Ian: Hey, Scott! Guess what? I’ve got another explainer for you.
Scott: Oh, here we go again. What’s keeping you up at night this time?
Ian: It’s clocks! Do you know why they run clockwise?
Scott: Umm… because that’s just how they’ve always been?
Ian: (grinning) Not quite! Imagine long, long ago, before clocks existed. People used the sun to tell time. They used a tool called a sundial.
Scott: A sundial? What is that?
Ian: Picture a flat plate with numbers on it, like a clock face, and a stick in the middle. That stick is called a gnomon (NO-mon). The gnomon’s shadow moved as the sun crossed the sky.
Scott: Oh, cool! So, the shadow told them what time it was?
Ian: Exactly! And guess which way the shadow moved?
Scott: Umm… to the right?
Ian: Bingo! In the Northern Hemisphere, where most ancient civilizations were, the shadow moved to the right. So, when people invented clocks, they made the hands move the same way as the sundial’s shadow–clockwise!
Scott: Whoa! So, if clocks were invented in the Southern Hemisphere, they’d go the other way?
Ian: Yep, counterclockwise!
Quick Question for You!
What direction do you think a shadow move in your part of the world?
Try it out on a sunny day with a stick!