Can someone explain Inertial Frame of Reference to me better than wikipedia?

Question

So here I was on the porcelain thinking chair when I was thinking about a question on here someone asked about if the earth stopped rotating.   I said something about the earth being an oblate spheroid thanks to it's rotational inertia and left it at that.  But then I got to thinking how we know earth is rotating.  I mean, motion is relative after all.  We tend to think of stars as fixed points of reference but they're not really.  

So lets say we took a rotating planet like earth that is a oblate spheroid thanks to it's inertia and plopped it into an otherwise empty universe.  Without any frame of reference there would be no way to establish it was rotating, would it's rotational inertia simply vanish? Or would we assume there to just be some 'dark force' that acts against gravity keeping earth oblate. 

I read though this which I think describes the answer as "We know it's rotating because we like how the math works better" but I'm not sure if I read it right.
http://en.wikipedia.org/wiki/Inertial_frame_of_reference

K... go.

Big Daddy · Accepted Answer

Good question.  One idea behind it is often known as Mach's Principle.

http://en.wikipedia.org/wiki/Mach%27s_principle

It's difficult to test (since we don't have an empty universe to probe), but yes the idea is that without the rest of the universe to interact with, the planet would not "feel" the rotation.

It is actually possible to use General Relativity to model what happens if the earth were standing still, and the rest of the universe were spinning around it.  It turns out that everything appears the same, and the motion of the universe actually increases the pull on the earth, giving it the same bulge.

I don&#39;t think so · Answer

Some unusual observed physical effects would tell you the Earth was rotating.  The Coriolis effect for instance results in spinning weather systems and long range artillery shells that mysteriously veer off target.  Gyroscopes and pendulums would precess.

DLM · Answer

You could still determine rotation using a Focault pendulum.

Can someone explain Inertial Frame of Reference to me better than wikipedia?

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