Lunar Phases

Mankind has been observing the various stages of lunar phases since time immemorial. One of the most interesting phenomena of nature that has fascinated mankind is the sight of the ever-changing appearances of the moon.

Basic Facts about Lunar Cycles

The moon is the only satellite of the Earth; it revolves around the Earth in an elliptical path and takes approximately 29.5 days to complete one lunar cycle. Since the orbit is elliptical in shape, the angular distance between the moon and the Earth changes from time to time. Half of the moon remains lit by sunlight all the time. To an observer on the Earth, this bright part of the moon is visible in changing angles due to its rotation round the Earth in its oval-shaped orbit. These changing angles are the reason for the changing appearances of the moon i.e. the lunar phases.

Main Phases of Lunar Cycle

The main phases of the lunar cycle or lunation can be divided into nine categories. The sequences of the lunar cycles are as follows:

• New Moon - During this phase, the sun, moon and Earth are aligned in a straight line. The moon is placed in between the Earth and the sun. So the illuminated hemisphere of the moon will be invisible to an observer on the Earth.
• Waxing Crescent – It is the phase in which the New Moon starts drifting to next Full Moon. During this phase the moon will be visible only between sunset and midnight.
• The First Quarter – In this phase, the moon is perpendicular with respect to both the sun and the Earth. Also, The sunlit portion of the moon is in an increasing mode.
• Waxing Gibbous – It is the phase falling in between the First Quarter and the Full Moon and its duration is of seven days. Here the moon is illuminated from right to left. This moon is visible after sunset and disappears just before the sunrise.
• Full Moon – In the full moon phase, the sun, moon and Earth are aligned in a straight line. The moon is located opposite to the Earth as a result of which the portion of the moon illuminated by sunlight is visible to us.
• Waning Gibbous – This phase describes the Moon that is shrinking to a smaller size. During this period, the moon is lit from left to right. As it sets after the sunrise, this moon can be seen early in the morning.
• The Third Quarter - This phase comes after the Full Moon, when the sun partially lights up the moon. But in this phase, the illuminated portion of the moon reduces to half of its size in the full moon phase.
• Waning Crescent - Only a thin slice of the moon is visible in this phase and that too, not before midnight.
• New Moon – This phase marks the completion of a cycle and the moon gets ready to start a new journey all over again.

Researchers and scientists believe that lunar cycles have a significant effect on sea tides and may cause some climatic change. Apart from Scientists, lunar cycles are also closely watched by astrologers, who believe that lunar cycles are mainly responsible for the way humans react to a particular situation at a given point of time.

Questions to Ponder

• Is the Moon seen as a crescent all over the world at the same time? Is the same phase of the moon visible from the Northern and Southern hemispheres?
• How does the position of Moonrise and Moonset change?
• Why do the size and brightness of the full moon change?