And so I thought well, okay, go ahead And he said a shaman told me that my grandmother is still alive because of quantum mechanics Is this right?

シャーマンが、祖母がまだ生きているのは量子力学のおかげだと言ったんだ。

I had to pause for a moment and try to understand and after thinking about this for a while I came to the conclusion.

私は少し立ち止まって理解しようとし、しばらく考えた末に結論に達した。

It's not entirely wrong But the thing is it's got nothing to do with quantum mechanics.

完全に間違っているわけではないが、量子力学とは関係ないということだ。

It's actually got something to do with Einstein's theory of special relativity It's all about the reality of time It's all about the question whether the present moment this now which we experience ourselves Whether this is of fundamental importance There are a lot of things like those big existential questions about afterlife that physics can actually tell us something about My name is Sabine Hossenfelder I'm a physicist and research fellow at the Frankfurt Institute for Advanced Studies And I have a book that's called existential physics a scientist's guide to life's biggest questions Before Einstein, time was this universal parameter We all shared the same moment of time the same moment of now that we could all agree on But then Einstein came and he said well, it's not that simple And the major reason for this is that the speed of light is finite And nothing can go faster than the speed of light It's the same for all observers and This sounds like a really innocent assumption, but it has a truly Fundamental consequence which is fairly easy to understand actually if you ask yourself Whether you know if the screen in front of you is actually there right now Naively would say yes, of course.

それはアインシュタインの特殊相対性理論と関係がある。時間の現実についてである、しかし、アインシュタインが登場し、彼は言った。「そう単純ではない」と。その大きな理由は、光速は有限であり、光速より速く進むものはない。

It's there I mean, I'm holding it my hand or I see it directly in front of me But we just learned that the speed of light is finite and nothing can go faster than the speed of light So everything that you experience everything that you see You see it as it was a tiny little amount of time in the past So, how do you know that anything exists right now?

でも、光速は有限で、光速より速く進むものはない。

What do you even mean by now?

今さら何を言っているんだ？

so this is the problem that comes up in Einstein's theory of special relativity and Einstein tried to construct A notion of now in this new theory and he failed So imagine you're looking straight ahead and there's a train going through to your line of sight say from the left to the right And on the train, there's your friend.

アインシュタインはこの新しい理論で「今」という概念を構築しようとしたが、失敗した。つまり、あなたがまっすぐ前を見ていて、あなたの視線の先に列車が走っているとしよう。

So let's call her Alice Now, let's also imagine that at the exact moment that Alice who's standing in the middle of the train is looking straight at you There are light flashes going off on both ends of the train And the question is did these light flashes happen at the same time?

では、彼女をアリスと呼ぶことにしよう。さて、列車の真ん中に立っているアリスが、あなたをまっすぐ見ているその瞬間に、列車の両端で閃光が走ったとしよう。

Now if you want to answer this question looking at the train, that's pretty straightforward There are those light flashes going off.

もし、この質問に電車を見て答えたいのなら、それはとても簡単なことだ。

They both come from sources that are the same distance from you So, of course you see them at the same time But how does the same thing look from Alice's perspective?

このふたつは同じ距離の光源から来ている。

The light flashes go off, but while the light travels towards her She's moving towards one of the light sources and away from the other So the one path of the light is shorter and the other one is longer So from Alice's perspective the light flash from the front of the train arrives earlier than the one from the back So she would say no, they did not happen at the same time And now the important point is that this is relativity Neither of them is right and neither of them is wrong.

光の点滅は消えるが、光が彼女に向かって移動する間、彼女は光源の一方に近づき、もう一方から遠ざかっている。

They both have an equally valid perspective And what do we conclude from this?

そして、ここから何を結論づけるのか？

Well, we conclude from this that there is no Unambiguous notion to define what happens now.

さて、ここから結論づけられるのは、今何が起きているのかを定義する明確な概念はないということだ。

It depends on the observer So they're both right and If you follow this logic to its conclusion Then the outcome is that every moment could be now for someone and that includes all moments in your past and It also includes all moments in your future So this impossibility to define one notion of now that we all agree on is called the relativity of simultaneity and it's super important because it tells us that fundamentally this Experience of now that we all share is meaningless So the mathematical framework that Einstein came up with to make sense of this absence of now and the finiteness of the speed of light and the relativity of Simultaneity is that he combined space with time to one common entity which is called space-time and More specifically because the present moment has no fundamental significance this entire space-time Exists in the present moment and it's become known as the block universe In the block universe the past the present and the future exist in the same way There's just no way that you can single out one particular time as special So the past in which your grandma is still alive exists the same way as this present moment Now there's another way to look at this idea that people who have sadly deceased Do in some sense still exist and it's because of the way that all the fundamental laws of nature that we know work They don't destroy information.

この論理を結論まで導くと、すべての瞬間が誰かにとっての「今」である可能性があり、それはあなたの過去のすべての瞬間を含み、あなたの未来のすべての瞬間も含むということになる。アインシュタインがこの「今」の不在と光速の有限性、そして同時性の相対性を理解するために考え出した数学的枠組みは、空間と時間を組み合わせて、空間と時間と呼ばれる共通の存在にするというものだった。より具体的には、今という瞬間には根本的な意味がないため、この空間全体が今という瞬間に存在し、この空間全体が今という瞬間に存在するのである。ブロック宇

The only thing that they do is that they Rearrange the matter and radiation and everything that's in the universe They just give you the rules for how to put them in different places with different velocities but you can apply those rules forward and backward and this means if you had a really really good computer you can in principle always Find out what happened earlier.

ただ、物質や放射線、宇宙に存在するすべてのものを並べ替えるだけなんだ。異なる場所に異なる速度で配置するためのルールを与えるだけで、そのルールを前にも後ろにも適用することができる。

So in this sense information cannot get destroyed it can however become for practical purposes impossible to retrieve.

この意味で、情報が破壊されることはない。

There are two cases that Physicists have considered where information might get destroyed that have so far not been resolved One of them is information that falls into a black hole we don't actually know what happens with it and the other one is the Mysterious measurement process in quantum mechanics, which is also an unresolved problem So if someone you knew dies then of course we all know that you can no longer communicate with this person and that's because the information that made up their personality it disperses into very subtle correlations in the remains of their body which become entangled with all the particles around them and slowly slowly they spread into Radiation that disperses throughout the solar system and eventually throughout the entire universe But this is a very anthropomorphic thing.

物理学者が考えた、情報が破壊される可能性のあるケースで、今のところ解決されていないものが2つある。1つはブラックホールに落ちた情報で、実際にどうなるかはわかっていない、もしあなたが知っている誰かが死んだとしたら、その人ともうコミュニケーションがとれないことは、もちろん誰もが知っている。

It's very tied to our own existence and Who knows what's going to happen in a billion years or something to the nature of humans?

それは私たち自身の存在と非常に結びついているし、10億年後とかに人間の本質に何が起こるかなんて誰にもわからない。

Maybe there'll be some cosmic consciousnesses, which will also be spread out and this information will become accessible again So, I know it sounds crazy but for all we know about the fundamental laws of nature about Einstein's theories and about the way that our Current theories work.

だから、おかしな話だと思うだろうけど、アインシュタインの理論や現在の理論が機能する方法について、私たちは自然の基本法則について知っているんだ。

It seems that our existence actually transcends the passage of time there is something timeless about the information that makes up us and everything else in the universe and I think that's a really deep spiritual insight that we get directly from studying the foundations of physics and I have to admit that I Personally find it really hard to make intuitive sense of it It's one way to look at the maths and say okay.

物理学の基礎を学ぶことで、直接的に得られる精神的な洞察は本当に深いものだと思う。

This is how it works These are the conclusions that we draw from our observations and the mathematics describes it correctly It's another thing entirely to make sense of this in your everyday life But as a physicist, I trust the process of knowledge discovery that comes from using the scientific method And so I take this seriously Get smarter faster with videos from the world's biggest thinkers and To learn even more from the world's biggest thinkers get big think plus for your business

しかし、物理学者として、私は科学的手法から生まれる知識発見のプロセスを信頼している。