My son wants to know how we can perceive light and it not take up any space at the same time.
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This is a very good question that I’ve never considered before. It really comes down to quantum mechanics and the wave particle duality. Light is simply a disturbance in the electromagnetic field, which permeates the entire universe and therefore all photons are everywhere at once until you observe it, thus collapsing the wave function (like Schrodinger’s cat). Of course the nature of the wave means there’s a location where the photon most likely is, and that can become quite a large area, but can always be collapsed down again by making an observation. However for a given photon, the probability that it is at an arbitrary point is never 0, no matter how infinitely small that probability is. The only way to get that probability to 0, would be to have a barrier it takes infinite energy to cross over, or else quantum tunnelling could take it through. Keep in mind, these non zero probabilities are really really close to 0. Small enough that a photon existing outside of where it is very likely to have been found probably hasn’t happened in the history of the universe. Acknowledging the possibility is more of a thought experiment than anything.
To look more into this, consider the double slit experiment with a single photon (also called single photon interference).
Schrodinger’s cat, but you’ve probably already heard of this one, but you can also look into the schrodinger wave equation and wave collapse if you want to get a little more advanced.
Quantum tunneling, which is basically proof that the peak of the wave equation isn’t necessarily where the particle is. And we know it exists because we’ve observed it and everything from basic chemistry to stars wouldn’t work if it didn’t exist. It was actually discovered because the wave equation predicted it.
This is some high level quantum mechanics shit and someone could probably get their PhD writing about the size of a photon. Sorry I couldn’t quite ELI5.
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