Not in motion… in comparison to what?

I know it can seem like a silly question, but bear with me. Most people who haven’t thought a lot about relativity are going to be confused by the question. Because every time they’ve thought about motion the earth has served as a frame of reference. Things have always been “at rest” or “in motion” in relation to the earth. It’s natural to extend this to the universe at large and ask, what is the reference frame for the universe. And what, if anything is at rest in relation to it.

Minor problem. There is no universal reference frame. This is what the Michealson-Morley (sp?) experiment, that “proved” Einstein’s theory of relativity failed to show. They were trying to measure earths motion against the reference frame and… there was no there, there. Science is pretty cool.