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 SeasonsThe Earth is spherical…

and can be divided into 3600

It spins (rotates) in ~ 24 hoursHow 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 SunRemember…it’s elliptical!

Why do we have seasons?1. Earth’s rotation2. Earth’s revolution3. Tilt of Earth’s axis

The Moon’s effect on EarthTides

Tide demonstrationhttp://

oceanexplorer.noaa.gov/edu/learning/10_tides/activities/predicting_tides.html#activity

Moon phasesWaxing phase – as the moon grows larger

each nightWaning phase – as the moon grows smallerCrescent…< 25% is showingGibbous…> 25% is showing

Solar eclipse

umbra

Penumbra

Lunar eclipse