Welcome to brain Stuff from house Stuff works dot com where smart Happens. Hi Am Marshall Brain with today's question, how do satellites orbit the Earth? Satellites are to some degree mysterious objects. They travel in space, which feels like an exotic place because most of us have never been there. They're so far away we can't see them. They usually cost millions or billions of dollars, which means none of
us will ever own one personally, and so on. Orbital mechanics can also be mysterious because there's no easy way for us to experience orbital mechanics personally. However, with a little imagination, you can understand the basic idea behind orbital mechanics very easily. Think about what happens when you throw a ball. Imagine that you're standing in a big field and you throw a baseball as hard as you can, like a picture. The ball might go a hundred feet
and then hit the ground. You put the ball into orbit. It's just that the ball's orbit is very very short. Now, imagine that you shot a rifle straightened level instead of throwing a ball. The bullet might travel a mile before succumbing to gravity and hitting the ground. Now, imagine that you shoot a very large and powerful cannon that's able to give its shell an extremely high initial velocity. Imagine
that the cannon is shot straight and level. The shell is going to go many miles far enough to actually follow the curve of the Earth for a period of time before hitting the ground. One thing that gums these examples up is air resistance. So imagine that you took this powerful cannon to the Moon and you mounted it on top of the highest mountain. The Moon has no real atmosphere and is completely surrounded by the vacuum of space.
If you adjusted the speed of the shell just right and shot the cannon, the shell would follow the curve of the Moon perfectly. It would fall at exactly the same rate that the curve of the Moon falls away from it, so it would never actually hit the ground. Eventually, it would curve all the way around the Moon and ram right into the back of the cannon. On the Moon.
You could actually have satellites in extremely low orbits like that just a few miles off the ground to avoid the mountains, and the satellites could conceivably be launched from powerful cannons on Earth. It's not so easy, because satellites have to get up above the atmosphere and into the vacuum of space to orbit for any length of time. Two miles up is about the minimum to avoid atmospheric interference.
The Hubble Space Telescope orbits at an altitude of three hundred eighty miles or so, but the principle is exactly the same. The speed of the satellite is adjusted so that it falls to Earth at exactly the same rate that the curve of the Earth falls away from the satellite. The satellite is perpetually falling, but it never hits the ground. Do you have any ideas or suggestions for this podcast? If so, please send me an email at podcast at
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