Sundial Machines Under the Sidewalk

In the front of our school, we have a big sundial painted on the front walkway outside. It was painted on the sidewalk and it’s really neat! There’s a box that says each month and if you stand in the box of the month that we’re currently in, your shadow will point to what time it is! After lunch, we walked outside to check what time it was according to the big sundial. The kids each stood in the “September” box and saw that their shadows pointed almost at the 12. They asked me what time it really was and I showed them my phone – 11:55. There was a chorus of “Wow!” and “Awesome!” and “How does it do that????”


When we got back to our classroom, we sat down and I asked the kids how they thought it works. “How does the sun cast a shadow to exactly the right number?” Their answers were very funny and showed definite understandings and misunderstandings of the way the sun and Earth are related. Here are some of their guesses:

“I think it’s because the sun knows what time it is so it puts the shadow at the right spot.”

“Maybe there’s a giant machine under the sidewalk that controls the shadow to make it go the right way.”

“The sun makes a shadow on the ground and as the sun moves across the sky your shadow changes.”

We talked about it a little more and then I asked them another question: “Why do you think there are different boxes depending on what month you’re in? Why can’t there just be one box and we always stand in that box?” Again, many responses, many ideas…

“Well, you know how it’s a different time everywhere in the world? Like in Japan right now it’s night. So maybe it matters what box you’re in because it matters where you are in the world.”

“I think it’s because the sun rises and sets at a different time in the year. Like some days are shorter and some days are longer. Like right now it might be a short day but in October it’ll be a long day and then a short day.”

“Yeah, I think she’s right because I go to afterschool and when my mom picks me up right now it’s still light outside but in the winter, it’s almost dark when she picks me up. I think it matters how much daylight we have.”

I loved listening to their ideas of how the world works and why they think things happen the way they do. It’s clear that some of them have heard/read/discussed some information about the sun and Earth, light and time. It’s interesting how they take everything they learn and try to make sense of it! We did finally google it because they were begging me for the real answer of how that simple, yet complex sundial works. They were very proud that they at least got a few parts right!


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