2Review QuestionPeople once believed that all planets and stars orbited around ____.MercuryEarthVenusMars
3The Rotating Earth is a sphere, a round 3-dimensional shape bulges slightly at equator and flattens slightly at polesRadius: same from all points on the surfaceAxis/Tilt: imaginary vertical line through the north and south poles it spins on
4What is Earth’s rotation? Rotation: spinning of earth on its axis, causes days and nightsOne complete rotation in 24 hourscompletes 365 rotations in a one year journey around the Sunrotates from west to east
5What is a Foucault pendulum? Weight on a string suspended from a support and swings freely.Swings in a constant direct but as earth turns it appears the pendulum shifts orientation.
6Earths RotationCompass always points north is evidence of earth’s magnetic fieldEarth’s magnetic axis and rotational axis are not at the same pointsThus, your compass would take you to magnetic north not the north poleMagnetic north changes and moves around rotational north
7What is the Coriollis Effect? rotation of Earth causes ocean currents and wind belts to curve to the left or right
8What is Earths Revolution? Revolution- the motion of a body that travels around another body in space; one complete trip along an orbita satellite of SunEarth’s orbit around the Sun is an Ellipse, an elongated closed curveis traveling around the sun at an average speed of 29.8 km/s.Aphelion: planet is farthest from the sunPerihelion: planet is closest to the sun.
9What causes the changes in seasons ? is tilted 23.5°causes our change in seasonsmakes daylight longer in summer and shorter in winterhemisphere tilted toward the Sun has longer hours of daylight and makes summer warmer
11What is an Equinox?Equinox: occurs when the Sun is directly over the equator; causing spring and fallTHINK EQUAL: Hours of daylight and nighttimeSpring equinox is Mar 21 and Fall equinox Sep 22
12What is a Solstice?hemisphere tilted toward the Sun receives and absorbs more solar radiation; causing summerSolstice: is the day when the Sun rays are at its greatest/least distance from the equatorJune 21:longest daylightDec 21: shortest daylight
16The Moon: Properties, history, phases, eclipses, and tides
17What is the moon? A natural satellite Satellite: a natural or artificial body that revolves around planet.One of more than 96 moons in our Solar SystemThe only moon of the planet Earth
18What is the moons Distance, Size, and Gravity? About 384,000 km (240,000 miles) from Earth3,468 km (2,155 miles) in diameter (about ¼ the size of Earth)1/6 of Earths gravity
19What is the moons internal structure? 3 major divisions of the Lunar interiorCrust - average thickness of about 70 kilometersMantleCore - radius is between 300 and 425 kilometersDetermined via seismic data from “moonquakes”
20What are some lunar features? No atmosphereNo liquid waterExtreme temperaturesDaytime = 130C (265°F)Nighttime = -190C (-310 F)
21Lunar Features – Highlands (Terrae) Mountains up to 7500 m (25,000 ft) tallRilles (trenchlike valleys)Anorthosite: light patches seen on the moon’s surface
22Lunar Features - Craters a bowl-shaped depression that forms on the surface of an object when a falling body strikes the object’s surface or when an explosion occurs]Up to 2500 km (1,553 miles) acrossMost formed by meteorite impact on the MoonSome formed by volcanic action inside the Moon
25Lunar Features - MariaOriginally thought to be “seas” by early astronomersDarkest parts of lunar landscapeFilled by lava after crash of huge meteorites on lunar surface 3-4 billion years agoMostly basalt rock
28What is the moons rotation and revolution? Revolution – Moon orbits the Earth every 29.5daysThe moon rises in the east and sets in the westThe moon rises and sets 50 minutes later each dayRotation – Moon turns on its axis every 29 daysSame side of Moon always faces usarth
29What shape is the moons orbit around the sun? The orbit of the moon around Earth forms an ellipse, the distance between Earth and the moon varies over a month’s time
30Apparent SizeThe illustration, based on Galileo spacecraft images, shows the approximate difference in apparent size between a full moon at perigee (the closest point in the lunar orbit, pictured at left) and a full moon at apogee, the farthest point in the lunar orbit.
31The near side The Moon rotates in 29.5 days. The Moon orbits Earth in 29.5 days.Because the Moon rotates and revolves at the same rate, we only see one sideThe NEAR sideThere is NO DARK SIDEThere is a FAR side….
33How was the moon formed? 3 major theories 1. Capture theory: large object ventured too near the forming earth and got trapped by gravity2. Simultaneous formation theory: Earth and moon formed at the same time.3. Impact theory: Most widely accepted.
34How was the moon formed? The Giant Impact Hypothesis 3 stages 1. began when a large object collided with Earth more than 4 billion years ago2. collision ejected chunks of Earth’s mantle into orbit around Earth3. debris eventually clumped together to form the moon.
36What are phases?Phase: in astronomy, the change in the illuminated area of one celestial body as seen from another celestial body; are caused by the changing positions of Earth, the sun, and the moon
38Why are their phases of the moon? Moonlight is reflected sunlightHalf the moon’s surface is always reflecting lightFrom Earth we see different amounts of the Moon’s lit surfaceThe amount seen is called a “phase”Synchronous rotation: orbital and rotational periods are equal.
45Review questionWhen only a small part of the moon is visible, the moon may be in itsfirst-quarter phasewaning-crescent phasenew moon phaselast-quarter phase
46Why don’t we have eclipses every month? MOON – SUN – EARTH: All do not travel in the same plane of orbit
47What are eclipses?an event in which the shadow of one celestial body falls on anotherBodies orbiting the sun cast long shadows into space
48What is the shadow structure for an eclipse? UMBRA (Latin for "shadow")is the darkest part of the shadowPenumbraUmbraPENUMBRA is a partial shadow,grayish outer part of a sunspot
49What is a solar eclipse?A solar eclipse is when the moon comes between the sun and the Earth, so that a viewer is in the moon's shadow.Total eclipses rare – only once every 360 years from one location!
50How do I see a total solar eclipse? Observers in the “umbra” shadow see a total eclipse (safe to view the Sun); can see the coronaThose in “penumbra” see a partial eclipse—not safe to look directly at SunOnly lasts a few minutesPath of Totality about 10,000 miles long, only 100 miles wide
55Why not a solar eclipse every month then? Moon's orbit is tilted about 5o with respect to the Earth's orbit (ecliptic), so the shadows usually miss!MoonEarthEclipticMoon’s Orbit
56What is a lunar eclipse?the passing of the moon through Earth’s shadow at full moonoccurs when Earth is positioned between the moon and the sun and when Earth’s shadow crosses the lighted half of the moon
59Why is the Moon red during an eclipse? The Earth’s atmosphere filters some sunlight and allows it to reach the Moon’s surfaceThe blue light is removed—scattered down to make a blue sky over those in daytimeRemaining light is red or orangeSome of this remaining light is bent or refracted so that a small fraction of it reaches the MoonExact appearance depends on dust and clouds in the Earth’s atmosphere
60What causes the tides?Tides: daily changes in the level of ocean waterinfluenced by the sun and the moonoccur in a variety of cyclesThe combination of gravity and inertia create two bulges of water.High Tide and Low Tide: How often tides occur and the difference in tidal levels depend on the position of the moon as it revolves around the Earth
61What causes the tides?The gravitational attraction between the Earth and the moon is strongest on the side of the Earth that happens to be facing the moon, simply because it is closer.This attraction causes the water on this “near side” of Earth to be pulled toward the moon.As gravitational force acts to draw the water closer to the moon, inertial force attempts to keep the water in place.But the gravitational force exceeds it and the water is pulled toward the moon, causing a “bulge” of water on the near side toward the moon
62On the opposite side of the Earth, or the “far side,” the gravitational attraction of the moon is less because it is farther away.Here, the inertial force exceeds the gravitational force, and the water tries to keep going in a straight line, moving away from the Earth, also forming a bulge
64Approximately how many days does it take the moon to go through a complete cycle? A. 7 B. 11 C. 26 D ow many days does it take the moon to go through a complete cycle?
65When the visible portion of the moon is increasing, the moon is A. waxing B. full C. waning D. waning-crescent
66A solar eclipse is most likely to occur when the sun is located between the earth and moonmoon is located between the sun and the earthearth is located between the sun and the moonearth and moon are at right angles to each other
67Earth has seasons because the temperature of the sun changesEarth rotates on its axisEarth's axis is tilted as it moves around the sunthe distance between Earth and the sun changes
68The sun appears larger than other stars because it is the biggest star in the universeit is a double starit is the closest star to the earth
69A lunar eclipse is most likely to occur when sun is located between the earth and moonmoon is located between the sun and the earthearth is located between the sun and the moonearth and moon are at right angles to each other
70From new moon to full moon phase you see a decreasing amount of the lighted side of the moonan increasing amount of the lighted side of the moonmore of the lighted side, then less of the lighted side of the moonthe same amount of the lighted side of the moon
71During what moon phase can a lunar eclipse occur? waxing gibbousfirst quarternew moonfull moon