7
7 is a prime number.
1, 3, 4, 7, 11, 18, 29... A Lucas number.
= 2 - 1A Mersenne prime.
There are seven days in a week.
Hept- or Sept- means seven. A heptagon is a figure with seven sides and a heptachord is a seven-stringed musical instrument. A septennium is a period of seven years and September used to be the seventh month in the year, but not any longer.
The Seven Deadly Sins are avarice, envy, gluttony, lust, pride, sloth and wrath (listed in alphabetical order, not order of wickedness). (they did not have geocaching back then)
Netball and water polo are both played with teams of seven players.
In Britain the 20p and 50p coins both have seven sides.
7-Up is a soft drink. It was invented in America in the 1920s by Mr C L Griggs of Missouri who originally called it Bib-label Lithiate Lemon-Lime Soda. With a name like that sales were poor even though the drink tasted good and so Mr Griggs set about changing the name. After six attempts he came up with 7-Up, or so the story goes. 7-Up is also the name of a card game.
John Sturges’s 1960 western The Magnificent Seven is about a Mexican village that hires seven gunmen for protection from bandits. The story is based on an earlier Japanese film made in 1954 - Akira Kurosawa’s The Seven Samurai.
Ask a number of different people to give you any number between one and ten, and most will choose seven. Ask people to name their favourite number between one and ten, and again most will say seven.
In 1956 George Miller wrote an article The Magical Number Seven Plus or Minus Two: Some Limits on Our Capacity for Processing Information. This showed that the amount of information which people can process and remember is often limited to about seven items. One example of this is called the digit span.
Ask someone to repeat back to you exactly what you say. Begin with four digits chosen at random e.g. 6 6 2 5. Then give them five digits e.g. 5 8 4 5 0, then six, and so on. Carry on increasing the number of digits until they make a mistake. The longest number of digits they get completely right is called their digit span and for most people this is about seven digits.
Suppose someone is shown a pattern of dots for a very short time - just one fifth of a second - and they are asked to count the number of dots they saw. If the number is less than seven they will be right almost every time, but with more than seven, they will make lots of mistakes.