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Early people looked at the stars and wondered…. The ancient Greeks studied the movement of the stars and observed patterns. They concluded the patterns of most of the stars do not change, except…. 5 points of light that seem to wander among the stars. - PowerPoint PPT Presentation
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Early people looked at the
stars and wondered…
The ancient Greeks studied the movement of the stars and
observed patterns.
They concluded the patterns of
most of the stars do not
change, except…
5 points of light that seem to
wander among the stars.
The Greeks named them
PLANETS, which means
wandering stars.
The Planets were named after the 5
Roman Gods, Mercury,
Venus, Mars, Jupiter and
Saturn
Mercury, Venus, Mars, Jupiter and Saturn were
the only planets that
could be seen at that time.
The Greeks thought the Earth
was the center of a celestial
sphere with all stars and planets
revolving around the Earth.
This Earth centered theory is called the geocentric system.
Observations of the planets did not fit the simplest version of the geocentric system.
.
Early astronomers tried to create a model that would fit their observations
In A.D. 140 Ptolemy suggested a variation
of the geocentric model that explained
why the planets move at different speeds. Bodies
revolved in small circles as they orbited
Earth
For 1,400 years people believed Ptolemy was correct.
In the early 1500’s the Polish astronomer
Nicolaus Copernicus thought the sun was the center of the system of
planets.
His sun-centered system was called the heliocentric system.
Helios is Greek for sun.
But people still believed Ptolemy’s geocentric system.
100 year’s later Galileo agreed with
Copernicus’ heliocentric system.
In 1609 Galileo perfected the
telescope which lead him to
discoveries that supported the
heliocentric system.
Galileo discovered the 4 moons of Jupiter.
He thought if moons revolve around Jupiter then all things do not revolve
around the Earth.
He discovered the phases of Venus. This requires the sun to be the center
of the system of planets.
Galileo’s discoveries were not accepted by those that still believed in the geocentric system. The geocentric view had the support of the church which was in power at that time.
This illustration was copied from Nick Strobel's Astronomy Notes. Go to his site at www.astronomynotes.com for the updated and corrected version.
Galileo was put on trial for his beliefs in 1633. He remained under house arrest until he died in 1642.
In the late 1500’s a Danish
astronomer, Tyco Brahe, carefully observed and recorded the
positions of the planets for 20
years.
• He believed in a modified version of geo-centric model.
• Every planet EXCEPT EARTH revolved around the sun.
• The sun with all the planets REVOLVED around Earth.
Brahe’s meticulous records of planetary motion were passed on
and interpreted by a German mathematician in the 1600’s.
Johannes Kepler used
Brahe’s data to figure out the shape of the
planets’ orbits.
Kepler concluded the planets orbit the Sun in an ellipse.