The single change
Start from two things almost nobody argues with.
Time never started. Pick any moment you like, and something was always happening right before it, because a moment with nothing at all before it is a moment we would have to explain using something outside of physics, and there is no outside of physics. So let time stretch back forever, with no first tick. And let space go on forever too, with no wall and no far edge, because the second you put up a wall you have to answer two questions no equation can answer, what is on the other side of it, and what is holding it there. Time with no beginning. Space with no edge. These are not wild ideas. They are the calm, ordinary thing you are left with once you stop sneaking in a beginning or a border you cannot back up.
Now let us just be honest about what Einstein's rules, the same relativity we already trust, actually say inside a Universe like that. If space goes on forever and is already full of stuff, then there is stuff everywhere, at every size. And here is the beautiful part, I did not have to arrange any of it. Gravity does the arranging all by itself. Einstein's equations have no favorite size built into them, so gravity plays the very same game at every level. Bits of matter pull together into clumps, clumps gather into bigger clumps, those ride inside bigger ones still, stars into systems, systems into galaxies, galaxies into clusters, clusters into superclusters, follow the leader all the way up, with no smallest rung and no biggest rung the equations care about.
And each one of those clumps, at every level, is a little crowd of things all drifting along together at about the same speed, sharing their own sense of time, tucked inside the bigger crowd above them. That nested, drifting, self made crowd is what I mean by a pocket of spacetime. I am not inventing it. Gravity and Einstein's own rules hand it to us for free, over and over, at every scale, forever. So the Universe is not smooth and empty. It is full of countless pockets, all of them quietly drifting. Some of them are strangers to one another, born of entirely separate events, sharing no past at all. But others are siblings, thrown off together in the same long run of collisions, and those carry a shared history, the same origin, the same spin, the same slow story unfolding side by side. A whole family born of one shared overlap where two vast pockets once met, and countless such families, spread across a Universe that never began.
And here is the thing almost everyone skips right over. Einstein never said two of those pockets cannot rush toward each other faster than light. His famous speed limit is about one exact thing, a nearby push speeding up a nearby object, and there it is rock solid, nobody argues. But it says nothing about how fast two things can close in on each other when they were never in the same pocket to begin with, and were never pushed together by anything nearby. We already live with this. Right now, tonight, galaxies far enough away are moving away from us faster than light, and nobody calls it cheating. But watch carefully what that fact is and is not doing here. That kind of moving apart happens inside one pocket, one stack of space stretching out, all of it sharing a single origin. It does not cause anything, and it does not tell you how a universe gets started. I only mention it for one reason, to show that two things with no shared beginning are already allowed to close in on each other faster than light, and we have already seen it. That is all it buys us. Not one bit more.
So take the honest starting ideas and follow them all the way to the one place that moving apart never covers. In a Universe with no beginning, no edge, and stuff everywhere, separate pockets drifting at every speed, some of them closing faster than light, will not just drift past each other forever. Sooner or later they meet. Not once, but over and over, forever. And two pockets meeting is a completely different event from the quiet spreading out going on inside either one. When two immense pockets finally overlap faster than light, that shared region of spacetime does not flash once and fall quiet. It becomes the site of a whole succession of collisions, a cascade that tears through the overlap stage after stage, everything in it thermalizing into a scorching, crushing hot soup of matter, the very fire we mistook for the beginning of everything.
But it was never the beginning. It was one shared overlap and the succession of collisions that poured out of it, a run of events in a Universe that has always been here and always will be. That is the whole change. I did not add a new push, a new force, or a new particle. I just refused to assume a beginning, and then I let Einstein's own rules tell me what has to happen when two immense pockets of a forever Universe finally choose to share the same patch of spacetime.
