Where is the center of the universe?

[Fredrik]

Thanks for your extensive replies. I have difficulty trying to picture the Big Bang as a property of a class of solutions of Einstein's equations. Sorry but my maths is not up to much - by 'class of solutions of' do you mean 'subset of formulas derived from'?

I mean a subset of the set of all solutions to Einstein's equation. Each solution describes a spacetime, so I'm talking about a subset of the set of all possible spacetimes. Specifically, the set of all 4-dimensional spacetimes that can be "sliced" into 3-dimensional "spacelike hypersurfaces" (sorry about using another technical term) that are are all homogeneous and isotropic (in a technical sense). We can think of these hypersurfaces as "space, at different times". If we label them with a parameter t>0, it's a fact that in any of these spacetimes, the distance between any two objects that are "floating freely in space" (like two galaxies) goes to zero as t goes to zero.

The value of this parameter t is assigned in a way that ensures that the word "time" is appropriate.

If you can't assign the value t=0 to the formulas, presumably due to fear of infinities, but you can assign t=0 + a miniscule amount, then it still feels like an event to me.

I suppose it does, but we're talking about the theory that tells us what time is, so we can't assume that time has different properties than what the theory is saying. If the theory doesn't even mention a t=0, how can we?

Einstein is reported to have said 'Most of the fundamental ideas of science are essentially simple, and may, as a rule, be expressed in a language comprehensible to everyone'. I guess this example is the exception :-(.

I can think of lots of examples that are much worse than this.

 

[blank.black]

There are lots of garbage claims in documentaries about these things, but I doubt that they had astrophysicists on the show who said that. It's definitely wrong.

Yes there were astrophysicists, theoretical physicists, cosmologists, etc. etc...but even if the astrophysicists on there didn't say something like that, the fact that they were on the show i think implies that they clearly support the idea and have nothing against it...otherwise why would they be part of it?

 

[Evo]

Yes there were astrophysicists, theoretical physicists, cosmologists, etc. etc...but even if the astrophysicists on there didn't say something like that, the fact that they were on the show i think implies that they clearly support the idea and have nothing against it...otherwise why would they be part of it?

Selective editing quite often completely changes what someone actually said.

 

[Greylorn]

That's exactly the kind of ridiculous and insulting nonsense I would expect from a creationist who isn't at all interested in learning what this theory says or what a theory is.


Those are not the only two options. And to prove a theory wrong, you have to perform experiments. Just asking questions isn't going to do it.

Fredrik,
You've provided excellent and well-considered replies to most of my questions. Thank you for both understanding and direction.

I'm not particularly interested in proving any theory wrong. I'm a theorist (and I do seriously care about what a theory is), probably because budget limitations have precluded the purchase of my own space telescope. I'm asking questions not to be a pest, but in hopes of finding the right theoretical direction. Only a crackpot would develop a theory which skirts evidence, or attempts to re-explain something which is already fully covered by a well-proven existing theory.

After more thinking I may come up with other questions, and will take the liberty of apprising you accordingly in case you care to engage them. You set a high standard for this forum. Thank you.

 

[blank.black]

Selective editing quite often completely changes what someone actually said.

huh?

 

[Ich]

All homogeneous and isotropic solution have an initial singularity.

All expanding homogeneous and isotropic solutions with sufficient matter/radiation density and appropriate conservation laws have an initial singularity.
There are solutions without an initial singularity or without singularities at all, but they don't match observational evidence (with the possible exception of some inflationary models).
It doesn't matter anyway, the singularity itself is not part of the Big Bang model. The hot, dense state at the beginning is undoubted.

 

[Fredrik]

Yes there were astrophysicists, theoretical physicists, cosmologists, etc. etc...but even if the astrophysicists on there didn't say something like that, the fact that they were on the show i think implies that they clearly support the idea and have nothing against it...otherwise why would they be part of it?

Some of them are probably really bad at finding appropriate ways to simplify what the theory says. And I assume that most of them don't know if it will be a good documentary or a bad one when they're being interviewed, so I don't think the fact that they agreed to be in it means anything.

 

[Evo]

Yes there were astrophysicists, theoretical physicists, cosmologists, etc. etc...but even if the astrophysicists on there didn't say something like that, the fact that they were on the show i think implies that they clearly support the idea and have nothing against it...otherwise why would they be part of it?

Some of them are probably really bad at finding appropriate ways to simplify what the theory says. And I assume that most of them don't know if it will be a good documentary or a bad one when they're being interviewed, so I don't think the fact that they agreed to be in it means anything.

blank.black, here is a hypothetical example. A scientist is approached about giving an opinion on black holes for a show. After they are filmed, the title of the show turns out to be "black holes don't exist". The footage of the scientist is cut into snippets and a narrator makes comments and then out of context snippets from the scientist are inserted, making it sound like the scientist is backing the narrator up. This happens not only in films and documentaries, but in written articles for popular news and magazines.

I'm not saying this happens frequently, but it seems to happen a bit too often, and to varying degrees.

 

[dx]

This happens not only in films and documentaries, but in written articles for popular news and magazines.

A good example of this: http://en.wikipedia.org/wiki/What_the_bleep

 

[Quantum-lept]

It can be finite without having an edge. Think of the surface of a sphere for example.


No. Think e.g. of an infinite line with distance markings on it, and imagine the distance between the markings growing with time. The scale is changing, but the total size isn't.

Thank you.

Yes, a circle or surface of a sphere has no edge or start/stop point.

But a sphere does have a boundary/edge. And we are speaking more of a sphere, which i think has an edge/boundary, moving though it may be. There are many references to the universe's edge by astrophysicists. What are they referring to?

As for the universe expanding without changing size, that makes no sense.Though i admit that such a thing may be possible in this strange universe. Where are the galaxies on the edge of this universe going as they move away from all the others? Distances between galaxies is real, is it not?
Unless you insist that expansion without a change in size is occurring.

Maybe the math that these theories are derived from does not compute using analogies. But, thanks for the effort.

 

[Fredrik]

Yes, a circle or surface of a sphere has no edge or start/stop point.

But a sphere does have a boundary/edge.

First let me correct the terminology. I was sloppy when I said "the surface of a sphere". That's a weird thing to say because a sphere is a surface. The region "inside" the sphere is called a ball. For example, the set of all (x,y,z) that satisifes x²+y²+z²=r² is called a sphere (or a 2-sphere to be even more precise), with radius r. The set of all (x,y,z) that satisifes x²+y²+z²<r² is called an open ball of radius r. Replace the < with ≤ and the set is called a closed ball.

A ball has a boundary. That boundary is a sphere. A sphere doesn't have a boundary.

And we are speaking more of a sphere, which i think has an edge/boundary, moving though it may be.

When you say "sphere" here, you mean a "ball", and we are talking about spheres. 3-spheres to be exact. The homogeneous and isotropic solutions can be divided into three classes: positive curvature, zero curvature, and negative curvature. The zero curvature case is a lot like that infinite line with a time-dependent scale. The only difference is that a line is 1-dimensional and space is 3-dimensional. The positive curvature case is a lot like a sphere with a time-dependent radius. The only difference is that a sphere is 2-dimensional and space is 3-dimensional. So we should really be talking about a 3-sphere: w²+x²+y²+z²=r²

There are many references to the universe's edge by astrophysicists. What are they referring to?

You'd have to ask them, but I'm guessing that they're talking about the most distant objects we can see.

As for the universe expanding without changing size, that makes no sense. Though i admit that such a thing may be possible in this strange universe. Where are the galaxies on the edge of this universe going as they move away from all the others?

Don't forget that now we're talking about a universe that's infinite at all times (the zero curvature case). There's no edge.

 

[Chronos]

The 'edge' of the universe is right here on Earth - the most temporally distant point from the surface of last scattering. Would you agree we see nothing to suggest the universe is inhomogenous in any direction? It is irrelevant whether the universe is finite or infinite. All we know is it was hotter and denser in the past, and incredibly consistent in all directions.

 

[blank.black]

blank.black, here is a hypothetical example. A scientist is approached about giving an opinion on black holes for a show. After they are filmed, the title of the show turns out to be "black holes don't exist". The footage of the scientist is cut into snippets and a narrator makes comments and then out of context snippets from the scientist are inserted, making it sound like the scientist is backing the narrator up. This happens not only in films and documentaries, but in written articles for popular news and magazines.

I'm not saying this happens frequently, but it seems to happen a bit too often, and to varying degrees.

k. but that is only in your perspective. you don't know for sure if that's how it happened or not. so I am guessing there is no true way of knowing, is there?

 

[blank.black]

Some of them are probably really bad at finding appropriate ways to simplify what the theory says. And I assume that most of them don't know if it will be a good documentary or a bad one when they're being interviewed, so I don't think the fact that they agreed to be in it means anything.

to the general television audience it does mean a lot. pretty much all that they think they know about science is channels like History, Discovery, etc.

 

[Quantum-lept]

Fredrik,"You'd have to ask them, but I'm guessing that they're talking about the most distant objects we can see."

What if we were able to see or infer that the most distant objects were 30b light years or further? How would that effect your theory?

 

[Greylorn]

blank.black, here is a hypothetical example. A scientist is approached about giving an opinion on black holes for a show. After they are filmed, the title of the show turns out to be "black holes don't exist". The footage of the scientist is cut into snippets and a narrator makes comments and then out of context snippets from the scientist are inserted, making it sound like the scientist is backing the narrator up. This happens not only in films and documentaries, but in written articles for popular news and magazines.

I'm not saying this happens frequently, but it seems to happen a bit too often, and to varying degrees.

Would you deign to provide a specific example (i.e. "evidence) to support your assertion? Which program? I missed, "Black Holes Don't Exist," and cannot find out when it will be re-televised. Perhaps "Black Holes Don't Exist" did not exist.

I'd like to determine if this kind of thing "seems to happen," or actually happens. This should be easy for you, since all that is required is empirical data.

Easy enough. Name a channel and program title. Detail at least one error. Else admit that you've made an unsupported allegation.

 

[Evo]

Would you deign to provide a specific example (i.e. "evidence) to support your assertion? Which program? I missed, "Black Holes Don't Exist," and cannot find out when it will be re-televised. Perhaps "Black Holes Don't Exist" did not exist.

I'd like to determine if this kind of thing "seems to happen," or actually happens. This should be easy for you, since all that is required is empirical data.

Easy enough. Name a channel and program title. Detail at least one error. Else admit that you've made an unsupported allegation.

Re-read my post.

Also another member already gave an example.

Also, my "hypothetical" example was based on this. http://www.nytimes.com/2007/09/27/science/27expelled.html

But we're dragging the thread off topic.

 

[Fredrik]

What if we were able to see or infer that the most distant objects were 30b light years or further? How would that effect your theory?

Why would that change anything?

 

[Quantum-lept]

Quantum-lept ," What if we were able to see or infer that the most distant objects were 30b light years or further? How would that effect your theory?"


Fredrik,"Why would that change anything?"


Other than change the age of the universe, i don't know.

What would falsify your theory?

 

[Greylorn]

Re-read my post.

Also another member already gave an example.

Also, my "hypothetical" example was based on this. http://www.nytimes.com/2007/09/27/science/27expelled.html

But we're dragging the thread off topic.

Evo,
I reread your post and perused the link you provided. (I've never been a Ben Stein fan.) You are absolutely right.

Thank you for your reply. My question was inappropriate. Back to topic.

 

[petm1]

The shortest line back to big bang is centered in every atom. I am as close to the center of the universe "now" as any other form of matter, because the direction in time to big bang is the center connection we feel as mass. The longest lines in time to big bang are taken by photons. This is why I still feel that I am the center of my own visible universe while the Earth in the center of our one visible universe.

 

[Fredrik]

Other than change the age of the universe, i don't know.

Then why did you bring it up?

What would falsify your theory?

Is that a serious question? I suppose you could ask those guys what they meant. If many of them answer e.g. that there's a brick wall at the end of the universe, I'll concede that I was wrong (about what they meant).

 

[Quantum-lept]

Fredrik, I did not know..that is why i asked the questions...you know the math, you know your theory, it's history, strengths and weakness, i don't.

I have to take it on faith, and i don't do faith well.

If Darwin and others point out what will falsify their theory, then i assumed that every theory has an argument or evidence that will falsify it. Has nothing to do with what others believe or think if they can support their theories and those theories are not falsified.

I thought that is what science is, postulating a theory and trying to falsify it.

I only have theories based on what i observe and understand. These can be easily falsified because observation without specific knowledge is prone to error.

So, if there are no questionable variables in your mathematical models which no one has taken issue with, then it is a sound working theory and obviously beyond my understanding. I can only try.

And the center of the universe is not me..(:

 

[Fredrik]

I thought that is what science is, postulating a theory and trying to falsify it.

It is, but you must have lost track of what we were talking about very early in this exchange. I said that physicists who use the phrase "the edge of the universe" are probably talking about the most distant things we can see, and you questioned that with some very confusing comments. I see now that you at some point must have started talking about something completely different. I still don't know what.

 

[Chronos]

Ok, back to the original question, in case we lost track of that. We are at the temporal edge of the universe and the rest of it looks very smooth. Does that mean we reside at the center of the universe?

 

[Quantum-lept]

Ok, back to the original question, in case we lost track of that. We are at the temporal edge of the universe and the rest of it looks very smooth. Does that mean we reside at the center of the universe?

I'm questioning the mathematical models that come to conclusions that may at this time observably may be confirmed, but since there is still so much that we don't observe, require some faith to believe.

What if we observe that the universe goes back 100bly?
That would make the universe much, much older than we think it is now...If some mathematical model says it is 14bly, then observation or the model is in error.

There may not ever be a way to confirm if there is an edge to the universe other than a mathematical model, so that has to be tested and questioned and if a weakness is found, suspected as flawed beyond a certain point.

I just read that "singularities" are a problem...I have a problem with them too...The BB makes a ripping good yarn, gives people something to think about and have faith in, but singularities may be an invention because we can't see mathematically into the area that we are looking toward.

Another problem: Too many infinities...infinity this, infinity that...infinities piled into, onto, or otherwise associated with infinities...the universe may not be infinite. time may not be infinite..infinite mass, just a glitch in the math.

To say for certain that there is or is not an edge to a universe requires faith, or faith based science...for now, anyway.

 

[petm1]

We are at the temporal edge of the universe and the rest of it looks very smooth. Does that mean we reside at the center of the universe?

Yes when you think of visible universe, but no because the center is relative to each of us through our own center connection in time and not through space. In some ways time appears to be the boundary condition for all waves to a point.

Too many infinities...infinity this, infinity that...infinities piled into, onto, or otherwise associated with infinities...the universe may not be infinite. time may not be infinite..infinite mass, just a glitch in the math

Good thing we can keep it to finite numbers because we are seeing motion relative to each of us in time not just space.

 

[JediSouth]

Yes, that is what Halls of Ivy is saying, and I agree.

Yes, but WHERE IS THE STARTING POINT that everything starting moving away from

 

[Chronos]

Everywhere is the short answer. Since everything began at the initial 'singularity', every atom in the universe still thinks it is at the center.

 

[EinsteinII]

Welcome to PF. Imagine sitting on a high mountain. Turn around in every direction - in every direction, the Earth looks roughly the same. This is a good 2d analogy for the 3d space.

Everywhere we look in space, it looks about the same. This implies rather strongly that there is no center to the universe. And expansion need not require one: replace the Earth with a giant balloon, expanding, and the analogy still holds.

I need one more explanation. I think by this question our friend wants to know the location of Big Bang.. If that.. Do we have any clues as of now?

 

[petm1]

Everywhere is the short answer. Since everything began at the initial 'singularity', every atom in the universe still thinks it is at the center.

We see the atoms as separate pieces of this single event as for distance just think of redshift as a measure of time's dilation not just space's expansion after all relative they are one.

 

[Radrook]

Let's assume that our universe is one of the theoretical millions that are like soap bubbles in a vast endless sea. If so then it is finite. If finite that means it has a periphery. If it has a periphery then the distance from its peripheries inward until we achieve radius would give us its approximate center.

Multiverse Theory
http://www.makli.com/multiverse-theory-008210/

 

[Chronos]

We are at the temporal edge of the universe. No matter what direction we look, the rest of the universe appears more ancient [due to the finite speed of light]. Since it looks the same in every direction, it creates the illusion we are at the center. The same is true for any other observer in the universe. The concepts of 'center' or 'edge' of the universe are therefore irrelevant.

 

[Radrook]

We are at the temporal edge of the universe. No matter what direction we look, the rest of the universe appears more ancient [due to the finite speed of light]. Since it looks the same in every direction, it creates the illusion we are at the center. The same is true for any other observer in the universe. The concepts of 'center' or 'edge' of the universe are therefore irrelevant.

But does perception relative to position make a center impossible? Isn't that like saying that perception makes reality? Also, how does irrelevancy make reality any different? Isn't that simply a dismissal of the presently unknowable? Neither does inability to comprehend change reality. It merely proves inability to comprehend. We may be fish in a vast sea which seemingly has no center but the sea might indeed have a center despite our inability to see or comprehend where it is. If we say that the universe was infinitely small and suddenly appeared and expanded, then we create paradoxes. That is a fact. But to say that every single point on that expanding universe was and still is at its center, or that it was and is impossible for it to have a center is to postulate the impossible. If indeed it is impossible for our universe to have a center even though it is acknowledged to be finite then the reason why it i impossible has to be proven. Despite my extensive reading on the subject I have as yet not encountered a convincing or even an attempted explanation proving this supposed impossibility.

 

[Chronos]

Do you agree every observer in the universe perceives they are as far away as possible from the 'center' of the 'big bang', 'now'? [given the finite speed of light]?

 

[Radrook]

Do you agree every observer in the universe perceives they are as far away as possible from the 'center' of the 'big bang', 'now'? [given the finite speed of light]?

I agree that every observer sees the universe receding from his position. That doesn't justify the observer to conclude he holds the universal central position. It only proves that from his perspective it seems as if he does. Neither does it prove there is no central position. If indeed the relativity of perspective justifies concluding that no central position is possible then please explain how.

 

[Chronos]

Science is derived from observation. If it appears you are at the center of the universe, you must derive an experiment that attempts to disprove this theory. Lacking any such evidence means either you are at the center, or no center exists. We can say with fair certainty we are at the temporal edge of the universe, yet we observe the same distribution of galaxies [at large scales] in every direction. That too is compelling evidence the notion of any 'edge' to the universe is an illusion. An unbounded region has no 'center' according to the rules of geometry.

 

[DLuckyE]

Science is derived from observation. If it appears you are at the center of the universe, you must derive an experiment that attempts to disprove this theory. Lacking any such evidence means either you are at the center, or no center exists. We can say with fair certainty we are at the temporal edge of the universe, yet we observe the same distribution of galaxies [at large scales] in every direction. That too is compelling evidence the notion of any 'edge' to the universe is an illusion. An unbounded region has no 'center' according to the rules of geometry.

So basically, you're saying if I'm drifting somewhere in a big ocean and can see the distance of water to the horizon is equal in every direction I have to conclude that I'm either at the center of that there's no center to the ocean at all? That makes no sense at all... It just means that the ocean is bigger than your horizon and thus you can't determine if there's a center and if you're at that center.

 

[petm1]

Science is derived from observation. If it appears you are at the center of the universe, you must derive an experiment that attempts to disprove this theory. Lacking any such evidence means either you are at the center, or no center exists. We can say with fair certainty we are at the temporal edge of the universe, yet we observe the same distribution of galaxies [at large scales] in every direction. That too is compelling evidence the notion of any 'edge' to the universe is an illusion. An unbounded region has no 'center' according to the rules of geometry.

Unbounded may be what we "see", but bounded is what we feel. We are bounded by gravity which is a true center connection and the center of gravity is a real direction in time. Relative to my "now" the path back through time is inward opposite of the flow set into each atom. I "think" big bang was a little twist, a focal point of motion, because it formed our atoms, like a little focal point that broke into all of our dilating massive points. Time does not contract it is still dilating outward from big bang, and even though relative to my now I do not know where its center is in space, I "think" time's center was big bang the original dilating entity.

 

[bytecash]

This still does not make sense, there HAS to be a "center" of the Universe under the big bang theory, even if it is a ball or balloon blowing up, there is still a CENTER or middle of the ball or balloon. Even if there are no "edges" of the universe there is still a geometrical point of center. If the universe started from one point in space and expanded in all directions there is a center even if it is a moving central point.

 

[Greylorn]

IMO you are correct. Your analysis is one of others which expose the absurdity of Big Bang theory.

I can afford to agree with you because my theory of the beginnings, which would never be allowed here, does not incorporate a singularity (which would represent absurd physics, no different from claiming that God did it) and has a different explanation for both the observed expansion of the universe as well as its acceleration.

None of this will help you any unless I publish, but at least you know that you are not alone. Keep thinking!

 

[nonequilibrium]

This still does not make sense, there HAS to be a "center" of the Universe under the big bang theory, even if it is a ball or balloon blowing up, there is still a CENTER or middle of the ball or balloon. Even if there are no "edges" of the universe there is still a geometrical point of center. If the universe started from one point in space and expanded in all directions there is a center even if it is a moving central point.

I think you're simply misunderstanding the balloon analogy. The balloon actually tells the story for a two-dimensional universe. In that case the "center of the balloon" isn't a part of space at all! If people were to live in a 2D world, the balloon analogy would be exact (but then again, people in a 2D world can't imagine an inflating balloon, so they would use the analogy of a closed loop getting bigger).

Anyway, for our 3D spatial universe you have to inflate a "balloon" in 4D instead of 3D. You see that the "center of the balloon" isn't a part of our physical reality at all.

(To be exact, you'd probably need a 5D space, as time is an extra dimension, but that's besides the point in this discussion.)

 

[DaveC426913]

Anyway, for our 3D spatial universe you have to inflate a "balloon" in 4D instead of 3D. You see that the "center of the balloon" isn't a part of our physical reality at all.

(To be exact, you'd probably need a 5D space, as time is an extra dimension, but that's besides the point in this discussion.)

In fact, not only do you not need a 5th dimension, you do not even need a 4th. The mathematics of a curved 3D space work out just fine without needing to invoke a 4th dimension in the equations.

 

[nonequilibrium]

Hello Dave. Can it be that you misread my post? Otherwise I don't understand your objection. I was saying that the correct balloon analogy should be a 3 dimensional balloon in a 4 dimensional space (the 3D balloon then playing the role of our 3D space), but of course such an analogy would be useless due to not being able to imagine it :p

 

[DaveC426913]

Hello Dave. Can it be that you misread my post? Otherwise I don't understand your objection.

No, and I wasn't objecting.

Pointing out that the 2D balloon analogy is like our 3D universe expanding into a 4th dimension is tantamount to suggesting that our universe would have a center - in that 4th dimension. That is going to send bytecash the wrong message.

The balloon analogy is simply an analogy because it shows someone how it is possible to have an object that is finite yet has no centre. But you don't want to carry the analogy too far, or you defeat the lesson. We don't want bytecash thinking our universe has a center in some 4th dimension.

 

[Imax]

Expansion from a center is not compatible with the notion of a homogeneous and isotropic Universe. If the Universe did expand from a center, then the observed expansion rate would depend on how far you are from the center.

 

[Chronos]

What part of seeing the universe as it appeared in the past is escaping notice here?

 

[nonequilibrium]

The balloon analogy is simply an analogy because it shows someone how it is possible to have an object that is finite yet has no centre. But you don't want to carry the analogy too far, or you defeat the lesson. We don't want bytecash thinking our universe has a center in some 4th dimension.

True, I should have noted that, but bytecash's post seemed to suggest, at least to me, that he thought that our universe was actually expanding like the balloon does, i.e. as a 2D sphere expanding in 3D space, and that is why I wanted to point out that the balloon analogy was merely a substitute for something we can't imagine.

 

[petm1]

Do you agree every observer in the universe perceives they are as far away as possible from the 'center' of the 'big bang', 'now'? [given the finite speed of light]?

I agree with this. Do you think that every observer also perceives they are as close as possible to the 'center' of the 'big bang', 'now', given the finite speed of mass?

 

[salvestrom]

I was immensely please with myself when I finally got to grips with this question a few days ago. I think I deserved to be, having been struggling with it for two decades. =D

What I realized was that since the universal singularity consisted of all space and all matter/energy then that energy occupied all of space. So when it went up like an intergalactic roman candle, all energy was evenly distributed and blown apart. Essentially, the entire universe, at every point 'exploded'. While the universe, or more specifically, space may yet turn out to have a center, an edge, or neither, the location of the Big Bang itself was everywhere.