1) A single bolt of lightning can heat the surrounding air to temperatures five times hotter than the surface of the sun.

2) The Federal Reserve System, often referred to as the Fed, is the central banking system of the United States.

3) The world's first credit card was introduced in 1950 by Diners Club.

4) The blue whale is the largest animal to have ever existed, with an average length of about 82 feet (25 meters).