How much skin covers the human body?

The call is close. Over the course of 12 hours in Granville, North Dakota, on February 21, 1918, the temperature rose 83 degrees. It went from –33 degrees Fahrenheit in the early morning to 50 degrees near the end of the afternoon. But in Fairfield, Montana, over the course of 12 hours on December 24,…

The light from a firefly comes from an area on the sides of its stomach. Fatty tissue located there contains air tubes and nerves that when stimulated give off oxygen. The oxygen combines with a pigment in the fat called luciferin, producing the familiar heatless light.

Whether the person is male or female, the number of hairs lost is the same, about 25 to 125 hairs. These are replaced by new hairs, unless the person starts balding.

Goose bumps are a vestige from the days when humans were covered with hair. When it got cold, the hairs stood on end, creating a trap for air and providing insulation. The hairs have long since disappeared, but in the places where they used to be, the skin still bristles, trying to get warm.

As of 1990, 53 percent of Americans drink fluoridated water. Of these, 121 million drink artificially fluoridated water; 9 million drink water from naturally fluoridated sources.

Smiling is easier on the face than frowning. It takes 17 muscles to smile and 43 to frown.