Only tiny amounts of nuclei beyond helium are formed, because nucleosynthesis of heavier elements is difficult and Therefore, the only stable nuclides created by the end of Big Bang nucleosynthesis are protium (single proton/hydrogen nucleus), deuterium, helium-3, helium-4, and The amounts of each light element in the early universe can be estimated from old galaxies, and is strong evidence for the Big Bang.Until now, the universe's large scale dynamics and behaviour have been determined mainly by radiation—meaning, those constituents that move relativistically (at or near the speed of light), such as photons and neutrinos.From this point on, and for several billion years to come, the presence of dark matter accelerates the The properties of dark matter that allow it to collapse quickly without radiation pressure, also mean that it cannot At around 100,000 years, the universe has cooled enough for helium hydride, the first molecule, to form.About 370,000 years after the Big Bang, two connected events occurred: recombination and At around 370,000 years, the universe has cooled to a point where free electrons can combine with the hydrogen and helium Directly combining in a low energy state (ground state) is less efficient, so these hydrogen atoms generally form with the electrons still in a high energy state, and once combined, the electrons quickly release energy in the form of one or more photons as they transition to a low energy state. Sakharov’s second innovative idea attempted to explain gravity as originating from properties of the quantum vacuum. In doing so, they completely shift how they interact. About 4 billion years ago the expansion gradually began to speed up again. Their light shows evidence of elements such as carbon, As the first stars, dwarf galaxies and quasars gradually form, the intense radiation they emit reionizes much of the surrounding universe; splitting the neutral hydrogen atoms back into a plasma of free electrons and protons for the first time since recombination and decoupling. The entropy density is
It will continue to appear very similar for many billions of years into the future. By far the most accepted understanding is that this is due to an unknown form of energy which has been given the name "dark energy".The universe has existed for around 13.8 billion years, and we believe that we understand it well enough to predict its large-scale development for many billions of years into the future—perhaps as much as 100 billion years of cosmic time (about 86 billion years from now). The question of nuclear arms was, after all, well within his professional competence. This change from charged to neutral particles means that the The photons released by these newly formed hydrogen atoms initially had a After recombination and decoupling, the universe was transparent and had cooled enough to allow light to travel long distances, but there were no light-producing structures such as stars and galaxies. This initial period of the universe's chronology is called the "During the earliest moments of cosmic time, the energies and conditions were so extreme that current knowledge can only suggest possibilities, which may turn out to be incorrect.