Fredagskollokvium: Polarization of the Cosmic Microwave Background, current status and future prospects

Detecting B-modes due to primordial gravitational waves in the polarization of the Cosmic Microwave Background (CMB) is one of the greatest goals of modern observational cosmology. Many experiments have been designed to detect this weak signal, and upper limits are improving year by year. In fact, while B-modes have now been clearly observed, these are not of primordial origin, but rather induced by late time effects. At large scales, the signal is most probably dominated by the galactic dust, whereas at small scale, it is due to gravitational lensing.  
In this talk, I will give a general introduction to the physics of the CMB and focus on its polarization. I will also show some recent observational highlights, and introduce our work at ITA on the SPIDER balloon-borne experiment.