View Full Version : Einstein's Theory of Relativity...

02-04-2005, 07:40
This is a question about Einstein's Theory of Reativity, I was thinking about this last night.

Right, you know that Einstein's Theory of Reativity says if your on point 'A' (lets say the Earth) and you look at point 'B' (lets say it's the sun) it is impossible to tell what point is orbit which, is the sun orbiting Earth or is the Earth orbiting the Sun? So does that mean if you went into space and looked at both point 'A' and 'B' would you still not be able to which is orbiting the other? Or would you be able to tell?

I hope you understand this.:)

02-04-2005, 07:43
Bad example, as you would know which is orbiting which simply by common sense. I understand what you mean, though.

The point of the principle of relativity is that there is no difference. One object is moving relative to another. There's no way of telling because there's nothing to tell.

02-04-2005, 07:46
I thought it was a bad example, sorry.

So what you are saying is that even if you were some where else observing the two, you still woudn't know?

02-04-2005, 07:51
Consider the situation. You are some distance away, stationary relative to one of the objects, watching the other 'orbiting' it. Fair enough.

But who says your viewpoint is special? What if you were stationary relative to the other object? You'd then be watching the first object 'orbit' the second. There's no reason to prefer any viewpoint over any other.

02-04-2005, 07:54
I get it now, cheers.

02-04-2005, 08:00
No worries. It can be a confusing theory, so just do your best to suspend disbelief and take everything exactly as it's said.

03-04-2005, 13:06
Actually with orbits they both rotate around the common centre of gravity of the system so they both move around the same point where ever you observe from.

03-04-2005, 13:40
Strictly yes, that's why it's a bad example. Special relativity doesn't discuss gravity so for the sake of 'reference frame' arguments like this one, you ignore it.

04-04-2005, 00:32
If i remember rightly in my Elite days,
You based your speed relative to the object with the largest mass. (within range/reason)
I was explained this theory by someone saying imagine you are standing on a train, relative to people beside the tracks you are moving, but relative to people on the train, you are not.
And you just take it further with planets and orbits blah blah blah ya?

04-04-2005, 10:32
I read a book that explained it with planets, that's why I used that example. I know it was a bad example, sorry.:rolleyes: