Cosmology and the Origin of Life

Epoch #4:

• time = 14 seconds
• temperature = 3 billion degrees

Electrons and anti-electrons now freeze out. These are the lighest particles that we know of and hence have the longest formation window.

All these electron and anti-electron pairs now annihilate thus producing the final photon background with characteristics such that there are one billion photons for each particle.

Stable nuclei (e.g. Helium) can't form yet because the Universe is expanding very fast and is still filled with very high energy photons.

At this time, there are 83% protons and 17% neutrons and the neutrons are decaying to 0%.

Epoch #5:

• time = 3 minutes
• temperature = one billion degrees

Conditions in the universe (temperature and density) are now very similar to conditions inside a star.

Universe is now 87% protons and 13% neutrons

p/n ratio is 7

What prevents the decay of neutrons?

Unless neutrons are bound in an atomic nuclei, they will decay. Therefore we need to make atomic nuclei.

How do we do this?

Thermonuclear Fusion

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