Starts With A Bang

How do photons experience time? (Synopsis)

The Sun and Earth from the ISS. While Earth's light is less than a second old, the Sun's is more than eight minutes old. Image credit: NASA / International Space Station.

“Everyone has his dream; I would like to live till dawn, but I know I have less than three hours left. It will be night, but no matter. Dying is simple. It does not take daylight. So be it: I will die by starlight.” –Victor Hugo

Whether you’re at rest or in motion, you can be confident that — from your point of view — the laws of physics will behave exactly the same no matter how quickly you’re moving. You can move slowly, quickly or not at all, up to the limits that the Universe imposes on you: the speed of light.

Light, in a vacuum, always appears to move at the same speed — the speed of light — regardless of the observer’s velocity. Image credit: pixabay user Melmak.

But what if you’re actually a photon? What if you don’t move near the speed of light, but at the speed of light? As it turns out, the way any massless particle experiences time, distance, and the Universe in general is entirely counterintuitive, and there’s nothing in our common experience that matches up.

A relativistic journey toward the constellation of Orion. Image credit: Alexis Brandeker, via http://math.ucr.edu/home/baez/physics/Relativity/SR/Spaceship/spaceship.html. StarStrider, a relativistic 3D planetarium program by FMJ-Software, was used to produce the Orion illustrations.

It’s a relatively interesting story if you want to think about it deeply, and yet once you arrive at the answer, it couldn’t be any simpler.