Solar System: Sun, Earth and Moon

Earth’s size and shapeEarth’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

EarthEarth

GravityGravity 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:Earths properties:Diameter Pole to Pole

12,714 km

Diameter through equator

12,756 km

Circumference poles 40,008 km

Circumference equator 40,008 km

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 fieldEarth’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 fieldsMagnetic fields

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

MagnetosphereMagnetosphere 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 OrbitEarth’s Orbit

ellipse

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

counterclockwise_but_there_are.phpcounterclockwise_but_there_are.php

EarthEarth 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: The Sun and Earth: seasonsseasons

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 earthRotation of the earth http://www.youtube.com/watch?

v=knK87GoNyGo

Revolution of the earthRevolution of the earth

Where the sunlight Where the sunlight hits the earthhits the earth

Slanted less intense at an angle

Direct intense light

Slanted less intense at an angle

SeasonsSeasons 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.

SolsticesSolstices

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.

SolsticeSolstice 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

EquinoxesEquinoxes 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/terc/content/visualizations/es0408/es0408page01.cfm

ReviewReview

What two ways does the earth move in space?

What determines the change in seasons?

Solar eclipseSolar eclipse

http://stargazerpaul.com/s_eclips.htm

http://www.mreclipse.com/Special/image/SEDiagram1c.JPG