Stationary Centre of Universe Defined?

[AntiTelharsic]

For what it's worth...

I read "A Brief History of Time" and I didn't understand it. I read Einstein's work, and not only did I not understand it, but I spent a lot of time trying to argue against it because it didn't make sense. Eventually I realized that if I was ever going to have a hope of understanding this stuff, I would have to go to university and study mathematics and physics, and it was only after a few years of doing that that this stuff finally started making any sense at all.

There really is no way around it. Modern cosmology is an essentially mathematical subject. Its models, the very things physicists are talking about when they speak of "the universe", are mathematical objects which can only be discussed in the language in which they were formulated: mathematics. Every analogy you're given will fail, at some level, to convey precisely what is being researched and discussed. Reasoning in terms of those analogies, you will find yourself going down the wrong path the instant you start. Your understanding will always remain incomplete -- the subject will always fail to make sense -- unless you obtain the requisite mathematical knowledge.

Arguing against this stuff when one lacks the knowledge required even to correctly talk about it... well, that's what crackpots do. I was a teenage crackpot. I didn't understand relativity; I thought Einstein had to be wrong because his claims violated my "common sense". But arguing armed with nothing more than my own common sense wasn't doing me any good -- I wasn't increasing my own understanding, and I was certainly in no danger of refuting the claims I was arguing against. I was just talking a lot of crap, and I didn't even have the ability to realize it.

The only rational alternatives to that are to get the education so that your opinions can at least be informed, or defer to those who have. There's nothing wrong with saying "I don't understand this, but accept that the professionals know what they're talking about" -- the scientific method, and the fact that this knowledge can in principle be obtained by anyone and the claims can be tested, make that a reasonable thing to do. But refusing to accept it, claiming that it's woo, is to be a crackpot.

I don't know if there's much else I can contribute to this thread; I think I've answered the main questions to the best of my ability, and it's up to anyone else how much they want to take from that, and there are others who know more than me anyway. I sincerely wish you all the best, ynot, in your search for the answers, and I hope you take this post as sympathy, rather than criticism

 

[383LQ4SS]

Maybe I can pick up where Ynot left off as the foil of this thread.
I am still having a difficult time of grasping all of this, however I just got done watching a great video from the 2009 AAI conference where Lawrence Krauss gave a lecture titled "A Universe from Nothing". I was able to follow most of it fairly easily. But I did have a similar question to how Ynot phrased his original post. That question was:
Can we determine the location of the center of the universe?
An actual geographical center?

It seemed obvious to me that if we pick out a decent number of galaxies, find their trajectory and work backward from there that you would be able to at least point to the center of the universe?


According to Krauss' lecture and his great example of the expanding universe where he used two simple square graphs of 6x6 dots with one showing Time frame 1 and a second 6x6 square dot graph with each dot having a greater distance representing time frame 2 and then superimposing T1 over T2 with any dot aligned easily showed that ALL other dots are moving away from what ever dot you align over a given time. Meaning that no matter where you are in the universe...all other bodies are traveling away from you on average. Looking at it that way it seems that maybe you cant tell the actual trajectory of things like galaxies except...away from you. So I suppose there really is no "trajectory" at all? Just expansion?

But it still seems there should be some way to atleast find the "center of mass" of the universe using an alternate method?

 

[lionking]

Asking "what is the centre of the universe" is like asking "what's the edge of a sphere". I'm far from an expert, but I think most physicists believe that there is strong evidence that the universe is curved, and there is no "edge", and therefore no centre. I will be corrected if this is wrong.

 

[Dancing David]

If the Universe uniformly expanded from the point of the singularity then surely it follows that the expanded Universe is concentric to that point.

And this is where language breaks down, the 'point' that expanded is the 'universe'.

The universe did expand from a point, it is the point.

Excluding that singularities are not points.

 

[Brian-M]

Can we turn this around, and say that expanding space is logically equivalent to shrinking matter? Or is there some complication that invalidates this change in perspective?

 

[Myriad]

Can we turn this around, and say that expanding space is logically equivalent to shrinking matter? Or is there some complication that invalidates this change in perspective?

I've sometimes wondered that myself. But it's not just matter that would have to shrink. For instance, the wavelength of electromagnetic radiation would have to shrink in proportion, and since there's a relation between wavelength and the frequency and energy of that radiation, that (or maybe time?) would also have to shrink in some way. I think even if there could be a theory of shrinking "matter" mathematically equivalent to expanding space, it would be quite a bit more complex when stated that way.

Respectfully,
Myriad

 

[Perpetual Student]

I think my “problem” is that I don’t accept the language of theoretical or modern physics. Or at least I don‘t accept that the way it‘s often used. Not accepting doesn’t mean not understanding and isn‘t saying wrong. As far as I’m concerned a triangle is Euclidean and can’t be drawn on the surface of a sphere. If you want to draw three lines on the surface of a sphere I don’t accept that it’s valid to say you can draw a triangle that has three 90 degree angles. This is no more a triangle than three lines drawn around the circumference with no angles.

When considering modern physics, specifically relativity and quantum theory, we have developed models that fit observations. Older models (Euclid, Newton, etc.) were found to be lacking. So we have a limited number of choices: accept the newer models as reflecting reality; accept the newer models as better approximations than the older ones but with the hope that there exist yet to be discovered (or never to be discovered) even better models which do reflect reality; throw up our hands and say "it's hopeless -- we will never understand the universe." You may have some other choice in mind, but I doubt that it's likely to enlighten us further.

 

[Ryan O'Dine]

Just to add a little perspective, giving the universe a central point out from which it expands would be tantamount to introducing a "preferred frame of reference." That is, a reference frame which would be the same for everyone. A thoroughly Newtonian concept.

Discarding that very concept was one of the great and stunning triumphs of relativity theory. In other words, to insist the universe has a center is effectively to ditch huge, fundamental swaths of modern physics.

 

[Brian-M]

Ynot... I was just thinking; If you're adamant that the angles of a triangle must add up to 180 degrees, then exactly how would you draw a triangle on a curved surface? Would you bend the lines to compensate?

 

[AntiTelharsic]

Ynot... I was just thinking; If you're adamant that the angles of a triangle must add up to 180 degrees, then exactly how would you draw a triangle on a curved surface? Would you bend the lines to compensate?

I don't think he recognizes the label "triangle" as valid in that situation; however you did it, he wouldn't call it a "triangle".

ETA:

Ynot would say that a triangle must be a polygon with three sides which are straight line segments. Mathematicians, however, would generalize that idea to allow a triangle to have sides which are geodesic segments; there's no problem with this because, in the plane, geodesic segments are just straight lines. Meanwhile, generalizing in this way is so useful (for example, in astronomy and navigation) that I think being a stickler for the special case of terminology isn't of any benefit. It's certainly out of touch with well-established mathematics.

 

[sol invictus]

I don't think he recognizes the label "triangle" as valid in that situation; however you did it, he wouldn't call it a "triangle".

A triangle is a closed figure with 3 "straight" sides. In a curved space, a "straight line" means "the line marking the shortest distance between two endpoints". On the surface of a sphere, those lines are so-called great circles, and if you make a triangle out of them, the sum of its angles is greater than 180 degrees.

According to Einstein, if in a gravitational field you take three surveying tripods, beam lasers between them (which automatically follow the shortest path, so long as they aren't deflected by anything), and measure the three resulting angles with sufficient accuracy, you will find that the sum is not 180 degrees. In fact a century earlier Gauss did that experiment because he understood that there was no reason to think the result had to be 180. His equipment wasn't accurate enough to detect the effect, but it's there.

 

[sol invictus]

I've sometimes wondered that myself. But it's not just matter that would have to shrink. For instance, the wavelength of electromagnetic radiation would have to shrink in proportion, and since there's a relation between wavelength and the frequency and energy of that radiation, that (or maybe time?) would also have to shrink in some way. I think even if there could be a theory of shrinking "matter" mathematically equivalent to expanding space, it would be quite a bit more complex when stated that way.

Yes, that's exactly correct.

 

[AntiTelharsic]

Sorry to edit while you were replying, Sol -- just added a bit about geodesics, which I notice you touched on in your post

 

[sol invictus]

Just to add a little perspective, giving the universe a central point out from which it expands would be tantamount to introducing a "preferred frame of reference." That is, a reference frame which would be the same for everyone. A thoroughly Newtonian concept.

Discarding that very concept was one of the great and stunning triumphs of relativity theory. In other words, to insist the universe has a center is effectively to ditch huge, fundamental swaths of modern physics.

That's not really correct. The universe does not have a center, but it does have a preferred rest frame. There is a background of cosmic microwave radiation visible everywhere in the universe, and it defines a rest frame: only observers moving with the "right" velocity will observe it as isotropic, everyone else sees a dipole in it due to Doppler shift.

If you're bothered by the idea of the universe having a preferred rest frame, you shouldn't be. Take a slightly more familiar example: the laws of physics are rotationally invariant. Properly controlled experiments will give the same results regardless of which direction the experimental apparatus is oriented. Now look around you. Is what you see rotationally invariant?

Symmetries of the laws of physics are the central idea of modern physics. They are important because they give rise to conservation laws - conservation of angular momentum in the case of rotation invariance. But these symmetries do not imply that solutions to the equations of physics are invariant under them. (Instead, they imply that the action of such a symmetry on a solution will result in a new, different solution.) The only state that can be invariant under all symmetries is a completely empty vacuum, and the universe is not a vacuum.

 

[sol invictus]

Sorry to edit while you were replying, Sol -- just added a bit about geodesics, which I notice you touched on in your post

No problem. We said almost the same thing, it looks like.

 

[Rocko]

I think my “problem” is that I don’t accept the language of theoretical or modern physics. Or at least I don‘t accept that the way it‘s often used. Not accepting doesn’t mean not understanding and isn‘t saying wrong. As far as I’m concerned a triangle is Euclidean and can’t be drawn on the surface of a sphere. If you want to draw three lines on the surface of a sphere I don’t accept that it’s valid to say you can draw a triangle that has three 90 degree angles. This is no more a triangle than three lines drawn around the circumference with no angles.

I think the problem is that it appears you don't understand the language of theoretical or modern physics. That language is maths, and if you can't follow it then the best you're left with is people trying to explain things by analogy.

You seem to be rejecting the analogy as simplistic, but not engaging with the maths that actually describes it either.

 

[arthwollipot]

Plane geometry is just a special case of elliptical geometry - one where the curvature is zero.

 

[Dancing David]

Can we turn this around, and say that expanding space is logically equivalent to shrinking matter? Or is there some complication that invalidates this change in perspective?

I suppose you could but again the Hubble constant is there, why would matter shrink proportional to its distance from each other.

ETA: I am wrong.

 

[Towlie]

As far as I’m concerned a triangle is Euclidean and can’t be drawn on the surface of a sphere.

What should the Bermuda Triangle properly be called then?

 

[Ryan O'Dine]

That's not really correct. The universe does not have a center, but it does have a preferred rest frame. There is a background of cosmic microwave radiation visible everywhere in the universe, and it defines a rest frame: only observers moving with the "right" velocity will observe it as isotropic, everyone else sees a dipole in it due to Doppler shift.

Thanks for the correction. I do have another objection (to the OP) I think may be more to the point.

If the Big Bang had gone off like a stick of dynamite, with a definitive center, galaxies in different parts of the explosion would have signature redshifts dependent not just on distance, but on where in the explosion they were relative to us. In contradiction to what is observed.

(One out of two? )