# Happy Birthday, Euler and da Vinci!

Happy Birthday to two prominent Leos today: Leonhard Euler and Leonardo da Vinci!

Euler is honored today with a Google Doodle (seen above)—you can spin the wireframe sphere around, but there is a lot of other information crammed into the Doodle. Down at the bottom are two representations of the Seven Bridges of Königsberg, a puzzle about whether you could create a path that crossed each bridge exactly once. Euler solved this problem and, in the process, created graph theory.

Up above is the formula V – E + F = 2, which relates the vertices (corners), edges, and faces of a polyhedron (for example, the icosahedron known to many gamers as a d20). The circular graph at the top is a representation of Euler’s formula, shown in the bottom right corner. Richard Feynman called this “the most remarkable formula in mathematics” because it ties together e, i, 0, 1, and ?. (The e, of course, is Euler’s Number.)

That’s just a short summary of Euler’s accomplishments. Euler would have been 306 years old today.

Not to be outdone, Leonardo da Vinci, who turns 561 today, was a painter, an anatomist, a sculptor, an inventor, a mathematician, a writer, and (among other things) the hero of a new TV series that just started last week. Da Vinci painted the Mona Lisa, now the most famous painting in the world, along with The Last Supper, without which geeks would not have a great tableau to parody whenever they need an iconic representation of an ensemble cast.

Da Vinci, of course, was also obsessed with flight: he made many drawings of flying machines, which inspired animator Jim Capobianco to create an animated short, Leonardo. Check out the Aerial Contrivance Workshop—in honor of da Vinci’s birthday, the “Complete Codex” package is on sale through Sunday, April 21. (Use code LEOBDAYS when checking out.)

You can watch the 10-minute film on Vimeo now (though I don’t know how long this will be available, so watch it soon!).

So, happy birthday to Euler and da Vinci!

Oh, and for you U.S. citizens, don’t forget today is Tax Day, too.

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