700
xkcd #2898: Orbital Argument
(imgs.xkcd.com)
Alt text:
"Some people say light is waves, and some say it's particles, so I bet light is some in-between thing that's both wave and particle depending on how you look at it. Am I right?" "YES, BUT YOU SHOULDN'T BE!"
Pretty sure you can chose earth as fix point and have everything rotate around it on really strange orbits. Everything is kind of relative.
Wouldn't that break relativity tho if you treat the earth as a fixed point? Stuff really far out would have to be going absurdly faster than light to orbit the earth once every 24h. I feel like that's one of the ways to tell whether or not you're rotating, or stuff is orbiting you.
Relativity works when earth is the center because it's relative, we just calculate everything with earth as the frame of reference. It does make a lot of math harder, but that's what we already are doing when using earth based telescopes (although we try to shift the math to a more reasonable frame of reference for most stuff, but earth is always the starting point because we're making all the measurements from here)
If the earth is fixed (not just in position, but in rotation), you're using a non-inertial reference frame, and things get wonky. But you can make the math work.
Why would objects far out need to orbit earth every 24h?
To be honest, physics was never my strong point. If I remember correctly you could chose any point as your observational (?) point but maybe someone with some real physics cred can chime in.