44. THE MICROWAVE SKY

The Microwave Sky
WMAP has produced a new, more detailed picture of the infant universe. Colors indicate "warmer" (red) and "cooler" (blue) spots. This new information helps to pinpoint when the first stars formed and provides new clues about events that transpired in the first trillionth of a second of the universe.


The CMB Angular Spectrum



The "angular spectrum" of the fluctuations in the WMAP full-sky map. This shows the relative brightness of the "spots" in the map vs. the size of the spots. The shape of this curve contain a wealth of information about the history the universe.

There is a "black" period between the inflation process and the start of CMB - radiation (see article 46). We call that period "DARK AGES", the period where stars and systems were born. Fortunately there is a very poor radiation: "spin-radiation" , in the radio-frequency region with some cm's wavelength, which is stretched by the expansion up to some hundreds of meters. That radiation can yet be used to investigate that period, albeit that we need antenna's of kilometers length!.
The expansion goes on and on, even in an accelerated way since the last ~ 7 billion years!
For stopping the expansion of the universe dark matter is not the answer, (if dark matter should consist of normally matter formed from elements it can only exist in very short supply, otherwise the limit of the critical mass will be severely exceeded). If we take all observed resp. calculated stardust and dark matter (as defined in article 37) together, then it is still only a fraction of the critical mass necessary, less than 30%.
Therefore there must be another source of density compensating for the great deficiency in required density. That is the reason for the introduction of the notion “DARK ENERGY”, an energy being “invisible” but contributing to the density of the universe in order to reach the critical density (energy = mass!) . That energy is not just fantasy, it comes out that when it is added as extra mass to the universe to explain the now observed ever increasing expansion it fills up exactly the 70% deficiency in density.

The universe has been created from a very hot and dense “prehistoric soup”, a plasma of electrons and positrons, of various sorts neutrino’s with their antiparticles and of protons and neutrons. Photons were strongly bound, escaping was not possible, but fluctuations in density occur, that is “quantum noise”. When the temperature decreased by super-fast expansion of the universe, those fluctuations were isolated and blown up into inhomogeneous areas of various densities, where gravitational forces had the final word at last.
The masses in the inhomogenities were enormous, equal to stars or even galaxies. So 300.000 - 400.000 year after the inflationperiod, when the temperature has dropped to about 3000 K, the original fluctuations became all “frozen" in as anisotropies, that is: photons therein had no longer any pressure effect, they are no more bound, moving more or less free through space after their last scattering.
Those free photons give a radiation phenomenon: the CMB : COSMIC MICROWAVE BACKGROUND - radiation, which presents the temperature differences between small areas on the firmament against a continuous background. The temperature differences are “frozen” acoustic oscillations, mathematically expressed in a “powerspectrum”, (see figure).
The first large-scale measurements of CMB by the Cobe-satellite show a very homogeneous universe, with many small spots of just a bit higher or lower temperature (1 on 100.000!) from which finally the larger structures in the present day cosmos were formed, such as galaxies.
The intensity of light emitted as CMB-radiation shows an frequency distribution analogous to the spectrum of light, that is emitted by a black box with T = 2.7 Kelvin. That spectrum has a wavelength distribution with a peak at ~ 2 mm.
Be aware of the fact that the CMB - radiation has shifted from the highfrequency area (gamma-rays) to the microwave area today by the expansion of the universe during 13 billion years.

CMB - radiation is everywhere present in the universe, so also around ourself: about 1% of the noise on T.V. - screens is determined by that.
Those areas with different temperatures form also the basis of the matter in the present day universe: stars and galaxies, because it is supposed that the resulting density-anisotropies grew by gravitation forces to the objects now observed by us.
This proces of gravitational attraction, causing the accretion of matter around the original small fluctuations, forming still larger structures, is called: the “gravitational instability model” for the formation of the structure of the universe.