FULL MOON
Full moon, one of eight lunar phases, in which the entire round illuminated face of the Moon is visible from Earth. Because the most sunlight reflects off the Moon and toward Earth during the full moon, it is typically regarded as the most striking lunar phase. Due to the Moon's glare, it is harder to see other celestial objects like planets and stars during and around the full moon night. It is also difficult to observe the surface of the Moon itself when it is full, as the light tends to wash out topographic features.
Given that one half
of the Moon always faces the Sun as it orbits, one half of the Moon is always
illuminated, and the other half is always dark.
As the Moon progresses through its orbit, the amount of the illuminated
lunar surface visible from Earth changes, creating the phases. The Moon appears full when it reaches the
halfway point of its orbit—that is, when it is directly opposite the Sun, with
Earth in between. The full moon rises at
sunset and sets at sunrise because it is opposite the Sun. The synodic month is
the duration of the lunar phase cycle, which lasts 29.5 days. Thus, the full
moon occurs typically once per calendar month, but when the full moon happens
within the first two days of a given month, a second full moon may occur within
the same month. This phenomenon, known
as a “blue moon,” occurs on average about once every 33 months, though there
have been years in which two blue moons have occurred.
An ellipse, or oblong
orbit, of the Moon around the Earth-Moon barycentre is not a perfect circle. As
a result, there is no set distance between the two bodies. When the Moon
reaches the point in orbit closest to Earth (perigee), it can appear from Earth
as much as 14 percent larger in the sky than at its farthest point
(apogee). When a full moon occurs close
to the perigee, it is often regarded as a supermoon, a term coined in the
1970s. This phenomenon usually occurs in
about four or five consecutive lunar cycles per year. The geometrical relationship between the
Moon, Earth, and the Sun can cause other night-sky phenomena, such as lunar
eclipses, which occur only during the full moon when the Moon travels into
Earth’s shadow, or umbra, and thus appears darker (and sometimes tinted red) in
the sky.
As the largest and
brightest object regularly seen in the sky besides the Sun, the full moon has
persisted as a symbol in legend, religion, and even agriculture across many
cultures. In Hinduism, for instance,
full moon days, or Purnima, are frequently marked by fasting. Full moon days
have historically been significant to followers of Buddhism, and full moon
rituals are common in Neo-Paganism and similar movements. In Europe, the full moon was believed to
trigger uncontrollable behaviour in what was known as the “lunar lunacy
effect,” which inspired tales of werewolves and other beasts that broke free
only under the full moon’s light. Today, the full moon is still associated with erratic behaviour and an increase in
crime rates, though these ideas are an urban legend.
Many cultures and civilizations across history have used the
moon cycles to keep track of passing time, and some gave names to the full
moons that often referenced the climate or agriculture of a given “month.” There are countless records and translations
of these names. In the English language
today, there is a set of 12 names for the full moons that occur within a year
(the 13th is called a blue moon). For
example, the January full moon is called the wolf moon, the March full moon is
called the worm moon, and the September full moon is called the full corn moon
or the harvest moon. Some of these names
probably came from Native Americans in North America, while others may have
come from Celts or people from medieval England.
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