What is a lunar month?
For thousands of years people have used the Moon to measure the passing of time and the seasons. The Moon revolves around its own axis every 29 
days, which is also the time it takes to complete one orbit around the Earth. This period of time is known as a lunar month. Our calendar has been devised to follow this astronomical pattern fairly closely. It has to be adjusted slightly to round up the number of days in each month to a more convenient figure. The sidereal month, of 27.32 days, measures the time it takes for the stars to return to an identical position in the sky.
Wobbling Moon
We always see the same side of the Moon as it rotates around the Earth. However, it wobbles slightly as it orbits the Earth, giving us a glimpse of some of the features around the edges of its hidden side. Because of this wobble, we can actually see about 59 percent of the Moon’s surface from the Earth.
How far away is the Moon?
The distance of the Moon away from the Earth was settled once and for all after the Apollo astronauts left a small reflector on the Moon’s surface. Lasers were directed at this reflector, and the time taken for the laser light to reach the Moon and be reflected back again was measured. As light has a constant speed this enabled the exact distance of the Moon from the Earth to be calculated. This distance is 384,000 km, though it varies slightly because the Moon does not have a perfectly circular orbit.