Jun-Jie Wei

A distant radio signal travels toward us through gas, and the more gas it encounters, the more the signal is 'slowed down.' Astronomers use this to weigh the invisible envelope of our Galaxy: its halo. But if the halo is uneven, like a thick scarf draped over the shoulders, measurements in different directions will differ.

The night sky is occasionally pierced by short radio waves, like flashes from distant lighthouses. Most are barely noticeable, but sometimes a signal arrives so strong it outshines all others. It was just such a burst, named FRB 20250316A, that the Canadian radio telescope CHIME caught. It was so bright that astronomers decided to check just how likely such an event really is.

The Universe is expanding, but at what speed? Astronomers have been arguing for decades about the precise value of the Hubble constant. Two classic methods give slightly different results. Now there's a third — using mysterious radio bursts.

Half a century ago, Fritz Zwicky noticed that the visible matter in galaxy clusters was catastrophically insufficient to explain gravity.

The universe is like a vast invisible scaffold. We don't see it directly, but we know it's there: galaxies and clusters hold together thanks to it. This scaffold is dark matter. The most popular version says it is "cold," made of heavy, slow-moving particles.

A translator at a meeting keeps getting distracted by every rustle in the room, then suddenly dives into a long monologue by the speaker. That's exactly how the fast radio burst source FRB 20240114A behaves: in one hour, its pulses fire randomly, but over months they line up into a predictable drift.