Conventional ideas of an Hour arises by splitting Earth’s 360 degrees rotation around its own axis into 15 degree segments. However, ancient Indians split the 360 degree rotation into 6 degree units instead. This therefore corresponds to a time measure of 24 minutes. A 24 minute unit is a Nazhigai (நாழிகை) in Tamil language. Nazhigai is Ghatika or Ghati in Sanskrit.
The use of Nazhigai time units goes several centuries before the start of the common era. at that time, copper was used to make measuring instruments to track time in Nazhigai units. A very old Sangam text mentions a Kannal (கன்னல்) instrument and qualifies it with the phrase “of narrow water passage” (குறுநீர்). Using these instruments and announcing the passage of time in units of Nazhigai was a profession in itself (Nazhigai Kanakkar நாழிகை கணக்கர்). Those who measured the movement of stars and planets in the sky took the tile “the one who observes” (பார்ப்பனர்) an astronomer.
A temple measuring time in Naazhigai
Temple builders were familiar with the Nazhigai units and may have also been experts in assembling special stones to serve as a clock. They selected two types of special stones and built the inner ceiling of the Shiva temple in the town of Thittai in Tamil Nadu. Water vapor condenses on the carved surface of one of them during the night. However, it condenses on the surface of the other type of stone during day time. In addition, these two stones gather enough water to create a drop of water every 24 minutes. A drop of water falls on the Lingam in this temple every one Nazhigai. The knowledge of condensation and the use of it as a time measure may have originated earlier, when temples were constructed in moist caves.
Half Nazhigai represents a 3 degrees of rotation of the earth. Was this the smallest convenient measure of time in ancient times? The Vinadi unit is smaller than the Nazhigai unit. There are 60 Vinadis in a Nazhigai. It is too small a unit to be measured with any instruments known earlier. Traditionally the smaller units were based on phenomenon such as a blink or the time taken to pronounce a syllable.
Today, many in Tamil Nadu are only remember a time measure which is called a Jaamam (ஜாமம்). Seven and a half Nazhigais make one Jaamam. Pujas continue, even today, at every Jaamam in certain old Shiva temples. Astronomy texts in Sanskrit show the way to convert Nazhigai or Ghatika units into the Hora or Hour units. A Hora contains two and half Nazhigais.