8 (number)

This article is about the number eight.

8
0 1 2 3 4 5 6 7 8 9 >> List of numbers — Integers 0 10 20 30 40 50 60 70 80 90 >>
Cardinal	8 eight
Ordinal	8th eighth
Numeral system	octal
Factorization	$2^{3}$
Divisors	1, 2, 4, 8
Roman numeral	VIII
Roman numeral (Unicode)	Ⅷ, ⅷ
Arabic	٨
Amharic	፰
Bengali	৮
Chinese numeral	八，捌
Devanāgarī	८
Hebrew	ח (Het)
Khmer	៨
Thai	๘
prefixes	octa-/oct- (from Greek) octo-/oct- (from Latin)
Binary	1000
Octal	10
Duodecimal	8
Hexadecimal	8

8 (eight) is a number, numeral, and glyph that represents the number. It is the natural number that follows 7 and precedes 9. It is an integer and a cardinal number, that is, a number that is used for counting. In addition, it is classified as a real number, distinguishing it from imaginary numbers.

Evolution of the glyph

In the beginning, various groups in India wrote eight more or less in one stroke as a curve that looks like an uppercase H with the bottom half of the left line and the upper half of the right line removed. At one point this glyph came close to looking like our modern five. With the western Ghubar Arabs, the similarity of the glyph to five was banished by connecting the beginning and end of the stroke together. After that, the Europeans simply rounded the glyph, leading to our modern eight.

As in most modern typefaces, in typefaces with text figures the 8 character usually has an ascender, for example, in . The "1" and "4" are old-style figures; the "8" is the same height in both old-style and modern figures. 1234567890 are all the same height; they are modern figures.

In mathematics

8 is a composite number, its proper divisors being 1, 2, and 4. Eight is a power of two, being $2^{3}$, or two cubed. It has an aliquot sum of 7. All powers of 2 have an aliquot sum of one less than themselves.

8 is the base of the octal number system, which is mostly used with computers. In octal, one digit represents 3 bits. In modern computers, a byte is a grouping of eight bits, also called an octet.

The number 8 is a Fibonacci number, being 3 plus 5. The next Fibonacci number is 13.

8 and 9 form a Ruth-Aaron pair under the second definition in which repeated prime factors are counted as often as they occur.

A polygon with eight sides is an octagon. Figurate numbers representing octagons (including eight) are called octagonal numbers. A polyhedron with eight faces is an octahedron.

Sphenic numbers always have exactly eight divisors.

8 is the dimension of the octonions and is the highest possible dimension of a normed division algebra.

The number 8 is involved with a number of interesting mathematical phenomena related to the notion of Bott periodicity. For example if $O(\infty )$ is the direct limit of the inclusions of real orthogonal groups $O(1)\hookrightarrow O(2)\hookrightarrow \ldots \hookrightarrow O(k)\hookrightarrow \ldots$ then $\pi _{k+8}(O(\infty ))\cong \pi _{k}(O(\infty ))$. Clifford algebras also display a periodicity of 8. For example the algebra $Cl(p+8,q)$ is isomorphic to the algebra of 16 by 16 matrices with entries in $Cl(p,q)$. We also see a period of 8 in the K theory of spheres and in the representation theory of the rotation groups, the latter giving rise to the 8 by 8 spinorial chessboard. All of these properties are closely related to the properties of the octonions.

The lowest dimensional even unimodular lattice is the 8-dimensional E₈ lattice. Even positive definite unimodular lattice exist only in dimensions divisible by 8.

A figure 8 is the common name of a geometric shape, often used in the context of sports, such as skating

In binary code eight is 1000; in ternary code eight is 22; in quaternary numeral system code eight is 20; in quinary eight is 13; in senary eight is 12; in septenary eight is 11; in octal eight is 10; in novenary code and all codes above (such as decimal and hexadecimal) eight is 8.

A fallen or lying down 8 (∞, the lemniscate) is used to represent infinity in mathematics. This interpretation of 8 may be related to the representation of the caduceus (where two snakes form several figure eights) as stability or balance of opposing forces.

Eight is the number of Thurston model geometries. Eight is not a prime number

E₈ has rank 8.

As of 2008, there are only eight known Stern primes.

In numeral systems

Base	Numeral system
2	binary	1000
3	ternary	22
4	quaternary	20
5	quinary	13
6	senary	12
7	septenary	11
8	octal	10
over 8 (decimal, hexadecimal)		8

List of basic calculations

Multiplication	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20		21	22	23	24	25		50	100	1000
$8\times x$	8	16	24	32	40	48	56	64	72	80	88	96	104	112	120	128	136	144	152	160		168	176	184	192	200		400	800	8000

Division	1	2	3	4	5	6	7	8	9	10		11	12	13	14	15
$8\div x$	8	4	$2.{\overline {6}}$	2	1.6	$1.{\overline {3}}$	$1.{\overline {142857}}$	1	$0.{\overline {8}}$	0.8		$0.{\overline {72}}$	$0.{\overline {6}}$	$0.{\overline {615384}}$	$0.{\overline {571428}}$	$0.5{\overline {3}}$
$x\div 8$	0.125	0.25	0.375	0.5	0.625	0.75	0.875	1	1.125	1.25		1.375	1.5	1.625	1.75	1.875

Exponentiation	1	2	3	4	5	6	7	8	9	10		11	12	13
$8^{x}\,$	8	64	512	4096	32768	262144	2097152	16777216	134217728	1073741824		8589934592	68719476736	549755813888
$x^{8}\,$	1	256	6561	65536	390625	1679616	5764801	16777216	43046721	100000000		214358881	429981696	815730721

Radix	1	5	10	15	20	25	30	40	50	60	70	80	90	100
	110	120	130	140	150	200	250	500	1000	10000	100000	1000000
$x_{8}\$	1	5	$12_{8}\$	$17_{8}\$	$24_{8}\$	$31_{8}\$	$36_{8}\$	$50_{8}\$	$62_{8}\$	$74_{8}\$	$106_{8}\$	$120_{8}\$	$132_{8}\$	$144_{8}\$
	$156_{8}\$	$170_{8}\$	$202_{8}\$	$214_{8}\$	$226_{8}\$	$310_{8}\$	$372_{8}\$	$764_{8}\$	$1750_{8}\$	$23420_{8}\$	$303240_{8}\$	$3641100_{8}\$

In science

Physics

• In nuclear physics, 8 is the second magic number; the first one being 2. A magic number (in this case) is the number of nucleons (protons and neutrons) in the atomic nucleus, such that they are arranged into complete shells in the nucleus.
• In particle physics, the eightfold way is used to classify subatomic particles.

Astronomy

• The Saros number of the solar eclipse series that began on March 7, 2579 B.C.E. and ended on April 26, 1281 B.C.E. The duration of Saros series 8 was 1298.1 years, and it contained 73 solar eclipses.
• The Saros number of the lunar eclipse series that began on July 27, 2512 B.C.E. and ended on February 13, 961 B.C.E. The duration of Saros series 7 was 1550.6 years, and it contained 87 lunar eclipses.
• As of 2006, eight of the bodies orbiting the Sun are considered planets, in the Solar System.

Chemistry

• Eight is the atomic number of oxygen.
• The most stable allotrope of a sulfur molecule is made of eight sulfur atoms arranged in a rhombic form.
• In the electronic configurations of atoms, eight is usually the maximum number of electrons that can occupy a valence shell.
• The red pigment Lycopene consists of eight isoprene units.

Biology

• There are eight known B vitamins that play important roles in cell metabolism.
• All spiders, and more generally all arachnids, have eight legs.
• An octopus has eight tentacles.
• In the human adult dentition there are 8 teeth in each quadrant. The 8th tooth is the so called the wisdom tooth.
• Timothy Leary identified a hierarchy of eight levels of consciousness.

Measurement

• The SI prefix for 1000⁸ is yotta (Y), and that for its reciprocal is yocto (y).
• In liquid measurement (US customary units), there are 8 fluid ounces in a cup, 8 pints in a gallon, and 8 tablespoons in a gill
• There are 8 furlongs in a mile.

In technology

• Many (mostly historic) computer architectures are eight-bit, among them the Nintendo Entertainment System
• A byte is eight bits
• On most phones, the 8 key is associated with the letters T, U, and V, but on the BlackBerry it is the key for B , N, and X.
• A V8 engine is an internal combustion engine with 8 cylinders configured in two banks (rows) of 4 forming a "V" when seen from the end.
• A figure eight is a type of knot frequently used by climbers.

In religion

• The Dharmachakra, a Buddhist symbol, has eight spokes. The Buddha's principal teaching—the Four Noble Truths—ramifies as the Noble Eightfold Path. In Mahayana Buddhism, the branches of the Eightfold Path are embodied by the Eight Great Bodhisattvas (Manjushri, Vajrapani, Avalokiteshvara, Maitreya, Kshitigarbha, Nivaranavishkambhi, Akashagarbha, and Samantabhadra). These are later (controversially) associated with the Eight Consciousnesses according to the Yogachara school of thought: consciousness in the five senses, thought-consciousness, self-consciousness and unconsciousness-'consciousness' (alaya-vijñana). The 'irreversible' state of enlightenment, at which point a Bodhisattva goes on 'autopilot', is the Eight Ground or bhūmi. In general, 'eight' seems to be an auspicious number for Buddhists, e.g., the 'eight auspicious symbols' (the jewel-encrusted parasol; the goldfish (always shown as a pair, e.g., the glyph of Pisces); the self-replenishing amphora; the white kamala lotus-flower; the white conch; the eternal (Celtic-style, infinitely looping) knot; the banner of imperial victory; the eight-spoked wheel that guides the ship of state, or that symbolizes the Buddha's teaching). Similarly, Buddha's birthday falls on the 8th day of the 4th month of the Chinese calendar.
• The Jewish religious rite of brit milah is held on a baby boy's eighth day of life
• Hanukkah is an eight-day Jewish holiday that starts on the 25th day of Kislev
• Shemini Atzeret (Hebrew: "Eighth Day of Assembly") is a one-day Jewish holiday immediately following the seven-day holiday of Sukkot

• The Eight Immortals are Chinese deities
• Members of The Church of Jesus Christ of Latter-day Saints believe that humans are responsible for their actions by the age of 8. Before that age, children lack sufficient knowledge to commit sin and are therefore exempt from judgment for their actions.

• In Christianity, it is allegoric to:
  • what is beyond time (because the number 7 refers to the days of the week which repeat themselves),
  • and is the number of Beatitudes.
• In Islam, It is the number of Angels carrying The Holy Throne of Allah in heavens.
• In Neopaganism, there are eight Sabbats, festivals, seasons, or spokes in the Wheel of the Year.
• In Hinduism its the number of wealth , abundance. The Goddess Lakshmi has eightfold forms. There are eight nidhis - seats of wealth.

In superstition and divination

As a lucky or unlucky number

• Eight (八; accounting 捌; pinyin bā) is considered a lucky number in Asian culture because it sounds like the word "prosper" or "wealth" (发; Pinyin: fā). Additionally, it is considered lucky in Japan because the Chinese numeral character resembles a mountain, specifically Fujisan.
• In numerology, 8 is the number of building, and in some theories, also the number of destruction.

In astrology

• In Astrology, Scorpio is the 8th astrological sign of the Zodiac
• In the middle ages, 8 was the number of "unmoving" stars in the sky, and symbolized the perfectioning of incoming planetary energy

In music

• A note played for one-eighth the duration of a whole note is called an eighth note, or quaver
• An octave, the interval between two notes with the same letter name (where one has double the frequency of the other), is so called because there are eight notes on a western scale between the two, including the notes themselves
• There are eight notes in an octatonic scale
• There are eight musicians in an octet
• Albums with the number eight in their title include 8 by the Swedish band Arvingarna and The Meaning of 8 by Minnesota indie rock band Cloud Cult
• Dream Theater's eighth album Octavarium contains many different references to the number 8, including the number of songs and various aspects of the music and cover artwork
• "Eight maids a-milking" is the gift on the eighth day of Christmas in the carol "The Twelve Days of Christmas"
• The 8-track cartridge is a musical recording format
• "#8" is the stagename of Slipknot vocalist Corey Taylor
• "Too Many Eights" is a song by Athens, Georgia's Supercluster (band).
• Eight Seconds, a Canadian musical group popular in the 1980s with their most notable song "Kiss You (When It's Dangerous)"
• "Eight Days a Week" is #1 single for the music group The Beatles.

In sports

In football, the number 8 has historically been the number of the Central Midfielder while in rugby union the number eight central back row position wears the 8 shirt. Similarly in baseball, in its numbering system used to record defensive plays, eight represents the center fielder's position. The Philadelphia Flyers once had a line called the Crazy Eights with Eric Lindros at center (88); Mark Recchi (8); and Brent Fedyk (18). Kobe Bryant wore this number for most parts of his career. 49ers Quarterback Steve Young wore this number. In chess, each side has eight pawns and the board is made of 64 squares arranged in an eight by eight lattice. The eight queens puzzle is a challenge to arrange eight queens on the board so that none can capture any of the others.

Eight ball billiards is played with 15 balls; the black ball numbered 8 being the middle and most important one. Magic 8 Ball is a randomized process of predicting the future or answering various questions, packaged to resemble this ball and often sold as a fortune-telling device.

In rowing an 'eight' refers to a sweep oar boat with eight rowers plus a coxswain.

In rugby union, the only position without a proper name is the Number 8, a forward position.

It is the retired jersey number of Baseball Hall of Fame players Cal Ripken, Jr., Joe Morgan, Willie Stargell, Carl Yastrzemski, and Yogi Berra.

Ray Fosse, an all-star catcher and gold glove winner in 1970 and 1971, wore number 8 when he played for the Cleveland Indians (1967-1972). [Fosse also played for Cleveland in 1976 and 1977, but wore number 10 in those years.] His name "Ray Fosse" has 8 letters. His birthday is April 4 (4 + 4 = 8). His playing height was 6' 2" (6 + 2 = 8) and playing weight was 215 lbs. (2 + 1 + 5 = 8). He was drafted by the Cleveland Indians in 1965 as the seventh pick in the first round (7 + 1 = 8). His major league debut was on the 8th (of September, 1967); he batted 8th in the lineup and had 8 put-outs as the catcher. In his first year with the Cleveland Indians (1967), the team finished in 8th place. He played with the Cleveland Indians for 8 seasons (1967-72 and 1976-77). When Fosse won his second gold glove in 1971, it was the 8th time that a Cleveland Indian won a gold glove. In his first two seasons with Cleveland, he played in 8 games. In 1970, he had the only 5 RBI game of his career on May 21 (5 + 2 + 1 = 8). In 1977, he caught the only no hitter of his career (by Dennis Eckersley) on May 30 (5 + 3 + 0 = 8). In 1977, he played in 11 games with the Seattle Mariners—his position was catcher for 8 of those games.

In foods

• There is a brand of chocolates filled with peppermint-flavoured cream called "After Eight," referring to the time 8 p.m.
• There are eight vegetables in V8 juice
• In cooking recipes, there are approximately 8 pinches to a teaspoon

In literature

• In Terry Pratchett's Discworld series, eight is a holy number and is considered taboo. Eight is not safe to be said by wizards on the Discworld and is the number of Bel-Shamharoth. Also, there are eight days in a Disc week and eight colours in a Disc spectrum, the eighth one being Octarine
• Lewis Carroll's poem The Hunting of the Snark has 8 "fits" (cantos), which is noted in the full name "The Hunting of the Snark - An Agony, in Eight Fits
• 8 apparitions appear to Macbeth in Act 4 scene 1 of Shakespeare's Macbeth as representations of the 8 descendants of Banquo

In slang

• An Eighth is a common measurement of marijuana, meaning an eighth of an ounce
• Referring to the shape of the numeral, eight was represented in bingo slang, before political correctness, as "One Fat Lady." Eighty-eight was "Two Fat Ladies"
• The numeral "8" is sometimes used in writing to represent the syllable "ate," as in writing "H8" for "hate," or "congratul8ions" for "congratulations." Avril Lavigne's song "Sk8er Boi" uses this convention in the title. Often found on vanity plates
• "Section 8" is common U.S. slang for "crazy," based on the U.S. military's Section 8 discharge for mentally unfit personnel
• In Colombia and Venezuela, "volverse un ocho" (meaning to tie oneself in a figure 8) refers to getting in trouble or contradicting one's self.
• In China, '8' is used in chat speak as a term for parting. This is due to the closeness in pronunciation of '8' (bā) and the English word 'bye'.
• Eight is symbolic for lesbian sexual relations.

In other fields

International maritime signal flag for 8

Four playing cards showing the "8" of all four suits

• The ordinal adjective is octaval or octavary.
• The distributive adjective is octonary.
• Various types of buildings are usually eight-sided (octagonal), such as single-roomed gazebos and multi-roomed pagodas (descended from stupas).
• Eight babies delivered in a single birth are called octuplets. The first set of eight surviving babies, the Chukwu octuplets, was born in 1998.
• October was the eighth month in the Roman calendar; currently August is the eighth month.
• War of the Eight Princes was a war in Chinese history
• "88" is the abbreviated terminology used by the Aryan Brotherhood for the Nazi salute, "Heil Hitler"—"H" being the eighth letter of the alphabet, twice
• The silver piece of eight was coined in the Spanish Empire and moved trade around the world.
• There are Eight Principles of Yong in Chinese calligraphy.
• 8vo is shorthand for "octavo," a book size.
• The Eight: Eight American painters who exhibited together only once in 1908 in New York City. They joined this exhibition to oppose traditions upheld by the National Academy and help advance modernism in the United States. Five of the eight painters were associated with the Ashcan School: Robert Henri (1865-1929), George Luks (1867-1933), William Glackens (1870-1938), John Sloan (1871-1951), and Everett Shinn (1876-1953), along with Maurice Prendergast (1859-1924), Ernest Lawson (1873-1939), and Arthur Bowen Davies (1862-1928).

See also

• Arithmetic
• Integer
• Number

References

ISBN links support NWE through referral fees

• Flegg, Graham. 2002. Numbers: Their History and Meaning. Mineola, NY: Dover Publications. ISBN 0486421651.

• Higgins, Peter M. 2008. Number Story: From Counting to Cryptography. London: Copernicus. ISBN 978-1848000001.

• Ifrah, Georges. 2000. The Universal History of Numbers: From Prehistory to the Invention of the Computer. Translated by David Bellos et al. New York: Wiley. ISBN 0471393401.

• McLeish, John. 1994. The Story of Numbers: How Mathematics Has Shaped Civilization. New York: Fawcett Columbine. ISBN 0449909387.

• Menninger, Karl. 1992. Number Words and Number Symbols: A Cultural History of Numbers. New York: Dover Publications. ISBN 0486270963.

• Wells, D. G. 1998. The Penguin Dictionary of Curious and Interesting Numbers. Rev. ed. London, UK: Penguin Books. ISBN 0140261494.

External links

• Spoke 8: Symbolic Meaning of the Number Eight. The Bible Wheel. Retrieved August 21, 2008.
• Base Eight. Retrieved August 21, 2008.

• The Octonions John C Baez
• Flickr 8, the infinite beauty of - photo group
• 8by8 an art community based on the geometry of 8

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