Scientists Catch The Highest Energy Particles By Making Them Go Faster Than Light
“If you want to catch particles as they were before they ever reached Earth, you need to go to space to see them. But that’s expensive; the Fermi gamma-ray telescope (which detects individual high energy photons, not cosmic rays directly) cost approximately $690 million total. For less than half that cost, you can catch the particles that result from cosmic rays hitting the atmosphere in more than 100 locations across the globe, all because we understand the physics of particles that move faster-than-light through the atmosphere. More than that, the science prospects include understanding the origin of relativistic cosmic particles, the acceleration mechanisms around neutron stars and black holes and might even improve astrophysical searches for dark matter.”
It’s true that nothing can move faster than the speed of light, but only if you’re in a vacuum. Once you’re in a material, like water, glass, or even the atmosphere, all you need to do is make your particles move faster than the speed of light in that medium and all the rules change. By moving faster than light, you force these relativistic particles to emit photons in all directions – Cherenkov radiation – which forces them to slow down. This Cherenkov radiation can be detected by an observatory designed to do exactly this! Since very high energy cosmic rays strike our world and move through the atmosphere, we can detect these Cherenkov photons as their signature, and work to reconstruct where they came from and what caused them.