IntroAstronomy - Key Concept 1 Light Travel Time • Light...

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Cosmos: from the Greek meaning “orderly system or arrangement, ornaments Antonym: chaos Our cosmos is an orderly, structured place with well defined laws apparent to all: Is it? Predictable or probabilistic? Skin deep? Views of the Universe: apparent vs. actual Apparent: earth is flat, things naturally at rest, sky is a dome, sun, moon, planets, stars orbit Earth Actual: nothing at rest, Earth rotates, Earth is a spheroid, space is curved, earth orbits the sun, everything spins, the sky changing Solar (stellar) system A star and all the material that orbits it, including its planets and moon How many? Don’t know 500 at last count Galaxy A great island of stars in space, all held together by gravity and orbiting a common center Supermassive black holes In the center of galaxy Universe The sum total of all matter and energy; that is, everything within and between all galaxies Not just everything we see Ordered or chaotic, or both? Order from chaos?
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Unformatted text preview: Key Concept 1: Light Travel Time • Light travels at a finite speed(300,000 km/s), unit of distance • Thus, we see objects as they were in the past: the farther away we look in the distance, the further back we look in time o If far enough away, some of the things we see may no longer be there • Moon: 1 second • Sun: 8 Minutes • Sirius: 8 years • Andromeda Galaxy: 2.5 million years • Front of class: 10-100 billionths of a second • Light Year: o Distance light can travel in one year o Speed of light x 1 year o 9.461 x 10^12 km o 31 million seconds in a year • How far can we see? o 14 billion light-years – light from objects further from that has not had time to reach us o looking back 15 billion years is looking at a time before the universe existed o looking back before space was transparent is another problem – became transparent 300,000 years after universe formed...
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IntroAstronomy - Key Concept 1 Light Travel Time • Light...

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