A guide to the phases of the Moon, and also why the appearance changes night after ~ night from crescent to gibbous and earlier again.

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The Moon may appear to adjust shape, but in fact the bright surface you see and the ‘moonlight’ that reaches earth is in reality sunlight showing off the lunar surface. As the Moon orbits ours planet, its differing position method that the sun lights up various regions, creating the illusion that the Moon is an altering shape over time.

The best way of obtaining to know the lunar phases is to consistently go out on a clear night once the Moon is in the sky and also observe it. For more on this, read our overview on exactly how to observe the Moon.

On mean 384,400km native Earth, it’s stunning to the naked eye and also through binoculars or a small telescope, spectacular. It’s also a good target come photograph. For an ext on this, check out our overview on exactly how to picture the Moon or our beginners’ guide to astrophotography.


The phases the the Moon. The within circle mirrors what the Moon looks favor seen from above its phibìc pole, if the external circle reflects the step we check out from earth at that time. Credit: BBC sky at Night Magazine
The Moon appears serene however it is hurtling eastward travel at 3,682 km/h and, since its nearly circular orbit is tipped a just 5° family member to Earth’s, it much more or less follows the ecliptic (the Sun’s evident path) across the sky.

You may have noticed that the Moon always keeps the same confront turned in the direction of us. This is because it rotates when on that is axis in precisely the same time that takes come orbit planet – 27 days and seven hours.


Moon phases in the southerly hemisphere luis Rojas M, Santiago, Chile, 13 October – 17 October 2018. Equipment: Canon EOS Rebel T6i, check out Scientific 102mm ED refractor, iOptron iEQ30 agree mount.
This synchronisation is called tidal locking and also is a an outcome of earth gravitational impact on the young Moon when it to be forming.

During that is elliptical journey about Earth, the Moon moves v ‘phases’, the term we usage to describe how much of the lunar disc shows up illuminated as watched from Earth.

This elliptical orbit, merged with the phases is also what leader to the appearance of a so-called supermoon.

In fact, the Moon is always fifty percent lit, we simply don’t check out it that way. Everything phase we’re seeing, the opposite step is keep going on the far side that the Moon.

And while we only ever before see one terminator (the name provided to the splitting line between the light and dark components of the lunar surface) sweeping appropriate to left across the lunar bowl at any type of time, there are actually two of them circumnavigating the Moon exactly 180° apart; the morning terminator (which ushers in the lunar day) and the evening terminator (which brings the night behind it).

So sorry, Pink Floyd, there is no permanently dark next of the Moon.

The phases that the Moon

What many civilization don’t realise (even though it’s completely logical), is the there’s also a relationship in between the Moon’s phases and also moonrise times.

New Moon


new Moon (1% visibility) by boy name Marthadinata.
In this phase, our satellite is invisible. V the Sun and also Moon ~ above the same side of Earth, they rise together however we cannot view the Moon as it’s surprise in the Sun’s glare. Yes sir not lot to check out anyway, together its confront towards united state is completely in shadow.

Waxing crescent

Credit: Sarah and also Simon Fisher.
Continuing that is journey, the Moon’s western (right) edge becomes sunlit to develop a sliver-thin crescent. The morning terminator starts its creep that 15.5km/h from west come east.

First quarter

Credit: Paul Licorish
This one confuses non-astronomers, due to the fact that it plainly looks like fifty percent a Moon, however it’s called a quarter Moon. That’s because the terminator has completed a quarter (90°) the its 360° journey roughly the Moon.

By this logic a complete Moon should be referred to as a half Moon, but that’s simply silly, right? In this phase, the Moon rises in ~ noon and also sets in ~ midnight. Follow me the terminator, low-angled sunshine creates long shadows, throwing nearby crater and mountains right into sharp relief – perfect because that lunar observations.

Waxing gibbous

Credit: Harvey Scoot.
In this step the Moon is almost totally illuminated. The daylight area shows up egg-shaped (gibbous) and also is boosting in size (waxing) daily.

Full Moon

full Moon at Perigee by Tom Howard
Halfway v the morning terminator’s journey, the Moon is top top the opposite side of earth from the Sun, through its close to side completely illuminated and also dazzling. Shadow-less, bleached and also flat-looking, it’s not an excellent for observation – that’s a shame because in this step it rises as the sun sets, sets as the sun rises and is visible all night long!

Waning gibbous

Credit: Sarah and also Simon Fisher
The Moon’s western edge is gift consumed through darkness together the evening terminator comes into view. The sunlit, egg-shaped area is diminishing (waning).

Last quarter

Credit: Andrew McNaught.
It’s seven days and also nine hours because full Moon and, currently 90° west of the Sun, simply the Moon’s eastern (left) fifty percent is illuminated. At this step it rises in ~ midnight and sets at noon and, prefer the an initial quarter phase, uses staggering views.

Waning crescent

Credit: Anadolu agency / Getty Images
With simply the eastern edge sunlit you will do it admire a beautiful ‘C-shaped’ crescent. Diminishing everyday (waning) that will soon disappear as the lunar cycle concludes and also the Moon return to ‘new’. When the Moon may keep the same face turned to us, it stays a daily changing delight come observe.

Lunar libration
many thanks to lunar libration we can observe slightly an ext than half of the Moon’s surface. Credit: Pete Lawrence
Over the food of a lunar cycle, the Moon all at once wobbles both latitudinally and also longitudinally. These oscillations are recognized as librations.

Libration in latitude – nodding – occurs because the Moon’s axis is contempt inclined loved one to Earth’s, allowing us come peer simply a little over its north and, later on in the month, south poles.

Libration the longitude – shiver – occurs due to the fact that the Moon travels fastest when closest to Earth and also slowest once farthest away.

Daily (diurnal) libration occurs due to the fact that of ours planet’s rotation.

We watch the Moon indigenous slightly different perspectives as soon as it rises and when it sets, and also this difference in perspective manifests together a slight apparent rotation in the satellite, very first to the west and also then to the east.

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The merged effect of all the above means that instead of seeing simply 50 per cent that the Moon, with time we actually obtain to see around 59 per cent.


Jane green is a other of the royal Astronomical society and author of the Haynes Astronomy Manual

Phases of the Moon by Tom Chitson, Woking, Surrey, UK. Equipment: sky Watcher explorer 130p, Sony Cybershot W210
Moon Montage by sarah & Simon Fisher, Bromsgrove, Worcestershire, UK. Equipment: Canon 600D, Mak 127mm scope
Moontage by buy it & Simon Fisher, Bromsgrove, Worcestershire, UK. Equipment: Canon 600D, Mak 127mm scope
Moontage by sarah & Simon Fisher, Bromsgrove, Worcestershire, UK. Equipment: Canon 600D, Mak 127mm scope


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