As the moon orbits the earth, we see the light side of the moon in various
phases. A full lunar cycle occurs when the moon completely orbits the earth
in about 27 days 7 hours 43 minutes 11.5 seconds.
Note: a blue moon is the second occurrence of a full moon
in one calendar month.
Fields of Science,
The Solar System,
What would you weigh on other planets?, Current Moon Phase and Next Full Moon