Announcements Reading assignment for next time: read The Degenerate Era, The Black Hole Era, The Dark Era and The Conclusion 1st Quarter Observing Night tonight: cloudy and cold so it will be inside. Set-up will start at 6:45pm. Meet in the 3rd floor B-wing hallway by the astronomy storage room.

Colored Card Question The current cosmological decade is The 1st The 10th The 13th The 25th None of the above

Another colored card question The last stars will die out in which cosmological decade? The 1st The 14th The 23rd The 50th I don’t have a clue.

The Primordial Era -50 < h < 5

The four forces of nature in the Primordial Era

Cosmological Inflation The “bang” of the Big Bang

Inflation solves the flatness problem

Inflation solves the Horizon Problem

An Analogy for the Expanding Universe Where is the center of this universe? Is it “in” the universe?

Colored Card Questions ClassAction website Cosmology module Centerless Expansion Models Effects of Expansion Universe Changes

In-class Activity Do “The Big Bang” lecture-tutorial. Work together in groups of two or three. You have 20 minutes.

Recombination Recombination is a misnomer. The electrons and protons had never been together before this time

Stretching the CMB

Where did all the matter come from? Electron-positron pair production and annihilation

Virtual particles and vacuum energy There had to have been some small number of cases where a particle was created without an antiparticle. We still don’t understand how that can be.

What is the atomic content of the Universe? The Big Bang theory predicts that the universe is made of hydrogen and helium with traces of deuterium, tritium, helium-3, lithium and beryllium