Numerology guide
Why Is the Number 7 So Symbolic? The Seven Planets, the Week and the Scale
From the Seven Classical Planets to Numerology
Key takeaways
• Ancient observers knew seven moving bodies visible to the naked eye: the Sun, the Moon, Mercury, Venus, Mars, Jupiter and Saturn.
• These seven gave their names to the days of the week, directly or through Germanic gods.
• The number 7 also shows up in the musical scale and the colors of the rainbow, where Newton chose the number.
• In numerology, 7 is associated with introspection and the search for meaning.
The Seven Wandering Stars
To ancient observers, most stars kept the same positions relative to one another. Seven bodies, however, moved across that fixed background: the Sun, the Moon and five planets visible to the naked eye, Mercury, Venus, Mars, Jupiter and Saturn. The word "planet" comes from the Greek planētēs, "wanderer."
This group of seven deeply shaped ancient astrology and symbolism. The more distant planets, Uranus and Neptune, were only discovered in the 18th and 19th centuries.
The Days of the Week
The seven-day week linking each day to one of the seven bodies spread through the Roman Empire. English kept three of them directly and replaced the other four with Germanic gods equated with the Roman ones:
• Sunday · Sun's day · Sun
• Monday · Moon's day · Moon
• Tuesday · Tiw's day (Germanic god equated with Mars) · Mars
• Wednesday · Woden's day (equated with Mercury) · Mercury
• Thursday · Thor's day (equated with Jupiter) · Jupiter
• Friday · Frigg's day (equated with Venus) · Venus
• Saturday · Saturn's day · Saturn
Romance languages kept the Latin planets more visibly: French mardi (Mars), mercredi (Mercury), jeudi (Jupiter), vendredi (Venus).
Why this order? The order of the days doesn't follow the planets' order in the sky. It comes from an ancient system of planetary hours: the seven bodies, ranked from slowest to fastest (Saturn, Jupiter, Mars, Sun, Venus, Mercury, Moon), ruled each hour in turn, and the body ruling the first hour gave its name to the day. Run that 7-step cycle over 24-hour days and you get exactly Saturday, Sunday, Monday, Tuesday, Wednesday, Thursday, Friday.
7 Elsewhere
• The scale: the diatonic scale has seven notes (do, re, mi, fa, sol, la, ti).
• The rainbow: the light spectrum is continuous. Isaac Newton chose to divide it into seven colors, partly by analogy with the seven notes of the scale.
• The Seven Wonders of the Ancient World, the seven deadly sins, the seven days of Creation in Genesis: 7 often returns as a number of completeness.
7 in Numerology
Numerology links 7 to introspection, analysis and the search for meaning. In Cheiro's system it's tied to Neptune; in Vedic numerology, to Ketu, the lunar South Node. See life path 7 and our planets and numbers article.
It's striking that modern numerology doesn't link 7 to the seven classical planets, but to invisible or mathematical bodies (Neptune, Ketu). The symbolism of 7 as a number of mystery and inwardness won out over its astronomical side.
Frequently asked questions
Why does the week have seven days?
Several factors played a part: the seven moving bodies known in antiquity, the phases of the Moon (roughly seven days each), and the biblical tradition of the Sabbath.
Is 7 a lucky number?
It's valued in many cultures. In numerology, it's associated with introspection rather than luck.
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