Cosmology Results from Planck Tomorrow

The Planck satellite, a European cosmic microwave background observatory, was launched in 2009 and is finally ready to release its first set of cosmology results. (It has already released findings on galaxies and dust and so forth — what early-universe cosmologists call “foregrounds” and others call “my life’s work.”) They will be showing us the highest-precision all-sky map of the microwave background ever made. The announcement starts at 10 a.m. Paris time, which works out to 2 a.m. Los Angeles time. Don’t expect me to be live-blogging.

So what should we be looking for? Typically an experiment like this isn’t just a fishing expedition; scientists have a pretty clear idea of what questions they would like answered, and what discoveries they might be able to make. Nature is always capable of surprising us, of course. There are some very useful posts on this question by Renee Hlozek and Shaun Hotchkiss. (I hope everyone reading those posts will take a moment to appreciate how wonderful it is that we live in an era where real experts can chime in directly on important scientific questions.)

A CMB map contains an enormous amount of information, especially if you are measuring the polarization as well as the temperature at each point. My understanding is that this edition of the Planck results will not include polarization, but that will be coming some day down the road. (And Max Tegmark’s $100 is safe for another few months.) Nevertheless, a lot of the interesting information boils down to the “power spectrum,” which tells us how strongly the temperature varies on different angular scales. Of course, there are a few observables that go beyond the power spectrum, and those are some of the most interesting ones.

Here are some of the major things cosmologists might want to learn from the CMB temperature anisotropies:

  • Did the original perturbations we inherited from the early universe have the same amplitude on all scales, or were the slightly different?
  • What are the best fits for cosmological parameters such as the density of dark matter and dark energy, the numbers and masses of neutrinos, and the Hubble constant? Or even spatial curvature?
  • Are there persistent “anomalies” that can’t be easily accounted for by a simple theory of primordial perturbations? For example, do the anisotropies somehow define a preferred axis in space?
  • Are the perturbations completely random — “Gaussian” — or are there hints of primordial non-Gaussianity, which might help pin down specific models of inflation?

I suspect it would be wise to keep expectations low for Earth-shattering (or universe-shattering) discoveries here, although I’d certainly welcome a surprise. The amplitude of the primordial perturbations has already been nailed down fairly well, by the Atacama Cosmology Telescope as well as by the South Pole Telescope that I blogged about. From Renee’s post, here is a graph of the data from the WMAP satellite as well as ACT and SPT, which as you can see are pretty compatible with each other as well as with the theoretical prediction. We might get a more definite finding that the amplitudes aren’t strictly the same at all scales, which would be good news for proponents of inflation.


We definitely hope to get more precise measurements of cosmological parameters, especially the number of neutrino species and their masses. Evidence from particle physics experiments here on the ground is inconclusive when it comes to the number of neutrino species — very recent results from the MiniBooNE experiment seem to point in the direction of sterile neutrinos that don’t feel the weak interactions. If such neutrinos are produced in the early universe, they could have an effect on the CMB anisotropies. Obviously any definitive statement that there were more than three kinds of neutrinos would be huge news. The other hope for groundbreaking news would be the discovery of nonzero spatial curvature, but nobody really expects that.

As far as anomalies are concerned, Planck has a very different scanning strategy than WMAP had, so it’s possible that it will squelch some people’s favorite anomalies. But there is the problem of cosmic variance (in the original sense) — on very large scales, there is a limited number of modes we can measure, since we only get one universe. If large-scale fluctuations just happen to be statistically anomalous, it might be very difficult to ever decide whether it’s an accident or the sign of new physics.

The search for non-Gaussianities (correlations between fluctuations on different scales) is possibly the most interesting thing we should be looking at in the current release. If inflation is right, you may or may not see deviations from perfectly Gaussian behavior, depending on the kind of inflation we’re talking about. Roughly speaking, we expect perturbations to be Gaussian in simple models of inflation with ordinary dynamics of a single scalar field, but adding bells and whistles to your inflationary model can introduce some non-Gaussianities. So it’s not really evidence for or against inflation, but limits the model space if inflation is the right answer.

Let’s offer early congratulations to the Planck team, who have certainly worked incredibly hard to get to this point.

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20 Responses to Cosmology Results from Planck Tomorrow

  1. Pingback: Allgemeines Live-Blog vom 18. bis 20. März 2013 | Skyweek Zwei Punkt Null

  2. Chemicalscum says:

    What about possible evidence in the CMB for collisions with other inflationary bubble universes as proposed by Aquirre?

  3. Sean Carroll says:

    Good point, actually. We could also find evidence for circles in the sky, cosmic strings, or other more exotic anomalies. Often, however, these are left up to post-data-release analyses by other teams, rather than being addressed in the first papers.

  4. James Gallagher says:

    Not a brilliant outcome for inflation models (with the enhanced anomalies).

    Could 2013 be the year where both SUSY and Inflation start to decline in popularity due to big bad Nature just not playing game?

    (It will make the Milner Prizes look embarrassing in retrospect)

  5. Sean,

    Do you answer questions from visitors???


  6. Sean Carroll says:

    David– Generally not. Given time constraints, I use the blog to talk about whatever happens to be on my mind at the time.

  7. CoffeeCupContrails says:

    @DavidDoggett HAH! I see what you did there 😀

  8. Charles Sven says:

    This relic radiation supports a Big Bang conversion of Dark Energy into matter as demonstrated by Stanford Labs in ’97. This is part of a large set of new physics discovered since the 1930’s from a variety of expanding scientific disciplines that have a direct bearing on the study of cosmology, not all apparently related and not currently organized into one cohesive structure.

    Put these all into a Richard Feynman like analysis of new physics; starting from scratch using only observations and replicated experimental results, combines these new disciplines starting with the conversion of energy into matter conducted at Stanford labs in ’97, then adds dark energy, the Super-Kamiokande ageless atom/proton study, the Hubble’s Deep Field observations, the recording of the 13.7 billion year old CMB cosmic microwave radiation sightings, most importantly – the very slow moving milky-way galaxy and other equivalent discoveries. All these reassembled describes the dark energy source of the Big Bang Explosion in Pre-Existing Space. This then dramatically changes the way we calculate the age of our atoms, galaxies, and Universe.

    The full paper is available on line at my web site:

    Creation of Our Universe:
    a Richard Feynman like analysis of new physics
    discovered since the 1930’s – applied without assumptions
    by Charles Sven ––– March 7, 2013

  9. Pingback: Planck results on the CMB, and latest on the Higgs | Mostly physics

  10. Romulo Binuya says:

    Excellent blog, the hyperlink are very useful in accepting that the CMB map is indeed accurate. Nice to know that among the sub-routines of Planck satellite is setting up of the stage before plotting the CMB map, which includes systematic removal of contaminant emissions. I assume it includes too the factors that could affect the incoming CMB radiation. But still, I would appreciate it if somebody could tell me that the magnetosphere of Jupiter, the second largest continuous structure in our solar system that almost fried the Pioneer probe couldn’t possibly affect the incoming CMB radiation. The hemispherical temperature anomaly is really anomalous. 😀

  11. Romulo Binuya says:

    One more thing about Jupiter is its radiowaves. Have you experienced driving on a dark desert highway and hearing eerie hum, whistle, and roar on the AM radio? They said that’s Jupiter yelling. Is it true that radiowave and microwave don’t interfere with each other, like em waves do in the double slit?

  12. James Gallagher says:

    Hi Romulo,

    Photons interfere with themselves only, as famously pointed out by Dirac in his Lectures on Quantum Mechanics. There are experiments with double beams, starting from early 1960s with MASERS which confuse the issue, but even in these cases the emission intensity can be dropped low enough to ensure only one photon is in the measuring apparatus at a time (and inteference is still observed).

    So, no a radiowave can’t interfere with a microwave. But that’s not needed to cause strange noises in electronic radio equipment, the microwaves just need to interact with the metallic parts in the electronics to cause all kinds of mischief – have you ever tried to listen to an AM radio near a working microwave oven in the kitchen?

  13. Romulo Binuya says:

    Hi James, Thanks! so it was empirically verified that radiowaves don’t interfere with microwaves.. there is something comforting about that.

    I might try that am radio and microwave oven at home though someone told me that the vents in the microwave oven is designed so that the microwave within it of known amplitude and wavelength could not possibly escape.

    I’m still searching about the Jupiter’s magnetosphere and its possible effect on the incoming cmb radiation. It seems that nasa and esa had already investigated our solar system in their previous separate missions, maybe they already considered that magnetosphere. We don’t like another “uh oh moments” loose cable and superluminal neutrino, pioneer anomaly, division by zero, among some goofs… the worst of which is complacency and psychological factors like the Millikan’s unspoken question “Am I wrong?” which caused the inaccurate value of elementary charge e to prevail for some twenty years.

  14. Romulo Binuya says:

    if microwave interferes with am radio, my inference would be quantum tunneling? 🙂

  15. James Gallagher says:

    Romulo, no microwave oven is 100% effective at preventing escaping radiation, but regulations in most countries limit any significant leakage to within a few cm of the oven surface. In fact you can put your mobile/cell phone inside the oven, shut the door and ring it, if it rings then microwaves at the cell phone’s operating frequency are getting through the door grill (though these may be at a different frequency to the oven’s operating frequencies)

    If you have a bad door seal, damaged door grill (etc) leakage will be worse, so the radio test is actually a simple way of checking for leaks (am radio works better than fm radio – perhaps because of the fixed coiled antenna inside an am radio) In particularly bad cases I’ve had wifi connections go down when a microwave oven has been turned on!

    I don’t know if NASA has carefully considered all possible sources of interference in their recent publication of the CMB data, perhaps you could email one of the authors of the recent papers (there are dozens) and ask for clarification of specific issues. It would be amusing if the “axis of evil” anomaly was simply a measurement goof.

  16. James Gallagher says:

    OOPS, sorry, not NASA, ESA the European Space Agency!

    (re your followup question – quantum tunneling isn’t required, microwaves impacting on a metallic surface will generate currents just like in an antenna)

  17. Romulo Binuya says:

    Thanks for the insights James. Kids love watching the cheese melts on a pizza, intuitively I told them to watch it at a distance as something near it might damage the rods and cones in their eyes.

    Wifi signal go down when the microwave oven is on, wifi is radiowave… I guess it’s worthwhile to investigate it.

    I will try to contact esa and nasa asap. Thanks! 🙂

  18. James Gallagher says:

    Just to be accurate about the Dirac quote “Each photon then interferes only with itself” (which is from Principles of Quantum Mechanics p9, not, as I incorrectly wrote, his later published Lectures on QM), In 1967 Pfleegor and Mandel suggested that Dirac might be right even in the two laser sources case, in a paper published just a few years after their original experiments they reduced the intensity of the beams and concluded:

    It is the purpose of this communication to re-
    port the results of further experiments which
    show that the effect cannot reasonably be de-
    scribed as an interference between photons of one
    beam and photons of the other. On the contrary ,
    it appears that Dirac’s statement , in a sense, is
    just as applicable to the foregoing experimental
    situation as to conventional interferometry

    Interference effects at the single photon level – Pfleegor, Mandel 1967 pdf

    This conclusion was found to be too simplistic, and after much more sophisticated investigations the modern consensus is that the Dirac quote is too naive relative to modern field theory. A nice survey by P Hall from 1986: Interference between Independent Photons concludes:

    When the term interference is not taken simply as a
    synonym for the occurrence of an observable interference
    pattern (as it might be by optical researchers), but is more
    generally used to denote any effect indicative of the super-
    position of optical fields, in the sense that their field
    strengths add rather than their intensities, Dirac’s famous
    statement that “interference between two different pho-
    tons never occurs” (Dirac, 1930) proves to be false. This
    has been illustrated in the text by some relevant examples.

    More recently, exotic multiphoton states have been created and applied in Quantum Information scenarios, so Dirac’s single photon interference looks doomed (Scott Aaronson certainly hopes so, he has $100,000 dollars riding on it)

    However, specially prepared coherent laboratory states are one thing, it doesn’t mean you can ever detect interference between naturally occurring microwaves and lower frequency radiowaves

  19. Romulo Binuya says:

    Thanks James, that’s really useful info. I’m still thinking about photons whenever I have the time and simplifying the terms to make it digestive to my layman’s brain. Frequency is photons that hit per second?, intensity is number of photons that hit a unit area? photons comes in beads of discreet ball of waves that depends on its wavelength? the discreet ball of waves is pictured in 2-D but it’s 3-D… 4-Dimensional actually if we include the fourth dimension time. It’s comprehensible that photons interfere with themselves in the double slit, but they do break the rule and split the indivisible quantum in the beam splitter.. allegedly.

    A blog of particular significance is quite active in discussing the cmb map provided by Planck the satellite. I’ll just paste my latest comment there in here… “”Our anomalous cmb map especially its “axis of evil” which is aligned to the ecliptic and the equinoxes, challenge the Copernican Principle. My question to ESA and NASA would be simple if ever I could contact them… “Did you or did you not consider the planet Jupiter before you plot the cmb map?””