A Retired Burlington Doctor Designed a Sundial That Only Tells Time During a Solar Eclipse 

click to enlarge

• Ken Picard ©️ Seven Days
• Gottesman with a glass sundial designed by Daniel Wenger, a physics professor from California

For thousands of years, humans measured the passage of time using nothing but the shadows cast by the sun, a remarkable achievement that combined astronomy with precise mathematical calculations. When Bill Gottesman set out to design a sundial that only works on the rare occasions when the sun is eclipsed by the moon, the idea sounded like the setup for a joke: What's next, a sundial that only works in the shade?

Actually, the 66-year-old retired Burlington physician and sundial enthusiast has invented exactly that: a sundial that tells time during solar eclipses. Lest anyone think that Gottesman is just trying to capitalize on Vermont's totality fever ahead of the solar eclipse on April 8, rest assured that he's not selling his eclipse sundials. Anyone can visit his website, enter their city and state — or longitude and latitude, if their location isn't included in the website's database — and download Gottesman's design for free. The only hitch: The sundial works best if you're not in the eclipse's path of totality, which will include most of Vermont. The path of totality in our region stretches from Montréal in the north to Middlebury and Barre in the south.

• Courtesy
• A printout of the eclipse sundial for Burlington. To use, the sun's image would be projected onto the dial using a pinhole card.

Gottesman first thought up the idea for the eclipse sundial in the lead-up to the 2017 solar eclipse, which he watched from St. Louis, where he was attending the annual conference of the North American Sundial Society. Gottesman then partnered with Dan Axtell, an old high school friend and computer programmer living in Putney. While Gottesman did the mathematical calculations, Axtell figured how to make the sundial accessible and downloadable online, and thus, the eclipse sundial was born. The pair has since updated the website with new calculations to tell the time during the upcoming solar eclipse.

Gottesman became captivated by sundials while he was an undergraduate at Dartmouth College. While studying in Baker-Berry Library in 1977, the Scarsdale, N.Y., native came across a book on sundials. Though the mathematics seemed over his head at the time, "it just drew me in," he recalled.

Gottesman went on to become a family physician in Burlington. But after 11 years of practicing medicine, he burned out and left the profession without knowing what he wanted to do next.

So, why the pivot to sundials?

"I'm fascinated by all things mechanical," he said. "I love to build things, and sundials are a real challenge."

In fact, he has a player piano in his house that he's been rebuilding for more than a year. In 2018, he also built a telescope that sat outside the ECHO Leahy Center for Lake Champlain until it was vandalized and had to be removed.

Gottesman also loves math and collects slide rules. In his fifties, he enrolled in a course at the University of Vermont to learn spherical trigonometry, "just for the fun of it." Combining his love of tinkering with crunching numbers, Gottesman started building sundials — first as a hobby, then as a business, called Precision Sundials. The biz, now on hiatus, mostly served wealthier clients who could afford to spend several thousand dollars on a backyard sundial.

"I don't know that I ever made more than I put into it," he said.

click to enlarge

• Ken Picard ©️ Seven Days
• Bill Gottesman with his patented Renaissance sundial

During a reporter's visit to his home in Burlington's Hill Section on a sunny, near-cloudless day, Gottesman proudly showed off his collection of indoor and outdoor sundials with childlike enthusiasm, including several sundials that he designed and patented himself. They include one, dubbed the Renaissance, that sits in his front yard. It's composed of a large bronze helix mounted on a white granite base. When the sun reflects off the sundial's polished glass surface, it casts a sharp black line onto the helix, which, when properly adjusted for the month and date, tells the time to the minute.

"The interesting thing about sundials, for something that's so old, you'd think it's all been done before. It hasn't," Gottesman said. "There's new stuff all the time."

Indeed, Gottesman is continuing a long Vermont tradition of designing and building unusual sundials. James Hartness of Springfield, who served as Vermont's governor from 1921 to 1923, was an inventor who patented several designs of telescopes, lathes and sundials. Many of his creations are on display at the Hartness-Porter Museum of Amateur Telescope Making in Springfield. Russell Porter, an artist, engineer, amateur astronomer and polar explorer who also lived in Springfield in the late 19th and early 20th century, was himself an avid sundial designer and builder.

Gottesman's sundial collection also includes an intriguing modern one designed by Daniel Scharstein, a computer science professor at Middlebury College. Scharstein's sundial is completely passive, with no batteries or moving parts. Nevertheless, it's able to tell the time digitally, using two closely spaced parallel masks that display different numbers that change as the sun's angle shifts in the sky.

click to enlarge

• Ken Picard ©️ Seven Days
• A sundial alarm clock

Another piece in Gottesman's collection resembles a Rube Goldberg machine but is actually a sundial alarm clock. Built in the 1990s, it's based on an 18th-century French design that used sunlight to set off a cannon every day at noon — assuming, of course, the sun was shining — to let the townspeople know the time of day. Gottesman's modern version, made of plumbing fixtures, uses a magnifying glass to light the fuse of a firecracker to go off at a set time. A rude awakening, indeed.

For all the apparent simplicity of sundials, Gottesman noted that reading them accurately requires some basic knowledge of the Earth's position relative to the sun, one's precise geographic location, and the month and date.

"Actually, the sun is not a very good timekeeper," he said. Because the Earth's elliptical orbit is not uniform, he explained, the sun's angle doesn't change at a uniform rate. Hence, the figure-eight symbol found on many old globes and sundials, known as an analemma, which displays the changing position of the sun in the sky from a fixed point on Earth.

("Is this too much?" Gottesman asked with a smile.)

So where will Burlington's biggest sundial enthusiast view next month's solar eclipse? Gottesman confessed that he'll be watching in Dallas rather than Vermont.

"A 64 percent chance of clear sky," he said, citing theskylive.com, a website used by amateur astronomers and other sky-gazers. Based on historical weather data, the site lists the top seven places in North America for viewing the totality, four of which are in Texas. By comparison, the chances of sun in Burlington that day are only 44 percent.

Talk about throwing shade.