think that time is an illusion i know why people say it because you know because they become eternalists because you think about physics you start thinking

that all moments are equally real and then you think start you go a little bit too far you go one step off the edge and you say well if all moments are equally real then time itself is not even real. The passage of time isn't real. There's just all the moments existing. But that's just wrong because, you know, we have space. All moments, all points in space exist. But we don't say that space is therefore an illusion.

Time is maybe not what you thought it was 2,000 years ago, but it's absolutely real. What about the theory that we never die because atheists have this theory? You never die because you'll never experience death because you won't know it happened because you'll be dead. So your brain basically will think that it's always living forever. I've never heard that. No, you won't know you're dead. You're not going to live forever. I'm not saying you live forever, but your brain won't. Your brain never concedes.

It'll never concede that it's dead. I think that that theory assumes that dying is instantaneous rather than kind of gradual where you kind of know. Oh, no, no, no. Your brain will be like, I think I'm dying. And then you'll always think that for the rest of eternity. So you're'm dying. And then he'll always think that for the rest of eternity. So you're forever dying. Well, that's interesting,

Sean, because it's, I feel like now when you said that, you know, like when you're watching TV and you fall asleep, but you're still sort of watching TV and then you can hear it in the background. That's probably what dying is like.

We're like, Oh no, here I go. Yeah. But the thing is you won't know the exact moment. True. But you also will be unless it's instantaneous like if you're dying a slow death and you'll be like oh this is it and then yeah

and then you're like then you're constantly like this is it i'm an atheist i'm i don't believe in heaven or hell or anything like that but it's dying still scares me still yeah i still scared why wouldn't it yeah because it's nothing to do with it's scaring you and i there's also, there is a heaven hell thing if you're religious, but you know, still, you want to live. I don't think anything will happen afterwards, but it's like, yeah, it's pretty finally all dying in it. Yeah. But you won't, you won't know what happens.

Yeah, yeah. I'm going to live forever. I do think it is interesting how time is so often a perception, right? Like it can move really slowly in certain points in your life and move really quickly. That's what is really kind of freaky about time. It's like, I imagine being in prison, time moves very slowly because you're bored. And then when things are exciting, you know, time moves really quickly.

Well, there's a saying with children that the, uh, the days along the years are short and that's the truest thing about pairing, I can tell you. That was part of the riddle. Yeah, each day you go, fuck, you're getting to bed, that took forever. And then you're like, fuck, he's 10. Yeah. Yeah.

You know what I mean? It goes really quick, their childhood. How do we measure time? Jim said through wrinkles, tree stumps, watches and stuff, seconds, minutes, hours. How long does it take for the planet to go around? Yeah, through clocks. I mean, that one is basically correct, right?

There are things in the world. If you want to measure it rather than just know that it's passing, the wrinkles aren't very good because you cannot go exactly from the existence of the wrinkles to a moment of time or an interval of time. What you want is something that does the same thing over and over again in a repetitive reliable way that's why the earth going around the sun is very good a grandfather clock with a pendulum rocking back and forth is very good atoms vibrating at certain frequencies they're very good these are reliable oscillating things and those are what let us measure the passage of time i thought tree stump was a good answer for you too jim because when you go that's a good one when you go to uh like any of the redwood or sequoia for us i always have that one cut in half and they have all the arrows like here's

the birth of christ here's it has all this you know the really old trees yeah i i have been mugged twice in my life i won't mention the first time the second time i got mugged was a very placid mugging where I had a watch that was maybe $400. Nice watch, you know what I mean? But I got mugged for my watch. Now, here's the place I got mugged. I got mugged in Greenwich for a watch.

Doesn't that blow your mind? Because that's where time is measured from. Holy crap. I wasn't thinking Greenwich Mean Time, yeah. I got mugged in Greenwich for a watch. I was new york city greenwich village anyways that's no no greenwich meantime yeah okay yeah well yeah but it's very important there bit of irony is that irony coincidence yeah just a coincidence yeah but i thought it was quite interesting at the time i remember walking away from the mug and going, we all learned something here today.

So that is the definition of a clock then, just a measuring tool on which to measure time. Jim, this is where Jim was crushing it in points here. Well, in particular, it's something that does the same thing over and over again in the right number of steps compared to other clocks. It's kind of a circular definition, but that's what we got. There's a guy in my neighborhood, Literally, you can measure time by him.

Every morning. His name is Manuel Rolex. At 7 a.m., he starts his walk. He does this whole walk around the thing. If you're there at the right times, you'll see him. He goes to the corner store, right? Because it opens at a certain time. He's like...

Animals know time. They know when you're going to be back. My dad has two birds that visit him at the same time every single day. Yeah. They got their internal clocks. Yeah. I don't know.

That's a term. Yeah. Your internal clock, your circadian rhythms and all of that stuff, I assume, would be a measurement of or some form of clock, right? Yeah. No, your body is full of clocks. Like I said, your breath, your heartbeat. But then also there are pulses in your brain in your nervous system there are changes in your chemicals through the day that you know

when you're awake when you're tired etc and so they're not as reliable as atomic clocks for rolexes but you absolutely feel the passage of time and there's also psychological passage of time which can depend on lots of things a big thing for the psychology of time is, are you experiencing something new? When you're experiencing something new, time seems to move quickly because there's so many new things coming at you. When nothing is happening and you're bored, you're like, ah, this is taking forever. Right, right, right. The DMV. Yeah, well, it it's their clocks don't

work it's when anytime you go shopping and you see somebody who's just sitting in like a purse store that nobody's visiting some of my friends would be like oh that's that's an easy job and i'm like that would be fucking awful like i would want to if i'm going to work retail i want to work in a really busy store where the day goes by quickly. Cause you have a lot of things to do. Like you get your job at the dollar shop. Okay. All right. I love the dollar store. Check out chicken Whole Foods,

man. That that's a, that's a tough job. That's why. And they don't have clocks in casinos. They don't want you to know what time it is. And malls. Yeah.

Malls don't have clocks. Nope. No, malls have clocks. I'm saying, I don't know. My mom told me that this could be a, some malls. Jack's mom. What are you doing? I don't know about that. Um, can have clocks. I'm saying clocks have moles. I don't know. My mom told me that. It could be a... Some moles.

Jack's mom, what are you doing? I don't know about that. Can you slow down time? Jim said, no, you can't. But every now and again, there's something happening in the solar system where we lose a second. Well, it's completely true about the leap second,

as we say, because the Earth going around the sun and the Earth rotating is not as reliable as you would like. It's not as reliable as modern physics ways of measuring clocks are. So there are leap seconds that sort of adjust the number of seconds in a year. But I actually,

I liked the answer that you can't slow down in time because many physicists would say that you can, but I think they're just being sloppy. If you go out near the speed of light and then you come back, you know, you age a different amount than if you stay back here on earth. And some people will say, well, that's kind of like changing the rate at which time flows but the person who goes out when they're looking at their watch or whatever they see still see it ticking at one second per second there's nothing different about that so i like the short and

simple answer no you cannot change the rate at which time flows okay so we can't travel at the speed of light we can break the sound barrier we can't travel at the speed of light. We can break the sound barrier. We can't break the light barrier yet, right? Do you foresee a time where we can and we will have time travelers? No, that's the laws of physics in the way. The speed of sound is just a convenient thing to measure, but the speed of light is really something you can't go faster than. Right, but it is a speed, right?

Because we see the sun takes like 10 minutes the rays to hit us right yeah and so it's a speed and you can never go faster than that how far can you can you give us the actual speed how many miles an hour is is light i don't know miles per hour it's 300 000 kilometers per second per second that's pretty fast. 300,000 kilometers. Isn't that your 100 meter time? Yeah. 3,000 kilometers? 300,000. It's only like 160

thousand miles. I'll tell you right now what it is. Well, Elon Musk just bought Twitter, so anything's possible, guys. It's 186,411 miles per second. Yeah, it was. That's pretty fast.

It'd be a good way to travel. All right, well, let's get working on that. Yeah, I know. You'd be like, oh, I got to go to Cleveland this weekend. Who cares? Getting in there in.0000001 seconds. Yeah. That is the type of time travel that I wish there was.

I don't want to go to any other timeline or anything like that that but i do wish there was a way that you could just snap your fingers and be in a different place teleporting would yes teleportation is what i'm very interested in i'll never quit stand-up comedy if teleportation becomes yeah you just show up i'll just walk out and then dressing out and if i can tell jokes and go back to my living room yeah exactly now that is unfortunately space travel not time travel yeah i'd like space travel i would like space travel they gotta put comedy clubs on other planets all these people that go we need to colonize mars and all that let's just let the planet die we can all just die we don't need to go to mars they're a red fucking rock where nothing grows and live a shitty existence.

We already have the Red Rocks Casino. Yeah, just die. Just go, ah, well. I'll beat. Thanks, Earth. We had a good time. I'm usually the nihilist on this show. I'm trying to take my bits.

What, you want to live on Mars? You think you're the nihilist on this show? I'm always talking about how I want to die. Luis doesn't even talk. Luis is upset. Time's traveling slow for him today. Why is the past different than the future? Jim said, because the past is known

knowledge where the future is not. They don't teach the future in school. Good answer, right? Those are all true statements. They're not quite the reason why. They're ways in which the past is different from the future. The reason why is because entropy is increasing. I mean, that's the interesting thing. This is a research-level question in modern physics.

It's easy to say that things go from order to disorder. You can scramble an egg, but you cannot unscramble the egg. Then that's a manifestation of entropy increasing. And we think that that increase of entropy is the entire reason why there is a difference between past and future, why you have memories of the past, why causes precede effects, why we're all born young and grow older. But we don't know why when the universe started, it was so orderly and low entropy in the first place that's a that's a mystery to us right now so that was the big bang there was just like zero entropy and then now it just completely is disheveled at this point it was very very low

entropy yeah we don't know why yeah we had that we did an episode of memory did we yeah yeah and i get it and uh i also don't remember i don't remember we loved that we loved that one of the big things i took from that was about she was saying that um that even people that we think have good memories or they think themselves have good memories like that all memories are everyone's memory is probably worse than you think if not really but yeah i was in calgary the other day and the lady who picked us up uh with my friend tommy campbell who was opening for me um talked about when the three of us went go-karting together yeah i don't remember even meeting her i'm like i thought go-karting is something you should remember.

Go-karting. I franged around a track with a helmet on my head, and I have no recollection. Yeah, that memory episode was, and then I'm coupling it with this timeline right now, and I'm just like, yeah, all right. I guess nothing matters. The present is a gift time traveling that's why it's cold now

we kind of already talked about this at length at the beginning is time travel possible real Jim said he doesn't believe but we kind of covered this I feel like already we did we spent a lot of time on that let's talk about oh sorry he talked about the black hole and you kind of nodded when

he when he was talking about going into a black hole and shooting out somewhere else maybe we can talk about that well the the short answer is we're not sure whether or not time travel is possible we think it's probably not i am the simple answer is that it's probably not but there have been proposals for how to do it you know if you if you put aside your love for Back to the Future and think about Interstellar, for example, where there's a wormhole that takes you across space and changes your perception of time. That's all. It's not exactly completely realistic, but it's based on ideas that are real physics. So we know how time travel might work if it is possible, but there's a lot of reasons to think that it's just not possible in the real world anyway.

Is time different on other planets because the moon moves differently, it goes around the sun differently, or whatever their sun is? So would a second be longer or something, or is time a constant throughout the universe? Time is, as far as we can tell tell constant in the sense that if you built an atomic clock, it would work the same no matter where you put it. Of course, if you build a pendulum clock on a planet where the gravity is different,

then it would work differently. But you know, that's just your bad design sense rather than the flow of time being actually different. Sun dials would be different, things like that, but they would be. Yeah.

Calendars would be different, but, but the number of oscillations of a cesium atom would be different things like that but they would be yeah calendars would be different but but the number of oscillations of a cesium atom would be this thing right like i said right yeah what did he just say he just said that it'd be the same a clock works the same no matter where you fucking put it unless there's a pendulum involved that involves gravity if i put this watch anywhere it would still work the same actually it wouldn't this is a i think this is a motion thing. Archaeopteryx. I'm so lazy that I lie down one day and my watch stopped ticking.

Because it has the... I masturbate with my right hand. I wear my watch on the left. I know what happened. What's your main focus when you study time? Like, what's the main thing you are trying to figure out as an individual or the thing you're most interested in? Yeah, it's probably this arrow of time business. Why all of these ways in which the past is different from the future, how they all trace

back to entropy increasing. When you think about cause and effect, if you swing your arm and you knock a wine glass onto the floor, right, it's very natural to say the reason why the wine glass fell is because I swung my arm and I hit it. It is very unnatural to say I swung my arm because the wine glass was going to fall. We don't put causes in the future and effects in the past. And so why is that? Right. I mean, this is a question at the boundary of philosophy and physics, but it's a fascinating one that we don't completely understand the answer to yet. Would that hold up in court, though? Could you say, I stabbed that knife because she was going to die anyway.

She had a stab wound in her, so I stabbed her. I had to fill it in with a knife. I like the wine glass one. So next time I knock something over, I'm like, yeah, I swung my arm because the wine glass was going to fall. Then knock it over. Tried to catch it. It's a fun party trick. Time it up.

Yeah, yeah, yeah. Your carpet was already dirty. It's already had the stuff on there. Okay. Here's a part of our show, Dinner Party Facts. We ask our expert to give us a fact, something obscure, interesting that our audience can use to impress people about this subject.

I have two. I have an easy one and a hard one. The easy one is the word time is the most used noun in the English language. Wow. Yeah?

According to the people who make the dictionaries, there you go. What, the herb or the actual measurement of time? I don't know. It is used all the time. It is used all the time. It's the most used noun, right? Obviously, like, the is used more often, but it's the most used noun in the English language.

Oh, wow. And I think in almost all other languages, there's a similar word. There's a lot of songs about time, too, now that I think about it. So I guess that's, yeah. I just thought of a couple. The Pink Floyd song's called Time. If I could put time in a

bottle. Prince had a sign in the times. Yeah, there's lots of songs with time in it, right? More than the time. The most used's lots of songs with time in it, right? Ah, more than the time. The most used now. I know, I'm confirming. You say this all the time. And then the second one.

You want the hard one then? That was the easy one. We just mentioned the fact that the most precise way to measure time, the best clock that we have are atomic clocks, where you really look at the vibrations of a certain atom. It happens to be a cesium atom. Okay. So this has been true for over 50 years. We've used this particular physical phenomenon, vibrations of a cesium atom to measure time, but we're changing that right now. Like right as we speak, they are the physicists of the world are in the process of switching over

from using atomic clocks to using what are called optical clocks. So we're changing the definition of a second to be a little bit more precise right now. Also time zones. They mustn't be that accurate, right? Time zones, zones depending depending on where you're situated in the time it's always like a jagged line like squiggly mountain time zones are all gerrymandered who figured out them

well it used to be that you would just use the local time depending on where the sun was but what that meant was that, you know, Los Angeles and Las Vegas would have different local times or, you know, Los Angeles and San Diego because they were a little bit different in longitude. So that turned out to be more inconvenient than just grouping them together in chunks of one hour each and calling it a time zone. Is that the government that figures out those lines

or is that scientists that got together for that? No, scientists would do a much more sensible job than what we actually have. It's definitely the government that figures out those lines or is that scientists that got together for that? No, scientists would do a much more sensible job than what we actually have. It's definitely the government. You know, like Adelaide in South Australia. This is dumb. What you're about to say is dumb.

They have a half hour difference. Terrible. Because when you're traveling in Australia, now it's a half hour or an hour and a half. That makes me sick. Yeah. It's quite confusing. It's terrible.

Well, and there are some places like Indiana that don't do daylight savings time. So sometimes they're in Eastern time. Sometimes they're in Central time. Arizona does it too. And then they haven't gotten together with like the satellite radio or your phone yet. So if you're traveling through there, you're like, does my phone update to this? And then you're, yeah, it's the worst. there's towns in Australia where the timeline goes through the middle. Yeah.

So if you're like, you're a plumber, you have two one o'clock appointments and two, you know what I mean? Like it's very fucking difficult. Oh my God. That's why they say time is an illusion. Yeah.

At that point. Yeah. Well, I guess we've learned everything there is to know about time. Um, no, I, I thought you explained everything.

It was like, great. I thought you explained everything. It was like, great, the way you explained it. Because sometimes we have complicated subjects. Except for Jack. Jack's brain melted at some point. I don't remember. It's in the headphones now. It's all oozed out. Okay.

Yeah. Pardon the pun, but thank you for your time, Sean. Sean, you can find him on Twitter and instagram at sean m carroll and uh his podcast is called the mindscape podcast and uh he's got many books i believe this was your last book something deeply hidden quantum worlds in the emergence of space time you can find on amazon and other places that you want to buy books what's your podcast about mindscape i mean i'm assuming yeah every week i just interview someone smart about some big ideas you know it'll be about physics but also biology uh neuroscience philosophy sometimes

politics i just interviewed daniels who are the directors of everything everywhere all at once the new movie about the multiverse that just came out don't hinting. I'm happy to do your podcast. Is this the dumbest podcast you've been on? No comment. I don't want to insult anybody else's podcast. All right, Sean. Thank you for being on the podcast. Look, ladies and gentlemen, if you're at a party and someone comes up to you and goes,

I hurried here. I traveled here at the speed of light. I don't know about that and walk away. Good night, Australia.