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Earth In Space Chapter 3 Shape of the Earth Ancient Greeks Earth casts a circular shadow on the moon during a lunar eclipse Shape of the Earth Ancient Greeks Ships were observed to “disappear” below the horizon as they sailed away from the viewer ____________ (276-195 B.C.) Astronomer used geometry to ___________ the ___________ of the _________ Eratosthenes (276-195 B.C.) Sunlight shone straight down a well at Syene, Egypt June 21 Alexandria is 800 km from Syene Eratosthenes (276-195 B.C.) Measured shadow cast by tall obelisk in Alexandria Calculated angle 7° 12’ exactly 1/50 of a circle Eratosthenes (276-195 B.C.) If the angle is 1/50 of a circle Then the distance between Alexandria and Syene must be 1/50th the circumference of the Earth Eratosthenes (276-195 B.C.) 50 x 800 km = 40,000 km Actual distance 40,075 km Earth is an _______ ___________ Earth in Motion Rotation ~1000 mph Revolution Moon around Earth 2300 mph Earth around Sun 66,000 mph Earth in Motion Revolution Solar system around Milky Way 230,000 mph Three Main Movements of the Earth ____________ ____________ ______ on Axis Revolution 1 trip takes ____________ days Earth moves ______ at _________, _________ at __________. Rotation The Earth’s axis maintains an average incline, or ______, on its axis. (______°) Axis points _______ the _______ for _________, then turns ________ for ____________. 3 effects: length of day/night, changing seasons, changing climates with latitude (know this) Earth’s Tilt (KNOW) Full daylight at NP Full darkness at SP Full daylight at SP Full darkness at NP Solstices ________ Solstice the sun is at its ________ point _______ has 24 hour light overhead ______________ of _______________ ____________ directly Solstices __________ Solstice the sun is at its __________ point ________ has 24 hour light overhead _____________ of ______________ ______________ directly Equinoxes ___________ __________ _________ ______ sun’s rays strike the equator almost directly and Earth is illuminated from pole to pole Equinoxes ___________ ___________ __________ ___ ___________ sun’s rays strike the equator almost directly and Earth is illuminated from pole to pole What causes the seasons? Caused by Earth’s _________ length of time sunlight falls on a particular location angle at which sunlight hits a region determines amount of solar energy Seasons in Northern Hemisphere Wobble on Axis _________ is ______ ____________ at 23.5 degrees Wobbles back and forth from 22.1 degrees to 24.5 degrees and back to 22.1 degrees. Caused by ___________ _________ of Sun and Moon on ______________ _________. Evidence of Rotation Observation of other planets rotating Rotating planets are oblate spheroids just like earth Jean Bernard Foucault (1851) ________ ____________ Slowly turns clockwise demonstrates counter-clockwise __________ of the __________ under the swing of the pendulum Pantheon in Paris Pendulum Swing Changes with Latitude North Pole Complete turn every 24 hours Equator No turn at all Rotational Velocity Different latitudes have different speeds _________ rotational ________ at __________ A point at the equator has to go farther than a point in Alabama, so it must go faster Coriolis Effect An __________ _________ of the path of an object that moves within a ___________ coordinate system Coriolis Effect Objects moving __________ from the equator will be moving east _______ than the ground Appear to be forced ________ east Coriolis Effect Objects moving __________ the __________ will be moving __________ than the east-moving ground Appear to be forced farther ________ Coriolis Effect Northern Hemisphere Objects moving north or south will appear to turn to the right (KNOW) Coriolis Effect Southern Hemisphere Objects moving north or south will appear to turn to the left (KNOW) Identifying Your Location on Earth Parallels East and west running circles parallel to the equator Latitude (parallels running east and west)--know Angular distance from equator to parallel measured in degrees Meridians North and south running arcs that intersect at both poles Longitude (arcs running north and south) - know Angular distance from prime meridian east or west measured in degrees _________ Observatory, ________ _______ __________ of the world Longitude _______ Every place on Earth is measured east or west from here Finding a Location New Orleans 30° N, 90° W Subdivisions of angular distance 1° = 60 minutes (60’) one minute = 60 seconds (60”) Other Points of Reference Tropic of ____________ __________ _________ border of the ____________ Northern Solstice Tropic of __________ _________ ___________ border of the ____________ Southern Solstice Other Points of Reference _________ Circle ___________ __________ limit of area where sun does _______ ________ on __________ solstice __________ Circle ____________ ________ limit of area where sun does______ ______ on _________ solstice Measuring Time Sun Time and Clock Time What is “noon”? When the sun crosses the _________ ________, _______ has occurred _______ ______ Noon Whenever noon occurs at a given location (longitude) A.M. = _______ _________ morning hours before sun crosses meridian P.M. = _______ ________ afternoon hours after sun crosses meridian ________ _______ _______ _______ time time from the position of the Sun in the sky the shadow of the gnomon on the sundial Caesar Augustus’ Sundial Rome, Italy Apparent Local Solar Time Changes Nonuniform and fluctuating Reasons Earth moves sometimes faster and sometimes slower in its elliptical orbit around sun Tilt of Earth Apparent Solar Day vs. Sidereal Day _________ _______ Day interval between _______ ____________ ____________ of the celestial meridian by the Sun _______ ____________ Apparent Solar Day vs. Sidereal Day _________ Day interval between ________ _________ _________ of the celestial meridian by a particular ______ time for Earth to rotate on axis (KNOW) sidereal means “_______” ______ hrs ______ min ______ sec Why is the Apparent Solar Day ______? Earth must rotate a little farther to compensate for orbit ______ extra minutes Apparent Solar Day vs Sidereal Day At time 1, the sun and a certain distant star are both overhead. At time 2, the planet has rotated 360° and the distant star is overhead again (1→2 = one sidereal day). But it is not until a little later, at time 3, that the sun is overhead again (1→3 = one solar day). Apparent Solar Day vs Sidereal Day Apparent Solar Day vs Sidereal Day Standard Time Zones Each longitudinal line has a different “measure” of time 360° 24 longitudinal lines = 15° each Moving _____ = ______ 1 hour Moving ______ = ______ 1 hour International Date Line (______ °) Moving __________– __________ day Moving __________ – __________ day What is a Year? __________ Year Interval between two consecutive ___________ equinoxes 365 days, 5 hours, 48 minutes, and 46 seconds 365.24220 mean solar days What is a Year? ________ year time required for the Earth to move around its orbit so the Sun is again in the same position relative to the stars _______ than tropical year by ____ minutes Fixing the Calendar ________ Calendar Julius Caesar (46 B.C.) _____ days per year day year every fourth year (______ year) Year started at Spring Equinox July (after Julius) & August (after Augustus) 366th Fixing the Calendar _________ Calendar (_______ ________) Pope Gregory XIII (1582) Revised Julian calendar off by 11 minutes 14 seconds per year only century years divisible by 400 are leap years the year 2000 is leap year the year 2100 is not a leap year The Moon The Moon 384,000 km from Earth (238,000 miles) Diameter ~3500 km ~2200 miles Revolution 3680 km/hr ~2300 mi/hr The Moon _______ _________ _______-colored __________ gravel or boulders compacted together Density (2.9 g/cm ) meteorite impacts 3 The Moon ________ (“______”) Smooth _____-colored ________ lava rock Density (3.3 g/cm ) 3 The Moon No atmosphere Temperature -300 degrees F (night) 417 deg F (day) 205 deg F (at poles) The Moon _________ is covered with fine, glassy _______ ____________ The Moon Moon’s period of rotation is ________ to one revolution around the Earth always see same side of moon from Earth (KNOW) _______ days Earth-Moon System Moon is about 1/81 the mass of the Earth Large enough to move center of mass away from center of Earth Slightly wavy path around Sun Act as a system Earth-Moon System Moon is > ¼ Earth’s diameter larger in comparison to its planet than any other moon provides just enough light large enough to keep spherical shape Phases of the Moon Results from Sun, Earth, & Moon positions _______ _______ _______ _______ _______ _______ _______ _______ The Rest of the Story Moon Phases ________ _________ The Moon’s __________ side is facing the ___________. Not visible except during solar eclipse __________ ________ The Moon is _____________ than __________ illuminated by direct sunlight __________ of the Moon’s disk that is illuminated is _______________ _________ Quarter ____________ the moon is _________ by direct sunlight ____________ of moon’s disk that is illuminated is ____________ ____________ __________ than __________, but not fully, ______________ ____________ of moon illuminated is _______________ __________ Moon ______________ _____________ on side ____________ Earth ___________ ___________ _________ than ______________, but not fully, ___________ ____________ of moon illuminated is ________________ _________ Quarter ___________ of moon is ____________ ____________ of moon illuminated is _______________ __________ __________ Moon is _________than _________ illuminated ___________ of moon illuminated is __________ Eclipses Earth’s or Moon’s shadow falling on the other body (know this) Uncommon because of 5° incline of Moon to Earth Sun, Moon, and Earth have to be in line Eclipses Any shadow of any body consists of two parts ___________ – region of _________ ___________ ________________ – outer _________ of ___________ _________ Lunar Eclipse Occurs when the Moon passes through some portion of Earth’s shadow. (KNOW) CAN ONLY OCCUR AT ______ ______ Lunar Eclipse Types ________________ ________________ ________________ Penumbral Lunar Eclipse Full moon enters earth’s penumbral shadow Moon dims a little Partial Lunar Eclipse Part of the moon is within Earth’s umbra Moon is partially shadowed ________ ________ Eclipse Moon is completely shadowed by earth ________________ ________________ ________________ No direct light from sun reaches the moon Varies in color Near black Red Copper orange Lunar Eclipse Why does the moon turn RED??? Lunar Eclipse _________ Moon Light from sun is __________(bent) by Earth’s atmosphere and ___________ Lunar Eclipse animation Solar Eclipse Occurs when the Moon passes between the Earth and Sun (KNOW) CAN ONLY HAPPEN AT _______ ______ Next solar eclipse visible from US: August 21, _________ Annular Solar Eclipse Moon covers center of sun, but not its edges Moon is too far away from Earth Tides ________ _______ and _______ of sea level Greatest range = _____ and ______ moon Least range = ________ moons ____ high tides and _____ low tides daily in a coastal location Tides ___________ __________ attracts water and land nearness of moon to Earth makes its gravity twice as effective as Sun’s Tides Side ________ moon ________ tide ________ side Earth is pulled away from from the ocean ______ tide tidal trough Other sides 90 degrees away ______ tide Tides _________ tidal range at ______moon and _______ moon ____________ Tides Gravity of Sun and Moon act on Earth All in line Tides ___________ tidal range at quarter moons __________ Tides Sun and moon are at right angles ______________ ____________ of Moon Tides Greatest Spring Tides Moon is closest to Earth Perigee 28,000 miles closer than Apogee Moon is Full or New Tides Size of Tides also determined by size, shape, and depth of water basin Coastal Regions 3-10 feet Gulf of Mexico Lakes and ponds Bay of Fundy 1 foot too small 50 feet