Where Is The Center Of The Big Bang Universe?

[BenHad]

Have there been any theories, papers, etc. on where the center of the Universe (Big Bang location) is located? I've found references about the age of the Universe, but not the center. A recent article in "Science News" suggests that a gravitional lensed (sp?) galaxy is 13.7-billion-years-old, only 700 millions after the Big Bang. Would this indicate the direction to the center of the Universe?

The galaxy in the article is A1689-zD1.

 

[Olowkow]

Layman's answer:

Most would say there is no center. Space actually expanded or inflated at the big bang. The analogy is like saying where is the center on the surface of a sphere. Everything just is "moving" away from everything else, because the universe expands. It is a tricky concept to grasp, but I'm sure one of the "experts" will jump in.

 

[sol invictus]

You're right - it doesn't have a center.

Where is the center of the surface of the earth?

 

[Dan O.]

If you look in any direction you would find that the edge of the visible universe is exactly the same distance away. That means we (or more specifically "you") are in the exact center of the universe.

 

[MattusMaximus]

Sol's answer is a good one, but here's a way to illustrate it for yourself.

Get a balloon and a marker. Place some dots on the outer surface of the balloon. The balloon's outer surface represents the spacetime fabric of our universe, and the dots represent galaxies and galaxy clusters. You can even mark one dot with MW for Milky Way (our galaxy).

Now, slowly inflate the balloon and observe what happens. From the point of view of MW, all the other galaxies and clusters appear to move away -- likewise, from the point of view of another galaxy, the MW and all others would appear to move away. So, the idea is that no matter where you are in the universe, you will observe everything to be stretching away from you and could easily conclude that you're at the "center".

This is an illustration of what's known as the Cosmological Principle.

Two important points to note about this example:

1. People will often ask, "What's inside the balloon? Isn't that where the 'center' is?"

The answers are "nothing" and "no." Remember that in this model the entire universe is the stretched fabric of the outer surface of the balloon. The question of what's "inside" isn't relevant, unless you wish to speculate about hypothetical extra dimensions of space, etc.

2. Note that the dots on your balloon do not actually move along the surface of the balloon; rather they move with the balloon's surface as it stretches. In addition, dots further from the MW dot will appear to stretch away faster than nearby ones.

This points out a common misconception about big bang cosmology: that galaxies and galaxy clusters are actually moving through space. They aren't (for the purposes of an expanding universe, that is), instead they are being carried along with the spacetime fabric of the universe as it is undergoing an expansion or stretching.

Lastly, about the further points moving faster as compared to the closer ones: this is an illustration of Hubble's Law, which was one of the first ways we quantified the age of the universe to be many billions of years (roughly 13.7 billion years by current estimates).

I hope this helps. Have fun with your balloons!

 

[Broes]

Cosmic background radiation is equally distributed in every direction we look.

The CBR is the remaining 'noise' of the big bang. So either we ARE rather close to the centre, or there is no centre and alle galaxies see the same thing as we do here on earth.

 

[MattusMaximus]

Cosmic background radiation is equally distributed in every direction we look.

The CBR is the remaining 'noise' of the big bang. So either we ARE rather close to the centre, or there is no centre and alle galaxies see the same thing as we do here on earth.

There is no "center" -- see my post above. Btw, great point about the CBR!

 

[Gate2501]

When I learned about time being the 4th dimension I sort of accidentally imagined my own balloon model without hearing of it prior.

I tried to think of how you could possibly add a 4th dimension to 3d space and decided that the only way to do it (in my head) was to imagine our 3 dimensions in 2d and have time running at 90degrees to it. Like little time arrows pushing out on a balloon from the inside.

I also at that time concluded that this was why the universe was expanding, cause the balloon had to get bigger cause the past was inside of there leaving the future no where to go but outward! I quickly realized that part was a bunch of woo, but the model always stuck in my head. The big bang being the empty spot right in the center of that balloon.

I dunno how right that is, I am just a layman.

 

[sol invictus]

I dunno how right that is, I am just a layman.

Mattus gave a good way to think about it.

I would start by imagining you're a little ant that lives on a line. You can only move left or right along the line, but not forward or backwards, or up and down. So the line is your world - it's a one-dimensional world.

Now imagine the line is actually a big circle. It's still true that you can only move left or right, but if you walk far enough in the same direction you end up back where you started. Notice that the line itself (which is all you can see or travel to) does not have a center regardless of whether we wrap it around into a circle.

Now imagine the circle is expanding with time, so that as time passes, you have to walk further and further to get back to where you started.

Now scale that up by one dimension - instead of a line, a plane, rather than a circle, the surface of an expanding balloon.

Now scale that up by one more dimension (a little harder to picture now, isn't it! ), and you have what is called a closed big bang cosmology (perhaps like the one we live in). It's one of essentially only three possibilities (the other two being the three dimensional analog of the line being infinite and straight - but stretching and expanding - or like a hyperbola - curved, but infinite in length, and expanding).

 

[MattusMaximus]

When I learned about time being the 4th dimension I sort of accidentally imagined my own balloon model without hearing of it prior.

I tried to think of how you could possibly add a 4th dimension to 3d space and decided that the only way to do it (in my head) was to imagine our 3 dimensions in 2d and have time running at 90degrees to it. Like little time arrows pushing out on a balloon from the inside.

A reasonable question. In the balloon model I described, remember that the surface of the balloon represents the spacetime of the universe. So you can think of it as 2D + 1 (where normal 3D space is "squashed" into 2D and +1 represents time).

I, like you, have no way to visualize a 3D + 1 model easily.

I also at that time concluded that this was why the universe was expanding, cause the balloon had to get bigger cause the past was inside of there leaving the future no where to go but outward! I quickly realized that part was a bunch of woo, but the model always stuck in my head. The big bang being the empty spot right in the center of that balloon.

I dunno how right that is, I am just a layman.

Try to fight that misconception. I know it's tough, but it's an important point. For the purposes of this balloon model, what's "inside" isn't relevant -- the entire universe we observe exists on the outer surface of the balloon.

As for the big bang, imagine taking the balloon and deflating it. All the observable universe (that which we can measure now), that is the surface of the balloon, was shrunken into a small volume long ago.

This is another point where I must note another popular misconception: the big bang (despite its name) was not an explosion from a small point. Rather, imagine that our entire section of the observable universe (also called our Hubble volume) was condensed into such a small point long ago, but that is only the corner of our universe we can observe. We have every reason to suspect that the universe extends far beyond our Hubble limit, so that would mean that the next Hubble volume was condensed into a small volume long ago, and same with the next, and so on...

So, I guess a good way to put it is that the big bang didn't take place at a single point; rather, it took place everywhere.

Try wrapping your mind around that picture. I've taught about this for years, and I'm just now getting a good intuitive hold on it - but it's damned weird.

If you want to read more about this, Scientific American had a good series of articles on "Misconceptions About the Big Bang" a few years ago. Check it out.

 

[Gate2501]

Wouldn't the *center* tho of the big bang universe be impossible to define as a location in space (our 3 dimensions)?

I would think there there would be a *center* or *place* somewhere down the axis of time, where the big bang occurred. We just wouldn't be able to define that place in our current space. Am I just crazy in visualizing the past as some finite stuff that exists back behind us on this time axis? I honestly have no idea.

 

[MattusMaximus]

Wouldn't the *center* tho of the big bang universe be impossible to define as a location in space (our 3 dimensions)?

Yes, I believe this is correct using the definition of "center" as we're used to. it just doesn't apply in this situation. Sol, what do you think?

I would think there there would be a *center* or *place* somewhere down the axis of time, where the big bang occurred. We just wouldn't be able to define that place in our current space. Am I just crazy in visualizing the past as some finite stuff that exists back behind us on this time axis? I honestly have no idea.

Yes, if you wanted to think of it as a "center" on the time axis, the number you'd get (according to current data) would be roughly 13.7 billion years.

Don't worry if you have trouble visualizing this, it isn't easy for me either.

 

[Dark Jaguar]

According to Phil Plait it turns out that it's the flat arrangement. I have to admit that's the one I least expected, because it seemed to me more likely that the density level would fall to one side or the other than land directly on that middle amount. However, that's where the evidence points.

http://www.badastronomy.com/bablog/2008/03/05/the-universe-is-1373-12-billion-years-old/

 

[sol invictus]

Yes, I believe this is correct using the definition of "center" as we're used to. it just doesn't apply in this situation. Sol, what do you think?

Yeah, I agree. The cosmological principle you described can be summarized by saying that the universe on large scales is both homogeneous (meaning every point is equivalent to every other point) and isotropic (meaning every direction looks like every other direction). A homogeneous space cannot have a center, because that would be a point that's different from the rest.

 

[Olowkow]

...Get a balloon and a marker. Place some dots on the outer surface of the balloon. The balloon's outer surface represents the spacetime fabric of our universe, and the dots represent galaxies and galaxy clusters. ...

Strictly speaking, I read somewhere that one should glue pennies to the balloon to represent galaxies in this analogy, since the galaxies are not themselves expanding as they would if they were dots on the fabric of the balloon.

 

[MattusMaximus]

Strictly speaking, I read somewhere that one should glue pennies to the balloon to represent galaxies in this analogy, since the galaxies are not themselves expanding as they would if they were dots on the fabric of the balloon.

Good point. Perhaps gluing grains of sand onto the balloon would be even better.

 

[sol invictus]

According to Phil Plait it turns out that it's the flat arrangement.

He's not telling the whole story. The data is consistent with the universe being flat, but really big closed and open universes look flat too - because we can only see a small piece of them. Just like the surface of the earth looks flat because you can only see a small part of it.

So all we actually know is that the universe is really big - bigger than the finite part we can observe.

 

[sol invictus]

Good point. Perhaps gluing grains of sand onto the balloon would be even better.

Yeah, that is a good point. They're actually getting smaller, at least below 10 Mpc or so.

 

[Gate2501]

According to Phil Plait it turns out that it's the flat arrangement. I have to admit that's the one I least expected, because it seemed to me more likely that the density level would fall to one side or the other than land directly on that middle amount. However, that's where the evidence points.

http://www.badastronomy.com/bablog/2008/03/05/the-universe-is-1373-12-billion-years-old/

What if the universe looks flat to us, simply because that flat spot is a small spot on a MASSIVE multi-verse (outside of that Hubble boundary thingy I just read about). Then it may only look flat because the sphere or saddle is so large? I guess that wouldn't really matter since the rest of the stuff is outside of our ability to measure anyhow.

I read a book my Leonard Susskind that was pretty convincing, dealing with the Anthropic Principle pretty much suggesting that either there is a God (Baloney), or that we are only seeing a small part of the whole of this multi-verse.

Sorry that I posit silly things and ask questions so much

Edit: Seems like Sol already addressed this while I was typing *argh*

 

[Fredrik]

When I learned about time being the 4th dimension I sort of accidentally imagined my own balloon model without hearing of it prior.

I tried to think of how you could possibly add a 4th dimension to 3d space and decided that the only way to do it (in my head) was to imagine our 3 dimensions in 2d and have time running at 90degrees to it. Like little time arrows pushing out on a balloon from the inside.

That's not bad at all. In fact, if I understand you correctly, you're describing exactly the same thing as Sol Invictus in his reply. There are three solutions of Einstein's equation that describe a homogeneous and isotropic universe with the "cosmological constant" (i.e. the density of vacuum) =0, and you're describing one of them (with one spatial dimension missing of course, but you are already aware of that).

I also at that time concluded that this was why the universe was expanding, cause the balloon had to get bigger cause the past was inside of there leaving the future no where to go but outward! I quickly realized that part was a bunch of woo, but the model always stuck in my head.

Yes, that part is wrong. The prediction of this model is actually that the universe will reach a maximum size and then and collapse into a "big crunch". (However, the density of vacuum in our actual universe isn't zero, so this model isn't realistic).

The big bang being the empty spot right in the center of that balloon.

That part is not wrong. Note that "the universe at time t" is always a spherical surface, and that the size of that surface depends on t. The time t=0 is not a part of this model. One of the reasons for that is that it would contradict the assumptions that were made to find this solution in the first place. We say that we're approaching a singularity as t goes to 0, and we call the singularity at t=0 "the big bang".

A lot of people think the big bang was an explosion in a pre-existing space, but it's not even a point or any other kind of structure in space-time. It's just a term that describes a property of space-time.