On the subject of photon experience...

“The photon, because it travels at the speed of light, the time is just stretched out and it’s nothing. So right from its creation, in some particle decay or something, this photon goes out to infinity and it experiences zero time. So, it’s not bored in the sense of—forget about whether it actually has feelings or not—it doesn’t experience the passage of time. Now this is the sort of thing I used to play around with and thinking about gravitational radiation and how you put boundaries on spacetimes and so on. And it was a useful way to think that this boundary is something you could imagine going through, and if you were a massless thing when you hit that boundary you say, ‘well, where the hell am I?,’ you see. There’s got to be something on the other side, you might think”—Sir Roger Penrose on Sean Carroll’s Mindscape podcast, episode 28, Jan. 7, 2019, time 46:26