Surf doesn't roll onto the shore as an even front. It comes in tongues of foam that merge and split apart. Magnetic fields inside materials behave much the same way: they breathe in waves, and until now nobody had seen them whole. Physicists at Princeton have built a device that catches these waves the way a radar catches planes, meaning it pins down not just the strength of the signal but also its direction, wavelength and speed.
Each defect is a tiny antenna, but on its own an antenna is weak. When there are many of them, they reinforce one another, and the picture comes out sharp. Previously such antennas listened to the noise at a single point or between two points, which means they heard only fragments of the melody. The new setup takes readings from the whole surface at once, and a computer turns them into a map of the waves, just as a radar turns echoes into a trajectory.
To see the shortest waves, the scientists burn away the excess defects with a laser, leaving a glowing spot 100 nanometers across. It's like squinting to make out a distant ship: the smaller the spot, the finer the detail it can resolve. That squint lets them peer past the limit set by ordinary optics.
Now physicists can listen to the magnetic surf in superconductors and magnets, where new phases of matter are born. Such waves used to be inferred only from indirect signs, and now they can be measured directly, from 100 nanometers up to micrometers. And if the surf changes, we'll be the first to see it.
The sensitive volume of the sensor can be squeezed down to 100 nanometers, which is 2.5 times smaller than the diffraction limit of light. It is like reading a newspaper through a keyhole, yet still seeing individual letters.
The idea of seeing the invisible waves of matter echoes the "psi-waves" of Frank Herbert's "Dune", where navigators sense the hidden currents of space.