Ned Wright's Cosmology Tutorial - Part 1
The redshift caused by the expansion of the universe is properly called a . It is not the same as a Doppler shift produced by the Doppler effect. Doppler shifts are caused by an object's motion through space, whereas a cosmological redshift is caused by the every essence of the expansion of space.
Big Bang Theory: Evolution of Our Universe - Universe …
The term nucleosynthesis refers to the formation of heavier elements, atomic nucleiwith many protons and neutrons, from the fusion of lighter elements. The theory predicts that the early universe was a very hotplace. One second after the Big Bang, the temperature of the universe was roughly 10billion degrees and was filled with a sea of neutrons, protons, electrons, anti-electrons(positrons), photons and neutrinos. As the universe cooled, the neutrons either decayedinto protons and electrons or combined with protons to make deuterium (an of hydrogen). During the first three minutesof the universe, most of the deuterium combined to make helium. Trace amounts of lithiumwere also produced at this time. This process of light element formation in the earlyuniverse is called Big Bang nucleosynthesis (BBN).
By peering into the distance with the biggest and best telescopes in the world, astronomers have managed to glimpse exploding stars, galaxies and other glowing cosmic beacons as they appeared just hundreds of millions of years after the big bang. They are so far away that their light is only now reaching Earth, even though it was emitted more than 13 billion years ago.
What is the evidence for the Big Bang
The newfound gas clouds, as Fumagalli and his colleagues see them, existed about two billion years after the big bang, at an epoch of cosmic evolution known as redshift 3. (Redshift is a sort of cosmological distance measure, corresponding to the degree that light waves have been stretched on their trip across an expanding universe.) By that time the first generation of stars, initially comprising only the primordial light elements, had formed and were distributing the heavier elements they forged via nuclear fusion reactions into interstellar space.
Evidence for the Big Bang - TalkOrigins Archive: …
However, the Big Bang model can be tested further. Given a precise measurement of the abundance of ordinary matter, the predicted abundances of the other light elements becomes highly constrained. The is able to directly and finds a value of 4.6% (±0.2%), indicated by the vertical red line in the graph. This leads to predicted abundances shown by the circles in the graph, which are in good agreement with observed abundances. This is an important and detailed test of nucleosynthesis and is further evidence in support of the Big Bang theory. Had the results been in conflict, it would point to 1) errors in the data, 2) an incomplete understanding of the process of Big Bang nucleosynthesis, 3) a misunderstanding of the mechanisms that produce , or 4) a more fundamental problem with the Big Bang theory.
How Gravitational Lensing Shows Us Dark Matter! – …
The predicted abundance of deuterium, helium and lithium depends on the in the early universe, as shown in the figure at left. These results indicate that the yield of helium is relativelyinsensitive to the abundance of ordinary matter, above a certain threshold. We genericallyexpect about 24% of the ordinary matter in the universe to be helium produced in the BigBang. This is in very good agreement with observations and is another major triumph for the Big Bang theory.
Big Bang Theory: Evolution of Our Universe - Universe Today
Very recent observations of the 6Li isotope in halo stars reveal a 6Li plateau about 1000 times above the predicted big bang nucleosynthesis abundance. We calculate the evolution of 6Li versus redshift generated from an initial burst of cosmological cosmic rays (CCRs) up to the formation of the Galaxy. We show that the pre-Galactic production of the 6Li isotope can account for the 6Li plateau observed in metal-poor halo stars without additional over-production of 7Li. The derived relation between the amplitude of the CCR energy spectra and the redshift of the initial CCR production puts constraints on the physics and history of the objects, such as Population III stars, responsible for these early cosmic rays. Consequently, we consider the evolution of 6Li in the Galaxy. Since 6Li is also produced in Galactic cosmic-ray nucleosynthesis, we argue that halo stars with metallicities between [Fe/H] = -2 and -1 must be somewhat depleted in 6Li.