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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!.
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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 • Earth’s revolution • Tilt of Earth’s axis
The Moon’s effect on Earth • Tides
Tide demonstration • http://oceanexplorer.noaa.gov/edu/learning/10_tides/activities/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 umbra Penumbra