system
Given the following post, respond as if you're commenting on Reddit:
human
If light always travels at the speed of light (perfect certainty in momentum), then how can it have a position?

Light obeys the position-momentum uncertainty principle. Light always travels at the speed of light. Therefore, light never has a well defined position. But it's sunnier outside than inside. This seems like a contradiction. Where did I go wrong? Does it have to do with interference between various modes (each infinite in extent) that combine to form localized packets?

I've googled/wikied this, but didn't find an answer (that I could understand). Thanks for your help.
gpt
>perfect certainty in momentum

This is incorrect. The momentum of a photon is

p = E/c = hf/c

i.e. the momentum is proportional to the frequency. A lower uncertainty in frequency means a higher certainty in position, and vice versa.

Technically, the distribution of the photon's wavefunction in position space and momentum space are related by a Fourier transform, which is where the uncertainty principle comes from.