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Before computers had the kind of processing power they do now, engineers would build analog circuits to solve differential equations. A modern-day quick link:

• yablak 10y ago
  (nowadays it's usually the other way around, of course ;)
• versteegen 10y ago
  Before electronic computers existed, engineers built mechanical analog devices called differential analysers [1] to compute derivatives and integrals, invented in 1876 by brothers James Thomson and Lord Kelvin. Famously, cheap differential analysers were built out of Meccano starting in 1934 [2]. After scientists gained access to electronic computers, these old analysers were repeatedly handed down through lower-budget institutions, schools and eventually museums. [1] https://en.wikipedia.org/wiki/Differential_analyser https://en.wikipedia.org/wiki/Differential_analyser [2] http://amg.nzfmm.co.nz/differential_analyser_explained.html http://amg.nzfmm.co.nz/differential_analyser_explained.html
  • Sharlin 10y ago
    This old US Navy training film on mechanical fire control calculators (called "computers" back then, used to calculate firing solutions on warships) is pretty fascinating: https://www.youtube.com/watch?v=s1i-dnAH9Y4 https://www.youtube.com/watch?v=s1i-dnAH9Y4