Solar System: Sun, Earth and Moon

Earth’s size and shape The earth is sphere. Aristotle made three observations: Objects fall straight down Earth’s shadow is curved People see different stars

Earth

Gravity The attractive force between two objects Depends on the masses and distance between two objects. How does the pull of gravity indicate that the Earth’s shape is spherical?

Earths properties: Diameter Pole to Pole 12,714 km Diameter through equator 12,756 km Circumference poles 40,008 km Circumference equator Mass 5.98 X 1024 kg Avg distance from sun 149,600,000km Avg distance from moon 384,400 km Period of rotation 23hr 56 min Period of revolution 365 days, 6h,9min

Earth’s magnetic field Hypothesized that the strong rotation of the earth and the movement in the core set up the magnetic field The magnetic poles are 11.5* off from the physical poles. They wander due to the movement of the Earths crust and mantle

Magnetic fields http://www.google.com/imgres?q=earths+magnetic+poles&hl=en&sa

Magnetosphere An area in the Earth’s magnetic field that deflects harmful radiation coming from the sun as solar wind These collide with atoms in the atmosphere causing the aurora borealis or aurora australis

Earth’s Orbit ellipse

http://scienceblogs.com/startswithabang/2010/10/counterclockwise_but_there_are.php

Earth Is a planet Supports life Has lower CO2 than Venus but trapped CO2 may contribute to green house effect Ocean absorbs CO2

If the magnetic field was not there to protect us what would happen to the earth?

The Sun and Earth: seasons The earth moves in two ways: Rotation: the earth spinning like a top around its axis. 24 hours or one day Revolution: The earth traveling around the sun. It takes one year 365 ¼ days

Rotation of the earth http://www.youtube.com/watch?v=knK87GoNyGo

Revolution of the earth

Where the sunlight hits the earth Slanted less intense at an angle Direct intense light Slanted less intense at an angle

Seasons Seasons are caused by the tilt of the Earth’s axis as it moves around the sun. The amount of sunlight depends on the Latitude that the sunlight is directly hitting.

Solstices Solstices occur twice a year on the days that the sun appears directly overhead at latitude 23.5 north or 23.5 south. Remember the earth tilts 23.5 degrees off of the axis. Northern Hemisphere: Summer solstice on June 21st. The Northern Hemisphere is tilted toward the sun. The longest day in the North and the shortest in the South. North- Summer, South-Winter.

Solstice Winter solstice occurs on December 21 six months after the Summer Solstice. The Northern Hemisphere is tilted away from the sun and receives the least amount of light. Shortest day in the North and Longest day in the South. North-Winter, South-Summer

Equinoxes Halfway between the solstices are two days called Equinoxes. See page 754: Halfway between the solstices are two days called Equinoxes. At the Equinox neither hemisphere is tilted toward the sun the length of day light and night is EQUAL. March 22- Spring, September 22- autumn

Spring equinox is called Vernal equinox. Autumn equinox is called the Autumnal equinox. On these two days the sun is directly overhead the equator.

http://www.classzone.com/books/earth_science/ter c/content/visualizations/es0408/es0408page01.cfm

Review What two ways does the earth move in space? What determines the change in seasons?

Solar eclipse

http://stargazerpaul.com/s_eclips.htm http://www.mreclipse.com/Special/image/SEDiagram1c.JPG