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Unformatted text preview: Modern Cosmology (1 st Mid-Term) 01/04- Mon Cosmos- from the Greek word for the order of the universe. It is, in a way, the opposite of chaos. It implies the deep interconnectedness of all things. It conveys awe for the intricate and subtle way in which the universe is put together. Karl Popper- Science progresses only by falsifiability • Scientists must make bold hypotheses that can be ruthlessly tested to see if they are false • If a theory cannot be proven false, it is not scientific Occam’s (Ockham’s) Razor • When evaluating competing theories that can each explain all observations, the simplest theory is usually the correct one. The Greeks c. 300 BCE • Knew that the Earth was round o One’s views of constellations change as one moves north and south o Ship’s hull disappear first over the horizon o The Earth’s shadow on the Moon during eclipses is curved • Thought that the Earth was stationary o If one drops an object, it falls straight down o Wouldn’t there be winds if the Earth were moving? o We don’t feel any motion • Believed that theory was more important than observation Aristotle • Student of Plato • believed that there is a separation between the Earthly and the Heavenly o Earthly elements earth, water, air, and fire o Heavenly element: Quintessence (or ether) • 5 th element not found on Earth o Planets move on crystalline spheres of this material • Champion of the Geocentric (Earth-centered) model of the universe • Beliefs were held for nearly 2000 years Retro grade motion • Pattern that the planets moved backwards Planet=wanderer Ptolemy (100-170 AD) • Follower of Aristotle • Refined Aristotle’s geocentric system in the Almagest • Was able to explain retrograde motion of the planets • Used epicycles • His system made very accurate predictions of the motions of the planets for the observations • Planets move at constant speed; earthly objects slow down • Planets move in combinations of circles • Knew Mercury and Venus were always by the sun • By adding as many epicycles as you need, you could explain any motion Ptolemy’s model was so successful, “it helped prevent the advance astronomy for a millennium” 01/06-Wed Instruments used to measure the night sky (could measure angles but not distances) • Cross staff o Measures angles between any two points (stars or objects in the sky) • Hands o Distance between pointer finger and pinky is about 15 degrees • Quadrith (protractor with string) o Sight object thru holes and string lines up according to angle • Nocturnal o Tells time at night o Line up pointers as same angle as big dipper and little dipper and it gives you the time Everything in the sky was a little point of light besides the sun and the moon Copernicus (1473-1543) • Polish Catholic cleric, physician, scholar • Believed in heliocentric theory of the universe • The Little Commentary o Circulated a handwritten pamphlet describing his theory o Didn’t publish because he was afraid that other scholars would laugh at him...
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