the big bang. cmbr discussion why can’t the cmbr be from a population of unresolved stars at high...

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 1011 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

10-12 sec after Big BangTemperature 1015 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 10-35 sec Temperature 1027 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 10-43 sec

Quantized gravity?

Grand Unification Era

Time: 10-43 sec to 10-38 sec

Strong, weak nuclear and electromagnetic forces are the same

Electroweak Era

Time: 10-38 sec to 10-10 sec

Strong force freezes out causing inflation

Creation of particles

Weak nuclear and electromagnetic forces are the same

Particle Era

Time: 10-10 sec to 10-3 sec

Weak nuclear force freezes out

Quarks confined to protons and neutrons

Era of nucleosynthesis

Time: 0.001 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.