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As I said in another question I am just a physics enthusiast so I am sorry for my very poor knowledge. What is meant by models in physics? what is their function and why physicists imply them? Are the actual phenomena the exact reproduction in the real world of a physical model?

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A model in physics usually means a mathematical description of a system which is used to make testable predictions about its behavior. When writing about physics, some people prefer the term "model" over "theory" because most non-physicists don't know the difference between "theory" in the scientific sense and in its everyday usage.

All models are approximations to actual behavior, shown to be relevant and useful in prescribed sets of circumstances. "Adding more physics" to a model usually means accounting for more subtle physical effects by including them in the math, in the interests of improving the model's accuracy.

Sometimes, making a model more accurate a representation of the real world requires it to be fundamentally rewritten, as for example in the case of our understanding of gravity. Newton's original formulation was the first mathematical treatment of gravity and is perfectly useful today in predicting the movements of planets and satellites, but fails when called on to account for the behavior of extremely massive or extremely fast-moving things. Einstein's formulation of gravity encompasses the Newtonian treatment and also gives useful results in these special cases.

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  • $\begingroup$ This is a great answer, and I chortled a little when I realized that by this definition string theory isn't a model as it has not generated testable predictions - and indeed, it's right in there the name: theory. Until now I had naively assumed it was a model. (Note: I'm an experimentalist) $\endgroup$ – SabrinaChoice Sep 24 '18 at 1:54
  • $\begingroup$ your comments about string theory are spot-on. Have you read Smolin's book about it called "The Trouble With Physics"? $\endgroup$ – niels nielsen Sep 24 '18 at 3:29
  • $\begingroup$ Thanks for the answer. So, given that "All models are approximations to actual behaviour" it is correct to say that physical phenomena are never the exact counterpart of their correspondent models? In a nutshell, are physical phenomena the exact copy in nature of the model? $\endgroup$ – BGregerB Sep 24 '18 at 9:36
  • $\begingroup$ The deeper you go into the math, the more closely the models resemble reality i.e., the simpler the relationships get (fewer messy details)- but you can almost always find a set of circumstances where the model must fail. for example, any term with (distance)^2 in the denominator is destined to fail as distance -> zero. $\endgroup$ – niels nielsen Sep 24 '18 at 16:16
  • $\begingroup$ @nielsnielsen I haven't read that book, do you recommend it? I'm always looking for a good book! $\endgroup$ – SabrinaChoice Sep 25 '18 at 19:47

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