Checking the Big Bang
2) Abundance of light elements: predicted abundance of helium4, helium3, deuterium and lithium7 (the number refers to the combined number of protons and neutrons) in the Big Bang model agrees with measured abundance of these elements in the universe.
3) Cosmic microwave background radiation: radiation left from the time of the Big Bang. Since then the universe has cooled and this radiation has cooled as well. Originally, this radiation was the radiation permeating the universe shortly after the Big Bang, more precisely when the Universe was 105 years old and had a temperature of over 4,000 K; at that time light stopped interacting with matter. Light cooled down and now it represents the black-body radiation of a body at 2.7 K. (Remember: energy of radiation is inversely proportional to wavelength - as the radiation cooled, the wavelength stretched). There is a very good match between the Big Bang prediction and the measurement of the cosmic background radiation.
4) Particle physics-cosmology: The very beginning (the first three minutes!) of the universe was dominated by processes at high energies. With the help of the COSMOS TIMELINE table is possible to describe the different stages of the universe expansion: At 10-43 sec the temperature of the universe was around 1032 K and all forces of nature were unified (the electroweak, strong and gravitational forces). At 10-6 sec quarks condensed into baryons and mesons. At 3 min. the nuclei of the lightest elements (helium4, helium3, deuterium, and lithium) became stable. Only much later on, at 105 years after the Big Bang, atoms were created (nuclei and their electrons). The universe expand so rapidly that heavier elements are no formed at this point in time. They will form much later on in stars. The observed abundance of He in the universe stemming from the formation of H in the Big Bang has lead to insights into the number of possible families of neutrinos. Click here to see the Cosmos Timeline table. Let's now take a look to the problems of this theory.
1) The horizon problem: the cosmic background radiation, the remnant radiation from the time of the Big Bang, indicates that the universe at that time was very smooth. Actually, it was too smooth, in the sense that the radiation that we measure now is coming from regions of the early universe that they couldn't have been in communication with one another, since they are further apart than the space traveled by light since the beginning of the universe. Thus, regions of the early universe that couldn't have influenced each other had the same temperature to a precision of 1 in 100,000. This is possible but unlikely. 2) The lumpiness problem: Out of the smooth early universe, how did stars, galaxies and clusters of galaxies (i.e., lumpy matter) form? 3) The matter/antimatter problem: the conditions of the universe at the time of the Big Bang were such that an equal amount of matter and antimatter should have been produced. However, much less antimatter than matter is observed at the present time.