| | Lunar Phases (Site not responding. Last check: 2007-10-31) |
 | | For example, if the Moon is at position 1 in the diagram, the half of it that is lit by the sun is facing away from us, so we do not see the moon at all. |
 | | In the Southern Hemisphere the effect is just the opposite!) Astronomers use this to distinguish between the repeated phases of the moon by referring to the waxing or waning crescent, gibbous, and half phases. |
 | | (We do not observe phases of the outer planets because their orbits lie outside the orbit of the Earth and therefore they can never be between the Sun and the Earth.) There are two differences between the phasesof the Moon and the phases of Venus and Mercury, however. |
| www.astro.umd.edu /education/astro/moon/phases.html (819 words) |