Cosmology and the Evolution of the Cosmology and the Evolution of the Cosmology and the Evolution of the Cosmology and the Evolution of the Universe Universe Universe Universe Edwin Hubble, 1929: Edwin Hubble, 1929: Edwin Hubble, 1929: Edwin Hubble, 1929: -almost all galaxies have a redshift -moving away from us -greater distance greater redshift Implications of the Hubble Law: Implications of the Hubble Law: Implications of the Hubble Law: Implications of the Hubble Law: - Universe is changing changing changing changing (getting bigger!) - it is not static, unchanging - Universe had a beginning beginning beginning beginning !! - could not have been expanding forever HUBBLE LAW: HUBBLE LAW: HUBBLE LAW: HUBBLE LAW: v = H v = H v = H v = H o r v = velocity (speed); r = distance Rate of expansion: H o = Hubble constant (slope of line) The Hubble Constant tells us: - Size of observable universe largest redshift = largest distance - Age of universe how long ago everything was together - Fate of universe what will happen in future Most accurate measurements (2014): H o = = = = 70.4 70.4 70.4 70.4 to to to to 74.3 74.3 74.3 74.3 km/s per M km/s per M km/s per M km/s per Mpc pc pc pc Age = 13. Age = 13. Age = 13. Age = 13.25 25 25 25 to 13.9 to 13.9 to 13.9 to 13.98 billion years billion years billion years billion years The Big Bang Model The Big Bang Model The Big Bang Model The Big Bang Model Universe began from a single point - that was extremely dense and hot Cosmic Singularity - "Explosion" of matter and energy (and space and time!) -today, still expanding - properties of universe change with time - had different conditions in the past - will have diff. conditions in future - ultimate fate is unknown The Early Universe: Initially was very HOT! - Hot enough for Hydrogen fusion everywhere in space! - explains why 25% of universe is Helium Basic Principles of Big Bang Model 1. Universe cools as it expands: Time Temperature 0.01 s 100 billion Kelvin 180 s 1 billion Kelvin 400,000 yrs 3000 Kelvin
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Cosmology and the Evolution of theCosmology and the Evolution of theCosmology and the Evolution of theCosmology and the Evolution of the UniverseUniverseUniverseUniverse
Edwin Hubble, 1929:Edwin Hubble, 1929:Edwin Hubble, 1929:Edwin Hubble, 1929: -almost all galaxies have a redshift
-moving away from us
-greater distance � greater redshift
Implications of the Hubble Law:Implications of the Hubble Law:Implications of the Hubble Law:Implications of the Hubble Law:
- Universe is changingchangingchangingchanging (getting bigger!) - it is not static, unchanging
- Universe had a beginningbeginningbeginningbeginning !! - could not have been expanding forever
HUBBLE LAW:HUBBLE LAW:HUBBLE LAW:HUBBLE LAW: v = Hv = Hv = Hv = Hoooo rrrr v = velocity (speed); r = distance
Rate of expansion: Ho= Hubble constant (slope of line)
The Hubble Constant tells us: - Size of observable universe
largest redshift = largest distance
- Age of universe how long ago everything was together
- Fate of universe what will happen in future
Most accurate measurements (2014):
HHHHoooo = = = = 70.470.470.470.4 to to to to 74.374.374.374.3 km/s per Mkm/s per Mkm/s per Mkm/s per Mpcpcpcpc
Age = 13.Age = 13.Age = 13.Age = 13.25252525 to 13.9to 13.9to 13.9to 13.98888 billion yearsbillion yearsbillion yearsbillion years
The Big Bang ModelThe Big Bang ModelThe Big Bang ModelThe Big Bang Model
Universe began from a single point - that was extremely dense and hot
� Cosmic Singularity
- "Explosion" of matter and energy (and space and time!)
-today, still expanding
- properties of universe change with time - had different conditions in the past - will have diff. conditions in future
- ultimate fate is unknown The Early Universe:
Initially was very HOT! - Hot enough for Hydrogen fusion
everywhere in space! - explains why 25% of universe is
Helium Basic Principles of Big Bang Model
1. Universe cools as it expands:
Time
Temperature
0.01 s
100 billion Kelvin
180 s
1 billion Kelvin
400,000 yrs
3000 Kelvin
2. High energy radiation (photons) create matter
� E = m cE = m cE = m cE = m c2222
electron
Gamma Rays
positron
3. Energy of radiation (photons) depends on temperature of universe
- As universe expands and cools - radiation loses energy - universe is a blackbody
PREDICTION:PREDICTION:PREDICTION:PREDICTION: According to Big Bang Model:
What is temperature of universe TODAY? Prediction: 3 Kelvin3 Kelvin3 Kelvin3 Kelvin (1964, Peebles and Dicke, Princeton Univ.)
1964, A. Penzias and R. Wilson (Bell Labs)
-built antenna for satellite communications
-detected "noise" in all directions -background noise corresponds to temperature of 3 Kelvin!
���� Energy leftover from theEnergy leftover from theEnergy leftover from theEnergy leftover from the
BIG BIG BIG BIG BANGBANGBANGBANG !!!
““““Cosmic Microwave BackgroundCosmic Microwave BackgroundCosmic Microwave BackgroundCosmic Microwave Background”””” (CMB)(CMB)(CMB)(CMB)
1989, satellite COBE - accurate measurements of Cosmic Microwave Background
- Temperature of Universe: T = 2.725 +/T = 2.725 +/T = 2.725 +/T = 2.725 +/---- 0.002 K0.002 K0.002 K0.002 K
Expansion of the Universe:Expansion of the Universe:Expansion of the Universe:Expansion of the Universe:
- the space between objects is expanding
- objects are not moving through space.
CosmoCosmoCosmoCosmological Principle:logical Principle:logical Principle:logical Principle: - there is no center, no edge - every location appears to be at
center
- same at every location (large scales) “Homogeneous”
- same appearance in every direction “Isotropic”
Clusters, Superclusters, Voids - origins should be seen in the CMB - 1992, temp fluctuations of 0.0002 K - seeds of large scale structure
Surprising Discovery in 1998:
- rate of expansion is increasing!
- previously thought that gravity would slow expansion over time
- what can overcome affects of gravity? - repulsive, anti-gravity force
---- ““““Dark EnergyDark EnergyDark EnergyDark Energy””””
Fate of the Universe:Fate of the Universe:Fate of the Universe:Fate of the Universe: Three Three Three Three Possible FatesPossible FatesPossible FatesPossible Fates:
- based on overall density of universe - need to know total mass - need to know overall size (Ho)
Closed Universe: - expansion will eventually stop - gravity will cause universe to collapse
- Universe will end in "Big Crunch""Big Crunch""Big Crunch""Big Crunch" - maybe start again (?)
Overall geometric “shape” of universe is spherical
Flat universe: - expands forever, always slowing down - not enough gravity to start collapse - Universe will end in ““““ColdColdColdCold Death”Death”Death”Death” - all forms of energy becomes evenly distributed in space. - everywhere in universe is same temperature -close to absolute zero
Overall “shape” of universe is flat.
- Flat universe is predicted by current theories.
Open Universe:
- expands forever, possibly going faster and faster
- dark energy overwhelms gravity
- Universe will end in “Big Rip”“Big Rip”“Big Rip”“Big Rip” - dark energy overwhelms all other forces. - expansion will accelerate so much, all matter will get ripped apart Overall “shape” of universe is hyperbolic.
TIMETIMETIMETIME EVENTEVENTEVENTEVENT 0 – 10-43 seconds
The Planck Time:The Planck Time:The Planck Time:The Planck Time: Nothing is known during this time.
????
10-35 – 10-32 seconds
InflationInflationInflationInflation:::: Universe goes through period of enormous expansion, grows by factor of 1043!!
Radiation Dominated Universe
(Primordial Fireball)
10-8 – 10 seconds
Production of Production of Production of Production of MatterMatterMatterMatter: quarks and electrons created from extremely hot photons
10 – 300 seconds
Nucleosynthesis EraNucleosynthesis EraNucleosynthesis EraNucleosynthesis Era: 2H and 4He created by fusion reactions throughout the universe
400,000 yrs Era of RecombinationEra of RecombinationEra of RecombinationEra of Recombination: Electrons combine with nuclei to form atoms; (T = 3000 K), space is now transparent
Matter Dominated Universe
(Transparent)
1 – 2 billion years
Formation of GalaxiesFormation of GalaxiesFormation of GalaxiesFormation of Galaxies: Young galaxies seen as quasars
9 – 10 billion years
FormaFormaFormaFormation of Solar Systemtion of Solar Systemtion of Solar Systemtion of Solar System: Sun and planets form within the Galaxy (4.6 billion years ago)
Today (14 billion years)
Universe still expanding; Average temperature T = 2.725 K
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