A brave new world.

SR replaced Galilean transformations by Lorentz transformations, the ones that include the Lorentz factor that warps space and time for moving objects. Then, Einstein should have reformulated the question he asked when young, the other way around: How does light experience our universe?

Now, we'll see reality through the eyes of a photon. A very interesting experience:

• Always at c speed: Photons are massless quanta of light, so they always move at c in vacuum.
• No space or distance: Going at c, photons experience maximum length contraction. So much contraction they have no concept of distance. All the 3D paths we think they describe wandering the universe are compressed into a single point for them. The evolution of the material world defines those “paths”, yet photons feel just an emission/absorption point.
• No time or duration: They experience maximum time dilation. So much dilation they don't know what time is. Their internal clock is so slow that any interval we could imagine would be instantaneous for them. Imagine a photon being emitted when the universe began, being absorbed whenever the universe ends. All those billion years would be just an instant for that photon.
• No evolution: Thus, photons can't evolve while traversing vacuum at c, because they feel everything as a single interaction. The vast distances we see in our universe don't exist for photons “in flight”. For them, fields and field lines describe how emission and detection points connect together. They feel emission point “glued” to detection by the field lines that lie on free space, so any medium in which they don't travel at c would join with the next seamlessly.

This is the strange way a photon sees the universe while traversing vacuum. They feel leaving emission and arriving at detection at the same time. c is the ultimate spacetime compression factor, as nothing can experience anything faster than instantly, no matter what others could say about its speed.