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UA - ay 101 - Class Notes - Week 5

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UA - ay 101 - Class Notes - Week 5

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background image History  Geocentric to Heliocentric o  Geocentric view of the Universe means the Earth is the center
o  Heliocentric means the Sun is the center
 Astronomers o  Aristotle    Geocentrist    “perfect”   shapes   and   motions   in   celestial   objects;   he
believed   everything   in   the   sky   was   a   perfect   circle   and
   Believed the earth and sky were separate    Believed   stars,   moon,   planets,   etc.   were   on   concentric
spheric planes of “aether”
   Believed matter naturally rested    Mixed observation and theory o  Artistarchus    Heliocentrist    (310-230 BC)    Believed sun was bigger than the Earth and that it would
make   sense   for   the   smaller   object   (Earth)   to   orbit   the
bigger object (sun)
 Realized   sun   was   farther   away   b/c   of   the   moon
phases, so since sun and moon seem the same size,
the sun must be huge
   Not accepted in his time o  Eratosthenes    (273-195 BC)    Measured Earth’s radius to a 2% error    Determined the difference of the angle of the sun in two
different   locations   and   used   it   to   create   a   proportion   to
figure out the radius
o  Ptolemy    (85-165 AD    Geocentrist    Added epicycles to orbits to account for retrograde motion    Gave Venus phases “new and cresent” o  Copernicus    (1473-1543)    Heliocentrist    Clergyman    Still   believed   in   perfect   circles,   but   made   the   sun   the
center to simplify the models of the universe and because
it was aesthetically pleasing
background image    Refused to publish his work until after he died because he
did not want to be ridiculed
o  Tycho Brahe    (1546-1601)    Geocentric    Very rich, owned much land, close with king of Denmark    Built massive observatory    Lost half of his nose in a duel over a math problem, had an
alcoholic pet moose
   Had   to   go   to   the   bathroom   while   visiting   the   king   but
wanted to be polite, so he held it and his bladder burst and
he got an infection and died
   Discovered a supernova    Collected massive amounts of data o  Johannes Kepler    (1571-1630)    Heliocentrist    Accurate planetary orbital laws    Assisted Brahe    Tried using perfect circles, but when it failed, finally went to
ellipses; some planets were more elliptical than others
   3 orbital laws  Planets are in elliptical orbits around the Sun with the
Sun at one focus of ellipse; sun was in the small side
of more elliptical orbits, not directly at center
 Sun-planet line sweeps out equal areas in equal time;
orbital speed not uniform; faster when closer to sun
due to gravity
o  Equal spaces of time within an orbit; distance traveled   when   made   into   a   triangle   with   the
sun, area the same in all triangles
 Period is proportional to distance 3 ; so p 2 =a 3 o  Mass,   size,   etc.   does   not   affect   rotational velocity    His work was a turning point in astronomy    No physics behind his laws, just mathematical fits (didn’t
understand gravity)
o  Galileo Galilei    (1564-1642)    Physical laws  Law of Inertia: objects at rest tend to stay at rest, or
objects in “uniform motion” tended to stay in motion

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School: University of Alabama - Tuscaloosa
Department: OTHER
Course: Intro to Astronomy
Professor: Ronald Buta
Term: Spring 2017
Tags: astronomy, Astronomy 101, intro to astronomy, history, newton's laws, and Astronomers
Name: AY 101 Week 5
Description: These notes address the history of astronomy, such as famous astronomers and their accomplishments. This also covers a few laws that such astronomers created, like Newton's laws of motion.
Uploaded: 09/17/2017
4 Pages 38 Views 30 Unlocks
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