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Aspirin is the most widely used drug in the world. It has even been recognized as such by the Guinness Book of World Records.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Egg cells are about the size of a grain of sand. They are formed inside of a female's ovaries before she is even born.
Astigmatism is the most common vision problem. It may accompany nearsightedness or farsightedness. It is usually caused by an irregularly shaped cornea, but sometimes it is the result of an irregularly shaped lens. Either type can be corrected by eyeglasses, contact lenses, or refractive surgery.