ch 23

Ch 23Ch 23 Section ISection I

The EarthThe Earth

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

Earth is a round 3-dimensional Earth is a round 3-dimensional spheresphere

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

Axis – imaginary vertical line Axis – imaginary vertical line around which earth spinsaround which earth spins

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

Earth has a magnetic field with Earth has a magnetic field with north and south polesnorth and south poles

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

Magnetic north vs. geographic Magnetic north vs. geographic northnorth

Revolution – Earth’s yearly orbit Revolution – Earth’s yearly orbit around the sunaround the sun

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

Earth’s orbit is an Earth’s orbit is an ellipseellipse or or elongated, closed curveelongated, closed curve

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)

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

Earth’s tilt causes the seasonsEarth’s tilt causes the seasons

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

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.

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

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

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

Geocentric – everything revolves around earth

Heliocentric – everything revolves around the sun

MoonMoon

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

The moon seems to shine because The moon seems to shine because it reflects sunlightit reflects sunlight

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

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

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

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

First visible thin slice of the moon is First visible thin slice of the moon is a a waxing crescentwaxing crescent

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

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

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.

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

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

Phases of the Moon

What time period did we get from studying the moon?

Completes its moon cycle in 29.5 daysCompletes revolution in 27.3 days

The moon’s orbit is tilted about 5 degrees relative to Earth’s orbit around the sun.

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

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

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

Penumbra – experiences a partial eclipseUmbra – experiences a total eclipse

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

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?

Does not occur every month because the moon’s orbit is tilted to earth’s orbit.

NASA - Total Lunar Eclipse: February 20, 2008

The moon is 3,476 km in diameter, a little less than the distance across the

contiguous United States.

Moon’s gravity is 1/6 of Earth’s gravity

because it is less massive

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

What could destroy the footprint?

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

http://stardate.org/pdfs/teachers/ObservingTheMoon.pdf

Shows marias

Regolith is the broken rock material on the moon’s surface.

Moon rocks are similar to ours and have tiny crystals of pure iron.

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.

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

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!!!!!)

Arizona Crater

20,000-50,000 years agoAsteroid 80 feet in diameter1.2 kilometers in diameter

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

Albedoreflectance

Albedo of 0

Albedo of 1

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

Clementine

Northside

Farside

Nearside

Southside

Clementine

3 billion metric tons at poles

Lunar Prospector

Desk sized 1998 Confirmed impact

theory

Graphic Organizer

rotates revolves

causing causing

Earth

Graphic Organizer

rotates revolves

causing causing

Earth

On its axis

Night and day

Around the Sun

years