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As I mentioned before, I’m branching out a bit and writing some listicles for Symmetry Magazine this year. The first covered gravity, and the second covers… light!

Eight things you might not know about light

Light is all around us, but how much do you really know about the photons speeding past you?

For Symmetry Magazine:

1. Photons can produce shock waves in water or air, similar to sonic booms.

Nothing can travel faster than the speed of light in a vacuum. However, light slows down in air, water, glass and other materials as photons interact with atoms, which has some interesting consequences.

The highest-energy gamma rays from space hit Earth’s atmosphere moving faster than the speed of light in air. These photons produce shock waves in the air, much like a sonic boom, but the effect is to make more photons instead of sound. Observatories like VERITAS in Arizona look for those secondary photons, which are known as Cherenkov radiation. Nuclear reactors also exhibit Cherenkov light in the water surrounding the nuclear fuel. [Read the rest at Symmetry Magazine…]