外太空从哪里开始?

罗斯玛丽-是的，这是个好问题。天文学和所有事物的问题是，很少有一个非黑即白的答案。可以说，大气并没有什么优势。它渐渐消失了。所以科学家们把大气层分成了几个不同的层。对我们所有人来说最有价值的，我想也是我们一生都会与之互动的，叫做对流层。75%的大气微粒都在那里。它一直延伸到外逸层，实际上到达了月球的一半。所以这是一个非常大的大气范围。但大多数人认为太空可能在到达月球一半之前就开始了，你知道吗? So in the 1900s there was a scientist named Theodore von Kármán, and he basically calculated the highest point that an aircraft could function within the atmosphere, right? So planes rely on air to provide lift. And so he calculated about 84 kilometers, around there, was the highest point that a plane could fly, relying on lift. Now, he ultimately decided that a hundred kilometers is just a nicer number. There wasn't a lot of science behind that. But a hundred kilometers also happens to be about where a satellite can no longer stay in stable orbit because then you have to take into account the atmosphere interfering with that orbit. So it might destabilize. So the general consensus is around a hundred kilometers. It's not super important, space is space. The only reason that it was kind of concerning is politics. You know, who's controlling what aspects of the air and all that. So, great question. Thanks Emma.

克里斯:目前人们接受的是100公里，不过这个数字有点武断，因为大气层不会停在那里，其他方面也不会停在那里，国际空间站大约有400公里，不是吗?所以距离是它的四倍。但它仍然在大气中因为我和一个太空科学家交谈他们说他们必须定期给它一个推力因为它受到了大气的束状和卷须的阻力甚至在那里也在进步。

罗斯玛丽:对，没错。是的。

克里斯:这就对了。现在您知道了Kármán行。谢谢你，罗斯玛丽。