>Now, if the rubidium atom is moving, the light hitting it head on will be Doppler shifted into the wavelength that it absorbs, slowing it down, whereas the oth

>Now, if the rubidium atom is moving, the light hitting it head on will be Doppler shifted into the wavelength that it absorbs, slowing it down, whereas the other light wouldn't affect it Spooky. It's like having a Maxwell's demon for photons sitting on top of every atom!