1. Theories notes
steady-state, inflationary, open universe, closed universe, Geocentric, Heliocentric theories

2. Cosmology: The study of the universe, its current nature, its origin and its evolution.
Astronomy: Study of everything in space including space itself.

3. Steady-state Theory
Universe had NO beginning and does not change with time.
New matter must be continually created and added to the universe as it expands.

4. Big Bang theory & the possible fate of the Universe.
According to the Big Bang theory, the outward momentum of the expanding universe is opposed by the inward force of gravity due to the matter in the universe.
The force of gravity acts to slow expansion.
What ultimately happens depends on whether momentum or gravity is stronger.

5. Three possible outcomes
These three outcomes are based on the premise that the rate of expansion has decreased since the beginning of the universe.
Open universe
Continue to expand forever (cold & dark)
Closed Universe
Contract & collapse back onto itself
Flat Universe
Expansion will slow to a halt but never contract.

6. Inflationary Model Theory
Version of the Big Bang theory that combines the increasing rate of expansion, the observed density of the universe and dark matter.
Universe expanded very rapidly during the small fraction of a second after the Big Bang.
It has settled into a more gradual expansion.

7. Geocentric Theory Geo = Earth Earth is at the center of the Universe
2 observations to support
Stars, sun and planets appear to revolve around the Earth each day
Perception that the Earth is solid, stable and not moving.

8. Heliocentric Theory Helio = Sun
Sun is stationary and at the center of the Universe

9. Galileo Galileo was a professor of astronomy
Galileo supported the Heliocentric theory which got him into trouble with the Catholic Church.
Convicted of heresy (1663)
Constructed his own telescope
Discovered the sunspots
Discovered the 4 brightest moons of Jupiter
Moon not smooth but covered with mountains and craters.

10. Contrast: Big Bang and Steady State
Began as a compressed hot dense state
Farther away a galaxy is the faster it is moving away
Expansion rate is speeding up
Cosmic background radiation
STEADY STATE
No beginning – always the same
Does not change with time
No prediction or way to explain cosmic background radiation

11. Big Bang vs. Steady-State – the same for both
Looks the same to all observers
New matter is created and added to universe
Expansion
BIG BANG
Looks the same to all observers
Distance and speed related
Expansion
Both Big bang and steady state – expansion and that it looks the same to all observers
Steady state – new matter is created and added to universe
Big bang – expansion and matter is going along for the ride – the distance and speed of the galaxy are related