Astrological Lore in Herodotus

Herodotus (5th century BCE) records that “gold is calculated to be thirteen times the value of silver” (Histories 3.95). I can’t help but wonder if this is an idealized value calculation based on the relative periods of the moon and the sun. The following metals were associated with the seven classical planets:

  • Saturn – Lead
  • Jupiter – Tin
  • Mars – Iron
  • Sun – Gold
  • Venus – Copper
  • Mercury – Mercury
  • Moon – Silver

One need look no further than the colors of the metals and luminaries to understand the association of gold with the sun and silver with the moon.

The sidereal period of the moon is 27.3 days, while the synodic period (the time from new moon to new moon) is about 29.5 days. However, because of the week of seven days (also based on the seven classical planets), it is common to think of the period of the moon as an idealized figure of 28 days. As such, there are almost precisely 13 (13 x 28 = 364) “moons” or lunar months in a solar year. It is difficult to consider it a coincidence, then, that gold is reckoned to be 13 times the value of silver.