Tag Archives: water clock

Read this now! Time is running out!

Hourglasses are good timers that are easy to use, so they’ve been part of people’s lives for centuries. My mom used to have a little one that measured 3 minutes—just right for boiling an egg.

The hourglass became a symbol for time itself, and just how quickly it seems to pass. Go into an old cemetery and you might see one carved into a tombstone—eeek!

On some computers a little icon of an hourglass shows up to tell you that your program is still loading.

By golly, I would have committed murder to own that Wizard of Oz hourglass when I was an art student, How about the lucky prop artist who got to design it!

If you ever saw the old Wizard of Oz movie with Judy Garland, you’ll remember that terrifying big hourglass that belonged to the Wicked Witch of the West. Here’s a website that tells how hourglasses are made. This one’s good, too.

Back to the beginning of The Western Civ User’s Guide to Time & Space

How to build a better water clock

Ctesibius of Alexandria. Believe it or not, this guy’s dad was a barber.

If you’ve been following this blog, you’ll remember that a couple of posts ago I ranted about how Egyptian water-clocks seemed impractical and I didn’t see how they could even function as clocks at all.

Well, apparently back around 270 bc, an inventor named Ctesibius (Teh-SEE-bee-us) of Alexandria thought the same thing. He identified two problems:

One) The water-clock wasn’t a clock, but rather a timer. It only worked while there was water in it.

Two) The water came out of the bung-hole at the bottom at different rates of speed: quickly when the jar was full, slowly as it grew empty. That’s because the weight of the water on top pushed down on the water that was escaping—less water, less pressure, slower dripping of water. That made it unreliable for keeping time.

So how did Ctesibius fix these problems? Well, he figured in order to keep constant pressure on the hole at the bottom, the water clock should always be full. So he set up a second jar of water to keep the first one filled. The second jar had a hole at the bottom that leaked water into the first jar.

THEN, a third, empty jar was placed under the first jar. Instead of telling the time by how much water had leaked out, this empty jar told time by how much water had leaked into it.

Ctesibius even made a float to put into the empty jar. As the water level rose, an arrow—attached to the float—pointed to the hour.

A tip of the hat to Heidi K. for sending me a link to this video!

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Ancient Egyptian water wristwatches never caught on