From astonishing, amazing and surprising science and history facts to the little-known stories hidden inside bigger events, The Big Book of Facts is a fascinating tour through our weird and interesting world. You'll learn about the earth and its history through absorbing stories and interesting tidbits. Did you know ... Babies start laughing at just a few weeks old; there are ten discernible types of laughter; and laughter spurs our appetite for food? Like fingerprints, every tongue on Earth has a unique print? The history of the U.S. Postal Service, including the Pony Express, ... and the short-lived (but legal) practice of mailing children? Hand washing was not always common through history; toilet paper was invented in the 1400s, and Sir John Harington invented the flushable toilet for Queen Elizabeth I? Though they are all differently shaped by virtue of being an assembly of water droplets, there are ten basic kinds of clouds? A basic and quick history of cash in America, including Alexander Hamilton and the Bank of the United States, Benjamin Franklin's efforts to thwart counterfeiting, $100,000 bills, and the fact that more than 85% of the world's money is digital only? Though Shakespeare mentioned Valentine's Day in "Hamlet," sending paper cards to a beloved wasn't a fad until the eighteenth century, and by the 1840s, insulting Valentine cards also became common? Government agencies in the U.S. and France both agree that the measure of a second is determined by how long it takes a cesium atom to vibrate just over nine billion times? The history of children's games such as hide-and-seek, blindman's bluff, and jacks that date back to the ancient Greeks and Romans? And much, much more.