eli5: I’ve heard orbit described as continuously falling past or missing the Earth, how then do objects in geosynchronous orbit above a single point not fall out of the sky?
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The orbiting object is moving at high speed, but at a very high altitude so that as the Earth rotates (once every 24 hours) the object is always over the same spot. Everything is moving, but from the ground it seems to hold still.
Because the Earth is rotating. Geosynchronous just means orbiting as fast as the Earth rotates, or one revolution every 24~ hours. The satellite is still “falling sideways” as they say, just at a speed that matches the rotation of the Earth.
Lot of people focused on the “geosynchronous” aspect, but I’m going to shorthand an explanation I read regarding the “falling” part to help that make sense.
Imagine for a second you shot a cannon. The ball will go a good distance and then fall to earth. If you shoot it with even more energy, it will start faster and go farther. But it’s still falling.
Now, picture shooting the ball out of the cannon so fast that it starts to fall, but by the time it starts to fall it’s gotten to the horizon, and it falls in an arc that matches the curvature of the earth – it would miss the earth, but just keep continually falling.
As some have said, close to earth it would have to go REALLY fast to do that. But higher up, it’s got some more room to fall, and doesn’t have to go quite as fast. This is what “orbit” is – continually falling to earth.
“Geosynchronous” just means it’s at that place where it’s high enough over the earth, but not too high, such that the speed it needs to go to continually fall is the same rotational speed as the earth – so you’re in “synch” with it. You’d have to be traveling in the same direction as the earth is rotating.
Lot of people focused on the “geosynchronous” aspect, but I’m going to shorthand an explanation I read regarding the “falling” part to help that make sense.
Imagine for a second you shot a cannon. The ball will go a good distance and then fall to earth. If you shoot it with even more energy, it will start faster and go farther. But it’s still falling.
Now, picture shooting the ball out of the cannon so fast that it starts to fall, but by the time it starts to fall it’s gotten to the horizon, and it falls in an arc that matches the curvature of the earth – it would miss the earth, but just keep continually falling.
As some have said, close to earth it would have to go REALLY fast to do that. But higher up, it’s got some more room to fall, and doesn’t have to go quite as fast. This is what “orbit” is – continually falling to earth.
“Geosynchronous” just means it’s at that place where it’s high enough over the earth, but not too high, such that the speed it needs to go to continually fall is the same rotational speed as the earth – so you’re in “synch” with it. You’d have to be traveling in the same direction as the earth is rotating.
Lot of people focused on the “geosynchronous” aspect, but I’m going to shorthand an explanation I read regarding the “falling” part to help that make sense.
Imagine for a second you shot a cannon. The ball will go a good distance and then fall to earth. If you shoot it with even more energy, it will start faster and go farther. But it’s still falling.
Now, picture shooting the ball out of the cannon so fast that it starts to fall, but by the time it starts to fall it’s gotten to the horizon, and it falls in an arc that matches the curvature of the earth – it would miss the earth, but just keep continually falling.
As some have said, close to earth it would have to go REALLY fast to do that. But higher up, it’s got some more room to fall, and doesn’t have to go quite as fast. This is what “orbit” is – continually falling to earth.
“Geosynchronous” just means it’s at that place where it’s high enough over the earth, but not too high, such that the speed it needs to go to continually fall is the same rotational speed as the earth – so you’re in “synch” with it. You’d have to be traveling in the same direction as the earth is rotating.
The farther away from earth you are, the slower you fall and the slower you need to move to keep missing.
At some point that speed happens to match earths rotation speed.
The farther away from earth you are, the slower you fall and the slower you need to move to keep missing.
At some point that speed happens to match earths rotation speed.
The farther away from earth you are, the slower you fall and the slower you need to move to keep missing.
At some point that speed happens to match earths rotation speed.
They are going JUST the right speed, in the same direction as the planet’s rotation is going.
Objects in Geosynchronous orbit are *still falling*, they’re just falling at the *same speed as the earth is rotating*.
Since the earth can more or less be thought of as a sphere, therefore the effect it has on gravity is still a sphere, no matter which way it’s facing. In the same way that driving on the outside of a turn on a racetrack is slower than driving on the inside, the further away you are from earth the easier it is to continuously “miss,” the earth as you fall, allowing it to keep pace with the speed the earth is spinning.
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