* Seven is often considered as a lucky number. There is no unique explanation for this. In Japan folklore, for instance, there are seven gods of fortune. Buddhists celebrate the seventh day after birth and July 7th is celebrated as a special holiday. An old game called hazard, played with two dice, is based on bets among which the sum of seven points on both dice has a special place. The sum of points of the opposite sides on every die (singular of dice) is also always seven (1+6, 2+5 or 3+4). Number seven has the highest probability as a sum in a throw of two dice.
Of course, a lot of slot machines show the winning combination as a sequence of numbers seven.
* Eden Hazard, a popular Belgian striker in soccer wears number seven - thus being faithful to his surname.
* Ancient people in different environments observed the moon cycles which last 28 days. If they are divided into four equal parts (each phase of the moon: new moon, first quarter, full moon, last quarter), we got the number seven which is the number of the days in the week. Many cultures named the days of the week by gods or planets (there were exactly seven known planets in antique if we include Sun and Moon): Sun - Sunday, Moon - Monday, etc.
As we can see in the table above, the deities gave the names to specific names of the week. In Anglo-Saxon naming calendar days were respectively called: Sunnandaeg, Monandaeg, Tiwesdaeg, Wodnesdaeg, Tunresdaeg, Frigedaeg, and Saeternesdaeg.
Sometimes names were simply called by their position in the week (for instance in Slovenia: Cetrtek - the fourth day, Petek, the sixth day), but that leads to even more variations with different starting points (sometimes the week is started with Monday, sometimes with Sunday). Through many years and misinterpretations, we got what we got now.image credit
* Pitagora pronounced number seven as a number of perfection (a sum of a triangle and a square) and his followers spread the idea so successfully people started to group many natural phenomena and other stuff by seven.
For this reason, we have seven natural wonders, seven ancient world wonders, seven steps in the musical scale, seven colors in the rainbow
(Newton proposed five at first but as a die-hard fan of Pitagora added orange and indigo later). In medieval times they also still believed there are seven planets and they were familiar with exactly seven (!) different so-called planetary metals.
* There are seven rows in the periodic table. There are also seven columns plus one with noble gasses (which by definition hardly make any impact in chemistry reactions). The pH scale of acidity/alkalinity is based around number seven - 0 for most acidic, 14 for most alkaline substances and seven for neutral value (like of pure water).
* Number seven is very important in Christianity. The world was created in six days and the seventh was for resting. There are seven deadly sins and seven virtues, seven joys and seven sorrows of the Virgin Mary, seven parables, seven angels, seven churches, seven seals, and seven trumpet plagues, ...
Seven virtues are: Chastity, Temperance, Charity, Diligence, Patience, Kindness, and Humility. Again, they are made of four cardinal and three theological virtues.
Seven is seen as a union of the Holy Trinity with four corners of the Earth. We can probably all recall the story about seven fat cows who were eaten by seven ugly skinny cows (Pharaoh and Joseph). In the Book of Revelation, we can find seven angels, seven churches, seven seals, seven stars, seven trumpets, ...). The Bible is originally divided into seven sections:
* The Law
* The Prophets
* The Writings and Psalms
* The Gospels and Acts
* The General Epistles
* The Epistles of Paul
* The Book of Revelation
Other religions put great importance on number seven as well: seven heavens are mentioned in several major religions, there are also seven levels of hell according to Dante. A similar concept is known from Hinduism. Muslim Pilgrims walk around Mecca seven times and seven repetitions is included in wedding ceremonies in different cultural environments.
And, by the way: the total of books in the Bible is 7 times 7.7 x 7 = 49
* Many cultures share stories about the magic powers about the seventh son of the seventh son. The powers vary but are frequently associated with longevity or even mortality. Did you know Rome was established on seven hills and is called Eternal City?
* Mathematician Alex Bellos organized a poll about favorite numbers among people on the web. All numbers were available but almost half of all participants (44 thousand approximately) choose numbers between 1 and 10. Seven was the indisputable winner with about 10 percent of participants proclaiming it for their favorite. He interprets the success of seven through its uniqueness and gives the next example:
* All numbers between 1 and 10 can be divided or doubled, yet still stay in the group, except seven:
* 1, 2, 3, 4, and 5 can be doubled (and the result stays within the group of 10)
* 2, 4, 6, 8, and 10 can be divided by 2, 9 with 3, and 5 and 10 with 5 (10 also with 10)
* 7 is unique in the group
* The seventh day of every Chinese Year is known as “All Men’s Day”. This is the day when everybody celebrates his birthday no matter when he or she was really born, sharing the birthday spirit with everybody else!
* Just like Isaac Newton many found the way to group similar things by seven, even if that meant to change the rules according to new discoveries. Seven continents or seven seas are just two examples of such doing.
* Number seven is very important in Harry Potter series (consisting of seven books, of course) too:
- there are seven Weasley kids,
- Harry has to destroy seven Horcruxes,
- Hogwarts has seven floors and you need to study seven years to become a certified magician,
- Ministry of Magic has seven levels,
- for a Quidditch, you need seven players,
* Fairy tales are particularly fond of number seven:
* There are seven dwarfs in the story about Snow White.image credit
* We have all heard about Wolf and seven kids.
* The Brave Little Tailor is sometimes titled as Seven at One Blow (he killed seven flies on his bread).
* Seven ravens is another, although less known fairy tale by Brothers Grimm.
* There were seven fairies in Perrault’s version of The Sleeping Beauty.
* Sinbad finished seven voyages.
* We are familiar with seven-league boots too...
* Seven is the highest number of objects a human mind can recognize and remember without grouping them or otherwise using mnemonic techniques. This memory working capacity, known from 1956 (Harvard University's Department of Psychology) is probably related to the number of so-called short-memory chunks. Later experiments showed there is no fixed number of chunks even if we consider the effect of aging and different distractions.
* It is widely accepted fact that cells in our bodies are completely replaced within every seven years. Skin is made of seven layers and is regenerated in seven days.
* Widely accepted psychological theory claims there are seven stages of grief:
* Some teachers of creative writing believe there are exactly even basic plots and each good story needs to have seven character types (although there could be more than one type in a specific character, who can, for instance, play the role of the protagonist and antagonist at the same time).
* You'll always get the same indefinitely repeating sequence: 142857, no matter which integer you divide with seven:
1 : 7 = 0,142857142857142857...
2 : 7 = 0,285714285714285714...
3 : 7 = 0,428571428571428571...
etc. (except for multiples of 7)
15 : 7 = 2,142857142857142857...
16 : 7 = 2,285714285714285714...
17 : 7 = 2,428571428571428571...
* It's believed the loving feelings in the couple vanish after seven years. Psychologists call it a 7-year itch. It's believed the occurrence of infidelity in marriages really highly rises after the seventh year of marriage.