the concept of an orbitWe learned in the last post that staying in space and just being in space are not the same thing. To stay in space, you must be in an orbit. Hopefully, you know that an orbit is a circular (elliptical!) "path" around something. The Earth is in orbit around the Sun. The Moon is in orbit around the Earth. The ISS is in orbit around the Earth, too! Thus, the International Space Station is not stationary. If it was, it would have to use large amounts of fuel to hover in position. The ISS moves at 4.76 miles per second- sideways. It IS still falling, though. The basic idea is that it is going so fast sideways that when it falls to the Earth, it "misses." The Earth's gravity is what keeps the ISS from flying away. Same goes for the Moon. The reason this works is because velocity is a vector, a value with both magnitude and direction. So in a perfectly circular orbit, the -9.8 meters per second squared of acceleration (ish) from the Earth doesn't go into changing the magnitude of an orbiting body's speed, it goes into changing its direction. Thus, the Earth's gravity does accelerate the ISS. It just doesn't affect its downward speed much.
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Jacob mitchellI like to play computer games, program, and try my hand at 3D printing. Archives
February 2017
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