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GEOSTATIONARY ORBIT

How it can be that satellites are going round IN ORBIT and yet fixed satellite dishes manage to still be able to point at them!

Satellite TV dishes are sometimes fixed, bolted to the wall, so how do they manage to still be pointing at television satellites which are obviously in orbit and therefore going round and round the earth?

This is done by having the satellites going around the earth at the same speed that the earth is going round, one revolution per day. So, the earth goes round, and the satellites go round at the same speed, and so the satellites seem to remain in the same place in the sky, stationary relative to the geography, in orbits called GEOSTATIONARY orbits. Geostationary orbit satellites are not stationary in space, but they are orbiting, going around the earth at the same rate per day as the earth goes around.

It's not quite as simple as that, because satellites that are 60 miles high go round much faster, at about 18,000 miles per hour, and complete an orbit of the earth in about 84 minutes.

To make a satellite go round much slower it needs to be much higher. Earth's gravity is like a magnet and is weaker the further away you go. The higher a satellite is, the less gravity there is, so it doesn't need to go so fast to stay up.

If a satellite was orbiting as high as the moon, 239 thousand miles away, it would take a month to complete an orbit, the same time as the moon takes.

Somewhere inbetween is the right height to orbit so a satellite takes exactly 24 hours to go around the earth, so it always stays over the same piece of the earth. That height is about 22,500 miles.

It also has to be going round the same way as the earth!

Geostationary orbit satellites have to orbit over the equator, because otherwise they would swing north and south. That's why Sky TV satellite dishes in the UK point South, because the satellite is overhead over the equator. You can use this effect as a conjuring trick explained here as Alternative Satellite Navigation

More about how basic orbiting works at the page of ORBITS