MODELS OF THE SOLAR SYSTEMChap. 29, Sect. 1•OBJECTIVES: SWBAT…•1. Compare the models of the universe developed by Ptolemy and Copernicus.

•2. Summarize Kepler’s 3 laws of planetary motion.

EARLY VIEWS OF SOLAR SYSTEM•1. Earth is center: geocentric theory. (Aristotle)

•2. Earth is flat and motionless.

GEOCENTRIC THEORY

EARLY VIEWS OF SOLAR SYSTEM•3. Greeks: planets move in reverse direction (retrograde motion).

RETROGRADE MOTION

CLAUDIUS PTOLEMY

EARLY VIEWS OF SOLAR SYSTEM•4. Ptolemy: “planet has 2 motions”:

• A. one is around the Earth.

• B. one is on a smaller circle (epicycle).

EARLY VIEWS OF SOLAR SYSTEM• C. explains retrograde motion.

EPICYCLES

NICHOLAS COPERNICUS

RISE OF MODERN ASTRONOMY•1. Copernicus:•A. “sun is the center”•B. “planets move at a different speed and direction, which explains retrograde motion.

COPERNICAN VIEW

TYCHO BRAHE

RISE OF MODERN ASTRONOMY•2. Tycho Brahe:•A. uses 1st pretelescopic instruments.

•B. charts over 700 stars in precise positions.

JOHANNES KEPLER

RISE OF MODERN ASTRONOMY•3. Johannes Kepler:•A. analyzes Brahe’s data.

•B. comes up with 3 Laws of Planetary Motion.

RISE OF MODERN ASTRONOMY•LAW 1: “The motion of a planet around the sun is an ellipse (oval-shaped).”

•A. sun occupies 1 foci.•B. perihelion and aphelion.

LAW OF ELLIPSES

RISE OF MODERN ASTRONOMY•LAW 2 (Equal Areas): “A line drawn from a planet to the sun sweeps out equal areas in equal amounts of time.”

LAW OF EQUAL AREAS

RISE OF MODERN ASTRONOMY•LAW 3 ( Law of Harmony): “The cube of the ave. dist. Of a planet from the sun is always proportional to the square of the period.”

•K x r3 = p2

NEWTON’S LAWS•Said that a moving body will

change its motion only if an outside force causes it to do so.

•Inertia: the tendency of a moving body to move in a straight line at a constant speed until an outside force is applied.