Throw a stone into a pond and ripples spread across the water. Magnetic fields inside materials also ripple in waves, but no one has ever seen these waves in full. Scientists at Princeton have built a device that catches all of them at once for the first time.
Previously, such antennas listened at only one point, which means they heard just a fragment of the melody. The new setup takes readings from the entire surface at once, and a computer turns them into a map of the waves, the way radar turns an echo into an airplane's trajectory. To see the shortest waves, the scientists leave a glowing spot 100 nanometers across, which is a thousand times thinner than a human hair.
Now physicists can listen to the magnetic surf in superconductors and magnets, where new properties of matter are born. Previously such waves were only guessed at, but now they can be measured directly. And if the surf changes, we will 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.