I've see some velocities such as that of the Sun quoted as "relative to the cosmic microwave background"?

How is this different to measuring velocities relative to that old, discredited idea, the ether?

  • $\begingroup$ Well, that is just about the most mind-blowing thing I've read in a while. $\endgroup$ – spraff Jan 26 '15 at 15:07
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    $\begingroup$ @spraff But isn't learning physics always mindblowing? :P $\endgroup$ – Jim Jan 26 '15 at 15:24