1. Retrograde Motion & Eclipses L/O: To describe retrograde motion and why solar and lunar eclipses happen.

2. What is an eclipse? A lunar eclipse is when the earth interrupts light shining on the moon A solar eclipse is when the moon interrupts light from the sun

3. Solar Eclipse

4. http://msnbc.com/news/wld/graphics/eclips e_dw.swf

5. Lunar Eclipse

6. http://www.guardian.co.uk/flash/lunar_eclips e2.swf

7. The diagrams show different ways of explaining eclipses. As the sun is an extended source of light, the shadows do not have hard edges. There is a region on hard darkness (umbra) and a region of partial darkness (penumbra)

8. The size of the eclipse will depend on the size of the light source. Label the umbra and the penumbra

9. If the moon goes around the earth every 28 days, why isn’t there an eclipse every month? http://msnbc.com/news/wld/graphics/eclipse _dw.swf Lets say the plane of the Earth and the Sun is a straight line. The moon will be 5 o off that plane. Hence why solar eclipses happen in specific locations.

10. Retrograde Motion Some planets can be seen with the naked eye. The planets steadily move in one direction. Ancient astronomers noticed that sometimes the planets appeared slow down then move backwards. This is retrograde motion!

11. http://bigbang.physics.tamu.edu/Figures/St olenAnimations/mars_retrograde_motion.s wfhttp://bigbang.physics.tamu.edu/Figures/St olenAnimations/mars_retrograde_motion.s wf http://www.dybim.com/astro1/MarsRetrogr ade.swfhttp://www.dybim.com/astro1/MarsRetrogr ade.swf