Eclipses Old Dead Guys Part I
Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015
Quotes & Cartoon of the Day
“I much prefer the sharpest criticism of a single intelligent man to the thoughtless approval of the masses. “ -- Johannes Kepler Astronomy 1 - Elementary Astronomy
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Announcements
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First HW will be graded Monday & key posted
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Practice HW on Lunar Phases posted with key
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Use this to study, no credit awarded
Have you picked your observing project? First midterm Wednesday (10/1), through Night Sky material
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No late submissions accepted after key is posted.
Eclipses from today, but not rest of today’s material Rest of schedule still needs tweaking
Total Lunar eclipse Sunday night!
Astronomy 1 - Elementary Astronomy
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Last Class
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LT: Predicting Lunar Phases Eclipses (???)
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we just missed the questions, right?
History Ancients-Galileo
Astronomy 1 - Elementary Astronomy
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This Class
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Eclipses (if not done Monday) History Ancients-Galileo
Astronomy 1 - Elementary Astronomy
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ECLIPSES
Eclipses
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Lunar eclipse — Earth precisely between Moon and Sun
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Earth’s shadow falls on Moon Moon goes dark (reddish actually)
Solar eclipse — Moon precisely between Sun and Earth
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Moon’s shadow falls on Earth
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partly in some places (partial solar eclipse)
Sunlight blocked completely in some places (total solar eclipse)
and not at all in most places
Astronomy 1 - Elementary Astronomy
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Apparent Size of Sun and Moon
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The Sun and Moon appear to have the same size when viewed from Earth.
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Makes total solar eclipse possible
Astronomy 1 - Elementary Astronomy
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Eclipses
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So... once a month the Moon is between the Earth and the Sun....
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New Moon…
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Why don’t we have a solar eclipse every month?
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Or a lunar eclipse every month?
Astronomy 1 - Elementary Astronomy
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The Moon’s Orbit is tilted
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The Moon’s orbit tilted relative to the Earth’s orbit around the sun by about 5°
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(recall its apparent angular size is ~ 0.5°)
Most of the time, the moon is above or below the direct line from Sun to Earth.
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
The Moon’s Orbit is tilted
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Periodically, the Moon crosses the line from Earth to Sun.
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If it does so at full moon, we have a Lunar Eclipse
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The Earth’s shadow falls on the Moon
If it does so at new moon, we have a Solar Eclipse
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The Moon’s shadow Falls on the earth
Astronomy 1 - Elementary Astronomy
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Lunar Eclipse
Path for penumbral eclipse
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Lunar Eclipse
Progression of Total Lunar
Eclipse
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Lunar Eclipses 2010-2017
Astronomy 1 - Elementary Astronomy
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Solar Eclipses
Image: Sanhujinka.com
Astronomy 1 - Elementary Astronomy
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Solar Eclipse
Astronomy 1 - Elementary Astronomy
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A Total Solar Eclipse
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Solar Eclipses
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Next good US TOTAL solar eclipse opportunity is in 2017
Astronomy 1 - Elementary Astronomy
LA Mission College
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Let’s Practice
Suppose it is early in the month and you are going on a cruise to view a total solar eclipse later the same month. The moon is currently full. If it only takes a day or so to get to the viewing location, about when might your cruise depart?
A. tomorrow B. next week C. about two weeks from today D. at the very end of the month Astronomy 1 - Elementary Astronomy
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If you found yourself on a planet very similar to Earth with a moon very similar to our Moon, what would you conclude if you observed a total lunar eclipse every full moon?
A. That this planet’s moon orbits in the same plane as the planet orbits its star. B. That this planet’s moon is much larger than our Moon. C. That this planet’s star is much more distant than our Sun. D. That this planet’s moon orbits over the poles of the planet rather than near its equator. Astronomy 1 - Elementary Astronomy
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Old Dead Guys Greece to Kepler in 10 minutes
Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015
ARCHAEOASTRONOMY
Stonehenge
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Humans have been interested in the sky for a long time
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Built ~ 3000-2000 BC Many other sites built with astronomical alignments
Astronomy 1 - Elementary Astronomy
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ANCIENT GREECE
Contribution of the Ancient Greeks
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Many firsts First preserved written documents about ancient astronomy
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from ancient Greek philosophy
Realized the Earth was round Estimated size of earth and distance to sun First star catalog
Astronomy 1 - Elementary Astronomy
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Limitations of Ancient Greek “Astronomy”
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Models were generally wrong because they were based on philosophical “first principles”, believed to be “obvious” and not questioned
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The Heavens are “perfect and unchangeable”
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Adhered to “perfect” shapes: spheres & circles
The Earth is at the center of the universe and unmoving
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Geocentric
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Limitations of Ancient Greek “Astronomy”
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Aristotle (384-322 BCE)
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55 crystalline spheres
Circles upon circles required to model motions of planets
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epicycles (Hipparchos)
Ptolemy ~450 years after Aristotle, still Geocentric and “perfect”
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Lasted until 16th century AD 80 spheres Epicycle upon epicycle upon epicycle
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NICOLAUS COPERNICUS THE RELUCTANT REVOLUTIONARY
Nicolaus Copernicus
http://www-history.mcs.st-andrews.ac.uk/PictDisplay/Copernicus.html
Astronomy 1 - Elementary Astronomy
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The “Copernican Revolution” •
Heliocentric: The center of the universe near the Sun
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The Moon orbits Earth
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Earth & the planets orbit the Sun
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The daily rotation of the Earth on its axis is responsible for the apparent motion of the stars & the Sun.
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Predicted retrograde motion without need for epicycles
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Didn’t get the timing right
The orbits, however, were still perfect circles
Astronomy 1 - Elementary Astronomy
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Ptolemaic vs Copernican
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Ptolemaic Model vs. Heliocentric
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TYCHO BRAHE, OBSERVER EXTRAORDINAIRE THE MAN WITHOUT A NOSE WHO DIED AN IGNOBLE DEATH (MAYBE)
Tycho Brahe (1546 - 1601)
http://www.humanities.uci.edu/users/vfolkenflik/VRF%20Sources/tycho%20brahe%20large.jpg
Astronomy 1 - Elementary Astronomy
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The Uraniborg
• King Frederik II of Denmark gave funds for Tycho to build an observatory on the Island of Hven.
• First built in 1576 • an international research center...
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100 students and artisans worked here
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(But no telescopes!)
• ... and also his own court (jester and moose included)
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Late Career, Kepler and Endgame
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left Hven in 1597 Relocated to Prague in 1599,
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Imperial Mathemetician among his duties was casting horoscopes
He hired others to assist him, notably Johannes Kepler died in 1601, 11 days after famously refusing to leave a court banquet to relieve himself
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Ruptered bladder? Kidney stones? Mercury poisoning?
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JOHANNES KEPLER, THE WEEDY PRIG WHO GOT IT ALL RIGHT
Johannes Kepler
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1571-1630
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Discovered “Kepler’s Laws of Planetary motion”
German mathematician, astronomer and reluctant astrologer
Astronomy 1 - Elementary Astronomy
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Biographical Notes
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No proverbial silver spoon here! Born prematurely and reputedly sickly as a child, suffered complications from smallpox
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Could not see well
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Father was a mercenary soldier who left home when Johannes was 5
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Mother was an innkeeper’s daughter and an herbalist/ healer who was tried for witchcraft
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Early interest in astronomy
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Observed great comet of 1577 at age 6 with mother Observed lunar eclipse at age 9
Astronomy 1 - Elementary Astronomy
LA Mission College
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Early Career
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Initially interested in (Lutheran) theology,
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Adopted heliocentrism for both scientific and philosophical and theological reasons
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In 1600 he “went where the data was” to Tycho Brahe in Prague
hired to teach mathematics and astronomy at the University of Graz
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Uneasy alliance Upon Tycho’s death in 1601, succeeded to his post as Imperial mathematician and astrologer
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Kepler’s Laws explaining retrograde motion
Astronomy 1 — Elementary Astronomy LA Mission College Spring F2015
Kepler’s Laws
Astronomy 1 - Elementary Astronomy
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Context
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Kepler’s Laws were empirical and described the motion of the (known) planets in our solar system
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Describe, rather than explain also describes comets
Astronomy 1 - Elementary Astronomy
LA Mission College
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The 3 Laws Summarized
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First Law: Planetary orbits are ellipses with the Sun at one focus
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Second Law: Planets are traveling fastest along their orbit when closest to the Sun
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Third Law: Planets farther from the Sun take longer to complete an orbit.
Astronomy 1 - Elementary Astronomy
LA Mission College
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Kepler’s Laws Can Be Generalized
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Kepler’s laws work for Earth satellites Work any time a relatively small (low mass) object orbits a relatively large (high mass) object
Astronomy 1 - Elementary Astronomy
LA Mission College
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Let’s Practice
Kepler’s second law says “a line joining a planet and the Sun sweeps out equal areas in equal amounts of time.” Which of the following statements means nearly the same thing?
A. Planets move the same speed at all points during their orbit of the Sun. B. Planets move fastest when they are moving toward the Sun. C. Planets move faster the closer they are to the Sun.
Astronomy 1 - Elementary Astronomy
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During how many of the portions of the planet’s orbit (A, B, C, or D) would the experience an increase Kepler’s Second Lawplanet – Instructor’s Guide 31 in speed for at least a moment? ADDITIONAL QUESTIONS
The planet in the orbit shown in the drawing at right obeys Kepler’s Laws. Use this drawing to answer the next four questions. 1) According to Kepler’s Second Law, during which one of the portion of the planet’s orbit (B, C, or D), would the planet take the same amount of time as it took for the portion of the orbit identified with letter “A”? If you think all the portions of the orbit take the same amount of time, answer “E”. [B is the correct answer]
A. Only during one of the portions shown. 2) During which part of the planet’s orbit (A, B, C, or D) would the planet move with the greatest speed? [C is the correct answer]
B. During two portions 3) Duringof how the many portions of the planet’s shown. orbit (A, B, C and D) would the planet be speeding up the entire time? a) Only during one of the portions shown. b) During two of the portions shown. c) During three of the portions shown. d) During four of the portions shown. e) None of the above.
C. During three of the portions shown. D. During four of the portions shown.
4) During which of the portions of the planet’s orbit (A, B, C, or D) would the planet experience an increase in speed for at least a moment? a) Only during one of the portions shown. b) During two of the portions shown. c) During three of the portions shown. During four of the portions shown. Elementaryd)Astronomy LA Mission College Levine F2015 e) None of the above.
E. None of the above. Astronomy 1 -
Jupiter takes longer to orbit the Sun than the Earth does. Which of Kepler’s 3 laws describes this?
A. Kepler’s first law (shapes) B. Kepler’s second law (equal areas in equal times) C. Kepler’s third law (period/distance relationship)
Astronomy 1 - Elementary Astronomy
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If the Earth were moved to twice its current distance from the Sun, how would the length of a year be affected?
A. It would be half as long B. It would be the same C. It would be more than twice as long
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Which of the following best describes what would happen if Mercury and Jupiter were to switch places in their orbits about the Sun?
A. Jupiter, the larger planet, would have a shorter orbital period than before. B. Mercury, the smaller planet, would have a shorter orbital period than before. C. Neither of the two planets would have any change in their orbital periods Astronomy 1 - Elementary Astronomy
LA Mission College
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GALILEO GALILEI: FALLING ROCKS, OBSERVATIONS, THE TELESCOPE AND THE INQUISITION
Galileo Galilei
• 1564-1642 • •
Tycho 1546-1601 Kepler 1571-1630
• Greatly improved the
newly telescope, (did NOT invent the telescope!)
• First to report telescope observations of the sky
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Portrait by Domenico Crespi
support the Copernican Model of the Universe
Astronomy 1 - Elementary Astronomy
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Biographical Notes
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Born in Pisa, son of a musician Roman Catholic, considered the priesthood Had 2 daughters and a son (out of wedlock)
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“Galileo’s Daughter” by Dava Sobel
Studied Medicine at Pisa but wound up a Mathematician Contemporary of Kepler, but dismissed his ideas about tides and elliptical orbits Got in trouble with the Inquisition over Heliocentrism
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“It is surely harmful to souls to make it a heresy to believe what is proved.” (Galileo Galilei via Brainyquote.com)
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Herin hangs a fascinating tale, for which we don’t have time... Ultimately recanted and spent the last 10 years of his life under house arrest
Astronomy 1 - Elementary Astronomy
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Galileo
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Galileo is also credited with
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Playing a major role in making science science rather than philosophy (aka the Scientific Revolution)
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"Philosophy is written in this grand book, the universe ... It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures;...." Galileo Galilei in The Assayer
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Demonstrating that two objects fall at the same rate regardless of their mass (if you can neglect air resistance)
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Actual experiment probably apocryphal But illustrative of his approach
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Galileo
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http://www.biography.com/people/galileo-9305220 http://www.history.com/topics/galileo-galilei
Astronomy 1 - Elementary Astronomy
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Galileo’s Observations
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Built telescope in 1609 Published Sidereus Nuncius (Sidereal Messenger) in 1610
• Moon has mountains & valleys. • Heavens are not perfect • Milky way is made up of •
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individual stars.
Stars must be far away…and not on a fixed sphere
Four “planets” orbiting Jupiter. The Earth is not the only “center of revolution”
Subsequent important observations
• The sun had spots. g d • Heavens are not perfect • Venus had phases. •
Venus MUST orbit the Sun
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Galileo’s Observations
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Built telescope in 1609 Published Sidereus Nuncius (Sidereal Messenger) in 1610
• Moon has mountains & valleys. • Heavens are not perfect • Milky way is made up of •
•
•
•
individual stars.
Stars must be far away…and not on a fixed sphere
Four “planets” orbiting Jupiter. The Earth is not the only “center of revolution”
Subsequent important observations
• The sun had spots. • Heavens are not perfect • Venus had phases. •
Venus MUST orbit the Sun
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Galileo’s Observations
• •
Built telescope in 1609 Published Sidereus Nuncius (Sidereal Messenger) in 1610
• Moon has mountains & valleys. • Heavens are not perfect • Milky way is made up of •
•
•
•
individual stars.
Stars must be far away…and not on a fixed sphere
Four “planets” orbiting Jupiter. The Earth is not the only “center of revolution”
Subsequent important observations
• The sun had spots. • Heavens are not perfect • Venus had phases. •
Venus MUST orbit the Sun
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Galileo’s Observations
• •
Built telescope in 1609 Published Sidereus Nuncius (Sidereal Messenger) in 1610
• Moon has mountains & valleys. • Heavens are not perfect • Milky way is made up of •
•
•
•
individual stars.
Stars must be far away…and not on a fixed sphere
Four “planets” orbiting Jupiter. The Earth is not the only “center of revolution”
Subsequent important observations
• The sun had spots. • Heavens are not perfect • Venus had phases. •
Venus MUST orbit the Sun
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
WRAP-UP
Topic for Next Class
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History part II
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Newton Gravity
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Tides
Intro to light
Astronomy 1 - Elementary Astronomy
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Reading Assignment
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Ch 3&4 in Astro Ch 3,4&10 in the Astropedia
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Homework
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No new HW yet
Astronomy 1 - Elementary Astronomy
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