New moon

The lunar phase when the Moon lies approximately between Earth and the Sun, with its illuminated side facing away from Earth. It is usually invisible from Earth, though it can be seen during a solar eclipse.

Lunar phases: The recurring changes in how much of the Moon’s sunlit hemisphere is visible from Earth. New moon is one point in the cycle of changing visible illumination.
Sunlight: Electromagnetic radiation emitted by the Sun, including the visible light that illuminates the Moon. The Moon’s phases arise from viewing different portions of its sunlit half.
Lunisolar calendar: A calendar that tracks lunar months while keeping its year aligned with the solar year. Many lunisolar months begin at or near the new moon.
Full moon: The lunar phase when the Moon’s Earth-facing hemisphere is nearly fully illuminated. It occurs roughly halfway through the synodic month, opposite new moon.
Synodic month: The average interval of about 29.5 days between successive identical lunar phases. It measures the time from one new moon to the next.
Lunar terminator: The boundary between the illuminated and dark hemispheres of the Moon. Its position on the lunar disk changes as the phase progresses.
Islamic calendar: A lunar calendar of twelve months used to set Islamic dates and observances. The visibility of the new crescent helps determine the start of each month.
First quarter: The phase when about half of the Moon’s visible disk is illuminated and waxing. Unlike new moon, it shows a clear half-disk and lies about a quarter-cycle later.
Solar eclipse: An event in which the Moon passes between Earth and the Sun, obscuring some or all of the Sun. A solar eclipse can occur only near new moon, when alignment is close enough.
Geocentric coordinates: A system that describes celestial positions as viewed from Earth’s center. The phase is defined by the Moon’s position relative to Earth and the Sun.

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