Claims Frank at Frankly Curious:
If someone were to head to the farthest visible galaxy, it would take 13.3 billion years traveling at the speed of light to get there.
No, not entirely correct. If they were traveling at the speed of light, they’d get there instantly — from their perspective. This is why reasoning about things moving at relativistic speeds is so difficult.
You’ve heard I am sure the old standard tale about one of a pair of twins being sent away from earth at relativistic speeds (99% of the speed of light or whatever) while one remains behind? The twin who leaves earth spends five years away but when she returns 35 years have passed on earth. This is similar, except if you move actually at light speed,* time ceases passing for you altogether as relative to the outside universe, thus the length/distance to anywhere definitionally becomes zero. From your perspective, you’d arrive anywhere the same moment you left.
From the view of a photon, it is emitted and is instantly absorbed elsewhere, no matter how far away in its relativistic frame it appears to be from ours — even if it’s 13.3 billion light years away.
*Nothing with mass can move at the speed of light. Photons have no mass, so they can pull off this cool-ass trick.