B1 中級 12653

 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. 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 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! and, like, 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. 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. 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 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, alright, much less people and things. So, you would burn up due to atmospheric friction. So, I do not recommend this.

# 【TED-Ed】在外太空自由落體會怎樣？(Free falling in outer space - Matt J. Carlson)

12653

1. ## 1. 單字查詢

在字幕上選取單字即可即時查詢單字喔！

2. ## 2. 單句重複播放

可重複聽取一句單句，加強聽力！

3. ## 3. 使用快速鍵

使用影片快速鍵，讓學習更有效率！

4. ## 4. 關閉語言字幕

進階版練習可關閉字幕純聽英文哦！

5. ## 5. 內嵌播放器

可以將英文字幕學習播放器內嵌到部落格等地方喔

6. ## 6. 展開播放器

可隱藏右方全文及字典欄位，觀看影片更舒適！

1. ## 英文聽力測驗

挑戰字幕英文聽力測驗！

1. 點擊展開筆記本讓你看的更舒服

1. UrbanDictionary 俚語字典整合查詢。一般字典查詢不到你滿意的解譯，不妨使用「俚語字典」，或許會讓你有滿意的答案喔