Why 7 days in a week?

We work and slog for 5 days in a week to get the much deserved 2 days break. So many discussions on the permutations and combinations for an effective week schedule. With all the noisy drama behind, why do we have 7 days in a week. Let’s explore.

According to Induism, a planet (கோள் – Kol in tamil) denotes nothing but a celestial object and there are 9 planets. However, Science has identified Uranus, Neptune and Pluto (a dwarf planet?) which is not present in our temple list. Instead, we have Raagu and Kethu which is still not identified by Science.

Planets                                                                                 Days in a week

1. ஞாயிறு (nyayiru) = Sun                                ஞாயிறு (nyayiru) = Sunday
2. திங்கள் (thingal) = Moon                              திங்கள் (thingal) = Monday
3. செவ்வாய் (chevvai) = Mars                        செவ்வாய் (chevvai) = Tuesday
4. புதன் (pudhan) = Mercury                            புதன் (pudhan) = Wednesday
5. வியாழன் (viyazhan) = Jupiter                  வியாழன் (viyazhan) = Thursday
6. வெள்ளி (velli) = Venus                                வெள்ளி (velli) = Friday
7. சனி (Sani) = Saturn                                        சனி (Sani) = Saturday
8. இராகு (Raagu) *
9. கேது (Kethu) *


The intersection between planets and days of the week is so clear.

Why each day was designated to a specific planet?  Is this a thing present only in Induism?

Why did we choose to have 7 days of the week instead of 9? Or may be a whole number 10 just as the Romans tried for a while and gave up? What is the magic behind the number 7 that we intend to follow throughout history and throughout the World?

For this, let’s jump into the meaning of the days of the week:

English Old English Latin Japanese
Sunday sunedai (day of Sun) dies solis (day of the sun) Nichiyoubi (Sun)
Monday monedæi (day of Moon) lunae die (day of the moon) Getsuyoubi (Moon)
Tuesday Tiwesdæg (day of Tiw = Mars) Martis (day of Mars) Kayoubi (Fire =Mars)
Wednesday Wednesdei (day of Woden = Mercury) dies Mercurii (day of Mercury) Suiyoubi (Water = Mercury)
Thursday þursdæġ (day of Thor = Jupiter) Iovis Dies (day of Jupiter) Mokuyoubi
(Wood = Jupiter)
Friday Frīġedæġ (day of Frigg = Venus) dies Veneris (day of Venus) Kinyoubi (Gold = Venus)
Saturday Sæterdæġ(day of Saturn) Sāturni diēs (day of Saturn) Doyoubi (Saturn)

How is it the meaning of the week days follow the same planet even in Latin, Japanese? Why’s each day of the week assigned for a solid planet across the World??

Could it be that their influence (or radiation) is more on Earth on selected days of the week? If so, how do we measure it?

Why haven’t we conducted experiments to measure the influence of the planets in Earth?