A neutron star is a spinning top with the mass of the Sun, crushed to the size of a city. It's born in the fire of a supernova and usually only slows its spin. But sometimes, for no apparent reason, it suddenly speeds up — such a jerk is called a glitch. Many neutron stars become pulsars: they beam out rigid radio pulses like cosmic lighthouses. Their discovery in 1967 by Jocelyn Bell Burnell gave the first clue to these extreme objects.

Inside the star, matter enters a frictionless state — superfluidity. In the lab, its role was played by porous aerogel soaked with superfluid helium. It turned out that in the outer layer, akin to a crust, tiny whirlpools (quantum vortices) break loose and slide when the spin is too fast. But in the dense core, they stick tight to the pores, and the slightest change triggers an avalanche of new vortices. Both processes whip the star forward, like a gust of wind spinning a top. A surprise: glitches aren't a nuisance, but a gift. By tracking these jerks, like seismic waves, we can peer into the star's interior, beyond the reach of any telescope. The concept of neutron stars was laid down by Fritz Zwicky and the calculations of Subrahmanyan Chandrasekhar, and now the lab analog turns every glitch into a session of cosmic tomography.