Number 18

A page of the Numeropedia - the Special Encyclopedia of Numbers

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Number 18 in History & Gov.     Number 18 in Math.     Number 18 in Sports      Number 18

[Astronomy]  The number of minutes between the first man, Neil Armstrong and the 2nd man, Edwin A. “Buzz” Aldrin, landing on the Moon.

[Astronomy]  The number of natural satellites of the planet Saturn.

[Astronomy]  The astronomical twilight is when the center of the (refracted) Sun is 18o below the horizon.

[Chemistry]  The atomic number of Argon (Ar).

[Chemistry]  The number of electrons that can reside in a shell is 2n2, i.e., 2, 8, 18, 32, 50, 72 and 98.

[Chemistry]  The number of groups in the periodic table of the elements, numbered by 1-18 (recommended by the International Union of Pure and Applied Chemistry) or by another way: 1A to 8A and 1B to 7B and 3 groups (8-9-10) combined into group 8B.

[Education]  The age of a typical high school graduate.

[Education]  The legal age of adulthood, typical in many countries.

[EECS]  18(W, KW or MW) is one of standard numerical values for resistors (of tolerance class 5%). 18pF (picofarads) is one of standard numerical values for capacitors.

[Language]  Prefixes: Octodeca-, Decennoct-…

[Language]  The number of letters in the Scottish Gaelic alphabet: A, B, C, D, E, F, G, H, I, L, M, N, O, P, R, S, T and U.

[Measure]  Length of a person’s forearms, from the elbow to the middle finger tips, is cubit: 1 cubit = 6 palms = 24 digits = 18 inches = 457.2 mm.

Roman cubit: 17.5 inches = 444.5 mm. Egyptian cubit  = 20.63 inches = 524 mm = 27.5 digits or often 28 digits.  A digit is the width of one finger, ¾ of an inch, 19.05 mm.

[Phone]  The emergency telephone numbers dialing within Guadeloupe are 17 and 18.

[Science]  Prefix: Exa- = 1018.

[Science]

 American British Number (no entry) septendecillion 10102 septendecillion nonillion 1054 nonillion quintillion 1030 quintillion trillion 1018 trillion billion 1012 billion milliard 109

[Tech.]  Nickname for moving trucks: 18-wheeler.

[Trivia]  Modernly, the 18th wedding anniversary is named porcelain (or cat’s eye) anniversary.

[Trivia]  Pack of soft drink cans or bottles: 4, 6, 12, 18, 20, 24, 30 or 36.

[Trivia]  The number of eggs in a carton: 6, 12, 18 or 36.

[Zip]  The values of the US non-denominated first-class postage stamps and later values, for the first ounce, starting 14 September 1975 at 10¢ to 44¢, in May 2009.

 Series * * A B C D E F G H * * * * * * Value (¢) 10 13 15 18 20 22 25 29 32 33 34 37 39 41 42 44

[Trivia]  The number of branches of weaponry of traditional Chinese military arts. They are grouped into:

1-  Long range: staff, kuan-dau, spear and sword.

2-  Short range: dagger and ax

3-  Both: three-section staff and nine-section whip chain

4-  Others: tiger fork/trident, da-dau/darn-dau, twin-hooked sword and straight sword…

(Not completed yet. Not included: firearms, cannons, rockets and catapults).