Matter-Antimatter Asymmetry : Our universe is observed to consist of matter. Today there is no evidence of antimatter in the form of stars, galaxies, galaxy clusters or any form of cosmological antimatter. However, antimatter should have been plentiful when the temperature of the universe was high enough to create matter- antimatter pairs. In order to prevent complete annihilation of matter and antimatter, the early universe must have had a very slight asymmetry between the matter density ad the antimatter density. Theories for the origin of the matter- antimatter asymmetry all involve charge- conservation- parity (CP) violation and violation of the law of convservation of baryon number. While CP violation has been observed in reactions involving kaons and B-mesons, unfortunately there is no experimental evidence for violation of baryon number (such as proton decay).
* In homogeneous, isotropic cosmological models, the spatial geometry of the universe may be flat, spherical, or hyperbolic. The standard hot big bang model is consistent with the observed high degree of spatial flatness of the universe, but cannot explain it. * Observations of the cosmic microwave background from the big bang reveal a universe that is very smooth, but not perfectly smooth. The temperature of teh universe is very nearly the same in all directions, but there are tiny fluctuations in the temperature of the background in different directions of the sky. These small temperature fluctuations cannot be explained by the standard cosmology. * The early-universe theory of inflation potentially provides an explanation for the observed homogeneity and isotropy of the universe, the spatial flatness, the seeds of structure, and the temperature anisotropies. However, inflation involves particle physics at energies beyond the experimental reach of terrestrial accelerators, and hence it is untested. * Various recent observations suggest that the present expansion velocity of the universe is larger than it was in the recent cosmological past; the expansion of the universe is accelerating. This increase with time of the expansion velocity of the universe is believed to result from the mass-energy of the universe dominated by a type of "lambda" term pr a cosmological constant) in teh gravitational field equations as proposed by Einstein by 1917. More generally, the lambda term is referred to as "dark energy". At the current time, the physical explanation for the dark energy is unknow. * Dark energy and dark matter seem to comprise 96% of the mass- energy density of the present universe (73% dark energy and 23% dark matter). Only about 4% of the mass-energy of the universe is made of ordinatry neutrons and protons, i.e familiar matter that we are made up of. we do not yet understand the basic forms of matter and energy in the universe.
1 Comment
raevol
2/13/2016 04:54:18 pm
We have to be a part of mystery to solve the mystery
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