Name: 我們穿越回了過去，結果物理學家們超生氣！🤯 (We Traveled Back in Time. Now Physicists Are Angry.)
Uploaded: 2026-01-15T17:01:20.000Z
Duration: 11 min 20 s

Congratulations, you're a time traveller.

恭喜你，你就是個時間旅行者。

A bit lame, but let's start here to get to the fun real time travel.

雖然有點遜，但我們先從這裡開始，接著進入好玩的時間旅行。

To ride on dinosaurs and high five, Einstein.

要騎在恐龍身上，跟愛因斯坦擊掌。

Time isn't really a thing that passes, but a dimension, a direction you can move in.

時間其實不是一個會流逝的東西，而是一個維度，一個你可以移動的方向。

We think our universe is four dimensional, with three spatial and one time dimensions smooshed together into a fancy thing we call space time.

我們認為我們的宇宙是四維的，有三個空間維度和一個時間維度，它們被壓縮成一個我們稱為時空的美妙東西。

What you experience as time passing and your life happening is actually you moving through the time dimension.

你所體驗到的時間流逝和你的人生經歷，其實是你正在穿越時間維度。

While you can go forward, backward, left and right, up and down in the space dimensions, in time, you can only go forward.

雖然你可以在空間維度裡前後左右上下移動，但在時間裡，你只能往前走。

You have far more control over how you move through time.

你對如何在時間中移動，其實有更多控制權。

To explain how this actually works, without making a maths video, we have to make a lot of physicists grumpy.

為瞭解釋這實際上是怎麼運作的，而且不拍數學影片，我們得惹毛很多物理學家。

So please keep in mind that we're still simplifying and lying a bit.

所以請記住，我們還是在簡化和稍微唬爛一下。

好的，所以有一個非常奇怪的規則。

Everything in our universe moves at the speed of light through four dimensional space time.

我們宇宙中的一切，都在四維時空中以光速移動。

Your speed through space time is the sum of your separate speeds through time and space.

你在時空中移動的速度，是你分別在時間和空間中移動速度的總和。

Even if you're not moving through space dimensions, you're moving through the time dimension, blasting face first into the future.

就算你沒有在空間維度移動，你還是在時間維度移動，直衝未來。

You can slow down in the time dimension by moving faster through the space dimensions.

你可以在空間維度移動得更快，來減慢你在時間維度的速度。

But in total, you will always move at the speed of light through space time.

但總體來說，你移動的時空速度永遠是光速。

If you could somehow truly stand still in space, you'd still move through time at the speed of light.

如果你真的能在空間中靜止不動，你仍然會以光速穿越時間。

And the other way round, photons, light particles, move at the speed of light through space.

反過來說，光子，也就是光粒子，是以光速在空間中移動。

They don't experience any time passing because their speed in that time dimension is zero.

牠們不會感受到時間流逝，因為牠們在時間維度的速度是零。

In the time dimension, they're frozen in place.

在時間維度裡，牠們是被凍結在原地的。

If you see light on earth from the photon's perspective, it was just on the surface of the sun and then suddenly crashed into your eye with nothing happening in between.

如果你從光子的視角看地球上的光，牠其實剛從太陽表面出發，然後突然就進入你的眼睛，中間什麼事都沒發生。

Remember, we're telling a science story here.

記住，我們在這裡講一個科學故事。

In real life, things are more complicated.

For one, it's impossible to truly stand still relative to space itself.

首先，你不可能真正地相對於空間本身靜止不動。

You can only be standing still relative to other things in space.

你只能相對於空間中的其他物體靜止。

And you can't really define a reference frame for photons as we just did.

而且我們就像剛剛那樣，無法真正為光子定義一個參考系。

想知道更多細節，可以看看我們的參考資料。

Ok, so everything in the universe moves at the same breathtaking speed.

好的，所以宇宙中的一切都以同樣令人驚嘆的速度移動。

But this speed is split between space and time, which leads to all sorts of wacky things.

但這個速度是分配在空間和時間之間的，這就導致了各種奇妙的事情發生。

而且我們可以看到時間旅行發生的地方。

When a bus drives past you, it's moving a little bit faster through space than you are.

當公車從你旁邊開過去時，它在空間中的移動速度比你稍微快一點。

So it moves slower through time than you.

所以它在時間中的移動速度比你慢。

Or how it's usually worded, the bus is moving slower through time relative to you.

或者更常見的說法是，公車相對於你的時間移動速度比較慢。

While this makes things feel like weird physics, magic, it's very simple.

雖然這聽起來像奇怪的物理學、魔法，但其實非常簡單。

Move faster through space, go slower in time, move slower through space, go faster in time.

在空間中移動越快，時間就過得越慢；在空間中移動越慢，時間就過得越快。

And if you had another person moving way faster or slower than you, both end up traveling different distances in the time dimension.

如果有另一個人移動的速度比你快很多或慢很多，兩個人在時間維度上最終會移動不同的距離。

The story that's usually told to demonstrate this is to get twins, force one of them into a rocket against their will, shoot them through space super fast while the other twin chills on Earth.

通常用來示範這個概念的故事是，找一對雙胞胎，強迫其中一人搭火箭，然後以超快的速度飛向太空，而另一位雙胞胎則留在地球上。

And because one twin moves very fast through space while the other moves slowly on Earth, they move at different speeds through time.

因為其中一位雙胞胎在空間中移動得非常快，而另一位在地球上移動得比較慢，所以他們在時間中的移動速度也不同。

When the rocket finally gets home, they're no longer the same age.

當火箭終於回家時，他們就不再是同一個年紀了。

And the younger space twin is ready to start.

而年輕的太空雙胞胎已經準備好開始了。

Years of therapy for being abducted by theory.

幾年的心理治療，因為被理論綁架了。

This is the twin paradox, and it makes perfect sense within the rules of the universe.

這就是雙生子佯謬，而且在宇宙規則內是完全說得通的。

If you want to learn more about the paradoxes of time, we made a video about it.

如果你想更深入瞭解時間的佯謬，我們有拍一支影片介紹。

But in a nutshell, you're using time dilation, the fact that your position in time is subjective and only true for yourself.

簡單來說，你就是在運用時間膨脹，也就是你的時間位置是主觀的，只對你自己有效。

With sufficiently fast rockets, you could get as far as you want into the future.

只要有足夠快的火箭，你就能前往你想要的未來。

This way you can witness the end of the universe or look at the final thing that will ever happen.

這樣你就可以親眼見證宇宙的終結，或是看看宇宙中最後會發生的事。

We should mention that there's another way to jump forward in time.

我們要提一下，還有另一種跳躍到未來的方法。

Massive objects bend space time, causing time to go slower near them.

巨大的物體會扭曲時空，讓時間在它們附近流逝得比較慢。

在地球上，這個效應非常微小。

The gravity of our planet makes time pass 0.000000007% slower than in deep space, far from any gravitational fields.

我們星球的重力讓時間流逝的速度比在沒有重力場的深空中慢了 0.000000007%。

If you move into a really strong gravitational field, like around a black the closer you get to the event horizon, the slower time passes for you.

如果你進入一個非常強的重力場，像是黑洞附近，離事件視界越近，時間對你來說就過得越慢。

If we kidnap our twin again, they won't notice it at all.

如果我們再次綁架我們的雙胞胎，他們根本不會注意到。

Their watch ticks as fast as it always does, but

他們的錶走得跟平常一樣快，但是

from the outside, they seem to almost stand still.

從外面看，他們幾乎像是靜止不動。

Only when the twin leaves the gravitational field and comes back to Earth do they realize they time traveled.

只有當雙胞胎離開重力場回到地球時，他們才會意識到自己進行了時間旅行。

Ok, so you can time travel to the future by going fast or near a black hole.

好的，所以你可以透過高速移動或靠近黑洞來進行時間旅行到未來。

But this is pretty lame and has literally only downsides.

但這樣實在有點遜，而且只有壞處。

Except for people who want to sort of teleport into the future.

除了那些想「傳送」到未來的人之外。

And it makes building a gigantic human space empire super Hard, because even if we develop the technology to go really super fast between stars, Going on a faraway journey will always mean leaving your home as you knew it forever.

而且這會讓建立一個龐大的人類太空帝國變得超級困難，因為即使我們發展出超光速星際旅行的技術，一趟遙遠的旅程也總是意味著永遠告別你所認識的家。

But now that we know all of this, there's actually a way we could use the rules of our universe to travel backwards through time.

但既然我們都知道了這些，其實有個方法可以利用宇宙規則來進行時間旅行回到過去。

So you always move through space time at the speed of light.

所以你總是會以光速穿越時空。

If you go fast through the space dimension, you slow down in the time dimension.

如果你快速穿越空間維度，你就會在時間維度中減速。

And here we find an actual opening for backwards.

在這裡我們找到了一個實際的切入點，可以回到過去。

The theory of relativity, which may be the most solid scientific theory we know, does not forbid faster than light motion through space.

相對論，這可能是我們所知最堅實的科學理論，並沒有禁止超光速穿越空間的運動。

If you move through the space dimension faster than the speed of light, superluminal, you need to move through the time dimension with negative speed.

如果你以超光速穿越空間維度，也就是超光速，你需要在時間維度中以負速度移動。

That means you go backwards through time Relative to the rest of the universe, into the past.

這代表相對於宇宙中的其他人，你會向後穿越時間，回到過去。

Actually, scientists have been looking for superluminal particles and given them a name.

事實上，科學家一直在尋找超光速粒子，並為它們命名。

They could exist and would have wild properties like getting f when they lose energy.

它們可能存在，並且會有一些奇怪的特性，像是失去能量時會變得更慢。

And, of course, traveling backwards in time.

Finally, real time travel, Just like with photons, it isn't really possible to clearly define how time passes for tachyons themselves.

終於，真正的時間旅行，就像光子一樣，我們無法清楚定義時間對までの道のり本身是如何流逝的。

It depends on how you move through spacetime relative to them.

這取決於你相對於它們如何在時空中移動。

But now, for the first time, some observers could actually see tachyons literally traveling backwards in time, which means they could be used to directly interact with the past.

但現在，有史以來第一次，一些觀察者實際上可以看到までの道のり字面意義上地向後穿越時間，這意味著它們可以用來直接與過去互動。

In theory, you could use them to send messages to your past self and change all sorts of things that have already happened.

理論上，你可以利用它們向過去的自己傳送訊息，並改變已經發生的各種事情。

Maybe with some tachyon powered sci fi future tech, you could see a star die before it was born, Meet your great grandparents, Prevent your past self from making that one dumb mistake, win the lottery, or get eaten by dinosaurs, and

也許藉由某種超光速粒子驅動的科幻未來科技，你就能看到一顆星星在誕生前就已熄滅、見到你的曾祖父母、阻止過去的自己犯下那個愚蠢的錯誤、中樂透，或是被恐龍吃掉，

create juicy time paradoxes that also kind of break the universe.

並創造出一些聽起來很厲害、但可能會讓宇宙崩潰的時間悖論。

It seems there are things in our universe that are impossible to mix.

看來我們的宇宙裡，有些東西就是沒辦法混在一起。

Unfortunately, the theory of relativ specifically forbids anything that starts out traveling slower than the speed of light to reach the speed of light.

遺憾的是，相對論明確禁止任何一開始速度比光速慢的東西達到光速。

Because moving faster through space requires energy, and

因為在空間中移動得更快需要能量，

the energy required to reach the speed of light is literally infinite.

而要達到光速所需的能量，簡直是無限的。

Even if you could gather all the energy of the universe, you, couldn't accelerate a grain of sand to the speed of light.

就算你能聚集宇宙中的所有能量，也無法讓一粒沙加速到光速。

You can get as close as you like, but you can never reach it.

你可以無限接近，但永遠無法達到。

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我們穿越回了過去，結果物理學家們超生氣！🤯 (We Traveled Back in Time. Now Physicists Are Angry.)

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