NATS 1 - Scientific explananations.They are tentative they...

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Scientific explananations .They are tentative they are based on empirical observations Predictable and testable Provide a well- defined natural cause toexplain the occurrence of a natural event Science is . . .• . . . a process of discovery that increases ourbody of knowledge.• . . . information that can be learned; much of itis waiting to bediscovered.• . . . the curiosity and creativity of scientists in the search for answers to critical questions. Science is not . . .• . . . a list of facts to be memorized . What is Science? To “do science” we need observations, a testable hypothesis,and one or more predictions based on the hypothesis. Stars and Planets Space• Stars use hydrogen as fuel! Very high temperatures and pressures in the interiors of stars fuse hydrogen atoms together – nuclear fusion – to! Stars burn out when hydrogenis used up… some go out violently(supernovas)… some die less violently (e.g. our Sun)Clouds of hydrogen gas and dust in Eagle Nebulaare incubators for the formation of new stars.• Hydrogen (and helium) formed soon after the Big Bang • Other elements and complex compounds formed during the life cycle of stars Stars and Planets • Stars vary in size, age! Giant stars burn out faster (10-20 million years) and die violently (supernovas)! Supernovas create all the heavy elements! We are truly made of star dust!! Intermediate-sized stars such as the sun will last approximately10 billion years, and end as coldballs of carbonLife cycle stages and types of stars(Hertsprung-Russell diagram). Stars and Planets • When stars form they are surrounded by a rotating disk of cosmic debris• Gravity pulls debris together to form planets that revolve in a consistent direction around star! Heavier, rocky planets closer to star! Lighter, gas-rich planets farther from star• Potentially thousands or millions of extra-solar planets revolve around other stars• A star and its planets(i.e., a Solar System)all form at the same time• The Big Bang explains the formation of the Universe, notsolar systems! Our Solar System 4 Terrestrial planets(Mercury, Venus,Earth, Mars) Eight Planets: 4 Jovian planets(Jupiter, Saturn,Uranus, Neptune) ( Note Change of Scale!!) Plate Tectonics Conceptest The Good Earth/Chapter 4: Plate TectonicsWhich of the lines of evidence were notused to support Wegener’s continentaldrift hypothesis? Evidence from the Seafloor Seafloor topography! Age of the seafloor! Heat flow! VolcanoesEarthquakesIn the decades following Wegener’s research,key observations about the seafloor contributedto a new understanding of Earth processes Evidence from the • Age of seafloor rocksvaries systematically• Rocks of the seafloorare young comparedto most rocks on thecontinents! Rocks on ocean flooryounger than 200million years old! Rocks on continents asold as 4,000 millionyears 1 . Where are the youngest rocks?2. Where are the oldest rocks? Evidence from the Seafloor Polarity of seafloor alternatesbetween normal (+) andreverse (-) on either side ofoceanic ridge
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This note was uploaded on 06/16/2008 for the course NATS 102 taught by Professor Coyne during the Spring '08 term at Arizona.

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NATS 1 - Scientific explananations.They are tentative they...

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