The Earth is huge — its surface area is over 500 million square kilometers, and it currently holds over seven billion people.

地球超大，其表面積超過五億平方公里，且目前容納超過七十億人口。

But it's nothing compared to the solar system, which is billions of kilometers across.

但與橫跨幾十億公里的太陽系相比，地球根本小兒科。

And that is still nothing compared to the Milky Way galaxy.

但就連這麼廣大的太陽系，也比不上銀河系。

And if we zoom out even more, we can really start to appreciate how huge the universe actually is.

若再拉遠些，我們就會了解宇宙到底有多大。

But we might be able to take this one step further — because we might be living in something called a multiverse,

或許還能更進一步——因為我們可能住在所謂的平行宇宙，

where there is not just one universe, but potentially an infinite amount of them.

也就是不只一個宇宙，而是有無數個宇宙。

And if this is true, some scientists think that we have the Big Bang to thank.

若這是真的，有些科學家認為，是大爆炸造成了這一切。

See, for a fraction of a second after the Big Bang, the universe expanded incredibly quickly and then stopped.

大爆炸後不到一秒內，宇宙快速膨脹，然後瞬間停止。

And over the next 14 billion years, it cooled down and formed stars, galaxies, and eventually life!

其後的一百四十億年，宇宙冷卻下來，形成恆星、銀河，最終形成生命。

But there's reason to believe that there are some pockets of space that haven't stopped inflating, and some others that have at different times.

可以相信，宇宙中有些空間其實還沒停止膨脹，其他則在不同時間點停止。

This is called the "eternal inflation" theory, and each of these bubbles of space forms its own, isolated universe.

這就是「永恆膨脹」理論，每個空間都有如泡泡，各自形成獨立的宇宙。

And interestingly, the laws of physics and the fundamental constants might not be the same here.

有趣的是，每個宇宙的物理定律和基礎常數可能都不太一樣。

And that got me thinking: what would a parallel universe even be like?

這不禁讓我猜想：平行宇宙到底是什麼樣子？

Well, in a lot of these universes, you and I might not even exist — sorry sci-fi fans, I know that's hard to hear.

在眾多宇宙中，你跟我可能根本不存在。科幻迷們，拍謝啦！我知道這難以接受。

See, if the laws of physics were different enough — like (if) the forces between particles were too weak, atoms might never form.

如果物理定律差異夠大，像是，粒子間的作用力太弱，原子就根本不會形成。

And that means no molecules, no stars and planets, and no life.

也就不會有分子、恆星和行星，甚至是生命。

Sounds pretty boring over there — worst vacation spot ever!

那邊聽起來真無聊。史上最糟的旅遊景點！

That said, there's also the possibility that the laws of physics in some of those universes are so close to ours that intelligent life is possible.

但可能有些宇宙的物理定律和我們相似，智慧生物也就有可能存在。

And if there is an infinite amount of them, it's pretty likely that there's a bubble universe that's very similar to our own.

而且如果有無數多個宇宙，極有可能其中一個會與我們的宇宙極為相似。

Maybe in another universe, I'm really buff and strong. Okay, I'm not gonna get carried away.

或許在另一個宇宙中，我有肌肉又強壯。好啦，不要再沉迷幻想了。

And interestingly, it is theoretically possible that some of these neighboring universes can collide with each other.

有趣的是，理論上相鄰的宇宙是有可能會互相碰撞的。

In fact, it's possible that our universe may have collided with others in the past.

事實上，我們的宇宙可能就曾和其他宇宙碰撞過。

The main hypothesis is that a collision like this might have left a mark on the cosmic microwave background that we can detect.

主要假說指出，宇宙碰撞可能會在宇宙背景輻射中留下痕跡，而我們能藉偵測得知。

But sadly, the researchers haven't found anything so far, and there isn't any proof that parallel universes even exist.

但很可惜，目前為止，研究人員還未找到證據證明平行宇宙的存在。

But if they do, and if they contain life, it would be interesting to see what that life was like.

但若平行宇宙真的存在，且能孕育生命，目睹那些生命體一定非常有趣。

What do you think ?

你覺得呢？

Do you believe that parallel universes are out there?

你相信有平行宇宙嗎？

Let me know in the comments!

留言告訴我！

And if you want to know why we haven't found life in our galaxy yet, click here to find out.

如果想了解為何在銀河系還沒發現生命，點擊此處一探究竟。

There's a link in the description if you're on mobile.

如果你是使用手機觀看，說明欄有連結。

As always, I'm Blocko.

老樣子，我是 Blocko。

This has been Life Noggin.

而你收看的是《Life Noggin》。

Don't forget to keep on thinking.

別忘了時刻動腦。