Big Bang and First Light
How was light created, going off of the Big Bang theory? I
realize that several sub-atomic particles collided, but how did
light become? Was light one of the particles that collided, or what?
Questions about the early universe are always interesting. The short answer
is that as long as the universe has had energy, it has had light in one form
or another. Many of the most common (especially in our every day circumstances)
particle interactions involve particles of light. Light particles (photons) were
certainly present in the early universe. This includes not just the narrow range
of visible light, but photons of all energies including very, very high energy
photons as well as low energy ones.
Light particles (photons) are different from other particles such as protons and
electrons in a number of ways. One of those differences is that (within a few given
rules) photons can be more easily created and destroyed than electrons, protons, and
their ilk. In fact it is entirely possible to make photons through processes that do
not make these other particles.
There is an interesting question related to light and the early universe that you
might enjoy thinking about. When did the universe become "transparent?" In the early
universe, things we very dense and very hot. As things cooled there was a point at
which we had protons and neutrons forming nuclei, but those nuclei and the electrons
still had too much energy to form atoms like we are used to seeing today (such as
hydrogen and helium). There were lots of photons at this point too, but they would
scatter around very strongly from all the electrons and nuclei, never really going
anywhere in particular, just randomly being scattered and reflected about. In this
respect the universe was a very "opaque" place. Once the universe cooled enough for
the electrons and nuclei to form atoms this changed. The photons no longer strongly
interacted with the more stable atoms and began proceeding through the universe in a
more "unhampered" way and the universe became transparent to light. These photons are
still traveling today and can be detected as the "cosmic microwave background radiation."
Michael S. Pierce
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Update: June 2012