There were 272 million visits to U.S. national parks during the 2007 calendar year. Source: National Park Service

The fastest a giraffe has been recorded running is 34.7 miles per hour. Source: San Diego Zoo

On today’s date in 1969, Neil Armstrong became the first man to walk on the moon. Shortly thereafter, Buzz Aldrin became the second. Source: National Aeronautics and Space Administration (NASA)

On today’s date in 1814, firearm innovator Samuel Colt was born in Hartford, Conn. Source: PBS

The world population of Caribou is about 5 million. Source: Alaska Department of Fish and Game

A giraffe’s feet are 12 inches wide; its legs are 6 feet tall. Source: San Diego Zoo

There were 66 nuclear power plants in the United States in 2007. Source: Energy Information Administration

The word "smallpox" comes from the Latin word for "spotted" and is a reference to the bumps that appear on the body of a person who has the disease. Source: Food and Drug Administration

About 19 percent of the total net electricity generated in the United States comes from nuclear power. That’s about equal to the amount of electricity used in California, Texas and New York, the three most populous states. Source: Energy Information Administration

About 92 percent of the coal used in the United States is used for generating electricity. Source: Energy Information Administration