While Master Gardener and sundial enthusiast Bryan Preas wears a watch, when he’s at the 78th Street Heritage Farm or carrying a pocket sundial from his collection, he doesn’t need a modern time-keeping device. He can turn to any number of sundials to get an approximate reading of solar time that can be compared to standard time.
Preas said sundials are a way to utilize ancient technology and a great way to connect with history and science. He added that public sundials can be found at Fort Vancouver, Clark College and the 78th Street Heritage Farm, which the Clark County Washington State University Extension uses for research and experimental farming. In 2015, Washington State Master Gardeners built a human sundial at the property. The human acts as the gnomon, the part of the sundial that casts a shadow, by standing on a middle section that faces true north. The middle section tells the months of the year for the human gnomon to stand on for a more accurate reading of time.
Last week, Preas acted as the gnomon by standing in the beginning portion of August and raised his arms. The shadow he casted fell in an area that could be interpreted as 10:45 a.m., which corresponded to the time on his watch. To figure out the time of sunset, Preas stood in a marked sunset circle and positioned himself back toward the area indicating Aug. 3, and his shadow indicated sunset would be between 8 and 9 p.m., which also happened to be the general position of where sunset would be on the horizon line. Sunset on Aug. 3 was at 8:37 p.m. according to timeanddate.com. “I like it because it’s a way to connect to history. One other thing that intrigues people [about sundials] is the connection to science,” Preas said.
The oldest known sundial was made in Egypt in 1,500 B.C., making the sundial the earliest type of timekeeping, according to Britannica.com. The ancient Greeks laid the groundwork of trigonometry by utilizing the sundial, Preas added.
Preas said there are many types of sundials and even has some old pocket-sized ones in his personal collection. Along with his pocket sundials, Preas made his very own version of the shepherd’s dial with a wine bottle, paper and metal. The shepherd’s dial measures the length of the sun’s shadow compared to the angle of the sun’s shadow.
While Preas demonstrated his self-made shepherd’s dial, the standard time on a watch read 10:15 a.m. When he pointed the shepherd’s dial towards the sun, the shadow casted a little bit past the 10 o’clock line.
Preas said if people wanted to use a sundial as an accurate way to tell time, a lot more goes into its placement than plopping it down as a yard ornament.
For example, the Portland Metro Area sits around the 45-degree latitude line. Preas explained the gnomon, the straight edge piece that ultimately casts the solar time shadow, should then be placed at a 45-degree angle, and the sundial must be facing true north, which can be achieved with a compass.
Preas explained when clocks were first invented they were typically inaccurate, and clock workers would refer to sundials to reset the clocks when the gnomon shadow cast at noon.
Sundials ultimately gave way to standard time zones with the westward expansion of railroads in the 1800s, Preas said. Each municipality had a local time based on a sundial, which led to the creation of standard time zones for an easier set time. Preas added that the Portland area sits roughly 12 minutes ahead of Pacific Standard Time, so the sundial at Clark College has been adjusted past the 12 o’clock mark to reflect the proper 12-minute advance.
The interactive human sundial at the 78th Street Heritage Farm will be on display during the Starry Night at the Farm event on Aug. 22. Registration is still available eventbrite.com/e/starry-nightat-the-farm-tickets-658730710287.
