Thanks to Galileo, it's common knowledge that the Earth orbits the sun. What's not as commonly known is that the sun - and our entire solar system - is orbiting around a massive black hole at the center of the galaxy. It takes 225 million Earth years to make one loop around the Milky Way. A small group of science enthusiasts thinks we should all stop and ponder this and other amazing facts about our place in the universe once in a while, and they’ve declared a holiday this Thursday for exactly