In our entire solar system, the only object that shines with its own light is the Sun. That light always beams onto Earth and Moon from the direction of the Sun, illuminating half of our planet in its orbit and reflecting off the surface of the Moon to create moonlight.
When we think of the way the Moon seems to change over the course of a month, we think of phases. But frequent Moon observers know that the Moon also appears to twist, nod, and roll slightly during its journey across the sky, allowing us to peek around the Moon's shoulder and catch glimpses of the farside. This phenomenon is called libration.
Have you ever wondered when the next full moon will be? How about the first quarter moon? Put the dates and times for all the Moon's phases for the year at your fingertips by building your own Moon Phases Calendar and Calculator!
At the new Moon phase, the Moon is so close to the Sun in the sky that none of the side facing Earth is illuminated (position 1 in illustration). In other words, the Moon is between Earth and Sun. At first quarter, the half-lit Moon is highest in the sky at sunset, then sets about six hours later (3). At full Moon, the Moon is behind Earth in space with respect to the Sun. As the Sun sets, the Moon rises with the side that faces Earth fully exposed to sunlight (5).The Moon has phases because it orbits Earth, which causes the portion we see illuminated to change. The Moon takes 27.3 days to orbit Earth, but the lunar phase cycle (from new Moon to new Moon) is 29.5 days. The Moon spends the extra 2.2 days "catching up" because Earth travels about 45 million miles around the Sun during the time the Moon completes one orbit around Earth.
The term "blue Moon" has not always been used this way, however. While the exact origin of the phrase remains unclear, it does in fact refer to a rare blue coloring of the Moon caused by high-altitude dust particles. Most sources credit this unusual event, occurring only "once in a blue moon," as the true progenitor of the colorful phrase.
Have you ever wondered when the next full moon will be? How about the first quarter moon? Now you can have all the dates and times for all the moon phases for the year at your fingertips by building your own moon phases calendar and calculator!
The Moon Phases Calendar and Calculator can tell you approximately what time of day* and where you can see your favorite moon phases! For example, to see the full moon as it sets on the western horizon, you need to be awake before 6 a.m.! It is easier to wait for the full moon to rise in the eastern horizon at about 6 p.m.
The Waning Gibbous on January 1 has an illumination of 74%. This is the percentage of the Moon illuminated by the Sun. The illumination is constantly changing and can vary up to 10% a day. On January 1 the Moon is 19.8 days old. This refers to how many days it has been since the last New Moon. It takes 29.53 days for the Moon to orbit the Earth and go through the lunar cycle of all 8 Moon phases. The 8 Lunar Phases There are 8 lunar phases the Moon goes through in its 29.53 days lunar cycle. The 4 major Moon phases are Full Moon, New Moon, First Quarter and Last Quarter. Between these major phases, there are 4 minor ones: the Waxing Crescent, Waxing Gibbous, Waning Gibbous and Waning Crescent. For more info on the Moon Cycle and on each phase check out Wikipedia Lunar Phase page.
Students use the frosting of Oreo cookies to visualize the phases of the moon using the contrast of the frosting and cookie to represent light and shadows on the surface of the moon as seen from Earth.
This model is a great visual representation of a simple cycle of the phases of the moon. To better visualize the phases of the moon, you may place an object in the center of the moon phase circle and place another object on the outside of the moon phase circle to represent the sun.
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A lunar phase or Moon phase is the apparent shape of the Moon's directly sunlit portion as viewed from the Earth (because the Moon is tidally locked with the Earth, the same hemisphere is always facing the Earth). In common usage, the four major phases are the new moon, the first quarter, the full moon and the last quarter; the four minor phases are waxing crescent, waxing gibbous, waning gibbous, and waning crescent. A lunar month is the time between successive recurrences of the same phase: due to the eccentricity of the Moon's orbit, this duration is not perfectly constant but averages about 29.5 days.
The appearance of the Moon (its phase) gradually changes over a lunar month as the relative orbital positions of the Moon around Earth, and Earth around the Sun, shift. The visible side of the Moon is sunlit to varying extents, 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).[1]
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.[2][a] 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).
Between the principal phases are intermediate phases, during which the apparent shape of the illuminated Moon is either crescent or gibbous. On average, the intermediate phases last one-quarter of a synodic month, or 7.38 days.[b]
When the Sun and Moon are aligned on the same side of the Earth (conjunct), the Moon is "new", and the side of the Moon facing Earth is not illuminated by the Sun. As the Moon waxes (the amount of illuminated surface as seen from Earth increases), the lunar phases progress through the new moon, crescent moon, first-quarter moon, gibbous moon, and full moon phases. The Moon then wanes as it passes through the gibbous moon, third-quarter moon, and crescent moon phases, before returning back to new moon.
The terms old moon and new moon are not interchangeable. The "old moon" is a waning sliver (which eventually becomes undetectable to the naked eye) until the moment it aligns with the Sun and begins to wax, at which point it becomes new again.[4] Half moon is often used to mean the first- and third-quarter moons, while the term quarter refers to the extent of the Moon's cycle around the Earth, not its shape.
When an illuminated hemisphere is viewed from a certain angle, the portion of the illuminated area that is visible will have a two-dimensional shape as defined by the intersection of an ellipse and circle (in which the ellipse's major axis coincides with the circle's diameter). If the half-ellipse is convex with respect to the half-circle, then the shape will be gibbous (bulging outwards),[5] whereas if the half-ellipse is concave with respect to the half-circle, then the shape will be a crescent. When a crescent moon occurs, the phenomenon of earthshine may be apparent, where the night side of the Moon dimly reflects indirect sunlight reflected from Earth.[6]
In the Northern Hemisphere, if the left side of the Moon is dark, then the bright part is thickening, and the Moon is described as waxing (shifting toward full moon). If the right side of the Moon is dark, then the bright part is thinning, and the Moon is described as waning (past full and shifting toward new moon). Assuming that the viewer is in the Northern Hemisphere, the right side of the Moon is the part that is always waxing. (That is, if the right side is dark, the Moon is becoming darker; if the right side is lit, the Moon is getting brighter.)
Closer to the Equator, the lunar terminator will appear horizontal during the morning and evening. Since the above descriptions of the lunar phases only apply at middle or high latitudes, observers moving towards the tropics from northern or southern latitudes will see the Moon rotated anti-clockwise or clockwise with respect to the images in this article.
When the Moon (seen from Earth) is a thin crescent, Earth (as viewed from the Moon) is almost fully lit by the Sun. Often, the dark side of the Moon is dimly illuminated by indirect sunlight reflected from Earth, but is bright enough to be easily visible from Earth. This phenomenon is called earthshine, sometimes picturesquely described as "the old moon in the new moon's arms" or "the new moon in the old moon's arms".
Archaeologists have reconstructed methods of timekeeping that go back to prehistoric times, at least as old as the Neolithic. The natural units for timekeeping used by most historical societies are the day, the solar year and the lunation. The first crescent of the new moon provides a clear and regular marker in time and pure lunar calendars (such as the Islamic Hijri calendar) rely completely on this metric. The fact, however, that a year of twelve lunar months is ten or eleven days shorter than the solar year means that a lunar calendar drifts out of step with the seasons. Lunisolar calendars resolve this issue with a year of thirteen lunar months every few years, or by restarting the count at the first new (or full) moon after the winter solstice. The Sumerian calendar is the first recorded to have used the former method; Chinese calendar uses the latter, despite delaying its start until the second or even third new moon after the solstice. The Hindu calendar, also a lunisolar calendar, further divides the month into two fourteen day periods that mark the waxing moon and the waning moon.
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