Kepler’s Laws of Planetary Motion

Objectives

• Describe Kepler’s Laws of Planetary Motion

• Relate Kepler’s Laws to Newton’s Laws

• Prove Kepler’s 3rd law is valid

Just to get an idea of the timeline

• Nicolaus Copernicus (1473-1543)

• Tycho Brahe (1546-1601)

• Galilieo Galilei (1564-1642)

• Johannes Kepler (1571-1630)

• Isaac Newton (1642-1727)

The efforts of many men…• Nicholas Copernicus published his work in 1543

stating the solar system is Sun centered opposing the belief that Earth was the center of our system. (deathbed…)

• Tycho Brahe (1546–1601) studied the planets and stars without a telescope. He used a huge apparatus to record the positions of the heavenly bodies. After many years of study he concluded the Sun and moon orbited Earth while all other planets orbited the Sun.

Johannes Kepler (1571 – 1630)

• Kepler was an assistant to Brahe and inherited Brahe’s work upon his death in 1601. Kepler believed the Sun was our center point and that he could decipher the distance and motion of our planets. Analyzing Brahe’s work along with his own studies painstakingly for nearly 20 years**…Kepler did not give up on his idea…Finally he presented….

Kepler’s Laws of Planetary Motion

• 1st Law states that planets orbit in elliptical paths with the Sun at one focus. (1609)

• Definition of Ellipse…?

• Board illustration

• 2nd Law states that an imaginary line from the Sun to a planet sweeps out equal areas in equal time intervals. (1609)

Kepler’s 3rd Law (1619)• The square of the ratio of the periods of any two

planets revolving around the Sun is equal to the cube of the ratio of their average distances from the Sun.

• In other words, there is a distinct relationship between a planets period and its distance from the Sun.

• Kepler managed to make these discoveries before Newton’s Laws of Motion were formed!

SAY WHAT!?!

• An example of the

My hard work has paid off… You have something

to take notes on!!!You’re welcome.

• Proof

T2 r3

Conclusion…

• What did we learn today?

• How does this relate to what we already know?

• How about the history? What does such a rich and layered story imply? (still not over)

• Problems.