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13 (number) - Wikipedia, the free encyclopedia

13 (number)

From Wikipedia, the free encyclopedia

"Thirteen" redirects here. For other uses, see 13 (disambiguation)
13 10 3

13 (thirteen) is the natural number following 12 and preceding 14. It is the smallest integer with eight letters in its spelled out name in English.

Cardinal 13
thirteen
Ordinal 13th
thirteenth
Numeral system tredecimal
Factorization Prime
Divisors 1, 13
Roman numeral XIII
Roman numeral (Unicode) XIII, xiii
Binary 1101
Octal 15
Duodecimal 11
Hexadecimal D
Look up thirteen in
Wiktionary, the free dictionary.

Contents

[edit] Mathematics

Let ploggx denote the discrete logarithm according to the prime number p, i.e., the number l modulo p − 1 such that

g^x \equiv l \pmod{p}

Then 13 is the only prime number p such that for any two primitive roots g and h,

_p\mathrm{log}_gh \equiv\ _p\mathrm{log}_hg \pmod{p-1}

There exists an aperiodic set of thirteen Wang tiles.

Thirteen is the fifth lucky number. It is the fourth two-digit number in the number line.

[edit] In science

[edit] Astronomy

  • The Saros number of the lunar eclipse series which began on -2313 May 20 and ended on -1015 July 6. The duration of Saros series 13 was 1298.1 years, and it contained 73 lunar eclipses.
  • The known universe is currently thought to be about 13.7 billion years old, with an error of about one percent.
  • There are 13 zodiac constellations, which consist of the 12 signs in the astrological zodiac and Ophiuchus.

[edit] In religion

  • The number of participants at the Last Supper
  • Counting both Judas and Matthias, there were thirteen apostles
  • Thirteen was once associated with the Epiphany by Christians, the child Jesus having received the Magi on his thirteenth day of life.
  • In Judaism, 13 signifies the age of maturity (bar mitzvah) for boys
  • The number of principles of Jewish faith according to Maimonides
  • According to the Torah, God has 13 Attributes of Mercy
  • In modern day Wicca, thirteen is considered the maximum size of a coven, and in some traditions is the ideal number of members, and there are also 13 goals of a witch.[1]
  • In Sikhism, the number thirteen (13) is a number devoted to the remembrance of God, therefore it is also considered lucky by people who practice the Sikh faith.

[edit] A Significant Number

For various reasons 13 is considered a number carrying a special significance in many cultures.

[edit] Unlucky 13

See also: Triskaidekaphobia
The stall numbers at the Santa Anita Park show that 13 is considered an unlucky number in horse racing.
The stall numbers at the Santa Anita Park show that 13 is considered an unlucky number in horse racing.

Thirteen is regarded as an unlucky number in many cultures. Thirteen may be considered a "bad" number simply because it is one more than 12, which is a popularly used number in many cultures (possibly due to it being a highly composite number). When a group of 13 objects or persons is divided into two, three, four or six equal groups, there is always one leftover, "unlucky" object or person.

Unreasoned fear of the number 13 is termed triskaidekaphobia. Due to this fear, some tall buildings have resorted to skipping the "thirteenth floor", either by numbering it "14" (though it's really still the thirteenth floor) or by designating the floor as "12a" or something similar. Similarly, some streets do not contain a house number 13.

Some Christian traditions have it that at the Last Supper, Judas Iscariot, the disciple who betrayed Jesus, was the 13th to sit at the table, and that for this reason 13 is considered to carry a curse of sorts. However, there is evidence that 13 may have been considered unlucky in the pre-Christian era: the Code of Hammurabi, a collection of laws created ca. 1760 BCE, does not contain a thirteenth law.

According to another interpretation, the number 13 is unlucky because it is the number of full moons in a year. Actually two full moons in a single calendar month (referred to as a Blue Moon) only happens about every 2.5 years, so to say there are 13 full moons in a year is false. On average, there will be 41 months that have two full moons in a century, so a Blue Moon actually occurs about once every two-and-a-half years, and is in no way related to the number 13.[2] Women living in a natural environment tend to have their menses during a full moon.[citation needed] A twenty-eight day menstruation cycle is most typical, so a woman usually has 13 menses in a year. Supposedly, in the past, a woman who menstruated during a full moon might be thought a witch.

Early nursery rhymes stated there were thirteen months in a year because of the natural moon cycle that was used to count the lunar year. In England, a calendar of thirteen months of 28 days each, plus one extra day, known as "a year and a day" was still in use up to Tudor times. The lunar year was the easiest to count for cultures before scientific methods existed to observe the movement of the earth around the sun, so it was associated with worship of the pagan Great Goddess[citation needed] for thousands of years, which may be another reason for 13 becoming a taboo number. Taboo often is misunderstood when only half of the totem and taboo relationship is recognized. Among religions having totem and taboo characteristics, that which is taboo on a regular basis, may become quite sacred on special occasions.

The thirteenth of a month is likewise ominous, particularly when it falls on a Friday (see Friday the 13th), a Tuesday in the Greek and Spanish-speaking world, or a Monday in Russia. Months with a Friday the 13th must always begin on a Sunday.

In the Persian culture, 13 is also considered an unlucky number. On the 13th day of the Persian new year (Norouz), people consider staying at home unlucky, and go outside for a picnic in order to ward off the bad luck.

Most race car drivers consider 13 a very unlucky number, as a car carrying that number has never won the Indianapolis 500 or a NASCAR Nextel Cup race, and most all Formula 1 teams opt out of carrying the number 13 when car numbers are given out to teams on basis of points. Only once in recent years (1991, Ricky Johnson) has an AMA Motocross rider chosen #13 instead of #14. Some NASCAR tracks refuse to have a pit stall #13.

The career of Alex Rodriguez has taken a notable turn for the worse since donning the #13 for the New York Yankees.

In Tarot decks, the #13th card of the Major Arcana is Death (Tarot card). While Death is not typically interpreted literally, it is possible that this furthered the perception of 13 as an unlucky number.

[edit] Lucky 13

In Sikhism, the number 13 is considered a special number since 13 is tera in Punjabi, which also means "yours" (as in, "I am yours, O Lord"). The legend goes that when Guru Nanak Dev was taking stock of items as part of his employment with a village merchant, he counted from 1 to 13 (in Punjabi) as one does normally; and thereafter he would just repeat "tera", since all items were God's creation. The merchant confronted Guru Nanak about this, but found everything to be in order after the inventory was checked.

Several successful athletes have worn the number 13. Dan Marino, an American football player known for passing more yards than any other quarterback in NFL history, wore the number 13. Another athlete Wilt Chamberlain wore the number 13 on his jersey throughout his NBA career. Also, FIBA rules require a player to wear the number in international competitions (only numbers from 4 to 15 could be worn, and as there are 12 players, one must wear 13); Chris Mullin, who wore #20 in college and #17 in the NBA, wore #13 for both (1984 and 1992) of his Olympic appearances. Shaquille O'Neal wore #13 in 1996, Tim Duncan wore #13 in 2004. And Mats Sundin wears 13 in NHL. Alex Rodriguez also wears 13 for the New York Yankees

In Judaism, 13 is considered a lucky number. One explanation for this is that the word אחד echad, Hebrew for 'one' and thus a way of describing the unique God, has the numerological value of 13 according to the Gematria system.

[edit] In mythology

  • The number of circles, or "nodes", that make up Metatron's Cube.
  • The number of Norse gods (there were 12) at a banquet that was crashed by the evil spirit Loki (making 13) who killed one of the guests with a poison arrow.
  • The number of steps, according to Egyptian lore, between life and death.

[edit] Age 13

  • In Jewish tradition a boy becomes a bar mitzvah at age 13, when a ceremony is held and the boy reads from the Torah for the first time.
  • On October 13th, 2000, the 13th birthday is on the 13th day in October (golden birthday) on a Friday and on the same day... a full moon.
  • A period of 13 years is called a tridecennary, although that word is hardly ever seen in print, and only appears in one dictionary, the Oxford English Dictionary.

[edit] In media

  • In music:

[edit] In fiction

[edit] United States of America

  • The number of original colonies the United States was founded from. The original flag had thirteen stars, one for each state. New stars have since been added whenever a new state joins the union, but the idea of adding stripes for new states was soon dropped, so the American flag to this day has thirteen horizontal stripes: six white ones and seven red ones.
  • The Great Seal of the United States has:
    • 13 levels of the truncated pyramid,
    • 13 letters in "E Pluribus Unum", which appears in the banner running through the eagle's beak on the right side of the bill's reverse.
    • 13 letters in the phrase "Annuit Coeptis", which appears over the pyramid on the left side of the bill's reverse.
    • 13 stars above the Eagle,
    • 13 leaves on the olive branch,
    • 13 olives on the olive branch,
    • 13 arrows held by the Eagle, and
    • 13 bars on the shield.
  • The number of guns in a gun salute to U.S. Army, Air Force and Marine Corps Major Generals, and Navy and Coast Guard Rear Admirals Upper Half.
  • The Naval Jack of the United States has 13 stripes, 7 red and 6 white, the rattlesnake has 13 buttons on its rattle, and the motto "Don't Tread on Me" has 13 letters

[edit] In other fields

[edit] Historical years

A.D. 13, 13 B.C., 1913, 2013, 13th century (1201-1300), 1300s (14th century)

[edit] References

  1. ^ Katherine A. Gleason, Denise Zimmermann (2003). Complete Idiot's Guide to Wicca and Witchcraft. Alpha Books. 
  2. ^ http://www.obliquity.com/astro/bluemoon.html

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