X-rays add bony style to Google doodle homepage

Monday's X-rays Google homepage honors the invention's 115th anniversary.

Nope, it's not Halloween again. Google's bone-themed homepage on Monday pays tribute to X-rays. These invisible rays were discovered 115 years ago.

The monochromatic image of bones, keys, and lost treasures should be familiar to many Google users. While the world is well acquainted with X-rays and their many applications, few know the man who discovered them: German physicist Wilhelm Rontgen.

On November 8, 1895, Rontgen stumbled upon strange lab results, hints that he had found a new kind of ray. He named his discovery X-rays simply because he didn't know what else to call them. X is a regular stand-in for mysterious elements in math and science, so the term seemed appropriate. After two weeks of tests, Rontgen took the first X-ray print. His wife was the first model. After looking at the skeletal image of her hand, she reportedly said "I have seen my death!"

This form of electromagnetic radiation has an itty-bitty wavelength – smaller than over-the-air TV signal, smaller than microwaves, smaller than visible light. The only major category of electromagnetic radiation tinier than X-rays is gamma rays, which come from sub-atomic particle interactions – and gave the Hulk his powers (if you believe in that kind of thing).

Google went the extra mile with this X-rays doodle by giving the image a faint flicker. Animations are slowly becoming more common with these doodle. Newton got a falling Apple. Pac-Man got a fully functional board, which you can still play, by the way.

Which has been your favorite? Let us know in the comments.