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The Phases of the Moon

Half of the Moon’s surface is always illuminated by sunlight. However, just how much of that light we can see from our point of view on Earth varies every day and this is what we refer to as a Moon phase.

Illustration showing the Moon phases based on Moon images from NASA.

Different phases of the Moon.

Illustration showing the visible Moon phases based on images from NASA.

©iStockphoto.com/Delpixart

Sun Lights Up the Moon

The Moon does not radiate its own light, but the Moon's surface reflects the Sun’s rays.

Primary and Intermediate Phases

In Western Culture, we divide the lunar month into 4 primary and 4 intermediate Moon phases.

Technically, the primary Moon phases occur at a specific moment in time, and the intermediate Moon phases take up the time in between.

New Moon

Illustration of the Moon's position in space in relation to Earth and the Sun at New Moon.
The Moon's position in space at New Moon.
The Sun (left), the Moon (middle), and Earth (right) at New Moon. The arrows show the direction of the sun's rays.
@timeanddate.com

New Moon is the 1st primary phase and it occurs the moment when the Sun and Moon are aligned, with the Sun and Earth on opposite sides of the Moon.

A New Moon cannot normally be seen from Earth since only the dark side of the Moon faces our planet at this point. Sometimes, if the New Moon is close to the Lunar nodes of its path, it can cause a Solar Eclipse.

The greatest difference between high and low tide, also known as spring tides, takes place around New Moon and Full Moon.

Waxing Crescent Moon

The moment a thin sliver of the Moon becomes visible after New Moon is the beginning of the first intermediate phase, the Waxing Crescent Moon.

In the past, this used to be called New Moon while the darkest phase was called Dark Moon. This traditional definition of New Moon is still in use in some cultures, defining the beginning of the months for instance in the Islamic calendar.

The rest of the Moon is also sometimes faintly visible during most of this phase because Earth also reflects sunlight onto the Moon, a phenomenon called earthshine.

First Quarter Moon

Illustration of the Moon's position in space in relation to Earth and the Sun at First Quarter Moon
First Quarter Moon is the 2nd primary phase.
First Quarter Moon is also called Half Moon as we can see exactly half of the Moons surface illuminated.
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First Quarter Moon is the 2nd primary Moon phase and it is defined as the moment the Moon has reached the 1st quarter of its orbit around Earth, hence the name. It is also called Half Moon as we can see exactly 50% of the Moon's surface illuminated. Whether you see the left or right half illuminated, depends on several factors, including your location.

The smallest difference between high and low tide, also known as neap tides, occurs around the 2 Quarter Moons.

Waxing Gibbous Moon

The 2nd intermediate phase, the Waxing Gibbous Moon, lasts until the next primary phase. Waxing means that it is getting bigger. Gibbous refers to the shape, which is larger than the semicircle shape of the Moon at First Quarter, but smaller than a full circle.

Full Moon

Illustration of the Moon's position in space in relation to Earth and the Sun at Full Moon
Full Moon is the brightest phase.
Full Moon; The Moon has completed half its orbit around Earth and the part that faces Earth is 100% illuminated.
@timeanddate.com

The Full Moon appears in the night sky when the Sun and the Moon are aligned on opposite sides of Earth.

Technically, this alignment only lasts a moment. However, the Moon can appear to be full a day before or after while more than 98% of the Moon's disc is illuminated.

When a Full Moon occasionally passes through Earth's shadow, it will cause a lunar eclipse.

When the Full Moon comes close to the points of its orbit that are closest or farthest away from Earth, we call it a Supermoon or Micromoon, respectively.

Waning Gibbous Moon

The next intermediate Moon phase is the Waning Gibbous Moon. The portion of the visible half of the Moon illuminated decreases during this period.

Third Quarter Moon

Illustration of the Moon's position in space in relation to Earth and the Sun at Third Quarter Moon.
Third Quarter Moon is the last primary phase.
At Third Quarter Moon, we can see half of the Moon's surface lit up.
@timeanddate.com

The Third Quarter Moon occurs the moment the opposite half of the Moon is illuminated compared to the First Quarter Moon.

Waning Crescent Moon

The Waning Crescent Moon. The Sun illuminates less than half of the visible part of the Moon during this Moon phase and you can sometimes see earthshine on the rest of the Moon towards the end.

Topics: Astronomy, Moon

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The Moon Phases

  1. The Lunar Month
  2. New Moon
  3. Waxing Crescent Moon
  4. First Quarter Moon
  5. Waxing Gibbous Moon
  6. Full Moon
  7. Waning Gibbous Moon
  8. Third Quarter Moon
  9. Waning Crescent Moon

Moon Phases

Moon Location

Where is the moon now?

The Moon

  1. What Is a Supermoon?
  2. The Moon Illusion
  3. The Moon Phases
  4. The Moon's Effect on Tides
  5. What Is a Micro Moon?
  6. How Can Full Moon Be in the Daytime?
  7. Is a Blue Moon Blue?
  8. The Moon's Orbit
  9. The Far Side of the Moon
  10. What Is a Black Moon?
  11. What Are Moonbows?
  12. Full Moon Names
  13. Taking pictures of the Moon

Moon index

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