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Hey or hey, I think it's time we confronted a really tricky topic.

Hey or hey, I think it's time we confronted a really tricky topic.

Do you think we have time for that?

Do you think we have time for that?

You know, there's no time like the present.

You know, there's no time like the present.

It could be a good time.

It could be a good time.

It might be a fun way to pass some time.

It might be a fun way to pass some time.

All right, I'll make time for it.

All right, I'll make time for it.

It's about time. So, Cory, how many time puns can one fit into a single podcast?

It's about time. So, Cory, how many time puns can one fit into a single podcast?

That's right? How much time do you have?

That's right? How much time do you have?

I've got time.

I've got time.

I think it's a timely set of puns.

I think it's a timely set of puns.

Well, you use that pun time after time, nothing else.

Well, you use that pun time after time, nothing else.

Now's the time to start the podcast.

Now's the time to start the podcast.

Now's the time to tackle this tricky topic. I am Horehe and I'm Daniel.

Now's the time to tackle this tricky topic. I am Horehe and I'm Daniel.

It's time for our podcast, Daniel and Jorhe Explain the Universe, a production of iHeartRadio.

It's time for our podcast, Daniel and Jorhe Explain the Universe, a production of iHeartRadio.

In which we take everything about the universe, the now, the future, the past, the deep, deep, deep past and try to explain it to you.

In which we take everything about the universe, the now, the future, the past, the deep, deep, deep past and try to explain it to you.

That's why we take the time to take a little bit of your time and maybe get you to understand a little bit more about this amazing and spacious place that we live in called the universe.

That's why we take the time to take a little bit of your time and maybe get you to understand a little bit more about this amazing and spacious place that we live in called the universe.

That's right. And sometimes we like to grapple with topics that are sort of obvious, you know, sort of things that are right in front of you, and understand like does physics know how to make sense of it? Does physics have a good definition of it? Do we understand why it's this way and not that way?

That's right. And sometimes we like to grapple with topics that are sort of obvious, you know, sort of things that are right in front of you, and understand like does physics know how to make sense of it? Does physics have a good definition of it? Do we understand why it's this way and not that way?

That's right. And so today we're tackling a topic that is probably in everybody's mind all the time.

That's right. And so today we're tackling a topic that is probably in everybody's mind all the time.

That's right. This is something you think about every day from when your alarm clock goes off to when it's time to go to bed.

That's right. This is something you think about every day from when your alarm clock goes off to when it's time to go to bed.

To stay on the podcast, we will be talking about time.

To stay on the podcast, we will be talking about time.

What is time anyway?

What is time anyway?

Yeah?

Yeah?

And why does it only go forwards?

And why does it only go forwards?

Why do you remember the past and not the future?

Why do you remember the past and not the future?

Can you remember the future? That would be pretty cool.

Can you remember the future? That would be pretty cool.

Well, that's the whole question right on one hand, very intuitive understanding of time. We all know what time is, right, Yesterday was yesterday, tomorrow's tomorrow, right now is now, But when you get down to it, we don't really understand why we have it right. Why is it like that? Why does it only go forwards? Why is the future different from the past.

Well, that's the whole question right on one hand, very intuitive understanding of time. We all know what time is, right, Yesterday was yesterday, tomorrow's tomorrow, right now is now, But when you get down to it, we don't really understand why we have it right. Why is it like that? Why does it only go forwards? Why is the future different from the past.

Yeah, it's weird to think that we are in the press and right now and there's a past going backwards in time and there's a future going forwards in time. But what's really the difference between those two things?

Yeah, it's weird to think that we are in the press and right now and there's a past going backwards in time and there's a future going forwards in time. But what's really the difference between those two things?

Yeah?

Yeah?

Why can't I see or feel or have any kind of memory about the future?

Why can't I see or feel or have any kind of memory about the future?

Yeah? Exactly what makes it different? Why is the past fixed right? Unchangeable? Unless you believe in crazy science fiction time travel stories, which I don't and the future undetermined? Right, what's the difference? Can physics reveal that? Is there some understanding of time from physics? It tells us why one is different from the other. Yeah?

Yeah? Exactly what makes it different? Why is the past fixed right? Unchangeable? Unless you believe in crazy science fiction time travel stories, which I don't and the future undetermined? Right, what's the difference? Can physics reveal that? Is there some understanding of time from physics? It tells us why one is different from the other. Yeah?

Why is at an era of time? Like a one way sign in the universe, in the highway of time of the universe.

Why is at an era of time? Like a one way sign in the universe, in the highway of time of the universe.

Yeah, And this is one of those wonderful questions because on the surface of it it seems kind of dumb, like somebody asks you what is time? You're gonna tell them, Oh, it's three o'clock. And if they dig deeper and ask you though, like what is time? Even mean?

Yeah, And this is one of those wonderful questions because on the surface of it it seems kind of dumb, like somebody asks you what is time? You're gonna tell them, Oh, it's three o'clock. And if they dig deeper and ask you though, like what is time? Even mean?

Man? Sometimes I say it's two o'clock. Depending on the circumstances.

Man? Sometimes I say it's two o'clock. Depending on the circumstances.

Oh, I always give the same answer no matter what time. The way people stop asking me. No, my kids always what time is it? And they have like a watch on their hand, there's like two watches on the wall, Like why are you asking me? So I would just say it's three o'clock, no matter what, so that they stop asking.

Oh, I always give the same answer no matter what time. The way people stop asking me. No, my kids always what time is it? And they have like a watch on their hand, there's like two watches on the wall, Like why are you asking me? So I would just say it's three o'clock, no matter what, so that they stop asking.

It sounds like sounds like the same parenting strategy my wife has when we go on road trips, to always ask how long are we do we get there? Is it? Are we there? Yet and she always answers, Nope, it's gonna take twenty more hours.

It sounds like sounds like the same parenting strategy my wife has when we go on road trips, to always ask how long are we do we get there? Is it? Are we there? Yet and she always answers, Nope, it's gonna take twenty more hours.

No matter what. You're like pulling into the place, and she's like, twenty more hours.

No matter what. You're like pulling into the place, and she's like, twenty more hours.

Yeah, no matter what, she always says, twenty hours.

Yeah, no matter what, she always says, twenty hours.

It is a great strategy. You know, me and your wife, we would really get along. It seems like we see eye to eye about how to handle these approaches, how to handle these trouble.

It is a great strategy. You know, me and your wife, we would really get along. It seems like we see eye to eye about how to handle these approaches, how to handle these trouble.

You would have some very sarcastic kids.

You would have some very sarcastic kids.

Bro exactly. Anyway, I love these questions you know that are like, on the surface, so simple, but when you dig deep, they reveal like enormous gaps in our knowledge about the universe. Those questions are the best because those are the opportunities to reveal that the universe is different from the way we understood. Like the way we think about the universe reflects just our experience, the way we've lived and grown up, and not something fundamental, something universal, right, and that's the whole goal of physics.

Bro exactly. Anyway, I love these questions you know that are like, on the surface, so simple, but when you dig deep, they reveal like enormous gaps in our knowledge about the universe. Those questions are the best because those are the opportunities to reveal that the universe is different from the way we understood. Like the way we think about the universe reflects just our experience, the way we've lived and grown up, and not something fundamental, something universal, right, and that's the whole goal of physics.

Yeah, it's one of those questions, like it makes you kind of look almost inwards or look in your like you one day you just wake up and you don't even know where you're standing or how how the house that you live in was built.

Yeah, it's one of those questions, like it makes you kind of look almost inwards or look in your like you one day you just wake up and you don't even know where you're standing or how how the house that you live in was built.

Ohoh, don't lose grasp of reality there, or or hey, we're trying to dig deep. We're not trying to make you go crazy.

Ohoh, don't lose grasp of reality there, or or hey, we're trying to dig deep. We're not trying to make you go crazy.

Doesn't it make you kind of question at like the very nature of the universe?

Doesn't it make you kind of question at like the very nature of the universe?

It does. It's sort of like if you say a word like a hundred times, like say the word marriage a hundred times, it starts to turn into a really weird word. Right, you take it apart, you look at it, you like, that's really strange. It's the same thing with the concept of time, like you know, pick up your hand and rub your fingers together, right, you're feeling that right now, right? But what does now mean? Right now? Sort of like it's always it's infinitely short, and it's slipping constantly into the past. You can never grasp onto it, you can never hold it, right, it's always you're always losing it. It's a really strange concept, the concept of now.

It does. It's sort of like if you say a word like a hundred times, like say the word marriage a hundred times, it starts to turn into a really weird word. Right, you take it apart, you look at it, you like, that's really strange. It's the same thing with the concept of time, like you know, pick up your hand and rub your fingers together, right, you're feeling that right now, right? But what does now mean? Right now? Sort of like it's always it's infinitely short, and it's slipping constantly into the past. You can never grasp onto it, you can never hold it, right, it's always you're always losing it. It's a really strange concept, the concept of now.

Yeah.

Yeah.

Yeah, although I don't know if that's what makes marriage weird, but.

Yeah, although I don't know if that's what makes marriage weird, but.

No, there's lots of things that make marriage weird. Saying that a hundred times is not it. But I remember reading a book about conciousness back when I was really interested in the science of consciousness, which we can talk about another podcast. But the basic idea in that book that's by Daniel Dennett, it's called Consciousness Explained, is that there is no now that you're the consciousness is basically an illusion that all you're ever doing is remembering the immediate past. And I don't know if I believe that, but it really made me think about what now is and how you can never really grasp it. It's always just like sliding away from you and you know, whether it really exists, whether there is a now, right, whether there's a special instant that differentiates between the past and the future.

No, there's lots of things that make marriage weird. Saying that a hundred times is not it. But I remember reading a book about conciousness back when I was really interested in the science of consciousness, which we can talk about another podcast. But the basic idea in that book that's by Daniel Dennett, it's called Consciousness Explained, is that there is no now that you're the consciousness is basically an illusion that all you're ever doing is remembering the immediate past. And I don't know if I believe that, but it really made me think about what now is and how you can never really grasp it. It's always just like sliding away from you and you know, whether it really exists, whether there is a now, right, whether there's a special instant that differentiates between the past and the future.

Right, right, Because sort of technically and physics of time could go both ways, right, like you could. Time is kind of just like an arrow you can flip back and forth in the equations that you guys use, right.

Right, right, Because sort of technically and physics of time could go both ways, right, like you could. Time is kind of just like an arrow you can flip back and forth in the equations that you guys use, right.

Yeah, time is not really very es central to physics. Yeah, I mean, on one hand it is, and on one hand it isn't. Some you could write a lot of physics down without ever thinking about time. On the other hand, time is a central property of physics because we're trying to use physics to predict the future. So this time is both like not part of physics and deeply entwined in it at the same time. So it's an important topic.

Yeah, time is not really very es central to physics. Yeah, I mean, on one hand it is, and on one hand it isn't. Some you could write a lot of physics down without ever thinking about time. On the other hand, time is a central property of physics because we're trying to use physics to predict the future. So this time is both like not part of physics and deeply entwined in it at the same time. So it's an important topic.

Yeah, no, And it's a topic that everybody experiences right at every second of the day, every day of the year, every year of their lives. They're experiencing time, and they're moving forwards in it, and they are they feel it, right, Yeah, they think about it, they think about the future, they remember the past, and so it kind of makes you wonder how many people actually think about or know what time actually is.

Yeah, no, And it's a topic that everybody experiences right at every second of the day, every day of the year, every year of their lives. They're experiencing time, and they're moving forwards in it, and they are they feel it, right, Yeah, they think about it, they think about the future, they remember the past, and so it kind of makes you wonder how many people actually think about or know what time actually is.

Yeah, exactly. So I was wondering do people know why time goes forward? Like, I mean, physicists don't really, but it's always fun to ask general public questions that scientists don't know the answer to, just to see what they come up with. So I walked around the user Irvine campus and I ask people why does time only go forwards?

Yeah, exactly. So I was wondering do people know why time goes forward? Like, I mean, physicists don't really, but it's always fun to ask general public questions that scientists don't know the answer to, just to see what they come up with. So I walked around the user Irvine campus and I ask people why does time only go forwards?

Here's what people had to say.

Here's what people had to say.

Do you know why time only goes forwards?

Do you know why time only goes forwards?

Not really, honestly, I have like some sort of like intuition why it only goes forward, But I don't think we can explain that.

Not really, honestly, I have like some sort of like intuition why it only goes forward, But I don't think we can explain that.

Yeah, okay, cool.

Yeah, okay, cool.

I have no idea.

I have no idea.

No, I don't.

No, I don't.

I guess if I had to go I just say gravity or something.

I guess if I had to go I just say gravity or something.

Okay, No, I don't any idea of best guess, sorry.

Okay, No, I don't any idea of best guess, sorry.

I think time is like the fourth dimensional, right, So actually I don't know about cooky, right, yeah, okay, I'm not sure.

I think time is like the fourth dimensional, right, So actually I don't know about cooky, right, yeah, okay, I'm not sure.

Oh okay.

Oh okay.

Well, when I think of time, I think of it kind of almost as linear progression, meaning that it's a constant in the universe and it's always kind of moving forward, and that's something that we accept as being a fact of the universe, at least as we understand it now. So in that regards, I think that's why we can only see it as moving forwards, because it doesn't kind of make sense to us or it's not even physically possible currently for us to move backwards in time, so we don't consider it in that way.

Well, when I think of time, I think of it kind of almost as linear progression, meaning that it's a constant in the universe and it's always kind of moving forward, and that's something that we accept as being a fact of the universe, at least as we understand it now. So in that regards, I think that's why we can only see it as moving forwards, because it doesn't kind of make sense to us or it's not even physically possible currently for us to move backwards in time, so we don't consider it in that way.

I think it might be a matter of observation. So relative to us, time moves forward in the way that we experience the world just biologically, it's designed to be in a manner that is sort of one dimensional on a forward mind all the time. But in reality, it might be that the fourth dimension of time in space, time might just be a way of describing the universe that the math predicts from physics and myology and perhaps other related science fields.

I think it might be a matter of observation. So relative to us, time moves forward in the way that we experience the world just biologically, it's designed to be in a manner that is sort of one dimensional on a forward mind all the time. But in reality, it might be that the fourth dimension of time in space, time might just be a way of describing the universe that the math predicts from physics and myology and perhaps other related science fields.

Okay, cool, Yeah, so I got a pretty good mix of answers there, right from the standard physics like gravity, which is a you know, that's a good answer. You never know, it might be right.

Okay, cool, Yeah, so I got a pretty good mix of answers there, right from the standard physics like gravity, which is a you know, that's a good answer. You never know, it might be right.

Gravity that somebody actually said gravity.

Gravity that somebody actually said gravity.

Aswer, I don't know gravity.

Aswer, I don't know gravity.

It could be it could be.

It could be it could be.

Yeah, Well, gravity is like the answer to half the questions in physics, the way like pie is the answer to half the questions in math. Right, So if you have no idea, you could just say gravity, and half the time you'll be right.

Yeah, Well, gravity is like the answer to half the questions in physics, the way like pie is the answer to half the questions in math. Right, So if you have no idea, you could just say gravity, and half the time you'll be right.

Not the movie The Force, right, yeah, the fabric of space time itself, that's right, it's gravity.

Not the movie The Force, right, yeah, the fabric of space time itself, that's right, it's gravity.

Yeah. And then you know, some other folks had some more elaborate discussions, but.

Yeah. And then you know, some other folks had some more elaborate discussions, but.

Some people had opinions.

Some people had opinions.

People did have opinions. Yeah, some of them were sort of longer word salad, right, you know, some of them hit on some of the scientific concepts, time being a fourth dimension, et cetera. But yeah, a lot of people want to ask them this question. You could just see in their faces that they had not ever considered this. They're not even a question they had imagined, But as soon as they thought about it, they realized they didn't know and that's my favorite part of this topic is that nobody has really thought about it in terms of general public. But as soon as they do, they're very curious. Right, those are the best questions.

People did have opinions. Yeah, some of them were sort of longer word salad, right, you know, some of them hit on some of the scientific concepts, time being a fourth dimension, et cetera. But yeah, a lot of people want to ask them this question. You could just see in their faces that they had not ever considered this. They're not even a question they had imagined, But as soon as they thought about it, they realized they didn't know and that's my favorite part of this topic is that nobody has really thought about it in terms of general public. But as soon as they do, they're very curious. Right, those are the best questions.

It's amazing how little you actually kind of need to know about the universe to live a full and happy life, you know what I mean, that's a prospective happy life. There's so much you don't need to know.

It's amazing how little you actually kind of need to know about the universe to live a full and happy life, you know what I mean, that's a prospective happy life. There's so much you don't need to know.

Ignorance is bliss, you know, that does have a meaning. People have been living in this universe for hundreds of thousands of years, depending on how you count the beginning of humanity, and there's been a lot of happiness and joy without really any understanding. I mean, I would say people five hundred years ago basically knew nothing about the way the universe actually works. But you know, people had birthday parties and eight cakes and had moments of joy.

Ignorance is bliss, you know, that does have a meaning. People have been living in this universe for hundreds of thousands of years, depending on how you count the beginning of humanity, and there's been a lot of happiness and joy without really any understanding. I mean, I would say people five hundred years ago basically knew nothing about the way the universe actually works. But you know, people had birthday parties and eight cakes and had moments of joy.

So yeah, I mean like a hundred only one hundred years ago, right in the nineteen hundreds, early nineteen hundreds, the people didn't know the concept of atoms or quantum physics, right.

So yeah, I mean like a hundred only one hundred years ago, right in the nineteen hundreds, early nineteen hundreds, the people didn't know the concept of atoms or quantum physics, right.

Yeah, that's about one hundred years old. We didn't know how long the universe had been around, right, So pretty basic stuff about the way the universe works is pretty modern, right, So.

Yeah, that's about one hundred years old. We didn't know how long the universe had been around, right, So pretty basic stuff about the way the universe works is pretty modern, right, So.

We didn't know there were other galaxies?

We didn't know there were other galaxies?

Right, No, they didn't. So what's your point here? Your point is you don't need physics to be happy? Is that what you're trying to say is irrelevant happiness?

Right, No, they didn't. So what's your point here? Your point is you don't need physics to be happy? Is that what you're trying to say is irrelevant happiness?

You think of how much of a richer life you can lead if you know physics.

You think of how much of a richer life you can lead if you know physics.

Okay, I like the way you spun that back, right, using all this technology to talk to me. That's based on physics, not.

Okay, I like the way you spun that back, right, using all this technology to talk to me. That's based on physics, not.

Like money rich, but you know, like spiritually rich.

Like money rich, but you know, like spiritually rich.

Right, right, your career based on technology that was developed with the help of physicists. Where would you.

Right, right, your career based on technology that was developed with the help of physicists. Where would you.

Be is in your science dependent on technology to progress?

Be is in your science dependent on technology to progress?

Exactly? Yes? I am a tiny little mite standing on the shoulders of giants, absolutely, But so are we all? So are we all?

Exactly? Yes? I am a tiny little mite standing on the shoulders of giants, absolutely, But so are we all? So are we all?

Yeah? Well, maybe it's time we got back on topic here, and so let's break it down for people, Daniel, how do physicists see time? Like if you're at a conference and you guys are talking and somebody said, hey, guys, what is time? What do you think people would generally say?

Yeah? Well, maybe it's time we got back on topic here, and so let's break it down for people, Daniel, how do physicists see time? Like if you're at a conference and you guys are talking and somebody said, hey, guys, what is time? What do you think people would generally say?

I think we'd be a lot of disagreements because we don't really have a great description of time. You know one that really makes sense, and you know. The way physics approaches a problem is first you try to build like a model of the problem. You try to describe it in a way that we can grapple using the language that we're familiar with, which is mathematics.

I think we'd be a lot of disagreements because we don't really have a great description of time. You know one that really makes sense, and you know. The way physics approaches a problem is first you try to build like a model of the problem. You try to describe it in a way that we can grapple using the language that we're familiar with, which is mathematics.

You try to find an equation that tells you what's happening.

You try to find an equation that tells you what's happening.

Yeah, exactly, you know something's happening in the real world. Maybe it's like a ball is being thrown in the air, and we try to understand it. So we write down a bunch of equations to describe it, and that lets us build that model in our heads and manipulate it and then use information from the model to describe what's happening in the world. Cool. How do we do that with time? Right? How do we ask this question about like why can I remember the past and not the future? Why does ice melt but not unmelt? Right? These kinds of questions about time, it's pretty hard to wrap your mind around. One approach is to think about the universe in terms of a bunch of snapshots, like you think about a movie. Right, what is a movie? It's not really a continuous experience in time. If you're looking at the screen, you're not really seeing smooth motion. You're seeing a bunch of snapshots.

Yeah, exactly, you know something's happening in the real world. Maybe it's like a ball is being thrown in the air, and we try to understand it. So we write down a bunch of equations to describe it, and that lets us build that model in our heads and manipulate it and then use information from the model to describe what's happening in the world. Cool. How do we do that with time? Right? How do we ask this question about like why can I remember the past and not the future? Why does ice melt but not unmelt? Right? These kinds of questions about time, it's pretty hard to wrap your mind around. One approach is to think about the universe in terms of a bunch of snapshots, like you think about a movie. Right, what is a movie? It's not really a continuous experience in time. If you're looking at the screen, you're not really seeing smooth motion. You're seeing a bunch of snapshots.

You're seeing like a little cells in a film, or like a bunch of screenshots.

You're seeing like a little cells in a film, or like a bunch of screenshots.

Yeah, it's a bunch of screenshots, and they're just packed so tightly together that you don't notice that they're not actually smoothly varying. Right. Your brain does the interpolation for you. It tells you a story. So sometimes we think about the universe that way. We think about like all the universe at this moment, and then all the universe at the next moment, and all the universe at the next moment, like snapshots of the universe.

Yeah, it's a bunch of screenshots, and they're just packed so tightly together that you don't notice that they're not actually smoothly varying. Right. Your brain does the interpolation for you. It tells you a story. So sometimes we think about the universe that way. We think about like all the universe at this moment, and then all the universe at the next moment, and all the universe at the next moment, like snapshots of the universe.

By snapshots, you mean like what is every particle doing and where is it going?

By snapshots, you mean like what is every particle doing and where is it going?

Yeah, exactly and time. Then is a way to sort of order those snapshots is to say this one first, that one next, that one next, and to sort of put them together.

Yeah, exactly and time. Then is a way to sort of order those snapshots is to say this one first, that one next, that one next, and to sort of put them together.

This one can go in front of the other one, yes, or you know what I mean, Like it limits the ordering.

This one can go in front of the other one, yes, or you know what I mean, Like it limits the ordering.

Yeah, And in that sense, physics. The job of physics is to take all the snapshots in the past and predict the ones in the future and to say, okay, according to the laws of physics, the next snapshot will look like this, or if you want to talk quantum mechanically, there's a probability distribution of the next snapshots. These are likely, these are unlikely, these are impots. Right, So physics takes sort of that view of time, and there's a bunch of caveats there, Like, you can't have a snapshot of the whole universe, right because time is not universal. It means different things for different people. You can't know everything about the universe. But you know, you take a small enough model or a single particle or something.

Yeah, And in that sense, physics. The job of physics is to take all the snapshots in the past and predict the ones in the future and to say, okay, according to the laws of physics, the next snapshot will look like this, or if you want to talk quantum mechanically, there's a probability distribution of the next snapshots. These are likely, these are unlikely, these are impots. Right, So physics takes sort of that view of time, and there's a bunch of caveats there, Like, you can't have a snapshot of the whole universe, right because time is not universal. It means different things for different people. You can't know everything about the universe. But you know, you take a small enough model or a single particle or something.

You can also have quantum I mean you also have quantum states, right, Like, isn't that prevent you from getting an exact snapshot of the universe?

You can also have quantum I mean you also have quantum states, right, Like, isn't that prevent you from getting an exact snapshot of the universe?

Yeah, exactly. So you can't really get an exact snapshot, but you could do a quantum mechanical version. You could say, well, what's the quantum state of all the particles or you know, what's the wave function? What's the state of the wave function? Right now that you can talk about and that determines probabilities as.

Yeah, exactly. So you can't really get an exact snapshot, but you could do a quantum mechanical version. You could say, well, what's the quantum state of all the particles or you know, what's the wave function? What's the state of the wave function? Right now that you can talk about and that determines probabilities as.

See, So you're describing kind of how physicists see the universe. They don't see it as they see it as this kind of sequence of snapshots of how things are arranged.

See, So you're describing kind of how physicists see the universe. They don't see it as they see it as this kind of sequence of snapshots of how things are arranged.

Yeah. For example, think about the shortening equation. The shortening equation famous equation describes how a particle's a wave function moves through time, right, and it tells you how it moves. It says, if you have this wave function now and you experience this, then your wave function will be that later. Right. So that's what physics tries to do, or or go back to the mechanical example of a ball going through the air. Right, tells you, well, you shot your ball in this direction. Where's your ball going to be in the future. So that's the role of time in physics, right, to predict the future snapshots.

Yeah. For example, think about the shortening equation. The shortening equation famous equation describes how a particle's a wave function moves through time, right, and it tells you how it moves. It says, if you have this wave function now and you experience this, then your wave function will be that later. Right. So that's what physics tries to do, or or go back to the mechanical example of a ball going through the air. Right, tells you, well, you shot your ball in this direction. Where's your ball going to be in the future. So that's the role of time in physics, right, to predict the future snapshots.

Oh, I see. So to you guys, time is like an input that tells you what the universe is likely to do. Yeah, you know what I mean, Like, do you? It's an input. It's not like an output or something that you can vary or that it is affected by all the other variables.

Oh, I see. So to you guys, time is like an input that tells you what the universe is likely to do. Yeah, you know what I mean, Like, do you? It's an input. It's not like an output or something that you can vary or that it is affected by all the other variables.

Yeah, exactly. And so for example, you want to predict the flight of your ball, it's an input. You can dial that knob and say I want to know where the ball is going to be in one second or five seconds. Or eight point twenty nine seconds or whatever. So it's sort of that knob. The thing we don't the thing that that doesn't explain at all is like why does it only go forwards? And who's controlling how that knob is turning? Or why do we have time at all? Why don't we just have a static universe? That's just sort of like there, you know, it's great, But the first step, of course, is just try to describe it, and then you can build from that and try to answer some of these questions.

Yeah, exactly. And so for example, you want to predict the flight of your ball, it's an input. You can dial that knob and say I want to know where the ball is going to be in one second or five seconds. Or eight point twenty nine seconds or whatever. So it's sort of that knob. The thing we don't the thing that that doesn't explain at all is like why does it only go forwards? And who's controlling how that knob is turning? Or why do we have time at all? Why don't we just have a static universe? That's just sort of like there, you know, it's great, But the first step, of course, is just try to describe it, and then you can build from that and try to answer some of these questions.

What do you mean, like how come we don't have a static universe?

What do you mean, like how come we don't have a static universe?

Like why do we have time at all? Boom right, I don't know, you don't know, nobody knows, Like.

Like why do we have time at all? Boom right, I don't know, you don't know, nobody knows, Like.

Well, I know, there's this idea that time is the fourth dimensions. We have three dimensions up, down, left and right, backwards and forwards, and maybe time is just another direction of the universe, and so we and I think the idea is that we do sort of exist in this state of being still in all for the mensions, but it just so happens that we somehow feel one of the mensions.

Well, I know, there's this idea that time is the fourth dimensions. We have three dimensions up, down, left and right, backwards and forwards, and maybe time is just another direction of the universe, and so we and I think the idea is that we do sort of exist in this state of being still in all for the mensions, but it just so happens that we somehow feel one of the mensions.

Do you know what I mean? Yeah? I love the it just so happens part of that explanation. A right, Okay, here's the hardest part. I'll just YadA, YadA, YadA over that bit.

Do you know what I mean? Yeah? I love the it just so happens part of that explanation. A right, Okay, here's the hardest part. I'll just YadA, YadA, YadA over that bit.

That's my Nobel Prize Nobel Prize winning paper officer.

That's my Nobel Prize Nobel Prize winning paper officer.

It just so happens. I was going ninety miles an hour. You know, I can't explain it. No, you're right. Time is sometimes thought of as the fourth dimension. And so let's dig into that a little bit. What does that mean? Why do we think of it that way? We think of it that way because it's helpful mathematically. Like when Einstein was developing his theory of special relativity, and we talked all about time dilation and stuff like that on a previous episode, he discovered that the equations have a certain symmetry. They look really nice like that. You can write them down really simply and compactly if you include time as the fourth dimension of this larger concept he called space time. So he took three dimensions of space. He tacked on a fourth dimension, which is time, and he constructed this thing called space time. And because your perception of time depends on where you are in space and how fast you are moving through space, the equations get much simpler if you think about all four dimensions in that way. Right, if you think about time parallel to space in that way, And that's a clue when you write down equations and they become simpler if you think about them a certain way. That's a clue from the universe that it's maybe the right way to think about things.

It just so happens. I was going ninety miles an hour. You know, I can't explain it. No, you're right. Time is sometimes thought of as the fourth dimension. And so let's dig into that a little bit. What does that mean? Why do we think of it that way? We think of it that way because it's helpful mathematically. Like when Einstein was developing his theory of special relativity, and we talked all about time dilation and stuff like that on a previous episode, he discovered that the equations have a certain symmetry. They look really nice like that. You can write them down really simply and compactly if you include time as the fourth dimension of this larger concept he called space time. So he took three dimensions of space. He tacked on a fourth dimension, which is time, and he constructed this thing called space time. And because your perception of time depends on where you are in space and how fast you are moving through space, the equations get much simpler if you think about all four dimensions in that way. Right, if you think about time parallel to space in that way, And that's a clue when you write down equations and they become simpler if you think about them a certain way. That's a clue from the universe that it's maybe the right way to think about things.

Okay, so that's that's time is a different dimension. Let's get more into it. Let's go down that rabbit hole. But first, let's take a quick break.

Okay, so that's that's time is a different dimension. Let's get more into it. Let's go down that rabbit hole. But first, let's take a quick break.

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So wait, so the idea that it's a fourth dimension you're saying came from mathematical convenience by Einstein, Do you know what I mean? Like, it's not it was just easier to treat it like a dimension.

So wait, so the idea that it's a fourth dimension you're saying came from mathematical convenience by Einstein, Do you know what I mean? Like, it's not it was just easier to treat it like a dimension.

Yeah, And I wouldn't blow that off mathematical convenience. It's not a small thing, you know. The whole goal of physics, remember, is to like write down an equation of the universe in one line. And so if you can write things more simply, that's a clue that it's probably more correct. It's more and it's like a deeper understanding. So yeah, he discovered that if you write things down with time as sort of the fourth column of your vector, then a lot of the equations are simpler to write down. There's a connection. There's a symmetry there, right, We talked about symmetry in another episode. You can treat time the same way you treat space in many ways. And that's tempting because you think, oh, well that answers question time is just another dimension, right, But it doesn't answer the question because it's not just another dimension, right. You know, time is not space? Right?

Yeah, And I wouldn't blow that off mathematical convenience. It's not a small thing, you know. The whole goal of physics, remember, is to like write down an equation of the universe in one line. And so if you can write things more simply, that's a clue that it's probably more correct. It's more and it's like a deeper understanding. So yeah, he discovered that if you write things down with time as sort of the fourth column of your vector, then a lot of the equations are simpler to write down. There's a connection. There's a symmetry there, right, We talked about symmetry in another episode. You can treat time the same way you treat space in many ways. And that's tempting because you think, oh, well that answers question time is just another dimension, right, But it doesn't answer the question because it's not just another dimension, right. You know, time is not space? Right?

Time? What does it mean time is not space? Well, for exam, time's money. You can move forwards and backwards. In space, right, you can go left, you can go right, you have some control over it. You can't do that with time. But isn't it just sort of a matter of perspective, Like I like in the grand scheme of the history of the universe. You know, I existed for this amount of time, but while I'm living it, I can only go forward. I can only get the experience of moving forward in time.

Time? What does it mean time is not space? Well, for exam, time's money. You can move forwards and backwards. In space, right, you can go left, you can go right, you have some control over it. You can't do that with time. But isn't it just sort of a matter of perspective, Like I like in the grand scheme of the history of the universe. You know, I existed for this amount of time, but while I'm living it, I can only go forward. I can only get the experience of moving forward in time.

Yeah, that's true.

Yeah, that's true.

Technically I sort of existed all throughout my life in space time.

Technically I sort of existed all throughout my life in space time.

You existed all throughout your life, Yeah, but you don't exist all throughout time. Right, There's no limit to where you can visit in space, you can go from here to there to the other places. But in time you can only visit between your birth and your death, and you can only go to each time once. Right, that's not true for space. I imagine there are lots of places you go to many many times, like your refrigerator or your bed. Right, you visit those places many times. So space is quite different from time. Right, there's a.

You existed all throughout your life, Yeah, but you don't exist all throughout time. Right, There's no limit to where you can visit in space, you can go from here to there to the other places. But in time you can only visit between your birth and your death, and you can only go to each time once. Right, that's not true for space. I imagine there are lots of places you go to many many times, like your refrigerator or your bed. Right, you visit those places many times. So space is quite different from time. Right, there's a.

Special loops in space, but it can't do loops in time exactly.

Special loops in space, but it can't do loops in time exactly.

And time time has this special difference right than now. Right, there's no now in space. I mean, I'm here, I'm there, you're over here. But there's no special location in space. But time has this special location, this thing we call now, which exists weirdly and slides forward weirdly. So I was saying earlier, like, why is in the universe static? Why is time move forwards? Why isn't it just stuck a T equals zero? Nothing happens? What's pushing it forward? What's turning the engine of the universe? Right?

And time time has this special difference right than now. Right, there's no now in space. I mean, I'm here, I'm there, you're over here. But there's no special location in space. But time has this special location, this thing we call now, which exists weirdly and slides forward weirdly. So I was saying earlier, like, why is in the universe static? Why is time move forwards? Why isn't it just stuck a T equals zero? Nothing happens? What's pushing it forward? What's turning the engine of the universe? Right?

I guess what I mean is, you know, if time is you can treat it as a fourth dimension. Then you know our experience of the universe is a time is constant, and you them it moves at a steady pace, and that you were only going forwards in it, right, whereas in space you're saying we can go backwards. But what if I just kind of take another dimension and use that as my kind of ticker?

I guess what I mean is, you know, if time is you can treat it as a fourth dimension. Then you know our experience of the universe is a time is constant, and you them it moves at a steady pace, and that you were only going forwards in it, right, whereas in space you're saying we can go backwards. But what if I just kind of take another dimension and use that as my kind of ticker?

Which dimension would you use as your clock?

Which dimension would you use as your clock?

I don't know? Up?

I don't know? Up?

Okay, yeah, so you'd be like, hey, let's have lunch at X equals five meters or something.

Okay, yeah, so you'd be like, hey, let's have lunch at X equals five meters or something.

Yeah, I don't know, or you know, kind of mathematically, what would that mean?

Yeah, I don't know, or you know, kind of mathematically, what would that mean?

The different time and space are not the same. You can't just swap out time for space because you don't have the same freedom and time as you do in space. Right. If space were moved always forward the way time did, like, you could never go back to anywhere. Right, You're like, oh, yeah, hey, I had lunch and now it's sort of sliding slowly away from me. You know, it'd be pretty weird, but it's very natural experience.

The different time and space are not the same. You can't just swap out time for space because you don't have the same freedom and time as you do in space. Right. If space were moved always forward the way time did, like, you could never go back to anywhere. Right, You're like, oh, yeah, hey, I had lunch and now it's sort of sliding slowly away from me. You know, it'd be pretty weird, but it's very natural experience.

Oh, I see, you're more limited in the time dimension exactly.

Oh, I see, you're more limited in the time dimension exactly.

There's some extra rules that seem to apply to the time dimension that don't apply to the other dimensions, and that's weird. And anytime we see symmetries, we're like cool. But then when those symmetries are broken, we're like, Okay, time is like the other dimensions, but it's different. Then we ask why is it different? How's it different? What makes it different? Because that's the clue to solve the the other puzzle.

There's some extra rules that seem to apply to the time dimension that don't apply to the other dimensions, and that's weird. And anytime we see symmetries, we're like cool. But then when those symmetries are broken, we're like, Okay, time is like the other dimensions, but it's different. Then we ask why is it different? How's it different? What makes it different? Because that's the clue to solve the the other puzzle.

Right, Okay, so time is it is sort of a fourth dimension, but there are special rules that apply to it that makes us think that maybe it's not really a fourth dimension. Maybe it's just like a mathematical.

Right, Okay, so time is it is sort of a fourth dimension, but there are special rules that apply to it that makes us think that maybe it's not really a fourth dimension. Maybe it's just like a mathematical.

Good clues, right, yeah, or maybe there's two kinds of dimensions. There are space dimensions and time dimensions, right, yeah, and maybe.

Good clues, right, yeah, or maybe there's two kinds of dimensions. There are space dimensions and time dimensions, right, yeah, and maybe.

There are other minds that.

There are other minds that.

Haven't imagined yet, you know. Oh yeah, that's that's the kind of mind blowing like look at the universe in a different way, discovery that I always hope to make in science, you know, to like crack something open that's so deep that it like nobody gets it but the stoners. Man.

Haven't imagined yet, you know. Oh yeah, that's that's the kind of mind blowing like look at the universe in a different way, discovery that I always hope to make in science, you know, to like crack something open that's so deep that it like nobody gets it but the stoners. Man.

Okay, so what are these rules? The rules are that you can only you can visit two times in your you know, you can't go back in time, you can make loops, and it can only go forward. Are those mainly the main restrictions here with time?

Okay, so what are these rules? The rules are that you can only you can visit two times in your you know, you can't go back in time, you can make loops, and it can only go forward. Are those mainly the main restrictions here with time?

Yeah, exactly, those are the main restrictions. And I think the goal of physics and the goal of our podcast is is to try to understand where that comes from. Like can we look at the laws of physics and say, oh, that comes from this, you know, like the way we can look at the laws of quantum mechanics and from that understand the way hydrogen works or whatever. We want to look at the laws of physics and say do they require this behavior? Is it necessary? What does it come from? And it's the deepest level, right, The problem is when we look at laws of physics, we don't get those kinds of clues.

Yeah, exactly, those are the main restrictions. And I think the goal of physics and the goal of our podcast is is to try to understand where that comes from. Like can we look at the laws of physics and say, oh, that comes from this, you know, like the way we can look at the laws of quantum mechanics and from that understand the way hydrogen works or whatever. We want to look at the laws of physics and say do they require this behavior? Is it necessary? What does it come from? And it's the deepest level, right, The problem is when we look at laws of physics, we don't get those kinds of clues.

When we look at the laws of physics, we don't. So the equations in your model of the universe don't tell you that there should be restrictions some time.

When we look at the laws of physics, we don't. So the equations in your model of the universe don't tell you that there should be restrictions some time.

Yeah, let's go back to those equations about like the ball moving. Right. Imagine you throw a ball in.

Yeah, let's go back to those equations about like the ball moving. Right. Imagine you throw a ball in.

Make equals ma. Right, you're talking about equals.

Make equals ma. Right, you're talking about equals.

Yeah, basic stuff. Right, you throw a ball in the air, it goes up and it comes down. Let's start with the simplest case. There's no air resistance, right, It's path up and its path down are going to be very similar. In fact, if somebody took a video of that and then played it backwards, they couldn't tell whether the video is going forwards or backwards. Right, Physicists analyzing the motion of the ball couldn't tell you whether the video is going forwards or backwards.

Yeah, basic stuff. Right, you throw a ball in the air, it goes up and it comes down. Let's start with the simplest case. There's no air resistance, right, It's path up and its path down are going to be very similar. In fact, if somebody took a video of that and then played it backwards, they couldn't tell whether the video is going forwards or backwards. Right, Physicists analyzing the motion of the ball couldn't tell you whether the video is going forwards or backwards.

So if you fed it a time, like if you gave it time, it would give you the same up. And whether you put negative time or positive time exactly how it breaks down.

So if you fed it a time, like if you gave it time, it would give you the same up. And whether you put negative time or positive time exactly how it breaks down.

Exactly, because the equations work in both directions. Right. The equations have time in them. They tell you how things change with time, but they work the same forwards and backwards. So they don't tell you which way the universe should run. They tell you how the universe changes with time, but they don't say why it has to go forwards or not backwards, why it has to go anywhere at all, or why I can't go forwards and then backwards.

Exactly, because the equations work in both directions. Right. The equations have time in them. They tell you how things change with time, but they work the same forwards and backwards. So they don't tell you which way the universe should run. They tell you how the universe changes with time, but they don't say why it has to go forwards or not backwards, why it has to go anywhere at all, or why I can't go forwards and then backwards.

Right, So, if the equations of the universe really represent the universe, then the universe would is okay with traveling backwards in time.

Right, So, if the equations of the universe really represent the universe, then the universe would is okay with traveling backwards in time.

You're saying exactly.

You're saying exactly.

The equations sort of say like, hey, you want to go backwards and time, Sure, here is what would happen.

The equations sort of say like, hey, you want to go backwards and time, Sure, here is what would happen.

Yeah, exactly. And it's sort of like you were saying earlier. It's like an input, you know. Imagine you're doing some calculation and the calculation is a function of position and time. Right, you want to know how many balls are at this location at this time. Right, you drop a thousand balls into a box and you're wondering, like, how many balls are at this location this time? You can ask that question of any point in space and any point in time. Right. You can take the current configuration and you can evolve it forwards or evolve it backwards. The laws allow for all of that, but for some reason there's a difference in the way it actually works in the real world. Right, things slide forwards in time and we don't know why. But there's no restriction on the space parts, right, The equations are functions of space and time, but there is like extra restriction on the time part of it when it comes to like actually implementing the universe.

Yeah, exactly. And it's sort of like you were saying earlier. It's like an input, you know. Imagine you're doing some calculation and the calculation is a function of position and time. Right, you want to know how many balls are at this location at this time. Right, you drop a thousand balls into a box and you're wondering, like, how many balls are at this location this time? You can ask that question of any point in space and any point in time. Right. You can take the current configuration and you can evolve it forwards or evolve it backwards. The laws allow for all of that, but for some reason there's a difference in the way it actually works in the real world. Right, things slide forwards in time and we don't know why. But there's no restriction on the space parts, right, The equations are functions of space and time, but there is like extra restriction on the time part of it when it comes to like actually implementing the universe.

Right, kind of like we have the now, and if all we have was now, the equations would let us tell what happened before in negative time, and we would let us tell us what happens forwards in time, right exactly, the equations wouldn't. Yeah, but but someho our experience. We only have experience of the stuff that happened in negative time.

Right, kind of like we have the now, and if all we have was now, the equations would let us tell what happened before in negative time, and we would let us tell us what happens forwards in time, right exactly, the equations wouldn't. Yeah, but but someho our experience. We only have experience of the stuff that happened in negative time.

That's right. We only remember the past, right, that's the weird part. Right. The past we can remember, we have access to it. It affects us. The future we can't. And most of the laws of physics is an asterisk there. Most of the laws of physics are totally symmetric.

That's right. We only remember the past, right, that's the weird part. Right. The past we can remember, we have access to it. It affects us. The future we can't. And most of the laws of physics is an asterisk there. Most of the laws of physics are totally symmetric.

Right.

Right.

They don't care whether the universe is going forwards or backwards. They're happy to do either one. Wow.

They don't care whether the universe is going forwards or backwards. They're happy to do either one. Wow.

So that's the mystery is the time would be sort of a fourth dimension, but there are some rules, but they those rules are sort of not in the equations of the universe.

So that's the mystery is the time would be sort of a fourth dimension, but there are some rules, but they those rules are sort of not in the equations of the universe.

Yeah, it's weird.

Yeah, it's weird.

That's the game with an asterisk, you're saying exception.

That's the game with an asterisk, you're saying exception.

Right, Yeah, So the game is figure out if the laws of physics that we know of, that we've discovered, that we've written down, if those require things to move forwards, and if so, you know, does that give us a clue as to why it's happening, or maybe there are other laws of physics out there that are much more sensitives to time, that are the ones making time go forward.

Right, Yeah, So the game is figure out if the laws of physics that we know of, that we've discovered, that we've written down, if those require things to move forwards, and if so, you know, does that give us a clue as to why it's happening, or maybe there are other laws of physics out there that are much more sensitives to time, that are the ones making time go forward.

What do you mean, Like, so you're looking for something in the equations that would require time to only move forwards? What does that mean? Like if you put negative time, it should break.

What do you mean, Like, so you're looking for something in the equations that would require time to only move forwards? What does that mean? Like if you put negative time, it should break.

Or yeah, exactly, Like let's think about that. Are there is there anything in physics that does require time to move forward? So let's go back to that ball example. Right, I said, if you throw a ball in the air, you can't tell whether the video of that ball in the air goes forwards or backwards. And when we did that, I said, ignore air resistance. And that's for an important reason, right, because air resistance changes the flight of the ball, right, It slows it down, so that in reality, if you throw a ball in the air, right, it's going to slow down. And so you can tell the difference between going forwards and going backwards, right.

Or yeah, exactly, Like let's think about that. Are there is there anything in physics that does require time to move forward? So let's go back to that ball example. Right, I said, if you throw a ball in the air, you can't tell whether the video of that ball in the air goes forwards or backwards. And when we did that, I said, ignore air resistance. And that's for an important reason, right, because air resistance changes the flight of the ball, right, It slows it down, so that in reality, if you throw a ball in the air, right, it's going to slow down. And so you can tell the difference between going forwards and going backwards, right.

Because there's a there's like you lose some heat or you lose some energy in reality.

Because there's a there's like you lose some heat or you lose some energy in reality.

Right. Yeah, it's probably simpler to think about, like dropping a ball. You know, if you drop a ball and there's no friction, it's going to come all the way up to where you dropped it from. If you drop a ball and it is air resistance, it's going to lose some energy to bumping against all the air molecules. Right, It's not going to come up quite as high as you dropped it. We just keep letting it bounce. Eventually it's going to dribble down and stop right, right.

Right. Yeah, it's probably simpler to think about, like dropping a ball. You know, if you drop a ball and there's no friction, it's going to come all the way up to where you dropped it from. If you drop a ball and it is air resistance, it's going to lose some energy to bumping against all the air molecules. Right, It's not going to come up quite as high as you dropped it. We just keep letting it bounce. Eventually it's going to dribble down and stop right, right.

And that one, that one, if you played it backwards, you would be able to tell the.

And that one, that one, if you played it backwards, you would be able to tell the.

Difference exactly that one if you play it backwards. And that's the case for most things. Right. So where does that come from? Well, that comes from entropy, right, that comes from heat. The heat is really there is the key. It turns out that the universe likes to go from organized to disorganized, right, and that's this concept we call entropy.

Difference exactly that one if you play it backwards. And that's the case for most things. Right. So where does that come from? Well, that comes from entropy, right, that comes from heat. The heat is really there is the key. It turns out that the universe likes to go from organized to disorganized, right, and that's this concept we call entropy.

Yeah, I've heard of this before. But before we dive in, let's take a short break.

Yeah, I've heard of this before. But before we dive in, let's take a short break.

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