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The theory of BBN gives a detailed mathematical description of the production of the light "elements" deuterium, helium-3, helium-4, and lithium-7. Specifically, the theory yields precise quantitative predictions for the mixture of these elements, that is, the primordial abundances at the end of the big-bang.
Helium is the least water-soluble monatomic gas, [96] and one of the least water-soluble of any gas (CF 4, SF 6, and C 4 F 8 have lower mole fraction solubilities: 0.3802, 0.4394, and 0.2372 x 2 /10 −5, respectively, versus helium's 0.70797 x 2 /10 −5), [97] and helium's index of refraction is closer to unity than that of any other gas. [98]
Helium is the most common element in the universe after hydrogen, with a mass fraction of about 24%. Most of the helium in the universe was formed during Big Bang nucleosynthesis, but the amount of helium is steadily increasing due to the fusion of hydrogen in stellar nucleosynthesis (and, to a very slight degree, the alpha decay of heavy ...
Helium fusion first begins when a star leaves the red giant branch after accumulating sufficient helium in its core to ignite it. In stars around the mass of the Sun, this begins at the tip of the red giant branch with a helium flash from a degenerate helium core, and the star moves to the horizontal branch where it burns helium in its core.
Helium is inert - it does not react with other substances or combust - and its atomic number is 2, making it the second lightest element after hydrogen. Rockets need to achieve specific speeds and ...
However, the Alpher–Bethe–Gamow theory does correctly explain the relative abundances of the isotopes of hydrogen and helium. Taken together, these account for more than 99% of the baryonic mass of the universe. Today, nucleosynthesis is widely considered to have taken place in two stages: formation of hydrogen and helium according to the ...
A major advantage is that this gas is noncombustible. But the use of helium has some disadvantages, too: The diffusion issue shared with hydrogen (though, as helium's molecular radius (138 pm) is smaller, it diffuses through more materials than hydrogen [4]). Helium is expensive. Although abundant in the universe, helium is very scarce on Earth.
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