Abstract: How do we know the stuff we know? In physics and engineering, a lot of our knowledge comes from calculations. And when these calculations become difficult, we need tools to perform them. Fifty years ago, mechanical calculators (pictured left) were the tool of choice, and they allowed us to quickly add, subtract, multiply, and divide numbers. They are reliable, make a heck of a noise, weigh 20 pounds, and they just work. They solved many problems before the advent of the computer, contributing a huge amount to what we know today. But as science ...
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