Gamma ray bursts are flashes of gamma rays that hit our planet quite regularly. They can last for fractions of seconds or minutes. They can be detected from enormous cosmic distances.
Back in April 2010, a satellite detected a 10 second GRB burst. That’s ten seconds of gamma rays that we now know travelled 13 .7 billion years to reach us from a supernova in a galaxy that occurred about 630 million years after the Big Bang.
