The mind-bending physics of time | Sean Carroll

Summary

Die Zeit ist ein Rätsel der Physik. Obwohl die Zeit eine Richtung hat, unterscheiden die Grundgesetze der Physik nicht zwischen Vergangenheit und Zukunft. Die Zeit hat eine Richtung wegen des Einflusses des Urknalls. Die Entropie des Universums nimmt stetig zu. Komplexe Strukturen wie Lebewesen können nur in einer Welt mit wachsender Entropie existieren. Das Universum war am Anfang einfach und geordnet, und wird in der Zukunft wieder so sein. Dazwischen entstehen komplizierte Strukturen.

Takeaways

• 😀 Zeit ist einfach ein Label für verschiedene Ereignisse im Universum.
• 😯 Es gibt viele rätselhafte Eigenschaften der Zeit, wie die Asymmetrie zwischen Vergangenheit und Zukunft.
• 🤔 Die fundamentale Physik unterscheidet nicht zwischen Vergangenheit und Zukunft.
• 😮 Der Pfeil der Zeit kommt vom Einfluss des Urknalls.
• 😃 Entropie misst die Unordnung eines Systems.
• 🧐 Entropie nimmt im Universum natürlicherweise zu.
• 🤨 Das Universum startete in einem sehr geordneten, niedrig-entropischen Zustand.
• 😕 Komplexität braucht steigende Entropie, um zu existieren.
• 🙂 Wir verdanken das Leben der Tatsache, dass die Entropie zunimmt.
• 🤔 Warum komplexe Strukturen wie Leben entstanden sind, ist noch ein Rätsel.

Outlines

00:00

🤔 Zeit ist nur ein Etikett für Ereignisse im Universum

In diesem Absatz geht es darum, dass das Wort „Zeit“ nur ein Label ist, das wir verwenden, um verschiedene Ereignisse im Universum voneinander zu unterscheiden. Der Begriff „Zeit“ an sich ist nicht das Problem, sondern die rätselhaften Eigenschaften, die wir der Zeit zuschreiben, wie Vergangenheit, Gegenwart und Zukunft. Es wird die Asymmetrie zwischen Vergangenheit und Zukunft diskutiert und infrage gestellt, ob Zeit eine Richtung hat.

05:02

😡 Komplexe Strukturen verdanken ihr Entstehen der Entropie

Dieser Absatz behandelt das Konzept der Entropie und argumentiert, dass die Zunahme der Entropie im Universum notwendig war, damit komplexe Strukturen wie Leben entstehen konnten. Allerdings bedeutet das nicht, dass Leben ein Kampf gegen die Entropie ist. Vielmehr nutzen komplizierte Systeme die zunehmende Unordnung, um Ordnung auf einer lokalen Ebene zu erschaffen. Es bleibt die wissenschaftliche Frage offen, wie genau komplexe Strukturen unter Ausnutzung steigender Entropie entstanden sind.

Keywords

💡Zeit

Zeit ist ein zentrales Thema des Videos. Der Sprecher diskutiert die Natur der Zeit und ihre Eigenschaften. Er stellt fest, dass Zeit ein hilfreiches Konzept ist, um zwischen verschiedenen Momenten zu unterscheiden, aber die eigentlichen Rätsel liegen in den Eigenschaften der Zeit wie Vergangenheit, Gegenwart und Zukunft. Der Sprecher hinterfragt, ob wir uns tatsächlich durch die Zeit bewegen und ob wir in die Vergangenheit reisen können.

💡Entropie

Entropie beschreibt den Grad der Unordnung oder des Durcheinanders in einem System. Der Sprecher erklärt, dass die Entropie im Universum die Tendenz hat, von niedrig zu hoch zu steigen. Die niedrige Entropie des Universums kurz nach dem Urknall ist der Grund, warum wir eine gerichtete Zeit oder einen Zeitpfeil wahrnehmen.

💡Vergangenheit

Die Vergangenheit ist einer der Aspekte der Zeit, die der Sprecher diskutiert. Er stellt fest, dass wir zwar Erinnerungen an die Vergangenheit haben, aber keine Erinnerungen an die Zukunft. Der Sprecher hinterfragt, warum es diese Asymmetrie zwischen Vergangenheit und Zukunft gibt.

💡Gegenwart

Die Gegenwart ist ebenfalls ein Aspekt der Zeit, den der Sprecher diskutiert. Er sagt, die Gegenwart sei der Ort, an dem wir leben - zwischen Vergangenheit und Zukunft. Die Eigenschaften der Gegenwart im Vergleich zu Vergangenheit und Zukunft sind Teil des Rätsels der Zeit.

💡Zukunft

Die Zukunft ist der dritte Aspekt der Zeit, den der Sprecher untersucht. Im Gegensatz zur Vergangenheit haben wir laut Sprecher keine Erinnerung an die Zukunft. Er fragt, warum wir glauben, die Zukunft beeinflussen zu können, aber nicht die Vergangenheit. Dies ist Teil der Asymmetrie, die er hinterfragt.

💡Urknall

Der Urknall markiert den Beginn unseres beobachtbaren Universums. Laut Sprecher begann die Entropie des Universums nach dem Urknall extrem niedrig und steigt seitdem. Der Urknall ist daher der Ausgangspunkt für den Zeitpfeil, den wir wahrnehmen.

💡Naturgesetze

Der Sprecher erwähnt, dass unsere besten physikalischen Theorien keinen Unterschied zwischen Vergangenheit und Zukunft machen. Die Richtung der Zeit ist nicht in den Naturgesetzen verankert. Dies wirft für ihn die Frage auf, woher die Asymmetrie zwischen Vergangenheit und Zukunft kommt.

💡Komplexität

Der Sprecher diskutiert, wie trotz steigender Entropie komplexe Strukturen wie Lebewesen entstehen konnten. Dies bleibt ein Rätsel, das weiterer Forschung bedarf. Ohne Entropiezunahme gäbe es jedoch keine Komplexität.

💡Leben

Der Sprecher argumentiert, dass Leben der Entropiezunahme im Universum zu verdanken ist. Ohne Entropiezunahme gäbe es keine Vergangenheit, keine Zukunft und keine Komplexität. Leben speist sich gewissermaßen von der Entropiezunahme.

💡Information

Der Sprecher sieht die Rolle von Information als einen wichtigen Faktor, um zu verstehen, wie komplexe Strukturen entstehen konnten. Die Chemie und Geologie spielen ebenfalls eine Rolle, aber Informationen sind ein Schlüsselkonzept, das weitere Forschung erfordert.

Highlights

Time is just a label on different events in the Universe.

The real puzzles come about when we talk about the properties that time has, like past, present and future.

At the level of fundamental laws of physics, there is no intrinsic arrow of time.

We perceive an arrow of time because we live in the aftermath of the influential Big Bang event.

Entropy is a measure of how disorganized a system is. The universe tends to go from low to high entropy.

The low entropy in the past explains the arrow of time, not fundamental physics.

Without increasing entropy, there would be no memory, no causal effects, just a maximally boring universe.

Complex structures like life require increasing entropy, but their existence remains scientifically puzzling.

In between low and high entropy states, intricate systems like life can come into existence.

If entropy weren't increasing, none of the complexity of our universe would have come to pass.

Our universe started simple and low entropy. In the future, it will be simple but high entropy.

It's the journey from low to high entropy where complexity can arise.

We don't fully understand why complex structures like life came into existence.

Information and chemistry may help explain the emergence of complexity.

Increasing entropy enables, but does not necessarily cause, the intricacy we see.

Transcripts

- Lexicographers will tell you that time,

the word, "T-I-M-E,"

is the most used noun in the English language.

We can't get through the day

without talking about time all the time.

I think about how we use time,

when we actually talk about it.

If you say, "Meet me at 7 p.m.,"

no one panics.

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.

The Universe happens over and over again

at different things we call moments,

and time helps us tell the difference

between one moment and another.

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?

Why are we all born young?

Why do we all inevitably age?

Why do we think

that we can affect the future but not the past?

Could we possibly travel back into it?

Anyway, there's a lot of questions about the nature

of time that are really confusing

and many of them we don't know the answer to,

but what time is,

I don't think it's one of them.

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?

We live in a three-dimensional world-

up, down, left, right, forward, backward-

at the level of the fundamental laws of physics,

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.'

Entropy is how messy, how disorganized,

how random a system is.

When things are nice and neat and tidy,

they are low entropy.

When they're all messy

and all over the place, they're high entropy.

And there's a natural tendency of things

in the Universe to go from low entropy to high entropy.

This is called the 'second law of thermodynamics.'

The real question is:

Why was the world ever low

entropy to begin with?

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 why was the Universe even lower entropy the day

before yesterday?

Because it was even lower entropy the day before that.

And this chain of reasoning goes back 14 billion years

to the Big Bang, to the origin of our observable universe;

in a hot, dense state, a very low-entropy state,

and the Universe has been increasing in entropy ever since.

And this is called the 'Past hypothesis' by philosophers-

David Albert, who's a philosopher of physics,

gave it this name.

So now we say, "If you know that the world is made of atoms,

and you know what entropy is,

in terms of rearranging all those atoms,

and you know the past hypothesis-

that the entropy of the universe started really low-

then you can explain everything that happened after that.

There's a way of talking

about human life and entropy, which I think is misguided,

which is that we should think about life.

You know, literally living, being a biological organism,

taking in food and everything,

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.

Without entropy increasing,

there's no memory of the past.

Without entropy increasing,

there's no causal effect that we have on the future.

You'd just be in what we call 'thermal equilibrium.'

Everything would be the same everywhere.

It would be the maximally boring universe.

But what we do have as a scientific question is:

'Why do complicated complex structures come

into existence at all?'

It's clear that they need increasing entropy to exist,

because if entropy were already maxed out,

there would be no complexity.

But that doesn't mean they have to come

come into existence.

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.

There's more perfume here over there.

There can be swirls caused by the motion

of the wind in the room and so forth.

The Universe is just like that.

Our Universe started out simple and low entropy.

In the future, the stars will die,

the black holes will evaporate.

It'll be dark, empty, and again, simple, but high entropy.

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.

We don't know the whole story there.

I think it's a very fun, active, scientific research area:

Why did complex structures like living beings come

into existence and exactly the way we did?

What is the role of information?

What is the down-to-Earth chemistry that is going on here?

What is the geology that is going on here?

Could it happen on other planets?

Very interesting questions- but one thing I do know

is that if entropy weren't increasing along the way,

none of it would've come to pass.