Cosmic background radiation

On the last three decades, several space experiments with parts at very low temperatures have been flown. Among these, we mention IRAS (Infrared Astronomical Satellite) launched in 1983 (see Fig. 14.1), COBE (Cosmic Background Explorer) launched in 1989, ISO (Infrared Space Observatory) launched in 1995 and Astro-E (X-ray Observatory), launched in 2000 with instrumentation at 65 mK [35], Some cryogenic space missions are in the preparation or in final phase in Europe, USA and Japan. For example, ESA is going to fly Planck (for the mapping of the cosmic background radiation) and Herschel (called before FIRST Far Infrared and Submillimetre Telescope ) [36], These missions will carry experiments at 0.1 and 0.3 K respectively. 

Figure 2.3 An almost-perfect black body spectrum for the cosmic background radiation. Figure courtesy of NASA/COBE Science Team...

Universe, tell me how old you are, and 1 will tell you the colour of your radiation background and the energy of each of your photons. Today, the cosmic background radiation is red, very red. It is so red and cold (about 3 K) that it cannot be seen. Its chilled voice quivers in the great ears of our radiotelescopes. Solar emissions, on the other hand, can be compared with the radiation from an incandescent body at a temperature of around 5700 K. Temperatures vary across the Universe, from 2.73 K for the cosmic background to 100 billion K when a neutron star has just emerged. 

The neutrino Sun never sets. Sixty billion neutrinos blasted out from the Sun s core eight minutes ago fly through every square centimetre of our body each second. We feel absolutely nothing and neither do they. They are the height of discretion. The night is not absolutely dark because, not only are we forever bathed in the cosmic background radiation at microwave wavelengths, but we... 

It is therefore a Euclidean universe which lies at the meeting point between data from remote supernova studies and observations of the cosmic background radiation. Such a universe contains just enough matter and energy to keep the geometry Euclidean. In fact the Euclidean cosmology fits our Universe like a glove. 

For most astronomers, the solution to these cosmological problems resides in a combination of various methods. The luminosity-redshift test must be combined with independent techniques, such as anisotropies in the cosmic background radiation and statistical study of gravitational lenses. 

In the spirit of Lorentz [45], de Broglie, and Vigier, let us postulate the existence of a preferred frame E. Operationally, E may be identified with the frame of cosmic background radiation (CBR), whose isotropic thermal nature was established by measurements during the COBE-FIRAS project [46]. Then, the principle of relativity simply states that all frames that are not accelerated relative to E, are equivalent to it. 

For the connection between the CN-predic-tion and the cosmic background radiation, see Kragh, Cosmology and Controversy, 134-135, 345-347. 

An important application of cosmic background radiation is to provide a test of the reality of the expansion if we are able to measure the temperature of the background at higher redshift it should scale accordingly to ... 

We cannot help but notice that temperature fluctuations in the cosmic background radiation have a typical fractional magnitude of J7 as 10 5 [70,71]. The observed and measured value T k, 10 5 [70,71] is obviously far more certain than the speculated value / 10 5 hence the distinction between the fs symbol as opposed to the symbol. Although it is unlikely that there is a connection between T k, 10 5 [70,71] and / 10 5, it doesn t seem to hurt if we at least mention this numerical concurrence — just in case there might be a connection. 

The anisotropy of the microwave cosmic background radiation is being measured by the Wilkinson Microwave... 

This temperature is that of the cosmic background radiation. The species have reasonably large electric dipole moments for CH and CN, measurement gives... 

A transparent Universe. After 300,000 yr temperatures dropped to 4,500 K and gave rise to the formation of atomic matter, and atoms of hydrogen, helium, and deuterium were formed. Because electrons were removed from the plasma through the formation of atoms, radiation streamed out and the Universe became transparent. Initially the Universe contained abundant ultraviolet-and X-rays, now cooled down to microwave wavelengths. This is what is recorded as the Cosmic Background radiation. 

The present Universe. As the universe continues to expand the initial radiation will appear to be derived from a much cooler body. Hence today the Cosmic Background radiation is 2.73 degrees above absolute zero. 

As cosmologists began to accumulate measurements of the Cosmic Background radiation at the edge of the Universe they were impressed by the uniformity of the results. 

Question. Does ihe short-wavelength approximation apply over all of these ranges Would it apply to the cosmic background radiation of the universe at 2.7 K where Amax 0.2 cm ... 

P13.30 The question of whether to use CN or CH within the interstellar cloud of constellation Ophiuchus for the determination of the temperature of the cosmic background radiation depends upon which one has a rotational spectrum that best spans blackbody radiation of 2.726 K. Given flo(CH) = 14.90 cm-1, the rotational constant that is needed for the comparative analysis may be calculated from the 226.9 GHz spectral line of the Orion Nebula. Assuming that the line is for the l2Cl4N isotopic species and J + 1 <— 7=1, which gives a reasonable estimate of the CN bond length (117.4 pm), the CN rotational constant is calculated as follows. 

The cosmic background radiation and molecular absorption lines are shown in the graph. Figure 13.7. It is evident that only CN spans the background radiation. 

Big Bang theory supported by discovery of cosmic background radiation, inflation theory, high-energy particle collision expts. ... 

It was still too hot for the electrons to join the hydrogen and helium ions to form neutral atoms. This occurred not until about 500 000 years later, wh tenq>erature had dropped to a few 1000 K. The disappearance of free electrons broke the thermal contact between radiation and matter, and radiation continued then to expand freely. An outside spectator would have observed this as a hugh flash and a rapidly expanding fireball. In the adiabatic expansion the radiation cooled further to the cosmic background radiation level of 2.7 K measured today. 

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