https://socratic.org/questions/how-does-the-rotation-of-the-earth-cause-day-and-night
http://www.aurorahunter.com/moon.php
http://www.glogster.com/fairypheebz/seasons/g-6m185vbe27bul1tv7vgfir7
http://www.education.com/science-fair/article/astronomy_moon-phase/