A lunar eclipse occurs when the

Moon The Moon is Earth's only natural satellite. It is the fifth largest satellite in the Solar System and the largest and most massive relative to its parent planet, with a diameter about one-quarter that of Earth (comparable to the width of ...

moves into the

Earth's shadow Earth's shadow (or Earth shadow) is the shadow that Earth itself casts through its atmosphere and into outer space, toward the antisolar point. During the twilight period (both early dusk and late dawn), the shadow's visible fringe – sometimes ...

. Such alignment occurs during an

eclipse season An eclipse season is the period, roughly every six months, when eclipses occur. Eclipse seasons are the result of the axial parallelism of the Moon's tilted orbital plane ( tilted five degrees to the Earth's orbital plane), just as Earth's we ...

, approximately every six months, during the

full moon The full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (when the ecliptic coordinate system, ecliptic longitudes of the Sun and Moon opp ...

phase, when the Moon's orbital plane is closest to the plane of the Earth's orbit. This can occur only when the

Sun The Sun is the star at the center of the Solar System. It is a nearly perfect ball of hot plasma, heated to incandescence by nuclear fusion reactions in its core. The Sun radiates this energy mainly as light, ultraviolet, and infrared radi ...

, Earth, and Moon are exactly or very closely aligned (in syzygy) with Earth between the other two, which can happen only on the night of a

when the Moon is near either lunar node. The type and length of a lunar eclipse depend on the Moon's proximity to the lunar node. When the moon is totally eclipsed by the Earth, it takes on a reddish color that is caused by the planet when it completely blocks direct

sunlight Sunlight is a portion of the electromagnetic radiation given off by the Sun, in particular infrared, visible, and ultraviolet light. On Earth, sunlight is scattered and filtered through Earth's atmosphere, and is obvious as daylight when t ...

from reaching the Moon surface, as only the light reflected from the lunar surface has been

refracted In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomeno ...

Earth's atmosphere The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...

. This light appears reddish due to the

Rayleigh scattering Rayleigh scattering ( ), named after the 19th-century British physicist Lord Rayleigh (John William Strutt), is the predominantly elastic scattering of light or other electromagnetic radiation by particles much smaller than the wavelength of th ...

of blue light, the same reason sunrise and sunsets are more orange than during the day. Unlike a

solar eclipse A solar eclipse occurs when the Moon passes between Earth and the Sun, thereby obscuring the view of the Sun from a small part of the Earth, totally or partially. Such an alignment occurs during an eclipse season, approximately every six month ...

, which can only be viewed from a relatively small area of the world, a lunar eclipse may be viewed from anywhere on the

night Night (also described as night time, unconventionally spelled as "nite") is the period of ambient darkness from sunset to sunrise during each 24-hour day, when the Sun is below the horizon. The exact time when night begins and ends depends o ...

side of Earth. A total lunar eclipse can last up to nearly 2 hours, while a total solar eclipse lasts only up to a few minutes at any given place, because the Moon's

shadow A shadow is a dark area where light from a light source is blocked by an opaque object. It occupies all of the three-dimensional volume behind an object with light in front of it. The cross section of a shadow is a two-dimensional silhouette, o ...

is smaller. Also unlike solar eclipses, lunar eclipses are safe to view without any

eye protection Eye protection is protective gear for the eyes, and sometimes face, designed to reduce the risk of injury. Examples of risks requiring eye protection can include: impact from particles or debris, light or radiation, wind blast, heat, sea sp ...

or special precautions. The symbol for a lunar eclipse (or indeed any body in the shadow of another) is file:Lunar eclipse symbol.svg (U+1F776 🝶). For the date of the next eclipse, see .

Types of lunar eclipse

can be divided into two distinctive parts: the

umbra The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast. Th ...

and

penumbra The umbra, penumbra and antumbra are three distinct parts of a shadow, created by any light source after impinging on an opaque object. Assuming no diffraction, for a collimated beam (such as a point source) of light, only the umbra is cast. Th ...

. Earth totally occludes direct

solar radiation Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre ( ...

within the umbra, the central region of the shadow. However, since the Sun's diameter appears about one-quarter of Earth's in the lunar sky, the planet only partially blocks direct

within the penumbra, the outer portion of the shadow.

Penumbral lunar eclipse

This occurs when the Moon passes through Earth's penumbra. The penumbra causes a subtle dimming of the lunar surface, which is only visible to the naked eye when about 70% of the Moon's diameter has immersed into Earth's penumbra. A special type of penumbral eclipse is a ''

total penumbral lunar eclipse A total penumbral lunar eclipse is a lunar eclipse that occurs when the Moon becomes completely immersed in the penumbral cone of the Earth without touching the umbra. The path for the Moon to pass within the penumbra and outside the umbra is ...

'', during which the Moon lies exclusively within Earth's penumbra. Total penumbral eclipses are rare, and when these occur, the portion of the Moon closest to the umbra may appear slightly darker than the rest of the lunar disk.

Partial lunar eclipse

This occurs when only a portion of the Moon enters Earth's umbra, while a ''total lunar eclipse'' occurs when the entire Moon enters the planet's umbra. The Moon's average

orbital speed In gravitationally bound systems, the orbital speed of an astronomical body or object (e.g. planet, moon, artificial satellite, spacecraft, or star) is the speed at which it orbits around either the barycenter or, if one body is much more mas ...

is about , or a little more than its diameter per hour, so totality may last up to nearly 107 minutes. Nevertheless, the total time between the first and the last contacts of the Moon's limb with Earth's shadow is much longer and could last up to 236 minutes.

Total lunar eclipse

This occurs when the Moon falls entirely within the Earth's umbra. Just prior to complete entry, the brightness of the lunar limb-- the curved edge of the Moon still being hit by direct sunlight-- will cause the rest of the Moon to appear comparatively dim. The moment the Moon enters a complete eclipse, the entire surface will become more or less uniformly bright. Later, as the Moon's opposite limb is struck by sunlight, the overall disk will again become obscured. This is because as viewed from the Earth, the brightness of a lunar limb is generally greater than that of the rest of the surface due to reflections from the many surface irregularities within the limb: sunlight striking these irregularities is always reflected back in greater quantities than that striking more central parts, and is why the edges of full moons generally appear brighter than the rest of the lunar surface. This is similar to the effect of

velvet Weave details visible on a purple-colored velvet fabric Velvet is a type of woven tufted fabric in which the cut threads are evenly distributed, with a short pile, giving it a distinctive soft feel. By extension, the word ''velvety'' means ...

fabric over a convex curved surface which to an observer will appear darkest at the center of the curve. It will be true of any planetary body with little or no atmosphere and an irregular cratered surface (e.g., Mercury) when viewed opposite the Sun.

Central lunar eclipse

This is a total lunar eclipse during which the Moon passes through the centre of Earth's shadow, contacting the

antisolar point The antisolar point is the abstract point on the celestial sphere directly opposite the Sun from an observer's perspective. This means that the antisolar point lies above the horizon when the Sun is below it, and vice versa. On a sunny day, ...

. This type of lunar eclipse is relatively rare. The relative distance of the Moon from Earth at the time of an eclipse can affect the eclipse's duration. In particular, when the Moon is near

apogee An apsis (; ) is the farthest or nearest point in the orbit of a planetary body about its primary body. For example, the apsides of the Earth are called the aphelion and perihelion. General description There are two apsides in any ellip ...

, the farthest point from Earth in its orbit, its

is the slowest. The diameter of Earth's umbra does not decrease appreciably within the changes in the Moon's orbital distance. Thus, the concurrence of a totally eclipsed Moon near apogee will lengthen the duration of totality.

Selenelion

A ''selenelion'' or ''selenehelion'', also called a ''horizontal eclipse'', occurs where and when both the Sun and an eclipsed Moon can be observed at the same time. The event can only be observed just before

sunset Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from everywhere on Earth (except the North and South poles), the equinox Sun sets due west at the moment of both the spring ...

or just after

sunrise Sunrise (or sunup) is the moment when the upper rim of the Sun appears on the horizon in the morning. The term can also refer to the entire process of the solar disk crossing the horizon and its accompanying atmospheric effects. Terminology Al ...

, when both bodies will appear just above opposite

horizon The horizon is the apparent line that separates the surface of a celestial body from its sky when viewed from the perspective of an observer on or near the surface of the relevant body. This line divides all viewing directions based on whether i ...

s at nearly opposite points in the sky. A selenelion occurs during every total lunar eclipse-- it is an experience of the ''observer'', not a planetary ''event'' separate from the lunar eclipse itself. Typically, observers on Earth located on high mountain ridges undergoing

false sunrise A false sunrise is any of several atmospheric optical phenomena in which the Sun appears to have risen, but is actually still some distance below the horizon. A number of different atmospheric conditions can be responsible for this effect, all ...

false sunset A false sunset can refer to one of two related atmospheric optical phenomena, in which either (1) the Sun appears to be setting into or to have set below the horizon while it is actually still some height above the horizon, or (2) the Sun has alr ...

''at the same moment of a total lunar eclipse'' will be able to experience it. Although during selenelion the Moon is completely within the Earth's umbra, both it and the Sun can be observed in the sky because

atmospheric refraction Atmospheric refraction is the deviation of light or other electromagnetic wave from a straight line as it passes through the atmosphere due to the variation in air density as a function of height. This refraction is due to the velocity of ligh ...

causes each body to appear higher (i.e., more central) in the sky than its true geometric planetary position.

Timing

The timing of total lunar eclipses is determined by what are known as its "contacts" (moments of contact with Earth's shadow): * ''P1'' (''First contact''): Beginning of the penumbral eclipse. Earth's penumbra touches the Moon's outer limb. * ''U1'' (''Second contact''): Beginning of the partial eclipse. Earth's umbra touches the Moon's outer limb. * ''U2'' (''Third contact''): Beginning of the total eclipse. The Moon's surface is entirely within Earth's umbra. * ''Greatest eclipse'': The peak stage of the total eclipse. The Moon is at its closest to the center of Earth's umbra. * U3 (''Fourth contact''): End of the total eclipse. The Moon's outer limb exits Earth's umbra. * ''U4'' (''Fifth contact''): End of the partial eclipse. Earth's umbra leaves the Moon's surface. * ''P4'' (''Sixth contact''): End of the penumbral eclipse. Earth's penumbra no longer makes contact with the Moon.

Danjon scale

The following scale (the

Danjon scale The Danjon scale is a five-point scale useful for measuring the appearance and luminosity of the Moon during a total lunar eclipse. It was proposed by André-Louis Danjon in 1921, when postulating that the brightness of a lunar eclipse was rela ...

) was devised by

André Danjon André — sometimes transliterated as Andre — is the French and Portuguese form of the name Andrew, and is now also used in the English-speaking world. It used in France, Quebec, Canada and other French-speaking countries. It is a variation ...

for rating the overall darkness of lunar eclipses: * ''L'' = 0: Very dark eclipse. Moon almost invisible, especially at mid-totality. * ''L'' = 1: Dark eclipse, gray or brownish in coloration. Details distinguishable only with difficulty. * ''L'' = 2: Deep red or rust-colored eclipse. Very dark central shadow, while outer edge of umbra is relatively bright. * ''L'' = 3: Brick-red eclipse. Umbral shadow usually has a bright or yellow rim. * ''L'' = 4: Very bright copper-red or orange eclipse. Umbral shadow is bluish and has a very bright rim.

Lunar versus solar eclipse

Lunar eclipse oct 8 2014 Minneapolis 4 46am

There is often confusion between a solar eclipse and a lunar eclipse. While both involve interactions between the Sun, Earth, and the Moon, they are very different in their interactions. The Moon does not completely darken as it passes through the umbra because of the

refraction In physics, refraction is the redirection of a wave as it passes from one medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most commonly observed phenomeno ...

into the shadow cone; if Earth had no atmosphere, the Moon would be completely dark during the eclipse. The reddish coloration arises because sunlight reaching the Moon must pass through a long and dense layer of Earth's atmosphere, where it is scattered. Shorter

wavelength In physics, the wavelength is the spatial period of a periodic wave—the distance over which the wave's shape repeats. It is the distance between consecutive corresponding points of the same phase on the wave, such as two adjacent crests, tro ...

s are more likely to be scattered by the air molecules and small particles; thus, the longer wavelengths predominate by the time the light rays have penetrated the atmosphere. Human vision perceives this resulting light as

red Red is the color at the long wavelength end of the visible spectrum of light, next to orange and opposite violet. It has a dominant wavelength of approximately 625–740 nanometres. It is a primary color in the RGB color model and a secondar ...

. This is the same effect that causes

s and

s to turn the sky a reddish color. An alternative way of conceiving this scenario is to realize that, as viewed from the Moon, the Sun would appear to be setting (or rising) behind Earth. The amount of refracted light depends on the amount of

dust Dust is made of fine particles of solid matter. On Earth, it generally consists of particles in the atmosphere that come from various sources such as soil lifted by wind (an aeolian process), volcanic eruptions, and pollution. Dust in homes ...

cloud In meteorology, a cloud is an aerosol consisting of a visible mass of miniature liquid droplets, frozen crystals, or other particles suspended in the atmosphere of a planetary body or similar space. Water or various other chemicals may co ...

s in the atmosphere; this also controls how much light is scattered. In general, the dustier the atmosphere, the more that other wavelengths of light will be removed (compared to red light), leaving the resulting light a deeper red color. This causes the resulting coppery-red hue of the Moon to vary from one eclipse to the next. Volcanoes are notable for expelling large quantities of dust into the atmosphere, and a large eruption shortly before an eclipse can have a large effect on the resulting color. Eclipse Christophe Colomb

Lunar eclipse in culture

Several cultures have

myth Myth is a folklore genre consisting of Narrative, narratives that play a fundamental role in a society, such as foundational tales or Origin myth, origin myths. Since "myth" is widely used to imply that a story is not Objectivity (philosophy), ...

s related to lunar eclipses or allude to the lunar eclipse as being a good or bad omen. The

Egyptians Egyptians ( arz, المَصرِيُون, translit=al-Maṣriyyūn, ; arz, المَصرِيِين, translit=al-Maṣriyyīn, ; cop, ⲣⲉⲙⲛ̀ⲭⲏⲙⲓ, remenkhēmi) are an ethnic group native to the Nile, Nile Valley in Egypt. Egyptian ...

saw the eclipse as a sow swallowing the Moon for a short time; other cultures view the eclipse as the Moon being swallowed by other animals, such as a

jaguar The jaguar (''Panthera onca'') is a large cat species and the only living member of the genus '' Panthera'' native to the Americas. With a body length of up to and a weight of up to , it is the largest cat species in the Americas and the th ...

Mayan Mayan most commonly refers to: * Maya peoples, various indigenous peoples of Mesoamerica and northern Central America * Maya civilization, pre-Columbian culture of Mesoamerica and northern Central America * Mayan languages, language family spoken ...

tradition, or a mythical three-legged toad known as

Chan Chu The Jin Chan (), also called Chan Chuy () or "Zhaocai Chan Chu" (), is most commonly translated as "Money Toad" or "Money Frog". It represents a popular feng shui charm for prosperity. This mythical creature is said to appear during the full moon ...

China China, officially the People's Republic of China (PRC), is a country in East Asia. It is the world's most populous country, with a population exceeding 1.4 billion, slightly ahead of India. China spans the equivalent of five time zones and ...

. Some societies thought it was a demon swallowing the Moon, and that they could chase it away by throwing stones and curses at it. The

Ancient Greeks Ancient Greece ( el, Ἑλλάς, Hellás) was a northeastern Mediterranean civilization, existing from the Greek Dark Ages of the 12th–9th centuries BC to the end of classical antiquity ( AD 600), that comprised a loose collection of cult ...

correctly believed the Earth was round and used the shadow from the lunar eclipse as evidence. Some

Hindus Hindus (; ) are people who religiously adhere to Hinduism.Jeffery D. Long (2007), A Vision for Hinduism, IB Tauris, , pages 35–37 Historically, the term has also been used as a geographical, cultural, and later religious identifier for ...

believe in the importance of bathing in the

Ganges River The Ganges ( ) (in India: Ganga ( ); in Bangladesh: Padma ( )). "The Ganges Basin, known in India as the Ganga and in Bangladesh as the Padma, is an international river to which India, Bangladesh, Nepal and China are the riparian states." is ...

following an eclipse because it will help to achieve

salvation Salvation (from Latin: ''salvatio'', from ''salva'', 'safe, saved') is the state of being saved or protected from harm or a dire situation. In religion and theology, ''salvation'' generally refers to the deliverance of the soul from sin and its c ...

Inca

Similarly to the Mayans, the

Incans The Inca Empire (also known as the Incan Empire and the Inka Empire), called ''Tawantinsuyu'' by its subjects, (Quechua for the "Realm of the Four Parts", "four parts together" ) was the largest empire in pre-Columbian America. The admin ...

believed that lunar eclipses occurred when a jaguar ate the Moon, which is why a blood moon looks red. The Incans also believed that once the jaguar finished eating the Moon, it could come down and devour all the animals on Earth, so they would take spears and shout at the Moon to keep it away.

Mesopotamians

The ancient

Mesopotamians Mesopotamia ''Mesopotamíā''; ar, بِلَاد ٱلرَّافِدَيْن or ; syc, ܐܪܡ ܢܗܪ̈ܝܢ, or , ) is a historical region of Western Asia situated within the Tigris–Euphrates river system, in the northern part of the F ...

believed that a lunar eclipse was when the Moon was being attacked by seven demons. This attack was more than just one on the Moon, however, for the Mesopotamians linked what happened in the sky with what happened on the land, and because the king of Mesopotamia represented the land, the seven demons were thought to be also attacking the king. In order to prevent this attack on the king, the Mesopotamians made someone pretend to be the king so they would be attacked instead of the true king. After the lunar eclipse was over, the substitute king was made to disappear (possibly by

poisoning A poison can be any substance that is harmful to the body. It can be swallowed, inhaled, injected or absorbed through the skin. Poisoning is the harmful effect that occurs when too much of that substance has been taken. Poisoning is not to ...

Chinese

In some Chinese cultures, people would ring bells to prevent a

dragon A dragon is a reptilian legendary creature that appears in the folklore of many cultures worldwide. Beliefs about dragons vary considerably through regions, but dragons in western cultures since the High Middle Ages have often been depicted as ...

or other wild animals from biting the Moon. In the 19th century, during a lunar eclipse, the

Chinese navy The People's Liberation Army Navy (PLAN; ), also known as the People's Navy, Chinese Navy, or PLA Navy, is the maritime service branch of the People's Liberation Army. The PLAN traces its lineage to naval units fighting during the Chine ...

fired its artillery because of this belief. During the

Zhou Dynasty The Zhou dynasty ( ; Old Chinese ( B&S): *''tiw'') was a royal dynasty of China that followed the Shang dynasty. Having lasted 789 years, the Zhou dynasty was the longest dynastic regime in Chinese history. The military control of China by th ...

( 1046–256 BC) in the ''Book of Songs'', the sight of a Red Moon engulfed in darkness was believed to foreshadow famine or disease.

Blood moon

Certain lunar eclipses have been referred to as "blood moons" in popular articles but this is not a scientifically-recognized term. This term has been given two separate, but overlapping, meanings. The first, and simpler, meaning relates to the reddish color a totally eclipsed Moon takes on to observers on Earth. As

penetrates the

atmosphere of Earth The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing for ...

, the gaseous layer

filters Filter, filtering or filters may refer to: Science and technology Computing * Filter (higher-order function), in functional programming * Filter (software), a computer program to process a data stream * Filter (video), a software component tha ...

and

refracts In physics, refraction is the redirection of a wave as it passes from one transmission medium, medium to another. The redirection can be caused by the wave's change in speed or by a change in the medium. Refraction of light is the most common ...

the rays in such a way that the green to violet wavelengths on the

visible spectrum The visible spectrum is the portion of the electromagnetic spectrum that is visual perception, visible to the human eye. Electromagnetic radiation in this range of wavelengths is called ''visible light'' or simply light. A typical human eye wil ...

scatter more strongly than the red, thus giving the Moon a reddish cast. The second meaning of "blood moon" has been derived from this apparent coloration by two

fundamentalist Christian Christian fundamentalism, also known as fundamental Christianity or fundamentalist Christianity, is a religious movement emphasizing biblical literalism. In its modern form, it began in the late 19th and early 20th centuries among British and ...

pastors,

Mark Blitz Mark Blitz (born March 15, 1946) is an American political philosopher and Fletcher Jones Professor of Political Philosophy at Claremont McKenna College. Books *Plato's political philosophy, Baltimore : Johns Hopkins University Press, . 2010 *C ...

and

John Hagee John Charles Hagee (born April 12, 1940) is an American pastor and televangelist. The founder of John Hagee Ministries, his ministry is telecast to the United States and Canada. Hagee is also the founder and chairman of the Christian-Zionist or ...

. They claimed that the 2014–15 " lunar tetrad" of four lunar eclipses coinciding with the feasts of

Passover Passover, also called Pesach (; ), is a major Jewish holidays, Jewish holiday that celebrates the The Exodus, Biblical story of the Israelites escape from slavery in Ancient Egypt, Egypt, which occurs on the 15th day of the Hebrew calendar, He ...

and Tabernacles matched the "moon turning to blood" described in the

Book of Joel The Book of Joel is collected as one of the twelve minor prophets of the Nevi'im ("Prophets") in the Hebrew Bible, and as a book in its own right in the Christian Old Testament. Content After a superscription ascribing the prophecy to Joel (s ...

of the

Hebrew Bible The Hebrew Bible or Tanakh (;"Tanach"
''Random House Webster's Unabridged Dictionary''. Hebrew: ''Tān ...

. This tetrad was claimed to herald the

Second Coming of Christ The Second Coming (sometimes called the Second Advent or the Parousia) is a Christian (as well as Islamic and Baha'i) belief that Jesus will return again after his ascension to heaven about two thousand years ago. The idea is based on messi ...

and the

Rapture The rapture is an Christian eschatology, eschatological position held by some Christians, particularly those of American evangelicalism, consisting of an Eschatology, end-time event when all Christian believers who are alive, along with resurre ...

as described in the

Book of Revelation The Book of Revelation is the final book of the New Testament (and consequently the final book of the Christian Bible). Its title is derived from the first word of the Koine Greek text: , meaning "unveiling" or "revelation". The Book of R ...

on the date of the first of the eclipses in this sequence on April 15, 2014.

Occurrence

At least two lunar eclipses and as many as five occur every year, although total lunar eclipses are significantly less common. If the date and time of an eclipse is known, the occurrences of upcoming eclipses are predictable using an

eclipse cycle Eclipses may occur repeatedly, separated by certain intervals of time: these intervals are called eclipse cycles. The series of eclipses separated by a repeat of one of these intervals is called an eclipse series. Eclipse conditions Eclips ...

, like the saros.

Recent and forthcoming lunar eclipses

Eclipses occur only during an

, when the Sun appears to pass near either

node In general, a node is a localized swelling (a "knot") or a point of intersection (a vertex). Node may refer to: In mathematics *Vertex (graph theory), a vertex in a mathematical graph *Vertex (geometry), a point where two or more curves, lines, ...