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Old Aug 31st 2017, 05:04 AM   #1
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Physics is not about proving things

In a recent post < expanding space > Pmb made the statement:
physics is not about proving things
Which I thought deserved a bit more attention than just a passing glance.

At first look I thought this seemed wrong,
but thinking about it more I realised how much it points to the core of Physics.
Possibly we should say that Physics is about disproving things.

Physicists use flights of imagination to construct workable models of "reality"
as long as those models match observation, they are accepted
however Physicists are continually probing at the edges where these models might start to get a bit iffy
And when they find the model no longer exactly matches their observations, they dream up a new model.

However it is always a model...
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Old Aug 31st 2017, 06:31 AM   #2
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Yes, only in mathematics can one prove whether a conjecture is true or false. In the sciences we can only look for examples that show a conjecture is false, and thus perhaps disprove it. If scientists can't find compelling examples that disprove the idea, then we call the conjecture a theory. (Sometimes the term "theory" is confused with "conjecture," but they really are different things.)
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Old Aug 31st 2017, 06:57 AM   #3
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I highly recommend watching a video that a good friend of mine did for me.

http://www.newenglandphysics.org/com...an_Guth_04.mp4

In fact they're all worth watching. See: Common Misconceptions
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Old Aug 31st 2017, 11:07 AM   #4
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Yes indeed, PMB is absolutely right.
Physics and Science more generally is not about 'proof'
Proof lies in the provinces of Mathematics and Logic.

This is because proving something means showing that that something is consistent with a given set of premises, axioms, notions or whatever you wish to call them.

Nothing more.

No proof is ever offered for those axioms; you have to take them as absolute given.
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Old Aug 31st 2017, 11:40 AM   #5
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Originally Posted by ChipB View Post
Yes, only in mathematics can one prove whether a conjecture is true or false. In the sciences we can only look for examples that show a conjecture is false, and thus perhaps disprove it. If scientists can't find compelling examples that disprove the idea, then we call the conjecture a theory. (Sometimes the term "theory" is confused with "conjecture," but they really are different things.)
There is a relationship between proofs in math and proofs in physics. Each starts with axioms and certain undefined things. An example of somethings undefined in math are a point and a set. The postulates of natural numbers are peano's postulates/axioms

See: https://en.wikipedia.org/wiki/Peano_axioms

Euclidean geometry is based on Euclid's postulates: Postulate -- from Wolfram MathWorld

I studied logic for some time and came to understand that all arguments are based on premises and eventually it boils down to a postulate somewhere.
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Old Sep 8th 2017, 04:57 AM   #6
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No scientific theory has ever been proven right. But we have a large number which have not yet been proven wrong.
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Old Sep 13th 2017, 06:43 PM   #7
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I think the following article is something which should be made a sticky somewhere.

What is science? by the Panel on Public Affairs (POPA) of the American Physical Society, Am. J. Phys., 67(8), Aug (1999)

What is science?

The following statement was originally drafted by the Panel on Public Affairs (POPA)! of the American Physical Society, in an attempt to meet the perceived need for a very short statement that would differentiate science from pseudoscience. This statement has been endorsed as a proposal to
other scientific societies by the Council of the American Physical Society, and was endorsed by the Executive Board of the American Association of Physics Teachers at its meeting in Atlanta, 20 March 1999.

Science is the systematic enterprise of gathering knowledge about the world and organizing and condensing that knowledge into testable laws and theories.

The success and credibility of science is anchored in
the willingness of scientists to:

(1) expose their ideas and results to independent testing and replication by other scientists; this requires the complete and open exchange of data, procedures and materials;

(2) abandon or modify accepted conclusions when confronted with more complete or reliable experimental evidence.

Adherence to these principles provides a mechanism for self-correction that is the foundation of the credibility of science.
Continuing on the subject of this thread; the reason it is held that science/physics is not about proving things is because science uses inductive, rather than deductive logic. Its usual to call an inference 'inductive' if it passes from the singular statements to general statements such as accounts of the results of observations or experiments. to universal statements, such as hypotheses or theories.

That said, one is not justified in inferring universal statements from singular ones (no matter how many white swans we see it doesn't mean all swans are white). What it does mean is that, although not strictly valid, we can obtain some degree of reliability or probability.

That applies to the postulates of science. Once we move beyond that we start to use deductive logic where we can say that we've logically deduced something to a certainty. Logical arguments always start with premises which are assumed to be true and from which conclusions are arrived and in that manner we can say that those conclusions are "true," i.e. true if the premises are true.

I'm afraid Guth left that part out. I want to see if he'll redo those videos for me with that in mind someday.
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