Have you ever been floating in a swimming pool, all comfy and warm, thinking, "Man, it'd be cool to be an astronaut! You could float out in outer space, look down at the Earth and everything. It'd be so neat!" Only that's not how it is at all. If you are in outer space, you are orbiting the Earth: it's called free fall. You're actually falling towards the Earth. Think about this for a moment: that's the feeling you get if you're going over the top of a roller coaster, going, like, "Whoa!" Only you're doing this the whole time you're orbiting the Earth, for two, three, four hours, days. Whatever it takes, right? So, how does orbiting work? Let's take a page from Isaac Newton. He had this idea, a little mental experiment: You take a cannon, you put it on top of a hill. If you shoot the cannonball, it goes a little bit away. But if you shoot it harder, it goes far enough so that it lands a little bit past the curvature of Earth. Well, you can imagine if you shot it really, really, hard, it would go all the way around the Earth and come back -- boom! -- and hit you in the backside or something. Let's zoom way back and put you in a little satellite over the North Pole of the Earth and consider north to be up. You're going to fall down and hit the Earth. But you are actually moving sideways really fast. So when you fall down, you're going to miss. You're going to end up on the side of the Earth, falling down, and now the Earth is pulling you back in sideways. So it's pulling you back in and you fall down, and so you miss the Earth again, and now you're under the Earth. The Earth is going to pull you up, but you're moving sideways still. So you're going to miss the Earth again. Now you're on the other side of the Earth, moving upward, and the Earth's pulling you sideways. So you're going to fall sideways, but you're going to be moving up and so you'll miss. Now you're back on top of the Earth again, over the North Pole, going sideways and falling down, and yep -- you guessed it. You'll keep missing because you're moving so fast. In this way, astronauts orbit the Earth. They're always falling towards the Earth, but they're always missing, and therefore, they're falling all the time. They feel like they're falling, so you just have to get over it. So technically, if you ran fast enough and tripped, you could miss the Earth. But there's a big problem. First, you have to be going eight kilometers a second. That's 18,000 miles an hour, just over Mach 23! The second problem: If you're going that fast, yes, you would orbit the Earth and come back where you came from, but there's a lot of air in the way, much less people and things. So you would burn up due to atmospheric friction. So, I do not recommend this.
你是否曾经漂浮在游泳池 非常惬意,暖洋洋,遐想不断 “天啦,当一名宇航员太爽了! 你可以在外太空漂浮, 俯瞰地球以及所有的一切。 太棒了!“ 只是事实并不如此。 如果你在外太空, 你将会绕地球转动, 这叫做自由落体。 事实上,你正朝着地球下落。 好吧,就此考虑一会儿。 你得到的感觉是这样的: 就像你坐上云霄飞车,即将爬过顶端 冲吧 “喔喔哦哦~~·!” 只是这回你将一直这样 你将围绕着地球转动 两个 三个 四个 小时, 好几天 无论怎样,对吧? 那么,怎么旋转的呢? 让我们请教一下牛顿吧。 他有这样一个想法, 一个小的心理实验。 你拿来一个大炮, 把它摆在山顶上。 如果你发射炮弹, 射到不远处。 但是如果你更猛地发射, 它将“嗖”的飞到足够远,以至于 它降落在地球表面的曲度以外。 那么, 想象一下, 倘若你非常非常猛地发射, 它也许会绕着地球飞行很远, 然后绕回来,砰! 好比,撞到你后背啥的。 让我们把焦点拉回太空 并把你放在 一个位于地球北极上方的小卫星里 并设北极方向为正向上的。 你将会下落并撞向地球。 然而, 实际上你正在非常快速地向一旁移动。 所以,当你下落的时候, 你不得不错过正下方。 你将最终移动到地球的一边, 你往下落, 而地球把你往一旁拉 也就是说,你被地球往下拉 同时你往正下方降落, 所以,你将再次错过地球。 这时,你已经移动到地球的下面。 地球往上拉你, 但是你仍旧往一旁移动。 所以,你不得不再次错过地球。 现在,你已经移动到地球的另一边, 正往上移动,并且地球正把你拉向一边(垂直朝向地球), 也就是说,你在往一边下落, 但是,你正在(快速地)向上移动,所以你再次错过(地球)。 现在,你再次回到了地球顶端, 北极上方, 往一旁移动,同时向下落, 是的,你已经猜到了。 你将一直错过(地球),因为你正在飞速地移动。 正是如此,宇航员围绕地球飞行。 虽然他们一直朝地球下落, 但他们却一直错过(落回地球), 因此,他们一直在下落。 他们也感觉自己在下落, 你基本上只能接受这样一种感觉。 所以,技术上说,如果你跑得足够快, 突然绊一脚, 你将脱离地球。 但是,这里有个大问题。 第一,你必须每秒跑8公里。 也就是每小时18,000英里 超过23马赫(23倍音速)! 第二个问题: 假设你能移动那么快, 是,你将绕地球运动 并且回到你的起点, 但是一路上会有大量的空气, 当然,极少有人和其他事物。 所以,大气摩擦将导致你燃烧至尽 因此,我并不推荐(这样做)。