ch 23
TRANSCRIPT
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Ch 23Ch 23 Section ISection I
The EarthThe Earth
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Properties of the EarthProperties of the Earth
people used to think that Earth was flat people used to think that Earth was flat and at the centre of the universeand at the centre of the universe
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Earth is a round 3-dimensional Earth is a round 3-dimensional spheresphere
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Proof the Earth is roundProof the Earth is round
Aristotle saw a curved Aristotle saw a curved shadow on moon shadow on moon during an eclipseduring an eclipse
See top of ship sails See top of ship sails firstfirst
Sailors noticed Sailors noticed different stars in the different stars in the night skynight sky
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Axis – imaginary vertical line Axis – imaginary vertical line around which earth spinsaround which earth spins
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Rotation – the spinning of Earth Rotation – the spinning of Earth around its axis that causes day and around its axis that causes day and
nightnight
Takes 24 hrs. or 1 day
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Earth has a magnetic field with Earth has a magnetic field with north and south polesnorth and south poles
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Caused by: Caused by: 1- the movement of material in core 1- the movement of material in core 2- Earth’s rotation2- Earth’s rotationProtects us from harmful solar radiation by Protects us from harmful solar radiation by
trapping charged particlestrapping charged particles
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Magnetic north vs. geographic Magnetic north vs. geographic northnorth
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Revolution – Earth’s yearly orbit Revolution – Earth’s yearly orbit around the sunaround the sun
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Revolution vs. rotationRevolution vs. rotation
Revolution – trip around SunRevolution – trip around SunEarth orbits around the SunEarth orbits around the SunEarth is a satellite of the SunEarth is a satellite of the Sun
Rotation – spinning on axisRotation – spinning on axisCause of night/dayCause of night/day
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Earth’s orbit is an Earth’s orbit is an ellipseellipse or or elongated, closed curveelongated, closed curve
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The Sun is not centered in the ellipseThe Sun is not centered in the ellipse PerihelionPerihelion: closest point (winter): closest point (winter)AphelionAphelion: furthest point (summer): furthest point (summer)
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Distance from SunDistance from Sun
Earth closest Jan. 3:Earth closest Jan. 3:147 million kilometers147 million kilometers
Earth furthest July 4:Earth furthest July 4:152 million kilometers152 million kilometers
Small difference 5 million kilometers so…Small difference 5 million kilometers so…Earth is exposed to almost the same amount Earth is exposed to almost the same amount
of Sun year roundof Sun year round
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Earth’s tilt causes the seasonsEarth’s tilt causes the seasons
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Tilt causes radiation to strike at different Tilt causes radiation to strike at different angles angles
The more direct the angles receive more The more direct the angles receive more radiationradiation
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Seasons on EarthSeasons on Earth
The height of the sun above the horizon The height of the sun above the horizon varies with the season.varies with the season.
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SolsticeSolstice the day when the sun the day when the sun
reaches its greatest distance reaches its greatest distance north or south of the equatornorth or south of the equator
Summer solstice: June 21 or Summer solstice: June 21 or 22 in northern hemisphere22 in northern hemisphere Sun directly over Tropic of Sun directly over Tropic of
CancerCancer
Winter solstice: December Winter solstice: December 21 or 22 in northern 21 or 22 in northern hemispherehemisphere Sun directly over Tropic of Sun directly over Tropic of
CapricornCapricorn
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EquinoxEquinox the day when the sun is the day when the sun is directly over Earth’s equatordirectly over Earth’s equator
Daytime and nighttime hours Daytime and nighttime hours are equal all over the worldare equal all over the world
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Vernal (Spring) equinox: March 20 or 21 in Vernal (Spring) equinox: March 20 or 21 in northern hemispherenorthern hemisphere
Autumnal (Fall) equinox: September 22 or 23 in Autumnal (Fall) equinox: September 22 or 23 in northern hemispherenorthern hemisphere
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Geocentric – everything revolves around earth
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Heliocentric – everything revolves around the sun
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MoonMoon
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Motions of the moonMotions of the moon rotatesrotates on its axis on its axis takes 27.3 days for one takes 27.3 days for one revolutionrevolutionAlways the same side facing earth b/c Always the same side facing earth b/c
moon rotates and revolves at the same moon rotates and revolves at the same speedspeed
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The moon seems to shine because The moon seems to shine because it reflects sunlightit reflects sunlight
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Games/activitiesGames/activities
http://www.sciencenetlinks.com/http://www.sciencenetlinks.com/interactives/moon/moon_challenge/interactives/moon/moon_challenge/moon_challenge.htmlmoon_challenge.html
http://www.engagingscience.org/games/http://www.engagingscience.org/games/onlinegames/games.htmlonlinegames/games.html
http://aspire.cosmic-ray.org/labs/moon/http://aspire.cosmic-ray.org/labs/moon/lunar_phases_main.htmllunar_phases_main.html
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Moon Phases – the different forms Moon Phases – the different forms the Moon takes in its appearance the Moon takes in its appearance
from Earthfrom Earth
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New Moon – when the moon is New Moon – when the moon is between earth and the sun and between earth and the sun and
cannot be seencannot be seen
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Waxing phasesWaxing phases
more of the illuminated half of the moon more of the illuminated half of the moon that can be seen each night after the new that can be seen each night after the new moonmoon
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First visible thin slice of the moon is First visible thin slice of the moon is a a waxing crescentwaxing crescent
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First quarter phase First quarter phase – half the lit side of the – half the lit side of the moon is visiblemoon is visible
Waxing gibbous Waxing gibbous – more than one quarter – more than one quarter is visibleis visible
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All of the Moon’s lit side is visible All of the Moon’s lit side is visible during a full moonduring a full moon
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Waning phases Waning phases – less of the – less of the illuminated half of the Moon is illuminated half of the Moon is
visible after the full moon.visible after the full moon.
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Waning gibbous Waning gibbous – starts after a full moon – starts after a full moon where more than half of the lit side is still where more than half of the lit side is still visible.visible.
Third quarter Third quarter - half the Moon’s lit side is - half the Moon’s lit side is visible visible
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The last visible slice before a new The last visible slice before a new moon is called the moon is called the waning crescentwaning crescent
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Phases of the Moon
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What time period did we get from studying the moon?
Completes its moon cycle in 29.5 daysCompletes revolution in 27.3 days
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The moon’s orbit is tilted about 5 degrees relative to Earth’s orbit around the sun.
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visualsvisuals
http://www.ioncmaste.ca/homepage/http://www.ioncmaste.ca/homepage/resources/web_resources/CSA_Astro9/resources/web_resources/CSA_Astro9/files/multimedia/unit3/phases_moon/files/multimedia/unit3/phases_moon/phases_moon.htmlphases_moon.html
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Eclipses – when the Earth or the Eclipses – when the Earth or the moon casts a shadow on the othermoon casts a shadow on the other
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Solar EclipseSolar Eclipse the moon moves directly the moon moves directly between the Earth and the between the Earth and the Sun, shadowing part of the Sun, shadowing part of the EarthEarth
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Penumbra – experiences a partial eclipseUmbra – experiences a total eclipse
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A total solar eclipse is visible only A total solar eclipse is visible only on a small area of Earthon a small area of Earth
The corona is the silvery part
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Lunar Eclipse – when Earth’s Lunar Eclipse – when Earth’s shadow falls on the moonshadow falls on the moon
What color does the moon turn during as eclipse?
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Does not occur every month because the moon’s orbit is tilted to earth’s orbit.
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NASA - Total Lunar Eclipse: February 20, 2008
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The moon is 3,476 km in diameter, a little less than the distance across the
contiguous United States.
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Moon’s gravity is 1/6 of Earth’s gravity
because it is less massive
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The Moon’s surface has many The Moon’s surface has many depressions, or craters. formed depressions, or craters. formed from meteorites, asteroids, and from meteorites, asteroids, and
cometscomets
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What could destroy the footprint?
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Cracks in the Moon’s crust caused Cracks in the Moon’s crust caused lava to fill large craters, forming lava to fill large craters, forming
maria, or dark, flat areasmaria, or dark, flat areas
Mountainous area calledhighlands
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http://stardate.org/pdfs/teachers/ObservingTheMoon.pdf
Shows marias
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Regolith is the broken rock material on the moon’s surface.
Moon rocks are similar to ours and have tiny crystals of pure iron.
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Data from moonquakes suggest Data from moonquakes suggest that under the Moon’s crust might that under the Moon’s crust might
lie a solid mantle, then a partly lie a solid mantle, then a partly molten mantle and a solid, iron rich, molten mantle and a solid, iron rich,
core.core.
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Impact Theory of Moon OriginImpact Theory of Moon Origin
the Moon formed 4.6 billion years ago the Moon formed 4.6 billion years ago from Earth material thrown off when a from Earth material thrown off when a large object collided with Earthlarge object collided with Earth
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Impact BasinsImpact Basins or craters, are or craters, are depressions left by depressions left by objects striking the Moon objects striking the Moon (or anything else!!!!!)(or anything else!!!!!)
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Arizona Crater
20,000-50,000 years agoAsteroid 80 feet in diameter1.2 kilometers in diameter
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Chicxulub, Mexico
Now covered by the Yucatan Penninsula
Asteroid 6 mi (10 km) Crater diameter 110
miles (180 km) 65 million years ago Cretaceous period
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Albedoreflectance
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Albedo of 0
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Albedo of 1
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Clementine
January 25, 1994 Objective to test
lightweight sensors Task was to map the
surface of the moon Cost 80 million Bet. 2/26 – 4/22 1.8
million images Carried cameras –
infrared to ultraviolet
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Clementine
Northside
Farside
Nearside
Southside
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Clementine
3 billion metric tons at poles
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Lunar Prospector
Desk sized 1998 Confirmed impact
theory
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Graphic Organizer
rotates revolves
causing causing
Earth
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Graphic Organizer
rotates revolves
causing causing
Earth
On its axis
Night and day
Around the Sun
years