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The Big Bang: Fact or Fiction?. The Big Bang. Fact or fiction?. Dr Cormac O’Raifeartaigh. The expanding universe (1929 ). many galaxies moving apart. rewind graph: universe converges infinite density, temp beginning of time: Big Bang?. The origin of the universe. Georges Lemaitre.

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the big bang fact or fiction
The Big Bang: Fact or Fiction?

The Big Bang

Fact or fiction?

Dr Cormac O’Raifeartaigh

the expanding universe 1929
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?

The origin of the universe

Georges Lemaitre

t~ 14 billion yr

Expanding and cooling ever since


Newton’s gravity

  • planet orbits due to gravity
  • gravity caused by sun’s mass

What is pushing out?

modern theory of gravity
Modern theory of gravity

General theory of relativity

  • space + time = space-time
  • space-time not fixed
  • affected by mass


gravity = curvature of space-time

r elativity and the expanding u
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


Evidence II:Composition of the elements

BB Prediction

Georges Gamow

Heavier elements: 0.1%

Formed in stars

evidence iii cosmic background radiation
BB prediction

radiation leftover from BB

low temperature

low frequency

Evidence III:Cosmic background radiation

Alpher, Gamow and Herman

cosmic microwave background 1965
radio interference

low frequency

temperature 3 K

Cosmic microwave background (1965)


Penzias and Wilson

Echo of Big Bang

modern measurements
Modern measurements
  • accurate CMB spectrum
  • homogeneous?
  • how do galaxies form?

COBE satellite (1992)

wmap satellite
WMAP satellite
  • highly homogeneous
  • flat universe
  • ev idence for inflation

WMAP satellite (2002)

  • explains galaxy formation
  • explains flatness of U
  • solves horizon problem

Alan Guth

Hyper- expansion

immediately after BB

new surprises
New surprises
  • U speeding up


  • U flat
  • Dark energy
outstanding puzzles
Outstanding puzzles
  • Nature of inflation?
  • Nature of dark energy ?
  • Singularity at time zero?

Further reading: ANTIMATTER

the big bang model
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
Cosmological model

Known matter: 4%

Dark matter: 23%

Dark energy: 73%

Flat universe

evidence for general relativity
Evidence for general relativity
  • bending of light by gravity
  • time stretching by gravity
  • black holes