WMAP data due out Thursday

[Martin]

starting Thursday I will be checking these websites

http://lambda.gsfc.nasa.gov/

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

 

right now the "current" site only has "first year data"---it should soon be updated to show "third year data"

 

the WMAP is the satellite at Earth-Sun L2 which gives us an accurate map of the Cosmic Microwave Background (CMB).

 

The three-year data from WMAP are due to be released this week, around Thursday 16 March.

 

Most of what we can say about cosmology---overall outlines of the universe---depends on measurements of the CMB. So it is a big deal.

 

People have been waiting for 3 years for this data. I have heard a lot of impatience and wild suspicions about why it hasnt been realeased sooner etc.

 

Probably it will only confirm the preliminary (first-year) data that was released some time ago. With some reduction in the error bars. But even just a few percent more accuracy could be interesting.

 

It is all tied up with the issue of whether or not the universe is spatially flat.

ultimately the new data will change estimates of the cosmological parameters like what you find here:

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

 

paramters like the age, and the hubble, and the percentage of dark matter and energy, and the Omega parameter that tells you how close to flat----right now it is given as 1.02 +/- 0.02

that is based on WMAP data released in 2003, still the best we have

and it would be nice if that 1.02 could be refined and the error narrowed down

 

anyway, keep an eye out for fresh WMAP data probably sometime this week, and some refinements in what we know about the cosmos

 

I will be disappointed if, after announcing they were going to, they dont release it---but I wont be the only one----there are people scheduled to give conference talks this month who count on being able to present the new data in their talks.

[bascule]

The CMBR freaks me out. Sadly the coolest thing I could think to do with the WMAP data is load it into Mathematica and spit out a sound file. Someone already did this with the data from WMAP's predicessor, I think (whichever one showed the CMBR is non-uniform)

 

A more precise estimate of omega would be awesome. I'm not really a big fan of the whole infinite flat thing...

[Bettina]

Want to take a guess? Mine is that they find its not flat.

 

Me

[Martin]

Want to take a guess? Mine is that they find its not flat.

 

Me

 

sure, I will take a guess. my guess is the same as yours actually. I think something like Omega = 1.02 +/- 0.01

 

I give zero credence to my guess because it is just a shot in the dark, not based on anything, but if I had to guess that would be it.

 

So that would put the true value most probably between 1.01 and 1.03

and the univese would be positive curved and spatially finite!

 

Bascule would be happy with that, I think. I would too---can't say why

 

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

 

it is also possible that the estimate of Omega will not change and that the new data will all be about things that most of us dont care about. or havent even heard of

I'm prepared to be disappointed but still I am hopeful they will narrow the error bars on Omega

 

another link to check on thursday:

http://map.gsfc.nasa.gov/m_mm.html

[Severian]

sure' date=' I will take a guess. my guess is the same as yours actually. I think something like Omega = 1.02 +/- 0.01

 

That would be consistant with a flat universe, so I am not sure what you mean?

 

If it is not exactly flat then you will have another fine tuning problem - why would it be so close to 1 if it is not equal to 1?

[Martin]

That would be consistant with a flat universe' date=' so I am not sure what you mean?

 

If it is not exactly flat then you will have another fine tuning problem - why would it be so close to 1 if it is not equal to 1?[/quote']

 

the results are due out tomorrow, so maybe we would do better to wait and discuss then

 

I want to stress that they may not come up with any change in the estimate of Omega----so I dont want to talk about it so much that we get our hopes up

 

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

 

just at the level of personal subjective feelings, for whatever they are worth, I'm happy to tell you mine

 

I am not worried by the appearance of this particular "fine tuning" problem. If the U is positive curved finite and almost flat, then all that means is that the curvature is a VERY SMALL number close to zero. Plausible mechanisms probably exist to make curvature small.

 

the cosmo constant Lambda is a much tougher case of fine tuning-----there it has to be not only very small but also NOT TOO small

that is where it gets hard to think of mechanisms that would result in the observed number

 

it is not enough for it just to be somewhere close to zero------Lambda has to be just SO close to zero and not any closer.

 

I am not saying that the value of Lambda won't eventually be explained, or the observations modeled some other way. I only mean that the problem is more formidable.

 

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

I can picture a flat infinite universe too, or some other kind of flat universe. Flat could certainly be the case and maybe that seems more reasonable to you, Severian.

I just happen to have a slight personal bias towards a finite world that is nearly, but not exactly, flat-----a bias which I will not defend, it is a matter of taste.

De gustibus non disputandum.

 

I would take the shift from the present Omega interval of 1.00 - 1.04

to an interval of 1.01 - 1.03

to be a good sign, and a step in the right direction

although since this is probabilities I would not take it as conclusive

[Severian]

Funnily enough I just posted about the Cosmological constant in Jim's thread. To explain further, you can just add a gravitational constant in my hand, just as Einstein did. Lets call that [math]\Lambda_0[/math]. But, since electroweak symmetry is broken the vaccum-energy associated with the Higgs field should also provide an effective contribution to the cosmological constant. when you work it out this contribution is

 

[math] \Lambda_H = (10^{19} {\rm ~GeV})^4 = 10^{76} {\rm ~GeV}^4[/math]

 

(10¹⁹ GeV is the Planck scale) so the total cosmological constant is

 

[math] \Lambda_{\rm tot} = \Lambda_0 + \Lambda_H[/math]

 

But we know that [math]\Lambda_{\rm tot} \sim 10^{-47} {\rm GeV}^4[/math] so we have to put in by hand a [math]\Lambda_0[/math] which has the opposite sign of [math]\Lambda_H[/math] but has the same magnitude up to the 123rd significant figure, where it must start to deviate.

 

This is incredibly hard to justify. Having the same magnitude exactly would be fine, (you just need a symmetry) so this was not a problem when the cosmological constant was zero, but getting it not quite zero is a big problem.

[Bettina]

Well???

 

Edit..... Ok, what does this mean in laywomens language. Are they saying they are more sure now that its flat?

 

http://lambda.gsfc.nasa.gov/product/map/dr2/pub_papers/threeyear/parameters/wmap_3yr_param.pdf

 

Bet

[Martin]

Well???

 

Edit..... Ok' date=' what does this mean in laywomens language. Are they saying they are more sure now that its flat?

 

http://lambda.gsfc.nasa.gov/product/map/dr2/pub_papers/threeyear/parameters/wmap_3yr_param.pdf

 

Bet[/quote']

 

Hi Bet,

 

thanks for letting me know the data was up. You saw it first. I will try to interpret some.

First of all for general readers there is a page with some press releases

 

http://map.gsfc.nasa.gov/m_mm.html

 

I dont know how useful that will actually be but I thought the graphic timeline was beautiful.

 

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

now looking at the paper by Spergel et al that you linked to.

 

I can't say for sure, but I will sort of guess my way along and maybe someone else with more confidence will come in and help. I think there is a trend more towards the pos-curved spatially finite picture.

 

One thing is look at page 48 figure 20. In a perfectly flat case the data should fall along that line marked flat. But the data do not. They go off on a somewhate different line.

 

I am still trying to figure out how to interpret a parameter they call "Omega-sub-K" or Omega_k

 

I think if this parameter is just slightly negative, what it means is that the curvature is just slightly positive.

 

I am very interested by the figure 17 on page 44. the number they call "w" is a technical thing called "dark energy equation of state" which we don't have to worry about----it relates the dark energy density to its (negative) pressure. Nearly everybody assumes that w = -1. but the data is now good enough that it can TELL something about w, and reassure people that it is, in fact, near -1.

 

the thing about figure 17 is that the data is good enough so that it can simultaneously tell us something about w and Omega_k.

 

It used to be that there was a trade-off and in order to estimate one thing you would have to make an assumption about something else. But with more and more data it begins to be much more satisfactory---the data constrains both at once, without having to assume so much.

 

Bet, I have been staring at this, and at page 50 Table 11. And I THINK it is saying that this Omega_k is NOT coming out zero the way it would in a spatially flat universe. I think they are saying that Omega_k is coming out slightly negative, as it should in a positive curved universe.

 

they are being very cautious, and balanced in what they say, as they SHOULD be, since it all involves observational error, error-bars, probabilities----lots of sources of uncertainty!

But I am not going to stress this. What I want is to get a feel for the drift of where the estimates are going.

 

here is a quote from page 50. I think the 15 is a typo, and should be 17:

 

"Figure 15 shows that by using the combination of CMB, large-scale structure and supernova data, we can simultaneously constrain both Omega_k and w. This figure confirms that our minimal model, Omega_k = 0 and w = −1 is consistent with the current data."

 

Omega_k = 0 means "flat". So they say the data is CONSISTENT with the simplest model of flat, and standard dark energy w = -1. OK so it does not yet disprove that simple model. It is not that far off yet, from the flat case. But it is SLIGHTLY off from the flat case. And as time goes on and more data has come in it seems that it gets MORE off from the flat case.

 

 

Another indication is in figure 21 on page 49

 

"..The panels show various combinations of WMAP and other data sets. While models with Omega_matter = 0.415 and Omega_{dark energy}=0.630 are a better fit to the WMAP three year data alone than the flat model, the combination of WMAP three year data and other astronomical data favors nearly flat cosmologies..."

 

 

To get the total Omega, what we were talking about, you add the Omega_m and the Omega_Lamda.

 

You add their 0.415 and their 0.630

this is just a rough estimate and I dont see the error-bar

but it looks like they are coming out with an Omega of 1.045

 

that is LARGER than the 2003 best estimate of 1.02

 

It still means NEARLY flat, and indeed AFAIK they still think it could be flat and are considering that case along with others

But the 1.045, if that is what is emerging from the data, is nevertheless more in the territory of a positive curved spatially finite

[Severian]

But the 1.045' date=' if that is what is emerging from the data, is nevertheless more in the territory of a positive curved spatially finite

[/quote']

 

Their quoted value of the spatial curvature is [math]\Omega_k = -0.015^{+0.020}_{-0.016}[/math] which means that they are still very consistant with a flat universe. (Even if the error was smaller than the deviation of the central value from zero, you must remember that these errors are 1 sigma deviations, so there is a 33% chance that the true value falls outside the error range.)

[Bettina]

I know people are still pointing to the universe being flat, but with new refined data, 1.045 still tilts the arrow farther away from flat. I know the number is small, but its still greater. So, whats next for Wmap.

 

And... when they talk about Omega, are they looking at our observable universe only?, or the global enivironment.

 

B

[Martin]

I know people are still pointing to the universe being flat' date=' but with new refined data, 1.045 still tilts the arrow farther away from flat. I know the number is small, but its still greater. So, whats next for Wmap.

 

And... when they talk about Omega, are they looking at our observable universe only?, or the global enivironment.

 

B[/quote']

 

I should not have said that 1.045:embarass:

 

we should listen to Severian. I was going out on a limb. I have to go back and try to understand this Omega-sub-k better

[Severian]

[math]\Omega_k[/math] is (I think) simply how much [math]\Omega_{\rm tot}[/math] is deviating from 1 (I think it is [math]\Omega_{tot}=1-\Omega_k[/math] but I would have to check...). So, it is showing more of a deviation than before, but it is not statistically significant.

[Martin]

thanks, I was suspecting that, but was not sure

 

so that is why the minus sign, it was the minus sign that was bothering me

Omega_k = 1 - Omega_total

 

because apparently a negative Omega_k

corresponds to positive curvature

 

now we seem to be in good shape

it is no big surprise or breakthrough, nothing to make headlines

but still a gradual improvement in what is known about Omega_k

[Bettina]

So what are you guys saying.... It shows less flat than before? I just want to know the comparison conclusion from 2003 to 2006.

 

B

[Martin]

So what are you guys saying.... It shows less flat than before? I just want to know the comparison conclusion from 2003 to 2006.

 

B

 

2003 said 1.02 +/- 0.02

 

what has changed is that there is now another decimal place

 

2006 says 1.015 with an error bar that is more precise' date=' see Sev's post.

He wrote [math']\Omega_k = -0.015^{+0.020}_{-0.016}[/math]

 

at first sight it looks like a retreat because 1.015 is less than 1.02

but remember that 1.015 ROUNDS to 1.02

the value comes in the extra decimal place

additional confidence and precision

 

I will translate what Sev gave into an interval

 

1.015 - 0.020 up to 1.015 + 0.016

 

doing the arithmetic that means

 

0.995 up to 1.031

 

still anything could be the case, but I like the added precision and it is definitely lopsided in favor of finite space. somehow this calls for a smiley:-)

[Bettina]

2003 said 1.02 +/- 0.02

 

what has changed is that there is now another decimal place

 

2006 says 1.015 with an error bar that is more precise' date=' see Sev's post.

He wrote [math']\Omega_k = -0.015^{+0.020}_{-0.016}[/math]

 

at first sight it looks like a retreat because 1.015 is less than 1.02

but remember that 1.015 ROUNDS to 1.02

the value comes in the extra decimal place

additional confidence and precision

 

I will translate what Sev gave into an interval

 

1.015 - 0.020 up to 1.015 + 0.016

 

doing the arithmetic that means

 

0.995 up to 1.031

 

still anything could be the case, but I like the added precision and it is definitely lopsided in favor of finite space. somehow this calls for a smiley:-)

 

 

0.995 up to 1.031

 

I don't know why my 97 pound body is happy that the uncomprehendable size of the universe is not flat. But I'm getting the chills. Is Wmap saying that the universe is closed? The big crunch is a possibility? There is hope of a rebirth? An oscillating universe?... Am I going to fast?

 

Bettina

[Martin]

 

Is Wmap saying that the universe is closed? The big crunch is a possibility?

 

Bettina

 

Wmap is not saying that big crunch is a possibility

 

since 1998' date=' when accelerating expansion was observed

the idea of big crunch has received less and less attention

 

accelerating expansion has been explained by postulating dark energy (which people dont really understand)

 

with that in the picture, you can have a spatially finite universe that keeps on expanding forever

 

and that is the most prevalent notion right now. I dont say it is right, or that the underlying mechanism is understood. It is just the prevailing picture in cosmology.

 

There is hope of a rebirth? An oscillating universe?... Am I going too fast?

 

for me, you are. I try to stay pretty close to the mainstream consensus in cosmology. It seems like enough to try to grasp

 

did you see that graphic timeline, looks like a horn made of galaxies and stars?

[Martin]

0.995 up to 1.031

 

I don't know why my 97 pound body is happy that the uncomprehendable size of the universe is not [infinite/]. But I'm getting the chills.

 

I can sympathize with this. You express it well.

[Bettina]

did you see that graphic timeline, looks like a horn made of galaxies and stars?

 

You bet I did. I printed it out and it looks awesome. If you know of a poster size anywhere let me know. If not, I'm going to see if any online poster makers can print one from the jpg I send them. I never saw anything done in that shape before..

 

On your other comments, yes, I wish too hard. I will take your advice and stay with the present model.... but I can dream.

 

B

[Martin]

If people want some wide-audience press coverage----besides the technical articles at the NASA site----here are a couple of things

 

Here is a NASA press release

 

http://www.nasa.gov/vision/universe/starsgalaxies/wmap_pol.html

 

Here is a Voice of America article that does a pretty good job

 

http://www.voanews.com/english/2006-03-17-voa16.cfm

 

 

The technical paper we have been discussing results from, in this thread, is by Spergel et al

 

 

 

Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology

 

 

http://lambda.gsfc.nasa.gov/product/map/dr2/pub_papers/threeyear/parameters/wmap_3yr_param.pdf

 

this is one of a handful of papers (5 or so) that will be published IIRC in Astrophysical Journal

[bascule]

Very cool. Thanks for the links, Martin.

 

I especially liked this quote:

 

Our species is one that seeks its origin, and the deepest of all questions of origin is, how did the universe begin? WMAP has certainly not answered this question, but WMAP's data is taking us one giant step closer to the answer by giving us a precise quantitative look at what happened literally at time zero itself

[Martin]

Hi Bascule, thanks for responding. the whole historic process of reading the microwave background is a fascinating one, I think. It is a slow process and this is just a step.

 

It involves a lot of waiting. going off and doing something else and coming back to see if they have turned up anything surprising. Listening for the other shoe.

 

I have no clairvoyance about what is going to turn up in this batch of data.

 

Have you heard about the socalled "axis of evil" the unlikely close alignment of the dipole and quadrupole anisotropies? I am a total non-expert about that----it would be nice if someone would explain it.

 

To me what looks like it should eventually attract some notice is figure 17 of page 43 of the "implications for cosmology" paper. I have printed out just that one page and it is lying around on my desk for me to scribble on and think about.

 

the blob is too far to the left. it puts Omega in the range 1.008-1.037

with 68 percent confidence (when Omega and the dark energy parameter w are both allowed to vary and both constrained by the data)

 

too far to the left to continue believing that space is flat (yet that is customarily assumed---and won't give up without a struggle)

 

but I could be focussing on the wrong thing----the data may hold other stuff that I dont know how to anticipate.

[bascule]

Hi Bascule, thanks for responding. the whole historic process of reading the microwave background is a fascinating one, I think. It is a slow process and this is just a step.

 

CMBR has fascinated me ever since I heard about it. I especially liked Tony Zee's idea that a "message from god" could be encoded into it, but sadly I guess the CMBR varies depending on what vantage from which you observe it

 

Have you heard about the socalled "axis of evil" the unlikely close alignment of the dipole and quadrupole anisotropies? I am a total non-expert about that----it would be nice if someone would explain it.

 

Actually I started a thread on it asking just that... for someone to explain what the hell it was all about. No takers

 

If what I think they're saying is true, and there is a pattern in the CMBR, then it would seem to make some good evidence for strong determinism, at least in my wacky world view. I was really fascinated in The Singularity is Near when Kurzweil described the universe as evolving like a Rule 110 cellular automaton, which is something I've kind of been playing around with in my head long before reading that book (I posted some threads about it before)

 

the blob is too far to the left. it puts Omega in the range 1.008-1.037

with 68 percent confidence (when Omega and the dark energy parameter w are both allowed to vary and both constrained by the data)

 

too far to the left to continue believing that space is flat (yet that is customarily assumed---and won't give up without a struggle)

 

An infinite flat universe never sat well with me, probably too much poking and prodding around inside of computers for so long make me think exclusively in discrete and finite terms. That and I think an infinite regression explanation of causality is really no better than the "There's a little man inside your head who has a little man inside his head who has a little man inside his head ad infinitum" approach to epistemology.

 

I'm of course a strong determinist so to me the universe represents an enormous quantum computer ticking away at solving some problem, and the more we figure out what the problem is (or for that matter, why the universe is solving it in the first place), the closer we'll come to understanding what the universe is really all about.

 

Well anyway, enough crazy ranting. I guess I just await the day when we look at those doting on the infinite heavens no differently than those who thought the Earth was flat. Or maybe I'm wrong, but for now, WMAP seems to agree

[aguy2]

Actually I started a thread on it asking just that... for someone to explain what the hell it was all about. No takers

bascule' date='

There was a taker, but you chose not to follow up on it.

Here is a site with some visuals (fig.3&4) of hydro pulses, that may prove helpful. http://www.physics.nmt.edu/~dynamo/PJRX/Results.html

 

My contention is that the visible universe is acting as if it is an ideal liquid [b']pulse[/b] that has transited from a laminar (even) flow to the presently observed turbulent condition.

 

aguy2