The document discusses the history of models of the solar system from ancient Greek astronomers to Johannes Kepler. It describes how Greeks originally believed in a geocentric model with the Earth at the center, which was later supported by Ptolemy. Copernicus then developed the heliocentric model of the sun at the center. Galileo's observations of Jupiter's moons and use of the telescope supported this model. Tycho Brahe and Kepler collected extensive observational data, allowing Kepler to develop his three laws: planets orbit in ellipses, their speed changes as they revolve with closer planets moving faster, and their orbital period relates to their average distance from the sun.

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. Ptolemy (Greek astronomer)
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. Copernicus’s 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.