The Planets Prof. Michael Manga Prof. Geoff Marcy 3 Units Astronomy and Earth & Planetary Science C12 Letters & Science C70 The Planets Dione Against Saturn & Ring Taken: October 11 2005 Prof. Michael Manga Prof. Geoff Marcy This course can be used to satisfy the Physical Science breadth requirement in the College of Letters & Science 3 Units Tu, Th 11-12:30 am VLSB 2050 © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Announcements Waitlist: Everyone will get in ! Read Chapters 1 & 2 . Discussion Sections meet this week. Homework Assignment: Posted on Web. There will be NO sections this week, but pls. read Ch. 1 & Ch. 2 of text by next Tuesday You should get an account in Blackboard, where these announcements and assignments are posted This is not a mathematical course, but there is simple arithmetic such as used for filling out taxes. Also powers of ten: we will be discussing. The main source of material is the book, but lectures tell you what is important (and fill out detail – the book is brief) Falling behind in reading or homework makes life very tough for you – It’s really hard to cram this material at the end! 7 Problems / Questions Due: Friday, Tomorrow, Feb 1 Turn in: Basement of Campbell Hall. © 2005 Pearson Education Inc., publishing as Addison-Wesley

Telescope Observations Project Two Parts 1. Make Telescope Observations of two objects Suggestions: Saturn, Mars, Orion Nebula Telescope Hours: Tue & Thu 7-8 pm, 7th floor of Campbell Hall Sketch both objects on 1/2 sheet of paper. Note Date and Time. Mark the position of Mars with a dot, at three times during the Semester, early, middle, late. (Use either map.) Note date of each observation. There will be NO sections this week, but pls. read Ch. 1 & Ch. 2 of text by next Tuesday You should get an account in Blackboard, where these announcements and assignments are posted This is not a mathematical course, but there is simple arithmetic such as used for filling out taxes. Also powers of ten: we will be discussing. The main source of material is the book, but lectures tell you what is important (and fill out detail – the book is brief) Falling behind in reading or homework makes life very tough for you – It’s really hard to cram this material at the end! © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Last Time: Useful Spherical Coordinate System The Celestial Sphere North Celestial Pole Near the ”North Star” Stars “glued” to sphere Constellations: Apparent groupings North & South “Celestial poles” Celestial equator Ecliptic: Sun’s path against the stars = Orbital plane of Earth Celestial Sphere Rotates around us every 24 hours: As Earth spins . Celestial Equator © 2005 Pearson Education Inc., publishing as Addison-Wesley

From Berkeley From the Equator From the North Pole Motion of the Night Sky From Berkeley From the Equator From the North Pole © 2005 Pearson Education Inc., publishing as Addison-Wesley

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© 2005 Pearson Education Inc., publishing as Addison-Wesley Phases of the Moon If the moon were farther away than the Sun, would it ever be a crescent? Today’s Moon: http://www.calculatorcat.com/moon_phases/phasenow.php?tcv=49 © 2005 Pearson Education Inc., publishing as Addison-Wesley

Moon Going through phases © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley If you stand on the Moon, Does the Earth go through “phases” ? © 2005 Pearson Education Inc., publishing as Addison-Wesley

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© 2005 Pearson Education Inc., publishing as Addison-Wesley Eclipses: Solar Lunar © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Solar Eclipse © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Solar Eclipse at Earth As seen from the Moon © 2005 Pearson Education Inc., publishing as Addison-Wesley

Solar Eclipse 1999 Aug 11 from the Russian Mir Space Station © 2005 Pearson Education Inc., publishing as Addison-Wesley

Total Solar Eclipse Lusaka, Zambia 2001 © 2005 Pearson Education Inc., publishing as Addison-Wesley

By: Solar Physicsts Wendy Carlos and Fred Espenak India Solar Eclipse 24 October 1995 By: Solar Physicsts Wendy Carlos and Fred Espenak India © 2005 Pearson Education Inc., publishing as Addison-Wesley

2002 total Solar Eclipse Ceduna, Australia Dec 4, 2002 © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Last Time: Lunar Eclipse © 2005 Pearson Education Inc., publishing as Addison-Wesley

Total Lunar Eclipse September 2002 © 2005 Pearson Education Inc., publishing as Addison-Wesley

We see only one side of the Moon © 2005 Pearson Education Inc., publishing as Addison-Wesley

Why we always see the same face of the Moon Rotation period = orbital period Earth © 2005 Pearson Education Inc., publishing as Addison-Wesley

How to build a “model” (sketch) or a “theory” of the Solar System It must explain all the motions of the planets: the “data”. . . © 2005 Pearson Education Inc., publishing as Addison-Wesley

Planets: Moving relative to the Stars Obvious to the eye Mercury Difficult to see; Always angularly close to Sun Venus Very bright. Always near Sun— morning or evening “star” Mars Noticeably orange. Usually moves west-to-east Sometimes backwards “retrograde” ! Jupiter Very bright. Moves west-to-east against stars. Saturn Moderately bright. Moves more slowly west-to-east. © 2005 Pearson Education Inc., publishing as Addison-Wesley

Motion of the Planets Relative to the Earth where we make observations Sun and planets seem to orbit the orbit the earth . © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley The Motion of Planets The Planets normally move West to East against the background stars. Why do planets sometimes seem to move backwards relative to the stars? Greeks concluded that the planets orbit the Earth. Why did smart people conclude this? © 2005 Pearson Education Inc., publishing as Addison-Wesley

Observed Motion of Mars: Normal & “Retrograde”” © 2005 Pearson Education Inc., publishing as Addison-Wesley

To Explain Retrograde Motion Two Models: Geocentric Heliocentric © 2005 Pearson Education Inc., publishing as Addison-Wesley

Ptolemy’s Geocentric Model Earth is at center Sun orbits Earth Planets orbit on small circles whose centers orbit the Earth on larger circles (The small circles are called epicycles) © 2005 Pearson Education Inc., publishing as Addison-Wesley

In Heliocentric “model” Retrograde Motion is a Natural Consequence Planets usually appear to move eastward relative to the stars. But as we pass by them, planets seem to move west relative to the stars. Only noticeable over many nights; on a single night, a planet rises in east and sets in west… © 2005 Pearson Education Inc., publishing as Addison-Wesley

Earth-Centered Theory Sun-Centered Theory Which Seems “Best” ? © 2005 Pearson Education Inc., publishing as Addison-Wesley

Choosing the Best Model: Explaining Retrograde Motion Natural result of Heliocentric Model Difficult to explain if Earth is at center The Best “Model” or “Theory” explains various data and phenomena with the fewest assumptions. “Occam’s Razor “: Choose the simplest model that explains all the data. © 2005 Pearson Education Inc., publishing as Addison-Wesley

3D “model” of the Solar System © 2005 Pearson Education Inc., publishing as Addison-Wesley

Why did the Greeks reject the theory that the Earth orbits the Sun? It ran contrary to their common sense: Every day, the sun, moon, and stars rotates around us. So, we “must be” at the center . . . If the Earth rotated, then there should be a “great wind” as we moved through the air. Greeks knew that we should see stellar “parallax” if we orbited the Sun – but they could not detect it. © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Test the Theory that Earth orbits the Sun: Parallax: Apparent shift of a star’s position due to the Earth’s orbiting of the Sun. Greeks didn’t detect parallax ! The nearest stars are much farther away than the Greeks thought. The parallax angles of the stars are so small, that you need a telescope to observe them. © 2005 Pearson Education Inc., publishing as Addison-Wesley

Two Possible reasons why stellar parallax was not detected: Stars are so far away that stellar parallax is too small for naked eye to notice. Earth does not orbit Sun; it is the center of the universe. Debate about theory: Earth-centered vs. Sun-centered Planetary System. © 2005 Pearson Education Inc., publishing as Addison-Wesley

The Science of Astronomy Chapter 3: The Science of Astronomy We especially need imagination in science. It is not all mathematics, nor all logic, but is somewhat beauty and poetry. Maria Mitchell (1818 – 1889) Astronomer and first woman elected to American Academy of Arts & Sciences © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Scientific Thinking It is a natural part of human curiosity: Search for understanding and truths that explain many facts. We draw conclusions based on our experiences. Progress is made through “trial and error.” Hypothesize. Then test your hypothesis. Eating Carbohydrates make me get fat . . . © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Ancient Greek Science How did the Greeks lay the foundations for modern science? The Ptolemaic model (theory) of the Solar System. © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Plato (428 - 348 BC) All natural motion is circular Reason is more important than observation © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Aristotle (384 -322 BC) Physics elements earth water air fire quintessence © 2005 Pearson Education Inc., publishing as Addison-Wesley

Democritus: Pre-Socratic Greek philosopher (460 - 370 BC). ``There are innumerable worlds of different sizes. These worlds are at irregular distances, more in one direction and less in another, and some are flourishing, others declining. Some of the worlds have no animal or vegetable life nor any water.” © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Epicurus (341-270 B.C.) Greek philosopher in Athens where he opened a school of philosophy “There are infinite worlds both like and unlike this world of ours ... we must believe that in all worlds there are living creatures and plants and other things we see in this world…” © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Eratosthenes (276 - 195 BC) He measured the circumference of the Earth. The Sun is at the zenith in the city of Syene at noon on the summer solstice. But at the same time in Alexandria, it is 7 from the zenith. Eratosthenes inferred that Alexandria was 7 of latitude north of Syene. The distance between the two cities is 800 km. Dist = 7/360 times the Earth’s circumference. His result of 42,000 km is very close to the right number: 40,000 km. © 2005 Pearson Education Inc., publishing as Addison-Wesley

Claudius Ptolemy (AD 100-170) Theoretical Model of planets, Sun, Moon His model fit the data, made accurate predictions, but was horribly contrived! © 2005 Pearson Education Inc., publishing as Addison-Wesley

Nicolaus Copernicus (1473-1543) He thought Polemy’s model was contrived Yet he believed in circular motion De Revolutionibus Orbium Coelestium Replace picture with Fig. 3.16.1 © 2005 Pearson Education Inc., publishing as Addison-Wesley

Copernicus’ Heliocentric Model Sun is at center Earth orbits like any other planet Inferior planet orbits are smaller Retrograde motion occurs when we “lap” Mars & the other superior planets © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Tycho Brahe (1546-1601) Greatest observer of his day • Charted accurate positions of planets • Observed a nova in 1572 © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Johannes Kepler (1571-1630) Greatest theorist of his day Imagined planets on “heavenly spheres” © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Kepler’s Laws 1. Each planet’s orbit around the Sun is an ellipse, with the Sun at one focus. © 2005 Pearson Education Inc., publishing as Addison-Wesley

Eccentricity of an Ellipse © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Kepler’s 2nd Law A planet moves along its orbit with a speed that changes in such a way that a line from the planet to the Sun sweeps out equal areas in equal intervals of time. © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Kepler’s 3rd Law The cube of a planet’s average distance from the Sun is equal to the square of its orbital period. (Use units of years and AUs.) a3 = P2 © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Galileo Galilei (1564-1642) First man to point a telescope at the sky wanted to connect physics on earth with the heavens Dialogue Concerning the Two Chief World Systems [written in Italian] This book got him in trouble with the Church! © 2005 Pearson Education Inc., publishing as Addison-Wesley

Galileo’s Observations Galileo discovered that Jupiter had four moons of its own. Jupiter was the center of its own system. Heavenly bodies existed which did not orbit the earth. © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Galileo’s observation of the phases of Venus was the final evidence which buried the geocentric model. Geocentric Heliocentric No gibbous or full phases! All phases are seen! Galileo observed all phases! © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley The Scientific Method Question Hypothesis a tentative explanation Prediction Test Result confirm, reject, or modify should be the same no matter who conducts the test © 2005 Pearson Education Inc., publishing as Addison-Wesley

Hallmarks of Good Science Science seeks explanations for observed phenomena that rely solely on natural causes. Science progresses through the creation and testing of models of nature that explain the observations as simply as possible. Occam’s Razor A scientific model must make testable predictions that could force us to revise or abandon the model. Theory -- a model which survives repeated testing © 2005 Pearson Education Inc., publishing as Addison-Wesley

Bad Scientific Practice pseudoscience – masquerades as science, but does not follow the scientific rules of evidence nonscience – establishes “truths” through belief © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Astrology Claims to study how the positions of the Sun, Moon, & planets among the stars influence human behavior © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Astrology Theory: The positions of the planets, sun, and moon at the time of your birth determine your personality and your future, day to day. © 2005 Pearson Education Inc., publishing as Addison-Wesley

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© 2005 Pearson Education Inc., publishing as Addison-Wesley Signs of the Zodiac AQUARIUS January 19-February 17   PISCES February 18-March 19 ARIES March 20-April 18   TAURUS April 19-May 19 GEMINI May 20-June 19   CANCER June 20-July 21   LEO July 22-August 21   VIRGO August 22-September 21 LIBRA September 22-October 22 SCORPIO October 23-November 20   SAGITTARIUS November 21-December 20 CAPRICORN December 21-January 18 © 2005 Pearson Education Inc., publishing as Addison-Wesley

Your Horoscope: All 12 Signs Jan 25, 2007 Your Horoscope: All 12 Signs 1 2 3 4 5 6 7 8 9 10 11 12 Geoff: Be sure to scramble the order of the horoscopes © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley Test of Astrology Write your “sign” of the zodiac on one sheet of paper. Choose the horoscope that best describes your day today Write the NUMBER of that paragraph: 1 - 12 on that paper. © 2005 Pearson Education Inc., publishing as Addison-Wesley

Your Horoscope: All 12 Signs Today: Jan 25, 2007 1 2 3 4 5 6 7 8 9 10 11 12 © 2005 Pearson Education Inc., publishing as Addison-Wesley

Theory: Astrology works The horoscope for your sign of the zodiac allows you to predict your future. Design a Test: If Theory is True: Your horoscope matches your situation today (challenges, opportunities, experiences) . Most of you will choose the paragraph corresponding to your actual sign of the zodiac If theory is not true. In that case, your chosen horoscope will be random. For example, only a fraction of the “Leo’s” will choose their horoscope. © 2005 Pearson Education Inc., publishing as Addison-Wesley

Your Horoscope: All 12 Signs Today: Jan 25, 2007 1 2 3 4 5 6 7 8 9 10 11 12 If you are aquarius, please stand up. Hold up the number of your horoscope. If you’re right, you all chose the same number. Now, let me reveal which horoscope is really aquarius. If you didn’t choose that number, please sit down. You’ve been voted off your horoscsope. Only 3 out of N got it right. © 2005 Pearson Education Inc., publishing as Addison-Wesley

Your Horoscope: All 12 Signs Today: Jan 24, 2007 1 2 3 4 5 6 7 8 9 10 11 12 © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley What have we learned? What is a theory in science? A model that explains a wide variety of observations in terms of just a few general principles, which has survived numerous tests to verify its predictions and explanations. How were astronomy and astrology related in the past, and are they still related today? Astronomy and astrology both grew out of ancient observations of the sky. Astronomy grew into a modern science. Astrology has never passed scientific tests and does not qualify as science. © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley What have we learned? How can we distinguish science from nonscience? It’s not always easy, but science generally exhibits at least three hallmarks. (1) Modern science seeks explanations for observed phenomena that rely solely on natural causes. (2) Science progresses through the creation and testing of models of nature that explain the observations as simply as possible. (3) A scientific model must make testable predictions about natural phenomena that would force us to revise or abandon the model if the predictions do not agree with observations. © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley

Astrology: What is the Mechanism that makes it work? © 2005 Pearson Education Inc., publishing as Addison-Wesley

© 2005 Pearson Education Inc., publishing as Addison-Wesley