### Mass as the Curvature of Space-Time

After noticing in my previous post that the highest energy photon would be the smallest black hole, I continued wondering about the smallest possible mass.

And after dancing around the obvious non-starter of a no energy photon, because zero energy would be equivalent to infinite wavelength, it occurred that it could be descriptive of the boundary of the universe, presuming the universe looks like a big balloon.

That is, like a latitude going infinitely around the earth but still being finite, a zero mass photon could describe a universal latitude (or longitude) around the still finite universe.

But, could a zero mass photon have a direction? Or be polarized? I’d guess not, so it probably can’t be a real thing.

It does suggest limits though, for the universe, and for the least possible mass.