Lunar and Planetary Institute






Moon Phases
Potential Questions or Issues

Some students may ask about the “Moon Hoax”—the concept that the Apollo landings on the Moon were faked.  They were indeed real; you can find great answers to their questions on this at Bad Astronomy.com: http://www.badastronomy.com/bad/misc/apollohoax.html

Some students may ask whether the Moon rotates on its axis.  It does; its period of rotation happens to match its period of revolution around the Earth—27.3 days.  (It is tidally locked to the Earth).  Ddemonstration of this can be physical, involving either moving the students or demonstrating with other materials: see Facing the Moon activity and The Quarter Earth-Penny Moon.  For more information on this, go to http://www.badastronomy.com/bad/misc/moon_spin.html

A few students may find another period listed for the Moon’s revolution around the Earth—29.5 days.  Because the Earth and Moon are orbiting the Sun, the Moon has to move a little more than 360 degrees around the Earth to go from New Moon to New Moon, or from Full Moon to Full Moon.  This is called the synodic period.  For more information, go to http://starchild.gsfc.nasa.gov/docs/StarChild/questions/question32.html