Would a change in laws of physics be noticed?

Discussion in 'Physics & Math' started by Dinosaur, Nov 6, 2005.

  1. Dinosaur Rational Skeptic Valued Senior Member

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    If major laws of physics changed with distance or time, would there be measurements and/or experiments which would tell us?

    For example, suppose gravity got weaker or stronger over the age of the universe. A change in the gravitational constant would affect the life cycle of stars, which I suppose would be noticeable.

    For example Both the color and the time period of variation for variable stars depends on their mass. Those variable stars which are much farther away are being viewed as they were a long time ago. I would expect a variation in the constant of gravitation over time to result in some noticeable differences among variable stars at various distances (ergo various times).

    I have noticed articles speculating on the laws of physics and/or various constants changing with time or distance, but have never seen any description of the possible effects.
     
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  3. PhysMachine MALLEUS SCIENTIARUM Registered Senior Member

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    There's actually a result in QFT about massive photons, which concludes with the Yukawa potential being the correct one for the electrostatic interaction. It leads to some quantitatively different physics.
     
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  5. Arcane Guest

    First, the Laws of physics dont change.

    and second, if they did, for example if gravity was to strengthen, and it became an inverse square ROOT law, the entire universe would collapse under its own gravitational pull. think big crunch.. lol

    Arc
     
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  7. Dinosaur Rational Skeptic Valued Senior Member

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    Arcane: First, I find it hard to believe that the laws of physics change.

    Second, I have read articles suggesting that the laws have changed over time and/or that they are different elsewhere in our universe. The latter speculation seems unreasonable.

    Pointing out the effects of gravity being drastically different (EG: An inverse square root law) is a bit of a strawman.

    BTW: there are some logical reasons why electromagnetic and gravitaional forces are inverse square laws.

    What has been suggested is that one or more constants have changed as the universe ages. For example, the gravitational constant might have been slightly larger or smaller billions of years ago or the speed of light might have varied slightly over billions of years.

    I merely wondered if any of the speculators considered the consequences of such changes and tried to verify or refute such speculations. It is my understanding (which I do not trust much) that some of these speculators are knowledgeable scientists. Of course, I happen to be aware that some knowledgeable scientists wrote The Jupiter Effect, which was nonsense and known to be such by the authors. I do realize that knowledgeable scientists can have flights of fancy, periods of irrationality, and/or decide to sell their academic credentials for cash.

    For example, suppose the gravitational constant was 1% different when the universe changed from radiation dominated to matter dominated (about 3-4 hundred thousands years after the Big Bang, assuming the validity of that theory). Suppose it has changed at a constant rate over the last 12-14 billions years, and is still changing at that rate. Could modern measurement technology detect that gradual a change if it tried to do so? Probably not, especially since the gravitational constant is one of the least accurately measured constants of physics.

    If the current small change could not be measured, would there be some predictable and measurable long term difference in some phenomena due to the total change? Would the life cycle of some stars be noticeably different, allowing us to detect such a gradual change? Note that the life cycle of a star like our sun is about 10 billion years, while the life cycles of some extremely massive stars is much shorter. Would a 1-2% difference in the gravitational constant in the early universe result in some effect noticeable from comparison of massive stars from that era with similar stars existing today?
     
  8. Physics Monkey Snow Monkey and Physicist Registered Senior Member

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    The laws of physics might change. In particular, Lee Smolin has put forward a number of interesting proposals. String theory seems to allow different regions of spacetime to have different "laws of physics" i.e. different particle spectra and relative force strengths, etc. String theory might also permit tunneling between these different vacua thus allowing the "laws of physics" to change. Not everyone is keen on the idea, but I don't see how anyone can just rule it out.
     
  9. FineStructure Registered Member

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    It would be hard to imagine how the actual laws of nature could vary fundamentally within our universe without having observable consequences. Most of our theories or partial theories that describe the macro effects seem applicable both here on earth and in the wider cosmos. The "constants", however, have been suspected of not being quite as constant as we would like to believe. It is hard to conclusively prove they have not varied; all we can do is to ascertain the maximum amount by which they could have varied using observational methods. As far as i can remember, it has been shown that G cannot have varied by more than 1 part in 2.5x10^9 in the last 10b years, i.e. it has probably not changed. The fine structure constant α (e2/h bar c ≈ 1/137) is currently most under suspicion following observation of differences in the separation of spectral lines from clouds of gas some 12 billion light years away, but this again is inconclusive and controversial. Until we have a theory that can give a convincing reason for the constants having the values they do, or that permits us to calculate them from axioms, we will never know for sure...
     
  10. Ballyhoo Registered Member

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    Recently there's been some evidence of changes in certain "constants" such as the speed of light. I'm not sure if this would constitute changes in laws, but it's interesting anyway.
     

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