What is a law?

[NeonBlack]

Seems like a stupid question, but I was wondering why there is no precise definition for a 'law.' Some examples of different types of 'laws':

 

1) Ohm's law, Hookes law: These are based on experiment and are true only in certain cases, for certain materials and in certain ranges. No real basis in first principles; only an effective description of what occurs.

 

2) Coulomb's law, Newton's 3rd law: Also based on experiment, but always true and seen as something fundamental.

 

3) Gauss's law: Always true, but can be derived from something fundamental (Coulomb's law or Newton's G law). Maybe we could say that Kepler's laws were originally type 1, but became type 3 after Newton.

 

4) Newton's 2nd law: Again always true, but basically just a definition.

 

Why is the word law applied to so many different things? My only guess is for historical reasons. Left over from a time when physics was not as rigorous as it was today. This makes sense to me as I can't think of any physical "laws" which have been discovered in the past century.

[Edtharan]

It is because of the way that science works.

 

First comes Observation: This is when some regular phenomina is seen.

 

Next is Hypothisys: This is when people (scientists) start trying to explain what is going on in the observed regular phenomina.

 

Then there is Theory: this is when the hypothisis are tested and one or more are shown to describe the phenomina and make testable predictions about them. They give a working model for the phenomina and related phenomina.

 

This is where most of our understanding about the Universe is. Theory doesn't mean "a good/educated geuess" as it does in every day speach (and this is why a lot of people try to us ethe non technical term as an argument against something described by the technical term).

 

Finally we come to Law: This is just a collective noun (group name) for all the Theories that have no compeating theories and have lasted through years and years (there is not specific time but it is usually many decades) of testing without needing revision.

 

This is why there are no recent "Laws" as they take many decades (sometimes hunderds of years) to undergo the thorough testing needed.

 

All "Laws", however are still theories in that if someone produces an observation (and undergoes all of what I just described above) that contradict the "Law" then the Law will then have to be revised.

 

All those hurdels that an observation has to undergo to be accepted is not because scientist are opposed to change, or worried about being prooved wrong. It is a quality control mechanism that filters out descritions of the Universe that don't actually describe what the Universe is like. A scientist can becomes famous simple because their idea was proved wrong as in the case of Michelson and Morely and the Ether (they believed that the Ether existed and performed an experiment to attempt to prove it's existance, but the experiment was a complete failure in that it conclusivle proved that the Ether dind't actually exist - and that is what they are famous for, proving that their theory was wrong ).

[swansont]

Finally we come to Law: This is just a collective noun (group name) for all the Theories that have no compeating theories and have lasted through years and years (there is not specific time but it is usually many decades) of testing without needing revision.

 

This is why there are no recent "Laws" as they take many decades (sometimes hunderds of years) to undergo the thorough testing needed.

 

All "Laws", however are still theories in that if someone produces an observation (and undergoes all of what I just described above) that contradict the "Law" then the Law will then have to be revised.

 

 

A scientific law is a subset of a theory. It's just a simple relationship that's been observed to hold under some set of circumstances. There's a very strong correlation between a law and an equation. Laws can and do exist without the theories that explain why the laws are valid, e.g. gravitation.

[thedarkshade]

I always thought a law is a confirmed scientific theory that refers to phenomenas that happen all the time!

[swansont]

I always thought a law is a confirmed scientific theory that refers to phenomenas that happen all the time!

 

No, it's not. Newton's laws are a subset of the theory of motion, there are various laws that are derived from or otherwise statements of Maxwell's equations, and other independent ones, that are a subset of electromagnetic theory. Still more laws that are part of thermodynamics.

 

A theory can encompass a law or laws, but also includes an explanation of why things occur and the body of evidence that supports it. Theory is the pinnacle.

[thedarkshade]

A theory can encompass a law or laws, but also includes an explanation of why things occur and the body of evidence that supports it. Theory is the pinnacle.

Right, fair enough! But taken generally you know, the word 'theory' is often understood (probably misunderstood) as an attempt to explain something, but with a dose of doubt. Like "theoretically speaking yeah, but in practice there might be some complications... and stuff like this! So by this understanding, a certainty (a law) is being a part of uncertainty (the theory) ! Unfortunately it is like this by the general understanding of the word theory!

 

general understanding = the understanding of non-scientific average-intelligent random people

[Bignose]

Right, fair enough! But taken generally you know, the word 'theory' is often understood (probably misunderstood) as an attempt to explain something, but with a dose of doubt. Like "theoretically speaking yeah, but in practice there might be some complications... and stuff like this! So by this understanding, a certainty (a law) is being a part of uncertainty (the theory) ! Unfortunately it is like this by the general understanding of the word theory!

 

general understanding = the understanding of non-scientific average-intelligent random people

 

It's an unfortunate happenstance that the common word and the scientific word have in many regards opposite meanings. But, that's the way it is. Unless we get all the scientists in the world together and say: ok, from now on we're not going to call theories 'theories' anymore, we're going to call them 'boogers' or 'peacocks' or 'super-theories' or 'dresses' or 'clocks' or 'schplitzes' or whatever.

 

The word is going to stick, just like all the other unfortunate words stick. The best thing to do is to educate people as much as possible what the word means in a scientific sense.

[swansont]

Right, fair enough! But taken generally you know, the word 'theory' is often understood (probably misunderstood) as an attempt to explain something, but with a dose of doubt. Like "theoretically speaking yeah, but in practice there might be some complications... and stuff like this! So by this understanding, a certainty (a law) is being a part of uncertainty (the theory) ! Unfortunately it is like this by the general understanding of the word theory!

 

general understanding = the understanding of non-scientific average-intelligent random people

 

But this is a science board and we know what is meant by theory when discussing science.

[timo]

But this is a science board and we know what is meant by theory when discussing science.

Not really, especially not when you think this understanding was what you supposedly mean with the term. Examples:

- People presenting their theory of magnetism/everything being made up of pure energy/discrete time/... .

- The famous Big Bang Theory that I always hear about in forums.

- I'd spontaneously (never really thought about the issue, though) use the term "theory" as more or less interchangable with "framework". So I surely do not have a problem with String Theory being called a theory (it's even part of the name of that field, after all). It's surely a framework, probably quite a large one, but surely nothing that has been well-tested experimentally. I even have no problem calling Newtonian Mechanics a theory, even though we know that applying it can be wrong for some problems. Or in other words: I would not attribute too much judgement about the value or applicability of an idea to the term "theory" (but certainly neither the negative "just a theory" evaluation). I'd see it as a value about range/size and internal consistency, at best.

 

On topic:

- I agree with Swansont's statement that "a scientific law is a subset of a theory" - that would have been my first thought, too.

- Thinking about it a bit further, there seems to be no reason why a law must be part of an existing theory. It seems to make perfect sense that you make observations that seem to hold true but that no existing theory (meant in the sense of "framework") explains why they should be.

- Just as with "theory", I wouldn't read the term "law" as inherently being a judgement.

 

Bottom line: I do not see a clear scientific definition of the term "law", especially not in an evaluating sense. Given that scientists are supposed to know when and to roughly what extent a statement applies, I also see little need for a clear definition.

[waitforufo]

I believe there was a time in science when a law was defined as an exceptionless regularity. So Ohm's Law, voltage equals current times resistance (V=IR), is always true without exception. One might argue that this "law" is true even if resistance changes with current or voltage. In such a system, resistance could be described as non-linear. Modern science has however found that concepts once considered to be exceptionless regularities, such as the law of conservation of mass/matter, actually have exceptions. Due to this, in my opinion, the term "theory" is favored over "law" in modern science.

 

Perhaps a better question would be "what is the definition of 'theory'." This word has a number of definitions in science depending on context. Unfortunately in popular culture the word "theory" seems to mean an idea not yet proven. This popular culture definition is always emphasized by pseudo science groups such as those promoting life origins through "intelligent design." Using this popular culture definition of 'theory' puts in their minds, "intelligent design" on the same footing as "natural selection" since neither can be proven to be an exceptionless regularity.

[fredrik]

Seems like a stupid question, but I was wondering why there is no precise definition for a 'law.'

 

It wasn't a stupid question at all IMO, probably one of the better ones.

 

While it may not be so arousing to actually discuss "definition of words", it sure would be important to define terms physically that are used in reasoning.

 

I don't know what the official comittee of definitions say, but these are the reflections I personally make on this:

 

When I think of "law", I think of it like a "tool of reasoning". You have a set of initial conditions and a set of laws. Somehow these laws typically allows you to make predictions, where the "premise" is the initial conditions and your "rules of reasoning" are the laws, and at least classically the laws are fixed and eternal.

 

But does that make sense? In the spirit of modern physics and Niels Bohr's epistemological perspective I would always want to ask, what to we KNOW about these laws? Ie. Laws or not, we are incomplete creatures and whatever the laws "are", the question we can not avoid is how does the process of gaining information about these "laws", and thus making them part of our knowledge look like?

 

This type of reasoning, at least leads me personally to suggest that there is from a deeper philosophical science perspetice, no clear cut distinction between initial condition and law! Because the law is probably more like a condensation of acquired history, from which we have extracted information about common, repeating and seemingly constant patterns in nature. This we use together with the latest information we have (initial conditions) to GUESS what will happen next.

 

This guess can be seen as a induction, and it's accuracy depends not only on the accuracy on the initial conditions, but also on the accuract of the rules of induction themselves.

 

I think ultimately even the percepted laws may evolve. Alternativrely you could choose to say that, well then the laws was "wrong". But the question is what is more constructive? To look for something that may not exist, or face our limitation and try to optimise our chances in this game of life.

 

So I like to loosely associate laws with rules of reasoning that are acquired. And these acquired laws are not eternal, they are most probably themselves dynamical and subject to ongoing distortion. I think the ideal that once we find the laws, they are eternal, sounds like a idealisation. And it is not a plausible one. The dynamical evolution of laws is to, provides a much more consistent picture.

 

/Fredrik

[Klaynos]

I believe there was a time in science when a law was defined as an exceptionless regularity. So Ohm's Law, voltage equals current times resistance (V=IR), is always true without exception.

 

It's only true for Ohmic resistors.... Sorry...

[swansont]

I believe there was a time in science when a law was defined as an exceptionless regularity.

 

Ohm's law and Hooke's law are two examples recognized in the OP as not applying in all cases.

[waitforufo]

It's only true for Ohmic resistors.... Sorry...

 

Klaynos,

I thought I pointed that out by saying...

 

"One might argue that this "law" is true even if resistance changes with current or voltage. In such a system, resistance could be described as non-linear."

 

 

Swansont,

OP?

[swansont]

 

Swansont,

OP?

 

Original Post

[xptoast]

Please make note that "Law" is only a highly able set of reasoning. Its not perfect. For instance in grammar you have the i before e law. However "their" law is a bit wrong as you just have seen. Science is the same way. A law is used often. Such as Newtons Laws of gravity. They held up pretty well but are not perfect. They are just very very accurate sets of logic but not perfect logic. Perfect logic is flawed anyhow. Such as pure evil cannot be pure as the intentions of evil is to gain something in which you could not with good but still has the intention of the good end result such as pleasure.

[xptoast]

Theory...This is from dictionary.com

 

 

the·o·ry /ˈθiəri, ˈθɪəri/ Pronunciation Key - Show Spelled Pronunciation[thee-uh-ree, theer-ee] Pronunciation Key - Show IPA Pronunciation

–noun, plural -ries.

1. a coherent group of general propositions used as principles of explanation for a class of phenomena: Einstein's theory of relativity.

2. a proposed explanation whose status is still conjectural, in contrast to well-established propositions that are regarded as reporting matters of actual fact.

3. Mathematics. a body of principles, theorems, or the like, belonging to one subject: number theory.

4. the branch of a science or art that deals with its principles or methods, as distinguished from its practice: music theory.

5. a particular conception or view of something to be done or of the method of doing it; a system of rules or principles.

6. contemplation or speculation.

7. guess or conjecture.

 

That looks like guess to me. Sorry it just bugs me when people wish to meddle with their own language and meanings. Even laws of physics are not perfect. Such as gravity formula. Its not perfect but sure as heck got us to the moon and back. Science is not perfect. Its just mostly right. Not all right.

[swansont]

Theory...This is from dictionary.com

 

 

the·o·ry /ˈθiəri, ˈθɪəri/ Pronunciation Key - Show Spelled Pronunciation[thee-uh-ree, theer-ee] Pronunciation Key - Show IPA Pronunciation

–noun, plural -ries.

1. a coherent group of general propositions used as principles of explanation for a class of phenomena: Einstein's theory of relativity.

2. a proposed explanation whose status is still conjectural, in contrast to well-established propositions that are regarded as reporting matters of actual fact.

3. Mathematics. a body of principles, theorems, or the like, belonging to one subject: number theory.

4. the branch of a science or art that deals with its principles or methods, as distinguished from its practice: music theory.

5. a particular conception or view of something to be done or of the method of doing it; a system of rules or principles.

6. contemplation or speculation.

7. guess or conjecture.

 

That looks like guess to me. Sorry it just bugs me when people wish to meddle with their own language and meanings. Even laws of physics are not perfect. Such as gravity formula. Its not perfect but sure as heck got us to the moon and back. Science is not perfect. Its just mostly right. Not all right.

 

 

dictionary.com is not a technical resource, but what's wrong with 1? That's referring to the scientific use, and does not mean "guess."

 

Calling something a law in science does not mean that it's perfect (something that we are discussing here, just that it's been observed to hold, and there's a relatively simple formula for it

 

(mod note: this and previous post copied over from FTL/tachyon thread)

[xptoast]

dictionary.com is not a technical resource, but what's wrong with 1? That's referring to the scientific use, and does not mean "guess."

 

Calling something a law in science does not mean that it's perfect (something that we are discussing here, just that it's been observed to hold, and there's a relatively simple formula for it

 

(mod note: this and previous post copied over from FTL/tachyon thread)

 

Dictionary.com uses the standard dictionaries. Please look at their website to see what I mean. Its a credible source.

[D H]

Nobody has claimed that Dictionary.dom is a non-credible source. The problem is that it is a lay source. Scientists do not use the term "theory" in the lay sense of "6. contemplation or speculation" or "7. guess or conjecture". They use the words conjecture, hypothesis, or guess instead. Definition #1 describes scientific theories such as relativity and evolution: A very detailed and well-confirmed explanation of the observed world. Unfortunately, even scientists are prone to abuse of terminology, and hence things like "string theory" (definition 2). Utter abuse of terminology is something scientists leave to the non-scientific world. As this is a scientific forum, we should avoid using definitions 6 and 7 at all costs. This is particular so since we have perfectly adequate words for such things, such as the four alternative words listed in definitions 6 and 7.