The Sundial

Sundials - you may have seen them in your weird aunt’s garden growing up, on some obscure British documentary regarding solar worship, or maybe you are a watch nerd like me and heard that sundials predated modern watches but are shit compared to what we have now. You may be wondering how accurate they are, who used them, and how did they have a religious use. Or maybe you aren’t. Regardless, you now find yourself reading a short article on the history of sundials and some notable examples of their uses. Lucky you! You must be fun at parties.

               So let’s start with what is a sundial – a device with a circular or semicircular disc base, markers for hours or some way to signify time, and with a pointed angled pole in the center known as the gnomon (Greek for pole) that casts a shadow from the sun onto the markers etched or inscribed into the disc base. As the sun moves throughout the day, the shadow of the gnomon tells us what time it is using those markers.

               Ok, so now that you know what a sundial is, let’s understand its uses. There are a number of uses but let’s start with the most obvious: a clock. Our ancient friends created the sundial to be a clock. Humans have been fascinated by the passage of time and as soon as we could count the hours, we have been frustrated with people for being late. The sundial was one of the first, most common clocks and was even used well up into the 19th century to check the accuracy of mechanical clocks. A second use of sundials is in the study of astronomy. Early astronomers, such as the Greek Aristarchus of Samos, created sundials that marked the passage of time and seasons, by studying the sun. A third use of the sundial was for a religious function, they were used to mark important seasonal festivals and for marking the specific times of day used for prayer. An example of this would be the use of sundials during the medieval period to mark when Muslims were supposed to pray. In fact, most sundials from the golden age of Islam indicate times on the sundial for when prayer was supposed to occur.

               Some notable examples of famous sundials are the Egyptian shadow clocks that date to 1500 BCE.  There was at one point a belief amongst historians that even the Egyptian obelisks could have been used as large sundials to measure the passage of time, but this idea has since been discounted mostly. The Greeks seem to have been particularly fascinated with sundials, two examples would be the Hemicycle by Aristarchus of Samos. This sundial not only measured time but also a concept (that goes way over my head) known as seasonal hours depending on the length of the shadow. Another is an octagonal building known as the Tower of the Winds in Athens. The building, completed around 100BCE, had eight “planar” sundials facing the cardinal directions of the compass. The Romans, as always, stole a famous example from a rival tribe, the Samnites. They put this sundial on display in the city of Rome in 290BCE and the first original Roman sundial for the city was not built until over 100 years later.

               So, what killed off the sundial and relegated it to a garden ornament? Well, of course, the mechanical clock. Mechanical clocks started to come around in the 14th and 15th century and as they become more accurate with springs, pendulums, and gears, sundials started to disappear. They were stubborn as hell though, and lasted well into the 19th century to measure the accuracy of mechanical time keeping devices. So, next time that weird aunt with the sundial in the garden invites you over, make sure you regale her with the EXTREMELY exciting uses and past of the sundial.