AST-A 100 Study Guide - Fall 2018, Comprehensive Midterm Notes - Solar System, Orbit, Galileo Galilei
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AST-A 100
MIDTERM EXAM
STUDY GUIDE
Fall 2018
Lecture 1—Class notes—8/22
− The plane of the galaxy is visible.
− Milky way is relatively flat compared to the width.
− “tars su ad the oo rise i the east ad set i the est’
o Appears as if the dome of the sky is moving
o Stars appear to be at the same distance
− Overhead dome is referred to as the celestial sphere
− Zenith: the top of the dome, the point directly overhead.
− Horizon: where the dome appears to meet the earth.
− North star: Polaris, nearest to the northern celestial pole.
− If you were at the north pole, your zenith would be pointing to the North star.
− Constellations divide the sky into regions
o Arbitrary patterns that appear next to each other—all perspective
− Zodiac contellations are the important because they lie along the ecliptic
o Ecliptic: path the sun takes through the sky
o Sun goes through the constellation about once a month
o Astrology assigned meaning to the Zodiac constellations
− Planets move along the ecliptic, just like the zodiac constellations
o Plaet eas aderer eause ulike stars, their positions are not fixed.
− Ancient astronomy- a geocentric view
o The earth was in the center of the solar system
o Held for a long time because it could describe everything that happened in the sky
o Ptolemy (~100 CE)—a natural philosopher who proposed the geocentric model
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▪ This model seemed to accurately predict the movement of the planets and the
sun
− Astronomy is a science
o Ongoing process
o Experiments are reproduced and checked
o Results are widely shared and evaluated
o Value of ideas based on evidence (not authority)
o Theories may be discarded where new evidence is found
o Great example is transition for geocentric model to heliocentric model
− New observations of apparent retrograde motion of Mars was hard to explain within the
geocentric model
o Retrograde = backwards
o Added epicycles to Geocentric model,
▪ Epicycle is a mini orbit.
− The Heliocentric model
o Natural philosophers had proposed the heliocentric model as early as the 3rd century BC
o A mathematical model was first created by Copernicus (~1500s) to explain the night sky
o Best explains apparent retrograde motion without epicycles
o This also explains why we only see retrograde motion in the outer planets
− Modern Astronomy
− Galileo
o Invented the telescope in the early 1600s
o Carried out first observations of moons of distant planets
o Discovered Moons of Jupiter
find more resources at oneclass.com
find more resources at oneclass.com