Johannes Kepler and His
Scientific Contributions
By Katelyn Cooper
• Lived from 1571-1630
• German moved to Prague to become Brahe’s
• Brahe told him to watch the orbit of Mars, so
Brahe could continue with his theory on the solar
• He kept him occupied with the orbit of Mars
because Brahe didn’t trust Kepler, he thought
one day, Kepler would eclipse him as the
premier astronomer of his time.
Kepler’s Theory
• Kepler believed in the Copernican System,
which placed the sun directly in the center of the
planets orbits.
• Kepler realized Aristotle was wrong when he
said that the orbits of planets were circular. In
the system Copernican assumed they were
circular also.
• Kepler proved that the theory was not wrong but
the shape of the orbit was, the orbits were
flattened circles, also known as ellipses.
First Law of Planetary Motion
• Kepler’s first law stated that the sun
was not the center of planet’s orbits
but at one focus.
• Which means the sun’s distance is
constantly changing.
Equal Area Law of Planetary Motion
• The line joining the planet to the Sun
sweeps out equal areas in equal times as
the planet travels around the ellipse.
• The planet moves faster when it is closer
to the sun.
• 2 parts: the perihelion and the aphelion
Harmonic Law of Planetary Motion
• The ratio of the squares of the
revolutionary periods for two planets is
equal to the ratio of the cubes of their
semimajor axes.
• Kepler's Third Law implies that the period
for a planet to orbit the Sun increases
rapidly with the radius of its orbit.
• P represents the planet’s period of
• R represents the planets axis’
Interactive Sites
• Kepler's First Law
• Simulation of Orbit
• "Johannes Kepler: the Laws of Planetary
Motion." Johannes Kepler: the Laws of Planetary
Motion. 15 May 2006
• Spaulding, Nancy E. Earth Science. Dallas:
McDougal Littell, 1999. 405-406.
• Porter, Roy, and Marilyn Ogilvie. Dictionary of
Scientists. 3rd ed. Vol. 1. Great Brittain: Helican,
2000. 554-557.

Johannes Kepler and His Scientific Contributions