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Today we are answering an age-old very scientific and important question: What if the moon crashes into earth?
今天，我们要回答一个古老的、非常科学和重要的问题：如果月球撞上地球会怎样？
It's more interesting and weird than you probably think. Let's start with the basics: Why isn't the Moon on its way to crash into us already?
这比你想象的更有趣、更奇怪。让我们从最基本的问题开始：为什么月球还没有撞上地球？
We know that earth's gravity pulls everything towards it, including the Moon, but somehow, it stays up, as if suspended by some opposite force.
我们知道地球的引力把一切都拉向它，包括月球，但不知何故，它却保持着向上的状态，就像被某种反作用力悬浮着一样。
But there is no other force countering gravity - instead, the trick to staying up is a 'sideways' motion that we call an orbit.
但是没有其他力量可以抵消引力——相反，保持向上的诀窍是一种“侧向”运动，我们称之为轨道。
You see orbits every day: when you throw a ball it makes a tiny little orbit.
你每天都会看到轨道：当你扔一个球时，它会绕着一个很小的轨道运行。
The only difference between that ball's orbit and the moon's is that the ball eventually hits the ground. Basically, the reason is speed.
那个球的轨道和月球轨道之间的唯一区别是球最终会撞到地面。基本上，原因是速度。
If you could throw your ball fast enough, it would bend around the world and come back to you. If there was no air slowing it down, it could orbit forever.
如果你能足够快地扔球，它会绕着地球转一圈再回到你身边。如果没有空气减慢它的速度，它就可以永远绕着轨道运行。
And this is what the moon does: Falling sideways around earth, very fast, with no air slowing it down. Orbiting earth every 27 days, at 3600 km/h.
月球就是这样：以非常快的速度绕地球侧坠，没有空气减慢它的速度。每27天绕地球运行一次，速度为3600公里/小时。
So for the moon to just stop in its orbit and plummet to the earth would break more laws of physics than we have time to explain.
如果月球只是在轨道上停下来并坠落到地球上，就会违反很多物理定律，而我们来不及解释。
So how do we crash it into earth? In a nutshell, to change an object's orbit, you need to change its speed, which changes where gravity takes it.
那么我们如何让它撞向地球呢？简而言之，要改变物体的轨道，你需要改变它的速度，从而改变重力将它带到的位置。
But even small changes require enormous forces, which is why all the large objects in the solar system are so stable nowadays.
但即使是很小的变化也需要巨大的力量，这就是为什么如今太阳系中的所有大型物体都如此稳定的原因。
According to science, the moon is big and very massive. Even igniting billions of rocket engines all over its surface would barely move the Moon.
根据科学，月球很大，质量很大。即使在其表面点燃数十亿个火箭发动机也几乎无法移动月球。
It looks like nothing short of magic will make the moon fall. So we'll use a magic spell that slows down the moon so much that it changes its orbit and spirals towards earth.
看起来只有魔法才能让月球坠落。所以我们将使用一个魔法咒语，让月球的速度大大减慢，从而改变其轨道并向地球旋转。
To get the most from the experience, the moon will take exactly one year before it hits earth. Ready? 3. 2. 1.
为了从经验中获得最大收益，月球将在一年内撞击地球。准备好了吗？
Magic Month 1 For the first few days, nothing really changes.
最初几天，什么都没有改变。
The moon gets a tiny bit brighter and scientists get confused, but the rest of us don't notice anything different.
月球变得稍微明亮了一点，科学家们感到困惑，但我们其他人没有注意到任何不同。
The only noticeable real effect of the moon on the earth are the tides. Tides exist because while earth pulls on the moon, the moon's gravity pulls back on the earth.
月球对地球唯一明显的实际影响是潮汐。潮汐之所以存在，是因为地球拉着月球，而月球的引力又拉着地球。
Since the strength of gravity gets weaker with distance, different parts of the earth feel a slightly different pull.
由于引力的强度会随着距离的增加而减弱，地球的不同部分会感受到略有不同的拉力。
Which causes the earth, especially the oceans, to bulge when the moon is above them, and contract a little on the sides when it's not.
这导致地球，尤其是海洋，在月亮高悬天空时会凸起，而月亮不在时，侧面则会稍微收缩。
As earth rotates every day underneath the moon, the moon's influence fluctuates, causing the water-level of the oceans to rise and fall by about half a meter twice a day.
随着地球每天在月球下方旋转，月球的影响也在波动，导致海洋水位每天两次上升和下降约半米。
But with the moon drawing ever closer, high tide gets higher every day.
但随着月球越来越近，潮汐每天都在升高。
At first barely noticeable, within a month the moon has covered half the distance to the earth and ocean tides have grown to 4 meters.
起初几乎察觉不到，一个月之内，月球已经覆盖了地球距离的一半，海洋潮汐已经增长到4米。
Everyday high tide comes and waves flood coastal cities. And there is no end in sight.
每天都有涨潮，海浪淹没沿海城市。而且看不到尽头。
With the moon drawing ever closer, tides rise ever higher, inundating another city and more inhabited land with salty water every day.
随着月球越来越近，潮汐涨得越来越高，每天都有咸水淹没另一个城市和更多有人居住的土地。
Month 2 By the end of month 2 the moon has covered two-thirds of the distance to earth, and global infrastructure is crumbling as tides rise above ten meters – displacing up to a billion people who happen to live near the coastlines.
到第二个月末，月球已经覆盖了地球距离的三分之二，随着潮汐涨到十米以上，全球基础设施正在崩溃，多达十亿恰好住在海岸线附近的人流离失所。
As ports become inoperable shipping grinds to a halt. Not only will it slow down the delivery of Kurzgesagt products but also less exciting things like food.
随着港口无法运营，航运陷入停顿。这不仅会减慢Kurzgesagt产品的交付速度，还会减慢食物等不那么令人兴奋的东西的交付速度。
Global communications fall into disarray – 95% of the internet is carried by ocean-crossing cables, and while these largely don't mind the water, their terminals on land do.
全球通信陷入混乱——95%的互联网是通过跨洋电缆传输的，虽然这些电缆大多不受水的影响，但它们在陆地上的终端却很介意水。
Living inland doesn't guarantee safety either, tidal bores cause rivers to flow backwards, carrying saltwater to contaminate surface and groundwater supplies.
居住在内陆地区也不能保证安全，潮汐涌动会导致河流倒流，携带盐水污染地表和地下水供应。
Gas shortages follow, as oil refineries near the coast are abandoned. Countries are left with the supplies they had on their shelves and strict rationing will begin.
随着沿海炼油厂被废弃，随之而来的是天然气短缺。各国只剩下货架上的供应，严格的配给制将开始。
In the cities, chaos reigns during the scavenging hours of low tide, while survivors take refuge in highrises when the water returns.
在城市里，低潮时一片混乱，而幸存者在潮水回流时躲进高楼大厦。
Month 3 Three months in and the moon is close enough to disrupt communication and navigation satellites.
三个月后，月球已经足够接近地球，可以干扰通信和导航卫星。
While it is normally far too distant for its gravity to cause any major problems for our satellites, the closer it gets the more warped their orbits become.
虽然它通常离地球太远，以至于它的引力不会对我们的卫星造成任何重大问题，但它离地球越近，它们的轨道就越扭曲。
As their fuel for orbital corrections runs out, satellites careen out of control.
随着轨道校正燃料耗尽，卫星失控。
Month 4 - 5 On earth, the tides are rapidly growing to about 30 meters and will be reaching 100 meters in height in a few short weeks.
第4至5个月，地球上潮汐正在迅速增长到大约30米，并将在短短几周内达到100米高。
