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Are the laws of physics static?

  1. Jan 12, 2009 #1
    Since the beginning of time, have the laws of physics changed (are they static or dynamic)? Did the laws of physics change until they were suitable for the big bang to occur and create the universe? Or, from the beginning, did the laws just so happen to be able to create the universe?
     
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  3. Jan 12, 2009 #2

    mgb_phys

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    The question of wether the big bang was the start of time and if it's meaningful to talk about time or physics before the big bang is debatable.

    But leaving that aside - we can observe things (the CMB) that were created only a few 100 million years after the big bang and they certainly have the same physical laws as we see today
     
  4. Jan 12, 2009 #3

    marcus

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    Could it be possible you meant to say a few 100 thousand years? Rather than a few 100 million? The usual estimate is the CMB was emitted around 380,000 years (less than one million years) after the start of expansion.

    That is a really good question! There are a couple of Perimeter Institute video lectures about this by Lee Smolin. I will get the links in case you haven't already seen them. The first of these is probably the more relevant to your question?
    http://pirsa.org/08100049/
    http://pirsa.org/08090050/
    Sometimes I have watched these by first downloading the slides (PDF) and then turning on the audio (MP3)
    other times I have gotten the combined video/audio lecture to work. It gives you several options.

    One good point about laws being dynamic is that until fairly recently (past 100 years or so) many people including scientists could well have declared the laws of Euclidean geometry to be universal natural law, intrinsic to 3D space itself, built into the foundations of physics.
    But instead of being static, 3D geometry turns out to be dynamic and governed by General Relativity. Not absolute but affected by the disposition of matter.

    There is probably a lot of other stuff that many of us think of as absolute physical law which is, in fact, dynamic. For instance conservation laws depend on geometry, so if geometry is dynamic so must conservation laws be contingent and lose some of their absolute character.

    Another point I recall was the quote from the American Pragmatist philosopher Charles Peirce to the effect that Law above all requires a rational explanation. If we claim to be rational we cannot simply accept that the laws are as they are--we must ask why. And although this may never lead to a FINAL explanation it can lead to peeling off layers of the onion. General Relativity explains, in a sense, how approximately flat conditions (obeying Euclid) could have come about.

    Yes it makes sense to ask how particular laws have evolved to be what they are.

    ===================
    However, and this is just a quibble, I would avoid using the phrase "the beginning of time". We don't know that time had a beginning, so it is simplest not to assume that it did. Occam's Razor, don't make up unnecessary mental constructs like "beginning of time" if there is no empirical evidence for it. :biggrin: Yes it's just a figure of speech, but still.
     
    Last edited: Jan 12, 2009
  5. Jan 12, 2009 #4

    mgb_phys

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    Damn - and I even remembered the '380' part , I was only a factor of a 103 off !
     
  6. Jan 12, 2009 #5

    Chronos

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    It is usually assumed the laws of physics are constant over time. The nuclear fine structure constant [Alpha] is one tool in the physics toolbox. Alpha appears to be constant over a long period of time. See
    http://en.wikipedia.org/wiki/Fine-structure_constant
     
  7. Jan 13, 2009 #6

    Chalnoth

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    There is, however, some very tentative evidence that the fine structure constant may have changed over the history of our region of the universe:
    http://arxiv.org/abs/astro-ph/0210531

    Of course, the variation is still pretty small: just a few percent over billions of years.

    The basic idea of the observation is that when looking at the spectra of the more massive elements in quasars, they see some significant deviation from what would be expected from a simple redshift. If, however, they adjust alpha slightly with redshift, the spectra match better.

    I think this is still very tentative because there's a lot of the astrophysics of quasars we just don't know, and new things, well, usually turn out to be misunderstood astrophysics rather than misunderstood cosmology. So it seems we need to find an independent method to confirm this observation if we're going to state that the fine structure constant has varied over time.
     
  8. Jan 13, 2009 #7
    Thats one of those questions that mess you up in the head for a couple of hours at least. One person can say that it is irrelevent because space-time didn't even exist before the big-bang. Another will say, "what existed before the big bang?' The truth is that we can speculate all we want, but we will never fully understand what took place during that time. Or what never took place, I hope that came out right... Science is about observations and we may be able to recreate simalar events in a controled setting, but we cannot experience them first hand. Mabey I am just outright crazy, but in order for the big bang to occure there had to be another physical space before. What exists beyond the big bang, I have no idea. I'm gonna lose sleep over this
     
  9. Jan 13, 2009 #8

    marcus

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    I think a good many (if not most) cosmologists would agree.
    It is no longer considered a crazy/unconventional idea by the relevant research community.

    The professional organization that includes GR experts, cosmologists, astrophysicists, gravitation researchers etc is called the GRG (international society for general relativity and gravitation.) They would be the branch of the scientific establishment to ask about what you say you are losing sleep about :biggrin:

    Well, Abhay Ashtekar is someone who definitely agrees with you, and the GRG organization elected him president at their last big international conference. Ashtekar is at Penn State. His team uses computer modeling to explore possible versions of spacetime before the big bang moment.

    One of the world's top research institutes (the Einstein Institute in Germany) has an outreach website called Einstein Online (EO)
    http://www.einstein-online.info/en/spotlights/cosmology/index.html
    that deals with this. If you check it out, have a look at the short essay called A Tale of Two Big Bangs. You'll see it on the menu.

    Here's a quote from EO:
    "Most cosmologists would be very surprised if it turned out that our universe really did have an infinitely dense, infinitely hot, infinitely curved beginning. Commonly, the fact that a model predicts infinite values for some physical quantity indicates that the model is too simple and fails to include some crucial aspect of the real world....Thus, while some cosmologists do not have a problem with assuming that our universe began in a singular state, most are convinced that the big bang singularity is an artefact - to be replaced by a more accurate description once quantum gravity research has made suitable progress."
     
    Last edited: Jan 13, 2009
  10. Jan 13, 2009 #9

    marcus

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    The timeframe you have in mind, for laws to change dynamically, is up to and including the BB.

    Therefore talking about the research some years back which, if I remember, established that the fine structure constant has not changed significantly in the past, say, 10 billion years is not relevant.

    Chalnoth, perhaps you could start a separate thread about the constancy of alpha---if I remember the observational research on that was something like 2003-2005 and we had some discussions of it here at PF. My impression was that variation was pretty well ruled out but I could have missed something.

    What I think is really interesting is what YZFR is talking about.
    As I picture it, the physics laws are a feature of space. The standard model is built into space at a microscopic level somewhat the way geometry itself is. Particles, forces, masses-----and of course laws: proportionalities relating these things----are built in to each small volume of space as intrinsic properties. That's how Alain Connes derives the standard particle model, as a feature of generalized geometry.

    Maybe a collapse/re-expansion has the ability to alter these otherwise fairly permanent properties of space. Allowing the array of particles, forces, proportions to evolve.
    Not to evolve continuously perhaps (as ordinary geometry does) but episodically, in sporadic crunch/bounce events for example.

    Then the laws could be static most of the time, but still evolve (say during brief episodes of very high density and pressure). Biologists would call this "punctuated equilibrium".

    OK so that is one way of imagining dynamic evolution of laws that YZFR is asking about.
    It is not completely off-base.

    Some 20 or so prominent mainstream scientists have contributed chapters to a 600-page book called Beyond the Big Bang which is scheduled to come out this year.
    http://www.springer.com/astronomy/general+relativity/book/978-3-540-71422-4?detailsPage=toc
    One thing it will talk about is this idea of evolving physical law that YZFR has brought up, and there are already some professional research papers on it.

    The issue of testability has of course been discussed quite a lot.
     
  11. Jan 13, 2009 #10

    Chalnoth

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    Well, I'm just not interested enough to have a whole discussion on it. But as a matter of pedantics, you can't rule out variation. But you can have insufficient evidence for it. And I agree, at the current time, there is insufficient evidence.

    However, if you meant that the quasar spectra had been ruled out as evidence for a varying alpha, well, I don't think that's yet the case. There are still groups working on it, and using more data. I think we'll need some detailed 21cm observations to really say something definitive about this issue.

    With respect to the laws of physics changing during brief episodes of very high density and pressure, or perhaps due to tunneling events, I think it's worth mentioning that we're not talking about the fundamental laws of physics changing. We're just talking about the effective, low-energy laws changing. I think we all expect there to be some set of laws which are completely invariant with respect to whatever variables you might throw at them (time, location, whatever). But these fundamental laws may manifest themselves in dramatically different behavior for low-energy physics based upon the specific conditions at hand.
     
  12. Jan 13, 2009 #11
    Thank you marcus I went to that site and really learned alot
     
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