There are five large worlds that share names with chemical elements: the planets Mercury, Uranus, and Neptune, and the dwarf planets Ceres and Pluto.

有五個星球的名稱與化學元素相同：水星、天王星和海王星等行星，以及穀神星跟冥王星等矮行星。

What if, to have some fun, each world suddenly composed of its corresponding element?

假如每個星球突然都由其名稱相對應得的元素組成會怎麼樣？

Mercury and cerium are metals, so Mercury and Ceres would mostly just get slightly heavier and shinier.

汞和鈰是金屬，所以穀神星和水星大多只會變得更重、更亮一些。

From earth, they'd look a bit brighter in the night sky enough that Ceres would become visible to the naked eye. 

從地球上來看，它們在夜空中看起來會更亮一點，足以讓穀神星變得肉眼可見。

Unfortunately, the night sky and human eyes would get a little harder to find, thanks to the other planets.

不幸的是，夜空和人眼會因為其他行星的關係，而變得有點難找。

Plutonium, uranium and neptunium are radioactive.

鈈、鈾和錼具有放射性。

Plutonium and uranium do have non-fissile isotopes which decay slowly and mainly produce a bit of heat.

鈈和鈾有非裂變的同位素，它們衰變緩慢，大部分會稍微發熱。

A small lump of Uranium's most common and stable isotope wouldn't even be hot to the touch.

一小塊鈾的最常見且最穩定的同位素甚至摸起來都不會熱。

But if you collected it into a planet-size ball, the tiny amount of heat produced by each part would add up to heat up the planet to thousands of degrees.

但是，如果你把它聚集成一個行星大小的球，那麼每一小部分產生的熱量加起來會使地球升溫到數千度。

It might seem strange that something that's cool in small amounts would be hot when collected together in a big ball, but this is  just a consequence of geometry and the physics of radiating heat.

這看似奇怪，在少量時很涼的東西，聚集成一個大球就會變熱，但這其實只是輻射熱的幾何學及物理學結果。

Since volume grows faster than surface area, and the volume is where the heat is produced, the interiors of large heat-producing objects produce more heat relative to their surface areas.

由於體積的增長速度比表面積的增長速度快，而體積是發熱的地方，因此大型發熱物體的內部相對於其表面產生較多的熱量。

But thermodynamics doesn't allow objects to just radiate more heat, they have to get hotter to do so.

但熱力學並不允許物體直接輻射出更多的熱量，他們必須變得更熱才能這麼做。

The hotter they are, the more heat they're allowed to radiate.

他們越熱，被允許輻射出的熱量就越多。

So, a large heat-producing object will produce more heat than it can radiate away until that heat builds up, and the object gets hot, hot enough that it can radiate away enough heat.

因此，一個大型發熱物體會產生比它的可能熱輻射更多的熱量，直到這些熱量積累足夠，並熱到能夠散發出足夠的熱量。

Really big objects can get extremely hot from just a tiny amount of heat production per unit of volume.

超大型物體可能會因每單位體積產生的極少熱量而變得非常熱。

Like, the sun.

例如，太陽。

A cup of the sun's core produces about 60 milliwatts of thermal energy.

一杯太陽核心產生大約60毫瓦的熱能。

By volume, that's about the same heat production rate as the body of a lizard, and substantially less than that of a human.

按體積計算，這與一隻蜥蜴身體的產熱率大致相同，且遠低於人類產生的熱量。

In a sense, you are hotter than the sun–there's just not as much of you. 

因此，你比太陽更熱—只是沒有那麼多的你(可以產熱)。

But, we were talking about Uranus, which there is a lot of, and which would get really really hot if made from uranium.

但我們談的是天王星，如果它是由鈾製成的，它會有很多鈾而且會變得非常非常熱。

The real Uranus, lit by the sun, is too dim to see with the naked eye.

真正的天王星在太陽的照耀下太過暗淡，所以肉眼無法看見。

But the super hot uranium Uranus would glow bright enough to be visible like an ordinary star in the night sky.

但極熱的鈾天王星會發出夠亮的光芒，就像夜空中一顆普通恆星一樣可見。

And plutonium Pluto would heat up and glow enough that from earth; it would also be visible to the naked eye, though just barely. 

而冥王星的鈽會變熱並發光，以至於從地球上也能用肉眼看見，儘管只是勉強可見。

Except you wouldn't be spending much time looking at the night sky anymore, thanks to neptunium Neptune.

除非你因為錼海王星不會再花太多時間看夜空了。

Even the most stable neptunium isotope is fissile, so 237 Neptune would instantly undergo a runaway fission chain reaction, converting the planet into an expanding cloud of high-energy particles and X-rays.

即使最穩定的錼同位素也是可裂變的，因此錼237會立即發生失控的裂變連鎖反應， 將海王星轉化為一個不斷擴大的高能粒子及X射線雲。

Around four hours later, the shock wave would reach—and completely obliterate—the Earth, stripping away its surface and everything on it and leaving behind a molten blob.

約四小時後，衝擊波將到達並徹底毀滅地球，剝去表面及上面的一切，留下一個融化的斑點。

We'd have gotten similar results for Uranus and Pluto if we'd instead used fissile isotopes of uranium or plutonium, though as a bonus, Uranus' shock wave would reach and destroy us about an hour faster than Neptune's,

如果我們改用鈾或鈈的裂變同位素，將會在天王星和冥王星上得到類似的結果，而且天王星的衝擊波會比海王星的衝擊波快一個小時到達並摧毀我們。

There's a simple takeaway from all this: If you have a choice between isotopes and you're not sure which to pick, go for the most stable one. 

從這一切中可以得到一個簡單的結論：如果你可以從中選擇一個同位素，如果不確定該選哪一個，就選最穩定的那個。

And just stay away from neptunium altogether. 

而且要離錼遠一點。

Ok, so I'll avoid neptunium.

好，我會避免使用錼。

But what if to be silly, we filled the solar system with soup out to Jupiter?

但是如果我們愚蠢地用湯灌滿木星會怎麼樣呢？

Or what if to pass the time we spun the earth up so that a day lasted a second?

或者，如果我們想打發時間便把地球旋轉起來，讓一天只持續一秒鐘呢？

Or what if to avoid getting in trouble you tried to read every single law that applies to you?

或者是你如果為了要避免惹上麻煩，試著閱讀每一條適用於你的法律會怎麼樣呢？

What if to answer these questions, you could just read a book called "What If? 2" that this video is based on and supported by?

如果要回答這些問題，你可以直接閱讀一本名為《Ｗhat if 2》的書，這支影片就是根據這本書所拍攝。

What if two reasons to read "What If? 2" are that it was written by Randall Munroe and that it has over 60 answers to important "what if" questions, like "what if Japan disappeared?"

必看《Ｗhat if 2》的兩個理由：這本書是由 Randall Munroe 寫的，以及它解答了超過60個重要的「如果...的話怎麼辦?」的問題，例如 「如果日本消失了怎麼辦？」。

What if to read "What If 2", you just had to look at the information in the description of this video?

如果想要閱讀《What if 2》，你只需要看一下影片下方的資訊欄。

"What If 2", to be clear, is available wherever books are sold, and when you get yourself a copy, then you can ask "what if", too.

確切來說，你可以在各大書店買到《What if 2》。當你買了一本後，你也可以問 「如果...?」。