《那些古怪又讓人憂心的問題》第111期:地球擴張(4)
t = 5 years
After five years, gravity would be 25 percent stronger. If you weighed 70 kg when the expansion started, you'd weigh 88 kg now.
5年後，重力增加了25％。如果你在擴張開始時有70千克，那麼現在你就有88千克了。Most of our infrastructure would have collapsed. The cause of the collapse would be the expanding ground below them, not the increased gravity. Surprisingly, most skyscrapers would hold up fine under much higher gravity.6 For most of them, the limiting factor isn't weight, but wind.
絕大多數的基礎設施都已經塌了，原因是它們腳底下的土地在擴張，而不是重力變大了。令人驚奇的是，絕大多數摩天大樓在重力顯著變大的情況下仍然十分堅挺。6對它們而言，限制因素不是重量，而是風。
t = 10 years
10年後After 10 years, gravity would be 50 percent stronger. In the scenario where the atmosphere isn't expanding, the air would become thin enough to be difficult to breathe even at sea level. In the other scenario, we'd be OK for a little while longer.
10年後，重力增加了50％。如果大氣不隨着擴張，那麼即使在海平面，空氣也已經稀薄到了無法呼吸的程度。如果大氣一起擴張的話，我們還能再撐一會兒。t = 40 years
40年後After 40 years, Earth's surface gravity would have tripled.7 At this point, even the strongest humans would be able to walk only with great difficulty. Breathing would be difficult. Trees would collapse. Crops wouldn't stand up under their own weight. Virtually every mountainside would see massive landslides as material sought out a shallower angle of repose.
40年後，地球的重力變成了最初的3倍。7此時此刻，即使是最強壯的人也只能勉強才能走路。呼吸也變得很艱難，樹都倒了，糧食被自己的重量壓得擡不起頭。幾乎每座山的山坡都可以見到巨型滑坡，因爲此時的靜止角比以往要更小。Geologic activity would also accelerate. Most of the Earth's heat is provided by radioactive decay of minerals in the crust and mantle,8 and more Earth means more heat. Since the volume expands faster than the surface area, the overall heat flowing out per square meter will increase.
地質運動也會加劇。地球產生的大部分熱來自於位於地殼和地幔之間的放射性物質的衰變放熱，8而更多的物質意味着更多的熱。由於體積擴張的速度比表面積快，因此總體平均每平方米發出的熱量就會變多。It's not actually enough to substantially warm the planet-Earth's surface temperature is dominated by the atmosphere and the Sun-but it would lead to more volcanoes, more earthquakes, and faster tectonic movement. This would be similar to the situation on Earth billions of years ago, when we had more radioactive material and a hotter mantle.
不過這些還不足以使這顆星球溫度大幅升高——地球的表面溫度主要取決於大氣層和太陽——但更多的熱會導致更多火山爆發、地震，以及更快的地殼運動。這和幾十億年前的地球相似，那時地球具有更多的放射性物質，所以地幔溫度會更高。More active plate tectonics might be good for life. Plate tectonics play a key role in stabilizing the Earth's climate, and planets smaller than Earth (like Mars) don't have enough internal heat to sustain long-term geologic activity. A larger planet would allow for more geologic activity, which is why some scientists think that exoplanets slightly larger than Earth (“super-Earths”) could be more friendly to life than Earth-sized ones.
更加活躍的板塊構造對生命來說可能有些好處。板塊構造對穩定地球的氣候起着關鍵作用，而比地球小的那些星球（比如火星）內部沒有足夠多的熱來維持長期的地質運動。更大的星球意味着更多的地質運動，這也是爲什麼一些科學家認爲生命在比地球稍大一些的星球（所謂的“超級地球”）會比和地球差不多大的星球上活得更好一些。
