### TOPIC 3 Movements of the Planets

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TOPIC 3
Movements of the
Planets
2 Theories of Solar System
4.6 Billion Years old
• Geocentric
–“EarthCentered”
–Claudius
Ptolemy
–90 A.D.
• Heliocentric
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–“SunCentered”
–Copernicus
–1543
Claudius Ptolemy
Nicholas Copernicus
•1473--1543
GEOCENTRIC
HELIOCENTRIC
relative brightness and positions of planets
Slide 8 of 35
TYCO BRAHE
• Danish Astronomer
• 1546------1601
• Built first observatory in
history(Europe)
• Collected data on positions of the
planets(Studied Mercury/Venus)
JOHANNES KEPLER
• 1571------1630
• Brahe’s student---supposedly murdered
Brahe so that he could take over his
laws?
• “Created” 3 laws of planetary motion:
– Law of Orbit(1st)
– Law of Equal areas(2nd)
– Law of Harmonic Motion(3rd)
Kepler website!
• Johannes Kepler
Astronomers
KEPLER’S FIRST LAW
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• “ALL PLANETS REVOLVE AROUND THE
SUN IN ORBITS SHAPED LIKE AN
ELLIPSE WITH THE SUN LOCATED AT
ONE OF THE FOCUS POINTS(FOCI)”
FOCUS POINTS
Nothing over
here!
*
SUN
*
PATH
EARTH
ELLIPSE
Definitions:
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• ORBIT: the path of a planet around
the Sun
• REVOLVE: planet’s movement around
the Sun
• ELLIPSE: a flattened circle with 2 focus
points (foci)
• Focus Points: FIXED points within an
ellipse
*
ELLIPSE!
CIRCLE: special
ellipse with one
focus point on top
of the other!
*
*
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ECCENTRICITY
»How far from a
perfect circle is an
ellipse represented by
a number between
0(circle) and 1(line).
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*
* *
*
*
EQUATION(ESRT)
e= distance between focus points(foci)
Length of major axis(“diameter”)
OR
e= d
L
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*
d
L
*
“e” values are found with a ruler and are
written out three numbers past the
decimal point(thousandths place!)
See Solar System Data in ESRT(Pg 15)
Almost
circular!
NO
UNITS!!!!!
Farthest from
a circle!
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