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To: edsheppa

Not true. Suppose that you want to calculate , say, the co-efficient of expansion of a metal as a function of temperature. You could perform an experiment and vary the the temprature systematically and come up with an answer. OTOH, if someone had reliable observations, you could simply fit your model to these observations. If you knew what you were doing, and knew the limits on the accuracy of observations, given a temperature, you could predict the expansion, and state reliable upper and lower bounds.

It someone gave you a temperature outside the range of the observations however, you would be on shaking ground. The metal might melt at a very high temperature, for instance.

Astonomers have *nothing* but historical data yet they can make very accurate predictions about planetary ephemeris, with reliable limits on the expected errors. Sixty years ago astronomers were able to predict (to within a few blocks) which streets on Manhattan would see a total eclipse and on which it would be partial.


26 posted on 02/28/2007 10:36:30 AM PST by Lonesome in Massachussets (When I search out the massed wheeling circles of the stars, my feet no longer touch the earth)
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To: Lonesome in Massachussets

You missed the point. I didn't say that models inferred from historical data are necessarily unreliable. I said it is unsurprising, and no indication of reliability, that a model fits data from which it was inferred. One should infer reliability only if the validating predictions are independent of the model.


28 posted on 02/28/2007 12:04:04 PM PST by edsheppa
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