- With the naked eye, seven objects can be observed to move
relative to the stars: the Sun, the Moon, and the five planets
Mercury, Venus, Mars, Jupiter, and Saturn.
- Given the power of the Sun to heat the Earth, and the Moon
to move the tides, it was natural to assume that the planets
were also "godlike" in character, and from earliest
times they have been associated with the deities of various cultures.
(This was also the genesis of astrology, although in fact the
the planets have little or no effect on the Earth.)
Naming the planets after gods goes back at least as far as the
cultures of Mesopotamia, but the tradition was continued by the
Romans, using similar gods.
English, a hybrid germanic-romance language, uses the same names
for the planets as the Romans.
- Seeing significance in the number of these visible, moving
objects, the ancient Babylonians chose to organize their calendar
around a seven-day week.
The names of the days were taken from these objects/gods, and the Romans followed suit.
The Germanic tribes of northern Europe also adopted the seven-day
week, and substituted their own gods in the names of the days.
English continued to use the Germanic names for days, thereby
disconnecting them, for the most part, from the planetary names:
- Sunday: The Sun's Day => Sol's Day
Sol was the Roman god of the Sun.
- Monday: The Moon's Day => Luna's Day
Luna was the Roman goddess of the Moon.
- Tuesday: Tiu's Day => Mars' Day
Tiu was the Germanic god of war, corresponding to the Roman god
This is an appropriate choice given the planet Mars' blood reddish
- Wednesday: Woden's Day => Mercury's Day
Woden or Odin is sometimes described as the supreme Germanic
god, which sounds like the Roman god Jupiter.
Germanic tribes associated Woden with the Roman god Mercury.
Mercury was the swift messenger of the gods, an appropriate characteristic
for the fastest moving planet.
daily sent out his two ravens to gather information about the
world, and was also the god of writing.
Probably more important, Woden and Mercury were both bearers
of the dead to the afterlife.
- Thursday: Thor's Day => Jove's Day
Thor was the Germanic god of thunder and lightning, and since
Jupiter was known to throw a few thunderbolts himself, this seems
an understandable correspondence.
Jupiter, the supreme god, seems an appropriate choice for this
planet, given its brightness and the relative longevity of its
appearances (and as we now know, its huge size).
- Friday: Freya's Day => Venus' Day
Freya was the Germanic goddess of love and beauty, corresponding
closely to the Roman goddess Venus.
The planet Venus can be the brightest object in the sky besides
the Sun and Moon, quite beautiful and hard to miss when it is
far from the Sun, so this seems an understandable association.
- Saturday: Saturn's Day
Saturn was the Roman god of agriculture and of time; he was the
father of Jupiter, so his association with the farthest visible
planet seems appropriate.
The Germanic tribes did
not appear to have a similar god themselves, and they may
have adopted him as their own.
- If you know Spanish, the day names closely match the Latin
(except for Sunday, Domingo, "the Lord's Day"): Lunes,
Martes, Miercoles, Jueves, Viernes, Sabado.