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2007-05-02 Models and Modeling"I remember my friend Johnny von Neumann used to say, with four parameters I can fit an elephant, and with five I can make him wiggle his trunk." Enrico Fermi, quoted in Dyson, F. (2004), A meeting with Enrico Fermi, Nature, 427, 297. "The trouble with most people in this business is that they think that because they have a bigger, faster computer, they can make more complicated models that are more realistic. "They should realize that because they cannot solve the equations and are stuck having to use the big machine, they must make the model simpler, if they want to UNDERSTAND the results." Dan McKenzie, ca. 1975 "Usually they start with one thing they don't understand: the Earth. "Then, they make a model, and they wind up with two things they don't understand: the Earth, AND the model!"
Philip England, ca. 1985
"Comprehensive complexity is no virtue in modelling, but, rather, an admission of failure." Ian N. James, p. 93, Introduction to circulating atmospheres, Cambridge University Press, Cambridge, 422 pp., 1994.
"Dynamic meteorologists have long been accustomed to simplifying their equations before putting them to use. Sometimes the simplifications are merely deletions of terms that appear to be inconsequential, but equally often they consist of omitting or significantly altering certain physical features or processes. Thus, effectively they replace the atmosphere by a different atmosphere, which Napier Shaw described in the early twentieth century, in his four-volume treatise Manual of Meteorology, as a fairy tale, but which today we would call a model." Edward N, Lorenz, in The Essence of Chaos, p. 86-87, University of Washington Press, Seattle, 1993.
"What it means to understand an equation ... was described by Dirac. He said: 'I understand what an equation means if I have a way of figuring out the characteristics of its solution without actually solving it.' So if we have a way of knowing what should happen in given circumstances without actually solving the equations, then we 'understand' the equations, as applied to these circumstances. A physical understanding is a completely unmathematical, imprecise, and inexact thing, but absolutely necessary for a physicist." in Chapter 2, page 2-1, of The Feynman Lectures on Physics, The Electromagnetic Field, Volume I, by Richard P. Feynman, Robert B. Leighton, and Matthew Sands, Addison-Wesley Publishing House, Reading, 19??.
(Substitute the word model for theory in the following)
"Another thing I must point out is that you cannot prove a vague theory wrong. ... if the process of computing the consequences is indefinite, then with a little skill any experimental results can be made to look like the expected consequences." in Chapter 7, p. 158, of The Character of Physical Law, by Richard Feynman, The M.I.T. Press, Cambridge, 1987. |
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