# Can the CMB be used as an absolute reference frame?

22 April 2011

## Question

Hi Chris, great show , Im hooked. I have a question:

The cosmic microwave background (CMB) shows a dipole distribution which is normally subtracted from the data to reveal the underlying "wrinkles" that appear in the public relations images (George Smoot´s "face of god"). This dipole distribution means that one side of the sky is slightly hotter than the other and this is usually described as being due to the doppler shifts in the CMB due to the solar systems motion through space. Surely this implies that the CMB provides an absolute frame of reference in space against which velocities can be measured? Einstein showed us that all velocities are relative. How can this apparent paradox be explained?

Cheers
Simon

Simon Tulloch