Chapter 23Chapter 23

Sun-Earth-Moon SystemsSun-Earth-Moon Systems

Earth PropertiesEarth Properties

In comparison to the rest of the solar In comparison to the rest of the solar system, the Earth is rather small. It has an system, the Earth is rather small. It has an equatorial diameter of approximately equatorial diameter of approximately 12,756 km. Even though 3 of the other 7 12,756 km. Even though 3 of the other 7 planets in our solar system are smaller planets in our solar system are smaller (Mercury, Mars, and Venus), the (Mercury, Mars, and Venus), the remaining 4 planets (Neptune, Uranus, remaining 4 planets (Neptune, Uranus, Saturn, and Jupiter) are much larger. Saturn, and Jupiter) are much larger.

Oblate Spheroid Oblate Spheroid The Earth is not a perfect sphere. The Earth is not a perfect sphere. The true shape of the Earth called an Oblate The true shape of the Earth called an Oblate

Spheroid, or a slightly elongated sphere.Spheroid, or a slightly elongated sphere.The diameter from the North Pole to the South The diameter from the North Pole to the South

Pole (the shortest diameter) is approximately Pole (the shortest diameter) is approximately 12,714 km. 12,714 km.

The equatorial diameter (the longest diameter) The equatorial diameter (the longest diameter) is approximately 12,756 km. is approximately 12,756 km.

This is proven by the fact that gravity changes This is proven by the fact that gravity changes on certain places on the Earth. The further on certain places on the Earth. The further from the center the less something will weigh.from the center the less something will weigh.

Relief and the Lithosphere, HydrosphereRelief and the Lithosphere, Hydrosphere The Earth's surface has many different elevations. The The Earth's surface has many different elevations. The

changing elevations of the land are called relief. changing elevations of the land are called relief. The lithosphere is the The lithosphere is the solidsolid portion of the Earth. Even portion of the Earth. Even

though most of the Earth's surface is covered with though most of the Earth's surface is covered with water, underneath that water is a solid layer of rock. water, underneath that water is a solid layer of rock. This includes soil, rocks, sand, etc. This includes soil, rocks, sand, etc.

The most important thing to know about the The most important thing to know about the lithosphere is what elements make it up. On lithosphere is what elements make it up. On page 11 of the Earth Science Reference Tables is a is a chart which provides you with all of the information chart which provides you with all of the information you will need concerning the makeup of the different you will need concerning the makeup of the different parts of the Earth. parts of the Earth.

The hydrosphere is simply the liquid portion of the The hydrosphere is simply the liquid portion of the Earth. Of course, this is essentially water, or H2O. Earth. Of course, this is essentially water, or H2O.

Earths magnetic fieldEarths magnetic field

Because of the material in the core and Because of the material in the core and the movement of the Earth during its the movement of the Earth during its rotation a magnetic field is produced. rotation a magnetic field is produced.

Just like a magnet Earth has a North and Just like a magnet Earth has a North and south pole which traps a lot of the suns south pole which traps a lot of the suns charged particles of radiation.charged particles of radiation.

A compass will point North because it is A compass will point North because it is attracted to the Northern magnetic charge attracted to the Northern magnetic charge of the Earth.of the Earth.

RotationRotation The Earth’s axis is an imaginary line that cuts directly The Earth’s axis is an imaginary line that cuts directly

through the center of the Earth. through the center of the Earth. At the ends of the axis is the North and South poles. At the ends of the axis is the North and South poles.

On this axis the earth spins or rotates .On this axis the earth spins or rotates . It takes the Earth 23h 56min to go around its axis It takes the Earth 23h 56min to go around its axis

360360°. We round up to 24 hrs. and call this one day on °. We round up to 24 hrs. and call this one day on Earth.Earth.

We orbit or revolve around the sun in 365 days 6 hr, We orbit or revolve around the sun in 365 days 6 hr, 9min.9min.

Earth’s rotation also gives us night and day. The Earth’s rotation also gives us night and day. The portion of the sun that is facing the sun will have portion of the sun that is facing the sun will have daylight and the opposite side will have no daylight daylight and the opposite side will have no daylight and will be called night time.and will be called night time.

Changes of SeasonsChanges of Seasons The Earth’s orbit around the sun is not a perfect circle The Earth’s orbit around the sun is not a perfect circle

its called an ellipse. And the sun is not in the middle its called an ellipse. And the sun is not in the middle of our elliptical orbit. Earth is closet to the sun in of our elliptical orbit. Earth is closet to the sun in January. And furthest away in July.January. And furthest away in July.

We experience climate changes b/c of the Earth’s We experience climate changes b/c of the Earth’s tilted axis not b/c of the distance from the sun.tilted axis not b/c of the distance from the sun.

Earth is tilted 23.5Earth is tilted 23.5° on its axis so the hemisphere that ° on its axis so the hemisphere that is tilted toward the sun will experience warmer is tilted toward the sun will experience warmer climates and longer days than the hemisphere that is climates and longer days than the hemisphere that is tilted away from the sun.tilted away from the sun.

This also causes the facing hemisphere to be exposed This also causes the facing hemisphere to be exposed to greater radiation from the sun causing hotter temps.to greater radiation from the sun causing hotter temps.

Solstices & EquinoxesSolstices & EquinoxesThe solstice is the day when the Sun The solstice is the day when the Sun

reaches its greatest distance north or South reaches its greatest distance north or South of the equator.of the equator.

In the Northern hemisphere the summer In the Northern hemisphere the summer solstice is June 21 or 22 (longest days)solstice is June 21 or 22 (longest days)

Winter solstice is December 21 or 22 Winter solstice is December 21 or 22 (shortest days)(shortest days)

An equinox is when the sun is directly over An equinox is when the sun is directly over the equator of the Earth. the equator of the Earth.

Spring equinox is March 20 or 21 & fall Spring equinox is March 20 or 21 & fall equinox is September 22 or 23equinox is September 22 or 23

H.W. pg 665 ques 1-4H.W. pg 665 ques 1-4

http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/energy/http://www.uwsp.edu/geo/faculty/ritter/geog101/textbook/energy/earth_sun_relations_seasons.htmlearth_sun_relations_seasons.html