Measuring the CMB Polarization with the Atacama Cosmology Telescope.
We have learned a great deal about the universe from measurements ofthe cosmic microwave background (CMB). Most of what we have learned so far has been based on the temperature anisotropy combined with measurements of the polarization at angular scales of roughly 10 degrees. We are entering a new era in which the polarization of the CMB will be measured to high accuracy especially at degree angular scales and smaller. With the polarization we can, for example, measure or limit the presence of gravitational radiation from the early universe and determine the sum of the neutrino masses. The polarization will also give us a new way to determine the cosmological parameters. We review recent results on the CMB polarization with anemphasis on those from the Atacama Cosmology Telescope (ACT) project.