House13Games t1_jco64y1 wrote on March 18, 2023 at 7:18 AM

Reply to comment by DudeWithAnAxeToGrind in Where do photons go if they've been emitted but are destined to never be absorbed, and would these photons traveling ad infinitum define the edge of the universe (even if space itself were still larger)? by mysteryofthefieryeye

But where do they go?

DudeWithAnAxeToGrind t1_jcqwb8m wrote on March 18, 2023 at 9:32 PM

Are you trolling me here? Assuming you are not, the above answers exactly where they'll go. It'll simply take them forever to get there, because space they have to travel through is itself expanding.

To make an analogy, imagine an ant on the surface of a balloon trying to get from the bottom to the top of the balloon. Imagine you can just keep inflating this balloon indefinitely, making it bigger and bigger. If you are inflating balloon fast enough so that it increases in size faster than ant can move over its surface, the ant will make a progress in its journey, but it will never be able to reach the top of the balloon. If ant can keep going infinitely, there's a spot on the balloon it will eventually reach after infinite amount of time has passed.

This is what happens to a photon traveling through Universe. The universe is expanding, and the far regions of space are receding from this photon faster than the photon can travel through space.