Wednesday, July 15, 2015

If you've got the Sun, I've got the Time

Sundials fit nicely into that cluster of technology I'm so fond of. They are like Morse Code compared to text messaging, a Foxhole Radio compared to High Def TV or netcat compared to Firefox. These technologies trade ease of use for functional simplicity and a vast amount of utility.

OK, so I like sundials. Here's one that takes 10 minutes to make and requires minimal supplies. Our good friend's at NASA provide the paper template, you'll need to provide the scissors and tape. Here's my crudely constructed version:

Note that I snapped the photo at 8:59am, so the time isn't exactly right, but it's pretty dang accurate given all the variables involved.

Speaking of variables, this sundial ties together 3 factors: compass direction, latitude and of course, time. So in theory, if you know two of these elements, you can figure out the third. Paper compass, anyone? Pretty nifty, right?

Here are more sundials you can construct with minimal materials. I think this project is crying out for an Altoids Tin version, which would make for an updated version of this classic project. I should so get on that.


  1. It's easy to use a watch as a compass. Lay your watch flat so its face is parallel to the ground. In the northern hemisphere, point the hour hand toward the sun; halfway between the hour hand and twelve o'clock is South. In the southern hemisphere, point twelve o'clock toward the sun, and South is halfway between twelve o'clock and the hour hand. Be sure to subtract an hour during daylight saving time. If you want to be more precise, you might enjoy this exercise at my blog.

  2. @pbewig - thanks for the suggestion - I'll have to give it a try on our next sunny day. And of course, thanks for the programming exercise. I'll definitely flag this one to work on my next airplane flight. Your rock!