All about the moon - Seasons Finish Tutorial I-33,...

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Unformatted text preview: Seasons Finish Tutorial I-33, “Seasons I” Prather, pages 91 –96. Seasons Do Tutorials I-34 through I-38, “Seasons II” through “Seasons VI” Ranking Exercises, Seasons #1 -- #5. Chapter 3 Cycles of the Moon The Orbit of the Moon Earth-Moon distance = 240,000 miles (average). Earth = 12 inches, Moon = 3 inches, Distance = ??? The Orbit of the Moon Daily (diurnal) motion of the Moon – just like everything else – Raise in the east, set in the west. The Tidally-Locked Orbit of the Moon The Earth exerts tidal forces (a result of gravity) on the moon’s rocky interior. It is rotating with the same period around its axis as it is orbiting Earth (synchronous orbit). → We always see the same side of the moon facing Earth. → The Orbit of the Moon The Moon is always found within 5° of the ecliptic line, moving west to east. The Orbit of the Moon During one month of west to east orbital motion, the Moon crosses the ecliptic twice. Those points are called nodes. The Orbit of the Moon Two measures of the Moon’s orbital period: Sidereal period Synodic period The Orbit of the Moon • The Moon orbits Earth in a sidereal period of 27.32 days. 27.32 days Moon Earth Fixed direction in space The Orbit of the Moon Fixed direction in space 29.53 days Earth Moon Earth orbits around Sun => Direction toward Sun changes! • The Moon’s synodic period (to reach the same position relative to the sun, i.e., the same lunar phase) is 29.53 days (~ 1 month). Chapter 3 Cycles of the Moon The Phases of the Moon Do Tutorial I-39, “The Motion of the Moon” Lecture Tutorial Document (Blackboard) pages 35, 36. The Phases of the Moon The phases of the Moon, of order (consider each of the phase names to be in red ink): Know these phases in order!! The Phases of the Moon These phases are called the quarter phases. They last about 4 hours. The Phases of the Moon These phases are called the intermediate phases or the interphases. They last about one week. The Phases of the Moon From Earth, we see different portions of the Moon’s surface lit by the sun, causing the phases of the Moon. The Phases of the Moon Evening Sky New Moon → First Quarter → Full Moon The Phases of the Moon Morning Sky Full Moon → Third Quarter → New Moon The Phases of the Moon Do Tutorial I-40, “The Cause of Moon Phases” Prather, pages 79 – 81. Chapter 3 Cycles of the Moon The Phases of the Moon Do Tutorial I-41, “Predicting Moon Phases” Prather, pages 83 – 85. The Phases of the Moon Do Tutorial I-42, “Lunar Phases III” Lecture-Tutorial Blackboard Document, pages 38, 39. The Phases of the Moon Do Tutorial I-43 to I-47, “Lunar Phases IV” to “Lunar Phases VII” Ranking Tasks, “Phases of the Moon” Exercises #1 – #5. Chapter 3 Cycles of the Moon The Phases of the Moon Do Tutorial I-43 to I-47, “Lunar Phases IV” to “Lunar Phases VII” Ranking Tasks, “Phases of the Moon” Exercises #1 – #5. Finish this!! 15 Minutes. Angles and Measure We can measure the apparent size of an object in terms of angles. The angular diameter depends on the object’s linear (true) size and the distance from the observer. Angles and Measure Q: Because the Sun and Moon have the same angular size, A) the ratio of the Sun’s and the Moon’s linear size, equals the ratio of their distance. B) they have the same linear size. C) they are at the same distance. D) the ratio of the Sun’s linear size and distance, equals the ratio of the Moon’s linear size and distance. Shadows If a light source is extended (like a large light bulb), any object casts a shadow that consists of a zone of partial shadow, the Penumbra, and a zone of full shadow, the Umbra. Shadows Do Tutorial I-48, “Shadows and Angles” Lecture-Tutorial Blackboard Document, pages 41, 42. Eclipses Lunar eclipse => Moon disappears. Solar eclipse => Sun disappears. Lunar Eclipses Also Earth’s shadow consists of a zone of partial shadow, the Penumbra, and a zone of full shadow, the Umbra. If the Moon passes through Earth’s shadow, we see a lunar eclipse. Lunar Eclipses If the Moon passes completely through the umbra (as shown here), we see a total lunar eclipse. Lunar Eclipses If the Moon passes only partly through the umbra, we see a partial lunar eclipse. Lunar Eclipses If the Moon passes through only the penumbral part of the shadow, we see a penumbral lunar eclipse. A Total Lunar Eclipse During a total eclipse, the moon has a faint, red glow, reflecting sun light scattered in the Earth’s atmosphere. A Total Lunar Eclipse A Total Lunar Eclipse 1 = 1st contact – the eclipse begins. (~1 hour) 2 = 2nd contact – totality begins. (~1 min – 1 hour) 3 = 3rd contact – totality ends. (~1 hour) 4 = 4th contact – the eclipse ends. (Ignore P1 and P2.) Lunar Eclipses: 2006-2012 Typically, 1 or 2 lunar eclipses per year. Lunar Eclipses Conditions to observe a total lunar eclipse: 1) Must be a full Moon. 2) The Moon must pass into the Earth’s shadow (eclipse season). 3) The observer must be on the dark side of the Earth (night). Lunar Eclipses Do Tutorial I-49, “Shadows and Angles” Lecture-Tutorial Blackboard Document, page 43. Chapter 3 Cycles of the Moon Eclipses Lunar eclipse => Moon disappears. Solar eclipse => Sun disappears. Lunar Eclipses Do Tutorial I-49, “Lunar Eclipses” Lecture-Tutorial Blackboard Document, page 43. Solar Eclipses The sun appears approx. as large in the sky (same angular diameter ~ 0.50) as the moon. → When the moon passes in front of the sun, the moon can cover the sun completely, causing a total solar eclipse. Solar Eclipses: 2006-2016 Approximately 1 total solar eclipse per year Solar Eclipses Earth and Moon’s Orbits Are Slightly Elliptical Apogee = position furthest away from Earth Perihelion = position closest to the sun Earth Perigee = position closest to Earth Moon Sun (Eccentricities greatly exaggerated!) Aphelion = position furthest away from the sun Annular Solar Eclipses When Earth is near perihelion, and the moon is near apogee, we see an annular solar eclipse. Perigee Apogee Perihelion Aphelion The angular sizes of the moon and the sun vary, depending on their distance from Earth. Solar Eclipses Three conditions to view solar solar eclipse. 1) Must be new moon. 2) Moon must be near a node. 3) Observer must be in path of totality. Solar Eclipses Do Tutorial I-50, “Solar Eclipses” Lecture-Tutorial Blackboard Document, page 44. Chapter 3 Cycles of the Moon Conditions for Eclipses The moon’s orbit is inclined against the ecliptic by ~ 50. A solar eclipse can only occur if the moon passes a node near new moon. A lunar eclipse can only occur if the moon passes a node near full moon. Eclipse Seasons Strawberry Season – Favorable for strawberries. Winter season – Favorable for snow. Eclipse season – Favorable for eclipses. Conditions for Eclipses Eclipses occur in a cyclic pattern. → Saros cycle: 18 years, 11 days, 8 hours Eclipse Seasons Typically: •Two eclipse seasons per calendar year. •Two solar eclipses per year. •70 total solar eclipses per century. •Three lunar eclipses every two years. The Saros Cycle Eclipse Seasons The Saros cycle is a (very close) repetition of eclipses. One Saros cycle is about 18 years. Can be used to predict future eclipses. Eclipse Seasons Do Tutorial I-51, “Eclipse Seasons” Lecture-Tutorial Blackboard Document, pages 46, 47. ...
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This note was uploaded on 01/31/2010 for the course AS 103 taught by Professor Millar during the Fall '08 term at Grand Rapids Community College.

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