It's Nicolaus Copernicus' 540th birthday, and Google marked the day with a lovely medieval model of the heliocentric solar system. Why? Because Copernicus was the first person to say what every kindergartner now knows: "The Earth goes around the sun."
Fun fact: Copernicus pulled this off without a telescope, having pre-dated telescope pioneer Galileo by about a century.
Another fun fact: Despite the fact that his scientific ideas were borderline heresy ("What? the Earth isn't the center of the universe?"), Copernicus wasn't executed.
(This may be because he only published his seminal work, "On the Revolutions of the Heavenly Spheres," on his deathbed at age 70.)
You can read more on astronomer and his pivotal ideas by clicking on the Google Doodle (today only!), or in the following stories: