The CMB Dipole: Eppur Si Muove
  The largest temperature anisotropy in the cosmic microwave background (CMB)
is the dipole. The simplest interpretation of the dipole is that it is due to
our motion with respect to the rest frame of the CMB. As well as creating the
$\ell$=1 mode of the CMB sky, this motion affects all astrophysical
observations by modulating and aberrating sources across the sky. It can be
seen in galaxy clustering, and in principle its time derivative through a
dipole-shaped acceleration pattern in quasar positions. Additionally, the
dipole modulates the CMB temperature anisotropies with the same frequency
dependence as the thermal Sunyaev-Zeldovich (tSZ) effect and so these modulated
CMB anisotropies can be extracted from the tSZ maps produced by Planck.
Unfortunately, this measurement cannot determine if the dipole is due to our
motion, but it does provide an independent measure of the dipole and a
validation of the y maps. This measurement, and a description of the
first-order terms of the CMB dipole, are outlined here.
