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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. Tu, Th 11-12:30 am VLSB 2050. Announcements. Waitlist: Everyone will get in ! Read Chapters 1 & 2 .

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slide1
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

Tu, Th 11-12:30 am

VLSB 2050

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

slide2
Announcements
  • Waitlist: Everyone will get in !
  • Read Chapters 1 & 2 .
  • Discussion Sections meet this week.
  • Homework Assignment: Posted on Web.
  • 7 Problems / Questions
  • Due: Friday, Tomorrow, Feb 1
  • Turn in: Basement of Campbell Hall.

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

slide3
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.

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

the celestial sphere
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

motion of the night sky

Motion of the Night Sky

From Berkeley

From the Equator

From the North Pole

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

phases of the moon
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

MoonGoing through phases

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

slide12
If you stand on the Moon,

Does the Earth go through “phases” ?

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

eclipses

Eclipses:

Solar

Lunar

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

solar eclipse
Solar Eclipse

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

slide16
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

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

Total Solar EclipseLusaka, Zambia 2001

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

solar eclipse 24 october 1995

Solar Eclipse24 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

2002 total Solar EclipseCeduna, Australia Dec 4, 2002

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

lunar eclipse
Last Time:Lunar Eclipse

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

total lunar eclipse september 2002

Total Lunar EclipseSeptember 2002

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

we see only one side of the moon
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
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
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
Planets: Moving relative to the StarsObvious 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

Motion of the Planets Relative to the Earthwhere we make observations

Sun and planets

seem to orbit the orbit the earth .

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

the motion of planets
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

Observed Motion of Mars:Normal & “Retrograde””

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

to explain retrograde motion two models geocentric heliocentric
To Explain Retrograde Motion

Two Models:

Geocentric

Heliocentric

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

ptolemy s geocentric model
Ptolemy’sGeocentric 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
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

Earth-Centered Theory Sun-Centered Theory

Which

Seems

“Best” ?

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

choosing the best model explaining retrograde motion
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

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
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

parallax
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
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

scientific thinking
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

ancient greek science
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

plato 428 348 bc
Plato (428 - 348 BC)
  • All natural motion is circular
  • Reason is more important than observation

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

aristotle 384 322 bc
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
Democritus:Pre-SocraticGreekphilosopher(460 - 370 BC).

``There are innumerable worlds ofdifferent 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

epicurus 341 270 b c
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

slide46
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
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
Nicolaus Copernicus (1473-1543)

He thought Polemy’s model was contrived

Yet he believed in circular motion

De Revolutionibus Orbium Coelestium

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

copernicus heliocentric model
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

tycho brahe 1546 1601
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

johannes kepler 1571 1630
Johannes Kepler (1571-1630)
  • Greatest theorist of his day
  • Imagined planets on “heavenly spheres”

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

kepler s laws
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
Eccentricity of an Ellipse

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

kepler s 2nd law
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

kepler s 3rd law
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

galileo galilei 1564 1642
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.

Galileo’s Observations

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

slide58
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

the scientific method
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
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
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

astrology
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

astrology63
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

slide65
Signs of the ZodiacAQUARIUS January 19-February 17PISCES February 18-March 19ARIESMarch 20-April 18TAURUS April 19-May 19GEMINI May 20-June 19CANCER June 20-July 21LEO July 22-August 21VIRGO August 22-September 21LIBRA September 22-October 22SCORPIO October 23-November 20SAGITTARIUS November 21-December 20CAPRICORN December 21-January 18

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

your horoscope all 12 signs
Jan 25, 2007Your Horoscope: All 12 Signs

7

8

9

10

11

12

1

2

3

4

5

6

Geoff: Be sure to scramble

the order of the horoscopes

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

test of astrology
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 signs68
Today: Jan 25, 2007Your Horoscope: All 12 Signs

7

8

9

10

11

12

1

2

3

4

5

6

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

slide69
Theory: Astrology works

The horoscope for your sign of the zodiac

allows you to predictyour 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 signs70
Today: Jan 25, 2007Your Horoscope: All 12 Signs

7

8

9

10

11

12

1

2

3

4

5

6

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

your horoscope all 12 signs71
Today: Jan 24, 2007Your Horoscope: All 12 Signs

7

8

9

10

11

12

1

2

3

4

5

6

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

what have we learned
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

what have we learned73
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

astrology what is the mechanism that makes it work
Astrology:What is the Mechanismthat makes it work?

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

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