Cosmology and the Origin of Life


Overview of the First Three Minutes:

Observations:

The observations indicate that the universe is expanding and cooling (just like an expanding gas cools). Hence, in the past the Universe was hotter and denser than it is currently. Extrapolation to the distant past demands that the Universe was very hot and very dense.

The condition of thermal equilibrium means that the behavior of the Universe at any epoch is dependent on its Temperature.

At early times, the energy density of the photons was so high that you could get particle creation from the photon field and/or energy creation from the matter field.

photon+photon <=====> particle + anti-particle

The kinds of particles +anti-particles that are created depends strictly on the average energy per photon which depends only on the temperature.

If photon energy is less than mpc2 then mp can't be created; only particles with mass less than mp will be created.

Since a proton is 2000 times heavier than an electron, the window of opportunity for creating electrons from the photon field is a lot longer than for creating protons.

In the very early Universe, lots of strange pairs of particles could have been produced from Quantum Fluctuations --> we know very little of this physics.

10-6 seconds to 0.1 second was the window of opportunity for creating protons and neutrons and other "normal" particles.

The Universe was opaque to neutrinoes prior to it being a second old and this kept the abundance of protons equal to that of neutrons.

At 1 second the neutrinoes escape and the neutrons start to decay. The only thing that prevents their decay is zero is the formation of atomic nuclei via thermonuclear fusion. This fusion epoch starts around t=3 minutes and lasts until t=15 minutes. The proton-to-neutron ratio at the start of this epoch is 7-to-1. This ratio makes a solid prediction about The Helium Abundance of the Universe.

Three big unknowns in the above are:

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