The days of the week, the Harry Potter books, the notes in a normal major or minor scale, Major League Baseball postseason series, and the Pillars of the House of Wisdom in the Book of Proverbs are all things that come in groups of seven. The number of heavens in Islam and the chakras in Hinduism are two further groupings of seven.
The number of official measurements in the International System of Units, the number of major stars in the Big Dipper constellation, the cervical vertebrae of most mammals, the periods on the periodic table of elements, and the seven colours of the rainbow identified by Newton are all examples of groups of seven in science.
The number of blessings at a Jewish wedding, the strata of the Earth in Islam, the Hindu seven worlds in the universe, the Virgin Mary’s Seven Sorrows and Joys, and Jesus’ last words on the cross are all religious groupings of seven. There are seven days of creation in the Old Testament.
The seven seas, the seven continents, the seven hills of Rome and Istanbul, and the seven sages of Greece are all examples of groups of seven in the classical world.
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