Introduction to Cosmology. Cosmology. Scientific study of the origin and evolution of the universe “kosmos” – Greek for “order” Based on laws of physics, incorporates chemistry, mathematics, and astronomy. Foundations of modern cosmology.
1) General Theory of Relativity (A. Einstein 1915) – describes gravity in terms of the warping of space-time by the presence of mass and energy.
Matter in the universe is distributed evenly in all places and in all directions (homogeneous and isotopic), IF YOU LOOK AT LARGE ENOUGH SCALES (about 100 Mpc).
Universe began in small, hot, dense state which has expanded and cooled over time.
His theory named “Big Bang” as an insult by Fred Hoyle.
Initial arguments against the big bang theory included a disbelief that the laws of physics could possibly be pushed back to the origin of the universe.
There was also an antireligious backlash against the theory, which reportedly was part of the motivation for the rival steady state model.
1) Observed expansion of the universe. Slope = H, but is difficult to determine (uncertainties in velocity and distance) HST Key Project
Predicts percentage of light isotopes relative to hydrogen. Observed composition matches theory with great precision (but restricts amount of normal or baryonic matter that can exist relative to light).
“We are star-stuff”
– Carl Sagan
Predicted by George Gamow in 1948, accidentally discovered by Penzias and Wilson in 1965 (1978 Nobel Prize).
Matches a blackbody of T = 2.7 K (and is very isotropic!)
Ω = ρ / ρcritical
= 1 (flat)
< 1 (open)
0.02 < Ω < 2
In 1981, particle physicist Alan Guth sought a solution for the magnetic monopole problem and ended up revolutionizing cosmology!
All agree with @ 13-14 billion years
The expansion is not slowing down, but is accelerating!
Presence of something like Einstein’s cosmological constant (called “dark energy”)
ΛCDM: accelerating, Ω = 1 universe with @ 70% dark energy and @ 25% cold dark matter and @5% “normal” matter
So far results are consistent with inflation as well.
- Andreas Albrecht (1994)