Galileo Galilei's Compass

February 25, 2005 1:18 PM

Galileo's compass (with sound). Galileo Galilei's compass resembles a calculator. In Le Operazioni del Compasso Geometrico e Militare (Padua, 1606), Galileo describes over 40 operations that can be carried out with this instrument. Try using the compass yourself.
posted by matteo (6 comments total)

You can see Galileo's text here
posted by matteo at 1:19 PM on February 25, 2005

Hey, that's really cool! Thanks.
posted by whatnotever at 2:36 PM on February 25, 2005

That is really cool. But when you follow the flash walk-through of the military uses of the compass, it tells you a square of 3,136 soldiers should have 56 soldiers on each side. I don't get it.
posted by atchafalaya at 4:32 PM on February 25, 2005

Uh... 56² = 3136 is too hard?
posted by flabdablet at 6:38 AM on February 26, 2005

Incredible instrument... where can I get one? (And I thought these were nice compasses.)
posted by Zurishaddai at 8:46 AM on February 26, 2005

OK, by now you've all had your fun with Galileo's tool & I'm sure you're inscribing heptagons in circles & who knows what kind of deviltry. Amid all this excitement, something must be said about old-school compassin'. And when I say old-school, I mean downright primitive. All of Euclidean geometry can be constructed—you don't need Euclid's collapsing compass and a straightedge—with only

1. compass alone
2. an arbitrarily short straightedge + an arbitrarily short arc (+ center point)drawn on the page with a rusty compass
3. an arbitrarily short double straightedge (the two edges don't have to be parallel)
4. origami

(#1 is the Mohr-Mascheroni theorem, #2 except for the arbitarily short part is the Poncelet-Steiner theorem, and as for origami, heck, you can even trisect angles with it...)
posted by Zurishaddai at 6:37 AM on March 8, 2005