Download Eclipses Old Dead Guys Part I Astronomy 1 — Elementary Astronomy

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
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
This Class
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Eclipses (if not done Monday)
History Ancients-Galileo
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
Lunar Eclipse
Path for penumbral
eclipse
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Lunar Eclipse
Progression of Total Lunar
Eclipse
<----------
Partial Lunar Eclipse
---------->
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Lunar Eclipses 2010-2017
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Solar Eclipses
Image: Sanhujinka.com
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Solar Eclipse
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
A Total Solar Eclipse
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Solar Eclipses
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Next good US TOTAL solar eclipse opportunity is in
2017
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
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
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
NICOLAUS COPERNICUS
THE RELUCTANT REVOLUTIONARY
Nicolaus Copernicus
http://www-history.mcs.st-andrews.ac.uk/PictDisplay/Copernicus.html
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
The “Copernican Revolution”
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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
LA Mission College
Levine F2015
Ptolemaic vs Copernican
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Ptolemaic Model vs. Heliocentric
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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)
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
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?
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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
Levine F2015
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
LA Mission College
Levine F2015
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
Levine F2015
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
Levine F2015
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
Levine F2015
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
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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
Levine F2015
GALILEO GALILEI: FALLING ROCKS,
OBSERVATIONS, THE TELESCOPE AND THE
INQUISITION
Galileo Galilei
• 1564-1642
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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
LA Mission College
Levine F2015
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
LA Mission College
Levine F2015
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
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Galileo
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http://www.biography.com/people/galileo-9305220
http://www.history.com/topics/galileo-galilei
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
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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.
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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
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
LA Mission College
Levine F2015
Reading Assignment
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Ch 3&4 in Astro
Ch 3,4&10 in the Astropedia
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015
Homework
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No new HW yet
Astronomy 1 - Elementary Astronomy
LA Mission College
Levine F2015