Charts · 16

Seven, and why the week is in that order

Seven is the number a culture reaches for when it wants a set to feel complete: heavens, chakras, notes, colours, wonders, sins. Most of those are seven by choice. One of them is seven by arithmetic, and it is the one you use every day. The days of the week are named for the seven classical planets, but not in the planets’ own order. Step the hours and watch why.

♄Saturn · Sat♃Jupiter♂Mars☉Sun♀Venus☿Mercury☾MoonSaturdayhour 1 · ruled by Saturn

The mechanism

Put the seven classical planets in the ancients’ order, slowest to fastest across the sky: Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon. Give each hour of the day to the next planet in that order, round and round. A day has 24 hours, and 24 mod 7 = 3, so the planet ruling the first hour of each new day is three steps on from the one before. Follow the first hours and you get Saturn, Sun, Moon, Mars, Mercury, Jupiter, Venus: the week. Drawn on the circle, that step of three is the {7/3} heptagram.

The names are the same seven gods in every European language that kept them: Saturn's day.

Seven, in columns

Set1234567
Newton's spectrumOpticks, 1704. Newton saw a continuum and chose seven divisions to match the seven notes of the scale; indigo is there to make the count.RedOrangeYellowGreenBlueIndigoViolet
The scaleSeven notes of the diatonic scale, which is what Newton was matching.CDEFGAB
The weekIn the order the heptagram above produces.SundayMondayTuesdayWednesdayThursdayFridaySaturday
Its planetsThe seven classical planets: the bodies that visibly move against the fixed stars.SunMoonMarsMercuryJupiterVenusSaturn
The chakrasSeven in the modern Western scheme, coloured red to violet in that scheme since the twentieth century.RootSacralSolar plexusHeartThroatThird eyeCrown
A Journey Through LightThe seven spheres of my MA installation (2018), one per colour of the spectrum, the audience walking from darkness through the seven into ultraviolet.Death & RegenerationConsciousness & The BodyAncient WisdomHermetic FoundationsMythology as CodePerception & Invisible RealitiesAscent & Unity

The rows are not claimed to correspond, only to count. The spectrum and the scale do, historically: Newton picked seven bands so light and music would share a number. The week and its planets do, mechanically, as above. The rest is seven because seven had already become the number you reach for when you want a set to feel complete.

Seven, counted

  • 7 ± 2items a person can hold in working memory, in Miller's famous estimate. Miller, 1956
  • 1 in 10people name seven as their favourite number, the most popular answer in Alex Bellos's 44,000-person survey. His reason: of the first ten numbers it is the only one you can neither multiply nor divide within the group. Bellos, 2014
  • 7heavens in Judaism and Islam, with God above the seventh; seven circuits of the Kaaba; seven wedding blessings. MA research, 2018
  • 7higher worlds and seven underworlds in Hinduism; seven horses pull the sun god's chariot; seven gods of fortune in Japan. MA research, 2018
  • 7planetary spheres the soul descends through in the Hermetica, which is where the week, the metals and the days all inherit the count. Corpus Hermeticum; Black, 2010

Notes

The planetary-hours explanation of the week is ancient and documented: Cassius Dio, writing around 230 CE (Roman History 37.18–19), gives exactly this account, the Egyptians assigning each hour to a planet in the order of their spheres and the day taking the name of its first hour. The Chaldean order is by apparent speed against the stars, which the ancients read as distance: Saturn slowest and outermost, the Moon fastest and nearest. Newton’s seven colours are from Opticks (1704), Book I, where he divides the spectrum in proportion to the intervals of the musical octave; he had earlier used five, and added orange and indigo. Miller’s 7 ± 2 is from The Magical Number Seven, Plus or Minus Two (1956), and later work puts the honest figure nearer four. Bellos’s favourite-number survey is in Alex Through the Looking-Glass (2014). The cultural sevens and the seven spheres are from my MA research, VIC708, A Journey Through Light (2018), in which the audience walks from darkness through the seven colours of the spectrum into ultraviolet, where quotes painted in UV-reactive paint become readable. The table rows count; only the ones the text says correspond are claimed to.