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Earth Moon and Sun Ch. 12 I. Motion of the Earth and Moon • The Earth, Moon and all other bodies in the solar system are in constant motion. All objects can have 2 types of motion: 1. Rotation: spinning on its axis – Causes day and night – Earth: 24 hour period of rotation – Moon: 28 day period of rotation 2. Revolution: traveling around another body (like planets around the sun or moons around their planets) –Objects in our solar system travel in elliptical orbits (or paths) around other objects –Earth: 365 1/4 day period of revolution –Moon 28 day period of revolution 3. Objects in our solar system typically revolve in paths called orbits. 4. Most orbits in our solar system are shaped like an elongated circle, this shape is called an ellipse How to draw an ellipse: How to draw an ellipse: II. Gravity and Motion 1. Gravity is the force that attracts all objects toward each other – Universal Law of Gravitation: Newton realized that all objects ( even the moon and planets) have to follow the law all through the universe A. Gravity depends on mass and distance • Gravity and Mass: a bigger mass has more gravity • Weight: the force of gravity on an object is the object’s weight • Gravity and Distance: the force of gravity decreases rapidly as distance increases B. We do not feel the effect of Universal Gravitation because the Earth is so massive and we are so close to it. The Earth’s gravity “wins” over all other gravitational forces on Earth. 2. Orbital motion: the motion of bodies in orbit is caused by a combination of two factors: gravity: pulling downward inertia: moving in a straight line III. Phases and Eclipses • The revolution of the Earth around the sun and the Moon around the Earth causes moon phases and eclipses 1. Moon Phases: the different shapes of the moon as you see from Earth all bodies in our solar system are lighted on the side that faces the sun and dark on the side that faces away The phase of the moon you see depends on the fraction of the lighted side that you can see. FIVE MAIN SHAPES QUARTER NEW CRESCENT FULL GIBBOUS Five Main Moon Shapes • New: none of the lighted half is visible • Crescent: any amount between new and quarter • Quarter: half of the lighted half is visible • Gibbous: any amount more than a quarter and less than full • Full: all of the lighted half is visible 1st QTR Waxing Gibbous Waxing Crescent Dusk New Moon Midnight Earth Noon Full Moon Dawn Waning Gibbous Waning Crescent 3rd QTR SU NLI GH T Waxing and Waning • The moon gets “light from the right” • Waxing: the moon is getting “bigger” or more of the lighted area is visible each night. The right side is lit up. • Waning: the moon is getting “smaller” or less of the lighted area is visible each night. The left side is lit up. Moon Phases • • • • • • • • 1. new moon 2. waxing crescent 3. first quarter 4. waxing gibbous 5. full moon 6. waning gibbous 7. 3rd (or last) quarter 8. waning crescent Phases of the Moon 2. Eclipses: an eclipse occurs when the shadow of one body falls on another Lunar Eclipse: When the shadow of the Earth falls on the Moon. Lunar Eclipse • The shadow darkens the Moon and turns it red because of light bending through the atmosphere (just like a sunset) • About 2-3 per year • Last up to 4 hours Solar Eclipse: When the shadow of the Moon falls on the Earth. Solar Eclipse • Occurs every 1 to 2 years • Last from 2-10 minutes • Can only be seen in a narrow path of totality Future Total Solar Eclipses Our Moon: The far side The near side Size About ¼ the Earth’s diameter Features: Craters Can you see the rays? Maria Does this photo show us a limb or terminator line? Name this phase! Full Moon What time does this phase rise and set? Craters Name these features. Maria Name these features. Does this image show us the near side or far side of the moon? Far Side How can you tell? Is this line the limb or terminator? Limb Terminator Is this line the limb or terminator? Name this phase! First Quarter Name this phase! Waxing Crescent Does this image show the near side or the far side of the moon? Near Side Name this phase! Waning Gibbous Name this phase! Third Quarter From what direction does the moon rise? The East Name this phase! Waxing Gibbous Name this phase! Waning Crescent What might be happening in this image? Lunar Eclipse Is this line the limb or the terminator? Limb Name this phase! Look closely! Waxing Gibbous True or False: The Far Side and the Dark Side of the moon are the same thing. False! Name this phase! Full Moon Name this phase! New Moon Does the moon rise or set in the west? It sets in the west. Name this phase! Waning Gibbous Name this phase! Waning Crescent Name this phase! Waning Gibbous