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

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

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.

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.

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.

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.

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.

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

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.

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

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