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.
