Re: What are some examples of energy converting to matter?

It was really embarrassing to realize I couldn't think of any examples off
the top of my head. So I turned to my trusty officemate Glen and repeated
your question.

"Pair production and the Big Bang," he said and turned resolutely back to
his terminal.

At this point, I smacked myself in the forehead.

You correctly pointed out that the annihilation of particle-antiparticle
pairs releases energy in the form of photons. However if you'd have just
gone back to where these particles come from, you would have had one of the
answers for yourself. 

Due to the quantum-mechanical nature of the universe,
the vacuum of space often spontaneously gives rise to particle-antiparticle
pairs, which subsequently annihilate because not only are they created
close together, but they are mutually attracted because of their opposite
charges. This creation of these sets of particles is called pair production
or fluctuations in the quantum field and is one example of
energy-into-matter. You may not think that a cubic meter of vacuum could
have any energy, but you'd be surprised.

If there is pair production near the event horizon of a black hole, an
interesting effect occurs. Instead of the particles touching and
annihilating, it's possible for one particle to be torn away from its
partner because of its greater proximity to the black hole. The other
particle can escape the black hole's gravity and be radiated into space.
This is known as Hawking radiation and if it happens enough, can lead to
the evaporation of a black hole.

Another way in which energy can turn into matter is the what's described by
the Big Bang theory. First: there was nothing. Then, there was an explosion
which released a lot of energy. Eventually, the universe expanded and
cooled enough for some matter to form out of this energetic soup. After
more cooling, the elementary particles were able to form atoms. And the
rest, as they say, is history.

Thanks for submitting that question. It was a good one.