Do you need a frame of reference against which to measure rotational velocity?

Or, is there such a thing as 'not spinning'? (What I mean is, you might say there is no such thing as 'not moving' (referring to linear velocity) since you need to provide a frame of reference to say what it isn't moving relative to.)

Finally, is it a valid question to ask 'how fast is the Sun rotating?' without providing (or implying) a frame of reference?

Posted in blog, Buzz