ICY SCIENCE: SCIENCE SPACE ASTRONOMY Spring 2014 | Page 80

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even higher energies even gravity would be indistinguishable. At energies this high, the Universe would
have been so hot and dense no one force could have been separate. This stage ended after 10-35seconds
when the Universe underwent a bout of inflation allowing temperature and energy levels to drop enough
for the forces to begin to separate.
After this period of rapid expansion came the Hadron Epoch. As the name suggests, during this period of
time the Universe was filled with hadrons such as protons and neutrons. During this phase the Universe
cooled to an extent where the first elements could begin forming out of the lighter hadrons. The Universe
would have been a violent place at this time as along with particle formation, antiparticles were also created
causing collision and annihilation between particle and antiparticle pairs. The last of the four unified forces
also separated, creating a very different Universe to how it had been previously.
The next period in the development of the Universe – the Lepton Epoch – lasted until 102seconds after the
Big Bang. A Lepton is a particle of light, so it was during this phase that the first electron and positron pairs
were created. A s in the Hadron Epoch, a period of annihilation followed until an equilibrium was reached
and the number of protons, neutrons, and electrons became stable. It was now that nucleosynthesis could
begin, allowing the first heavy elements to form.
The Nuclear Epoch followed and lasted for the next 1,000 years. With temperatures cooling from 109K to
around 3,000K during this time, it became cold enough for nuclear fusion between protons and neutrons
to occur. Collisions at these temperatures allowed for the creation of a heavy form of Hydrogen – known
as Deuteron – plus an energy release which was used to fuse another proton to the Deuteron nucleus producing Helium-3. Temperatures and radiation levels at this time were still too high to allow the formation of
anything heavier, but soon became too low to form new elements. This fixed the make-up of the Universe
at 75% Hydrogen, 25% Helium, and trace amounts of Deuteron, Lithium, Beryllium, and Boron.

ICY SCIENCE | QTR 2 SPRING 2014