WMAP5 data is out, check implications for cosmology

[Martin]

All the papers are here

 

http://lambda.gsfc.nasa.gov/product/map/current/map_bibliography.cfm

[Bettina]

I still see Omega larger than one (1.0175) although slightly less than last time. (1.031). Is this correct?

 

Are they going to come right out and say for sure that our universe is flat?

 

Bee

[Realitycheck]

Where are all of the pictures?

[iNow]

Where are all of the pictures?

 

They're coming soon, of course.

[Martin]

I still see Omega larger than one (1.0175) although slightly less than last time. (1.031). Is this correct?

 

Are they going to come right out and say for sure that our universe is flat?

 

Bee

 

That is one end of a confidence interval. the news is that the confidence interval is 95 percent instead of 68 percent.

 

It has shrunk down some, plus it has gotten more confident.

 

I honestly have no hunch which way it will go. Personally I would like it to come out right around 1.01 , which is about halfway in the middle of the 95 percent confidence interval that they have on page 16 (buried in the data) namely something like [0.993, 1.018]

but that is wishful thinking and I really have no hunch.

[Dr. Jekyll]

How can they be so sure universe is flat? I mean, you need Omega to be exactly equal to 1. That is, we just need Omega=1+10^(-99)>1 for universe to be closed. It seems as it would be an impossible task to show empirically that Omega = 1 and we have a flat universe; or have I missed something?

 

How sensitive is the age of the universe with respect to Omega? Say we would have an Omega = 10, would then universe collapse after just a few million years?

[Martin]

the universe can be spatially closed (Omega > 1) and nevertheless expand forever.

 

the age of the universe, and the prospects for expanding indefinitely and avoiding collapse, are a separate issue because they appear to depend not only on Omega but also on Lambda (the dark energy or accelerating expansion feature)

 

other things (like Lambda) being equal, the lifetime of the universe is sensitive to Omega. you boggled my mind by postulating Omega = 10. I can't picture how that would have come about without the universe having collapsed at a very young age. can't give an intelligent answer. or I'm just too lazy to work it out.

 

==========================

they CAN'T be sure that the universe is flat----i.e. omega exactly = 1.

for one thing in science you never completely prove anything. ideas survive tests and confidence builds up, but they can always be overturned.

 

I would say that the DEFAULT assumption is spatial flatness because that is simplest, and the confidence interval is right close to one.

Mathematically, flat and infinite is slmpler than putting more stuff in the picture like what is the volume, what is the circumference, how much is it curved etc etc. So OCCAM favors flat.

The burden of proof is really on people who say it is not flat! We are the ones who have to show a confidence interval that is like 95 percent and does not include 1. We havent done this yet. So far the damned confidence interval includes 1 and even goes over into 0.99...territory (negative curvature). I shouldn't say we. I am a bystander. But I sympathize with those professional cosmologists who are interested in the possibility that space can be finite volume.

 

Bruce Basset, Joanna Dunkley, Ned Wright are all on record as having said that the possibility of positive curved finite volume should be taken into account and flat should not be simply assumed. They are reputable. Thinking on this is subject to gradual change.

[Dr. Jekyll]

One can't be 100% sure about anything really, I know I know, but they seem so confident in the flatness scenario. Don't know if Occam is such a good choice here, once upon a time earth was flat too!

 

It would be another thing if they measured, e.g., Omega = -1.56 +/- 0.005 or Omega = 1.32 +/- 0.005. Then you would be able to "be confident" in either hyperbolic or spherical geometry. But to rely on just a couple of decimals in the Omega = 1.0xyz scenario and then assume Omega=1.0000... seems quite erroneous.

 

This is not my area of research, but I think one must also consider the behaviour of the universe with respect to Omega, e.g., stability and sensitivity. That is, perhaps an Omega very close to 1 is needed for the universe to evolve in the way it has; or it would freeze or collapse early after creation. I have not seen any articles taking that into account (but I have not searched to any greater extent either). That is why I asked about how the magnitude of Omega impact the age of universe. If anyone got any links, please post.

 

edit/added

About the magnitude of Omega. The most recent I found, apart from the actual 5yr WMAP, is in this 2006 article http://arxiv.org/abs/astro-ph/0608632 we have [math]\Omega_{tot}=1.003 \pm 0.010[/math] while in the latest, actual 5yr WMAP we have [math]\Omega_{tot}=1.0052 \pm 0.0064,[/math] i.e., [math]0.9988\leq\Omega_{tot}\leq1.0116 [/math]. Perhaps it is in a bit of "favour" for a closed universe when comparing with old results.

[iNow]

<For the layperson, and otherwise interested specialist>

 

Want to know more about what is driving this research?

 

 

Check out this special from NOVA called "Origins," which originally aired July 2004:

 

http://www.pbs.org/wgbh/nova/origins/program-3114.html

[Martin]

<For the layperson, and otherwise interested specialist>

 

Want to know more about what is driving this research?

 

 

Check out this special from NOVA called "Origins," which originally aired July 2004:

 

http://www.pbs.org/wgbh/nova/origins/program-3114.html

 

iNow, I didn't watch the NOVA program, but would be interested in your impressions from watching it, or those of anyone else who did.

We probably didn't give enough attention to the WMAP5 report when it came out. Here is the relevant arxiv link:

 

http://arxiv.org/abs/0803.0547

 

Key people to look out for, who are co-authors here, are

 

Ned Wright, Joanna Dunkley, David Spergel, Charles Bennett,...

[Arch2008]

And for folks in a hurry, here is a brief but easy to understand summary where you don’t have to sound out every other word

http://www.oakland.edu/physics/mog32/mog32.pdf