WMAP: The Last Judgement

It seems the the Wilkinson Microwave Anisotropy Probe, or rather the estimable team of people working on it, have produced yet another set of maps and key results. I believe this will be the final release from WMAP. The paper is on the arXiv here and it represents a synthesis of no less than nine years of measurements of the cosmic microwave background radiation:

Here’s the abstract:

We present the final nine-year maps and basic results from the WMAP mission. We provide new nine-year full sky temperature maps that were processed to reduce the asymmetry of the effective beams. Temperature and polarization sky maps are examined to separate CMB anisotropy from foreground emission, and both types of signals are analyzed in detail. The WMAP mission has resulted in a highly constrained LCDM cosmological model with precise and accurate parameters in agreement with a host of other cosmological measurements. When WMAP data are combined with finer scale CMB, baryon acoustic oscillation, and Hubble constant measurements, we find that Big Bang nucleosynthesis is well supported and there is no compelling evidence for a non-standard number of neutrino species (3.26+/-0.35). The model fit also implies that the age of the universe is 13.772+/-0.059 Gyr, and the fit Hubble constant is H0 = 69.32+/-0.80 km/s/Mpc. Inflation is also supported: the fluctuations are adiabatic, with Gaussian random phases; the detection of a deviation of the scalar spectral index from unity reported earlier by WMAP now has high statistical significance (n_s = 0.9608+/-0.0080); and the universe is close to flat/Euclidean, Omega_k = -0.0027 (+0.0039/-0.0038). Overall, the WMAP mission has resulted in a reduction of the cosmological parameter volume by a factor of 68,000 for the standard six-parameter LCDM model, based on CMB data alone. For a model including tensors, the allowed seven-parameter volume has been reduced by a factor 117,000. Other cosmological observations are in accord with the CMB predictions, and the combined data reduces the cosmological parameter volume even further. With no significant anomalies and an adequate goodness-of-fit, the inflationary flat LCDM model and its precise and accurate parameters rooted in WMAP data stands as the standard model of cosmology.

The main reason for posting this is to acknowledge the remarkable impact WMAP has had on the field of cosmology. The standard model does indeed account for most available cosmological data extremely well. I’m not entirely sure about the “no significant anomalies” bit in the last sentence, in fact, but I won’t argue with it as it depends entirely upon what you mean by significant. It’s not exactly proven that the fluctuations have “random phases” either. We’ll just have to see whether data from Planck, due to be released next year, will reveal evidence of any physics beyond the standard framework WMAP did so much to establish.

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15 Responses to “WMAP: The Last Judgement”

  1. Note that a Hubble constant of 69.32 corresponds to an age of the universe of 13,975 GY in the case of linear expansion (i.e. lambda=0 and Omega=0), only slightly larger than the age of the universe mentioned above (though not within the (presumably one-sigma) uncertainty). Our universe, however, has both Omega and lambda significantly different from zero, and first had deceleration then acceleration. In other words, the average value of the deceleration parameter q up to now is very close to zero, being very small and positive. Since the universe is accelerating now, and has been for some time, q is negative, so this near coincidence holds only around the present time.

    I think it is reassuring that it looks like the two quantities are close but not the same. If they were very close, one might wonder whether it is not really a coincidence but has a deeper explanation. (On the other hand, within the uncertainties it looks like the universe could be exactly flat, though of course a slight deviation might never be observable.) I am thus inclined to believe that this is no more significant than the coincidence that the angular sizes of the Sun and the Moon are the same. In a short time (cosmologically speaking), cosmologists will find the Hubble time/age of the universe coincidence much more exact. Maybe all manner of theories will appear to explain this remarkable coincidence. Or, if the cosmologists know about the Earth and the Moon, some might point out that in the past there was a similar coincidence which even enables total solar eclipses and hence was accessible to all humans, not just cosmologists (and thus surely even more significant).

    Maybe Cusp will weigh in with his thoughts on this.

    As Mike Turner said, sometimes coincidences tell you something and sometime they don’t.

    For me, the most interesting question in classical cosmology at the moment, and one which Planck might answer, is whether the sum of lambda and Omega is definitively greater than or less than one. In other words, can we say for sure whether the universe is finite or infinite?

    • The answer to your last question is definitely “yes”.

      • At a conference in Melbourne in 1995, Bill Press said that someone knew the Hubble constant to two significant figures, but that he didn’t know who that person was. (Note for all the young dudes: Back then, viable values for the Hubble constant ranged from 30 (Hi Tom!) through 42 (yes; Alan Sandage wrote a paper saying that H=42 in the title) to more than 80, i.e. not even one significant figure. This was a decade-long debate. One can also measure the Hubble constant by measuring the time delay between images in a gravitational-lens system, hence Press and the Hubble constant at a gravitational-lens conference. A larger time delay means a lower Hubble constant. There was a similar debate regarding the correct value for the time delay in the first gravitational-lens system ever discovered, 0957+561. Press favoured a large value, and hence lower Hubble constant. The consensus is now that the shorter value, and hence higher Hubble constant, is correct. At this meeting, with Paul Schechter in the audience, Press introduced himself as the front end of the Press-Schechter horse.)

    • My comment is that when we measured in this paper


      we got that it equaled 0.0113 +- 0.0154, and we wrote “Thus, the fact that the average value of the deceleration parameter over the age of the universe is nearly zero for CDM, really is a “greater” coincidence then the well known “coincidence problem”.”

      When a get a moment, I will plug the new values in to see if I we still get a being statistically zero.

      ps – I was at the 1995 Melbourne conference also :)

      • Hmmm – it looks like using angle brackets screws things up…

        Try 2

        My comment is that when we measured the time averaged value of q(t) in this paper


        we got that it equaled 0.0113 +- 0.0154, and we wrote “Thus, the fact that the average value of the deceleration parameter over the age of the universe is nearly zero for CDM, really is a “greater” coincidence then the well known “coincidence problem”.”

        When a get a moment, I will plug the new values in to see if I we still get a time averaged value of q(t) being statistically zero.

        ps – I was at the 1995 Melbourne conference also :)

      • “Hmmm – it looks like using angle brackets screws things up…”

        Yes, <q> is an unknown tag in HTML and hence ignored.

      • Of course, as Master of the Universe, I am allowed to write such things. :-)

  2. Note that this companion paper has more emphasis on cosmology.

  3. Why we are so anxious about lambda and omega to calculate finite or infinite. Balloon inside balloon theory of matter and antimatter universe on opposite entropy path producing dark energy which is antigraviton and graviton for gravity at common boundary by annihilation is injected in both the universes for further necessary action . The question is not finite or infinite as stage is multiverse with infinite space but whether our universe is actually expanding ,though the galaxies flying away . More I will talk about if WMAP give some indication of this theory. At present CERN has found these two Higgs Bosons which I said as graviton and antigraviton which I said gravitoethertons in ether=gravity=darkenergy theory of gravitoethertons also. Read and enjoy and think differently.

  4. Monica Grady Says:

    So, now that we know the age of the universe, omega and the hubble constant to such precision (and, one hopes, accuracy), has cosmology finished? i.e., are all the questions answered….?

    • It was about a hundred years ago that the mass and charge of the electron were measured. But it is still not understood why elementary particles have the masses and charges they do. So, a hundred years ago was not the end of particle physics but rather the beginning. Perhaps something similar will happen in cosmology.

      Something which is already happening, similar to what happened a few decades ago in general relativity, is, after the basic questions have been answered, a split into people who work on very fundamental theory on the one hand and “applied physics” on the other. In GR, these are questions about loss of information in black holes, black-hole thermodynamics etc on the one hand and building gravitational-wave detectors on the other. In cosmology, there will be folks who will try to understand the numbers now that we have them and folks who will work on applications, both theoretical (i.e. simulations of structure formation) and observational (i.e. next-generation instruments/surveys such as SKA, LSST etc).

  5. The entire quantum physics and its theories should be checked in LHC . We have to develop New Physics if we think dark matter,dark energy and gravity is understood beyond Einstein.

  6. [...] one CMB satellite bows out, with the announcement of the final results form WMAP, the new year will see the rise of the next CMB experiment, Planck. You’ll still have to wait [...]

  7. Basic atomic model without strong and weak forces as postulated in two charge cloud theory with mono magnetic coupling is waiting for further investigation in CERN. The whole quantum physics is being reviewed now .

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