Xue-Feng Wu

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 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.

In a distant galaxy, at a distance that light takes 11 billion years to cross, something flashed. The Einstein Probe X-ray telescope caught a brief, needle-prick-like burst: it lasted only a few dozen seconds.

A distant lighthouse flashes for an instant brighter than an entire galaxy. This is a fast radio burst — a mysterious signal from deep space. Some repeat, and astronomers have noticed a peculiarity: these bursts show rapid changes in polarization — a property indicating how the radio wave is twisted in space.

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.