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Re: [Phys-l] nature of science



Manoranjitham Joshua asked:

1. What is the basic difference between a theory and a law in science?

The differences, if any, are minor and not worth worrying about. Scientists use
words like rule, law, equation, identity, principle, formula, algorithm, etc.
almost interchangeably, to describe the process for making predictions
(although there are slight variations in connotations).

2. When Newton first developed it, would we classify Newton’s Law of Gravitation as a theory or a law?

Why should we classify it at all?

Words are used to communicate; what is the point you are trying to
communicate? Isn't there an easier way of communicating it?

3. What is the role of hypothesis in

a) introductory physics courses

b) physics major’s courses

c) graduate physics courses

The word "hypothesis" has two distinct meanings:

* In the context of hypothesis testing, a hypothesis is a tentative explanation. We have a set of hypotheses, each of which is consistent with the facts so far, but we expect some of the hypotheses to be ruled out as additional facts come in. For details, see
http://www.av8n.com/physics/hypothesis.htm#sec-testing

* In the context of a hypothetical scenario, a hypothesis is a statement that has been “factored out” of a group of statements. Such a factorization often makes a discussion much clearer and more concise. For details, see
http://www.av8n.com/physics/hypothesis.htm#sec-scen

Also, as it says at
http://www.av8n.com/physics/scientific-methods.htm#main-hypothesis

The lattermost stages of any
systematic investigation can often be formalized in terms of
hypothesis testing. More generally, though, science involves a
multi-stage iterative process, where the results of early stages are
used to guide the later stages. The early stages are exploratory, and
are not well described in terms of hypothesis testing, unless we abuse
the terminology by including ultra-vague hypotheses such as ``I
hypothesize that if we explore the jungle we might find something
interesting''. It is common for people who don't understand science
to radically overemphasize the hypothesis-testing model, and to
underestimate the number of iterative stages required before
nontrivial hypotheses can even be formulated.