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In physics, the fundamental interactions or fundamental forces are the interactions that do not appear to be reducible to more basic interactions. There are four fundamental interactions known to exist: [1] gravity. electromagnetism. weak interaction.
Each individual reaction produces only a tiny amount of energy, but because enormous numbers of these reactions occur constantly, they produce all the energy necessary to sustain the star's radiation output. In comparison, the combustion of two hydrogen gas molecules with one oxygen gas molecule releases only 5.7 eV.
The universe also has vast regions of relative emptiness; the largest known void measures 1.8 billion ly (550 Mpc) across. Comparison of the contents of the universe today to 380,000 years after the Big Bang as measured with 5 year WMAP data (from 2008). Due to rounding errors, the sum of these numbers is not 100%.
Comparison of the energy output (ε) of proton–proton (PP), CNO and Triple-α fusion processes at different temperatures (T). The dashed line shows the combined energy generation of the PP and CNO processes within a star. Helium accumulates in the cores of stars as a result of the proton–proton chain reaction and the carbon–nitrogen ...
The CNO cycle (for carbon – nitrogen – oxygen; sometimes called Bethe–Weizsäcker cycle after Hans Albrecht Bethe and Carl Friedrich von Weizsäcker) is one of the two known sets of fusion reactions by which stars convert hydrogen to helium, the other being the proton–proton chain reaction (p–p cycle), which is more efficient at the ...
Brown dwarfs are substellar objects that have more mass than the biggest gas giant planets, but less than the least massive main-sequence stars.Their mass is approximately 13 to 80 times that of Jupiter (M J) —not big enough to sustain nuclear fusion of ordinary hydrogen (1 H) into helium in their cores, but massive enough to emit some light and heat from the fusion of deuterium (2 H).
In physical cosmology, Big Bang nucleosynthesis (also known as primordial nucleosynthesis, and abbreviated as BBN) [1] is the production of nuclei other than those of the lightest isotope of hydrogen ( hydrogen-1, 1 H, having a single proton as a nucleus) during the early phases of the universe. This type of nucleosynthesis is thought by most ...
For example, an electron neutrino produced in a beta decay reaction may interact in a distant detector as a muon or tau neutrino. [7] [8] The three mass values are not yet known as of 2024, but laboratory experiments and cosmological observations have determined the differences of their squares, [9] an upper limit on their sum (< 2.14 × 10 − ...