Full moon in the context of Panguni

A lunar phase or Moon phase is the apparent shape of the Moon's day and night phases of the lunar day as viewed from afar. Because the Moon is tidally locked to Earth, the cycle of phases takes one lunar month and moves across the same side of the Moon, which always faces Earth. In common usage, the four major phases are the new moon, the first quarter, the full moon and the last quarter; the four minor phases are waxing crescent, waxing gibbous, waning gibbous, and waning crescent. A lunar month is the time between successive recurrences of the same phase: due to the eccentricity of the Moon's orbit, this duration is not perfectly constant but averages about 29.5 days.

The appearance of the Moon (its phase) gradually changes over a lunar month as the relative orbital positions of the Moon around Earth, and Earth around the Sun, shift. The visible side of the Moon is sunlit to varying extents, depending on the position of the Moon in its orbit, with the sunlit portion varying from 0% (at new moon) to nearly 100% (at full moon).

A lunar calendar is a calendar based on the monthly cycles of the Moon's phases (synodic months, lunations), in contrast to solar calendars, whose annual cycles are based on the solar year, and lunisolar calendars, whose lunar months are brought into alignment with the solar year through some process of intercalation – such as by insertion of a leap month. The most widely observed lunar calendar is the Islamic calendar. The details of when months begin vary from calendar to calendar, with some using new, full, or crescent moons and others employing detailed calculations.

Since each lunation is approximately 29+1⁄2 days, it is common for the months of a lunar calendar to alternate between 29 and 30 days. Since the period of 12 such lunations, a lunar year, is 354 days, 8 hours, 48 minutes, 34 seconds (354.36707 days), lunar calendars are 11 to 12 days shorter than the solar year. In lunar calendars, which do not make use of lunisolar calendars' intercalation, the lunar months cycle through all the seasons of a solar year over the course of a 33–34 lunar-year cycle (see, e.g., list of Islamic years).

In lunar calendars, a lunar month is the time between two successive syzygies of the same type: new moons or full moons. The precise definition varies, especially for the beginning of the month.

The Roman calendar was the calendar used by the Roman Kingdom and Roman Republic. Although the term is primarily used for Rome's pre-Julian calendars, it is often used inclusively of the Julian calendar established by Julius Caesar in 46 BC.

According to most Roman accounts, their original calendar was established by their legendary first king Romulus. It consisted of ten months, beginning in spring with March and leaving winter as an unassigned span of days before the next year. These months each had 30 or 31 days and ran for 38 nundinal cycles, each forming a kind of eight-day week—nine days counted inclusively in the Roman manner—and ending with religious rituals and a public market. This fixed calendar bore traces of its origin as an observational lunar one. In particular, the most important days of each month—its kalends, nones, and ides—seem to have derived from the new moon, the first-quarter moon, and the full moon respectively. To a late date, the College of Pontiffs formally proclaimed each of these days on the Capitoline Hill and Roman dating counted down inclusively towards the next such day in any month. (For example, the year-end festival of Terminalia on 23 February was called VII. Kal. Mart., the 6th day before the March kalends.)

Tidal range is the difference in height between high tide and low tide. Tides are the rise and fall of sea levels caused by gravitational forces exerted by the Moon and Sun, by Earth's rotation and by centrifugal force caused by Earth's progression around the Earth-Moon barycenter. Tidal range depends on time and location.

Larger tidal range occur during spring tides (spring range), when the gravitational forces of both the Moon and Sun are aligned (at syzygy), reinforcing each other in the same direction (new moon) or in opposite directions (full moon). The largest annual tidal range can be expected around the time of the equinox if it coincides with a spring tide. Spring tides occur at the second and fourth (last) quarters of the lunar phases.

Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria. They typically form compact colonies of many identical individual polyps. Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton.

A coral "group" is a colony of very many genetically identical polyps. Each polyp is a sac-like animal typically only a few millimeters in diameter and a few centimeters in height. A set of tentacles surround a central mouth opening. Each polyp excretes an exoskeleton near the base. Over many generations, the colony thus creates a skeleton characteristic of the species which can measure up to several meters in size. Individual colonies grow by asexual reproduction of polyps. Corals also breed sexually by spawning: polyps of the same species release gametes simultaneously overnight, often around a full moon. Fertilized eggs form planulae, a mobile early form of the coral polyp which, when mature, settles to form a new colony.

The Nebra sky disc (German: Himmelsscheibe von Nebra, pronounced [ˈhɪml̩sˌʃaɪbə fɔn ˈneːbra]) is a bronze disc of around 30 cm (12 in) diameter and a weight of 2.2 kg (4.9 lb), having a blue-green patina and inlaid with gold symbols. These symbols are interpreted generally as the Sun or full moon, a lunar crescent, and stars, including a cluster of seven stars, axiomatically interpreted as the Pleiades.

Two golden arcs along the sides (one now missing) are thought to have marked the angle between the solstices. Another arc at the bottom with internal parallel lines is usually interpreted as a solar boat with numerous oars, although some authors have also suggested that it may represent a rainbow, the Aurora Borealis, a comet, or a sickle.

A circle is a shape consisting of all points in a plane that are at a given distance from a given point, the centre. The distance between any point of the circle and the centre is called the radius. The length of a line segment connecting two points on the circle and passing through the centre is called the diameter. A circle bounds a region of the plane called a disc.

The circle has been known since before the beginning of recorded history. Natural circles are common, such as the full moon or a slice of round fruit. The circle is the basis for the wheel, which, with related inventions such as gears, makes much of modern machinery possible. In mathematics, the study of the circle has helped inspire the development of geometry, astronomy and calculus.

Paksha (Sanskrit: पक्ष, romanized: pakṣa) refers to a fortnight period consisting of various lunar phases in a month of the Hindu lunar calendar. Literally meaning "side" in Sanskrit, it refers to the periods between amavasya (new moon) and purnima (full moon), and vice versa.

A lunar month in the Hindu calendar has two fortnights, with each fortnight subdivided into lunar days called tithis. A paksha consists of 15 such tithis, each of which correspond to a 12-degree angular motion of the Moon. The fortnight between amavasya and purnima is called as Shukla Paksha (bright side) or Gaura Paksha, which corresponds to the period of the waxing moon. The second fortnight is called Krishna Paksha (dark side) or Vadhya Paksha' and corresponds to the period of the waning moon. Amavasya corresponds to the period when the Moon is within 12 degrees of angular distance from the Sun before their conjunction.

Chaitra (Sanskrit: चैत्र, romanized: Caitra) is the first month of the Hindu lunar calendar and the Indian national calendar. The name of the month is derived from the position of the Moon near the Chitra nakshatra (star) on the full moon day. The month corresponds to spring (Vasanta) season and falls in March–April in the Gregorian calendar.

In the Hindu solar calendar, it corresponds to the last month of Mina and begins with the Sun's entry into Pisces. It corresponds to Choitro, the last month in the Bengali calendar, and Chait, the last month in the Nepali calendar (Vikram Samvat). In the Tamil calendar, it corresponds to the third month of Chittirai, falling in the Gregorian months of April–May.

As a moveable feast, the date of Easter is determined in each year through a calculation known as computus paschalis (Latin for 'Easter computation') – often simply Computus – or as paschalion particularly in the Eastern Orthodox Church. Easter is celebrated on the first Sunday after the Paschal full moon (a mathematical approximation of the first astronomical full moon, on or after 21 March – itself a fixed approximation of the March equinox). Determining this date in advance requires a correlation between the lunar months and the solar year, while also accounting for the month, date, and weekday of the Julian or Gregorian calendar. The complexity of the algorithm arises because of the desire to associate the date of Easter with the date of the Jewish feast of Passover which, Christians believe, is when Jesus was crucified.

It was originally feasible for the entire Christian Church to receive the date of Easter each year through an annual announcement by the pope. By the early third century, however, communications in the Roman Empire had deteriorated to the point that the church put great value in a system that would allow the clergy to determine the date for themselves, independently yet consistently. Additionally, the church wished to eliminate dependencies on the Hebrew calendar, by deriving the date for Easter directly from the March equinox.

In folklore, a werewolf (from Old English werwulf 'man-wolf'), or occasionally lycanthrope (from Ancient Greek λυκάνθρωπος 'wolf-human'), is an individual who can shapeshift into a wolf or therianthropic hybrid wolf–humanlike creature, either voluntarily or involuntarily due to a curse or other affliction. In modern fiction, especially film, transformations are often depicted as triggered by the full moon and transmitted by a bite or scratch from another werewolf. Early sources for belief in this ability or affliction, called lycanthropy, are Petronius (27–66) and Gervase of Tilbury (1150–1228).

The werewolf is a widespread concept in European folklore, existing in many variants, which are related by a common development of a Christian interpretation of underlying European folklore developed during the Middle Ages. From the early modern period, werewolf beliefs spread to the Western Hemisphere with colonialism. Belief in werewolves developed in parallel to the belief in witches during the late Middle Ages and the early modern period. Like the witchcraft trials as a whole, the trial of supposed werewolves emerged in what is now Switzerland, especially the Valais and Vaud, in the early 15th century and spread throughout Europe in the 16th, peaking in the 17th and subsiding by the 18th century.

Andromeda is one of the 48 constellations listed by the 2nd-century Greco-Roman astronomer Ptolemy, and one of the 88 modern constellations. Located in the northern celestial hemisphere, it is named for Andromeda, daughter of Cassiopeia, in the Greek myth, who was chained to a rock to be eaten by the sea monster Cetus. Andromeda is most prominent during autumn evenings in the Northern Hemisphere, along with several other constellations named for characters in the Perseus myth. Because of its northern declination, Andromeda is visible only north of 40° south latitude; for observers farther south, it always lies below the horizon. It is one of the largest constellations, with an area of 722 square degrees. This is over 1,400 times the size of the full moon, 55% of the size of the largest constellation, Hydra, and over 10 times the size of the smallest constellation, Crux.

Its brightest star, Alpheratz (Alpha Andromedae), is a binary star that has also been counted as a part of Pegasus, while Gamma Andromedae (Almach) is a colorful binary and a popular target for amateur astronomers. With a variable brightness similar to Alpheratz, Mirach (Beta Andromedae) is a red giant, its color visible to the naked eye. The constellation's most obvious deep-sky object is the naked-eye Andromeda Galaxy (M31, also called the Great Galaxy of Andromeda), the closest spiral galaxy to the Milky Way and one of the brightest Messier objects. Several fainter galaxies, including M31's companions M110 and M32, as well as the more distant NGC 891, lie within Andromeda. The Blue Snowball Nebula, a planetary nebula, is visible in a telescope as a blue circular object.