An antiproton is a proton moving backward in time. I know you said photon, but presumably the same applies
Nothing will come of nothing.
-King Lear Act I, Scene I
I know this doesn't add to the discussion. I just wanted to look all cultured and stuff.
Oh dear oh dear oh dear, as someone's avatar might once have said ....
Time isn't really that mysterious. All of spacetime includes all of history, past and present.
It might seem like a minor thing but with chaos theory and the butterfly effect over the years that tiny tiny change would result in a slightly different universe.
..because when we move through the other dimensions, we're always popping in and out or spacetime and cannot be observed other than at the starting point and the destination....If, however, time is to be treated as a dimension (direction) it would be possible to step outside of this spacetime into time and back into spacetime again.
If time were reversed, energy would tend toward lower entropy. Disorder would move to order, which as far as we know, is breaking one of the most fundamental laws of physics.
If you require to move. However travelling from point A to point Q without passing through the rest of the alphabet between can’t be rejected outright, even in spacial terms. There is some (not totally conclusive yet) evidence they are doing it in Geneva, already (no, nothing to do with CERN). No, I do not understand it yet.to move from one point in time to another, we must pass through the intervening points.
The term dimension has a specific mathematical meaning: "In mathematics the dimension of a space is roughly defined as the minimum number of coordinates needed to specify every point within it". A minimum of four coordinates are needed to specify every event in spacetime, so spacetime is a four-dimensional space. The fact one coordinate is different from the other three does not make it any less of a coordinate.
However time is fundamentally different to space as can be seen from the Minkowski metric: ds²=-c²dt²+dx²+dy²+dz². Time is still a dimension, but that minus sign definitely singles it out.
Einstein published his general relativity and Minkowski subsequently formalized the idea of four dimension spactime...Einstein adopted it...And physicsts spent the next twenty years slowly discovering what general relativity really means...