## Thursday, March 11, 2010

### Making A Simple Astrolabe for Kids

While the little ones are working on telling time on our analogue clocks today, the older children are learning to tell time the 3rd century BC way, with an astrolabe.

An Astrolabe is a really old, and I mean really old, computer, used for navigation, measurement, and telling time, among other things. Tom Wujec has an excellent video introduction to the astrolabe, here, on YouTube.

Basically, it works by measuring the height, in degrees, of a fixed point in the sky, like a star, or the sun, and then checking against a built in star chart to find the time of day, on the particular date, your fixed point would be at the height you measured. It sounds fairly complicated, but it's actually quite elegant in it's simplicity.

We followed instructions, and used a couple of printouts from the Center for Science Education, to make, and use our own simple astrolabe with tape, string, glue, scissors, thin cardboard, a hole punch, a washer, a mater printout, and a rete/chart printout.

Basically, we glued the mater printout to a piece of thin cardboard...

...cut it out...

...poked a hole through a marked spot, and attached a string, with a washer to weight it down, and taped a piece of a straw onto the top.

Then, we used the device to measure the height of the sun (we let the sunlight tunnel through the straw onto our hands, instead of looking through the straw, directly at the sun).

Finally, we recorded the time we took the measurement, and the height of the sun, on the chart.

Now, tomorrow, if we measure the height of the sun, at the same time, our measurement should be the same as today's.

Obviously, making the first star chart would have been a tedious, detailed work. It's not surprising then, that this particular timepiece was originally made, and used by mathematicians, and astronomers.

It's great to be a homeschooler.

Debbie said...

You always have the neatest ideas for all of your kids, to keep them interested in learning. I have heard of an Astrolable before but to see and read how it really works is pretty neat!

Ticia said...

I've read of astrolabes in stories before, but hadn't ever seen how they worked. I've marked this down for when we get to this point in history.

Anonymous said...

See www.astrolabs.org for a more complete description of the types of astrolabes and a template that can be downloaded and printed to make a mariner's astrolabe. The instrument described is more correctly a quadrant.

An Almost Unschooling Mom said...

Very interesting. I think I'll revisit this with the kids - thanks.

Anonymous said...

Actually, I think the altitude will change over time. What happened over the next few days/weeks as you continued to take measurements?

An Almost Unschooling Mom said...

Anonymous - It's been a while, so I'm not sure, but if I remember right, we were studying how the device worked, not trying to prove if it worked - so I'm not sure we did follow-up experiments. Perhaps we need to come back to this one!

Anonymous said...

Thanks for this wonderful resource!
Pepe