Haitao Xu

When water churns behind a boat, the energy of motion is converted into heat through a cascade of vortices. Measuring how quickly this happens directly is difficult: you'd need to track all the vortices at once. So scientists use a simplification: they look at only one velocity component at a single point.

A massive star ends its life in a spectacular collapse: the core compresses into a neutron star or a black hole, while the outer layers fly off in a dazzling supernova.