Earth and Its Moon
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Transcript of Earth and Its Moon
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Earth and Its MoonChapter 3
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3-1 The Earth in Space
Earth rotates on its axis Axis = imaginary line from North Pole
to South Pole 2 movements of the Earth affect the
seasons and both day & night1. Rotation2. Revolution
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Day and Night Equator = imaginary line dividing
Earth into the Northern Hemisphere and Southern Hemisphere
Earth rotates abt 1600 km/hr 24 hours to rotate 1 time on its axis =
1 day Part of Earth faces the sun; other part
away from sun in darkness Day and night is caused by the rotation
of Earth on its axis
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Looking down on Earth from North Pole see that rotates in a counterclockwise direction West to East Sun rises in East as Earth turns toward it Sun sets in West as Earth turns away from it
Earth’s day is not constant Changes b/c Earth’s axis is tilted at a 23½°
angle and is not straight up and down If axis were straight
daylight = 12 hrs and nighttime = 12 hrs, every day of every year
Tilted axis: when North Pole leans toward sun then South Pole leaning away from sun Daylight hours not constant Hemisphere that leans toward sun has long
days and short night Hemisphere leaning away from sun has short
days and long nights
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A Year on Earth Earth takes 365.25 days to revolve 1
time around the sun = 1 year Extra ¼ day is left off calendar and
added every 4 years to the month of February
What is a year with an extra day called?
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Seasons on Earth 4 seasons: Spring, Summer, Autumn,
Winter Mars, Saturn, Uranus, & Neptune all
have seasons while other 3 have little to no seasons
Why do some planets have seasons and other do not?
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Planets have seasons because they are tilted on their axis
Different seasons on Earth caused by tilt of Earth’s axis
When hemisphere is tilting toward sun it’s summer and tilting away from sun it’s winter
Hemisphere tilting toward sun receives more direct rays from sun and have longer days Combination of these results in Earths
surface and atmosphere receiving more heat = summer
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Summer in Northern Hemisphere begins June 20 & 21 Northern Hemisphere tilted full 23½°
toward sun Northern Hemisphere has longest day Southern Hemisphere has shortest day
Summer Solstice = longest day of year Solstice – Latin meaning sun and stop
Sun reaches its highest point in the sky on the summer solstice
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After summer solstice sun begins to lower in the sky
December 21 & 22 = Winter Solstice Northern Hemisphere tilted full 23½°
away from sun Shortest day of year in Northern
Hemisphere Longest day of year in Southern
Hemisphere
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Equinoxes- 2 times a year when poles are not tilted toward the sun (Spring & Autumn) Latin for equal night Day and night are of equal length all
over the world Vernal Equinox – in Northern
Hemisphere spring begins March 20 or 21
Autumnal Equinox – begins Sept. 22 or 23
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A Magnet in Space Magnet Field – invisible lines of force
that connect the poles/ends of a magnet Earth similar to a magnet Earth has a magnetic field that forms
around it Comes from the movement of materials in the
Earth’s inner core Metals such as Iron and Nickel
Magnetic poles different from geographic poles
Geographic poles - opposite ends of tilted axis Magnetic poles – ends of lines of force that form
the Earth’s magnetic field
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Magnetosphere – Earth’s magnetic field Begins at abt 1000km and extends to
abt. 64000km on the side facing the sun On side away from sun is a tail that
extends millions of km long caused by a stream of charged particles called the solar wind which continually reshapes the magnetosphere as Earth rotates
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Van Allen radiation belts – 2 doughnut-shaped regions of charged particles formed as the magnetosphere traps particles in the solar wind Outer belt contains mostly negatively charged
electrons Inner belt contains mainly positively charged
protons Charged particles travel along magnetic lines of
force colliding with the Earth’s upper atmosphere Aurora – collisions of atmospheric particles that give off
visible light that appear as bands of shimmering colored lights
Aurora Borealis – a.k.a. “Northern Lights” near North Pole Aurora Australis – a.k.a. “Southern Lights” near South
Pole
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3-2 The Earth’s Moon
Lunar – Latin word for moon Neil Armstrong & Buzz Aldrin first
men to walk on the moon
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The Moon’s Characteristics
Moon – 3476km in diameter ¼ the diameter of Earth Gravity is 1/6 that on Earth (objects weigh
less) Avg. distance to moon = 384,403km
Measured using a mirror left on moon and bounced a beam of light back to Earth
Moonquakes measured using instruments left on the moon (approx. 3000 occur per year
Crust abt. 60km thick Inner layer abt 800km thick (denser rock) Core - melted iron
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Apollo astronauts brought back moon rocks Oldest abt 4.6 billions yrs abt. same as
age of Earth Earth and moon appear to have formed
abt same time Moon rocks show no traces of water Scientist believe moon never has had
water Moon has no atmosphere, therefore no
weather Extreme temperature range 100°C to -
175°C The moon is dry, airless, and
barren.
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Features of the Moon Galileo first person to see the moon
through a telescope Highlands – mountain ranges soaring
thousands of meters into the black sky Maria - broad, smooth lowland plains;
appear as dark areas Latin word for seas
Craters are scattered across moon’s surface Range in size from microscopic to hundreds of
km Copernicus is one of the largest craters on the
moon (91km across) Most craters located in highlands, very few in
the maria
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Craters formed from blasts of meteorites and some from volcanic activity
Maria filled with hardened rock from volcanic activity billions of years ago
Rilles – long valleys that crisscross much of the moon’s surface, Hadley Rille – 113 km long
Scientists unsure what made rilles, some possibilies: Evidence that there were active volcanoes Cut by rivers of flowing lava or Cracks in surface from moonquakes Moon’s hot surface cooling and shrinking
All is evidence that the moon was once hot and active
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Movement of the Moon Earth revolves around sun and at same
time moon revolves around the Earth Perigee – point of the moon’s orbit
closest to the Earth (abt. 350,000 km) Apogee – point of the moon’s orbit
farthest from Earth (abt. 400,000 km) Moon moves west across the sky,
apparent movement caused by Earth’s rotation When viewed amongst the stars, movement of
moon eastward is observed
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Earth rotates on axis 1 time every 24 hrs
Moon rotates 1 time on axis every 27.3 days
Moon revolves 1 time around Earth every 27.3 days Moon’s Period of Rotation = Period of
Revolution Same side of moon always faces the
Earth Apollo 8 astronauts were first humans
to view the dark side of the moon
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Origin of the Moon Moon was “born” when a giant
asteroid the size of Mars struck the young Earth, tearing away a chunk of material The Pacific Ocean possibly could be the
hole what was left Evidence based from moon rocks and
explains why moon is so similar to Earth
Water would have vaporized as it was torn from the Earth
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3-3 The Earth, the Moon, & the
Sun Relative motions of the Earth, the
moon, and the sun result in the changing appearance of the moon as seen from the Earth and the occasional blocking of the sun’s light
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Phases of the Moon Moon revolves around the Earth Moon’s revolution causes moon to
appear to change shape in the sky Different shapes called Phases of the
Moon Goes through all phases in 29.5 days Moon reflects sunlight toward the
Earth, has no light of its own Phase depends on where moon is in
relation to sun and Earth
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New Moon – moon has no visible light, btwn the sun and the Earth Sometimes faintly visible due to
earthshine (sunlight reflected off the Earth)
Waxing Crescent Phase – more of the lighted side of the moon is visible, a slim curved slice appears Moon is “waxing” when lighted area
appears to grow larger Moon is “waning” when lighted area
appears to grow smaller
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First Quarter Moon – moon appears ½ lit 1 week after new moon , moon traveled ¼ the
way around the Earth Waxing Gibbous Phase – days after First
Quarter Phase and more of the lighted side of the Moon appears
Full Moon – 2 wks after New Moon Phase Entire lighted side of moon is visible Earth is btwn the Moon and Sun
2 weeks more and the Moon moves through the Waning-Gibbous, Last Quarter, & Waning-Crescent Phases & back the New Moon Phases
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Eclipses Movement of the Earth, the Sun, and the
Moon lining up in the sky blocking out light or casting shadows
2 types of Eclipses Depends which body is blocked Sun or Moon
Solar Eclipse – new moon comes directly btwn moon’s shadow, sunlight blocked from reaching the Earth Shadow has 2 parts: Umbra and Penumbra Umbra – small, inner shadow Penumbra – larger, outer shadow
Only people directly in the path of the umbra can see a total solar eclipse (sun completely blocked) Never look directly into the sun during a total
solar eclipse
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Why isn’t there a solar eclipse every time there is a new moon?
Lunar Eclipse – Earth comes directly btwn sun and the Full Moon Phase Moon passes through the Earth’s
shadow Total Lunar Eclipse – moon passes
through umbra Partial Lunar Eclipse – moon passes
through penumbra dims moon’s glow to a reddish color when
sunlight is reflected off moon and is bent as it passes through the atmosphere
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Tides Gravitational attraction btwn Moon
and Earth due to closeness Gravitational pull of Earth on moon
results in a bulging of the Moon surface facing the Earth
Moon also exerts gravitational pull on Earth pulling results in the rise and fall of the oceans as the Moon moves around the Earth
Tides – rise and fall of oceans
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2 places on Earth that bulge due to the Moon’s gravitational pull causing high tides: Side of Earth facing the Moon Side of Earth facing away from the
Moon Low Tides occur btwn the bulges 2 high tides and 2 low tides occur
every 24 hrs High and low tides occur abt 50 min.
later each day due to the moon’s risng 50 min. later
Spring Tides – higher than normal during full and new moon phases Due to sun and moon being in direct
line with the Earth and increased effect of sun’s gravity on Earth
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Neap Tides – high tides that are lower that usual Occur during the first and last quarter
phases, gravitational pull on oceans is partially canceled by sun’s gravitational pull
Sun and moon at right angles of the Earth