1822
Difference Engine Plans · Charles Babbage
"What if a machine printed the tables for us without mistakes?" Babbage wondered while sketching brass gears long after midnight.
While revising astronomical tables for the Royal Astronomical Society, Babbage slammed his notebook shut and groaned, "If a machine turned the cranks for us, the errors would vanish." He rushed back to the workshops with sketches of interlocking gears, and apprentices poked at the drawings asking, "Can we really cut teeth this tiny?" Babbage laid out brass samples on the bench and coached them through each locking mechanism.
Months later at a Royal Society exhibition an astronomer squinted at the whirring prototype and asked, "Does this mean no more midnight corrections?" Babbage spun the handle and replied, "Pull the lever and the next column prints itself." An engineer beside him whispered, "I need this in my factory ledger," carrying the idea onward even before the full engine was complete.
The Difference Engine applied a mathematical insight: polynomials can be evaluated with addition alone when broken into finite differences. Inputs became the positions of metal rods, and outputs appeared on numbered wheels. Technology of the time could not produce a full-scale machine, yet the notion of delegating repetitive calculations heavily influenced later computer designs.