There's a strange set of numbers and months inlaid in front of the Domes. What is it?
The Mitchell Park Domes are a beloved Milwaukee landmark. People flock to the botanical gardens every season of the year, especially winter when they serve as a kind of oasis from the city’s harsh weather.
But if you come on a weekend, you may find yourself waiting in a long line stretching down the sidewalk and over one of the Domes lesser known features: a set of numbers that form a half circle around a center block that lists each month of the year. Bubbler Talk question asker Kate Collins is a member of the Domes, and she found herself wondering: what is this?
"Strictly speaking, they have a proper name of 'analemmatic sundials,' which are ground level and use anything vertical, whether that be a vertical rod or person, it’s the shadow of that upright thing that tells the time," says Douglass Hunt, the former owner of Modern Sunclocks in Scotland and the man who created the layout of the sundial in front of the Domes.
The type of sundial most people are familiar with are flat and circular, and have an upright triangle sticking up on top. That’s known as the gnomon, and its shadow is what indicates the time of day.
The clock in front of the Domes has two sets of numbers — one for daylight saving time and one for standard time — and it doesn’t have a traditional gnomon. Instead, the person interacting with the dial becomes the gnomon. That’s key to how an analemmatic sundial works.
"Unlike normal sundials that just have a fixed gnomon, analemmatic sundials require that upright thing, but it has to be moved along a scale of months in the middle to compensate for the changing seasons," Hunt explains.
That scale is known as the "zodiac walkway" and it’s necessary to getting the right time on the clock. The term “analemmatic” refers to the analemma: a diagram of how the sun’s movement changes in relation to a fixed point on earth. Basically as the seasons change, our distance to the sun also changes. So if a person wants to figure out what time it is, they have to stand on the right month on the zodiac walkway.
Paula Zamiatowski, a naturalist educator for the Domes, demonstrates. "With the Zodiac walkway, the very center of each block is the exact date, so that’s what you do, you actually go on [the month]. ... We stand here and we’ll pretend it’s a beautiful sunny day, and you put your arms up and I become the gnomon. It doesn’t matter if you’re short or if you’re tall, you still get the shadow where you need it," she explains.
Creating the layout of the clock takes a lot of math and includes figuring out which way the clock needs to face, how far apart the numbers need to be, and figuring out how big each of the month's tiles have be in order to get the right time.
Zamiatowski says, "What’s key is getting the formulas that you need to lay all this out, and it gets pretty complicated. … If you notice, this is not round, this is elliptical, cause we’re following the curvature of the earth."
That’s where Douglass Hunt comes in. His company created layouts based on these complicated formulas for places around the world, "From Australia to Alaska, from Tasmania to Tibet," he says (although he adds he's never had one placed in Russia or China).
Each of his designs are customized, based on the coordinates of where the clock will be placed.
"All we needed to know, basically, was the address of its intended location and that meant finding the specific latitude and longitude for that location, because every single layout anywhere in the world is absolutely unique," says Hunt.
For Zamiatowski, this sundial holds a special meaning. When she first started working at the Domes, the dial was painted onto the sidewalk by her late predecessor, Becky Loehe, who first came up with the idea to put in the clock.
She explains, "Back in 1998, Becky got all these calculations and painted one on a little farther to the front, then a few years later she had to have a heart transplant, so I took over painting every year and touching it up. And then when the designs for the plaza came about, no one wanted to part with this."
Now it’s a permanent part of the Domes. So the next time you find yourself waiting in line on a bright sunny day, you won’t need your phone to check the time, just look down.
If you're interested in making your own analemmatic sundial all you need is your zip code to create your own layout.