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Karl24

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- TL;DR Summary
- What's the experience of travel like for a photon?

We know that as speed increases, time slows, and at the speed of light time apparently ceases. Imagine a hypothetical hitch-hiker sitting on a photon and speeding through the universe at -- well, the speed of light. If time has stopped for him (her?), what is his experience of his journey? Are all locations and all times along his path of travel an instantaneous 'everywhere' and 'everywhen' for him?

And a subsidiary question: since the universe is finite, presumably there is eventually a frontier between space and no-space. Depending on where his photon was emitted, it could be that the hitch-hiker will never reach that frontier, because the accumulating expansion of space itself may exceed his rate of travel. But assuming the journey began somewhere already near the edge of space and the frontier was reachable, what happens when he reaches it? Does his mere presence extend the universe, and he continues merrily on his way? Or does he bounce back? Or cease to exist? Just wondering, before I book my ride!

And a subsidiary question: since the universe is finite, presumably there is eventually a frontier between space and no-space. Depending on where his photon was emitted, it could be that the hitch-hiker will never reach that frontier, because the accumulating expansion of space itself may exceed his rate of travel. But assuming the journey began somewhere already near the edge of space and the frontier was reachable, what happens when he reaches it? Does his mere presence extend the universe, and he continues merrily on his way? Or does he bounce back? Or cease to exist? Just wondering, before I book my ride!