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Originally Posted by Edge
We all know that we can make energy out of matter, it's a fact. However, if I may ask, can matter be created out of energy?
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As previous posts have noted, pair production – the changing of photons into positrons (anti-electrons) and electrons – is a widely accepted phenomena. Processes that create other subatomic particles – in particular, protons and anti-protons – are also known, but thought to occur much less frequently in nature – perhaps only in conditions like those found in the targets of particle accelerators.
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or to put it better, has it been done or observed?
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Yes, though, as with most sub-atomic phenomena, what is observed is indirect, and requires theoretical interpretation. Note that, since the 1997 article linked to be Tormod, CERN has actually succeeded in creating stable atoms of created matter. They actually created anti-matter – a few tens of thousands of atoms of anti-hydrogen, but matter could have been made by the same process. Matter being much less interesting than anti-matter, they concentrated on it instead.
Several folk have noted that there’s a kind of pair production that does not require a photon, but instead appears spontaneously in vacuum –
vacuum fluctuations. One of the best known, and easiest to produce demonstrations of is the
Casimir_effect, predicted in 1948 and first experimentally measured in 1997.
Bo asks
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Originally Posted by Bo
How do these people you refer to think that the universe went from radiation dominated to matter dominated? radiation is energy, matter is energy; they can convert into each other.
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While correct in principle, I think this provides an inaccurate picture of the current consensus of the
timeline of the Big Bang. According to it, the early universe was all energy in the form of bosons that had not yet separated into the 4 fundamental forces, then, about 10^-33 seconds after the Big Bang, matter in the form of the first fermions, free quarks and antiquarks came into existence. Annihilation of these quarks and antiquarks produced the first photons. The surviving quarks don’t form stable nuclear particles until later, 10^-5 seconds ABB.
The usual meaning of the phrases “radiation dominated” and “matter dominated” involves the time, around 379,000 years ABB, when electrons were captured by atomic nuclei, and the universe became transparent, marking the end of the “primordial” age and the beginning of the current, “stellariferous” one, where photons interact less frequently with electrons. At this time, the ratio of matter (fermions) to energy (bosons), including radiaton (photons) was very close to its current (about 10^10 years ABB) value, at which it’s expected to remain until “deep time”, about 10^14 years ABB.
Has matter been created out of energy?
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