Jump to content

7

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by Tolukra (talk | contribs) at 08:41, 1 November 2007 (In film: added »The Seventh Sign«). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Template:Numbers (digits)
Cardinal 7
seven
Ordinal 7th
seventh
Numeral system septenary
Factorization prime
Divisors 1, 7
Roman numeral VII
Roman numeral (Unicode) Ⅶ, ⅶ
Arabic ٧
Bengali
Chinese numeral
Devanāgarī
Hebrew ז (Zayin)
Khmer
prefixes hepta-/hept-
Binary 00000111
Octal 7
Duodecimal 7
Hexadecimal 7
Seven Days of Creation - 1765 book, title page

7 (seven) is the natural number following 6 and preceding 8.

In mathematics

  1. Remove the last digit,
  2. Double it, and
  3. Subtract it from the remaining digits.
  4. If the result is negative and there are 2 or more digits, drop the negative sign.
  5. Repeat until you end up with a result that is a multiple of seven (7). (i.e. -7, 0, or +7)
For example, the number 1358 is evenly divisible by seven, since:
135 - (8*2) = 119
11 - (9*2) = -7
Using Number Theory the proof is rather simple, once the number n is rewritten in the form:
n = 10a + b
Where:
a is the remaining digits, and
b is the last digit.
Then:
10a + b = 0 (mod 7)
5 * (10a + b) = 0 (mod 7)
49a + a + 5b = 0 (mod 7)
a + 5b - 7b = 0 (mod 7)
a - 2b = 0 (mod 7)

A second divisibility rule was formulated in 2006 in India, by Himanish Ganjoo, a Class 8 student in St. Columba's School Delhi:

  1. Remove the last two digits
  2. Divide the remaining number by 7
  3. Multiply the remainder by 2
  4. Add the product to the last two digits
  5. If the sum is divisible by 7, the number is also divisible

On March 25, 2007, Ganjoo formulated another variant form of this test, now separating the last 3 digits (in step 1), and multiplying the remainder by 6 (step 3), and then adding the sum to the last 3 digits (originally separated).

For example, 1568 is divisible by 7,
  1. 15/7 Remainder = 1
  2. Product 1*2 = 2
  3. 68 + 2 = 70 (which is divisible by 7)

Hence, 1568 is divisible by 7

In numeral systems

Base Numeral system
2 binary 111
3 ternary 21
4 quaternary 13
5 quinary 12
6 senary 11
7 septenary 10
over 7 (octal, decimal, etc) 7

In quaternary, 7 is the smallest prime with a composite sum of digits.

In the English language, 7 is the only 2-syllable natural, positive 1-digit number

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
7 14 21 28 35 42 49 56 63 70 77 84 91 98 105 112 119 126 133 140 147 154 161 168 175 350 700 7000
Division 1 2 3 4 5 6 7 8 9 10
11 12 13 14 15
7 3.5 1.75 1.4 1 0.875 0.7
0.5
1
2
Exponentiation 1 2 3 4 5 6 7 8 9 10 11 12 13
7 49 343 2401 16807 117649 823543 5764801 40353607 282475249 1977326743 13841287201 96889010407
1 128 2187 16384 78125 279936 823543 2097152 4782969 10000000 19487171 35831808 62748517
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
1 5

Evolution of the glyph

In the beginning, various Hindus wrote 7 more or less in one stroke as a curve that looks like an uppercase J upside down. The western Ghubar Arabs' main contribution was to make the longer line diagonal rather than straight, though they showed some tendencies to making the character more rectilinear. The eastern Arabs developed the character from a 6-look-alike into an uppercase V-look-alike. Both modern Arab forms influenced the European form, a two-stroke character consisting of a horizontal upper line joined at its right to a line going down to the bottom left corner, a line that is slightly curved in some font variants. As is the case with the European glyph, the Cham and Khmer glyph for 7 also evolved to look like their glyph for 1, though in a different way, so they were also concerned with making their 7 more different. For the Khmer this often involved adding a horizontal line above the glyph.[1] This is analogous to the horizontal stroke through the middle that is sometimes used in handwriting in the Western world but which is almost never used in computer fonts. This horizontal stroke is, however, important to distinguish the glyph for seven from the glyph for one in writings that use a long upstroke in the glyph for one.

On the seven-segment displays of pocket calculators and digital watches, 7 is the number with the most common glyph variation (0, 6 and 9 also have variant glyphs). Most calculators use three line segments, but on Sharp, Casio, and a few other brands of calculators, 7 is written with four line segments. The reason is that in Japan & Korea 7 is written as ① in the illustration to the right.

While the shape of the 7 character has an ascender in most modern typefaces, in typefaces with text figures the character usually has a descender, as, for example, in .

In science

  • The number of spots on a common ladybug.
  • With very few exceptions, all mammals' necks have seven bones.
  • ROY G. BIV = red, orange, yellow, green, blue, indigo, and violet are the 7 colours of the rainbow.

Chemistry

Astronomy

In technology

In the classical world

In classical antiquity:

In religion

God rested on and sanctified the seventh day (Shabbat).
  • In Judaism:
    • A highly symbolic number in the Torah, alluding to the infusion of spirituality and Godliness into the Creation. For example:
    1. God rested on and sanctified the seventh day (Sabbath).
    2. A seven-day purification period is required for one who has become tamei to become tahor.
    3. The Shemittah (Sabbatical) year arrives every seventh year.
    4. The Jubilee (Yovel) year comes after 7 times 7 years.
    5. The Counting of the Omer leading up to the Giving of the Torah is expressed as "7 times 7 weeks."
    • The weekly Torah portion is divided into seven aliyahs, and seven men or boys over the age of 13 are called up for the reading of these aliyahs during Sabbath morning services.
    • Seven blessings are recited under the chuppah during a Jewish wedding ceremony.
    • David was the eighth son of Jesse.
    • A Jewish bride and groom are feted with seven days of festive meals after their wedding, known as Sheva Berachot ("Seven Blessings").
    • The number of Ushpizzin (also known as the "Seven Shepherds") who visit the sukkah during the holiday of Sukkot: Abraham, Isaac, Jacob, Joseph, Moses, Aaron, and David.
    • The number of nations God told the Israelites they would displace when they entered the land of Israel (Deut. 7:1): the Hittite, the Girgashite, the Amorite, the Canaanite, the Perizzite, the Hivite, and the Jebusite.
    • In Breslov tradition, the seven orifices of the face (2 eyes, 2 nostrils, 2 ears, and the mouth) are called "The Seven Candles."
    • The menorah (Hebrew: מנורה), is a seven branched candelabrum lit by olive oil in the Tabernacle and the Temple in Jerusalem. The menorah is one of the oldest symbols of the Jewish people. It is said to symbolize the burning bush as seen by Moses on Mount Sinai (Exodus 25).
  • In Islam:
    • The number of ayat in surat al-Fatiha.
    • The number of heavens in Islamic tradition.
    • The number of Earths in Islamic tradition.
    • The number of circumambulations (Tawaf) that are made around the Kaaba
    • The number of walks {Al-Safa and Al-Marwah) that is travelling back and forth seven times during the ritual pilgrimages of Hajj and Umrah.
  • In Eternalism:
    • The number of deities
    • The years Godzimir was exiled to Turin, in Savoy
    • 1/7 of each of the Deities powers was taken to create the Eternal
    • There are seven verses in each of the Septrains of the Prognostications of Godzimir and Invomandus
    • Seven universe in each phase toward Edication
  • Others:
    • The number of Archangels according to some systems.
    • The minor symbol number of yang from the Taoist yin-yang.
    • The number of palms in an Egyptian Sacred Cubit.
    • The number of ranks in Mithraism.
    • The number seven is of particular significance within Cherokee cosmology.
    • In Buddhism, Buddha walked 7 steps at his birth.
  • In Hinduism:
    • The Sanskrit word 'sapta' refers to number seven.
    • The Indian Music has 'sapta swaras', means seven octats (sa re ga ma pa dha ni), which are basics of music, using which hundreds of Ragas are composed.
    • The Month 'September' is evolved from the word 'septa' meaning seven. September was earlier seventh month before July and August were added to the calendar. Also the subsequent months names are derived from Sanskrit names 'Ashta' and 'Nava' meaning eight and nine which are now called October and November.
    • Celestial group of seven stars are named as 'Sapta Rishi' based on the seven great saints.
    • Seven Promises, Seven Rounds in Hindu Wedding and Seven Reincarnation
    • As per Hindu mythology, there are seven worlds in the universe, seven seas in the world and seven Rishies (seven gurus) called sapta rishis.

In mythology

  • In Khasi mythology, the seven divine women who were left behind on earth and became the ancestresses of all humankind.
  • The number of gateways traversed by Inanna during her descent into the underworld.
  • The number of sleeping men in the Christian myth of the "Seven Sleepers."
  • The number of sages in Hindu mythology; their wives are the goddesses referred to as the "Seven Mothers."
  • The number of main islands of mythological Atlantis.
  • In Guaraní mythology, the number of prominent legendary monsters.
  • Seven Lucky Gods exist in Japanese mythology.
  • In British Folk lore, every 7 years the Fairy Queen pays a tithe to Hell (or possibly Hel) in the tale of Tam Lin.
  • In the British Folk tale of Thomas the Rhymer, he went to live in the faerie kingdom for 7 years.

In psychology

In music

In television

In film

In literature

In video games

  • 7 is a number used many times by Bungie Studios in their Halo and Marathon games. 7 appears in a variety of different contexts, from the stories of the games to the raw game coding. One obvious example is the fact that there are seven Halo rings strewn throughout the galaxy.
  • Final Fantasy VII has many instances of seven throughout the game and was even released (in North America) on the seventh day of September ("September" originally meant "seventh month") in 1997.
  • In the Sonic the Hedgehog games, Sonic collects seven Chaos Emeralds (after completing special stages) which, after getting all of them and then collecting at least 50 rings, allow him to turn into Super Sonic. This transformation makes him glow golden yellow and allows him to move at speeds much faster than he already moves (at the speed of sound[3]). Sonic 3 & Knuckles allows for an even more powerful transformation called 'Hyper Sonic' once an additional seven 'Super Emeralds' are collected.
  • The number of individual personalities serving Harman Smith as part of the group of assassins called the Killer7, hence the title of the game.
  • In Kingdom Hearts there are seven Princesses of Heart.
  • In the Super Mario RPG/Paper Mario series of games, the collection of seven mystical items (predominantly stars, but also hearts in Super Paper Mario) is the main quest of the game.
  • In The Legend of Zelda: Ocarina of Time, the main quest involves awakening the seven sages of seven elements to banish evil from the land of Hyrule.
  • The number of Koopalings on Super Mario Bros. 3 and Super Mario World. It is also the number of worlds on Super Mario World, not counting the Star World or the Special course; and it is also the number of worlds on Super Mario Bros. 2.
  • The 7 is a group of deadly mercenaries that kidnap the protagonist's family in the upcoming video game Kane & Lynch: Dead Men.

In sports

In other fields

International maritime signal flag for 7
  • Seven is the smallest positive integer requiring more than one syllable in English.
  • The British fifty-pence and twenty-pence coins are heptagons, with the sides curved to give them a constant diameter. Adding them gives you seventy pence
  • The Kulin people of Australia living near the Dandenong Ranges traditionally have seven seasons. Some of the Native Americans of Montana also have seven seasons: chinook season, muddy spring, green summer, gold summer (or dry summer), 'Indian' Summer, late fall, and cold winter.
  • The United States Constitution, as drafted in Philadelphia in 1787, was composed of 7 Articles.
  • The United States declared Independence in the 7th month of 1776.
7 playing cards of all four suits
  • In a standard deck of playing cards the 7 of Diamonds is the only diamond card that can be viewed as upside down when reversed.
  • Lotto Super 7, a Canadian-lottery game

Seven is also:

Names and titles

  • Sevens, a card game.
  • An agency of photojournalists founded by seven photographers.
  • Canadian fashion photographer Sev Seven.
  • California graffiti artist Seven
  • In the Fushigi Yuugi series, the four beast gods each have seven warriors, the Genbu Seven, the Byakko Seven, the Seiryuu Seven, and the Suzaku Seven.
  • In the Catalan culture, seven is present in a lot of popular stories like "Les set cabretes i el llop".
  • Number 7 is a popular brand of Canadian cigarettes.
  • "The Seven", also written: "The Se7en" is an exclusive grouping of dental surgeons.
  • 7UP is the name of a popular soft drink.
  • 7-Eleven is the trading name of a chain of convenience stores based in the U.S.
  • Seven Jeans, also known as Seven '7' for all Mankind, a brand of designer jeans.
  • 7 (New York City Subway service), a service of the New York City Subway
  • 7-ip is the name of an Australian satellite and wireless technology start up
  • The Ultra Series has two heroes with "Seven" in their name: Ultra Seven and Ultra Seven-21.
  • SEVEN Networks is a US company producing mobile email software.
  • The circle 7 logo used by numerous ABC network O&O stations in the United States.
  • In a survey in England seven was discovered to be the most common lucky number in the 2000 people that were surveyed.

Notes

  1. ^ Georges Ifrah, The Universal History of Numbers: From Prehistory to the Invention of the Computer transl. David Bellos et al. London: The Harvill Press (1998): 395, Fig. 24.67
  2. ^ "21Then Peter came to Jesus and asked, 'Lord, how many times shall I forgive my brother when he sins against me? Up to seven times?' 22Jesus answered, 'I tell you, not seven times, but seventy times seven.'". [1] The value of 490 suggested by Jesus has been the source of much debate among scholars. For example, did he actually mean to impose a limit at 490, or did he only mean that the number of times (one should be forgiven) is to be ongoing? Most conclude the latter. Alternatively, it may be that the New Testament's mention of seventy "times" seven is a mistranslation of the original Hebrew based on the statement of Lemech (Genesis 4:24) that "If Cain shall be avenged sevenfold, then for Lemech it shall be seventy-sevenfold."
  3. ^ Matte, Jared. "Sonic Encyclopaedia: Sonic the Hedgehog". The GHZ. Retrieved 2007-05-12.

See also

References


  • Wells, D. The Penguin Dictionary of Curious and Interesting Numbers London: Penguin Group. (1987): 70 - 71