The Big Bang

CMBR

Discussion Why can’t the CMBR be from a population of unresolved stars at high redshift?

Discussion If I proposed building an x-ray satellite in order to observe the CMBR at a time when the Universe was hotter than 3000 K, would you fund such a mission?

Maybe the Universe starts here?

Discussion If you take a bunch of protons and smash them together what would you expect to happen?

proton – proton chain

Proton-Proton chain too slow Even at 15 million K, it takes on average 14 billion years at a rate of 100 million collisions per second to fuse two protons to produce a deuterium atom in the Sun’s core.

Matter and photons The higher the temperature of the CMBR, the higher the energy of the photons The higher the energy, the more massive the particles that can be created

Protons and neutrons At temperatures greater than K, CMBR photons had enough energy to create proton- antiproton and neutron-antineutron pairs

H to He ratio Because the Universe has about 75% H and 25% He by weight, we know that there must have been 7 protons for every neutron at the time of nucleosyhthesis.

Matter and Energy in the universe

Electric and Magnetic Waves

General Relativity or Quantum Mechanics? These two theories disagree inside a black holes. Because we can never see inside a black hole does it even matter?

Unified Field Theory Einstein tried to explain the electromagnetic force using curved spacetime and failed. Was accomplished by Kaluza, but it required four space dimensions and one time dimension

Messenger particles Today, most scientists believe that the transmission of a force must be quantized Forces are caused by the exchange of virtual particles

The 4 fundamental forces

What’s the difference? The difference between the forces is their strength and the distance over which they can act. Electromagnetism and gravity can act over infinite distances. The nuclear forces can act only over very small distances.

But if the observable universe is very small, there is no effective difference between the range of the forces. Furthermore, the more energy you give to the messenger particles the stronger the force will appear.

Electroweak force sec after Big Bang Temperature K Observable universe about 1 mm in diameter Photons of the CMBR had enough energy to turn into W particles No difference between the electromagnetic force and the weak force.

The Electronuclear force At sec Temperature K No difference between the strong, weak, or electromagnetic forces.

What caused inflation? A phase change may have caused the inflationary expansion

Phase changes Water below 32 degrees F will undergo a phase change from a liquid to a solid. The properties of liquid water are very different from the properties of ice.

It was the freezing out of the strong nuclear force that is believed to have caused inflation.

A brief history of the Universe Decay of the “false vacuum”

Plank Era Time: 0 to sec Quantized gravity?

Grand Unification Era Time: sec to sec Strong, weak nuclear and electromagnetic forces are the same

Electroweak Era Time: sec to sec Strong force freezes out causing inflation Creation of particles Weak nuclear and electromagnetic forces are the same

Particle Era Time: sec to sec Weak nuclear force freezes out Quarks confined to protons and neutrons

Era of nucleosynthesis Time: sec to 5 min Protons and neutron form deuterium, tritium, helium, lithium and beryllium

Era of Nuclei Time: 5 min to 380,000 years Photons coupled to ions CMBR acoustical oscillations

Era of atoms time: 380,000 years to 430 million years Gravitation collapse of over dense regions

Re-ionization Time: 430 million years to 1 billion years First stars form, probably in globular clusters

Dark matter simulation

The future The universe is likely to expand forever Matter/dark matter will become more clumped together into larger isolated galaxies Once all H gas is used up galaxies will become redder and dimmer until all stars go out

Exam Thursday Same format as last exam. Covers all reading assignments not included on the last exam. One sheet of notes, writing on one side.