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Kepler’s LawsKepler’s Laws

…lots and lots and lots of math.2/18/1996

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Goal

• Is astrology a science?• Why should we care?• Kepler: Astrologer turned Astronomer.• Kepler’s Laws.• Proof of Kepler’s Laws.• Planets around other stars.

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Recap

• Science is about making theories.• Scientific theories:

– Explain what is already seen– Predict what can be seen in the future.

• Predictions can be falsified.

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Astrology

• The date, time, (and place) of birth affect:– Your personality– Your actions– Events that will affect your life

• Horoscopes appear in most papers.• Millions of people read them daily.

http://www.azcentral.com/ent/horoscopes/astrology101.html

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Astrology

• Is it a science?– Explain what is seen?– Make predictions?

• Does it work?• What test would falsify astrology?• Does it matter?

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Astrology and the President

(TIME, May 16, 1988) -- “The First Lady dabbled in astrology as far back as 1967. In 1981 [Joan] Quigley made Nancy a believer …. And from then on, no presidential public appearance was slated without the Friend's say-so. To this day, Nancy's Friend continues to influence the President's schedule. For the Reagan-Gorbachev Washington summit, she cast the charts of both men and determinedthat 2 p.m. on Dec. 8, 1987, was the most propitious moment for them to sign the intermediate-range nuclear forces treaty. At Nancy's behest, the entire summit was built around that hour. For the upcoming Moscow summit, Gorbachev's chart (he is a Pisces) has been recast alongside Reagan's (Aquarius).”

“[Former White House Chief of Staff, Donald] Regan and others make a compelling case that in 1986 and 1987 astrological influence dramatically reduced the presidency's effectiveness, at least partly, by keeping Ronald Reagan under wraps for much of the time. Nancy's intrusions in the scheduling process, Regan said in an interview with TIME last week, ‘began to interfere with the normal conduct of the presidency.’”

(TIME, May 16, 1988)

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It Works

Courtesy NASA/JPL/Cornell

33Courtesy NASA/JPL/Cornell

Mars

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Orbital Mechanics

Courtesy David Crisp and WFPC2 Science Team

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Kepler’s Laws

1. Orbits are always ellipses.

2. Sweep out equal areas in equal times.

3. The period of orbit is related to average separation.

32 SeparationPeriod

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Astrology to Astronomy

• Kepler was an astrologer.• Looked for Perfect Solids• Wants did not match with Observations

(tests).• Followed the facts where they led.• The result works.

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Class Structure

Investigate 4 Key Topics this semester:1. Extrasolar Planets2. Black Holes3. The Big Bang4. SETI

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Class Structure

• During each topic:– Pieces in a puzzle.– Many pieces in several topics

• At the end of each topic:– See how pieces fit.– See how the scientific method is applied– What is the evidence– Have a test.

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Homework #3Homework #3

• For Lab this week:• Read Bennett chapter 1.1 – 1.2

– (B1.1 – 1.2 on Physics 103 lecture web page)

• For Thursday 1/22:• Read Ty7, Ty8, B6.1 – 6.3• Do B6: Problems 1, 2, 3, 7, 15

– (PHYS 170: replace problem 15 with 20a,b)