The Earth-Moon-Sun System
(chapter 7)
Points of note….
 Earth is a sphere.
 Gravity causes large objects (planets) to form spheres.
 Earth has a magnetic field that protects us from solar
radiation.
Continued…
 Ironically, the magnetic poles are not at the North/South
Poles!
Earth’s orbit has an elliptical shape…
why is that important?
Time and Seasons
 The Earth is spherical…
 and can be divided into 3600
 It spins (rotates) in ~ 24 hours
 How many degrees does it turn in 1 hour?
 This is also the width of a time zone (15o)!
 The International Date Line – the location where a day is
added/subtracted
 Revolution – Earth’s motion around the Sun
 Remember…it’s elliptical!
Why do we have seasons?
Earth’s rotation
2. Earth’s revolution
3. Tilt of Earth’s axis
1.
The Moon’s effect on Earth
 Tides
Tide demonstration
 http://oceanexplorer.noaa.gov/edu/learning/10_tides/acti
vities/predicting_tides.html#activity
Moon phases
 Waxing phase – as the moon grows larger each night
 Waning phase – as the moon grows smaller
 Crescent…< 25% is showing
 Gibbous…> 25% is showing
Solar eclipse
Penumbra
umbra
Lunar eclipse