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viscence t1_jd0ehya wrote

Every experiment you can do to find out will tell you the same thing: "right here". If you measure how fast a galaxy is moving, you find that they all tend to move away from "here," and moreover they tend to move away from "here" faster the further they're away.

So did the big bang happen here and we're just spectacularly privileged to live in exactly that place? No. It doesn't matter where you perform the experiment, the answer is always "here". The explanation for this is that space itself is expanding. We're not seeing debris being thrown away from a central location where an explosion happened into some pre-existing space, what we're seeing is the metric expansion of space itself. All the distances between things are just increasing, not because the things are actually moving but rather because the space between them is literally growing. If you extrapolate time backwards far enough, all the distances become zero, and we call that singularity where our understanding of physics breaks down "big bang".

If you have two objects that are too far apart to affect each other, but that randomly happen to be stationary with respect to each other today, then tomorrow they will be further apart. There is no centre to this. The universe isn't expanding away from one spot, it's expanding everywhere like an infinite sponge soaking up water. And really, with the universe being infinite as far as we know, there can't really be another answer. It's not like the centre could have been "three quarters of an infinity" away from here.


mfb- t1_jd1k8zg wrote

> If you have two objects that are too far apart to affect each other, but that randomly happen to be stationary with respect to each other today, then tomorrow they will be further apart.

This statement is correct today, but only because of dark energy. You could have an expanding universe where it would be wrong (and for several billion years it was wrong in our universe), so it's not a direct consequence of expansion.


Krail t1_jd2bwak wrote

There was a post a couple days ago where someone was staunchly asserting that space is not actually expanding and that objects really are moving away from one another kinetically, with multiple citations on the subject (which I didn't look too far into). There was a bit of discussion and a couple people agreed with them.

This was the first I'd heard about that. All modern material I've ever seen on astrophysics (the last twenty five years or so?) talks about the universe expanding.

How solid is the scientific consensus on this subject? Is it actually contentious at the moment, or was this person stating an belief that is currently kind of fringe?


Dorigoon t1_jd9z0jx wrote

So to answer OP's question, we don't know, right?


viscence t1_jda3hah wrote

No, that's not right. We do know that no such "place" exists.


Dorigoon t1_jdar8ym wrote

So the location of the big bang can't be plotted on a hypothetical xyz axis? Is that because our math is incapable of calculating this? Unknown variables?


Shirkie01 t1_jdaxzfb wrote

The answer to "where did the Big Bang happen" is always "exactly where you are", no matter where you are. This is because it's not an event that happened in the universe, it is the universe.

Unfortunately I can't find the GIF with the expanding red dots that made it clearer, but the idea is that there is no preferred reference frame and thus no location that's "more important" than any other.

This image might help. Picture A is the location of galaxies at some given time, while Picture B is the location of galaxies at some future time. Pictures C and D show that the galaxies appear to be moving away from "here", wherever "here" might be, and the galaxies farther away from "here" appear to be moving faster.


ethereal_phoenix1 t1_jdrgcwd wrote

The reason why the center can't be plotted on and xyz axis it does not exist on the xyz axis.

In 2d think of the universe as the surface of a balloon being inflated there is no point on the surface of where expantion started (expantion started in the centre) as all points on the surface are moving away from all other points uniformly.

P.s. I know this I 3 days old