Basics · 7 min read

The Moon’s phases – why the shadow moves

Half of the Moon is always lit. The only thing that changes is how much of the bright half we happen to see from here. Drag the slider below and see for yourself.

The moonposition.com team · updated 28 October 2026

From above · north pole The yellow dot is you. The dashed line shows where you’re looking – and how much of the Moon’s bright side faces you.

What you see from the northern hemisphere

Best seen

Rises, roughly

The shadow isn’t Earth’s

The Moon doesn’t shine by itself. It works like a giant, dusty mirror for sunlight – and just like Earth it always has a day side and a night side. The dark part we see is simply the Moon’s own night.

Many people think Earth’s shadow creeps across the Moon. But Earth’s shadow only reaches it during a lunar eclipse – and that only happens at full moon.

Myth: Earth’s shadow causes the phases. Then the Moon would have to sit in the shadow all month.

In fact: the side facing the Sun is always lit. We just see it from different angles.

Eight phases, one orbit

From new moon to new moon takes 29.5 days on average. The cycle is usually split into eight phases, but in reality it’s a smooth change: the shadow line moves a little every hour.

New moon day 0

Waxing crescent day ~3.7

First quarter day ~7.4

Waxing gibbous day ~11.1

Full moon day ~14.8

Waning gibbous day ~18.5

Last quarter day ~22.1

Waning crescent day ~25.8

Waxing or waning?

From the northern hemisphere there’s a simple rule: if the Moon is lit on the right it is growing, if it’s lit on the left it is shrinking. The waxing Moon is seen in the evening, the waning Moon in the morning.

Northern hemisphereThe waxing crescent is lit on the right

Near the equatorThe crescent lies flat, like a boat

AustraliaEverything mirrored – lit on the left

29.5 or 27.3 days?

Measured against the stars, the Moon orbits Earth in 27.3 days. But meanwhile Earth has moved about 27° along its orbit around the Sun. The Moon needs just over two more days to reach the same position relative to the Sun – only then is it new moon again.

Scale and angles exaggerated for clarity.

When is the Moon visible?

The phase also tells you the time of day. The full moon is opposite the Sun, so it rises roughly as the Sun sets. The new moon follows the Sun across the sky and is lost in daylight.

PhaseRisesBest seenSets

New moon ~06Not visible~18

First quarter ~12Afternoon and evening~24

Full moon ~18All night~06

Last quarter ~24Night and morning~12

Waning crescent ~03Dawn in the east~15

The times are approximate and vary a lot with the seasons at high latitudes. Winter full moons ride high in the sky – summer ones barely clear the southern horizon.

“Half of the Moon is always day. We just see different amounts of it.”

Earthshine – when the dark part glows

Look at a thin crescent a few days before or after new moon: often the rest of the Moon shows as a faint, ash-grey disc. That’s sunlight that bounced off Earth, lit up the Moon’s night and bounced back to you. Leonardo da Vinci was one of the first to explain it, in the early 1500s.

Test yourself

Which phase is the Moon in during a lunar eclipse?

Hint: think about where Earth’s shadow points.

Take the full Moon quiz →