I tried to pick the most appropriate subforum, feel free to move this if there's a better one! I'm not a physicist, but I had an epiphany recently that I've never see anywhere else, and it seems so incredibly obvious that I think it's either the accepted theory of time directionality, or I'm missing something huge. According to Einstein we have a thing called spacetime which is 4 dimensional. In much the same way travelling North West will slow down progress toward the North (given the same travel speed), travelling through space slows down your progress through time proportional to how much of your motion you're diverting into motion through space instead of motion through time. So the first part is that we're living in this 4 dimension spacetime stuff, and we can travel along any of the 4 dimensions. We'll come back to that. Consider a particle flying away from a big explosion, like a chunk of MacGuffinium. Just for the sake of argument, say this chunk of stuff can consider its situation. It notices as it's living its life that it can move pretty freely along a 2D plane, but that if it "stops" trying to move, it's still moving very quickly in a particular, outward direction (we know the direction is away from the explosion, but the chunk doesn't). Whenever he moves from side to side he can measure that he's going infinitesimally more slowly in that outward direction. He can't seem to go back in that direction--the force is too great by far--but he can make (barely) measurable impact on the velocity by moving through the 2 dimensions he's free to move around. So back to spacetime. If we live in a universe that began with an enormous explosion into a 4 dimensional substrate, doesn't it make sense to consider that time is the "outward" direction of that explosion, and that we are travelling along that axis, in this direction, because of the force of that explosion? Wouldn't that explain why we can move relatively freely in the other 3 dimensions, but not so much in the 4th dimension? That would explain why time is moving the direction it seems to be moving, even though the equations don't demand it, and it explains why we can't really go back or forward on that dimension (extreme velocity from the explosion, relative to our puniness). It may also explain why we perceive time as qualitatively different than the other 3 dimensions: we're travelling super duper fast in that dimension, so we're experiencing it it a really distorted, compressed way in comparison to the other 3 dimensions. So... is this an accepted thing, am I missing something huge, or did I just blow open an old problem with an obvious explanation?