KWON O CHUL AstroPhotography

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Why don't satellites fall into the Earth?

Have you ever wondered why the International Space Station or satellites in the sky don't fall back onto Earth? Well, the first great scientist to think about this was actually Sir Isaac Newtion, as a matter of fact.

Let's throw a ball as far as we can. It falls back towards the ground. That's because Earth's gravity is pulling it back down. If we threw it from a higher place, it flies farther before falling to the ground. And if we throw it really, really hard from way up above the ground where there's no air friction? The ball would have fallen back towards the ground, but since the Earth is round, it will never reach the ground. The ball will keep circling Earth.

To become a satellite, it must fly at a speed of more than 7.9 km/s. But what happens if it fly much faster than this? If its speed is over 11.2 km/s, it can escape Earth's gravity. If it were a spacecraft exploring other planets, it would have to fly faster than this.

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