Why is a lunar month longer then a lunar revolution?

Answer 1

Because the Earth is orbiting the Sun so the Moon has to make an extra 1/12 of an orbit to catch up with the Sun in the sky.

Answer 2

What is a lunar month?
We divided our year in 12 months. Just a convention. Not even exact as we need to add one day every four years or so.
We can do what we want to split a lunar year.
What is clear is that the moon rotation and its orbit around the Earth occur in the same roughly 28 of our days, so that one half of the moon is always facing the Earth and we never see the other half surface.
28 days give about 13 moon revolutions in a 365 days year.

Answer 3

At the simplest level, all lunar calendars are based on the approximation that 2 lunations last 59 days: a 30 day full month followed by a 29 day hollow month — but this is only marginally accurate and quickly needs correction by using larger cycles, or the equivalent of leap days.

Answer 4

Because humans like to count month in full days, but the moon revolution is in between full days.

Answer 5

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http://www.answers.com/topic/lunar-month