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Do Laws Affect Constants?

  1. Mar 31, 2005 #1
    Do the physical laws make up the constants?
     
  2. jcsd
  3. Mar 31, 2005 #2

    turbo

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    We can define something as a law when we perceive that a strict relationship exists. For example: the intensity of a light source diminishes in relation to the inverse square of the distance between the emitter and the detector. The things that we consider physical laws are generally based on rigid experimental grounds.

    Constants can be derived in a number of ways, and in fact some constants are not really all that constant. The Hubble constant is derived by BB cosmologists interpreting the distance/redshift relationship as a sign of cosmological expansion. This particular "constant" has been anything but, and at times has been suggested to be at values that would place the age of the universe at a fraction of the age of the oldest stars. A constant of this type can be a convention based on consensus, and is far less likely to be as accurate and reliable as a "law". Some constants are invented to solve an intractible math problem in a complicated theory and stabilize it. Einstein invented the cosmological constant to ensure that his theory of General Relativity did not allow a theoretically infinite universe to collapse due to gravitational instability. This "constant" has been "on again off again" for decades, ranging from thoroughly discredited to cherished. So much for constancy.

    I realize this answer may not have been as helpful as you might have liked, but please realize that "constants" do not follow from laws as cleanly as you might hope. I think they arise more commonly to fit pet theories with incalcitrant observations.
     
  4. Mar 31, 2005 #3
    Which constants specifically?
    There are constants of proportionality and definitive constants.
     
  5. Mar 31, 2005 #4
    turbo-1:the hubble constant evolves with time.
     
  6. Mar 31, 2005 #5

    marcus

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    the constants typically occur as coefficients in the laws, so that if you could change the constants it would change the laws

    to sharpen up the discussion the first thing you need to do is get rid of this talk of "hubble constant" because it is a poor example. Today's cosmologists are very apt to call it "hubble parameter" instead. It is a no-brainer that the hubble parameter is NOT a physical constant and it is only called such sometimes by historical accident.

    the best examples of constants are what you get if you google
    "fundamental physical constants", which is you will probably get the US gov website of the NIST (natl. inst. standards and tech.) which has a list of
    all the physics constants they can think of, with the most accurate values known.

    and BTW they do not include the hubble parameter in their list :smile:

    Or if you have a hardcopy Handbook of Chemistry and Physics, look in the index for "fundamental physical constants" and you will get a list corresponding to the NIST online list.

    Goldbars, i think there is an integral connection betwen the constants and the laws. The constants derive their whole meaning from how they function in the laws. And many of the laws are expressing some proportionality where the proportion or ratio is one of the constants.

    As an example. the StefanBoltzmann constant (often denoted "sigma") is the KEY to the Fourth Power Blackbody Radiation Law. this is for cavity radiation and for dull nondescript commonplace hot surfaces that can be treated as a black body. (the surfaces are not allowed to be shiny reflective or have special absorption emission properties)

    the power per unit area of the radiating surface is equal to the temperature raised to the fourth and multiplied by sigma

    If you say "the power per unit area of an ideal radiator is proportional to temperature4"
    then you are tacitly referring to the constant sigma because sigma is the proportion so the laws and the constants form an inseparable tangle and are part of each other
     
  7. Apr 1, 2005 #6

    Chronos

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    The laws of physics are derived from physical constants, not the other way around.
     
  8. Apr 1, 2005 #7
    Could it be that there is some reason why our universe has the value it does, but it could still theoretically have been different because that particular law is true for our universe, but not necessarily true for all possible universes? Universes with different constants different effects and interactions?
     
  9. Apr 2, 2005 #8
    That was Einstein's problem - when he mused whether God had any choice when he made the universe. While its true in most models of the universe, the Hubble constant is a variable, there are some cosmologies where it is constant - but they are usually not mainstream physics. My own guess is that most of the factors we tend to call constant do vary in the long term scheme of things - an expanding universe by its very nature would seem to require that parameters that carry dimensional units such as G are not likely to be the same in the early universe - we sort of impliedly endorse the notion of temporal variance when we embrace inflation as a stage in the evolution that has led to the present.
     
    Last edited: Apr 2, 2005
  10. Apr 2, 2005 #9
    Constants have a lot to do with laws in many ocasions. And if the universe was different, then all the constants would also be different.

    So I think that constants are affected by natural laws.
     
  11. Apr 2, 2005 #10

    marcus

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    You might get quite a lot out of reading an essay by Lee Smolin
    proposing a mechanisim for how the values of the basic constants for our universe were determined (by an evolutionary process leading up to the big bang)

    the essay came out this year and is to be published by Cambridge University Press in a collection of essays on this general topic

    but Smolin's is the only one I know that's available on arxiv.org

    the essay is called "Scientific Alternatives to the Anthropic Principle"
    http://arxiv.org/abs/hep-th/0407213

    it made a prominent advocate of the Anthropic Principle quite angry because it makes definite predictions and offers a mechanism for why the contant-numbers in our universe HAVE to be approximately what they are and not widely different WHETHER OR NOT life has happened to evolve. it is a mechanism he figured out that works independent of whether we are here to see it, and it makes predictions astronomers can test and throw it out if it predicted wrong

    this makes the AP look bad because it says that the constants are essentially random and undetermined ----but given that life evolved they have to be about what you see because otherwise it would be unfavorable to life. "thats how it is, because we're here to see it"
    It is not a scientific explanation because it doesnt predict the outcome of any future experiment which could falsify the theory. (to be meaningful scientific theories must be testable: must make predictions by which they could be refuted if they predict wrong)
     
    Last edited: Apr 2, 2005
  12. Apr 2, 2005 #11

    turbo

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    Smolin's paper is a great one, not because I subscribe to his views, but because it turns the "Anthropic Principle" on its head. The AP is pretty silly. In the same spirit, I hereby propose an "iPodic Principle". The presence of iPods in the universe proves that the universe is fine-tuned to produce them. Obviously, if any of the constants and properties of the universe were altered, no iPods could exist, because we wouldn't be here to conceive of them and make them and enjoy our private Bach concerts. Just don't thrash around and mumble the lyrics, and the other people on the bus won't know you're listening to AC/DC. (I'm on a Highway to Hell!....) :devil:

    By the way, if you Google on "physical laws and constants" you will find yourself swamped in creationist links. Just try it and see how little real scientific content you will encounter. It's a bit scary.
     
  13. Apr 2, 2005 #12
    So would physical laws would differ from universe to universe? just throw out ya best guess
     
  14. Apr 2, 2005 #13

    marcus

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    make ya deal. you read the first few pages of that Smolin article
    and THEN we tell each other what's our best guess

    just go here
    http://arxiv.org/abs/hep-th/0407213
    and click on PDF to download it
     
    Last edited: Apr 2, 2005
  15. Apr 2, 2005 #14
    I just read the abstract and conclusion and I still dont understand it fully.
     
  16. Apr 2, 2005 #15

    marcus

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    Good! dont have to understand fully. but you need to get into it a ways

    in the CNS model universes reproduce and pass their "DNA" of physical constants along to their offspring universes

    quick quiz question, GoldB.:
    How do they reproduce?


    might have to be pages 11 thru 15
    (maybe I was wrong to say "first ten pages", the good stuff might be like 12-14)
    =====EDIT=======
    I fished out the paper and narrowed it down to these few pages:

    PAGES 13-16 starting section 4.2

    PAGES 28-31 starting section 5.2
     
    Last edited: Apr 2, 2005
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