The CMB is expected to appear isotropic i.e. the same in all directions. As we observe it, it isn’t – there’s a dipole contribution such that it’s hotter in one half of the sky and cooler in the other?

Question

The CMB is expected to appear isotropic i.e. the same in all directions. As we observe it, it isn’t – there’s a dipole contribution such that it’s hotter in one half of the sky and cooler in the other?

In: Physics

Answer 1

The CMB is in fact very even from all directions. Surprisingly so. But on the raw data, it will appear hotter in one direction and cooler in the other, because of red- and blue-shift caused by the motion of earth (and the galaxy) through local space.