Where is the center of the universe?


by JediSouth
Tags: universe
blank.black
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#55
Jul6-10, 11:45 PM
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Quote Quote by Evo View Post
Selective editing quite often completely changes what someone actually said.
huh?
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#56
Jul7-10, 03:47 AM
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Quote Quote by Fredrik
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.
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Jul7-10, 09:26 AM
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Quote Quote by blank.black View Post
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.
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Jul7-10, 10:13 AM
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Quote Quote by blank.black View Post
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?
Quote Quote by Fredrik View Post
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.
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#59
Jul7-10, 01:01 PM
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Quote Quote by Evo View Post
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
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#60
Jul7-10, 07:36 PM
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Quote Quote by Fredrik View Post
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.
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Jul7-10, 08:48 PM
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Quote Quote by Quantum-lept View Post
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.

Quote Quote by Quantum-lept View Post
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

Quote Quote by Quantum-lept View Post
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.

Quote Quote by Quantum-lept View Post
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.
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#62
Jul7-10, 11:56 PM
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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
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#63
Jul8-10, 02:30 AM
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Quote Quote by Evo View Post
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 thats how it happened or not. so im guessing there is no true way of knowing, is there?
blank.black
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#64
Jul8-10, 02:36 AM
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Quote Quote by Fredrik View Post
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
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#65
Jul8-10, 10:26 AM
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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
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#66
Jul9-10, 04:17 AM
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Quote Quote by Evo View Post
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.
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Jul9-10, 03:32 PM
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Quote Quote by Greylorn View Post
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/sc...7expelled.html

But we're dragging the thread off topic.
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#68
Jul9-10, 03:48 PM
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Quote Quote by Quantum-lept View Post
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
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#69
Jul9-10, 04:39 PM
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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
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#70
Jul10-10, 12:06 AM
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Quote Quote by Evo View Post
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/sc...7expelled.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
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#71
Jul10-10, 09:44 AM
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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
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#72
Jul10-10, 01:34 PM
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Quote Quote by Quantum-lept View Post
Other than change the age of the universe, i don't know.
Then why did you bring it up?

Quote Quote by Quantum-lept View Post
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).


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