There’s also no reason to believe that the big bang happened at one “point”. I believe that the universe (and therefore the big bang) are infinite.
Everything is relative, so something infinite can still expand: since there’s no absolute speed, galaxies can move away from each other everywhere, at all times.
The geometry of explosions says otherwise. An explosion implies expansion outward from a center. If every point in space exploded at once, there would be nowhere for anything to expand, thus creating compressive forces.
You would have to zoom out really really far, beyond the boundaries of the explosion, to see the forces expanding beyond that. And at that point, it’s just the Big Bang, only on a larger scale, and with the singularity being really a vast space seen from a much larger scale.
To illustrate, one speck of C4 explodes in an outward direction, but put a million specks of C4 together into a continuous block, and it still explodes in an outward direction. It’s not a million tiny explosions all taking place within the space of the block.
Metaphors like this at helpful for approaching understanding, but you can’t extrapolate from them. There was no 3D space in which the big bang occurred, “nothing” is not the same as “a patch of vacuum in spacetime”. An explosion doesn’t start as dimensionless singularity, it starts with the matter that explodes. And so on.
I think it’s a logical necessity for the universe to be infinite, at least spatially. In order to be finite, it needs to have something outside of it to set a boundary containing it. But if that were the case, then there must be something beyond it, which means the space contained within that boundary would not be the entirety of the universe.
Whether that space beyond is filled with anything or simply empty until stuff expands into it is a different question. And whether there were multiple other big bangs incomprehensibly far away from the observable universe is another question too. But neither of those possibilities implies that the big bang would have happened at every point in space simultaneously.
Another reason that possibility is untenable is because of heat dissipation. If every point in space exploded simultaneously, not only would there be nowhere for the force to go, but there would be nowhere for the heat to dissipate too, either. The heat would be uniformly distributed throughout space, offering no possibility of cooling down and coalescing into denser states of matter. The pressure would also be infinite, with no gradient. Everything would simply be an ocean of gammawaves, with no room for expansion.
The idea is that the big bang started as a singularity, where everything had the same position as far as our 3d space is concerned, and then the difference in position arose as a consequence of it. Maybe space (as we know it) didn’t exist before, maybe it did but collapsed, or maybe there was “other” space but this space we’re in popped into existence. Same thing with time and perhaps some other dimensions.
So it did happen everywhere (where everywhere is just everywhere inside this universe), but it was a single point at that moment.
Though I suspect it was inside another universe and that our big bang singularity was just another black hole forming in that universe and we’re seeing the mystery of what happens beyond the event horizon when gravity overpowers all other forces. Our familiar forces could just be the next set of rules physics for small things (from the perspective of the parent universe) after gravity overcomes the dominant ones in that universe. Which could mean that all black holes are tunnels to other universes (that we can’t visit but the matter that makes us could, though it would probably be something else once it did, like an entire galaxy cluster).
Then the CMB might just be light that entered our universe from the parent one, redshifted like crazy (plus other optical gravitational effects, like any light that enters will appear brighter in one direction but coming from all directions to some extent).
There’s also no reason to believe that the big bang happened at one “point”. I believe that the universe (and therefore the big bang) are infinite.
Everything is relative, so something infinite can still expand: since there’s no absolute speed, galaxies can move away from each other everywhere, at all times.
The geometry of explosions says otherwise. An explosion implies expansion outward from a center. If every point in space exploded at once, there would be nowhere for anything to expand, thus creating compressive forces.
You would have to zoom out really really far, beyond the boundaries of the explosion, to see the forces expanding beyond that. And at that point, it’s just the Big Bang, only on a larger scale, and with the singularity being really a vast space seen from a much larger scale.
To illustrate, one speck of C4 explodes in an outward direction, but put a million specks of C4 together into a continuous block, and it still explodes in an outward direction. It’s not a million tiny explosions all taking place within the space of the block.
No, there’s no center and no edge, the big bang happened everywhere at once. The universe might be finite, but only in the sense that it’s looping back on itself, not in the sense that it can possibly be a sphere (which has both center and edge). So your mental model of an explosion in 3D space doesn’t fit: https://nasaspacenews.com/2025/10/is-the-universe-infinite-new-evidence-challenges-our-cosmic-understanding/
Metaphors like this at helpful for approaching understanding, but you can’t extrapolate from them. There was no 3D space in which the big bang occurred, “nothing” is not the same as “a patch of vacuum in spacetime”. An explosion doesn’t start as dimensionless singularity, it starts with the matter that explodes. And so on.
I think it’s a logical necessity for the universe to be infinite, at least spatially. In order to be finite, it needs to have something outside of it to set a boundary containing it. But if that were the case, then there must be something beyond it, which means the space contained within that boundary would not be the entirety of the universe.
Whether that space beyond is filled with anything or simply empty until stuff expands into it is a different question. And whether there were multiple other big bangs incomprehensibly far away from the observable universe is another question too. But neither of those possibilities implies that the big bang would have happened at every point in space simultaneously.
Another reason that possibility is untenable is because of heat dissipation. If every point in space exploded simultaneously, not only would there be nowhere for the force to go, but there would be nowhere for the heat to dissipate too, either. The heat would be uniformly distributed throughout space, offering no possibility of cooling down and coalescing into denser states of matter. The pressure would also be infinite, with no gradient. Everything would simply be an ocean of gammawaves, with no room for expansion.
The idea is that the big bang started as a singularity, where everything had the same position as far as our 3d space is concerned, and then the difference in position arose as a consequence of it. Maybe space (as we know it) didn’t exist before, maybe it did but collapsed, or maybe there was “other” space but this space we’re in popped into existence. Same thing with time and perhaps some other dimensions.
So it did happen everywhere (where everywhere is just everywhere inside this universe), but it was a single point at that moment.
Though I suspect it was inside another universe and that our big bang singularity was just another black hole forming in that universe and we’re seeing the mystery of what happens beyond the event horizon when gravity overpowers all other forces. Our familiar forces could just be the next set of rules physics for small things (from the perspective of the parent universe) after gravity overcomes the dominant ones in that universe. Which could mean that all black holes are tunnels to other universes (that we can’t visit but the matter that makes us could, though it would probably be something else once it did, like an entire galaxy cluster).
Then the CMB might just be light that entered our universe from the parent one, redshifted like crazy (plus other optical gravitational effects, like any light that enters will appear brighter in one direction but coming from all directions to some extent).
That’s pretty cool sci-fi!