The terms old moon and new moon are not interchangeable. The Moon then wanes as it passes through the gibbous moon, third-quarter moon, crescent moon, and back to new moon. As the Moon waxes (the amount of illuminated surface as seen from Earth increases), the lunar phases progress through new moon, crescent moon, first-quarter moon, gibbous moon, and full moon. When the Sun and Moon are aligned on the same side of the Earth, the Moon is "new", and the side of the Moon facing Earth is not illuminated by the Sun. Waxing and waning Diagram of the Moon's phases: The Earth is at the center of the diagram and the Moon is shown orbiting. The camera is locked to the Moon as Earth rapidly rotates in the foreground. This video provides an illustration of how the Moon passes through its phases – a product of its orbit, which allows different parts of its surface to be illuminated by the Sun over the course of a month. Photograph (view from Northern Hemisphere) Principal and intermediate phases of the Moon Moon phase Because of this, around 59% of the Moon's surface has been imaged from the ground. Lunar libration causes part of the back side of the Moon to be visible to a terrestrial observer some of the time. The effect is subtle to the naked eye, from night to night, yet somewhat obvious in time-lapse photography. Lunar libration Animation showing progression of moon phase.Īs seen from Earth, the Moon's eccentric orbit makes it both slightly change its apparent size, and to be seen from slightly different angles. Non-Western cultures may use a different number of lunar phases for example, traditional Hawaiian culture has a total of 30 phases (one per day). A last quarter moon appears highest on the autumn equinox and lowest on the spring equinox. A full moon appears highest on the winter solstice and lowest on the summer solstice.A first quarter moon appears highest on the spring equinox and lowest on the autumn equinox.A new moon appears highest on the summer solstice and lowest on the winter solstice.The duration from full moon to new moon (or new moon to full moon) varies from approximately 13 days 22 + 1⁄ 2 hours to about 15 days 14 + 1⁄ 2 hours. The term waxing is used for an intermediate phase when the Moon's apparent shape is thickening, from new to a full moon and waning when the shape is thinning. On average, the intermediate phases last one-quarter of a synodic month, or 7.38 days. Each of these phases appears at slightly different times at different locations on Earth, and tabulated times are therefore always geocentric (calculated for the Earth's center).īetween the principal phases are intermediate phases, during which the Moon's apparent shape is either crescent or gibbous. There are four principal (primary, or major) lunar phases: the new moon, first quarter, full moon, and last quarter (also known as third or final quarter), when the Moon's ecliptic longitude is at an angle to the Sun (as viewed from the center of the Earth) of 0°, 90°, 180°, and 270° respectively. The upper part of the diagram is not to scale, as the Moon, the Earth, and the Moon's orbit are all much smaller relative to the Earth's orbit than what is shown here. Each phase would be rotated 180° if seen looking northward from the Southern Hemisphere. The phases of the Moon as viewed looking southward from the Northern Hemisphere. Įach of the four major lunar phases is approximately 7.4 days ☑9 hours (6.58–8.24 days), the variation being due to the eccentricity of the Moon's orbit and thus it orbiting at varying speeds. The visible side of the Moon is variously sunlit, depending on the position of the Moon in its orbit, with the sunlit portion varying from 0% (at new moon) to nearly 100% (at full moon). 29.53 days) as the orbital positions of the Moon around Earth, and Earth around the Sun, shift. The lunar phases gradually change over a synodic month ( c. Shape of the Moon's directly sunlit portion as viewed from Earth The lunar phases and librations in 2023 as viewed from the Northern Hemisphere at hourly intervals, with titles and supplemental graphics The lunar phases and librations in 2023 as viewed from the Southern Hemisphere at hourly intervals, with titles and supplemental graphics A full moon sets behind San Gorgonio Mountain in California on a midsummer's morning.Ĭoncerning the lunar month of approximately 29.53 days as viewed from Earth, the lunar phase or Moon phase is the shape of the Moon's directly sunlit portion, which can be expressed quantitatively using areas or angles, or described qualitatively using the terminology of the four major phases ( new moon, first quarter, full moon, last quarter) and four minor phases (waxing crescent, waxing gibbous, waning gibbous, and waning crescent).
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