"We were very much impressed. At the same time, we were afraid." Inside the quest to map the universe with mysterious bursts of radio energy When our universe was less than half as old as it is today, a burst of energy that could cook a sun's worth of popcorn shot out from somewhere amid a compact group of galaxies. Some 8 billion years later, radio waves from that burst reached Earth and were captured by a sophisticated low-frequency radio telescope in the Australian outback. The signal, which arrived in June 2022, and lasted for under half a millisecond, is one of a growing class of mysterious radio signals called fast radio bursts. In the last 10 years, astronomers have picked up nearly 5,000 of them.