The center of the universe

[tskaze]

correct me if im wrong, but its pretty well accepted that the universe is spherical. Since spheres have a center you can find if you know its radius, the universe logically has one as well.

 

I often go to my science teacher with this type of question, but even after i explain the above paragraph to them, they still tell me the center is relative. How can this be?

[Bettina]

Hello.....

Here is a great article. I love this and have read it more than once.

 

http://www.sciam.com/article.cfm?chanID=sa006&colID=1&articleID=0009F0CA-C523-1213-852383414B7F0147

 

Bettina

[bascule]

correct me if im wrong, but its pretty well accepted that the universe is spherical.

 

No, it's not. Most evidence today paints a picture of an infinite flat universe, although it's possible it's sphere shaped with positive curvature or saddle shaped with negative curvature.

 

Since spheres have a center you can find if you know its radius, the universe logically has one as well.

 

I often go to my science teacher with this type of question, but even after i explain the above paragraph to them, they still tell me the center is relative. How can this be?

 

Because the big bang was an explosion OF space, not an explosion IN space.

[tskaze]

right but if you know the boundaries of a regular 3 dimensional figure, cant you mathmatically find its center?

[Bettina]

right but if you know the boundaries of a regular 3 dimensional figure, cant you mathmatically find its center?

 

I think finding the boundaries is the problem. Where do you start. If the total universe is spherical which I'm sure it is, but the observable universe is flat due to the spheres size, how do you find the center?

 

If you were standing on a sphere that was a million miles in diameter, but because of fog you could only see about 100 feet, the surface you were standing on would seem flat to you.

 

The universe looks flat to us, but only the part we can see. I think this is correct to todays thinking.

 

Bettina

[Spyman]

No, it's not. Most evidence today paints a picture of an infinite flat universe, although it's possible it's sphere shaped with positive curvature or saddle shaped with negative curvature.

I thought "flat" meant no bending in any dimension which combined with infinite gives a spherical universe with infinite radius.

 

The "sphere" and "saddle" shape Your talking about is a 2D-view of universe bent in a positive or negative curvature in another dimension not the third.

 

A 3D universe could still be spherical even if bent in a "sphere" or "saddle" shape, it's just very hard to imagine or show in a picture.

[J.C.MacSwell]

right but if you know the boundaries of a regular 3 dimensional figure, cant you mathmatically find its center?

 

I think if it is approximately spherical it is hyper-spherical with our volume (the one we are in) being the 3D "surface" locally. You cannot point toward "the centre", you can only point along the surface no matter which direction you point in our volume.

[Spyman]

I think if it is approximately spherical it is hyper-spherical with our[/b'] volume (the one we are in) being the 3D "surface" locally. You cannot point toward "the centre", you can only point along the surface no matter which direction you point in our volume.

Is it still hyper-spherical if it's flat ?

[Megadeth]

originally posted by tskaze

correct me if im wrong, but its pretty well accepted that the universe is spherical. Since spheres have a center you can find if you know its radius, the universe logically has one as well.

 

I often go to my science teacher with this type of question, but even after i explain the above paragraph to them, they still tell me the center is relative. How can this be?

 

When you think of the big bang you are assuming that it was only matter that was created. The big bang created 'space time' as well. Todays present universe is an expanded form of the singularity, and so the centre of the universe is in fact everywhere.

[Megadeth]

sorry, i just repeated what bascule said.

[danny8522003]

If you think of the universe as a 2D film (like the skin of a balloon) that has expanded into a sphere of 3Ds, you will realise that without escaping our universe you could never locate the centre of this sphere. What would be the point in doing so anyway? We could never "point" to the centre of the universe or even reach it so IMO it would be useless especially seeing as the sphere would be of a rediculously large size.

 

You have to take into account that this sphere would also have to be 4D and it's surface 3D, creating a hypersphere. This discounts time as another dimension.

[EL]

If you think of the universe as a 1D string then you can wrap it around your finger, but if you think of the universe as a 666D you can scratch your head honestly and say that you have no freaking idea what the question was to which you have no answer because the whole idea is to play with Chinese wanton concepts of new-age-physics of speculative predictions such as if you could throw a piece of chalk faster than light you could have hit the last lesson's teacher.

People; how about coming back down-to-earth for a while and solving real life problems rather than wasting your lives answering ridiculous questions?

[J.C.MacSwell]

If you think of the universe as a 1D string then you can wrap it around your finger' date=' but if you think of the universe as a 666D you can scratch your head honestly and say that you have no freaking idea what the question was to which you have no answer because the whole idea is to play with Chinese wanton concepts of new-age-physics of speculative predictions such as if you could throw a piece of chalk faster than light you could have hit the last lesson's teacher.

People; how about coming back down-to-earth for a while and solving real life problems rather than wasting your lives answering ridiculous questions?[/quote']

 

Your mother wanted me to pass along this message:

 

"For the hunredth time EL, turn off that computer and get out and mow the lawn!"

[James R]

When people say things like "the universe is spherical", they aren't usually referring to the usual 3-dimensional sphere. More probably, they're referring to a particular 4-dimensional model of our universe's spacetime.

 

A good analogy is to drop one dimension. Imagine that you can only travel on the surface of the Earth: north, south, east or west, but you have no knowledge of "up and down". The geometry of the Earth's surface is the geometry of a sphere (obviously) in 3 dimensions, but you live in 2 dimensions. Where is the "centre" of the sphere? It's at the centre of the Earth. But, as a 2-dimensional being, you can't point to it, since it exists in the "down" direction, and you don't know about "down".

 

In fact, from your 2-dimensional perspective, where the SURFACE of the Earth is all that exists, your world has no centre. If you move off in one direction, you eventually end up back where you started. And no point on the Earth's surface is "more special" than any other point, so no point on the surface can be considered to be the "centre".

 

Now go to our actual universe. Suppose we live on the 3-D surface of a 4-sphere. We only know about the directions north, south, east, west, up, down. We can't point in the direction of the centre of the 4-sphere, and in fact the centre is not part of the space we inhabit. Our universe therefore has no centre in the usual sense.

[ydoaPs]

When people say things like "the universe is spherical"' date=' they aren't usually referring to the usual 3-dimensional sphere. More probably, they're referring to a particular 4-dimensional model of our universe's spacetime.

 

A good analogy is to drop one dimension. Imagine that you can only travel on the surface of the Earth: north, south, east or west, but you have no knowledge of "up and down". The geometry of the Earth's surface is the geometry of a sphere (obviously) in 3 dimensions, but you live in 2 dimensions. Where is the "centre" of the sphere? It's at the centre of the Earth. But, as a 2-dimensional being, you can't point to it, since it exists in the "down" direction, and you don't know about "down".

 

In fact, from your 2-dimensional perspective, where the SURFACE of the Earth is all that exists, your world has no centre. If you move off in one direction, you eventually end up back where you started. And no point on the Earth's surface is "more special" than any other point, so no point on the surface can be considered to be the "centre".

 

Now go to our actual universe. Suppose we live on the 3-D surface of a 4-sphere. We only know about the directions north, south, east, west, up, down. We can't point in the direction of the centre of the 4-sphere, and in fact the centre is not part of the space we inhabit. Our universe therefore has no centre in the usual sense.[/quote']

 

sorry, but the surface of a ball only has 2 dimensions. that is why it is called a 2-sphere. if you drop a dimension, you are left with a circle which is one dimensional, not two.

[danny8522003]

He means the overall sphere is 3D and the surface, as you said, is 2D.

 

I see exactly what you mean James, sounds the same sort of anology as i read elsewhere.

[Spyman]

You have to take into account that this sphere would also have to be 4D and it's surface 3D, creating a hypersphere. [b']This discounts time as another dimension.[/b]

Why ? You need Four dimensions for creating a hypersphere...

 

Can't time be considered as the first dimension, thus the radius of the hypersphere ?

[danny8522003]

I wouldnt have thought so because time is not a spacial dimension. The fact we live in a 3D universe implies that the sphere we may be on has to be 4D. In the same way the surface of a ball is 2D (discount the thickness) but the ball requires 3D in order to exist...

[Spyman]

Well, it's just a though that have "popped" up in my mind...

 

It steamed from the relativistic use of Time as an equal part of a position in space-time and as we move forward in Time space expands, reverse Time to BB and You are in the center.

 

The future is outside the "balloon", the skin is the present and the past is inside.

 

 

EDIT: (Wick rotation)

 

Suffice it to say that we replace the time variable "t" in all our calculations by "it", do a bunch of calculations, and then replace "it" by "t" again at the end. This trick is called "Wick rotation". In the middle of this process, we hope all our formulas involving the geometry of 4d spacetime have magically become formulas involving the geometry of 4d space.

http://math.ucr.edu/home/baez/week207.html

 

In physics, a Wick rotation is the process by which a theory in Euclidean space is analytically continued into one in Minkowski space and vice versa. It consists simply of replacing every instance of the variable t (representing time) with it (effectively redefining t), including within the derivatives. This relates statistical mechanics to quantum field theory, although why it works is a bit of a mystery.

http://en.wikipedia.org/wiki/Wick_rotation

 

Wick's idea was to multiply Minkowski's time by i, the square root of minus 1. That converts the metric to Euclidean ds² = c²dt² + dx² + dy^{2[/sup'] + dzV, and with units so that c = 1, it becomes pure Euclidean 4D space.}

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