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Announcements. Don’t forget to take the test! (today, tomorrow, Friday before class) Don’t discuss the test with classmates until class on Friday. Pick up graded homework. First project due in 9 days!. Earth as a Planet. 4 October 2006. Course Outline. Naked-eye astronomy
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Announcements • Don’t forget to take the test! (today, tomorrow, Friday before class) • Don’t discuss the test with classmates until class on Friday. • Pick up graded homework. • First project due in 9 days!
Earth as a Planet 4 October 2006
Course Outline • Naked-eye astronomy • Crash course in physics • Our solar system • The stars • Structure and history of the universe
Course Outline • Naked-eye astronomy • Crash course in physics • Our solar system • The stars • Structure and history of the universe You are here
Today: • Some important characteristics of Earth to keep in mind as we compare it to other planets
Earth • My favorite planet • Largest known rock • Very geologically active • Atmosphere of nitrogen and oxygen • 3/4 covered with water • Nice, comfortable surface temperature • Only known home of life
Earth • Made of rock (why?) • Hot inside (why?) • Atmosphere of nitrogen and oxygen (why?) • 3/4 covered with water (why?) • Nice, comfortable surface temperature (why?)
Some partial answers • Made of rock because heavy atoms (Si, O, C, Ca, Na, K, Fe, Mg) tend to form rocks, and light atoms (esp. H, He) are uncommon on earth (why?) • Hot inside because of radioactive decay of rare atoms (U, Th, K, Rb), plus some residual heat from earth’s formation; heat builds up and escapes slowly due to earth’s size • Atmosphere of nitrogen (N2) and oxygen (O2) because plant life has removed most carbon dioxide (CO2) and produced oxygen • 3/4 covered with water because of size and surface temperature • Nice, comfortable surface temperature because of our distance from the sun
Earth’s Moon • 1/4 earth’s diameter • 1/80 earth’s mass • Covered with craters, ancient lava flows • Geologically inactive • No atmosphere • Essentially no water • Hot days, cold nights • Only other world humans have visited