The Big Bang: Fact or Fiction?

The Big Bang

Fact or fiction?

Dr Cormac O’Raifeartaigh

The expanding universe (1929)

many galaxies

moving apart

The origin of the universe

rewind graph: universe converges

infinite density, temp

beginning of time: Big Bang? Georges Lemaitre

Expanding and cooling ever since

t~ 14 billion yr

• gravity caused by sun’s mass

Newton

• planet orbits due to gravity

Newton’s gravity

2r

MmGF

What is pushing out?

Modern theory of gravity

gravity = curvature of space-time

• space + time = space-time

• space-time not fixed

• affected by mass

General theory of relativity

Einstein

Relativity and the expanding U

dynamic U

expand or contract

depends on mass

Apply Einstein’s gravity to Universe

Alexander Friedmann

Evidence II: Composition of the elements

U = 75% H, 25% He

ObservedGeorges Gamow

BB Prediction

Heavier elements: 0.1%

Formed in stars

Evidence III:Cosmic background radiation

BB prediction

radiation leftover from BB

low temperature

low frequency

Alpher, Gamow and Herman

Cosmic microwave background (1965)

radio interference

low frequency

temperature 3 K

Penzias and Wilson

Echo of Big Bang

Observed

Modern measurements

• accurate CMB spectrum

• homogeneous?

• how do galaxies form?

COBE satellite (1992)

WMAP satellite

WMAP satellite (2002)

• highly homogeneous• flat universe • ev idence for inflation

Inflation

explains galaxy formation

explains flatness of U

solves horizon problem

Hyper- expansion

immediately after BB

Alan Guth

New surprises

U speeding up

Supernova

U flat

Dark energy

Outstanding puzzles

Nature of inflation?

Nature of dark energy ?

Singularity at time zero?

Further reading: ANTIMATTER

Summary

The Big Bang model

14 billion years ago, universe concentrated at a point

Primordial explosion of matter, energy, space and time

Universe expanding and cooling ever since

Misnomer: singularity problem

Cosmological model

Known matter: 4%

Dark matter: 23%

Dark energy: 73%

Flat universe

Evidence for general relativity

• bending of light by gravity

• time stretching by gravity

• black holes