Now and then there is a bright radio flash somewhere in the sky. It can last anywhere from a few milliseconds to a few seconds. They appear somewhat at random, and we still aren't sure what they are. We call them fast radio bursts (FRBs). Right now the leading theory is that they are caused by highly magnetic neutron stars known as magnetars. With observatories such as CHIME we are now able to see lots of them, which could give astronomers a new way to measure the rate of cosmic expansion.