Physics 24 B. Sadoulet/A.H. Jaffe 31 August 2000
The Big Bang
The universe is expanding now, and was denser & hotter in the past
The three pillars of the big bang
Cosmological expansion (1930s)
The Cosmic Microwave Background Radiation (60s)
The abundances of light elements (40s−70s)
The important numbers
The open questions
Physics 24 B. Sadoulet/A.H. Jaffe 31 August 2000
The History of Cosmology
Cosmology − study of the history and evolution of the Universe
(kosmos, order, universe + logia, speech, word, reason)
16th C. − Copernicus/Galileo − the sun vs. the earth at the center?
17th − 20th C. − Newton, Kant, Laplace, Herschel
What are the nebulae? “Island Universes”/Galaxies
1920s: The Shapley/Curtis debate
20th C. − Einstein, Hubble − Steady State vs. Big Bang
Theory: General Relativity(Freedman, Robertson, Walker, LeMaitre)
Observation: Expansion
Finally resolved in favor of the Big Bang only in 1950s−1970s
Physics 24 B. Sadoulet/A.H. Jaffe 31 August 2000
The Three Pillars of the Big Bang
Cosmological expansion
All galaxies are moving away from one another
No center, no edge!
The Cosmic Microwave Background Radiation
Light (photons) from the hot (3000K!) early universe, cooler now (3K)
Picture of the universe at early times
The abundances of light elements
Hot enough for fusion!
4 Hydrogen → 1 Helium and beyond
(Lithium, Deuterium...)
Physics 24 B. Sadoulet/A.H. Jaffe 31 August 2000
The Parameters of the Big Bang Theory
H0, Hubble’s constant:
How fast is the universe expanding?
Ω: What are the components of the universe?What is the geometry of the universe?
Normal matter: ~5%
Dark Matter: ~25% what is it????
“Dark Energy”/“Vacuum Energy”: ~70%
Accelerating universe???
t0: What is the age of the Universe?
(actually, determined by the answers above!)
Physics 24 B. Sadoulet/A.H. Jaffe 31 August 2000
Open Big Bang Questions
What are those parameters in detail?
Why is the universe flat?
Why are there galaxies? What formed the initial perturbations that grew into the ones we see today? How did they grow?
What is the dark matter?
Why is there more matter than antimatter?
Why is there anything at all?
Physics 24 B. Sadoulet/A.H. Jaffe 31 August 2000
Cosmic Microwave Background
Boomerang + Maxima: The universe is spatially flat!