Cosmology Chapter 5 & 6  Overheads


What three observations support the Big Bang Theory? The early big bang model also made a prediction about how much anti-matter there should be in the universe. What is Anti-matter?
Our world (depicted on the right) Mark Bergsma - Photographer
    is not made from anti-matter

Every particle has its anti-particle
For example there are protons and anti-protons.
Electrons and anti-electrons (called positrons)
Anti-matter has properties that are the same as matter
    (but with opposite charge)
Matter and anti-matter destroy each other
    (if they come in contact.)

This produces energy (E = mc2)
Likewise, energy can produce matter + anti-matter
The Big bang produced lots of energy.
Part of this energy became matter and anti-matter.

Thus the big bang model predicted that there should be just
    as much matter as anti-matter.

Everything in our solar system is made from matter.
But how do we know about other galaxies?
Perhaps there are vast areas of the universe that are totally anti-matter separated from matter by leidenfrost layers.

Light from galaxies can’t tell us if they are matter or antimatter
But high energy particles from other galaxies (cosmic rays) formed by violent events like supernovas can.

But you need to catch them high in the atmosphere before they have a chance to annihilate with the atmosphere.

Anti-helium can be formed by regular (matter) stars. But anti-carbon can’t. So finding lots of anti-carbon would have supported the big bang theory.

It wasn’t until 1956 that physicists discovered that anti-matter and matter don’t behave exactly the same.

They violate CP symmetry (their chemical and physical properties aren’t exactly the same).

 The slight difference in their properties lead to a slight

(one part in a billion) excess of matter over anti.

Soon after the big bang, when the universe was Hot

(there was lots of spare energy) matter and antimatter

were continually forming and annihilated.

A few thousand years later, the universe had cooled down enough 
    that matter would no longer form spontaneously

All the matter and anti-matter annihilated for the last time producing light
    (this light is the Cosmic Background Radiation, that we can still see today!!!)

But, because there was a slight excess of matter over antimatter, there was a little matter left over.
    (your made  up of leftover matter, but don’t feel bad, so is everything in the universe.)

Smoot wanted to use the cosmic background radiation to determine the earth's velocity through space.
    He did this by using the Doppler effect and U2 airplanes.  (a U2 airplane is not shown at right)
    It was very difficult.