Tuesday, June 12, 2012
The Cosmic microwave background radiation
Some facts of interest on the frequencies of CmB (cosmic microwave background).
The Cosmic Microwave Background (CMB) is the isotropic, electromagnetic radiation which resulted from the explosion of the universe between 15 and 18 billion years ago. This theory, accepted by many but not all, is called The Big Bang theory. The Big Bang was the explosion of the universe from the extremely small, dense, and hot conditions of the early universe. The photons and baryons present in this environment formed plasma, a gas of ionized matter united with the radiation also found in the atmosphere. After the universe exploded, the temperature decreased and the universe began to expand very rapidly. Particles such as electrons, neutrinos, protons, and neutrons, which were non-existent in the era before the explosion due to the extremely high temperatures began to form in the cooler temperatures. For the next 300,000 years, the particles scattered around the universe. The universe was opaque because the photons constantly bumped into the additional particles, such as the electrons, protons, and neutrinos, thus not allowing the photons to travel far distances. Anytime the protons and electrons attempted to combine, the photons had enough energy to rip them apart. Eventually, the temperature decreased so greatly that it was possible for the electrons and protons to combine without intervention from the photons, and neutral hydrogen atoms were formed. This period in time is referred to as "recombination.""Recombination"turned the formerly opaque universe transparent. In turn, matter and radiation were disunited. The photons were able to travel throughout the universe, free from interaction with matter. The vast array of photons that roam the universe is now what we refer to as Cosmic Microwave Background.
Cosmic Microwave Background is the greatest evidence in support of the Big Bang theory. Due to the constant expansion of the universe, the radiation had cooled to 2.73 K. The cmB is isotropic, meaning that it is uniform throughout the universe in all directions. The cmB spectrum is a perfect blackbody, or an object capable of absorbing all the electromagnetic radiation that it comes in contact with. By observing the cmB, scientists can learn a great deal about the universe after the big bang. The cmB does not have one specific frequency, but many frequencies throughout the microwave range. The peak frequency is 160.4 GHz. The frequencies range from 0.3 GHz to 630 GHz.