Download Physical Cosmology

Physical Cosmology
Dr Ian Parry
Tel: 01223 337092
Room: H57
E-mail: [email protected]
Lectures: Mon 10am, Thurs 10am
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Physical Cosmology
Course Schedule
What is cosmology about?
Cosmology from Greek s world
s
word, reasoning, theory
Physical Cosmology studies the Universe as a whole, draws
on many branches of Physics.
It tries to explain the following properties of the Universe:
•
•
•
•
geometry, dynamics
content (baryons, photons, neutrinos, dark matter, dark
energy)
spatial distribution
time evolution (thermal history, growth of structure,
galaxy formation)
Text books
http://www.nap.edu/readingroom/books/cosmology
http://www.nap.edu/readingroom/books/cosmology
Sequence of events
• At z=1100 the Universe has
cooled down to 3000K .
Hydrogen becomes neutral
(“Recombination”).
• At z <~ 20 the “first” star
(clusters)/small galaxies form.
• At z ~ 6-10 these gradually
photo-ionize the hydrogen
in the IGM (“Reionization”).
• At z<6 galaxies form most of
their stars and grow by merging.
• At z<1 massive galaxy clusters
are assembled.
The whole sky as seen by WMAP
WMAP = Wilkinson Microwave Anisotropy Probe
The Standard Model
Cosmology – early history
“The Greeks”
Aristotle (384-322 BC)
Ptolemy (100-170)
“The Renaissance”
Copernicus (1473-1543)
Brahe (1546-1601)
Kepler (1571-1630)
Galileo (1546-1642)
Newton (1643-1727)
geocentric cosmology heavenly
bodies move on spheres
epicycles
Earth not at the centre of the
Universe (Copernican principle)
detects supernova, measures
planetary motion
elliptic planetary motion, Kepler’s
laws
observes planets with telescope
detects moons of Jupiter
calculus, Newton’s laws,
mechanics, deterministic cosmology
Cosmology – history continued
1683
Newton’s Principia
1750
Structure of Milky Way
(Wright, Kant, Herschel)
1915
1927
George Lemaitre proposed the
“primeval atom”: expansion implies
a singularity in the past
1948
Nucleosynthesis of light elements in
early universe and prediction of the
CMB (Gamow, Alpha, Herman)
1948
Steady-state theory proposed
(Hoyle, Bondi, Gold)
1949
Hoyle coins phrase “big bang”
Einstein’s General relativity
1916/7 Relativistic Cosmologies
(Einstein, Friedman, Lemaitre,
de Sitter)
1920
Curtis/Shapley debate on
galaxies
1957
Nucleosynthesis of heavy elements
(Burbidge, Burbidge, Hoyle,
Fowler)
1924
Hubble establishes Andromeda
nebula to be extragalactic
1965
Cosmic microwave background
(CMB) discovered (Penzias,
Wilson)
Late
1920’s
Expansion of Universe
established, Hubble’s law
Cosmology – recent history
1980’s
Hot/Cold Dark Matter; Large
Scale
Structure in galaxy
distribution measured
1992
Detection of CMB fluctuations
by COBE satellite
late
1990s
increasing observational evidence
for cosmological constant/dark
energy, e.g. from type Ia
supernovae
2000
Detection of “acoustic peaks” in
CMB power spectrum by balloon
experiments
2003
announcement of results of
WMAP satellite
The cosmic microwave background photons were last scattered
when the Universe was only 380 000 years old.
Scales/Distances
Earth
Moon
Sun
1.3 x 107 m
3.6 x 106 m
1.4 x 109 m
distance to
Sun
1.5 x 1011m
centauri
Galactic centre
M31 Andromeda
4.0 x 1016 m
2.6 x 1020 m
2.2 x 1022 m
Virgo cluster
4.6 x 1023 m
Hubble radius
1.4 x 1026 m
1 parsec =3.08 x 1016 m
pc, kpc, Mpc, Gpc
k kilo
103
M Mega 106
G Giga 109
Cosmological Principles
• Copernican Principle:
Earth is not at the centre of the Universe
• Perfect Cosmological Principle:
The Universe is homogeneous, isotropic and static .
• Anthropic Principle:
The Universe must have conditions which are compatible with
our existence
Multiverses
• The Cosmological Principle (agreed upon by most):
The Universe is homogeneous and isotropic
homogeneous: the same everywhere no point
special
isotropic:
no preferred direction
isotropic everywhere
homogeneous
homogeneous
isotropic