Jay Forrester, (1918 -), an American engineer regarded as a pioneer in the development of early digital computer equipment. He is the founder of "system dynamics," the use of computer simulations to analyze social systems and predict the implications based on different model simulations. In 1944, the U.S. Navy contracted Forrester and colleague Robert Everett to develop a universal flight trainer and aircraft simulator. The result was Whirlwind, the first real-time electronic digital computer. Whirlwind's technology utilized the phenomenon that when current flows through a core, the core becomes magnetized even when the current is removed. The introduction of this kind of memory makes computers smaller in size, faster to access data, and more powerful. These attributes made Whirlwind the direct forerunner of the modern computer. Forrester's system dynamics theories were featured in the Limits to Growth (1972) written by Donella H. Meadows and others. Using system dynamics theory to construct a global computer model called "World3," the book presented 12 scenarios that revealed different possible patterns—and environmental outcomes—of world development over two centuries from 1900 to 2100. The book became a bestseller with over 30 million copies sold in more than 30 translations.