Frustrated by the problems he'd had in trying to build a machine to solve equations, he'd gone on a long drive. He wanted to solve differential equations to work on questions about the physics of crystals, the forces that govern atoms, and the design of electrical circuits. The feud over credit for the computer's invention began after a five-day trip that the late John Mauchly, a physics professor at Ursinus College near Philadelphia, made to see Atanasoff in June 1941. But Mauchly said later that he had quickly realized Atanasoff's machine was a dud. According to Eckert, he and Mauchly first discussed trying to do complicated computations with mechanical components.
Wires are cheaper than shafts and ball bearings and gears and things.
He believed he could analyze the weather and find mathematical patterns that could be used for forecasting. At Penn, his computer-building project drew the financial support of the Army, which needed complex calculations to produce the firing tables that are used to predict the paths of artillery shells. The machine that Mauchly and Eckert finally built with military money became operational in 1946. It was 100 feet long, used 17,468 vacuum tubes, had 6,000 switches, and weighed 30 tons. It could add 5,000 numbers is a second.