Solar System:
Sun, Earth and Moon

How to get to Mars
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
Circumference poles
12,756 km
40,008 km
Circumference equator
Mass
Avg distance from sun
40,008 km
5.98 X 1024 kg
149,600,000km
Avg distance from moon
384,400 km
Period of rotation
Period of revolution
23hr 56 min
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/i
mgres?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

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/SEDiagra
m1c.JPG
Solar eclipse