Physical Laws vs Physical Theories

[ShayanJ]

What's the difference between a physical Law and a physical theory?
thanks

 

[nasu]

One possible difference is that a theory may include several laws plus some models, assumptions, etc.

 

[f95toli]

The main difference is that the word "law" was mainly used for theories developed before the mid 19th century (there are exceptions, but the word is very rarely used in more modern physics). Another difference is that "laws" were often written as if they WERE (legal) laws (a good example is the laws of thermodynamics), back then people liked to talk about the "laws of nature" and the "laws of man"; the former having been decided by God and the latter by us.

 

[Drakkith]

There isn't much, if any difference other than different terminology. In effect they mean the same thing.

 

[Claude Bile]

The rule of thumb is that "laws" are theories that have been subject to an exceptional amount of rigorous testing; i.e. the law of conservation of energy, law of conservation of momentum; and have been found to be true in every instance. Mere theories have been subject to less stringent testing, relatively speaking.

The term "law" though is generally set by historical precedent rather than any quantitative assessment of the "correctness" of these theories. I tend to treat the word "law" as just part of the label that is attached to theory X, rather than give it any special significance.

Claude.

 

[alxm]

Not a very good rule of thumb, is it? Ohm's law is essentially the definition of electrical resistance, so it doesn't really say much, physically. Hooke's law is just a first-order approximation. Boyle's law and the Ideal Gas law are both theoretical idealizations that are only asymptotically true, so never true in practice. The laws of thermodynamics are about as absolute as anything. These things have very little in common.

I agree with f95toli's post. 'Law' just means something from the 19th century or earlier.

 

[Andy Resnick]

What's the difference between a physical Law and a physical theory?
thanks

not much- time and testing.

As others have mentioned, the difference between 'law' (Ohm's law) and 'theory' (the general theory of relativity) is often one of name, not substance.