Jul 29, 2024 02:56 AM
https://youtu.be/AZsmyTE3j9o
VIDEO EXCERPTS: [...] No one says like, "Oh my God, what are you talking about with these esoteric concepts about 7 p.m.?"
We all know what to do operationally. Time, in some sense, is just a label on different events in the Universe.
So what time is, I don't think is the problem. The issue -- the real puzzles -- come about when we talk about the properties that time has.
We have a past, we have a present, we have a future. How are they different? Are we moving through it?
We have memories of the past, but we have no memories of the future. Why is that? Where does that asymmetry come from?
[...] One of the most noticeable features of time is that it has a direction, right? That there's a difference between the past and future. Sometimes we think about this as just an intrinsic feature of reality.
Like the past already happened, it's in the books -- the future is up for grabs. It hasn't happened yet, and the present is where we live.
But then, along comes physics. And what people notice about our best theories of physics is that those theories do not distinguish between the past and the future.
But in our everyday lives, nothing is more obvious.
It really requires a bit of mental discipline to say, "Well, time could exist without an arrow."
And one way of thinking about that is there is no intrinsic arrow of space, but there's still space, okay?
[...] There's no special direction in space. And how you perceive that is imagine you're an astronaut: you're flying around in your little spacesuit.
There wouldn't be any difference between any direction you could look. There's no experiment you could do in physics that would point out a direction in the universe, but space still exists.
Likewise, time would still exist even if there wasn't an arrow.
But here on Earth, we do have an arrow of space. If I pick up a coffee cup and let it go, it will always fall down. There's clearly a distinction between up and down.
No one is tempted to think that's a fundamental feature of the Universe. It's not because downness is embedded in the laws of physics. It's because we live in the vicinity of an influential object: the Earth.
The arrow of time is exactly the same way.
We in our everyday lives, perceive an arrow of time because we live in the aftermath of an influential event: the Big Bang.
And that gets us into a realm of the concept of 'entropy.'
[...] Why was the world lower entropy yesterday than it is today? The explanation is not completely satisfying, to be honest.
The explanation is the following: because it was even lower entropy the day before yesterday.
[...] And this chain of reasoning goes back 14 billion years to the Big Bang, to the origin of our observable universe...
[...] There's a way of talking about human life and entropy, which I think is misguided, which is that we should think about life ... as a fight against increasing entropy.
I think that's wrong. I think that we owe life to the fact that entropy is increasing, because what would it mean if entropy were not increasing?
It would mean that nothing is happening. Nothing interesting is taking place.
[...] You'd just be in what we call 'thermal equilibrium.' Everything would be the same everywhere. It would be the maximally boring universe.
[...] Think about a famous example there: The perfume is all in little bottle.
It's in a big room. You open it, and it all floats through the room. The entropy of the perfume increases.
But if you think about it, when the perfume is all in the bottle, it's very simple.
Once it's all spread through the room, it's also very simple.
It went from low entropy to high entropy, but it went from simple to simple.
It's the journey from the simple, low-entropy starting point to the simple, high-entropy ending point, that there's a large space of possibilities where things can be intricate.
It's in between that things like us -- complicated, intricate systems that feed off of the increasing entropy of the Universe -- can and do come into existence.
How the Big Bang gave us time, explained by theoretical physicist Sean Carroll
https://www.youtube-nocookie.com/embed/AZsmyTE3j9o
VIDEO EXCERPTS: [...] No one says like, "Oh my God, what are you talking about with these esoteric concepts about 7 p.m.?"
We all know what to do operationally. Time, in some sense, is just a label on different events in the Universe.
So what time is, I don't think is the problem. The issue -- the real puzzles -- come about when we talk about the properties that time has.
We have a past, we have a present, we have a future. How are they different? Are we moving through it?
We have memories of the past, but we have no memories of the future. Why is that? Where does that asymmetry come from?
[...] One of the most noticeable features of time is that it has a direction, right? That there's a difference between the past and future. Sometimes we think about this as just an intrinsic feature of reality.
Like the past already happened, it's in the books -- the future is up for grabs. It hasn't happened yet, and the present is where we live.
But then, along comes physics. And what people notice about our best theories of physics is that those theories do not distinguish between the past and the future.
But in our everyday lives, nothing is more obvious.
It really requires a bit of mental discipline to say, "Well, time could exist without an arrow."
And one way of thinking about that is there is no intrinsic arrow of space, but there's still space, okay?
[...] There's no special direction in space. And how you perceive that is imagine you're an astronaut: you're flying around in your little spacesuit.
There wouldn't be any difference between any direction you could look. There's no experiment you could do in physics that would point out a direction in the universe, but space still exists.
Likewise, time would still exist even if there wasn't an arrow.
But here on Earth, we do have an arrow of space. If I pick up a coffee cup and let it go, it will always fall down. There's clearly a distinction between up and down.
No one is tempted to think that's a fundamental feature of the Universe. It's not because downness is embedded in the laws of physics. It's because we live in the vicinity of an influential object: the Earth.
The arrow of time is exactly the same way.
We in our everyday lives, perceive an arrow of time because we live in the aftermath of an influential event: the Big Bang.
And that gets us into a realm of the concept of 'entropy.'
[...] Why was the world lower entropy yesterday than it is today? The explanation is not completely satisfying, to be honest.
The explanation is the following: because it was even lower entropy the day before yesterday.
[...] And this chain of reasoning goes back 14 billion years to the Big Bang, to the origin of our observable universe...
[...] There's a way of talking about human life and entropy, which I think is misguided, which is that we should think about life ... as a fight against increasing entropy.
I think that's wrong. I think that we owe life to the fact that entropy is increasing, because what would it mean if entropy were not increasing?
It would mean that nothing is happening. Nothing interesting is taking place.
[...] You'd just be in what we call 'thermal equilibrium.' Everything would be the same everywhere. It would be the maximally boring universe.
[...] Think about a famous example there: The perfume is all in little bottle.
It's in a big room. You open it, and it all floats through the room. The entropy of the perfume increases.
But if you think about it, when the perfume is all in the bottle, it's very simple.
Once it's all spread through the room, it's also very simple.
It went from low entropy to high entropy, but it went from simple to simple.
It's the journey from the simple, low-entropy starting point to the simple, high-entropy ending point, that there's a large space of possibilities where things can be intricate.
It's in between that things like us -- complicated, intricate systems that feed off of the increasing entropy of the Universe -- can and do come into existence.
How the Big Bang gave us time, explained by theoretical physicist Sean Carroll