A fast radio burst (FRB) is like a race: lower frequencies, like sluggish rookies, lag behind the swift high frequencies. As they dash through a charged cosmic 'crowd' (free electrons), they lose pace, and the longer the distance, the wider the gap. This difference – the dispersion measure – was first noticed back in the 1930s by Karl Jansky, the father of radio astronomy, while Jocelyn Bell Burnell later linked such pulses to neutron stars.

Astronomers examined 90 bursts and found: the farther the galaxy (and thus younger, per Edwin Hubble's law), the more transparent it is to radio waves – meaning fewer electrons. Over time, galaxies accumulate ionized gas, and the signal delay grows. Astonishingly, this growth exactly mirrors the tempo of ancient star formation: stellar 'factories' churning out stars also spray charged particles into space. Later, those same regions breed magnetars, which in turn spawn FRBs. Thus a single burst links the birth and death of stars with the invisible evolution of galaxies. This data is crucial for untangling cosmic distances and the distribution of dark matter.