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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Suppose a satellite is in orbit (non geosynchronous). Then imagine that the rotation of the earth magically changes so that it is spinning at the same speed the object is orbiting. That wouldn’t affect the orbit of the satellite at all, except that you can now call its orbit “geosynchronous”. This shows that geosynchronous orbit is really just a coincidence between a particular orbit, and a particular rotational speed of the earth.
The only case in which that would be a problem would be if the earth wasn’t spinning at all. Then a “geosynchronous” satellite *would* fall out of the sky.
Geosynchronous orbit only means the orbital velocity will match the rotational velocity of the earth.
Orbits get slower the higher you go, so objects in geosync (37000km) go much slower than those at 400km. Go higher, and the speed relative to the Earth is lower. Someone standing on earth would notice the satellite to moving in reverse, eventhough it isn’t.
Suppose a satellite is in orbit (non geosynchronous). Then imagine that the rotation of the earth magically changes so that it is spinning at the same speed the object is orbiting. That wouldn’t affect the orbit of the satellite at all, except that you can now call its orbit “geosynchronous”. This shows that geosynchronous orbit is really just a coincidence between a particular orbit, and a particular rotational speed of the earth.
The only case in which that would be a problem would be if the earth wasn’t spinning at all. Then a “geosynchronous” satellite *would* fall out of the sky.
Geosynchronous orbit only means the orbital velocity will match the rotational velocity of the earth.
Orbits get slower the higher you go, so objects in geosync (37000km) go much slower than those at 400km. Go higher, and the speed relative to the Earth is lower. Someone standing on earth would notice the satellite to moving in reverse, eventhough it isn’t.
Things in low orbit zip around the planet every 90 minutes or so. The moon, on the other hand, is in a very high orbit, and takes almost a month to orbit the earth. Somewhere in between, there is a circular orbit whose period is exactly 24 hours – it orbits around the earth at the same rate the planet spins. This is called a geosynchronous orbit. If it’s above the equator, there is no north/south drift, so the satellite stays above one spot on the surface – this is a geostationary orbit.
The earth is spinning on it’s axis. Like a basketball on someone’s finger. That’s why we have days. Our point on the earth goes round and round, passing under the sun and then to the backside into night.
Since WE are spinning, any object that is “hanging” over a single spot on the planet must be circling around the earth at that same speed. The “single point” on the earth is moving, and so we know the satellite is also moving.
Geosynchronous orbit is the distance from the earth, a little over 22,000 miles, at which the speed the satellite is traveling in order to “fall/miss” in a stable orbit is the same speed as it needs to travel to keep a steady position over a point on the spinning earth.
The earth is spinning on it’s axis. Like a basketball on someone’s finger. That’s why we have days. Our point on the earth goes round and round, passing under the sun and then to the backside into night.
Since WE are spinning, any object that is “hanging” over a single spot on the planet must be circling around the earth at that same speed. The “single point” on the earth is moving, and so we know the satellite is also moving.
Geosynchronous orbit is the distance from the earth, a little over 22,000 miles, at which the speed the satellite is traveling in order to “fall/miss” in a stable orbit is the same speed as it needs to travel to keep a steady position over a point on the spinning earth.
The earth is spinning on it’s axis. Like a basketball on someone’s finger. That’s why we have days. Our point on the earth goes round and round, passing under the sun and then to the backside into night.
Since WE are spinning, any object that is “hanging” over a single spot on the planet must be circling around the earth at that same speed. The “single point” on the earth is moving, and so we know the satellite is also moving.
Geosynchronous orbit is the distance from the earth, a little over 22,000 miles, at which the speed the satellite is traveling in order to “fall/miss” in a stable orbit is the same speed as it needs to travel to keep a steady position over a point on the spinning earth.
Suppose a satellite is in orbit (non geosynchronous). Then imagine that the rotation of the earth magically changes so that it is spinning at the same speed the object is orbiting. That wouldn’t affect the orbit of the satellite at all, except that you can now call its orbit “geosynchronous”. This shows that geosynchronous orbit is really just a coincidence between a particular orbit, and a particular rotational speed of the earth.
The only case in which that would be a problem would be if the earth wasn’t spinning at all. Then a “geosynchronous” satellite *would* fall out of the sky.
From KSP2
For geostationary, the altitude is picked to keep the angular speed equal to a spot on the ground. Other good technical descriptions in the comments.
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