When do scientists believe the earth formed?

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

Sometimes likened to the shell that covers an egg, the layer of rock or crust that covers the surface of the earth is, on average, 22 miles thick.

Named for the patron saint of sailors, Saint Elmo’s fire is actually discharges of electricity that occur during storms. These discharges are seen as blue or bluish white lights at the tips of masts and bowsprits of ships at sea, as well as on church steeples and building spires on land.

In 1988, the United States was home to 49.4 million dogs and 57.8 million cats. The percentage of American households owning dogs was 37.2; the percentage owning cats was 30.

An average bolt of lightning raises the air temperature along its way to about 50,000 degrees Fahrenheit.

Broca’s area is the part of the brain associated with motor control of speech. It is usually located in the left but sometimes in the right inferior frontal convolution. It is named after its discoverer, the nineteenth-century French surgeon Paul Broca.