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In Praise of Ancient Light

How things change over time has never been as strikingly demonstrated as in recent findings. If you go back to the distant era when the universe was only 380,000 years old, you find that neutrinos made up fully ten percent of the universe. Given that these sub-atomic particles moving at nearly the speed of light are so abundant today that millions of them pass through us every second, you’d think they compose a substantial portion of today’s universe, but they actually account for less than one percent. And the change in neutrino ratio is only the beginning.

Changing Content of the Universe

For according to five years of recently released data from the Wilkinson Microwave Anisotropy Probe (WMAP), the early universe was composed of 12 percent atoms, 15 percent photons, almost no dark energy, and 63 percent dark matter. The contrast is stark, given WMAP estimates of the current cosmos: 4.6 percent atoms, 23 percent dark matter, 72 percent dark energy. And, of course, those greatly diminished neutrinos.

Image: WMAP data reveal that its contents include 4.6% atoms, the building blocks of stars and planets. Dark matter comprises 23% of the universe. This matter, different from atoms, does not emit or absorb light. It has only been detected indirectly by its gravity. 72% of the universe, is composed of “dark energy”, which acts as a sort of an anti-gravity. This energy, distinct from dark matter, is responsible for the present-day acceleration of the universal expansion. WMAP data is accurate to two digits, so the total of these numbers is not 100%. This reflects the current limits of WMAP’s ability to define Dark Matter and Dark Energy. Credit: NASA / WMAP Science Team

Usefully, the neutrino information jibes with theories based on the amount of helium we see today, which predict a cosmic neutrino background present when the helium was made. That, in turn, fits with measurements of neutrino properties made in particle accelerators here on Earth. The WMAP data release thus carries us forward, using observation that confirms theories and helps us stake out evidence for an era long vanished. The seven papers just submitted to the Astrophysical Journal about these data further enhance WMAP’s position as a breakthrough instrument.

Other WMAP results of interest: While the process that drives cosmic ‘inflation’ is still problematic (a rather serious understatement on my part), the new data make it possible to eliminate particular versions of inflation while leaving others viable. WMAP principal investigator Charles Bennett (Johns Hopkins) puts it this way: “The new WMAP data rule out many mainstream ideas that seek to describe the growth burst in the early universe.” The new constraints will power future investigations.

CMB Timeline via WMAP Data

Image (click to enlarge): A representation of the evolution of the universe over 13.7 billion years. The far left depicts the earliest moment we can now probe, when a period of “inflation” produced a burst of exponential growth in the universe. (Size is depicted by the vertical extent of the grid in this graphic.) For the next several billion years, the expansion of the universe gradually slowed down as the matter in the universe pulled on itself via gravity. More recently, the expansion has begun to speed up again as the repulsive effects of dark energy have come to dominate the expansion of the universe. The afterglow light seen by WMAP was emitted ~400,000 years after inflation and has traversed the universe largely unimpeded since then. The conditions of earlier times are imprinted on this light; it also forms a backlight for later developments of the universe. Credit: NASA / WMAP Science Team

WMAP also indicates that the ‘cosmic fog’ produced when the first generation of stars began to shine first appeared when the universe was some 400,000 years old. What an era that would have been — the first stars put an end to the darkness, creating a fog of electrons in the surrounding gas that scattered microwaves. The microwaves WMAP looked at to help scientists make these assessments represent light that has lost energy over the subsequent 13.7 billion years of the universe’s expansion, but is still robust enough to tell an extraordinary tale.

For more, see this news release on the WMAP data and its implications. More on the papers in The Astrophysical Journal when they become available.

Comments on this entry are closed.

  • James M. Essig March 11, 2008, 17:41

    Hi Folks;

    The NASA / WMAP Science Team has done great work as did the scientists and engineers who designed the WMAP probe and the technicians who assembled it. It never ceases to amaze me how more and more, our supercomputers seem to make quick work at simulating the birth and evolution of our cosmos at least as far back as the inflationary epoch. We take this for granted, but this is the simulation of the evolution of our universe from its first 10 EXP -33 second after its birth until the present. Our entire universe!!! This shows just how advanced our computers and numerical methods have become and we should all be proud of being human beings and our species and civilization for being able to come up with such computer systems and numerical methods for simulations as such.

    I wonder what will be next, simulation of the evolution from the first Planck time instant of 10 EXP – 43 after its birth? a limited subset of the first Planck time interval? the modeling of any future inflationary epochs or future phase changes or further symmetry breakings? the modeling of the fractal-verse or multiverse for GOD’s sake? perhaps the modeling of other fractal verses or multiverses?!! Perhaps one day in the extemely remote cosmic future, even the spiritual cosmos assuming such exists?!!

    The reader of this posting can clearly see that we will always find applications for ever faster, ever more sophisticated, and ever more complex supercomputers. I will note that at the college at which I recieved bachelors degree in Physics, George Mason University, in Fairfax VA, right outside of Washington D.C., they know have an innovative graduate or doctoral program in computational sociology of all things. Will we one day be able to usefully model the dynamics of advanced interstellar or intergalactic space-faring ETI civilizations as a whole or their minds and brains on an individual basis?

    We went from crude slide rules in the early 1940s to single supercomputers so fast that they are now approaching Petaflops capability. That’s 1,000 Teraflops or 10 EXP 15 floating operations per second in 70 short years. It was only as far back as the late 1970s when the CRAY supercomputers could only do one GigaFlops and now we are approaching speeds a million times greater than that with more complex individual calculations to boot.

    Many thanks to all of you computational astrophysicists, computational cosmologists and to all of you pen and paper theoretical physicists and theoretical cosmologists for comming up with the equations for which the computations are run and approximated numerically.



  • david March 12, 2008, 7:34

    That is really interesting.

    So, dark matter is decreasing. Is it being converted into dark energy by some process? What happens when/if it hits 0. If it is being converted into dark energy then when dark matter hits the 0 mark, and if there is no other source for the creation of dark energy, that would imply that as the universe gets larger the density of dark energy would decrease. Which would mean the the rate of expansion would decrease?

    But then the amount of atoms and other non-dark matter is also decreasing. So might there be a process by which matter is being turned into dark matter or dark energy? If so then the increase in dark energy might not stop until it is 100 percent of all the matter and energy in the universe? That would be very bad for life unless there is some way dark energy can support life. Or unless we can create atoms out of dark energy. There might be some relationship between matter and dark energy just as there is the famous e=mc(squared) equation for a relationship between energy and matter.

    Other than such thoughts such things are way beyond me. The people who can conceive of mathematical formulas describing such things and come up with ways of testing it are as far beyond me as I am compared to a chimp. If not more so given a chimp can use language and tools (like me) when taught to do so.

    t was only as far back as the late 1970s when the CRAY supercomputers could only do one GigaFlops and now we are approaching speeds a million times greater than that with more complex individual calculations to boot.

    That is the sort of thing that both scares me and fascinates me when I think of AIs and what they might do. If we were to create an AI with normal human intelligence and rate of thinking then in a very short time (a decade maybe) it would be able to think over a million times faster than us biological beings. A short times after that it could be trillions of times faster. The only limit would be the maximum speed the laws of physic allow computations to be done. Humans would be obsolete. Interstellar travel might be impossible for such entities – the several years it would take to get to their destination might seem like a near infinity to them. Even if they travel at the speed of light, with what seems like a 0 time elapse for them, it would still cut them off from the rest of their civilization. And once they did arrive exploring the system would still take them a near infinity.

  • wokka March 12, 2008, 14:32

    You do know that the preprints of the WMAP papers are available from arXiv.org?

  • Administrator March 12, 2008, 14:52

    No, I didn’t realize these papers were up at arXiv yet — great to hear they’re available. If you would, wokka, please pass along a link or two.

  • ljk March 24, 2008, 9:50

    Cosmological Signatures of the Interaction between Dark-Energy and Massive Neutrinos

    Authors: Kiyotomo Ichiki, Yong-Yeon Keum

    (Submitted on 21 Mar 2008)

    Abstract: We investigate whether interaction between massive neutrinos and quintessence scalar field is the origin of the late time accelerated expansion of the universe. We present cosmological perturbation theory in neutrinos probe interacting dark-energy models, and calculate cosmic microwave background anisotropies and matter power spectrum. In these models, the evolution of the mass of neutrinos is determined by the quintessence scalar field, which is responsible for the cosmic acceleration today.

    We consider several types of scalar field potentials and put constraints on the coupling parameter between neutrinos and dark energy. Assuming the flatness of the universe, the constraint we can derive from the current observation is $\sum m_{\nu} < 0.87 eV$ at the 95 % confidence level for the sum over three species of neutrinos. We also discuss on the stability issue of the our model and on the impact of the scattering term in Boltzmann equation from the mass-varying neutrinos.

    Comments: 4 pages, 3 figures, revtex

    Subjects: Astrophysics (astro-ph); General Relativity and Quantum Cosmology (gr-qc); High Energy Physics – Phenomenology (hep-ph)
    Cite as: arXiv:0803.3142v1 [astro-ph]

    Submission history

    From: Yong-Yeon Keum [view email]

    [v1] Fri, 21 Mar 2008 10:47:07 GMT (59kb)


  • ljk March 28, 2008, 13:30

    13.73 Billion Years – The Most Accurate Measurement of the Age of the Universe Yet

    Written by Ian O’Neill

    NASA’s Wilkinson Microwave Anisotropy Probe (WMAP) has taken the best measurement of the age of the Universe to date. According to highly precise observations of microwave radiation observed all over the cosmos, WMAP scientists now have the best estimate yet on the age of the Universe: 13.73 billion years, plus or minus 120 million years (that’s an error margin of only 0.87%… not bad really…).

    Full article here: