The Official String Theory Web Site:--> Cosmology :--> The Big Bang :--> Hydrogen forms

Protons and electrons form hydrogen

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TIME: 500,000 years

. By this time there are plenty of protons and other light nuclei in the universe, and there are also plenty of electrons. But until now, the Universe has been too hot and dense for the electrons to be captured for very long by a nucleus, without being smacked out of orbit by collisions with other particles.
. When the temperature of the Universe cools to the point where the average speed of an average electron isn't high enough to escape capture by a proton, then atoms start to form. Since the only nuclei that exist are hydrogen, helium and lithium, the first atoms to exist are therefore hydrogen, helium and lithium.
. The heavier elements, such as carbon which is necessary for life as we know it to evolve, are created in a much more interesting manner.

How old is the Universe? // Structure of the Universe // The Big Bang // Before the Big Bang? // What about string theory?

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