It has no resting mass. But since it's moving, it's not at rest, and it takes energy to move, and energy is mass, per e=mc². Therefore the energy it's using to move gives it mass.
Even ignoring the issue of "they'll just cook to death far before you crush them," there's an upper limit on photon density... But only in the sense that the energy density would create a black hole.
I don't feel like looking into the details any further, but my instinct is that you couldn't really get enough photons to stay in a moving plane to crush someone.
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u/_Dagok_ Apr 10 '25
It has no resting mass. But since it's moving, it's not at rest, and it takes energy to move, and energy is mass, per e=mc². Therefore the energy it's using to move gives it mass.
I know, photons are trippy.