What is the difference in theory and law

[MathJakob]

I googled this question first but there seemed to be a few different answers and I'm not sure which is correct. So take for example the theory of general relativity and the first law of thermodynamics, both are true, but why is one a theory and one a law?

Why was Einsteins theory called theory of general relativity and not law of general relativity? Also what about Heinsenberg's uncertainty principle, is this still a theory or law or just a mathematical statement?

Can you tell me when someone discovers something about the universe, what determines if it's classed as a theory or a law.

Thanks.

 

[Astronuc]

A physical law or scientific law, according to the Oxford English dictionary, "is a theoretical principle deduced from particular facts, applicable to a defined group or class of phenomena, and expressible by the statement that a particular phenomenon always occurs if certain conditions be present."[1] Physical laws are typically conclusions based on repeated scientific experiments and observations over many years and which have become accepted universally within the scientific community.

http://en.wikipedia.org/wiki/Physical_law
[1] "Law of Nature". Oxford English Dictionary (3rd ed.). Oxford University Press. September 2005.

A scientific theory is a well-substantiated explanation of some aspect of the natural world, based on knowledge that has been repeatedly confirmed through observation and experimentation.[1][2] Scientists create scientific theories from hypotheses that have been corroborated through the scientific method, then gather evidence to test their accuracy.

http://en.wikipedia.org/wiki/Scientific_theory
[1] http://www.nap.edu/openbook.php?record_id=6024&page=2
[2] AAAS Evolution Resources

Theory: In science, a well-substantiated explanation of some aspect of the natural world that can incorporate facts, laws, inferences, and tested hypotheses.

http://www.nap.edu/openbook.php?record_id=6024&page=2

A theory seems more general than a law and broader in scope.

 

[1MileCrash]

A theory offers an explanation behind some phenomenon. If the theory is working, we can manipulate that phenomenon. Germ theory of disease allows us to combat disease based on our understanding.

A law is a statement, but offers no explanation. Newton's laws of motion, for example, are statements.

 

[Evo]

I googled this question first but there seemed to be a few different answers and I'm not sure which is correct. So take for example the theory of general relativity and the first law of thermodynamics, both are true, but why is one a theory and one a law?

Why was Einsteins theory called theory of general relativity and not law of general relativity? Also what about Heinsenberg's uncertainty principle, is this still a theory or law or just a mathematical statement?

Can you tell me when someone discovers something about the universe, what determines if it's classed as a theory or a law.

Thanks.

This doesn't answer your *specific* questions, but it does explain the differences between hypothesis, theory and law.

https://www.physicsforums.com/showpost.php?p=4567304&postcount=4

For those too lazy to click on the link.

Since this is a science forum, the scientific definition would apply

Theory

Definitions from scientific organizations
The United States National Academy of Sciences defines scientific theories as follows:
The formal scientific definition of theory is quite different from the everyday meaning of the word. It refers to a comprehensive explanation of some aspect of nature that is supported by a vast body of evidence. Many scientific theories are so well established that no new evidence is likely to alter them substantially. For example, no new evidence will demonstrate that the Earth does not orbit around the sun (heliocentric theory), or that living things are not made of cells (cell theory), that matter is not composed of atoms, or that the surface of the Earth is not divided into solid plates that have moved over geological timescales (the theory of plate tectonics)...One of the most useful properties of scientific theories is that they can be used to make predictions about natural events or phenomena that have not yet been observed.[16]

http://en.wikipedia.org/wiki/Theory#Definitions_from_scientific_organizations

Hypothesis

People refer to a trial solution to a problem as a hypothesis, often called an "educated guess"[8][9] because it provides a suggested solution based on the evidence. Some scientists reject the term "educated guess" as incorrect, however.[10] Experimenters may test and reject several hypotheses before solving the problem.
According to Schick and Vaughn,[11] researchers weighing up alternative hypotheses may take into consideration:
Testability (compare falsifiability as discussed above)
Parsimony (as in the application of "Occam's razor", discouraging the postulation of excessive numbers of entities)
Scope – the apparent application of the hypothesis to multiple cases of phenomena
Fruitfulness – the prospect that a hypothesis may explain further phenomena in the future
Conservatism – the degree of "fit" with existing recognized knowledge-systems.

http://en.wikipedia.org/wiki/Hypothesis#Scientific_hypothesis

Law

While scientific theories and laws are both based on hypotheses, a scientific theory is an explanation of the observed phenomenon, while a scientific law is a description of an observed phenomenon

Both scientific laws and theories are supported by a large body of empirical data; both help unify a particular field of scientific study; and both are widely accepted by the vast majority of scientists within a discipline.

 

[SteamKing]

Theories come and go; one hopes that laws are more permanent.

 

[Curious3141]

Theories come and go; one hopes that laws are more permanent.

This is a little misleading. Newton's "laws" of motion (at least the second law, depending on how it's formulated) and "universal law" of gravitation have both been superseded by Einstein's "theories" (special and general relativity, respectively).

Newton's "laws" continue to be excellent approximations that hold to a very high degree of accuracy in commonplace experience. But Einstein's "theories" are considered (currently, anyway) to be exact descriptions of the same phenomena.

To the lay person, a "law" seems more definite and immutable than a "theory". But this is not necessarily true in Science.

 

[D H]

What is the difference in theory and law?

If you can tweet it, it's a law. In many cases, another name for "law" is "equation." If you need to write a book about it, or a volume of books, it's a theory. Laws are short and pithy, and oftentimes don't mean much in and of themselves. A scientific theory is needed to explain how and when to use those scientific laws.

Some examples:

• F=ma: Law. Newton's Principia: Theory.
• V=IR: Law (an empirical law at that, one that fails when your resistors emit smoke). Electromagnetism: Theory.
• j^*=εσT⁴: Law. Quantum mechanics and thermodynamics: Theory.

 

[Chronos]

Its just semantics. 'Laws' of nature are merely theories that are particularly well supported.

 

[1MileCrash]

Its just semantics. 'Laws' of nature are merely theories that are particularly well supported.

Hrrmm.. you make it sound like theories "become" laws, which is not true, they are different things.

 

[arildno]

Laws can remain practically unexplained, empirically-derived statistical regularities, such as Coulomb's law of friction.

The deeper explanatory principles behind friction cannot as yet be seen to be satisfactorily developed in such a way that Coulomb's law of friction falls deductively out as THE principal result in every case, even though one knows, of course, that Coulomb's law of friction must be regarded as the aggregate macroscopic effect of microscopic electromagnetic interactions.

But, even without this theory behind it, Coulomb's law is perfectly observable in its action.
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Newton's laws of motion in their totality, in contrast to the specific case like Coulomb's law, is of such a daring degree of generality that it must be regarded as a theory (and, a failed one as that)

 

[Pythagorean]

Theories consist of laws (and other things that put the laws in context)

 

[D H]

Newton's laws of motion in their totality, in contrast to the specific case like Coulomb's law, is of such a daring degree of generality that it must be regarded as a theory (and, a failed one as that)

Newtonian theory is not a failed theory. It remains a valid scientific theory, but now instead of being viewed as universally true theory it is a theory with a limited, non-universal domain. Physicists still teach and engineers still use Newtonian mechanics because it is extremely accurate in the realm in which it is applicable.

Failed scientific theories include concepts such as the caloric theory of heat. Even then, the term failed is a bit strong. A better term is superseded. After all, caloric theory had some remarkable successes (e.g., the Carnot cycle), and it was the dominant theory of heat for almost 100 years. Nobody teaches or uses caloric theory any more because it was superseded by thermodynamics, which has much greater utility and a much wider range of validity.

Why was Einsteins theory called theory of general relativity and not law of general relativity? Also what about Heinsenberg's uncertainty principle, is this still a theory or law or just a mathematical statement?

A scientific theory rather than a scientific law is the pinnacle of science. They represent a body of well-tested scientific knowledge and explain how to use that knowledge. F=ma doesn't mean much in and of itself, nor does σ_xσ_p≥ħ/2. Newton's laws doesn't mean much until backed up with the larger Newtonian mechanics (a scientific theory), just as Heisenberg's uncertainty principle doesn't mean much until backed up by the larger quantum theory.

So why aren't the Heisenberg uncertainty principle, the Pauli exclusion principle,the Dirac equation, the Schrödinger equation called "laws"? These concepts are named after the key developers of the second wave of quantum mechanics. They had just seen many of the supposedly universal laws of physics cast down to the status of equations with a limited domain of applicability, and now they were working to overthrow the old quantum mechanics that had just overthrown classical physics. Perhaps they thought calling their new concepts "laws" would have been a bit too arrogant. More importantly, the developers of that second wave of quantum mechanics were strongly influenced by the concepts of anti-realism and instrumentalism. Unlike earlier generations of physicists, Bohr, Heisenberg, Pauli, et al. very specifically were not trying to elucidate God's laws. They rejected that concept. The people behind the Copenhagen interpretation were merely trying to come up with a more concise and more accurate description of what could be observed physically.

 

[zoobyshoe]

Newton's theory was the theory of Universal Gravitation. He proposed the three laws as axioms upon which his long train of reasoning toward the existence of Universal Gravitation could be built. They have the same function the two postulates of SR have. They're basically stipulations upon which something else will be built. You agree to them or you don't. I'm not sure how the three laws, or the two postulates, could be reworked as a theory in and of themselves.

So, I think whether or not something is called a "law" depends on how well it functions as an axiom or postulate.

An axiom, or postulate, is a premise or starting point of reasoning. As classically conceived, an axiom is a premise so evident as to be accepted as true without controversy.[1] The word comes from the Greek ἀξίωμα (āxīoma) 'that which is thought worthy or fit' or 'that which commends itself as evident.'[2][3] As used in modern logic, an axiom is simply a premise or starting point for reasoning.[4] Axioms define and delimit the realm of analysis; the relative truth of an axiom is taken for granted within the particular domain of analysis, and serves as a starting point for deducing and inferring other relative truths. No explicit view regarding the absolute truth of axioms is ever taken in the context of modern mathematics, as such a thing is considered to be an irrelevant and impossible contradiction in terms.

-wiki

The actual chapter of Principia where Newton lays out the three laws is entitled "Axioms, or Laws of Motion." He put the word "axioms" first. All three words, "axiom," "law," "postulate," can probably be taken as synonyms.

 

[dipole]

Laws are empirical observations which can be taken as "facts" about nature. Conservation of energy and momentum, the laws of thermodynamics, Newton's Laws, Coulomb's Law and the Law of Gravitation etc...

They are all observed facts about nature (up to some degree of approximation) which theories, such as Thermodynamics and Classical Mechanics can be built up from. You can't really derive these laws from the theories without making some other kind of assumptions, which then just replace them as a new set of "laws".

 

[Pythagorean]

The actual chapter of Principia where Newton lays out the three laws is entitled "Axioms, or Laws of Motion." He put the word "axioms" first. All three words, "axiom," "law," "postulate," can probably be taken as synonyms.

Axioms are generally more fundamental. They are types of laws, but not all laws are axioms. Mostly just because law is such a diverse term that it's used more loosely, but axioms serve more as the core laws of a theory.

 

[zoobyshoe]

Axioms are generally more fundamental. They are types of laws, but not all laws are axioms. Mostly just because law is such a diverse term that it's used more loosely, but axioms serve more as the core laws of a theory.

Yeah. Despite the fact I just got done suggesting they could be taken as synonyms I don't actually believe there are any true synonyms. When it comes down to a specific context there is usually one choice that is le mot juste.

http://www.thefreedictionary.com/mot+juste

 

[Pythagorean]

I like how the pronunciation of that sounds like "most used".