On this date in 1776, rebellious colonials launched the first modern democracy, an experiment in government controlled by the people themselves. America succeeded so well that virtually the entire world later adopted democracy with its guarantee of personal rights.

Plasma is one of the four fundamental states of matter (the others being solid, liquid, and gas). Heating a gas may ionize its molecules or atoms (reducing or increasing the number of electrons in them), thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions.

A rule change was enacted before the 1974 National Football League (NFL) season to add one sudden death overtime period (15 minutes) to all preseason and regular season games. If no team scored in this period, the game would result in a tie. This rule was enacted to decrease the number of tie games. The first ever regular season overtime, a September 22 game between the Pittsburgh Steelers and the Denver Broncos, ended in a 35-35 draw. It was not until November 10, when the New York Jets defeated the New York Giants, 26-20, that an overtime game would produce a winner.

The Doppler effect (or Doppler shift), named after the Austrian physicist Christian Doppler, who proposed it in 1842 in Prague, is the change in frequency of a wave (or other periodic event) for an observer moving relative to its source. It is commonly heard when a vehicle sounding a siren or horn approaches, passes, and recedes from an observer. The received frequency is higher (compared to the emitted frequency) during the approach, it is identical at the instant of passing by, and it is lower during the recession.

The Mayan languages form a language family spoken in Mesoamerica and northern Central America. Mayan languages are spoken by at least 6 million indigenous Maya, primarily in Guatemala, Mexico, Belize and Honduras. In 1996, Guatemala formally recognized 21 Mayan languages by name, and Mexico recognizes eight more. The Mayan language family is one of the best documented and most studied in the Americas. Modern Mayan languages descend from Proto-Mayan, a language thought to have been spoken at least 5,000 years ago.