Transcript Our SOlar System

Our Solar System
Models of the Solar System
Objectives:
Compare the models of the universe
developed by Ptolemy & Copernicus
Summarize Kepler’s 3 laws of
planetary motion
Aristotle (384-322 B.C.)
• Promoted a GEOCENTRIC model of the
universe
• The universe revolves around ME
• But doesn’t explain the RETROGRADE
motion
Retrograde Motion
Ptolemy (87-150 A.D.)
epicycles
Copernicus (1500s A.D.)
Proposed the HELIOCENTRIC
model of the universe.
The arguments against the
Heliocentric Model
1) If the Earth actually spun on an axis -- as required in a
heliocentric system to explain the diurnal motion
(day/night)of the sky-- why didn't objects fly off the
spinning Earth?
2) If the Earth was in motion around the
sun, why didn't it leave behind the birds
flying in the air?
3) If the Earth were actually on an orbit around the
sun, why wasn't a parallax effect observed?
That is, as illustrated in the adjacent figure, stars
should appear to change their position with the
respect to the other background stars as the Earth
moved about its orbit, because of viewing them
from a different perspective
Copernicus
Copernicus put the SUN in the middle of
our solar system=> heliocentric model
Galileo agreed with him & invented the first
TELESCOPE just to prove that the Sun was in
the center of our solar system.
Kepler (1571-1630 AD)
• First to explain the
principles of how a
telescope works
• First to suggest that
the Sun rotates about
its axis
Formulated the other’s ideas into
Mathematical formulas  creating Kepler’s
3 laws of Planetary Motion
The First Law:
Planets move in ellipses with the
Sun at one focus.
APHELION
PERIHELION
Astronomical Unit = 149 598 000 km
The 2nd Law: A planet speeds up as it
gets closer to the sun. So that the area of
space covered is the same whether the
earth is close to the sun or further away.
The 3rd Law: the time it takes to orbit
the sun is directly related to its distance
from the sun.
Sir Issac Newton (1642-1727) explained
that the planets move in ellipses around the
Sun because of GRAVITY
Assignment:
Kepler’s 3 Laws of Planetary
Motion Handout
Comets follow the Kuiper Belt. The Kuiper Belt
follows past Neptune's orbit to the other side of the
Sun. There is an "Oort" cloud that's a spherical
region of Comets on the Kuiper Belt.
What do you think this ghostly
image is?