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Where is the center of the universe?

by JediSouth
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IanTBlack
#19
Jun23-10, 03:07 PM
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Why is it expanding at the same rate everywhere?
Lok
#20
Jun24-10, 03:40 AM
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Quote Quote by IanTBlack View Post
Why is it expanding at the same rate everywhere?
Because the overall density of the whole bigbang matter is thinning, and a relativistic view of this means time is accelerating and space is expanding. It is a twofold thing that results in acelerated expansion.
Fredrik
#21
Jun24-10, 05:01 AM
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Quote Quote by IanTBlack View Post
Why is it expanding at the same rate everywhere?
Because matter is distributed approximately the same everywhere. This is actually only true on large scales, but the same can also be said about the expansion. The solar system and the galaxy isn't expanding, at least not at the same rate as the cosmological expansion.
Mikeral
#22
Jun25-10, 02:08 PM
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What my impression of the discussion of the location of the center of the universe, would be look at it from another point of view. As a man on balloon looks around him, all he sees is a 2 dimensional plane with no possible to center to it. But when we take a look from outside the system, in a 3 dimensional point of view it is easy to find the center. Now since the human mind, like the balloon man has the concept of 2 dimensions, knows of only the concept of 3 dimensions, it would take an extra dimension to comprehend the shape of the world he lives in, the universe in our case. So in order to find the center of the universe we would have to expand our concept of 3 dimensions to include time and that the universe has a physical location but only at a specific time in existence, by that i mean, when all dimensions are at 0, like the center of the Cartesian plane, x,y and z are zero and time must be zero, therefore, the center of the universe exists at the big bang and disappears afterward.
Chronos
#23
Jun26-10, 01:24 AM
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This is a phishing expediton, imo. Either [A] earth is at the center of the universe, or [B] there is no center. Choose sides. Hint - [A] is indefensible.
Fredrik
#24
Jun26-10, 05:48 PM
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Quote Quote by Mikeral View Post
...therefore, the center of the universe exists at the big bang and disappears afterward.
The original big bang theory is just the claim that the properties of "space" changes with "time" as described by a FLRW solution. In those solutions, the phrase "at the big bang" doesn't make sense. These solutions only talk about times t>0, and at every value of the time coordinate t, the universe is homogeneous and isotropic. The big bang is the limit t→0.

There are more complicated "big bang theories" than the original, but as far as I know, none of them suggest that there was a center.
Donkeylip
#25
Jun27-10, 12:47 PM
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First time posting here. I'm by no means an authority on the subject, and my knowledge of physics is all in layman's terms, but here is my take on the question of a center of the universe.

First I think Mikeral was using the balloon metaphor correctly. I think it is more intended too explain the limitations of how we perceive the universe, not to explain how the universe actually works.

A better metaphor is a loaf of bread. Imagine you're baking a loaf of raisin bread. As you bake the bread the dough expands. The bread is the universe, and each raisin inside it is a galaxy/galaxy cluster. Now as the dough expands and the loaf gets bigger, every raisin would see all the other raisins moving away from it. It doesn't matter where the raisin is located, the effect is universal. This is why we see the universe expanding away from us, our cosmic loaf is expanding.

Now imagine that our loaf of bread started as an infinitely small ball of dough, just like the universe. If something is infinitely small then everything is at the center. This is the core of why it will be very hard to determine the physical center of the universe.

Because of the speed of light, the farther away from Earth we look, the farther back in time we are looking. We cannot look out into the present, we can only look out into the past. If the universe started as an infinitely small point where all of the matter in our universe was technically at the center, then if we look far enough away in ANY direction we will eventually see the "center" of the universe because 13+ billion years ago everything was at the center.

Assuming the universe is finite, we will never be able to see the "edge" of it because we can only look out into the past, not the present. Thus we will never be able to determine where the current physical center is. Since matter in the universe is spread out fairly evenly, my guess is that even if we could find the current center of the universe, there probably wouldn't be anything out of the ordinary going on there.

Sorry for the long post :)
Chronos
#26
Jun28-10, 03:28 AM
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Reminds me of one of my favorites - we are the most ancient object in the observable universe - which means we must be at the very edge. Still, everything looks pretty much the same in every direction, just younger. This is true no matter where [or when] you are in the universe. Every observer is forced to conclude they are both at the edge and the center of the universe - and neither conclusion is logical or valid.
Nickelodeon
#27
Jun30-10, 08:15 AM
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Quote Quote by Chronos View Post
This is a phishing expediton, imo. Either [A] earth is at the center of the universe, or [B] there is no center. Choose sides. Hint - [A] is indefensible.
What about [C]?

[C] could be that the red shift is caused by something other than a distance galaxy speed of recession
IanTBlack
#28
Jun30-10, 11:24 PM
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I suppose that on a larger scale it would make sense.
Greylorn
#29
Jul1-10, 01:37 AM
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Quote Quote by russ_watters View Post
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 do not believe that either the mountaintop or balloon analogy is applicable to the problem. Would not the analogy of an explosion be more appropriate, since the Big Bang was an explosion?

Explosions have centers of origin. They can be located after the fact.
russ_watters
#30
Jul1-10, 01:42 AM
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Quote Quote by Greylorn View Post
I do not believe that either the mountaintop or balloon analogy is applicable to the problem. Would not the analogy of an explosion be more appropriate, since the Big Bang was an explosion?
No. The explosion analogy is not appropriate precisely because the Big Bang was not an explosion. That's a pop-media misconception.
Greylorn
#31
Jul1-10, 04:25 PM
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Quote Quote by russ_watters View Post
No. The explosion analogy is not appropriate precisely because the Big Bang was not an explosion. That's a pop-media misconception.
Russ,
Thank you for your reply. I confess to having active subscriptions to pop-sci magazines, and nonetheless hope that you will readdress this issue,

Between 1965 and 1979 I did pioneering work in applying computer to technology, beginning with instrumentation and pointing control for the first space telescope and first ground based totally computer controlled instrument. My degree is simply a B.S. in physics, but I do have a minor paper on variable stars, co-authored of course. I read, learn, and argue, and during this time was seriously interested in the then-unresolved conflict between Hoyle's and LeMaitre's theories. (I have a yellowed paperback copy of Gamow's Creation of the Universe, deep in storage because I regarded most of it as unsupportable, illogical bunk.)

I never found either the steady-state or big-bang theory sufficiently logical to adopt, and never felt that it was necessary to choose between two opposing fallacies. I've kept track of the evolution of Big Bang theory as it rose to ascendancy. Until around the turn of the century, its precursor was regarded as very tiny "particle" containing all the mass/energy of the current universe.

That was an absurd and unprovable notion from the outset, and I angered many a righteous astronomer explaining why. But sure enough, eventually cosmologists figured out the same thing, and solved the problem by renaming their cosmic micro-pea (which, back then, had acccording to theory, blown up), a physical singularity.

Now since I've written pointing code for telescopes, I know what a mathematical singularity is. But a physical singularity is, in my not very humble opinion, invented nonsense. Its parallel in human thought is the omnipotent infinite God concept.

Of course you are correct, that the Big Bang could not have been an explosion, because a "physical singularity" cannot do anything, much less explode.

But, if the "singularity" did not explode, what have you renamed what it actually did? Inflated? Really?

Best I can tell, the expansion velocities of post-bang matter are sufficient to make a thermonuclear bomb analogous, by comparison, to the result of a drunken college student igniting his fart.

Most of us would call a really awesome explosion, at the very least, a "Big Explosion." Few would dub it inflation. I've inflated rubber boats, kiddie pools, and truck tires. I've set off firecrackers and tickled some dry nitrogen tri-iodide. I know the difference. When did Orwellian linguistics creep into astrophysics? More importantly, why?

Can we have a real discussion about this? Can anyone out there consider the possibility that current Big Bang theory is on a level with religious dogma, and that there must be a better explanation?
Heisenberg.
#32
Jul1-10, 05:29 PM
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Quote Quote by Greylorn View Post
Best I can tell, the expansion velocities of post-bang matter are sufficient to make a thermonuclear bomb analogous, by comparison, to the result of a drunken college student igniting his fart.
hmm I have a quick question - if we make the big bang analogous to a huge explosion, then would that not that contradict the uniformity of the universe? A popular example of showing how the universe is a little different from the common definition of "explosion" is dropping a balloon full of paint - it splatters everywhere - with random blobs of paint clumped together, not a uniform filled in circle of the paint. From what I have heard the reason why the difference is imperative is our universe would be a very different picture if it was in fact an "explosion", for it would contradict evidence such as wmap, no?.. pardon my ineptness if my comments are incorrect or if I have misunderstood your post.
Greylorn
#33
Jul2-10, 02:23 AM
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Quote Quote by Heisenberg. View Post
hmm I have a quick question - if we make the big bang analogous to a huge explosion, then would that not that contradict the uniformity of the universe? A popular example of showing how the universe is a little different from the common definition of "explosion" is dropping a balloon full of paint - it splatters everywhere - with random blobs of paint clumped together, not a uniform filled in circle of the paint. From what I have heard the reason why the difference is imperative is our universe would be a very different picture if it was in fact an "explosion", for it would contradict evidence such as wmap, no?.. pardon my ineptness if my comments are incorrect or if I have misunderstood your post.
The paint balloon analogy does not seem to fit. When the balloon hits the ground, it is subject to asymmetrical forces. The bottom will likely break while the top is intact. The paint will be emerging from a non-spherical container which flexes in process. Shards of rubber block the flow of paint.

A more approximate analogy might be a perfect sphere of paint sitting in deep space, with a tiny symmetrical explosive charge placed at its center that releases its energy in about 10exp-40 second. I suspect that this would produce an evenly distributed pattern of paint.

As for the WMAP images, I've looked at them again and again and keep wondering why astrophysicists insist that they show a symmetrical energy distribution. There are blobs and lumps all over the place. I make it a point to keep in practice recognizing such things by studying a centerfold image monthly. Haven't lost my skills. The WMAP images look to me like the result of a sloppy, asymmetrical paint balloon explosion.

Thanks for your reply. Please don't worry about sharing your thoughts with me. I don't treat PF like a physics class where the answers are in the professor's private supplementary text. The PF is a place where awesome ideas could be formed if people share their honest thoughts and best ideas, post interesting questions and expect a variety of answers.
Chronos
#34
Jul2-10, 02:58 AM
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Science relies on observational evidence to formulate theory. The big bang concept is supported by a vast body of observational evidence. Liking the evidence is optional. The burden is on dissenters to formulate a theory that more cleanly fits observation.
Ich
#35
Jul2-10, 06:03 AM
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I make it a point to keep in practice recognizing such things by studying a centerfold image monthly.
Which kind of journal, if I may ask? And which kind of practice?
Haven't lost my skills. The WMAP images look to me like the result of a sloppy, asymmetrical paint balloon explosion.
Yeah, great. Maybe sometimes you'll find the scale of these false color pictures. Try this one for a start..
Greylorn
#36
Jul2-10, 07:04 PM
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Quote Quote by Ich View Post
Yeah, great. Maybe sometimes you'll find the scale of these false color pictures. Try this one for a start..
Awesome link! Thank you! There is obviously more I can learn there before coming back on this issue. So, I will be getting back to studying.

Back in '75 when we were developing the imaging technology, we called it pseudo-color. "False color" is upfront and honest.

It never occurred to me to check the scale, which was stupid. (Of me, not the scale.) A difference of 0.018% seems downright negligible.

One curiosity, which I did not find answered on the page--- Is the low effect of galactic emission the result of a limited instrumentation bandwidth?

I appreciate your assistance and sense of humor, equally welcome.


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