Can someone PLEASE explain " the cosmic background radiation during first million yrs"?
Can someone PLEASE explain " The cosmic background radiation dominated the universe during the first million years."
- Anonymous1 decade agoFavorite Answer
In cosmology, the cosmic microwave background radiation (most often abbreviated CMB but occasionally CMBR, CBR or MBR, also referred as relic radiation) is a form of electromagnetic radiation discovered in 1965 that fills the entire universe. It has a thermal 2.725 kelvin black body spectrum which peaks in the microwave range at a frequency of 160.2 GHz, corresponding to a wavelength of 1.9 mm. Most cosmologists consider this radiation to be the best evidence for the big bang model of the universe.
If you tune your TV set between channels, a few percent of the "snow" that you see on your screen is noise caused by the background of microwaves.
We believe that the very early Universe was very hot and dense. At an early enough time it was so hot, ie there was so much energy around, that pairs of particles and anti-particles were continually being created and annihilated again. This annihilation makes pure energy, which means particles of light - photons. As the Universe expanded and the temperature fell the particles and anti-particles (quarks and the like) annihilated each other for the last time, and the energies were low enough that they couldn't be recreated again. For some reason (that still isn't well understood) the early Universe had about one part in a billion more particles than anti-particles. So when all the anti-particles had annihilated all the particles, that left about a billion photons for every particle of matter. And that's the way the Universe is today!
So the photons that we observe in the cosmic microwave background were created in the first minute or so of the history of the Universe. Subsequently they cooled along with the expansion of the Universe, and eventually they can be observed today with a temperature of about 2.73 Kelvin.
- joysam 【ツ】Lv 41 decade ago
In every direction, there is a very low energy and very uniform radiation that we see filling the Universe. This is called the 3 Degree Kelvin Background Radiation, or the Cosmic Background Radiation, or the Microwave Background. These names come about because this radiation is essentially a black body with temperature slightly less than 3 degrees Kelvin (about 2.76 K), which peaks in the microwave portion of the spectrum. This radiation is the strongest evidence for the validity of the hot big bang model. The adjacent figure shows the essentially perfect blackbody spectrum obtained by NASA's Cosmic Background Explorer (COBE) satellite.
The following image was taken by COBE. It shows the temperature of the cosmic background radiation plotted in galactic coordinates, with red cooler and blue and violet hotter (Ref). This dipole anisotropy is because of the Doppler effect. If the Earth moves with respect to the microwave background, it will be blue shifted to a higher effective temperature in the direction of the Earth's motion and red shifted to a lower effective temperature in the direction opposite the Earth's motion.
The indication of the above image is that the local group of galaxies, to which the Earth belongs, is moving at about 600 km/s with respect to the background radiation. It is not know why the Earth is moving with such a high velocity relative to the background radiation.
Evidence for the Big Bang
The cosmic background radiation (sometimes called the CBR), is the afterglow of the big bang, cooled to a faint whisper in the microwave spectrum by the expansion of the Universe for 15 billion years (which causes the radiation originally produced in the big bang to redshift to longer wavelengths). As shown in the adjacent intensity map of the background radiation in different directions taken by the Differential Microwave Radiometer on NASA's COBE satellite, it is not completely uniform, though it is very nearly so (Ref). To obtain this image, the average dipole anisotropy exhibited in the image above has been subtracted out, since it represents a Doppler shift due to the Earth's motion. Thus, what remains should represent true variations in the temperature of the background radiation.
In this image, red denotes hotter fluctuations and blue and black denote cooler fluctuations around the average. These fluctuations are extremely small, representing deviations from the average of only about 1/100,000 of the average temperature of the observed background radiation.
Problems with the Uniformity
The highly isotropic nature of the cosmic background radiation indicates that the early stages of the Universe were almost completely uniform. This raises two problems for the big bang theory.
First, when we look at the microwave background coming from widely separated parts of the sky it can be shown that these regions are too separated to have been able to communicate with each other even with signals travelling at light velocity. Thus, how did they know to have almost exactly the same temperature? This general problem is called the horizon problem.
Second, the present Universe is homogenous and isotropic, but only on very large scales.
- Anonymous1 decade ago
I think it is trying to say that the universe was filled mainly with photons during the first million years, much more so than matter. That radiation was what we now know as the cosmic background radiation, but at that time it was many times stronger than it is now.
- Anonymous4 years ago
Hopefully you are aware that the Big Bang theory was first purposed by a Christian minister. It took science a long time to begin to accept the idea because they felt that it implied there was a Creator behind the Big Bang. Not all creationist reject the idea of a Big Bang. Rather it would seem to match well with the idea in Genesis that the creation of the universe was a one time act of tremendous power (God spoke and it all came into being) that was followed by smaller steps that took it from initial chaos to the orderly world we see today. There are some young earth creationist who want to interpret Genesis to imply a 6000 year old creation. For them, the idea of cosmic background radiation may be an issue, But for the 99% of Christians who believe that the Big Ban and evolution are the mechanics that God used to create the universe and man, it is not an issue.