JF Ptak Science Books Post 1545
I found this object in my paper-calculators box (moveable disk calculators made of paper, two going back to A. Kircher in the 1660’s)—I’m not sure why it was there as it is not paper, though it is an interesting calculator.
[Images are greatly expanded in click mode.]
I learned a big lesson from it. The “Small Target Bombing Probabilities” calculator was issued by the insufferably-little-known Applied Mathematics Panel of the National Defense Research Council (NDRC)1 in the early 1940’s during WWII.
Marked “Restricted”, it calculated the number of bombs that would successfully be delivered given (1) the number of bombs, (2) the “aiming error”, and (3) target size. It would then generate results for “(a) the expected number of hits for the indicated number of bombs”, (b-e) the probability of at least one hit to four hits.
What is surprising to me was the number of bombs that didn’t find their target. For example, a 70,000 square foot building bombed with 200 bombs had a 50% chance of landing within 1200’ of the target’s center, and one in 100—or 2 bombs of the 200—will find their mark. I don’t think that I’ve ever seen figures like this before, and I’m surprised at the 1% hit rate.
1. The establishment of the NDRC was announced so: “It is announced by Science Service that the following committee has been appointed in the United States to correlate "scientific research on the mechanisms and devices of warfare": -- Nature 146, 191-191 (10 August 1940).
“Members included: Dr. Vannevar Bush (chairman), president of the Carnegie Institution of Washington, formerly dean of the faculty of engineering at the Massachusetts Institute of Technology; Prof. Richard C. Tolman (vice-chairman), dean of the graduate school and professor of physical chemistry and mathematical physics at the California Institute of Technology; . Dr. Irvin Stewart (secretary), formerly Federal Commissioner for Communications and chairman of the Committee on Scientific Aids to Learning; Rear Admiral Harold G. Bowen, director of the Naval Research Laboratory, Anacostia, D.C.; Conwiy P. Coe, U.S. Commissioner of Patents; Dr. Karl T. Compton, president of the Massachusetts Institute of Technology, formerly professor of physics at Princeton University; Dr. James B. Conant, president, formerly professor of organic chemistry, Harvard University; Dr. Frank B. Jewett, president of the Bell Telephone Laboratories; Brigadier General G. V. Strong, assistant chief of staff, U.S.”