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Lecture 5

ASTR 105 Lecture Notes - Lecture 5: Geocentric Model, Paradigm ShiftExam


Department
Astronomy
Course Code
ASTR 105
Professor
David Bush
Lecture
5

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Lab AST 105 Lecture Notes 5:
Which 7 objects did ancient people observe moving in the sky?
The sun, the moon, Mercury, Venus, Mars, Jupiter, and Saturn
When you place a stick on the ground at noon, what direction would its shadow point?
North
What are cardinal directions?
North, South, East, and West.
Which ancient civilization used a base-12 numbering system?
The Sumerians. This might make more sense than our current base-10 system because
12 is divisible by more numbers than 10 is.
What was Claudius Ptolemy's contribution to astronomy?
He developed the first model of our solar system, known as the Ptolemeic Model. This
was a geocentric model that explained retrograde motion of the planets by stating that
they are moving in circles while they are orbiting Earth.
Who was Eratosthenes?
A Greek astronomer who first calculated the size of Earth.
What is retrograde motion?
When planets in the night sky appear to move backwards for a short period. The Greeks
explained this by saying that the planets were moving in circles while they orbited Earth.
This is actually caused by Earth's orbit passing the planet's orbit as they both orbit the
sun.
What is a paradigm shift?
A fundamental change in the way science views natural phenomena. A paradigm shift
occurred when Copernicus suggested the heliocentric model of our solar system, rather
than the geocentric model.
What contribution did Copernicus make to astronomy?
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