Lunar phase

The lunar phases and librations in 2024 as viewed from the Northern Hemisphere at hourly intervals, with titles and supplemental graphics

The lunar phases and librations in 2024 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.

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]

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Besides the Sun, the Moon is the most obvious object in the sky. Bright, silvery, with tantalizing features on its face, it’s been the target of imagination, poetry, science, and even the occasional rocket. If you pay even the most cursory attention to it, you’ll see that it changes every day; sometimes it’s up in the day, sometimes at night, and its shape is always changing. What causes this behavior? The Moon is basically a giant ball of rock 3500 kilometers across hanging in space. Its surface is actually pretty dark, with about the same reflectivity as a chalkboard or asphalt. However, it looks bright to us because it’s sitting in full sunlight; the Sun illuminates it, and it reflects that light down to us here on Earth. And because it’s a sphere, and orbiting the Earth, the way we see it lit by the Sun changes with time. That’s what causes its phases: geometry. The important thing to remember through all this is, because the Moon is a ball and in space, half of it is always illuminated by the Sun! This is true for the Earth, too, and every spherical object in space; half faces the Sun, half faces away. We call the part facing the Sun the daylight or bright side, and the half facing away the night or dark side. The phase of the Moon refers to what shape the Moon appears to us; how much of it we see illuminated from the Earth. The key to all this is this line, dividing the lit day side from the unlit night side. We call that line the terminator. If you’re facing the moon, with the sun behind you, you’re seeing the half of the moon that is fully illuminated by sunlight and it looks full. If you’re off to the side you see half of the lit side and half of the dark side and we say the moon is half full. If the sun is on the other side of the moon, you’re look at the unlit half, and it looks dark. Now, mind you, I haven’t moved anything except our point of view here, so at all times the Moon is always half lit, and half dark. Remember that. The phase of the Moon we see depends on from what direction the sunlight’s hitting it, and the angle we see that from Earth. The Moon orbits the Earth roughly once per month. In fact, that’s where the word “month” comes from; “month” and “Moon” are cognates, words that have similar etymological histories, and in most languages, including English, the two words are very similar. The length of time we call the month is derived from the length of time it takes the Moon to go through all its phases -- 29.5 days. So. To describe the phases, let’s start at the beginning: New Moon. New Moon happens when the Sun, Moon, and Earth are all more or less in a line. The Moon’s orbit is actually tipped a bit to the Earth’s, so sometimes new Moon happens when the Moon is “below” the Sun, or “above” it. But at some point in its orbit, at some point in the month, it appears to be as close to the Sun as it can. What does this look like from Earth? The Moon is between the Earth and the Sun, so from our perspective we only see the dark half, the unilluminated half, of the Moon. The other side, the far side, of the Moon is lit, but we can’t see it. It makes sense then to call this the beginning of the Moon’s cycle, hence the term “New Moon”. Now think about this for a sec: Because the Moon is near the Sun in the sky, it travels across the sky with the Sun. It’s up during the day! You can only see it from the part of the Earth that’s lit, which is when it’s daytime. It’s a very common misconception that the Moon is only up at night, but it’s up during the day literally just as often. At New Moon, the Moon stays near the Sun, so it rises at sunrise, and sets at sunset. This makes it extremely difficult to see; it is, after all, sitting next to the brightest object in the sky, and only a little bit of it is lit from our perspective. But not for long. Because the Moon is orbiting the Earth, after a couple of days it’s moved a bit to the east. Now we’re seeing it along a slight angle, and we can see a little bit of the illuminated half of the Moon on its side toward the Sun. The terminator, the day/night line, appears curved around the Moon, so what we see is a thin illuminated crescent Moon. At this point the crescent is still very thin, with the horns of the crescent pointing away from the Sun. Note that the Moon is still pretty close to the Sun in the sky, just a bit to the east, rising maybe an hour or two after sunrise. But this means it’s up all day, and then sets after the Sun does. This is the best time to see the crescent Moon, when the Sun has already set and the sky starts to get dark. The Moon will be low over the western horizon, and it will set soon after the Sun does. Let’s wait a couple of days. OK, now the Moon has moved a bit more in its orbit around the Earth, and is farther from the Sun in the sky. We see a little more of the illuminated part, and the crescent is wider. Since it’s getting thicker, we say this is a “waxing crescent” Moon; waxing means growing or getting bigger. It’s also well away from the Sun now, so it’s easier to spot, even during the day before sunset. Seven or so days after new Moon we get to our first milestone: the Moon is now one-quarter of the way around its orbit. It’s 90° away from the Sun in the sky, which means we’re looking straight down on the terminator, the Moon’s day/night line. It cuts right down the middle of the visible face of the Moon, so it’s half lit, with the sunward side of the Moon visible and the other side dark. Confusingly, this phase is properly named “first quarter” because the Moon is ¼ of the way through its cycle, ¼ of the way through its orbit around the Earth, even though it looks half full. So it’s not really the half-full moon -- astronomers prefer “first quarter,” so if you want to sound all astronomery, then you should call it that. But time marches on. The Moon continues on its gravitational dance with Earth, swinging around its orbit. Now more than half full, we say its shape is “gibbous”, which means swollen or convex. Since it’s getting wider, this is actually the waxing gibbous phase of the Moon. It rises in the late afternoon, and is up most of the night. Our next big step comes two weeks after new Moon, when it’s moved halfway through its orbit. It is now opposite the Sun in the sky, 180° around. The Earth is between the Moon and Sun, so we’re looking at the fully-illuminated half of the Moon. This is the full Moon. Because it’s opposite the Sun, it rises at sunset and sets and sunrise; it’s up all night shining down on the Earth. But again, wait a couple of days and things change. When the Moon is full it’s 180° around the sky from the Sun, so as it continues to move around the Earth in a circle the distance between it and the Sun is now starting to decrease, even as it continues on in the same direction. As before, it keeps rising and setting later, but now it rises after sunset, and sets after sunrise. If you get up early in the morning as the Sun is just rising in the east, you’ll see the nearly-but-not-quite full Moon setting in the west. Not only that, but we’re about to go through all the phases again, but in reverse order. A few days after full Moon the lit side is shrinking. It’s in the waning, or shrinking, gibbous phase. Then, three weeks or so after new Moon, and a week after full, the Moon is once again half lit, the terminator splitting the Moon’s face in two even halves. This is the “third quarter” Moon, because the Moon is ¾ of the way through its cycle. It’s a lot like the first quarter, but the side that was lit is now dark, and vice versa. It’s 270° around the sky from the Sun. It rises at midnight and sets at noon. A few days later and the Moon is a crescent again, getting thinner. It’s now a “waning crescent.” It rises just a couple of hours before sunrise, and sets a couple of hours before sunset. Then, finally, we’re back where we started. One month after new Moon, the Moon has traveled 360° around the sky, and is once again as close to the Sun as it can get. It’s new Moon, and the cycle starts up again as it has for time immemorial. An interesting thing happens if you move your perspective from the Earth to the Moon. The phases of the Moon we see from Earth depend on the angle of the Moon and Sun in the sky. But on the Moon, the angles are exactly 180° reversed; at new Moon, when the Moon is between the Earth and Sun, the Earth is opposite the Sun as seen from the Moon. It’s full Earth! All the other phases are opposite too, so when we see a full Moon, a Moon-dweller would see a new Earth, and so on. Have you ever looked at the thin crescent Moon and seen the ghostly face of the rest of the unlit side? That’s because it’s not really unlit: the nearly full Earth is reflecting sunlight on the Moon, lighting up the otherwise dark part. The Earth is bigger and more reflective than the Moon, so it’s actually 50 times brighter than a full Moon! This glow is called Earthshine, a term I quite like. Even more poetically, it’s been called “the old Moon in the new Moon’s arms”, referring to the unlit part surrounded by the crescent new Moon’s horns. That’s lovely, isn’t it? The Moon is one of the most beautiful and most gratifying objects in the sky to observe. It’s different every day! Yet it’s also the same, because we see, more or less, the same half of it, the same face all the time. It’s big and bright, and the features on its surface discernible by eye (and even better with binoculars or a small telescope). As the phases change, inexorably, day after day, the angle of sunlight hitting the surface changes, bringing new things into our view. The motions become comforting, even familiar. It’s a reminder that the Universe may seem strange and complicated and forbidding at first, but over time, as you get outside and experience it, it becomes your neighborhood. Welcome home. Today you learned why the Moon has phases: It’s a sphere, and it orbits the Earth, so the angle at which we see its lit side changes. It goes from new, to waxing crescent, to half full, waxing gibbous, full, waning gibbous, half full, waning crescent, and then the cycle starts all over again. This also affects when it rises and sets, and what we see on the surface. Crash Course is produced in association with PBS Digital Studios. This episode was written by me, Phil Plait. The script was edited by Blake de Pastino, and our consultant is Dr. Michelle Thaller. It was co-directed by Nicholas Jenkins and Michael Aranda, and the graphics team is Thought Café.

Phases of the Moon

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]

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. 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.

Due to lunar motion relative to the meridian and the ecliptic, in Earth's northern hemisphere:

A new moon appears highest at the summer solstice and lowest at the winter solstice.
A first-quarter moon appears highest at the spring equinox and lowest at the autumn equinox.
A full moon appears highest at the winter solstice and lowest at the summer solstice.
A last-quarter moon appears highest at the autumn equinox and lowest at the spring equinox.

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).^[3]

Lunar libration

As seen from Earth, the Moon's eccentric orbit makes it both slightly change its apparent size, and to be seen from slightly different angles. The effect is subtle to the naked eye, from night to night, yet somewhat obvious in time-lapse photography.

Lunar libration causes part of the back side of the Moon to be visible to a terrestrial observer some of the time. Because of this, around 59% of the Moon's surface has been imaged from the ground.

Principal and intermediate phases of the Moon

Moon phase	Illuminated portion		Visibility	Average moonrise time^[c]	Culmination time (highest point)	Average moonset time^[c]	Illustration		Photograph (view from Northern Hemisphere)
Moon phase	Northern Hemisphere	Southern Hemisphere	Visibility	Average moonrise time^[c]	Culmination time (highest point)	Average moonset time^[c]	Northern Hemisphere	Southern Hemisphere	Photograph (view from Northern Hemisphere)
New Moon	Disc completely in Sun's shadow (lit by earthshine only)		Invisible (too close to Sun) except during a solar eclipse	06:00	12:00	18:00
Waxing crescent	Right side, (0%–50%) lit disc	Left side, (0%–50%) lit disc	Late morning to post-dusk	09:00	15:00	21:00
First quarter	Right side, 50.1% lit disc	Left side, 50.1% lit disc	Afternoon and early night	12:00	18:00	00:00
Waxing gibbous	Right side, (50%–100%) lit disc	Left side, (50%–100%) lit disc	Late afternoon and most of night	15:00	21:00	03:00
Full Moon	100% illuminated disc		Sunset to sunrise (all night)	18:00	00:00	06:00
Waning gibbous	Left side, (100%–50%) lit disc	Right side, (100%–50%) lit disc	Most of night and early morning	21:00	03:00	09:00
Last quarter	Left side, 50.1% lit disc	Right side, 50.1% lit disc	Late night and morning	00:00	06:00	12:00
Waning crescent	Left side, (50%–0%) lit disc	Right side, (50%–0%) lit disc	Pre-dawn to early afternoon	03:00	09:00	15:00

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. The camera is locked to the Moon as Earth rapidly rotates in the foreground.

Waxing and waning

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]

Orientation by latitude

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.)

In the Southern Hemisphere, the Moon is observed from a perspective inverted, or rotated 180°, to that of the Northern and to all of the images in this article, so that the opposite sides appear to wax or wane.

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.

The lunar crescent can open upward or downward, with the "horns" of the crescent pointing up or down, respectively. When the Sun appears above the Moon in the sky, the crescent opens downward; when the Moon is above the Sun, the crescent opens upward. The crescent Moon is most clearly and brightly visible when the Sun is below the horizon, which implies that the Moon must be above the Sun, and the crescent must open upward. This is therefore the orientation in which the crescent Moon is most often seen from the tropics. The waxing and waning crescents look very similar. The waxing crescent appears in the western sky in the evening, and the waning crescent in the eastern sky in the morning.

Earthshine

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".

Timekeeping

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.

The ancient Roman calendar was broadly a lunisolar one; on the decree of Julius Caesar in the first century BCE, Rome changed to a solar calendar of twelve months, each of a fixed number of days except in a leap year. This, the Julian calendar (slightly revised in 1582 to correct the leap year rule), is the basis for the Gregorian calendar that is almost exclusively the civil calendar in use worldwide today.

Calculating phase

Each of the four intermediate phases lasts approximately seven days (7.38 days on average), but varies ±11.25% due to lunar apogee and perigee.

The number of days counted from the time of the new moon is the Moon's "age". Each complete cycle of phases is called a "lunation".^[7]

The approximate age of the Moon, and hence the approximate phase, can be calculated for any date by calculating the number of days since a known new moon (such as 1 January 1900 or 11 August 1999) and reducing this modulo 29.53059 days (the mean length of a synodic month).^[8]^[d] The difference between two dates can be calculated by subtracting the Julian day number of one from that of the other, or there are simpler formulae giving (for instance) the number of days since 31 December 1899. However, this calculation assumes a perfectly circular orbit and makes no allowance for the time of day at which the new moon occurred and therefore may be incorrect by several hours. (It also becomes less accurate the larger the difference between the required date and the reference date). It is accurate enough to use in a novelty clock application showing lunar phase, but specialist usage taking account of lunar apogee and perigee requires a more elaborate calculation.

Effect of parallax

The Earth subtends an angle of about two degrees when seen from the Moon. This means that an observer on Earth who sees the Moon when it is close to the eastern horizon sees it from an angle that is about 2 degrees different from the line of sight of an observer who sees the Moon on the western horizon. The Moon moves about 12 degrees around its orbit per day, so, if these observers were stationary, they would see the phases of the Moon at times that differ by about one-sixth of a day, or 4 hours. But in reality, the observers are on the surface of the rotating Earth, so someone who sees the Moon on the eastern horizon at one moment sees it on the western horizon about 12 hours later. This adds an oscillation to the apparent progression of the lunar phases. They appear to occur more slowly when the Moon is high in the sky than when it is below the horizon. The Moon appears to move jerkily, and the phases do the same. The amplitude of this oscillation is never more than about four hours, which is a small fraction of a month. It does not have any obvious effect on the appearance of the Moon. It does however affect accurate calculations of the times of lunar phases.

Misconceptions

Orbital period

It can be confusing that the Moon's orbital sidereal period is 27.3 days while the phases complete a cycle once every 29.5 days (synodic period). This is due to the Earth's orbit around the Sun. The Moon orbits the Earth 13.4 times a year, but only passes between the Earth and Sun 12.4 times.

Eclipses

The lunar phase depends on the Moon's position in orbit around the Earth and the Earth's position in orbit around the Sun. This animation (not to scale) looks down on Earth from the north pole of the ecliptic.

It might be expected that once every month, when the Moon passes between Earth and the Sun during a new moon, its shadow would fall on Earth causing a solar eclipse, but this does not happen every month. Nor is it true that during every full moon, the Earth's shadow falls on the Moon, causing a lunar eclipse. Solar and lunar eclipses are not observed every month because the plane of the Moon's orbit around the Earth is tilted by about 5° with respect to the plane of Earth's orbit around the Sun (the plane of the ecliptic). Thus, when new and full moons occur, the Moon usually lies to the north or south of a direct line through the Earth and Sun. Although an eclipse can only occur when the Moon is either new (solar) or full (lunar), it must also be positioned very near the intersection of Earth's orbital plane about the Sun and the Moon's orbital plane about the Earth (that is, at one of its nodes). This happens about twice per year, and so there are between four and seven eclipses in a calendar year. Most of these eclipses are partial; total eclipses of the Moon or Sun are less frequent.

Footnotes

^ The quarter phases happen when the observer–Moon–Sun angle is 90°^{[citation needed]}, also known as quadrature^{[dubious – discuss]}. This is not the same as a right angle^{[dubious – discuss]}, but the difference is very slight. /
^ Their durations vary slightly because the Moon's orbit is somewhat elliptical, so its orbital speed is not constant.
^ ^a ^b As with sunrise and sunset, there are seasonal variations in the time of moonrise and moonset.
^ Lunar months vary in length about the mean by up to seven hours in any given year. In 2001, the synodic months varied from 29d 19h 14m in January to 29d 07h 11m in July.^[9]

References

Citations

^ "Is the 'full moon' merely a fallacy?". NBC News. 28 February 2004. Retrieved 2023-05-30.
^ Seidelmann 1992, p. 478.
^ "Hawaiian Moon Names". Imiloa, Hilo Attractions. Archived from the original on 2014-01-02. Retrieved 2013-07-08.
^ "Free Astronomy Lesson 7 - The Phases of the Moon". Archived from the original on 2023-04-14. Retrieved 2015-12-28.
^ "Gibbous Definition & Meaning". Dictionary.com. Archived from the original on 2023-04-21. Origin of gibbous: 1350–1400; Middle English <Latin gibbōsus humped, equivalent to gibb(a) hump + -ōsus-ous
^ Asmelash & Allan 2019.
^ "Phases of the Moon and Percent of the Moon Illuminated". aa.usno.navy.mil. Archived from the original on 2018-02-06. Retrieved 2018-02-12.
^ Seidelmann 1992, p. 577.
^ "Length of the Synodic Month: 2001 to 2100". astropixels.com. 8 November 2019.

Sources

Asmelash, Leah; Allan, David (30 July 2019). "A black moon is coming on July 31. Here's what that means". CNN.
Buick, Tony; Pugh, Philip (2011). How to Photograph the Moon and Planets with Your Digital Camera. Springer. ISBN 978-1-4419-5828-0.
Kelley, David H.; Milone, Eugene F. (2011). Exploring Ancient Skies: A Survey of Ancient and Cultural Astronomy (2nd ed.). Springer. ISBN 978-1-4419-7624-6.
Kutner, Marc L. (2003). Astronomy: A Physical Perspective. Cambridge University Press. p. 435. ISBN 978-0-521-52927-3.
Lynch, Mike. Texas Starwatch. Voyageur Press. ISBN 978-1-61060-511-3.
Naylor, John (2002). Out of the Blue: A 24-Hour Skywatcher's Guide. Cambridge University Press. ISBN 978-0-521-80925-2.
Ruggles, Clive L. N. (2005). Ancient Astronomy: An Encyclopedia of Cosmologies and Myth. ABC-CLIO. ISBN 978-1-85109-477-6.
Seidelmann, P. Kenneth, ed. (1992). Explanatory Supplement to the Astronomical Almanac. Mill Valley: University Science Books.

External links

Six Millennium Catalog of Phases of the Moon: Moon Phases from -1999 to +4000 (2000 BCE to 4000 CE).

Wikimedia Commons has media related to Lunar phases.

v t e The Moon
Outline
Physical properties	Internal structure Topography Atmosphere Gravity field Hill sphere Magnetic field Sodium tail Moonlight Earthshine
Orbit	Lunar distance Orbital elements Distance Perigee and apogee Libration Nodes Nodal period Precession Syzygy New moon Full moon Eclipses Lunar eclipse Total penumbral lunar eclipse Tetrad Solar eclipse Solar eclipses on the Moon Eclipse cycle Supermoon Tide Tidal force Tidal locking Tidal acceleration Tidal range Lunar station
Surface and features	Selenography Terminator Limb Hemispheres Near side Far side Poles North pole South pole Face Maria List Mountains Peak of eternal light Valleys Volcanic features Domes Calderas Lava tubes Craters List Ray systems Permanently shadowed craters South Pole–Aitken basin Soil swirls Rilles Wrinkle ridges Rocks Lunar basalt 70017 Changesite-(Y) Water Space weathering Micrometeorite Sputtering Quakes Transient lunar phenomenon Selenographic coordinate system
Science	Observation Libration Lunar theory Origin Giant-impact hypothesis Theia Lunar magma ocean Geology Timescale Late Heavy Bombardment Lunar meteorites KREEP Volcanism Experiments Lunar laser ranging ALSEP Lunar sample displays Apollo 11 Apollo 17 Lunar seismology
Exploration	Missions Apollo program Explorers Probes Landing Colonization Moonbase Tourism Lunar resources
Time-telling and navigation	Lunar calendar Lunisolar calendar Month Lunar month Nodal period Fortnight Sennight Lunar station Lunar distance
Phases and names	New Full Names Crescent Super and micro Blood Blue Black Dark Wet Tetrad
Daily phenomena	Moonrise Meridian passage Moonset
Related	Lunar deities Lunar effect Earth phase Moon illusion Pareidolia Man in the Moon Moon rabbit Craters named after people Artificial objects on the Moon Memorials on the Moon Moon in science fiction list Apollo era futuristic exploration Hollow Moon Moon landing conspiracy theories Moon Treaty "Moon is made of green cheese" Natural satellite Double planet Lilith (hypothetical second moon) Splitting of the Moon
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