Example #3: Issac Newton and the Speed of Sound

In the Principia Issac Newton presented examples of his mechanical system of the world. These examples acted as much to show the power of his system as they did to illustrate its uses. Through many editions of the text Newton worked with his editor to revise applications and maintain conformance with experimental findings. One body of experimental findings involved the speed of sound in air.
Newton understood very well the mechanical principles involved in sound propagation, but the specific details eluded him because of an incomplete understanding of heat transfer in a fast process. As a result Newton used the value of isothermal compressibility of air rather than isentropic compressibility, which left his estimates of sound speed wrong by 20% or so. However, to maintain the illusion that all was right with his mechanical system he engaged in a pattern of fudging the theory with ingenious, but unfounded and indefensible "corrections" to his calculations. Newton always knew what value for the speed of sound he needed to reproduce, which allowed him to fudge exact correction factors. This was circular reasoning, perhaps even outright dishonesty. Through the circular reasoning Newton managed to justify mechanical corrections that were non-existent. A well made circular argument can prove nearly anything.