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With WMAP now decommissioned and 'parked' in a solar orbit, the data analysis is going ahead for at least another two years (it should be the 9-year data set by then). The 7-year data set has just been released and although there are no very significant changes to the 5-year data1, I've spotted a quite subtle one. With the better accuracy now available on many (slightly revised) parameters, the minimum size of the total universe has doubled.
As I've shown in this 2008 Blog entry, the minimum diameter of the total universe was 800 Gly (billion light-years) at that time. Now it appears to have at least doubled, meaning the minimum volume has increased at least 8-fold. Not because of cosmic expansion, just due to tighter data tolerances.
Here's how it works. Out of the WMAP data comes the total density parameter2: Ω = 1 ± 0.03. Precisely one means a spatially flat (and potentially infinite) total universe. When smaller than 1, it means an open (also potentially infinite) total universe. However, when larger than 1, it indicates a spatially closed, finite universe, unbounded, but with no boundaries (like the surface of a sphere). The circumference of such a sphere represents the diameter of the 3-D universe, i.e., how far you have to travel to be in the same location that you have started from.
For Ω > 1, one can calculate the present radius of curvature of the cosmos. Take the present proper radius of the observable cosmos (45 Gly, the white circle)3 and divide it by √(Ω-1).4 This gives a radius of curvature of 45/√0.03 ≈ 260 Gly. Since we are interested in the circumference, we can multiply this by 2Pi, to get ≈ 1600 Gly. If the present universe would stop expanding abruptly, this is the minimum distance one would have to travel before you again end up where you started.
Since the universe is expanding, one can however never circumnavigate it, even if you had infinite time available. So, for all practical purposes, the total cosmos is infinite in size. Add to this that the probability for the density to be near 1.03 is quite small. It is much more likely to be closer to 1. The 95% confidence WMAP probability is Ω = 1 ± 0.01, giving a minimum circumference of around 3 trillion light-years.
As stated above, if Ω ≤ 1, the total cosmos may even be infinite today,
possibly because it started out infinite in size in the first place. I still hope that it will pan out to be a finite cosmos (Ω > 1) after all.5 It will be just that little bit less mind-bending. 
-J
1. I have updated the Cosmo-Calculator on my website with the new data. You can have a look at the 5-year data and the new 7-year data at the two links mentioned. Open them in separate tabs or windows for easy comparison. 7-year data from http://arxiv.org/abs/1001.4538
2. WMAP data gives the maximum values of the density parameters as: Ωm ≤ 0.29, ΩΛ ≤ 0.74, Ωtot ≤ Ωm + ΩΛ ≤ 1.03, where Ωm is the matter (normal and dark) density and ΩΛ is the vacuum energy density. We ignore radiation energy density, because when compared to the other two, it is negligible at present.
3. The yellow (28 Gly) circle shows the diameter of the observable cosmos in units of light-travel-time, not proper distance, like one would measure by a ruler.
4. It is clear that for Ω < 1, √(Ω-1) goes imaginary, signifying hyperbolic spatial curvature, like the surface of a saddle.
5. Edit: a closer look at the document http://arxiv.org/abs/1001.4538 referenced in 1 above indicates that a closed universe may indeed be slightly favored by the data. I have rounded to Ω = 1 ± 0.01, but what they say on page 17 is: 1 - 0.0084 ≤ Ω ≤ 1 + 0.0133, giving a statistical bias to the Ω > 1 case, if I'm not mistaken. It looks like a 60:40 distribution with a most-likely value at Ω ≈ 1.005. Not much, but still...
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Re: Cosmos now Bigger!
