Copyright © 2009 Pearson Education, Inc. Chapter 3 The Science of AstronomyCopyright © 2009 Pearson Education, Inc. The NASA budget - decliningCopyright © 2009 Pearson Education, Inc.Copyright © 2009 Pearson Education, Inc. We have more astronomy satellites now than we have ever had! A golden age of astronomy at NASACopyright © 2009 Pearson Education, Inc. What is science? Some questions Question: Do you believe there is evidence of Global Warming? A. Yes B. No C. Not sureCopyright © 2009 Pearson Education, Inc. Next question Do you believe that the evidence shows that human activity is causing Global Warming? A. Yes B. No C. Not sureCopyright © 2009 Pearson Education, Inc. The same question Question: do you believe there is evidence of Global Warming? A. Yes B. No C. Not sureCopyright © 2009 Pearson Education, Inc. Science • Science requires data taking. The data must be held to very high standards, and must be repeatable • Science also requires hypotheses to test against the data. • A hypothesis that gives no prediction is pretty much useless • Karl Popper – the idea of “falsifiable” • A hypothesis that has been checked over and over again and found to be true is a “theory”Copyright © 2009 Pearson Education, Inc. 3.1 The Ancient Roots of Science • In what ways do all humans employ scientific thinking? • How did astronomical observations benefit ancient societies? • What did ancient civilizations achieve in astronomy? Our goals for learning:Copyright © 2009 Pearson Education, Inc. In what ways do all humans employ scientific thinking? • Scientific thinking is based on everyday ideas of observation and trial-and-error experiments.Copyright © 2009 Pearson Education, Inc. How did astronomical observations benefit ancient societies? • In keeping track of time and seasons — for practical purposes, including agriculture — for religious and ceremonial purposes • In aiding navigation • but they also created a corrupt class based on pseudo-scientific rites. Knowledge, not shared, can corrupt.Copyright © 2009 Pearson Education, Inc. What did ancient civilizations achieve in astronomy? • Daily timekeeping • Tracking the seasons and calendar • Monitoring lunar cycles • Monitoring planets and stars • Predicting eclipses • Great parties on New Years Eve • Human sacrifice • And more…Copyright © 2009 Pearson Education, Inc. • Egyptian obelisk: Shadows tell time of day.Copyright © 2009 Pearson Education, Inc. England: Stonehenge (completed around 1550 B.C.)Copyright © 2009 Pearson Education, Inc. Mexico: Model of the Templo MayorCopyright © 2009 Pearson Education, Inc. New Mexico: Anasazi kiva aligned north–southCopyright © 2009 Pearson Education, Inc. SW United States: “Sun Dagger” marks summer solsticeCopyright © 2009 Pearson Education, Inc. Scotland: 4000-year-old stone circle; Moon rises as shown here every 18.6 years.Copyright © 2009 Pearson Education, Inc. Peru: Lines and patterns, some aligned with starsCopyright © 2009 Pearson Education, Inc. Macchu Pichu, Peru: Structures aligned with solsticesCopyright © 2009 Pearson Education, Inc. South Pacific: Polynesians were very skilled in the art of celestial navigation.Copyright © 2009 Pearson Education, Inc. France: Cave paintings from 18,000 B.C. may suggest knowledge of lunar phases (29 dots). I think this is crapCopyright © 2009 Pearson Education, Inc. China: Earliest known records of supernova explosions (1400 B.C.) Bone or tortoiseshell inscription from the 14th century B.C. "On the Xinwei day the new star dwindled." "On the Jisi day, the 7th day of the month, a big new star appeared in the company of the Ho star."Copyright © 2009 Pearson Education, Inc. What have we learned? • In what ways do all humans employ scientific thinking? — Scientific thinking involves the same type of trial-and-error thinking that we use in our everyday lives, but in a carefully organized way. • How did astronomical observations benefit ancient societies? — Keeping track of time and seasons; navigationCopyright © 2009 Pearson Education, Inc. What have we learned? • What did ancient civilizations achieve in astronomy? — To tell the time of day and year, to track cycles of the Moon, to observe planets and stars. (Many ancient structures aided in astronomical observations.)Copyright © 2009 Pearson Education, Inc. 3.2 Ancient Greek Science • Why does modern science trace its roots to the Greeks? • How did the Greeks explain planetary motion? • How did Islamic scientists preserve and extend Greek science? Our goals for learning:Copyright © 2009 Pearson Education, Inc. Our mathematical and scientific heritage originated with the civilizations of the Middle East following roughly the dispora of the family of Abrahm.Copyright © 2009 Pearson Education, Inc. Artist’s reconstruction of the Library of AlexandriaCopyright © 2009 Pearson Education, Inc. • Greeks were the first people known to make models of nature. • They tried to explain patterns in nature without resorting to myth or the supernatural. Greek geocentric model (c. 400 B.C.) Why does modern science trace its roots to the Greeks?Copyright © 2009 Pearson Education, Inc. Greek Science was not like ours • The Greeks were very careful about the difference between “truth” and “theory” • They did not necessarily believe that the planets did what was said in their theory. The theory was just a model. • Truth was unknowable – it was faith.Copyright © 2009 Pearson Education, Inc. Special Topic: Eratosthenes measures the Earth (c. 240 B.C.) Calculate circumference of Earth: 7/360 × (circum. Earth) = 5000 stadia ⇒ circum. Earth = 5000 × 360/7 stadia ≈ 250,000 stadia Measurements: Syene to Alexandria • distance ≈ 5000 stadia • angle = 7° Compare to modern value (≈ 40,100 km): Greek stadium ≈ 1/6 km ⇒ 250,000 stadia ≈ 42,000 kmCopyright © 2009 Pearson Education, Inc. Underpinnings of the Greek geocentric model: Plato Aristotle How did the Greeks explain planetary motion? • Earth at the center of the universe • Heavens must be “perfect”—objects move on perfect spheres or in perfect circles.Copyright © 2009 Pearson Education, Inc. But this made it difficult to explain the apparent
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