If you are not floating away into space right now you may be aware of the concept of gravity. Gravity is an attractive force cause by mass. Large masses like planets have large gravitational forces, this is why it's so tough to jump off the surface of earth and into space.
Satellites are also effected by gravity, so why don't they come crashing down into earth?
Well, if you notice satellites are moving through space quite quickly and there's a reason for this. Technically speaking satellites are always being pulled towards earth (by gravity) but they move fast enough so that they are always falling over the "edge" of earth.
It's almost like a small game. Gravity pulls the satellite in but the velocity keeps it from touching earth. A quote that I just made up to summarize what's happening is, "For every 1 mile the satellite falls it travels enough distance around earth place the earth back 1 mile. This works because the earth is a sphere." Take a look at the amazing diagram that I drew to potentially help you see what's going on.
The arrow pointing towards earth in this diagram represents the force of gravity. While the arrow that is tangent to earths surface is the velocity.
A cool thing to note is that when a satellite is closer to earth it must be going faster. This is because the closer you are to earth the stronger the force of gravity is. Which makes - in this case - the satellite fall faster so it must have a higher velocity to compensate for this extra gravitational pull. In other words the satellite must fall over the "edge" of earth faster.
If the satellite was further away the opposite would happen. As the gravity is much weaker so the satellite doesn't need to orbit as fast.
Last cool note:
Because satellites are in space they don't slow down as there is not air resistance. I.E. Once you're up to speed no fuel is required.
Cheers.
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