The Expanse

Light, i.e. photons, travel at the maximum speed we know of in the universe.

Einstein’s e=mc^2^ shows us that when “the speed of light” is achieved travel forward or backward on the time line is possible.

Therefore a photon exists only for an instantaneous amount of time, regardless of how far it travels, from the perspective of the photon.

The light that the JWST captures from 12.3 billion years ago is that old to us. To the photon, however, it was created in that stellar object and then immediately crashed into the JWST sensor.

The membrane of time is what we perceive not what the photon experiences.

Edit: How does light actually work?

It is a bit cryptic that phrasing. I think they are trying to describe a null/light geodesic, that is the path light follows in space time, in a geometric way. Or maybe they are comparing to light to a vibration that has to travel through a membrane? I do believe they make it clearer later what they mean in the context of superluminal communication/phenomena. The point is something like this: if you take a stick and have a point a and b in the sand, draw a line between a and b as fast as you can, it will always take some time larger than zero. This speed limit is the speed of light. Now if you instead drop the stick so it goes from a to b, you have managed to mark the path a to b faster than drawing it. Sending light, you drawing, will be bound by some speed, their communication, the equivalent of just dropping the stick, will not.