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

BIG BANG 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

BIG BANG Looks the same to

all observers Distance and speed

related Expansion

STEADY-STATE Looks the same to

all observers New matter is

created and added to universe

Expansion