Size of the Universe

1. Nov 10, 2005

Critical_Pedagogy

Anyone care to guess the size/diameter of the Universe?

Somehow I think we live in a Universe with extra dimensions, and we'd be fooling ourselves to guess the Universe's size because we don't even know it's shape.

Last edited: Nov 10, 2005
2. Nov 10, 2005

Phobos

Staff Emeritus
In 3 dimensions, I'll go with unbounded/infinite.
I'll reserve judgement on the possibility of additional dimensions until more evidence is in.

3. Nov 10, 2005

EL

What do you mean with "diameter" of the universe? Twice the curvature radius or what?

Anyway, my guess is infinite.

4. Nov 10, 2005

hellfire

The lack of patterns over a specific angular separation in the CMB map lead Neil Cornish to the conclusion that the universe must be at least 24 Gpc in diameter, see this. My vote goes to a finite closed universe, with a curvature radius considerably greater than the radius of the observable universe.

5. Nov 10, 2005

hossi

finite

My guess is it is finite with non-compactified extra dimensions. Now that requires an explanation where the extra dimensions are. I think that is interesting. I don't particularly like the Randall-Sundrum II model. Does anyone know of other possibilities for infinite extra dimensions?

Take Care,

Sabine

6. Nov 10, 2005

turbo

Unbounded and infinite, both spacially and temporally.

7. Nov 10, 2005

vincentm

Isn't the universe in a current state of expansion?

8. Nov 10, 2005

SpaceTiger

Staff Emeritus
That's correct, but there's no good reason to suppose a spatially infinite universe can't expand. As for turbo, he doesn't believe in expansion, but that idea pretty far out of the mainstream by now.

I think our universe is probably finite. I wouldn't try to even guess whether or not there is an infinite multiverse.

Edit: Generalized response, wasn't sure who vincent was responding to.

Last edited: Nov 10, 2005
9. Nov 10, 2005

turbo

I do not believe in cosmological expansion, and I do not expect you to expound upon this or support this idea in any way. It would be nice however if you would acknowledge that prior to Penzias and Wilson's discovery of the CMB radiation (already predicted by Eddington and many others dating about 60 years earlier in the Steady State model), Gamow had refined his prediction to 50 deg K, and this prediction was refuted, as Eddington's was confirmed. The measurement of the CMB was a confirmation of the SS model and a falsification of the BB model, although you would not know that from all the flak surrounding concordance cosmoology today.

10. Nov 11, 2005

SpaceTiger

Staff Emeritus
See

http://www.astro.ucla.edu/~wright/Eddington-T0.html" [Broken]

He predicts a radiation background with an effective temperature (i.e. one obtained by considering the energy density of the radiation) of 3.18 K by integrating the starlight in our galaxy. If one were to neglect dust and do a similar calculation today, one would get a similar result, so he wasn't entirely wrong. The problem is that it didn't predict the CMB, which lies in an entirely different part of the electromagnetic spectrum.

Last edited by a moderator: May 2, 2017
11. Nov 11, 2005

Chronos

I can't resist that bait, turbo. Getting the right answer is meaningless without getting it for the right reasons. Eddington himself admitted his reasoning was wrong in predicting the CMB temperature. This has been discussed before on PF. It is true Gamow came up with a less accurate prediction, but his reasoning was rock solid. This is why he got credit, and Eddington did not... at least in scientific circles. In my, and many other minds, it boils down to choosing between clairvoyance and science.