So I’ve been going through the dangerous rabbit hole of wondering how everything came to be and, obviously, the leading theory is the big bang theory. Where an infinitely dense spot of matter exploded and created every single thing in existence, including the ever-expanding universe. So, if the ever-expanding universe started expanding from an infinitely dense spot that exploded, wouldn’t that spot be the “center of the universe”, since it’s the starting point of said expansion?
In: 7
My answer: the big bang.
Imagine a sphere that is expanding in size, like a balloon being inflated. Note that the surface of the balloon is flat, i.e. two-dimensional. Now imagine a tiny 2D creature living on that surface, like a flat ant crawling on the surface of a beach ball.
Now consider how this world looks to the ant, compared to how it looks to us.
The ant says:
* My world is flat and two-dimensional. I define X as forward/backward and Y as left/right, but I have no concept of any other spatial direction.
* My world is unbounded, there’s no edge, but it has a finite amount of space, and that amount is expanding over time
* My world has no center, every spot is just like every other, so your question is meaningless
From our 3D perspective, we would say:
* Your world does indeed have two spatial dimensions, X and Y, but I can see that it’s curved through a radial spatial dimension, R, which is orthogonal at all points to X and Y
* What you call “expanding through time” is what I call “increasing distance R”. What you call the past is what I would call inward, and what you call the future is what I would call the same value of X and Y but a larger value of R.
* There is no “center” **on** the 2D surface at any particular value of R, but your world does have a center in 3D space: the origin point, what you would call t=0 and I would call R=0. It’s clearly the center, because at any value of R, that point is equidistant from every point on the 2D surface of your world.
* You might find it interesting that at that point, X=Y=R=0, the 2D surface you occupy is infinitely small and dense
Hopefully it’s clear that the point of this analogy is to suggest that our universe is similar, but with one extra spatial dimension. We would say:
* Our world has three spatial dimensions, X, Y and Z, and moves forward through time
* The volume of our universe is unbounded, but it is finite and increasing
* There is no “center” of the universe, as described in every other answer here
But you can imagine an alien who might say:
* I, from my 4D perspective, can see that your world is curved through a 4th spatial dimension R which is orthogonal to X, Y, and Z
* You experience this dimension as time; what you call “the future” I call “larger values of R”
* There is no center on the 3D “surface” of your universe, but viewed in 4 spatial dimensions it’s clear that the center is the origin point, what you’d call t=0 and I call R=0, the point at which your 3D world is infinitely small and dense: the big bang.
NB: this explanation is more thought-provoking than useful; it’s just an analogy, and AFAIK you can’t use this perspective to solve any previously unsolved question. It’s just a good way to visualize how a 3D surface can be limitless but still finite, and what “center” might mean in different dimensions. I hope you find it interesting (and that this thread isn’t too old for some real physicists to come along and tear it to shreds 🙂 ).
My answer: the big bang.
Imagine a sphere that is expanding in size, like a balloon being inflated. Note that the surface of the balloon is flat, i.e. two-dimensional. Now imagine a tiny 2D creature living on that surface, like a flat ant crawling on the surface of a beach ball.
Now consider how this world looks to the ant, compared to how it looks to us.
The ant says:
* My world is flat and two-dimensional. I define X as forward/backward and Y as left/right, but I have no concept of any other spatial direction.
* My world is unbounded, there’s no edge, but it has a finite amount of space, and that amount is expanding over time
* My world has no center, every spot is just like every other, so your question is meaningless
From our 3D perspective, we would say:
* Your world does indeed have two spatial dimensions, X and Y, but I can see that it’s curved through a radial spatial dimension, R, which is orthogonal at all points to X and Y
* What you call “expanding through time” is what I call “increasing distance R”. What you call the past is what I would call inward, and what you call the future is what I would call the same value of X and Y but a larger value of R.
* There is no “center” **on** the 2D surface at any particular value of R, but your world does have a center in 3D space: the origin point, what you would call t=0 and I would call R=0. It’s clearly the center, because at any value of R, that point is equidistant from every point on the 2D surface of your world.
* You might find it interesting that at that point, X=Y=R=0, the 2D surface you occupy is infinitely small and dense
Hopefully it’s clear that the point of this analogy is to suggest that our universe is similar, but with one extra spatial dimension. We would say:
* Our world has three spatial dimensions, X, Y and Z, and moves forward through time
* The volume of our universe is unbounded, but it is finite and increasing
* There is no “center” of the universe, as described in every other answer here
But you can imagine an alien who might say:
* I, from my 4D perspective, can see that your world is curved through a 4th spatial dimension R which is orthogonal to X, Y, and Z
* You experience this dimension as time; what you call “the future” I call “larger values of R”
* There is no center on the 3D “surface” of your universe, but viewed in 4 spatial dimensions it’s clear that the center is the origin point, what you’d call t=0 and I call R=0, the point at which your 3D world is infinitely small and dense: the big bang.
NB: this explanation is more thought-provoking than useful; it’s just an analogy, and AFAIK you can’t use this perspective to solve any previously unsolved question. It’s just a good way to visualize how a 3D surface can be limitless but still finite, and what “center” might mean in different dimensions. I hope you find it interesting (and that this thread isn’t too old for some real physicists to come along and tear it to shreds 🙂 ).
The beginning of the universe is often described as an infinity dense point that then, over the next 14 billion years, expanded and continues to expand into what we see today. This is a simplification to make the concept easier to understand.
The reality is that it wasn’t a single infinitely desne point, but rather the beginning of the univers, as far as we can tell, was an infinity dense everything that happened everywhere all at once, and that everything has been expanding ever since.
There may be a center, there may not. We have a limit to how far we can see, which is what we call the observable universe. There is most likely even more galaxies past what we can see, but because we can’t see everything, there is no way for us to know where the center is or if a center even exists.
The beginning of the universe is often described as an infinity dense point that then, over the next 14 billion years, expanded and continues to expand into what we see today. This is a simplification to make the concept easier to understand.
The reality is that it wasn’t a single infinitely desne point, but rather the beginning of the univers, as far as we can tell, was an infinity dense everything that happened everywhere all at once, and that everything has been expanding ever since.
There may be a center, there may not. We have a limit to how far we can see, which is what we call the observable universe. There is most likely even more galaxies past what we can see, but because we can’t see everything, there is no way for us to know where the center is or if a center even exists.
You are misunderstanding nature of big bang singularity and expansion. It wasn’t infinitely small early universe, it was infinitely dense early universe.
Universe doesn’t have some hard border, best we can tell its infinitely large and always has been. But in the past everything was much closer to everything else right down to very early universe when vacuum of space wasn’t even a thing because everything was so close together, and very hot too, nuclear fusion type of environment.
Expansion of the universe is not increase of some border, because universe has no such thing. Its expansion of space between everything, uniformly, there is no center everything is expanding away from.
You are misunderstanding nature of big bang singularity and expansion. It wasn’t infinitely small early universe, it was infinitely dense early universe.
Universe doesn’t have some hard border, best we can tell its infinitely large and always has been. But in the past everything was much closer to everything else right down to very early universe when vacuum of space wasn’t even a thing because everything was so close together, and very hot too, nuclear fusion type of environment.
Expansion of the universe is not increase of some border, because universe has no such thing. Its expansion of space between everything, uniformly, there is no center everything is expanding away from.
the universe is getting bigger so
from your own pov other stars and everything is getting away from you
from the pow of other stars, everything is getting away from them
if you run it back in time every star will get closer to you and from the pov of other stars everything will get closer to them
in reality some stars may be getting close to us due to their galactic motion path but overal everything is getting away from everything else
the universe is getting bigger so
from your own pov other stars and everything is getting away from you
from the pow of other stars, everything is getting away from them
if you run it back in time every star will get closer to you and from the pov of other stars everything will get closer to them
in reality some stars may be getting close to us due to their galactic motion path but overal everything is getting away from everything else
> the leading theory is the big bang theory
The big bang theory doesn’t really explain “how everything came to be” – it merely explains how the universe has changed since a certain point in time. And I don’t think “leading theory” is strong enough – there aren’t really any serious alternatives, and it has copious amounts of supporting evidence.
> Where an infinitely dense spot of matter exploded
This is a misconception. The big bang theory describes how the universe has expanded and cooled since a point in time at which it was an extremely hot, dense, uniform “soup” of subatomic particles. If you extrapolate the equations even further back in time, you end up at a point where the entire universe was infinitely dense, but there are good reasons to believe that those equations can’t be extrapolated back that far. It’s not really clear that the idea of an “infinitely dense spot” is physically meaningful – certainly, in the past, whenever theories predicted that anything was infinite, they eventually turned out to be incomplete.
Anyway, we can only measure our position in the universe relative to other things in the universe. It’s not like there are some axes in the background telling us where zero is. On the largest scales, the universe looks essentially the same in all directions – there doesn’t appear to be any particular star or galaxy that everything revolves around. So there is no apparent “centre”.
> the leading theory is the big bang theory
The big bang theory doesn’t really explain “how everything came to be” – it merely explains how the universe has changed since a certain point in time. And I don’t think “leading theory” is strong enough – there aren’t really any serious alternatives, and it has copious amounts of supporting evidence.
> Where an infinitely dense spot of matter exploded
This is a misconception. The big bang theory describes how the universe has expanded and cooled since a point in time at which it was an extremely hot, dense, uniform “soup” of subatomic particles. If you extrapolate the equations even further back in time, you end up at a point where the entire universe was infinitely dense, but there are good reasons to believe that those equations can’t be extrapolated back that far. It’s not really clear that the idea of an “infinitely dense spot” is physically meaningful – certainly, in the past, whenever theories predicted that anything was infinite, they eventually turned out to be incomplete.
Anyway, we can only measure our position in the universe relative to other things in the universe. It’s not like there are some axes in the background telling us where zero is. On the largest scales, the universe looks essentially the same in all directions – there doesn’t appear to be any particular star or galaxy that everything revolves around. So there is no apparent “centre”.
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