Phase 5 of 8 Next: Monday 26 October 2026

The Full Moon

The whole disc lit, and the flattest it ever looks. With the Sun directly behind us there are no shadows to give the surface any relief.

Where to look: Rises at about sunset, is highest around midnight, sets at about sunrise. Up for the whole night and only for the night — a full moon at noon is not a thing.

The phase everybody wants and the worst one to look at. The lack of shadow removes the topography, the brightness ruins your dark adaptation in seconds, and through a telescope it is genuinely uncomfortable. It is also a moment rather than a night: the Moon is full at one instant, and looks full to the eye for a day either side.

Commonly muddled: Fullness is not about size. A full moon near perigee is a supermoon and one near apogee is not, and almost nobody can tell the difference without a photograph of each to compare.

#001Phases & orbitThe Moon is drifting away from Earth at about 3.8 centimetres a year, roughly the rate your fingernails grow.Earth's tidal bulge sits slightly ahead of the Moon because the planet spins faster than the Moon orbits. That…Lunar Laser Ranging, NASA/ILRS

#006GeologyThe Moon is not white. It reflects about 12% of the light that hits it, which makes it roughly as dark as worn asphalt.It looks brilliant because it's a grey object against a black sky, lit by an unfiltered Sun. Photograph the Moon…NASA Moon facts

#007ObservingA full moon isn't twice as bright as a half moon. It's about ten times brighter.Two things pile up at full. Half the visible disc is lit at first quarter, but it's lit at a slant, so every crater…NASA Moon facts

#008ObservingThe full moon is the worst night of the month to look at the Moon.With the Sun straight overhead in lunar terms, there are no shadows, so craters and mountains flatten into a bright…NASA Moon observing

#031ObservingA 'supermoon' really is bigger, about 14% wider and 30% brighter than a full moon at its farthest. You will almost certainly not notice.The orbit is an ellipse, so the distance swings between roughly 356,500 and 406,700 km. The difference is…NASA Moon facts

#032ObservingThe Moon looks enormous on the horizon and normal overhead. It is the same size in both. The effect is entirely in your head.Photograph it in both positions with the same lens and the discs measure identically, if anything the horizon Moon…NASA Moon facts

#034ObservingThe harvest moon isn't bigger or oranger. It rises unusually early for several nights running, and that's the whole trick.Around the September equinox the Moon's path meets the horizon at a shallow angle, so the usual 50-minute delay…U.S. Naval Observatory

#043GeologyThe bright streaks fanning across the full moon come from one crater. Tycho's rays reach 1,500 km from the impact.Tycho is young, about 108 million years old, which on the Moon counts as recent, so its ejecta hasn't yet been…Lunar Reconnaissance Orbiter

#045Earth & tidesThe biggest tides of the month arrive at new and full moon, when the Sun and Moon pull in line.The Sun raises tides too, about 46% as strong as the Moon's. When all three bodies line up the effects add, giving…NOAA tides and currents

#048Earth & tidesThere is no measurable full moon effect on births, crime, or emergency rooms. It has been checked many times.A 1985 meta-analysis pooled dozens of studies and found essentially nothing. The persistent belief is a good…Rotton & Kelly, Psychological Bulletin (1985)

#053ObservingA totally eclipsed Moon turns red because it's lit by every sunrise and sunset on Earth at once.Earth's shadow isn't truly black: our atmosphere bends and filters sunlight into it, stripping out blue. Standing…NASA eclipse resources

#054ObservingLunar eclipses are no more common than solar ones. You will still see far more of them in your life.A solar eclipse paints a shadow track a couple of hundred kilometres wide; you have to be in it. A lunar eclipse is…NASA eclipse resources

#055Strange but trueMoonbows are real. A bright full moon and falling rain will make a rainbow, though your eyes usually see it as white.The physics is identical to a solar rainbow, the light is just about 400,000 times fainter, and at that level your…NASA Moon observing

#060ObservingThe brightest spot on the Moon is a crater called Aristarchus. It's bright enough that people have mistaken it for activity on the surface.Aristarchus sits on a plateau of unusually reflective material and is geologically fresh, making it stand out…Lunar Reconnaissance Orbiter

#061Strange but trueThe face in the Moon is made of lava flows 3 billion years old. Different cultures see a rabbit, a woman, a toad, or a man carrying sticks.The dark maria are the same shapes for every human being on the planet, the Moon has kept the same face turned…Lunar and Planetary Institute

#065Strange but trueA blue moon isn't blue and the popular definition is a mistake, a 1946 magazine misreading that everyone liked too much to fix.The older, seasonal meaning is the third full moon in a season that has four. Sky & Telescope garbled it into 'the…Sky & Telescope, 1946 / 1999 correction

#079ObservingThe most common reason a meteor shower disappoints is not cloud. It's the Moon.A gibbous moon washes out everything but the brightest few meteors. Shower dates are fixed by Earth's orbit while…American Meteor Society

#092Strange but trueSri Lanka gives a public holiday on every full moon, which is twelve or thirteen days a year decided entirely by the Moon.Poya days mark the full moon in the Buddhist calendar and each one is a national holiday: shops close, alcohol is…Sri Lanka public holiday calendar

#146ObservingA total lunar eclipse is rated on the Danjon scale: 0 is so dark the Moon nearly vanishes, 4 is bright coppery orange with a bluish rim.The difference is Earth's atmosphere. Every ray reaching the eclipsed Moon has been filtered through our air, so…Danjon, L'Astronomie 35 (1921); NASA eclipse…

#149ObservingDuring a total lunar eclipse near sunrise or sunset it is sometimes possible to see the eclipsed Moon and the Sun in the sky at the same moment, which geometrically should be impossible.An eclipse means Earth is directly between them, so both cannot be above the horizon at once. Refraction cheats…Meeus, Mathematical Astronomy Morsels

#152ObservingA full moon shines at magnitude -12.7, which sounds dazzling until you compare it with the Sun at -26.7. The gap is a factor of about four hundred thousand.It is why moonlight will not warm you and will not let you read comfortably, despite being bright enough to cast a…NASA Moon facts

#166Earth & tidesOnce a year, a few nights after a particular full moon, hundreds of coral species along 2,000 kilometres of reef release their eggs within an hour of each other.Corals carry light-sensitive proteins called cryptochromes that respond to moonlight specifically, and the…Levy et al., Science 318, 467 (2007)…

The Full Moon

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The Full Moon

22 facts about this phase