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Cosmos Study Dashes Hope for New Neutrino

The views expressed are those of the author and are not necessarily those of Scientific American.


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Planck CMB intensity map

Planck's map of the cosmic microwave background, courtesy of ESA and the Planck Collaboration

First particle physicists discovered “a boring old Standard Model Higgs boson,” as my colleague Michael Moyer put it, meaning that the particle hewed closely to theoretical predictions and offered little in the way of guidance to new and exciting physics. This week the European Space Agency’s Planck satellite gave a significant boost to cosmology’s own standard model, the so-called lambda-CDM cosmology in which dark energy and dark matter rule the universe. But the situation here is hardly boring, given that the very nature of dark matter and dark energy remain a mystery.

The first batch of Planck cosmology studies arrived March 21, and it is formidable. Spread across 29 lengthy scientific papers, Planck’s precise measurements of the cosmic microwave background (CMB)—remnant light from the very early universe, just 370,000 years after the big bang—confirm that the universe is about 13.8 billion years old and is dominated by dark energy, with dark matter playing a significant supporting role and normal matter (the atoms of the everyday world) constituting just a few percent of the overall contents.

In short, the Planck data seem to contain no major surprises, although they confirm a few outstanding anomalies from Planck’s CMB-measuring predecessor, NASA’s Wilkinson Microwave Anisotropy Probe (WMAP). In an intriguing anomaly, the CMB appears somewhat asymmetrical, as if the universe were a little lopsided.

Neutrino physicists, however, may find themselves a bit disappointed with Planck’s results, which disfavor the possible existence of an extra, yet-to-be-discovered variety of neutrino. Particle experiments on Earth have shown that neutrinos come in at least three flavors—electron neutrinos, muon neutrinos and tau neutrinos—and that neutrinos oscillate between those flavors as they propagate through space. But some puzzling experimental results have hinted that a fourth neutrino flavor—the sterile neutrino—might exist as well. (This hypothetical neutrino is called “sterile” because, unlike the other neutrinos, it would not feel the weak nuclear force and would barely interact with other particles.) Now that possibility looks rather unlikely.

CMB experiments and neutrino physics would seem an odd partnership, but the number of neutrinos and the masses of the particles can indeed have large-scale effects that shape the appearance of the CMB. The total number of neutrino species, for instance, affects the rate at which the cosmos expanded in its earliest epochs: more neutrinos means a faster expansion. Recent WMAP data were consistent with the three-neutrino family portrait but easily accommodated—even hinted at—the possibility of a fourth particle. The new Planck results (pdf), however, favor the existence of just three neutrinos.

One potential bright spot for neutrino physicists: the Planck observations have better pinned down the combined masses of the three neutrinos, none of which can yet be individually weighed with any precision. Cosmology studies currently provide the best limits on the neutrino’s mass, and Planck is already tightening those constraints to clarify the picture of the elusive neutrino. The sum of all three neutrino masses as per the Planck collaboration is no more than 0.23 electron-volt (for comparison, a single electron is two million times more massive), roughly half of the upper limit set by WMAP.

 

About the Author: John Matson is an associate editor at Scientific American focusing on space, physics and mathematics. Follow on Twitter @jmtsn.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. Mike.A.Schwab 9:35 pm 03/22/2013

    Perhaps the lopsided results means we are seeing to the beginning of the universe and we are slightly to one side of the center?

    Link to this
  2. 2. jtdwyer 12:18 am 03/23/2013

    I think the confirmation of the previously ignored contradictions with the Lambda-CDM model have been downplayed in all reports I’ve seen other than those from ESA. The Plank observational data indicates a very large scale anomalous symmetry in the distribution of ancient microwave emissions, capped by a seemingly related very large scale cold spot. Please see
    http://spaceinimages.esa.int/Images/2013/03/Planck_enhanced_anomalies

    “One of the most surprising findings is that the fluctuations in the CMB temperatures at large angular scales do not match those predicted by the standard model – their signals are not as strong as expected from the smaller scale structure revealed by Planck.

    “Another is an asymmetry in the average temperatures on opposite hemispheres of the sky. This runs counter to the prediction made by the standard model that the Universe should be broadly similar in any direction we look.

    Furthermore, a cold spot extends over a patch of sky that is much larger than expected.

    “The asymmetry and the cold spot had already been hinted at with Planck’s predecessor, NASA’s WMAP mission, but were largely ignored because of lingering doubts about their cosmic origin.

    “”The fact that Planck has made such a significant detection of these anomalies erases any doubts about their reality; it can no longer be said that they are artefacts of the measurements. They are real and we have to look for a credible explanation,” says Paolo Natoli of the University of Ferrara, Italy.”

    Please see the announcement http://www.esa.int/Our_Activities/Space_Science/Planck/Planck_reveals_an_almost_perfect_Universe and the more detailed report http://sci.esa.int/science-e/www/object/index.cfm?fobjectid=51551

    That the current standard Lambda-Cold Dark Matter model of cosmology produces results that can be well fit to current, exceedingly complex interpretations of observations does not preclude fundamental misconceptions – as demonstrated for more than a millennium by the Ptolemaic model of the cosmos.

    Link to this
  3. 3. rloldershaw 5:47 pm 03/23/2013

    One possible explanation for the newly verified dipole anisotropy in the CMB is that the structure of the cosmos has a fractal geometry and nature’s hierarchy extends far beyond the observable universe.

    Unlike the radical idea of a multiverse of 10^500 different universes with random properties, the discrete fractal paradigm proposes one unified physics for the entire cosmos. It is a new paradigm that is based on enlarging the symmetry properties of nature, rather than invoking ad hoc and thoroughly untestable speculations.

    Our observable “universe” may occupy a relatively infinitessimal volume within an object whose size is almost umimaginably large and yet is one but object among countless others on the next higher scale in nature’s hierarchy. If the hierarchy is rigorously self-similar, as appears to be the case within our obserable universe, then the physical laws would have the same covariant form on all scales.

    Robert L. Oldershaw
    http://www3.amherst.edu/~rloldershaw
    Discrete Scale Relativity/Fractal Cosmology

    Link to this
  4. 4. rloldershaw 9:23 pm 03/23/2013

    MAXWELL’S EXCELLENT ADVENTURE

    Imagine a “Maxwell Demon” of infinitesimal size deep in the interior of a type-II supernova event.

    Surveying his observable environment of about 10^-18 cubic centimeters, he draws the following conclusions.

    1. There is global expansion, as he can see from the velocities of the 10^11 gigantic particles.

    2. Superimposed upon this global expansion there are random velocities of about 700 km/sec that he calls “peculiar velocities” and indicate some unexplained very high-energy and chaotic phenomena.

    3. The unusual “weblike” filamentary/void distribution of the particles reminds him of high energy plasma phenomena

    4. The overall distribution of the gigantic particles looks very homogeneous, at least statistically speaking, but there is a small dipole anisotropy, i.e., slightly more particles and slightly higher temperatures in one direction and slightly lower values in the opposite direction.

    Maxwell concludes that the Universe, including all space, time and matter, began about 3 x 10^-17 seconds ago, apparently out of the vacuum. In order to explain the homogeneity, isotropy, lack of curvature, etc., he decides that a brief period of extreme inflation shortly after the creation event will explain things quite nicely. He is very pleased with his model and is sure that the small anomalies will be explained by the model in the near future.

    We then move “Maxwell” by about 10^15 centimeters to a location far outside of the supernova event. Looking back with mouth and eyes wide open, he utters two 4-letter words. The first is “Holy” and the second begins with “S”. He makes a solemn oath to never again confuse model-building models with the actual physical cosmos.

    Robert L. Oldershaw
    http://www3.amherst.edu/~rloldershaw
    Discrete Scale Relativity/Fractal Cosmology

    Link to this
  5. 5. Percival 12:48 pm 03/27/2013

    I wonder if it will eventually prove not to be possible to directly measure the mass of the three known neutrino types for the same reason that we can not directly measure the color(/anticolor) of any given quark; because they always come in threes. If indeed all neutrinos are subject to oscillation (are superpositions of all three kinds) the best we could hope for is a FWHM (FDHM?)for a given neutrino energy.

    Link to this
  6. 6. Xanthe Hunt 2:16 am 08/6/2013

    Would it be possible for me to interview you, Mr Matson, regarding science writing? I am a journalism student from Stellenbosch University in South Africa, and I am researching specialist science journalism. I would love to quiz the best on how it is done.

    If you have any spare email-minutes, please contact me on 16001974@sun.ac.za.

    Regards,
    Xanthe Hunt

    Link to this

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