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The Full Moon

The Full Moon is the most spectacular Moon phase when the entire face of the Moon is lit up.

Illustration image

The Full Moon.

When the side of the Moon we can see from Earth is fully lit up at Full Moon, the opposite side is in darkness, and vice versa at New Moon.

©iStockphoto.com/selimaksan

100% Illuminated

At Full Moon, the entire face of the Moon is illuminated by the Sun's rays and it can be bright enough to light up otherwise dark nights.

Technically, this primary Moon phase only lasts a moment, the instant when the Sun and the Moon are aligned on opposite sides of Earth (see illustration). So the exact time for Full Moon is during the day on parts of the planet.

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

Therefore, it can be difficult to tell the difference between a Full Moon and the last stage of a Waxing Gibbous Moon or the beginning of a Waning Gibbous Moon.

Earth in the Middle

Illustration of the Moon's position in space in relation to Earth and the Sun at Full Moon
The Moon's position in space at Full Moon.
The Full Moon appears in our night sky when the Sun and the Moon are aligned on opposite sides of Earth.
@timeanddate.com

The technical term for the Full Moon alignment is syzygy of the Sun-Earth-Moon-system.

When the side of the Moon we can see from Earth is fully lit up at Full Moon, the opposite side is in darkness, and vice versa at New Moon.

The Full Moon is visible in the sky approximately from sunset to sunrise. At the precise moment of the Full Moon alignment, the Moon is only visible in the night part of Earth, with a few exceptions.

A Primary Moon Phase

Full Moon is the 3rd of the 4 primary Moon phases which occur at specific moments in time. The other 3 are New Moon, First Quarter Moon, and Third Quarter Moon.

In addition, there are 4 intermediate phases which take up the time in between the primary phases. These are called Waxing Crescent Moon, Waxing Gibbous Moon, Waning Gibbous Moon, and Waning Crescent Moon.

Elliptical Orbit

The Moon orbits Earth counterclockwise on an elliptical path, and the same side of the Moon always faces Earth. However, over time, the Moon rocks slightly from north to south and wobbles a little from east to west. This motion, known as lunar libration, makes it possible to see up to 58% of the Moon’s surface from Earth, although only 50% at a time.

Supermoon and Micromoon

The point of the Moon's orbit closest to Earth is called perigee and the point farthest away is known as apogee. When the Full Moon comes close to the perigee, it is known as a Supermoon or Super Full Moon.

When a Full Moon is close to the apogee, it is called a Micromoon.

Higher Tides at Full Moon

The greatest difference between high and low tide is around Full Moon and New Moon. During these Moon phases, the gravitational forces of the Moon and the Sun combine to pull the ocean’s water in the same direction. These tides are known as spring tides or king tides.

Causes Lunar Eclipses

A bright red Moon during a total lunar eclipse against a black night sky.
A red Moon during a total lunar eclipse.
A bright red Moon during a total lunar eclipse on September 28, 2015.
Deanne Fortnam

Around 2 or 3 times a year, the Full Moon comes close to the lunar nodes. These are the points where the Moon's orbit crosses the ecliptic, which is the path of the Sun, seen from Earth. When this happens, Earth cast its shadow on the Full Moon, causing a lunar eclipse.

Solar eclipses, on the other hand, can only happen if the Moon comes close to the lunar nodes around New Moon.

Blue Moon Is a Full Moon

Most years have 12 Full Moons, 1 each month. However, our calendar is not perfectly synchronized with astronomical events. Therefore, every now and then, a year has 13 Full Moons. When this happens, at least 1 of those Full Moons will be Blue Moon.

Full Moon in Calendars

Calendar symbol for Full moon

The symbol for Full Moon in modern calendars is a completely white circle.

The other primary Moon phase symbols in calendars are:
Calendar symbol for New Moon = New Moon, Calendar symbol for First Quarter Moon = First Quarter, Calendar symbol for Third Quarter Moon = Third Quarter

Affects the Tides

The tides on Earth are mostly generated by the Moon’s gravitational pull from one side of Earth to the other. The Moon’s gravity can cause small ebbs and flows in the continents called land tides or solid Earth tides. These are greatest during the Full and New Moons because the Sun and Moon are aligned on the same or opposite sides of Earth.

The Full Moon in Culture

The Moon has influenced human culture for millennia, and the Full Moon phase in particular. The date for Easter Sunday, for example, is determined based on the Full Moon and the vernal equinox.

The Moon has also inspired the invention of countless deities, like the Roman goddess Luna or her Norse male counterpart Máni, who gave his name to Monday. And, even today, people use ancient Full Moon names, like Harvest Moon and Strawberry Moon.

Witches and Werewolves

Partygoers on the beach at night amongst neon lights in Haad Rin, Ko Pha Ngan, Thailand.
Full Moon Party on Koh Pha Ngan, Thailand.
Neon lights light up the otherwise overcast sky during a Full Moon Party on the island of Koh Pha Ngan, Thailand.
©iStockphoto.com/Phurinee

In the past, it was common to think that many forms of mental illness were caused by the Moon, hence the name lunatic. The Full Moon has even been held responsible for supernatural transformations, changing otherwise harmless men into ferocious werewolves.

Modern Full Moon Celebration

The Full Moon still inspires celebrations. One of the most famous gatherings these days is the monthly Full Moon party on Haad Rin beach on the island of Koh Pha Ngan, Thailand, where thousands of tourists gather every month.

Topics: Moon, Astronomy, Calendar, Eclipses

Next Full Moon

Jul 9, 2017 at 12:06 am

Previous Full Moon

Jun 9, 2017 at 9:09 am

Times for Full Moon can vary by time zone. Dates are based on the local time in Washington DC. Change location

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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

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The Moon

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

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Sun & Moon Photography

  1. Taking Pictures of the Sun
  2. Taking Pictures of the Moon
  3. Solar Eclipse Photography
  4. Lunar Eclipse Photography

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