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There are more bacteria in your mouth than there are people in the world.
When Gabriel Fahrenheit invented the first mercury thermometer, he called "zero degrees" the lowest temperature he was able to attain with a mixture of ice and salt. For the upper point of his scale, he used 96°, which he measured as normal human body temperature (we know it to be 98.6° today because of more accurate thermometers).
Every 10 seconds, a person in the United States goes to the emergency room complaining of head pain. About 1.2 million visits are for acute migraine attacks.
This year, an estimated 1.4 million Americans will have a new or recurrent heart attack.
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.