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Lecture 1

Lecture 1.docx

Earth and Environmental Sciences
Course Code
Jie Li

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Lecture 1
Study of the solar system: curiosity, intellectual advance, practical gains
We use our study of Earth through chemistry, physics and geology to study
planets and moons  comparative planetology
Science: “knowledge gained through experience”
Isaac Newton-
oIf I have seen further it is b/c I have been standing on the shoulders of
We are fortunate to do this from our ancestors discoveries and
History of planetary studies:
oAncient/common knowledge:
Sun and moon are ‘close objects
Planets (from Greek ‘wanderer’):
Mercury- messenger of the gods, very close to the sun
Venus- goddess of love, close to the sun and really bright,
very harsh planet can’t survive there at all
Mars- god of war, relatively small, other side relative to the
Jupiter- king of the gods, has retrograde
Saturn- chromos, father of Jupiter, can see with naked eye
Basic (& naked eye) observations
Stars are fixed w/ respect to each other
All planets move through the ecliptic in the zodiac
oSun and moon also move through the ecliptic
Mercury and Venus stay close to the sun
Mars Jupiter and Saturn show retrograde motion (go
forward stop go backwards and then go forwards again),
moving more slowly b/c of retrograde, Mars goes around
every 2 yrs, Jupiter and Saturn ~ 1 yr
Ecliptic plain- all of the orbits of the planets are more or less
confined to
While they do spin their location is fixed in relation to each other
Geocentric model: Epicycle would explain retrograde cycle- they
do their own circle while traveling on bigger circle, Earth is center
of universe – Ptolemy
Heliocentric model
oCopernican system- Heliocentric model
Mercury and Venus stay ‘naturally close
Retrograde motion is only apparent- its not actually real, just from
Earth’s point of view does it appear curved and back and forth
when it is really a normal orbit
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