1. Kepler’s Laws
Yep, all three!

2. Greek Observations
Early Greeks were the first to truly notice the
planets in our solar system. In fact, planets is
Greek for wanderers.
Greeks believed that the earth was spinning
within a larger dome called the celestial sphere.
Greeks believed in a geocentric model, where
the earth is at the center.

3. Greek astronomer: Ptolemy
Ptolemy believed, as other Greeks did, that
Earth was at the center; however, he
hypothesized that the planets were moving on
flat planes.
The Geocentric model was accepted as truth for
nearly 1,500 years!

4. Copernican Revolution!
Polish Astronomy, Nicolaus Copernicus helped
to develop the heliocentric model, where the
sun is at the center rather than the Earth.
Many people had trouble accepting this model,
even into the 1600’s!

5. Good old Galileo Galilei
Because Galileo use the newly invented
telescope, he was able to discover more than his
predecessors.
Galileo discovered 4 moons orbiting Jupiter
(known as the Galilean Moons)
Galileo also helped to support and develop the
heliocentric model.

6. Tycho Brahe & Johannes Kepler
Late 1500’s, Danish astronomer Tycho Brahe and
his assistant Johannes Kepler worked over a 20
year period collecting data through observations
of the night’s sky.
After Brahe died in 1601, Kepler continued to
analyze and study the data- from that came his
3 laws.

7. Kepler’s 1st Law
Through his observations of Mars’s orbit, he
discovered his first law:
The Orbital path of the planets are NOT
circular- they are an ellipse (oval shape).
This discovery disproved the long help belief of
circular orbits.

8. Kepler’s 2nd Law
Kepler then discovered that the speed of a
given planet changes as it revolves around the
sun.
The closer a planet is to the sun, the faster it
moves. The farther away it is, the slower it
moves.

9. Kepler’s 3rd Law
Kepler also discovered that the time it takes a
planet to orbit the sun and it’s average
distance from the sun are directly related.
The closer a planet is to the sun, the faster it’s
revolution. The farther a planet is, the slower
the revolution.

10. Kepler’s 3rd Law
Kepler also discovered that the time it takes a
planet to orbit the sun and it’s average
distance from the sun are directly related.
The closer a planet is to the sun, the faster it’s
revolution. The farther a planet is, the slower
the revolution.