Class Notes - Modern Cosmology (1 st Mid-Term) 01/04- Mon...

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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 Occams (Ockhams) 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 Ones views of constellations change as one moves north and south o Ships hull disappear first over the horizon o The Earths 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 Wouldnt there be winds if the Earth were moving? o We dont 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 Aristotles 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 Ptolemys 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 Didnt publish because he was afraid that other scholars would laugh at him...
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Class Notes - Modern Cosmology (1 st Mid-Term) 01/04- Mon...

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