We've all heard of sonic booms, which occur when the shock waves produced by an object traveling faster than the speed of sound accumulate to produce a giant pressure wave, but what about "photonic" booms? Researchers have just shown that indeed, light exhibits the same effect, and they used a camera that records 100,000,000,000 frames per second to show it.
Creating a photonic boom takes a bit of clever physics. We know that nothing can travel faster than light, but light itself can slow down depending on the medium in which it's traveling. To do this, scientists created a narrow tunnel surrounded by plates of silicone rubber and aluminum oxide powder. They then filled the tunnel with the gas from subliminating dry ice and fired a laser down it. When the laser pulses hit the bits of dry ice, it scattered into the plates, which had a higher refractive index, causing it to slow down and waves to accumulate: a photonic Mach cone. You can see the cone below.
Beyond this experiment, researchers are particularly excited about this imaging technique (called a "streak camera") as it applies to biomedical research. So fast is the camera that it can capture the firing of neurons, allowing researchers to potentially visualize neural networks in realtime, opening a new frontier of brain research.
Images via Science Advances, used under Creative Commons.