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Test 1 results

Mean: 82Median: 87

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Polar circles

90o – L – 23.5o ~ 0, -> L ~ 66.5o

At winter solstice:

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The axial tilt angle is not constant, but has a complex motion determined by many cycles of short to very long periods. Due to nutation the tilt oscillates over 9" (about 280 m on the surface) over a period of 18.6 years. The main long-term cycle has a period of 41000 years and an amplitude of about 0.68°, or 76 km on the surface. Currently the tilt is decreasing by about 0.47" per year, so the Arctic Circle is moving north by about 15 m per year.

Real life complications

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Precession

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Ecliptic and Zodiac

Sun travels 360o/365.25 days ~ 1o/day

Ophiuchus

Astrology

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History of Astrology

• Originated by Babylonians about 1000 BC (mundane astrology, i.e. applies to the world)

• Greeks developed natal (birth) astrology (codified by Ptolemy in Tetrabiblos, 2nd century AD)

Argues that a person's character and destiny can be understood from the positions of the Sun, Moon, and planets at the moment of his or her birth.

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Astrology — big business

• 10,000 practicing astrologers

• 1000 full-time professionals

• 20 astrological journals

• 10 new books a week

• > 1000 newspapers with astrological forecasts

• 5 million people spend ~ $200 M per year consulting astrologers

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Horoscope

• Natal chart uses astronomical information and date and location of birth

• Planets, Moon, & Sun in signs of zodiac

• Interpretation step: positions of celestial bodies are used to predict a person’s character and destiny

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Does it work?

• No evidence that it does

• Lots of evidence that it doesn’t

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Math Corner

• How do we decide if a test is statistically significant?

• Coin tossing experiment (flip a coin 20 times and count how many “heads” show up)

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Statistically Significant

• If N hits expected, deviations of sqrt(N) from the expected value

• Example: flipping a coin• 18 flips: 9 plus or minus 3 (33% error)• 20,000 flips: 10,000 plus or minus 100

(1% error)• If someone claims that he can “predict” the

outcome and his predictions are within sqrt(N) of the mean value, he is a liar.

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Example (Gauquelin)

• 15,560 successful individuals in 10 professions– No statistically significant relation between

Sun sign and profession

• Gave a free horoscope evaluation to anyone who wanted it– 95% said they recognized themselves– but it was the horoscope of France’s worst

mass murderer

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Example - Silverman

• 2978 marriages and 478 divorces in Michigan

• No correlations between astrological signs and statistics of marriages/divorces found

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Example - McGervey

• Birth dates and biographies of 6000 politicians and 17000 scientists

• Found the astrological signs for both group to be distributed completely at random

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Astrology — conclusion

• No predictive power

• No scientific basis

• Broad psychological appeal– Cheap, easy, and entertaining– May help some people (as do many forms of

empathetic counseling)– Useless or damaging in other cases

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Pseudoscience: Why bother?• Many people view science as just another belief

system• Poor understanding about the difference

between science and pseudoscience• Widespread ignorance of what constitutes

evidence• Ideological doctrines (religious, political etc.)

obstructed the progress in science and culture many times in history: Inquisition, Nazi Germany, Communist Russia etc.

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How to recognize pseudoscience?

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Goals

• Science: The primary goal of science is to achieve a more complete and more unified understanding of the physical world.

• Pseudosciences are more likely to be driven by ideological, cultural, or commercial goals.

Some examples: astrology (from ancient Babylonian culture,) UFO-ology (popular culture and mistrust of government), Creation Science (attempt to justify Biblical interpretation)

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Predictive?• science: Must be (falsifiability). Workers

in the field commonly seek out counterexamples or findings that appear to be inconsistent with accepted theories.

• pseudoscience: No. A challenge to accepted dogma is often considered a hostile act if not heresy, and leads to bitter disputes or even schisms.

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Role of evidence?• science: independently verifiable, no

contradictions allowed. Each principle must be tested in the crucible of experience and remains subject to being questioned or rejected at any time.

• pseudoscience: anecdotal, not independently verifiable. Observations or data that are not consistent with established beliefs tend to be ignored or actively suppressed.

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Innovation?• science: can incorporate new evidence; models

change; old ideas are built upon, modified where necessary

• pseudoscience: relatively rigid and authoritarian since it is not based on empirical evidence. The field has evolved very little since it was first established. The small amount of research and experimentation that is carried out is generally done more to justify the belief than to extend it.

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Authority?• science: no special “experts” recognized.

Scientific ideas and concepts must stand or fall on their own merits, based on existing knowledge and on evidence.

• pseudoscience: often based on ancient authority; high priests and priestesses

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Appeals to our needs and desires?

• science: may or may not• pseudoscience: yes