Big Bang nucleosynthesis
Δημοσιεύτηκε στις 27 Δεκ 2015
In
physical cosmology, Big Bang nucleosynthesis refers to the production
of nuclei other than those of the lightest isotope of hydrogen during
the early phases of the universe. Primordial nucleosynthesis is believed
by most cosmologists to have taken place from 10 seconds to 20 minutes
after the Big Bang, and is calculated to be responsible for the
formation of most of the universe's helium as the isotope helium-4,
along with small amounts of the hydrogen isotope deuterium, the helium
isotope helium-3, and a very small amount of the lithium isotope
lithium-7. In addition to these stable nuclei, two unstable or
radioactive isotopes were also produced: the heavy hydrogen isotope
tritium; and the beryllium isotope beryllium-7; but these unstable
isotopes later decayed into 3He and 7Li, as above.
Essentially all of
the elements that are heavier than lithium and beryllium were created
much later, by stellar nucleosynthesis in evolving and exploding stars.
This video is targeted to blind users.
Attribution:
Article text available under CC-BY-SA
Creative Commons image source in video
physical cosmology, Big Bang nucleosynthesis refers to the production
of nuclei other than those of the lightest isotope of hydrogen during
the early phases of the universe. Primordial nucleosynthesis is believed
by most cosmologists to have taken place from 10 seconds to 20 minutes
after the Big Bang, and is calculated to be responsible for the
formation of most of the universe's helium as the isotope helium-4,
along with small amounts of the hydrogen isotope deuterium, the helium
isotope helium-3, and a very small amount of the lithium isotope
lithium-7. In addition to these stable nuclei, two unstable or
radioactive isotopes were also produced: the heavy hydrogen isotope
tritium; and the beryllium isotope beryllium-7; but these unstable
isotopes later decayed into 3He and 7Li, as above.
Essentially all of
the elements that are heavier than lithium and beryllium were created
much later, by stellar nucleosynthesis in evolving and exploding stars.
This video is targeted to blind users.
Attribution:
Article text available under CC-BY-SA
Creative Commons image source in video
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