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geo - ch1 class notes

geo - ch1 class notes - Cosmology conscious thought...

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Cosmology conscious thought distinguishes humans - developed across 1,000s of generations - lends us curiosity, insight, and the ability to learn as a result, we seek to explain our surroundings - where do we come from? - where do we fit in the universe? - why are we here? = study of the structure and history of the universe cosmology is a complicated science requires thinking in unfamiliar scales of space and time - spatial scales Zeptometers (10^-21 meters), to 10s of billions of light years (9.46 x 10^22 meters +) - temporal scales zeptoseconds (10^-21 seconds), to 10s of billions of years (3.15 x 10^17 seconds +) Earth’s Changing Place 3,000 years ago, humans knew the heavens well - they knew: stars were fixed relative to other stars stars moved predictably across the sky they saw retrograde motion separating planets from stars but they did not think of Earth as a planet movement in the heavens was attributed to deities
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Evolving image of earth the ancients though the Universe was geocentric - heavenly bodies circle around a motionless central Earth - “proven” by Ptolemy (100-170 CE), the idea was wrong - the idea held as religious dogma for 1,400 years a heliocentric (sun-centered) universe was proposed by the Greeks ~ 250 BCE the renaissance rebirth of rational thought in 15th century Europe Spawned a new age of scientific discovery - Copernicus - published evidence for heliocentricity - Kepler - his elliptical planetary orbits refuted Ptolemy - Galileo - observed moons orbiting Jupiter - Newton - planet motion explained by his Theory of Gravity Natural laws governed natural events geocentricity faded away THe Solar System solar system = a sun, planets, moons, and other objects Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune Earth shares the solar system with 7 planets a planet: - is a large solid body orbiting a star (the sun) - has a nearly spherical shape - has cleared it’s neighborhood of all other objects moon = a solid body locked in orbit around a planet the solar system also includes asteroids and comets
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THe Planets two groups of planets occur in the solar system - terrestrial (earthlike) = small, dense, rocky planets Mercury Venus Earth Mars - Jovian (jupiter-like) - large, low density, gas-giant planets Jupiter Saturn Uranus Neptune Pluto is no longer considered to be a planet The Solar System the terrestrial planets are the 4 most interior the Jovian planets occupy the 4 outermost orbits the asteroid belt lies between Mars and Jupiter planet orbital planes lie within 3 ° of the Sun’s equator Stars and Galaxies stars are immense balls of incandescent gas - light and heat derives from nuclear fusion reactions - gravity binds stars together into vast galaxies the solar system is on an arm of the Milky Way galaxy - our sun is one of 300 billion stars in the Milky Way
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The Andromeda galaxy is 2.2 million light years away - the speed of light is 186,000 mile/s the moon is 1.3 light seconds (~237,000 miles) away
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