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.

An oil tanker, also known as a petroleum tanker, is a merchant ship designed for the bulk transport of oil. There are two basic types of oil tankers: the crude tanker and the product tanker. Crude tankers move large quantities of unrefined crude oil from its point of extraction to refineries. Product tankers, generally much smaller, are designed to move petrochemicals from refineries to points near consuming markets.

Deadweight tonnage is a measure of how much weight a ship is carrying or can safely carry. It is the sum of the weights of cargo, fuel, fresh water, ballast water, provisions, passengers, and crew.

A utility cooperative is a type of cooperative that is tasked with the delivery of a public utility such as electricity, water or telecommunications to its members. Profits are either reinvested for infrastructure or distributed to members in the form of "patronage" or "capital credits", which are essentially dividends paid on a member's investment into the cooperative. Each customer is a member and owner of the business with an equal say as every other member of the cooperative, unlike investor-owned utilities where the amount of say is governed by the number of shares held.

Ohio started the month of July with its pedal to the metal. The Buckeye State became the 34th state to adopt the 70 miles-an-hour speed limit. Drivers can now do up to 70 on more than 570 of Ohio's 1,332 miles of interstate highway. Congress repealed the 55 mph national limit in 1995. Despite predictions of calamity and carnage on the highways, the National Highway Traffic Safety Administration reported in October 1998 that "the traffic death rate dropped to a record low level in 1997". That pattern has continued since then.