MASTER GARDENER PROGRAM — MGs in the News
Published in: The Reflector • Sept. 30, 2015
WSU Extension Master Gardener program coordinator originates idea
We are surrounded by clocks: on our wrists and smart phones, our walls and dashboards. We can run our lives with military precision once we synchronize our watches, so it’s hard to imagine a life where the sole measure of time is the passing of the sun through the sky.
Early man undoubtedly noticed how the length and direction of shadows changed throughout the day. Sometime before 1500 BC, the sundial was created to mark the time by using shadows cast by the position of the sun in the sky.
In early times, the dials divided each day into 12 equal segments, so hours measured in the summer were longer than hours measured in the winter. In 1371, Ibn al-Shatir, an Arab astronomer and mathematician who also worked as a religious timekeeper, proposed that the hours be of equal time length throughout the year, and so they remain.
THE 78TH STREET Heritage Farm is home to a human sundial, a type of horizontal sundial where a person acts as the gnomon: the part of a sundial that casts the shadow. Using the longitude and latitude for the site, Master Gardener and sundial enthusiast Bryan Preas and a team of volunteers have created a sundial that allows users to participate in telling time in a unique way.
Here in Clark County, the 78th Street Heritage Farm is home to a human sundial, a type of horizontal sundial where a person acts as the gnomon (NO-mon – Greek for “the one that knows”): the part of a sundial that casts the shadow. Using the longitude and latitude for the site, Master Gardener and sundial enthusiast Bryan Preas and a team of volunteers have created a sundial that allows users to participate in telling time in a unique way.
A retired engineer and member of the North American Sundial Society, Preas indicates he has “always been interested in how the world works … connecting with the earth. Sundials are a way of capturing how the heavens work – how the sun moves.”
The sundial was the idea of Erika Johnson, WSU Extension Master Gardener program coordinator. Preas saw a connection between her interests and his and volunteered to lead the project. The two found an appropriate site at WSU’s Heritage Farm on 78th Street; the site is not only in sun all day, but it is easily accessible to visitors to the garden areas.
Preas faced some challenges in planning the site layout.
“Shadows cast by anything will change their length across the day and the year,’’ Preas said. “Shadows are the shortest at noon and longest at sunrise and sunset, and over the year, shadows are shortest in summer when the sun is highest and longest in winter when the sun is low.”
In creating the layout, he chose a size most appropriate for use in spring and fall as he felt more people would be in the gardens at those times.
Preas says that the sundial computations were “known to the ancients – the Egyptians were building sundials in 1500 B.C.”
While working on his own spreadsheet, he came upon a program on the web that simplified his work and enabled him to more quickly plot the coordinates of the stones.
The next challenge was the materials, which needed to be attractive and durable. Preas and Johnson talked to Chris Houlahan and Fred Davis at Mutual Materials, who donated the stones and provided invaluable advice, including recommending a stone engraver in Hillsboro, OR, with experience in engraving text into stone markers.
Fred Bass of Stone Art did the engraving at a deep discount, and the Master Gardener Foundation of Clark County provided the funds for the work. The stone cutting and engraving had to be accurate to within a fraction
of an inch to assure the sundial would work.
“Both of these suppliers came through admirably” says Preas. A local U-Haul lent the team a trailer to transport the heavy stones and the Nutter Corporation donated gravel and sand for the installation’s base layers.
“My step father, a retired truck driver drove the trailer and I can’t tell you how hard Master Gardeners Andy Maltoni, Bryan Preas, Doug Faulkner, Bruce Ingalls, Kirk Chamberlain, Mike McMurry, and Jon Bohannon labored to get this incredible thing in,” added Johnson.
Once the stones were completed, a group of Master Gardeners assisted Preas in laying out the correct positions and digging the holes to place the stones. When asked how accurate the dial is, Preas indicates that the stones and placement being accurate to a fraction of an inch equates to just a few seconds of time difference, and he feels the stones are correctly placed.
Preas reports that there are two other potential sources of inaccuracy in the sundial. One is the shadow of the person acting as the gnomon – if the person doesn’t stand on the correct position on the appropriate stone, the time will be off. The other inaccuracy inherent in using a shadow is how big that shadow is. Sundials usually use a thin pole or pointer to indicate the time. For a person to replicate this, they must hold their hands over their head with the palms together to form a pointer. In spring and fall, a normal sized person’s shadow can touch the numbers on the stones, but a shorter person will just see the direction that the shadow falls and will need to guess at the place it would touch the stones.
Sundials measure true local time, the local solar time at the exact location of the sundial, which will run either ahead of or behind our watches, which measure standard mean time for our time zone. This could be confusing prior to standardized time, because time would be different from town to town. Preas indicates that solar and mean time can differ by as much as 15 minutes. He hopes to eventually have a marking at the site with this “equation of time” explained for users.
Johnson has created a page on the Master Gardener website that explains the sundial in more detail (http://ext100.wsu. edu/clark/human-sundial-at-heritage-farm/). The site includes instructions on how to use the device – where to position their feet and how to read the clock.
Visitors will find the sundial east of the road leading to the community gardens. Gates are open from 8 a.m. to 5 p.m. Monday through Friday. The 78th Street Heritage Farm is located at 1919 NE 78th Street, Vancouver.
This article was written by Master Gardener, Susan Cox and submitted to the Reflector.
THE 78TH STREET Heritage Farm is home to a human sundial, a type of horizontal sundial where a person acts as the gnomon: the part of a sundial that casts the shadow. Using the longitude and latitude for the site, Master Gardener and sundial enthusiast Bryan Preas and a team of volunteers have created a sundial that allows users to participate in telling time in a unique way.