The long-awaited preliminary results from MAP were announced at a press conference on February 11, 2003. By then MAP was renamed WMAP, honoring the late David Wilkenson, a leader in the field from Princeton. Cosmologists at this conference stated that the WMAP results were among the most important in the last half century in deciphering the history of the early Universe. The higher resolution of WMAP, in terms of ability to measure even smaller temperature variations, is evident by comparing the new all-skies thermal map from WMAP with the equivalent coverage by COBE:
This pair of plots clearly demonstrates the great leap in resolution provided by WMAP, leading to much more detail about the very slight but signficant variations in CBR temperatures. A better view of the distribution of the very small but important blackbody background temperatures is afforded in this projection of WMAP measurements that describe conditions less than a half million years after the Big Bang; three additional spherical maps are needed to cover the entire sky:
Slight differences from the first WMAP shown above appear in the version below (Spring, 2009) which represents five years of data gathering.
The variations in color in this, and other maps above, give the impression of notable differences in value. Actually, the temperatures vary by very small amounts. The temperature differences give rise to slight variations in density. But these variations were key to the gradual buildup in differential densities that eventually brought about differences in gravitational attraction leading to local clumping into the first stars and larger scale clumping into the first galaxies. The variations represented by the spread of colors as seen in the WMAP map are an indication of the spatial distribution of the clumps in the early Universe; even though the CBR is now much cooler than in these early times this distribution pattern has persisted.
Some very far-reaching conclusions about the Universe have been drawn from interpretations of the WMAP data. One is a new (but still not necessarily the most accurate, although an accuracy of +/- 200 million years is claimed) age for the Universe of 13.7 billion years. The value has superceded the earlier 14.7 billion years that came out of COBE and other studies. This is based mainly on what is believed to be a better estimate of the Hubble Constant: 65 km/s/Mpc. Another WMAP conclusion is strong confirmation of the reality of Inflation during the first fraction of a second after the Big Bang.
WMAP leads also to a better estimate of the amount of detectable Ordinary Matter in the Universe and values for the invisible matter/energy that so far has eluded direct recognition and measurement. These have been reset at 4% for Ordinary Matter, whereas Dark Matter is 23% and Dark Energy 73% (but the results offer no clear indication of the nature of these dark states). (Only a fraction of Ordinary Matter is luminous [gives off detectable visible light], so that the vast bulk of the Universe's constituents is in fact non-luminous and thus hard to detect.) The time when the Universe first became transparent is now given as ~380000 years after the BB. Indirect evidence from WMAP data suggest that massive stars had begun to organize even earlier, perhaps over an interval of about 200,000-300,000 years post-Big Bang. .
COBE and WMAP data have been used to refine many of the fundamental physics and cosmological parameters as shown in this table:
However, the list below focuses on what cosmologists consider the 10 most important parameters whose values have been better calculated using the CMR data:
The English cosmologist, Dr. Martin Rees has cited his own list of the irreducible number of fundamental parameters that determine the development of the Universe we can measure in his book Just Six Numbers: The Deep Forces that Shape the Universe, 2000, Basic Books. These are: 1) N; = ratio of the electric force holding atoms together to the (much weaker) force of gravity, 1036; if this number were larger then only a miniature and short-lived Universe would have formed; 2) ε = a measure of the strong nuclear force, determined from the energy released in the fusion of Hydrogen to helium (differential of 0.007); if much different than this value, a different mix of chemical elements results, with carbon very scarce; 3) Ω = amount of matter/energy in the Universe (see below); it is the ratio of actual density to the critical density (see below); if too high, the Universe collapses and if too low, expansion would be so fast that there would be insufficient time for stars and galaxies to form; 4) λ = antigravity force (Cosmological Constant); if too large, the Universe would have expanded so rapidly as not to develop as it has; 5) Q = force needed to dissemble a gravitationally stabilized cosmic structure (star; galaxy), measured as the ratio of the energy needed to overcome the gravity force to the energy bound in the rest mass of the cosmic body, given as 10-5; if Q deviates from this value, a smaller number would have prevented the ripples that gave rise to galaxies, leaving only a dispersed gas but if much larger, only black holes would exist today; 6) D = number of spatial dimensions (3) needed to sustain life in our planet and similar bodies; 2 or 4 would have doomed our existence.
In addition to cosmological parameters, there are also many basic physical constants that are involved in both Cosmology and Physics as practiced on Earth. A discussion of these is given at this web site. More discussion of many of the parameters, as they bear not only on the origin and development of the Universe but on the appearance of organic life and ultimately Man, is given in the philosophical discussion subsection near the bottom of page 20-10.
The data displayed in the WMAP, CBI and other CMR maps also bear on the model that predicts the Universe had undergone a dramatic Inflation in its initial moments, and in effect provide a positive test of that concept. They likewise point to the notion of a flat Universe that will expand forever (see below).
A recent announcement from Hubble scientists carries this cosmic background concept into the visible radiation realm. Based on estimates of quasar populations at the farthest reaches of observable space (the Deep Field region), extrapolations of visible light sources to the entire Universe can be made. Results suggest that most of these sources are now accounted for and that the total amount of visible light which persists throughout the Universe is approximately of the order to be expected (by calculation) from the same model that predicts the amount of Cosmic Background Radiation. In other words, as different parts of the EM spectrum are analyzed for total energy involved, the numbers remain consistent with expectations and thus support the energy distribution predicted from the Big Bang model. The overall notion of an expansion appears on firm ground based on the ever accumulating scientific evidence.
(A CAUTION: A report issued in November, 2003 presents some support for a very KEY topic of controversy in Astrophysics and Cosmology: Have some or even all of the fundamental constants been constant throughout the Universe's history? The speed of light is a leading candidate for dispute and ingenious arguments indicating possible variation. In the report, evidence is cited that the strength of the attraction between nuclear protons and orbiting electrons may have been much greater in the early days of the Universe. The role of quintessence (top of next page) is cited as the factor responsible for this. Other constants are being challenged but until incontrovertible proof is accepted, the "rule of thumb" is to stay with the values (subject to possible minor modifications) cited above.)
Some of the recent ideas on the start times for the first stars and galaxies received support and specificity from the WMAP results. The first stars began to form as Supergiants about 200,000,000 million years after the Big Bang. The first galaxies began to organize some three hundred million (300,000,000) years later (possibly earlier). This next diagram depicts these stages (from left to right): 1) initial stages of CBR variations; 2) clots of matter prior to organization as stars; 3) the first supergiants; 4) developing galaxies; 5) galaxies after the first billion years.
The time lines for the first stars and galaxies as measured by different space telescopes (JWST is the James Webb Space Telescope planned for 2010; its mission will focus on the early eons of the galaxies, so that the starting time shown above is a "best estimate" for now) are shown in this diagram. Of special import is the new estimate of when the first stars started to form - about 200 million years after the Big Bang.
A major future objective of WMAP still to be addressed is to measure extremely small temperature fluctuations that should support/confirm the existence of gravitational waves. These were first postulated by Einstein as a consequence of his General Theory of Relativity. Gravitational waves represent moving disturbances within gravitational fields that are generated by various interactions of matter and/or energy, such as collisions of Black Holes or Neutron stars. With their force particles, the gravitons, they are analogous to electromagnetic waves, with their photons, except that gravitational waves can move unimpeded through matter that itself interacts with photons by absorption. Like the graviton, gravitational waves have yet to be detected but their behavior and influence within the Universe can be simulated with computer-based models. As gravitational waves move through space, they cause the geometry of space to oscillate (stretching and squeezing it). The wavelength of a gravitational wave depends on the mechanism of its generation.
Theory holds that gravitons and gravitational waves must have first been created during the Inflation period between 10-38 and 10-35 seconds at the outset of the Big Bang. These waves participated in the extreme expansion during those moments and as a result their wavelengths were greatly elongated. The inflationary gravitational waves played a key role in bringing about the slight variations in the distribution of matter and energy during the Radiation Era which ended in the Decoupling Era at which time photons were no longer scattered - this latter period is the earliest in which Cosmic Background Radiation could then be detected. WMAP is seeking to determine more exactly the temperature fluctuations in the CBR field which correspond to the pertubations imposed by the gravitational waves. In theory, these waves are detectable by analysis of the CBR coming from the Cosmic Microwave Background; gravitational waves will cause the radiation to be right or left polarized whereas density variations in the CMB will induce radial polarization (the two modes of polarization must be separated and distinguished by Fourier analysis.
The CBR phenomena are proving to be especially fruitful in the study of the Cosmos. It is not surprising then to learn that more satellites are to be put into space to observe the CBR. Next up is Planck, which was launched with its sister satellite Herschel on May 14 of 2009. It will eventually reach its final location at L2, the second Lagrangian point between Earth and the Sun. That location is approximately 1,500,000 km (930,000 miles) from Earth. Planck will have instruments that can measure very small temperature differences using data from 9 different bands. Here is an artist's rendition of Planck. Check out its homepage at this ESA website.
In August, 2009 Planck began returning data from which images are made. This example shows the Milky Way (central band) and adjacent areas of the sky (covering a 20° by 20° area) at 9 different microwave wavelengths (LFI refers to Low Frequency Instrument and HFI is the High Frequency Instrument):
The first full sky Planck microwave map shows a strip that actually covers 360° but is curved as shown on this projection. The map has been superimposed on a visible light image that highlights the Milky Way (which shows up as the dark red brown patches in the map). The regions off the Milky Way represent temperature differences (as with WMAP, red is warmer than blue) associated with the time of First Light about 300,000 years after the Big Bang. This rendition is not impressive as such, but the image below it shows some details in a 10° by 10° segment of the sky at high latitude off the Milky Way).