In science, the question of what light is reduces to what it does, but what it does isn’t physically possible. Even after centuries of study, physics still can’t explain why light:
1. Doesn’t fade. All physical waves fade over time, by the second law of thermodynamics, but light doesn’t. A photon that took a million years to hit a screen gives the same result as one just made.
2. Has a constant speed. The speed of a wave depends on the medium it travels through, but light travels at a constant speed in the nothing of space, for no physical reason.
3. Is a wave and a particle. Waves aren’t particles, nor are particles waves, but light travels like a wave then arrives like a particle.
4. Always finds the fastest path. A particle can’t know, in advance, the fastest path to any destination, but light always finds that path.
5. Chooses its path after it arrives. A particle can’t choose the path it takes to a destination after it arrives, but light can do just that.
6. Can reveal an object it didn’t physically touch. In a purely physical world, it is impossible to detect an object without touching it, but light can do exactly that.
7. Can vibrate outside space. Light vibrates, but does so in a dimension outside our space.
Most scientists assume that light is physical, but physical causes can’t explain it. For example, wave-particle duality lets light be both a wave and a particle, but nothing physical can do that. A water wave can’t arrive at a point like a particle, but light does. A particle can’t take many paths at once like a wave, but light does. Physical waves don’t act like particles, and particles don’t act like waves, so how can light be both? Surely science can decide if light is a particle or a wave?