The radio flash FRB 20240304B is a message from the past, a brief signal on invisible waves. Like a letter passing through hundreds of hands, it absorbed traces of everything it encountered during its 11-billion-year journey: gas, magnetic fields, entire galaxy clusters. Over that time, the expansion of the universe stretched space, and the signal became a key to the history of galaxy growth. Long before the discoveries of Edwin Hubble and Georges Lemaître, who proved expansion, it was already racing through the void. The James Webb Space Telescope found its starting point — a small, clumpy galaxy bustling with star formation. So these bursts flashed even when the universe was very young. But the biggest surprise was the magnetic fields: they turned out to be tangled, like a mess of old phone cords, not smooth lines. Such messages from the outskirts of the cosmos help us reconstruct the story from the Big Bang to the present day.
The energy of such a flash in a millisecond rivals that of the Sun over several days, even though its source could fit within a small city.