Halley's Comet has left a great impact on our history and understanding of these mysterious "falling stars." When this comet passed Earth in August of 1835, for example, it was blamed for the New York City fire that kept going for several nights. The Seminole Indians in Florida saw the comet's long tail and believed it marked the day they would lose their independence. What's so intriguing about this space body? How come it just pops up around Earth every once in a while? And, most importantly, is it really dangerous?