Calculating the direction of the center of the universe?

[Throstur]

Calculating the direction of the "center" of the universe?

I've had a theory lingering in my consciousness for a long time.

I've wondered about the relevance between the speed of light, red-shift in stars and galaxies and relativity.

Although c is a constant, I have read somewhere that this constant has actually changed over time. I read it in one of those popular science magazines though so I'm not really sure what to make of it.

Anyway. Shouldn't it be theoretically possible to calculate the direction of the center of the universe using the speed of light?

The experiment would probably have to be done in space with a gigantic rig, but there's got to be some way to minimize the experiment. Basically, the rig would need to travel in one direction while shooting a beam of light in the same direction. This would be done in all directions. I don't know how we would measure the actual speed of those beams (maybe the technology is impossible or does not exist yet) but since the rig is moving in the direction that the beam of light is shot there should be a difference in the velocity when shooting in separate directions.

I find it really hard to explain in words since I studied astronomy in Icelandic. Basically, imagine someone on a pickup truck kicking the ball off in separate directions while the truck is driving, depending on the relative vectors, the difference in the velocity of the truck and the ball will differ.

Am I making any sense or am I confusing things and breaking the laws of physics?

 

[Cosmo Novice]

I've had a theory lingering in my consciousness for a long time.

I've wondered about the relevance between the speed of light, red-shift in stars and galaxies and relativity.

Although c is a constant, I have read somewhere that this constant has actually changed over time. I read it in one of those popular science magazines though so I'm not really sure what to make of it.

There is currently no evidence, observational or indirect, to suggest that C is a constant that changes over time - usually pop-sci tends to lean towards "cool" sounding ideas. This idea has been proposed, not just for c but also for other constants. G was proposed as a constant that changed over time. Most of these can be disproved by observational evidence.

Anyway. Shouldn't it be theoretically possible to calculate the direction of the center of the universe using the speed of light?

There is no center, or rather; there is a center, but the center is every point in spacetime. You may benefit from reading the balloon analogy. Essentially a center would indicate the BB was an "explosion" in an existing space - this is not the case. The BB, and more specifically t>0 was a period of rapid inflation followed by expansion, where spacetime pertubations (matter dense regions) began to clump and form the galaxies/clusters we see today. The matter dense region we occupied was pretty much where we are now (in galactic/cluster terms) give or take minor kinematic motion. To ask where is the center is akin to asking: "Where in our currently expanding reality, did reality begin?" or "Where is the center of reality?" The question is void - you cannot use a spacetime metric to answer a question of pre spacetime metric origin.

The experiment would probably have to be done in space with a gigantic rig, but there's got to be some way to minimize the experiment. Basically, the rig would need to travel in one direction while shooting a beam of light in the same direction. This would be done in all directions. I don't know how we would measure the actual speed of those beams (maybe the technology is impossible or does not exist yet) but since the rig is moving in the direction that the beam of light is shot there should be a difference in the velocity when shooting in separate directions.

The speed of light is invariant in all reference frames (in a vacuum) and this is one of the key postulates of Special Relativity. So it would not matter where you shoot a beam of light - the resultant constant c will be always be the same, as postulated in SR.

 

[D H]

There is no "center" of the universe. Alternatively, every point in the universe can be viewed as being the center of the universe. In other words, there is no center of the universe.

As far as the speed of light not being constant, that's pop sci journalism for ya. Real science is a bit too slow, a bit too boring to sell to the masses. Pop sci journalism tends to put far to much focus on fringe scientists. They're outlandish and exciting. That they are usually wrong is beside the point. They sell copy. Real science doesn't.

 

[Chronos]

Variable c creates more questions than it solves, which is generally considered a step in the wrong direction. For a good discussion of the implications of variable fundamental constants see:
http://arxiv.org/abs/hep-ph/0205340
The fundamental constants and their variation: observational status and theoretical motivations
Authors: Jean-Philippe Uzan (IAP, GReCO, Paris and LPT, Orsay)
Abstract: This article describes the various experimental bounds on the variation of the fundamental constants of nature. After a discussion on the role of fundamental constants, of their definition and link with metrology, the various constraints on the variation of the fine structure constant, the gravitational, weak and strong interactions couplings and the electron to proton mass ratio are reviewed. This review aims (1) to provide the basics of each measurement, (2) to show as clearly as possible why it constrains a given constant and (3) to point out the underlying hypotheses. Such an investigation is of importance to compare the different results, particularly in view of understanding the recent claims of the detections of a variation of the fine structure constant and of the electron to proton mass ratio in quasar absorption spectra. The theoretical models leading to the prediction of such variation are also reviewed, including Kaluza-Klein theories, string theories and other alternative theories and cosmological implications of these results are discussed. The links with the tests of general relativity are emphasized.
Comments: 56 pages, l7 figures, submitted to Rev. Mod. Phys
Subjects: High Energy Physics - Phenomenology (hep-ph); Astrophysics (astro-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
Journal reference: Rev.Mod.Phys.75:403,2003

 

[Cosmo Novice]

Variable c creates more questions than it solves, which is generally considered a step in the wrong direction. For a good discussion of the implications of variable fundamental constants see:
http://arxiv.org/abs/hep-ph/0205340
The fundamental constants and their variation: observational status and theoretical motivations
Authors: Jean-Philippe Uzan (IAP, GReCO, Paris and LPT, Orsay)
Abstract: This article describes the various experimental bounds on the variation of the fundamental constants of nature. After a discussion on the role of fundamental constants, of their definition and link with metrology, the various constraints on the variation of the fine structure constant, the gravitational, weak and strong interactions couplings and the electron to proton mass ratio are reviewed. This review aims (1) to provide the basics of each measurement, (2) to show as clearly as possible why it constrains a given constant and (3) to point out the underlying hypotheses. Such an investigation is of importance to compare the different results, particularly in view of understanding the recent claims of the detections of a variation of the fine structure constant and of the electron to proton mass ratio in quasar absorption spectra. The theoretical models leading to the prediction of such variation are also reviewed, including Kaluza-Klein theories, string theories and other alternative theories and cosmological implications of these results are discussed. The links with the tests of general relativity are emphasized.
Comments: 56 pages, l7 figures, submitted to Rev. Mod. Phys
Subjects: High Energy Physics - Phenomenology (hep-ph); Astrophysics (astro-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics - Theory (hep-th)
Journal reference: Rev.Mod.Phys.75:403,2003

Thanks for the link

 

[bcrowell]

We have a FAQ about the center of the universe: https://www.physicsforums.com/showthread.php?t=506991

 

[JeffKoch]

I've always had a hard time wrapping my head around this. I'll grant that there was no pre-existing "space" that we are familiar with or know anything about in which the BB occurred, but if our familiar three-dimensional universe is expanding then I can imagine picking a vector and following it along at infinite speed, and rather quickly finding myself near the edge of the expanding cloud of space, so that if I keep going I run out of... space. Or something like this. The whole of space that exists is undoubtedly vastly larger than the part of it that we have access to (roughly 14 billion light years in radius, though perhaps it's more complicated than just c*t), but unless space somehow wraps around itself as a balloon surface does, so that my vector will eventually hit me in the back of the head, I can't see how there isn't some kind of edge. We might have no data at all to tell us where we are in the greater universe, so all we see is the inside of our relatively small raisin cake, but I don't see why this preclude there being an "edge".

 

[bcrowell]

FAQ: Has the fine structure constant changed over cosmological timescales?

It has been claimed based on astronomical observations that the unitless fine-structure constant alpha=e^2/hbar*c actually varies over time, rather than being fixed.[Webb 2001] This claim is probably wrong, since later attempts to reproduce the observations failed.[Chand 2004] Rosenband et al.[Rosenband 2008] have done laboratory measurements that rule out a linear decrease of alpha with time large enough to be consistent with Webb's results.

Webb et al. have recently made even more extraordinary claims that the fine structure constant varies over the celestial sphere.[Webb 2010] Extraordinary claims require extraordinary proof, and Webb et al. have not supplied that; their results are at the margins of statistical significance compared to their random and systematic errors.

Even if their claims are correct, this is not evidence that c is changing, as is sometimes stated in the popular press. If an experiment is to test whether a fundamental constant is really constant, the constant must be unitless.[Duff 2002] If the fine-structure constant does vary, there is no empirical way to assign blame to c as opposed to hbar or e. John Baez has a nice web page discussing the unitless constants of nature.

J.K. Webb et al., 2000, "Further Evidence for Cosmological Evolution of the Fine Structure Constant," http://arxiv.org/abs/astro-ph/0012539v3

J.K. Webb et al., 2010, "Evidence for spatial variation of the fine structure constant," http://arxiv.org/abs/1008.3907

H. Chand et al., 2004, Astron. Astrophys. 417: 853, http://arxiv.org/abs/astro-ph/0401094

Srianand et al., 2004, Phys.Rev.Lett.92:121302, http://arxiv.org/abs/astro-ph/0402177

Duff, 2002, "Comment on time-variation of fundamental constants," http://arxiv.org/abs/hep-th/0208093

Baez, http://math.ucr.edu/home/baez/constants.html

Rosenband et al., 2008, 319 (5871): 1808-1812, http://www.sciencemag.org/content/319/5871/1808.abstract

 

[drollere]

There is no "center" of the universe. Alternatively, every point in the universe can be viewed as being the center of the universe. In other words, there is no center of the universe.

"center" is a term that follows after or only in relation to "boundary".

the focus on "boundary" leads naturally to the idea of a sign somewhere in space that says "end of space. sorry for the inconvenience." but then, what would be on the other side of the boundary?

if it's not space, then it can't be outside space, since "inside" and "outside" are spatial concepts. if it *is* space, then it's inside the universe, since space time is a property contained in the universe, like matter and energy.

there's a point where the questions wave good by to theory and facts and enter the domain of language traps. you can't answer language traps, you can only avoid them.

Pop sci journalism tends to put far to much focus on fringe scientists. They're outlandish and exciting. That they are usually wrong is beside the point. They sell copy. Real science doesn't.

and thereon hangs a sad tale with a sad moral.

 

[Lino]

Bcrowell, Thanks for the comments and the links in your posting. Now that things are one year on, do you know of any additional articles / papers that discuss the views of Webb et al (I have read an amount of "positive press" and I am really looking for alternative interpretations)?

Regards,

Noel.