[Leftium]

If something blocks the photon, that was "agreed" upon before the photon was created.

A photon travels between an electron that emits it and an electron that absorbs it. These two electrons must agree on the photon transfer beforehand. This has some strange implications:

- When you see a star at night, it's because photons from the distant star hit your eyes.

- These photons started traveling billions of years ago, when neither you nor your eyes existed yet.

- Yet the electrons in your eyes and the electrons in the star (which may no longer even exist) must have agreed to transfer these photons.

- From the photon's perspective, it traveled instantaneously from the star to your eye; it traveled through billions of years of time!

Source: https://www.youtube.com/watch?v=bAedYtUredI&t=2630s

[fnordpiglet]

While I think you can conceive of it this way I don’t think it’s precisely right. Photons don’t experience time at all and never exist from their own perspective as they have no mass and always travel at the speed of light in all reference frames. However causality at speeds less than the speed of light is a real thing and due to special relativity we can interact with photons with a different simultaneity. This is partially because they can’t experience the events of the universe going less than the speed of light due to the fact they absorb rather than decelerate.

This doesn’t mean there’s some cross time agreement between particles mediated by the photon because the reference frame of those particles are different than the photons and are necessarily slower than the speed of light.