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TED-Ed 052・・Free falling in outer space （宇宙空間での自由落下 )

内容は簡単ですが かなり早い（早口の会話に近い）。

難　03分・・215wpm　　2014/02/12 新出
　
★下記英文はグ-グルのマウスオ-バ-辞書が使えます｡

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!" 　（Man＝うわっ 間投詞　　it'd = it would 口語)

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. Alright, 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, "Whoooooaaaahhhh!" 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 cannon ball, 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(カーブ） of Earth.

Well, you can imagine if you shot it really, really, really hard, it would go all the way around the Earth and come back, boom!（ドカーン） and, like, hit you in the backside or something. Alright, 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（地球に落ちない）. You're going to end up on the side of the Earth, falling down, and now the Earth is pulling you back in sideways. Alright, and 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. And 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. Alright, so you're going to fall sideways, but you're going to be moving up and to a miss. And 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. 　　　(Yep=うん 　Yes はい のラフな言い方）

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 kind of 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 8 kilometers a second. That's 18,000 miles an hour, just over Mach（マッハ） 23 ! (英語の['mɑ：k] の発音に注意）

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, alright, much less people and things. So, you would burn up due to atmospheric friction.

So, I do not recommend this.