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Thread: Laws, principles and facts

  1. #1 Laws, principles and facts 
    Forum Freshman iantresman's Avatar
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    Although scientists once thought that radioactivity violated the law of conservation of energy, then new understanding of nuclear decay helped demonstrate that the law was fact.

    So why do we continue to call the Conservation of Energy a law, and not a fact. Why not a principle? Is there a difference?


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    ▼▼ dn ʎɐʍ sıɥʇ ▼▼ RedPanda's Avatar
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    Quote Originally Posted by iantresman View Post
    So why do we continue to call the Conservation of Energy a law, and not a fact. Why not a principle? Is there a difference?
    It is to convey how confident we are in it being true.

    There is a notional hierarchy: idea, hypothesis, theory, law.
    But, ultimately, it is just a name.
    If it was called Peter's Special Hat of Power then it would be no less accurate.


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    Forum Professor Daecon's Avatar
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    I thought laws were explanations of things, and facts were just statements of things?
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    ▼▼ dn ʎɐʍ sıɥʇ ▼▼ RedPanda's Avatar
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    Quote Originally Posted by Daecon View Post
    I thought laws were explanations of things, and facts were just statements of things?
    That could be one way of looking at it.

    But if we look at the definition of 'fact': "a thing that is known or proved to be true" we can see that both observations and explanations fit that definition.

    Semantics, semantics...
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  6. #5  
    exchemist
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    Quote Originally Posted by RedPanda View Post
    Quote Originally Posted by Daecon View Post
    I thought laws were explanations of things, and facts were just statements of things?
    That could be one way of looking at it.

    But if we look at the definition of 'fact': "a thing that is known or proved to be true" we can see that both observations and explanations fit that definition.

    Semantics, semantics...
    Yes, but it is notable that your list in the previous post included idea, hypothesis, theory and law, but not fact. It seems that in science we actually tend to avoid the term "fact". I think this is for a good reason. In my experience, all good scientists are modest about the claims of both their observations and the associated theories - just in case what they think they know, or have discovered, is later shown to be in error, condition-dependent, or incomplete.

    In science, all "truth" is provisional. This is implicitly acknowledged by just about every scientist - hence the instinctive avoidance of a term like "fact", which can carry inappropriate connotations of finality, and can seem complacent and dogmatic.
    Last edited by exchemist; December 19th, 2013 at 04:43 AM.
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    Brassica oleracea Strange's Avatar
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    I agree, the word "fact" is of doubtful value. We might all agree that gravity is a fact; in that gravity exist (cue long philosophical discussion about what "exists" means, whether that can be applied to gravity, etc.)

    But we might disagree about whether gravity is a force or not, what causes it, what is the best theory to explain it, whether Newton's Laws of gravity are wrong or just inaccurate, etc.

    Isn't "Law" usually reserved for a concise mathematical statement from a theory (e.g. Newtons' Laws of Motion (the modern version), his Law of Gravitation, Boyles' Law, etc.).
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    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by iantresman View Post
    Although scientists once thought that radioactivity violated the law of conservation of energy, then new understanding of nuclear decay helped demonstrate that the law was fact.

    So why do we continue to call the Conservation of Energy a law, and not a fact. Why not a principle? Is there a difference?
    Is it because it is more quantitative? (I am trying to think of an example of the Something Principle to compare it with...)

    Also, I'm not sure that conservation of energy is a "fact", except locally. It is not well defined in GR and so, for example, there is no problem with cosmologically red-shifted photons "losing" energy; that is just explained by them originating in a different frame of reference: the energy hasn't "gone" anywhere and isn't conserved.
    Without wishing to overstate my case, everything in the observable universe definitely has its origins in Northamptonshire -- Alan Moore
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    Quote Originally Posted by iantresman View Post
    Although scientists once thought that radioactivity violated the law of conservation of energy, then new understanding of nuclear decay helped demonstrate that the law was fact.So why do we continue to call the Conservation of Energy a law, and not a fact. Why not a principle? Is there a difference?
    Just a note on 'what scientists thought'.

    This expression pops up now and then. It pops up in my field. Put 10 scientists from a discipline in a room and there will be 8 explanations (if not 10) of some enigmatic phenomenon. It doesn't violate anything but is just not explainable with current knowledge. The media and popular culture are who label something as 'violating' or impossible....not scientists.
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  10. #9  
    exchemist
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    Quote Originally Posted by Strange View Post
    Quote Originally Posted by iantresman View Post
    Although scientists once thought that radioactivity violated the law of conservation of energy, then new understanding of nuclear decay helped demonstrate that the law was fact.

    So why do we continue to call the Conservation of Energy a law, and not a fact. Why not a principle? Is there a difference?
    Is it because it is more quantitative? (I am trying to think of an example of the Something Principle to compare it with...)

    Also, I'm not sure that conservation of energy is a "fact", except locally. It is not well defined in GR and so, for example, there is no problem with cosmologically red-shifted photons "losing" energy; that is just explained by them originating in a different frame of reference: the energy hasn't "gone" anywhere and isn't conserved.
    Not sure whether this is a real distinction. Try this: Le Chatelier's principle - Wikipedia, the free encyclopedia
    which suggests "Law" and "Principle may both be qualitative.

    And then of course the Uncertainty Principle is often expressed (semi-) quantitatively, as delta p . delta x > h/4 pi.

    But it's true the Pauli Exclusion Principle is qualitative, as is Bernouilli's.
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    This is a good definition of a scientific law:
    Scientific law - Wikipedia, the free encyclopedia
    Laws differ from scientific theories in that they do not posit a mechanism or explanation of phenomena: they are merely distillations of the results of repeated observation. As such, a law is limited in applicability to circumstances resembling those already observed, and may be found false when extrapolated.
    You wouldn't call a law a fact, because observations will be ongoing, and there could conceivably be a case found where it doesn't apply.
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  12. #11  
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    Quote Originally Posted by exchemist View Post
    Quote Originally Posted by Strange View Post
    Quote Originally Posted by iantresman View Post
    Although scientists once thought that radioactivity violated the law of conservation of energy, then new understanding of nuclear decay helped demonstrate that the law was fact.

    So why do we continue to call the Conservation of Energy a law, and not a fact. Why not a principle? Is there a difference?
    Is it because it is more quantitative? (I am trying to think of an example of the Something Principle to compare it with...)

    Also, I'm not sure that conservation of energy is a "fact", except locally. It is not well defined in GR and so, for example, there is no problem with cosmologically red-shifted photons "losing" energy; that is just explained by them originating in a different frame of reference: the energy hasn't "gone" anywhere and isn't conserved.
    Not sure whether this is a real distinction. Try this: Le Chatelier's principle - Wikipedia, the free encyclopedia
    which suggests "Law" and "Principle may both be qualitative.

    And then of course the Uncertainty Principle is often expressed (semi-) quantitatively, as delta p . delta x > h/4 pi.

    But it's true the Pauli Exclusion Principle is qualitative, as is Bernouilli's.
    Oh, and then we have "rules". For example, the Selection Rules for electronic transitions - which are often broken. Whereas Flemings Left and Right Hand Rules in electromagnetism are not.

    I don't think science is all that tidy, when it comes to such things.
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    Lots of debate over the laws of thermodynamics. Quantum theory has more or less relegated the law on entropy to the dust bin labelled 'Newton'. Leonard Susskind has an interesting lecture on You Tube on this subject.
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    Quote Originally Posted by exchemist View Post
    I don't think science is all that tidy, when it comes to such things.
    Science is tidy. It is English that is a mess.
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    In science, all "truth" is provisional. This is implicitly acknowledged by just about every scientist - hence the instinctive avoidance of a term like "fact", which can carry inappropriate connotations of finality, and can seem complacent and dogmatic.
    i really like this and is the main reason i'm a sceptic.
    Sometimes it is better not knowing than having an answer that may be wrong.
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    Quote Originally Posted by Fossilborealis View Post
    Lots of debate over the laws of thermodynamics. Quantum theory has more or less relegated the law on entropy to the dust bin labelled 'Newton'. Leonard Susskind has an interesting lecture on You Tube on this subject.
    Hi Fossilborealis. Have you got a link for that which I can have a look at over Xmas? Much obliged in advance. :-))
    Quidquid latine dictum, altum videtur
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    Hi,I've spent dozens of hours following ( or trying to) Susskind's Stanford lectures on Quantum theory. He puts a quantum spin (excuse the pun) on traditional physics. You can get a bit of his flavour on entropy and Time in this presentation of his. I will sometimes watch one of these videos and click on another, etc.

    The only caveat is to avoid some links that use the word quantum but are really spiritualists, etc. trying to prove whatever.

    . http://m.youtube.com/watch?v=jhnKBKZvb_U
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  18. #17  
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    Quote Originally Posted by Fossilborealis View Post
    Hi,I've spent dozens of hours following ( or trying to) Susskind's Stanford lectures on Quantum theory. He puts a quantum spin (excuse the pun) on traditional physics. You can get a bit of his flavour on entropy and Time in this presentation of his. I will sometimes watch one of these videos and click on another, etc.

    The only caveat is to avoid some links that use the word quantum but are really spiritualists, etc. trying to prove whatever.

    . http://m.youtube.com/watch?v=jhnKBKZvb_U
    Ta muchly :-))
    Quidquid latine dictum, altum videtur
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