The Universe: Finite or Infinite?

[physalpha]

So

When we see the galaxy.

----Earth------------small gap light speed---------light speed -----above light speed--

----->||<-------------------->|<--------------------->|<----------------------------
============ red shift========== can not see============ never see=======
.........very small light speed...light go to the other side

visible lignt case
...O visible light
.....O infrared light
......O radio wave


Is this right?
?

 

[John232]

I would vote for finite but at the same time have the potential to expand indefentily. So it could be a certain size but then continue to expand larger forever. Like a beach ball that you could continue to blow up larger forever. The larger the universe gets the more dark energy would end up takeing over makeing the universe expand more and more as time progresses.

 

[Tanelorn]

Chalnoth can you please help me out here:


I have been able to understand and accept that galaxies just beyond the edge of our observable universe can recede from us at superluminous velocities, but I cannot think why they do not become effectively infinitely massive due to their relative velocity to us. What am I misunderstanding here?

Also if the universe is infinite in size then due to expansion galaxies would be moving at infinite speeds away from us, which makes the above situation even more strange.

Finally if the universe is in fact infinite in size, how can an infinite universe ever be finite let alone an infinitesimal inflatron singularity?

 

[Tanelorn]

Tried to answer the above questions myself and came across this theory that claims that even though both the universe's density (ρ) and its temperature (T) are shown to be larger in the past, it seems likely that these are purely relativistic affects and that at those times the measured values would be what they are today. Cosmological Special Relativity and Special relativity are not exclusive but work together, each being most significant under the right circumstances. Special relativity as v approaches c and Cosmological Special Relativity as t approaches τ.

http://creationwiki.org/Cosmological_relativity


This is an interesting paper discussing relativistic mass:

"We can thus tell our students with confidence that kinetic energy has weight, not just as a theoretical expectation, but as an experimental fact."

http://arxiv.org/PS_cache/gr-qc/pdf/9909/9909014v1.pdf


What is Relativistic Mass:

http://math.ucr.edu/home/baez/physics/Relativity/SR/mass.html



Is this statement correct: Most of the mass (protons and neutrons) comes from the relativitic mass of quarks.

 

[Chalnoth]

For the most part, we don't usually consider relativistic mass in relativity any longer, just the rest mass. The relativistic mass notation was largely dropped because it caused mistakes, instead taking mass to simply mean the rest mass, and allow energy to scale with velocity instead:

$$E = \gamma mc^2$$

This doesn't go against what Carlip said, mind you, because in this formulation gravity responds to energy, not mass, and inertia is similarly a function of energy instead of mass.

How does this mesh with far-away galaxies receding at faster than the speed of light? Well, the short answer is that the energy (or relativistic mass) of an object is an observer-dependent quantity. As an observer-dependent quantity, it shouldn't be any surprise that with some particular choices of coordinate system, the result is nonsensical.

In special relativity we are protected from such difficulties by the flatness of the space-time. But with space-time curvature, velocities of far-away objects become arbitrary, and thus carry no direct physical significance.