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13 Cards in this Set
- Front
- Back
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Scientific method
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form hypothesis, based on observations, experiments and existing laws-> test hypothesis, make predictions->hypothesis gains stregnth, revised
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Parallax
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apparent shift of a nearby object, relative to background objects, due to changing position of observer
from earth, stars appear to shift relataive to background stars farther away=smaler parallactic shift |
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retrograde motion
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planets appear to move eastward relative to stars, every once in a while reverse direction and move westward
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Aristotle
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physical laws govern universe
earth is @ center of finite universe, earth is imperfect proved earth was spherical |
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Ptolemy
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models of planetary motions based on concept of epicycles, to explain retrograde motion
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Epicycles
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planets orbit on circles, which are tied to larger circles
mercury & venus tied to Earth-sun line |
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Copernicus
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Motion of planets around sun (heliocentric)
Retrograde motion occurs when inner planet passes outer planet Uniform circular motion (epicycles to explain small variations in motion) |
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Brahe
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Model w/ planets orbiting the sun, but the sun orbiting Earth
designed intruments discovered new star (supernova) |
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Kepler
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adopted heliocentric view
3 laws of planetary motion using Brahe's observations |
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Kepler's first law
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Each planet moves in an elliptic orbit with the sun at 1 focus of the ellipse
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Keplers second law
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Line from sun to any planet sweeps out equal areas of space in equal time intervals
Move faster when closer to sun |
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Keplers third law
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the squares of the planets are proportional to the cubes of their average distances from the Sun
P2=a3 P=time a=distance planets closer to sun: a is smaller, so P is smaller planets further from sun: a is larger, so P is larger |
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Newtons law of universal gravitation
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gravity causes acceleration, which causes gravitation force
gravity keeps planets orbit around sun, moon around earth |
