Why do photons naturally travel at c?

[jcsd]

Compared to whatever neighbourhood of c you can suggest. What is the right word, if not collapse?

AM

Collapse implie ssome sort of catastrohic/irrevrsible process, thoguh I suppose you use it in the sense of fold-up, to convey the fact taht most of the stars you would see would appear in a very narrow area.

 

[donjennix]

I apologize in advance for making an assumption --- but in another thread the writer seemed to be understandably confused by the famous balloon model where the galaxies are spots on the expanding balloon. You can get the impression that the universe IS the balloon and the center is the center of the balloon. But as jcsd points out, you have to consider the universe as the SURFACE of the balloon. If the center of the balloon exists, it is in hyperspace or some such; and, just like there is no "center" of the surface of the world, obviously there is no center to such a universe ... unless you take the trivial case that the "center" is where ever I am now. If you add to that the fact that the universe does not seem to have the curvature of a sphere (I can't rremember if that is positive or negative) and you get even more complications.

 

[Andrew Mason]

You can get the impression that the universe IS the balloon and the center is the center of the balloon. But as jcsd points out, you have to consider the universe as the SURFACE of the balloon. If the center of the balloon exists, it is in hyperspace or some such; and, just like there is no "center" of the surface of the world, obviously there is no center to such a universe ... unless you take the trivial case that the "center" is where ever I am now. If you add to that the fact that the universe does not seem to have the curvature of a sphere (I can't rremember if that is positive or negative) and you get even more complications.

I am talking about the 3 dimensional 'slice' that exists for each frame of reference and which we see (as would all other observers sharing our reference frame) as our spatial universe. That universe has a centre. I am not saying it is an absolute centre because other observers in other reference frames would disagree. But all observers in our reference frame would agree where the centre is located (assuming that we could do all the necessary measurements).

AM

 

[Garth]

I am talking about the 3 dimensional 'slice' that exists for each frame of reference and which we see (as would all other observers sharing our reference frame) as our spatial universe. That universe has a centre.

The standard cosmological models are unbounded, so the universe we observe has no centre, except that of the observer herself (Copernicus eat you heart out!).

Garth

 

[jcsd]

I am talking about the 3 dimensional 'slice' that exists for each frame of reference and which we see (as would all other observers sharing our reference frame) as our spatial universe. That universe has a centre. I am not saying it is an absolute centre because other observers in other reference frames would disagree. But all observers in our reference frame would agree where the centre is located (assuming that we could do all the necessary measurements).

AM

Yes we are talking about spatial slices, infact the discussion of the sphere fits in well with the spatial slice of the case of the RW metric which describes a finite universe which is essentially a 3-sphere (i.e. the surface of a four-dimensional sphere).

As Garth says the Copernican cosmological principle is a pretty fundamantal assumpion in neraly all areas of cosmology and a geometric cnetre is a total violation of this principal.

 

[Rob Woodside]

Tuning in top the couple of posts only, I would point out the democracy of homogeneous and isotropic spaces. Every point can be taken as the centre of the space. The homogeneity and isotropy destroy any uniqueness that "the centre of the universe" might otherwise have.

 

[T.Roc]

hmm,

No one mentioned that the frequency and wavelength values of light are produced by the natural harmonic numbers of simple oscillation. There is always symmetry between values whose product is c.

TRoc