Measuring our velocity from fluctuations in number counts

Understand

Our velocity relative to the cosmic microwave background (CMB) generates a dipole from the CMB monopole, which was accurately measured by COBE.

• The relative velocity also modulates and aberrates the CMB fluctuations, generating a small signature of statistical isotropy violation in the covariance matrix.
• This signature was first measured by Planck 2013.
• Galaxy surveys are similarly affected by a Doppler boost.