1. 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
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 :30 am
VLSB 2050
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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.
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3. 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!
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4. © 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
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5. From Berkeley From the Equator From the North Pole
Motion of the Night Sky
From Berkeley
From the Equator
From the North Pole
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Phases of the Moon
If the moon were farther away than the Sun, would it ever be a crescent?
Today’s Moon:
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11. Moon Going through phases
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If you stand on the Moon,
Does the Earth go through “phases” ?
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Eclipses:
Solar
Lunar
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Solar Eclipse
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Solar Eclipse at Earth
As seen from the Moon
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17. Solar Eclipse 1999 Aug 11 from the Russian Mir Space Station
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18. Total Solar Eclipse Lusaka, Zambia 2001
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19. By: Solar Physicsts Wendy Carlos and Fred Espenak India
Solar Eclipse 24 October 1995
By: Solar Physicsts Wendy Carlos and Fred Espenak
India
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20. 2002 total Solar Eclipse Ceduna, Australia Dec 4, 2002
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Last Time:
Lunar Eclipse
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22. Total Lunar Eclipse September 2002
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23. We see only one side of the Moon
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24. Why we always see the same face of the Moon
Rotation period = orbital period
Earth
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25. How to build a “model” (sketch) or a “theory” of the Solar System
It must explain all
the motions of the planets:
the “data”. . .
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26. 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.
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27. Motion of the Planets Relative to the Earth where we make observations
Sun and planets
seem to orbit the orbit the earth .
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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?
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29. Observed Motion of Mars: Normal & “Retrograde””
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30. To Explain Retrograde Motion Two Models: Geocentric Heliocentric
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31. 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)
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32. 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…
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33. Earth-Centered Theory Sun-Centered Theory
Which
Seems
“Best” ?
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34. 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.
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35. 3D “model” of the Solar System
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36. 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.
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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.
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38. 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.
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39. 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
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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 . . .
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Ancient Greek Science
How did the Greeks lay the foundations for modern science?
The Ptolemaic model (theory)
of the Solar System.
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Plato ( BC)
All natural motion is circular
Reason is more important than observation
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Aristotle ( BC)
Physics
elements
earth
water
air
fire
quintessence
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44. 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.”
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Epicurus ( 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…”
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46. © 2005 Pearson Education Inc., publishing as Addison-Wesley
Eratosthenes ( 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.
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47. Claudius Ptolemy (AD 100-170)
Theoretical Model of planets, Sun, Moon
His model fit the data, made accurate predictions, but was horribly contrived!
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48. 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
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49. 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
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Tycho Brahe ( )
Greatest observer of his day
• Charted accurate positions of planets
• Observed a nova in 1572
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Johannes Kepler ( )
Greatest theorist of his day
Imagined planets on “heavenly spheres”
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Kepler’s Laws
1. Each planet’s orbit around the Sun is an ellipse, with the Sun at one focus.
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53. Eccentricity of an Ellipse
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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.
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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
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Galileo Galilei ( )
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!
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57. 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.
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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!
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59. © 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
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60. 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
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61. Bad Scientific Practice
pseudoscience – masquerades as science, but does not follow the scientific rules of evidence
nonscience – establishes “truths” through belief
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Astrology
Claims to study how the positions of the Sun, Moon, & planets among the stars influence human behavior
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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.
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Signs of the Zodiac AQUARIUS January 19-February 17   PISCES February 18-March 19 ARIES March 20-April 18   TAURUS April 19-May 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
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66. 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
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67. © 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:
on that paper.
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68. Your Horoscope: All 12 Signs
Today: Jan 25, 2007 1 2 3 4 5 6 7 8 9 10 11 12
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69. 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.
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70. 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.
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71. Your Horoscope: All 12 Signs
Today: Jan 24, 2007 1 2 3 4 5 6 7 8 9 10 11 12
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72. © 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.
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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.
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76. Astrology: What is the Mechanism that makes it work?
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