Joule, a unit of energy or work in the metric system of measurement. By definition, one joule is the work done when a force of one newton is exerted over a distance of one meter. (A newton is the force necessary to give a mass of one kilogram an acceleration of one meter per second per second.) The joule is an absolute unit—that is, it is based on mass rather than weight and hence is independent of the force of gravity. Another, less commonly used metric unit of energy or work is the erg. One joule equals 10,000,000 ergs. In the traditional English system of measurement, the foot-poundal is used in place of the joule. A foot-poundal is equal to approximately 1/25 of a joule.
You hear about global warming all the time on the news. If you wanted to help, what could you do? Well, you could start with a light switch.
Very little of the world's water is usable because of its high salt content, but a process known as desalination may help change that. How does desalination work to turn salt water into fresh water?