Cosmology
HNRT 227 Chapter 15
27 October 2015
Great Idea:
The universe began billions of years ago in the big bang
and it has been expanding ever since.
1
Chapter Outline
•
•
•
•
•
Galaxies
The Redshift and Hubble’s Law
The Big Bang
The Evolution of the Universe
Dark Matter and Ripples at the
Beginning of Time
• The End of the Universe
2
Galaxies
3
The Nebula Debate
• Nebulae
– Cloud-like objects
• Shapley vs. Curtis
– Debate over distance of nebulae
4
Edwin Hubble (with Milt Humason)
and the Discovery of Galaxies
• Hubble
– Largest telescope in his day
– Used Cepheid variable stars to
measure distance to nebulae
• Galaxies
– Hubble examined a multitude
of galaxies
• Categorized and measured
• Cosmology
– All galaxies outside our Local
Group are moving away from us
• Doppler shift
5
Kinds of Galaxies
•
•
•
•
Spiral
Elliptical
Irregular (& Dwarf)
Active galaxies
– Blazars, Quasars, Radio,
Seyfert
6
Properties of Galaxies
Property
Spirals
Ellipticals
Irregulars
Mass/M of Sun
109 to 4x1011
105 to 1013
108 to 3x1010
Luminosity/L of Sun
108 to 2x1010
3x105 to 1011
107 to 3x109
3x103 to 7x105
3x103 to 3x104
Diameter (light years) 16x103 to 8x105
% of galaxies
77%
20%
3%
National Optical Astronomy Observatory images
From this table, consider which galaxies are
the most and least massive, most and least
luminous, and largest and smallest in size.
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Active Galaxies
8
• Hubble
Deep
Field
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iClicker Question
•
How many stars are in a galaxy?
–
–
–
–
–
A
B
C
D
E
ten to a hundred
a thousand to a million
millions to hundreds of billions
hundreds of billions to trillions
both C and D above
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iClicker Question
•
The branch of science devoted to the
study of the structure and history of
the entire universe is:
–
–
–
–
–
A
B
C
D
E
oleology
biology
cosmology
nebuology
astrology
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iClicker Question
•
The most common galaxies in the
universe are:
–
–
–
–
–
A
B
C
D
E
elliptical
spiral
irregular
barred spiral
both B and C above
12
iClicker Question
•
–
–
–
–
–
Quasars are wild, explosive, violent objects
pouring vast amounts of energy into space
each second from an active center no larger
than our solar system. Where do
astronomers suggest the energy of quasars
comes from?
A
B
C
D
E
combustion of hydrogen
black holes
uranium fission
carbon fusion
they have no suggestion at this time
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The Redshift and Hubble’s Law
14
The Redshift and
Hubble’s Law
• Redshift
• Hubble’s Law
– The farther a galaxy,
the faster it recedes
– V=H x d
15
iClicker Question
•
Light emitted from elements in distant
(outside Local Group) galaxies is:
–
A
–
B
–
C
the same wavelength as light
from atoms on Earth
redshifted compared to light from
atoms on Earth
blueshifted compared to light from
atoms on Earth
16
iClicker Question
•
Hubble’s law says:
–
–
–
A
B
C
–
D
galaxies are all moving at constant rates
if anything can go wrong, it will
the farther away a galaxy outside of our
Local Group is, the faster it recedes
all galaxies are moving away from
our galaxy
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iClicker Question
•
Hubble’s law reveals what aspect of
our universe?
–
–
–
–
A
B
C
D
it is in equilibrium
it is expanding
it is collapsing
none of the above
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The Big Bang
19
The Big Bang
• Big Bang
– Best model of the formation of the
universe
– The universe began at a specific time in the
past, and it has been expanding ever since
20
The Large-Scale
Structure of the Universe
• The Local Group
– Milky way,
Andromeda galaxy,
and others
• Groups (smaller
number), clusters,
superclusters
– Regular and irregular
• Voids
21
Some Useful Analogies
Raisin-Bread
Dough Analogy
Expanding
Balloon Analogy
22
Evidence for the Big Bang
• The Universal Expansion
– Steady-state universe
• The Cosmic Microwave Background
– Penzias and Wilson
• End of steady-state theory
• The Abundance of Light Elements
– Hydrogen, helium, very little lithium and
beryllium
23
iClicker Question
•
The universe began at a specific point
in time and it has been expanding ever
since.
–
–
A
B
true
false
24
iClicker Question
•
The universe did not have a specific
beginning point in time and it is
currently expanding.
–
–
A
B
true
false
25
iClicker Question
•
Cosmologists believe the only nuclei
that could have formed in the big bang
are isotopes of which elements?
–
–
–
A
B
C
H, Fe, and C
Fe and heavier elements
H, He, Li, Be
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The Evolution of the Universe
27
Some General Characteristics
of an Expanding Universe
• All matter heats when compressed
– Hot big bang
• Freezings
– Changes in universe
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10-43 Second: The Freezing
of All Forces
• Two fundamental forces
– Gravity
– Strong-electroweak force
• Limit of our knowledge of universe
29
10-35 Second: The Freezing of the
Electroweak and Strong Forces
• Three fundamental
forces
• The elimination of
antimatter
– Galaxy is ordinary
matter
– Why?
• Leftover protons
• Inflation
– Short rapid
expansion
• Common temperature
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10-10 Second: The Freezing of the
Weak and Electromagnetic Forces
• Four fundamental forces
• Particle accelerators
– Reproduce from here forward
– Experimental evidence for evolution of
universe
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10-5 Second: The Freezing of
Elementary Particles
• Elementary particles formed
• Prior
– Quarks and leptons
• After
– Hadrons and leptons
• Electrons, protons and neutrons
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Three Minutes:
The Freezing of Nuclei
• Nuclei become stable
• Only nuclei of H, He, Li, Be
• Plasma
33
Before One Million Years:
The Freezing of Atoms
• Formation of Atoms
• Radiation released
– Cosmic microwave background
• Galaxy problem
34
Dark Matter and Ripples
at the Beginning of Time
• Dark Matter
– Measure gravitational
effects
• Hydrogen atoms
• Formation of dark matter
(questions to be answered)
– Before atoms formed?
– Formed clumps?
• Ripples at the beginning of
time
– Collection of luminous matter
35
The End of the Universe
• Open, closed or flat universe
• Current data
– Mass of universe
• Open universe
– Type Ia supernova
• Dark Energy
– 70% of universe’s mass
• Future
– Depends on dark energy
– Big Rip
36
iClicker Question
•
Dramatic changes in the fabric of the
universe are referred to as:
–
–
–
–
A
B
C
D
big bangs
freezings
paradigm shifts
red shifts
37
iClicker Question
•
At what time after the big bang did
nuclei form?
–
–
–
–
A
B
C
D
10-43 seconds
1 second
3 minutes
300,000 years
38
iClicker Question
•
What percentage below is closest to
the percentage of the matter in the
universe which is made of dark
matter?
–
–
–
–
A
B
C
D
0.9
9
90
99
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iClicker Question
•
There may be a new kind of force
acting over vast distance between
galaxies and behaving like a kind of
antigravity that pushes things apart:
–
–
A
B
true
false
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iClicker Question
•
I believe the universe will
–
–
A
B
–
–
–
C
D
E
continue to expand forever
slow its expansion and then
eventually collapse in on itself
come to an end some other way
continue like today, forever
none of the above
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