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More silly semantics that are nagging me

  1. Jun 17, 2006 #1
    Ok here's another question: A friend of mine shook her head in doubt and disbelief when I said that I believe physicists when they say that the universe is constant and is the same everywhere... meaning that the laws of physics don't change whether you are in this galaxy or in another. She believes that the laws of physics that we discovered aren't necessarily the same here as they are somewhere else in the universe. For example the properties of atoms of different elements. How would you prove or explain to a person like that these things are constant. That we don't have to go around the world and test every piece of silver to make sure that it has the same chemical properties in Africa as in Australia. How can we be sure that they are constant without going around and testing them. She believes that just because humans have discovered something that works here on Earth it doesn't necessarily mean that it works the same somewhere else. I asked her what would lead her to believe that it would be any different somewhere else but she insisted that I had to prove to her first that it is constant to begin with. Someone else I talked to about this very question mentioned something about spectroscopy and how through that we know that things are constant. Any help?
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  3. Jun 17, 2006 #2

    Andrew Mason

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    There is abundant evidence of how matter and energy behave at great distances. So far, we have found no evidence that is inconsistent with the laws of physics being the same all over the universe.

    But science does not really prove truths. It merely tests hypotheses. Although no one will be able to prove that the laws of physics are the same everywhere, so far no one has been able to find evidence that the hypothesis is false.

    We will continue to make observations and develop models of the universe based on that hypothesis until we find clear evidence to the contrary.

  4. Jun 17, 2006 #3


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    A mathematician and phycisist named Alexander Friedmann once made the assumption that the universe would look the same everywhere in whichever direction we look. This implied that the same would be true if you looked at it from different places in the universe.

    This was later found to be true when in 1965, two scientists named Penzias and Wislon, discovered microwave radiation. This radiation remained constant in whichever direction the device was pointed at in the sky!

    Surely that if the universe was not constant, these waves could not be the same everywhere!
  5. Jun 17, 2006 #4


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    The mere consistancy of our observations of the universe is, in of itself, strong evidence that the laws of physics do not vary from point to point in the universe. We look across the universe, and everywhere we look, it looks the same. We see the same types of Galaxies, they all emit the same kinds of raditation, if you look at their spectrums, you find the same spectral lines as you do for elements here on Earth etc.

    If the law of physics varied from place to place then we shouldn't see this consistancy. Galaxies would look different when we looked at different points in the Universe. Galaxies here would look nothing like galaxies there. We wouldn't see the same consistancy in spectral lines etc.

    Instead of the uniformity we see, we would see a random mish-mash.

    The only other possibility would be that the unverse only differs from place to place in those properties that we cannot see. Considering the interdependency of physical properties, that would imply imply some kind of universal conspiracy, and that is extremely more less likely than the universe simply being uniform to begin with,
    Last edited: Jun 17, 2006
  6. Jun 20, 2006 #5
    Your friend is actually correct in a way. It takes a leap of faith to state that the laws of physics are the same EVERYWHERE. That's why it is so cool when we make a prediction about something .... and it works!!!
  7. Jun 20, 2006 #6


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    Dearly Missed

    Any science worth its name does these leaps of faith all the time. This is part of the PREDICTIVE side of science.

    Another side is to report and correlate data. This is an absolutely necessary part of science, but mere reports and correlations is not all of science.
  8. Jun 20, 2006 #7
    If your friend is knowledgeable in physics and still thinks that this is the case, then there really is nothing wrong with it. Your friend just wants more proof. If your friend knows nothing of physics then there really isn't much that you can do to change her opinion. In this case, it happens to be that most people who are knowledgeable in physics do believe that the laws of physics are uniform throughout the universe. People who are ignorant of a particular subject really don't have enough knowledge to make a valid assumption. If this is the case, then just let it go.:tongue2:

    The only thing you could do is to ask her to learn more about the subject...maybe refer her here.
    People's faith in science is based off of evidence, and predictions are made from this evidence. When these predictions come true, one can't cease to be amazed.
    Last edited: Jun 20, 2006
  9. Jun 21, 2006 #8
    @ Omega: Heh well she is not a physicist... neither am I for that matter. I was just surprised to hear that from her because I believe that she is a very intelligent and reads alot about different subjects. I just thought that this is a case of pink unicorns. By that I mean ... a person can very well say that "you don't know that pink unicorns don't exist". That person would be correct however the proof rests on the person claiming that unicorns exist or doubts a person who says that there is no evidence for unicorns therefore as far as we know they don't exist. So when I asked her to show me what exactly makes her think that the laws of physics aren't necessarily constant everywhere in the universe she said that I had to prove that they are so in the first place. But I don't think that I have to prove that... all the evidence that we have points to that conclusion already and there is no reason to think otherwise. Surely we can speculate... but what reason would make us speculate unless we're in the business of writing a fantasy novel?
    Last edited: Jun 21, 2006
  10. Jun 21, 2006 #9

    Andrew Mason

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    Physicists look for evidence not only that the laws of physics are the same throughout the universe but that the laws of physics have been the same since the universe began. That is an interesting question that is the subject of a lot of current research. See: here and here

    So far there is no clear evidence that the speed of light has changed, but the question is still open.

  11. Jun 21, 2006 #10
    This is exactly my point. How are you supposed to argue with someone who needs absolute proof of your theory (when there is evidence for it), but has absolutely no proof or evidence of their own "theory". This almost sounds like a case of someone just trying to go against common theories in the only way they know how...in a ridiculous manner. The only way to PROVE without ANY doubt that the laws of physics are the same everywhere in the universe is to test them everywhere in the universe. This is certainly impossible. Since she seems to only want to break away from the norm, ask her what evidence there is for her own theory. She obviously has none, but at the same time she is allowed to believe whatever she wants.

    No valid theory can be posed on the basis that another theory is wrong. In order for the preposed theory to be accepted it must have its own evidence. If not, then it is just a belief. (intelligent design falls under this category of "theories")
    Last edited: Jun 21, 2006
  12. Jun 22, 2006 #11
    She doesn't have a theory actually... her exact words were "I refuse to believe that the laws of physics that are detected here on Earth or Solar System are the same as in another galaxy" ... later on she added "in another dimension" (shifting ground?) but anyway there she may be right... but no one has been to any other dimension other than this one as far as I know. I think she has a sort of contempt or derision for science-minded skeptical people, that they are closeminded... that just because humans here discovered something works doesn't mean that it's the same everywhere else. Oh well.. I love my friend anyway so I don't really want to bash her but ... I wanted to settle the question with people that actually have the authority on this subject.
  13. Jun 22, 2006 #12


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    I think it is a very smart point for her to raise!! Most people don't even stop and think about fundamental issues like this! I think she should be *praised* for raising such a deep issue.

    The only question now is whether she would understand and accept the answer. That's another story!

    The answer is that there i sno way to *prove* that the laws of physics are the same everyhwere. Or that they are the same all the time for that matter (if I measured the acceleration of an object falling near the surface of the Earth under cntrolled conditions for 30 years, there is no way I can prove that I will get the same result tomorrow morning).

    Ask your friend: does she believe that if she runs full speed into a wall while visiting Beijing she might not get hurt as much as if she does it at home? If she does, it's because she believes that the laws of physics are the same there than they are here.

    It's like saying that there is no way to disprove that some god created the entire universe 2 minutes before I was born...or that this created the entire universe 2 minutes go, with all my memories implanted in my mind when I was created.

    Scientists *are* open to the idea that the laws of physics may differ in different locations. But all present observations (of light coming from other galaxies, of the cosmic background radiation etc etc) suggests strongly that we are right in asusming that the laws we know apply everywhere. If we did find out that they don't (or that they don't apply the same way at all times) we would try to find a deeper theory that would account for that which means that this new theory *would* everywhere and at all times by definition.

    Without the assumption that this is feasible, science is moot and we might as well stop doing anything. So far, it has permitted us to go to the Moon and much beyond, to treat numerous diseases and on and on.
  14. Jun 22, 2006 #13
    Most of the people who try to answer such complete questions are biased by
    deductive science. The way lies in quitting biased mindsets and thinking about things which dont happen otherwise. I mean some everyday things, why are they just a mix up of a few set of rules............
  15. Jun 22, 2006 #14
    The fastest horse doesn't always win the race, but it's still the way to bet. Physics' best guess isn't always right, but it's still the way to assume.
  16. Jun 26, 2006 #15
    It seems to me that

    1) It is good to understand that science hasn't proven anything about places we can't experiement on (including indirectly),

    2) anyone who "believes" that the laws of nature might not apply elsewhere in the univese just doesn't understand what science is about. It is a useless question, as with pink unicorns, or green cheese. It is the same reasoning people use to *believe* in UFOs, ghosts, God, free-energy machines, and anything else where you can't prove the negative.

    The semantics of "proven" is also slippery for this kind of person. Darwin's theory of evolution is not proven, for example. Regardless of whether she is a creationist, the problem is the same: she doesn't understand the concept of scientific proof, and if she has read as much as you've indicated, she is *refusing* to understand, and probably has read the various sensationalist physics authors (we have to contend with phd's with this same mindset :-( ).

    Since we don't know for sure that there mightn't be a 12th dimension made of cheese, let's all sit around an think about how the moon really is made of green cheese after all, it's just that we only see the non-cheese 3D projection/extrusion. :smile:

    If you don't understand Occam's razor, then you're going to believe whatever you want to. Science is about understanding what is testable, and then extrapolating with care.

    It is one thing to have an open mind. It is another thing to take it to the extreme where "all things are possible", which is annoying new-age (and not just new-age, BTW) ideological position that is completely antithetical to science.

    A person like this might very well have an emotional investment in believing anything is possible, especially if s/he is religious. There might be no way to convince him/her because s/he will refuse to be convinced. Such people have a subtle non-distinction between hard reality and faith which cannot be penetrated. You'll have to figure out what sort of person you are talking to, and whether you want to bang your head against a brick wall.

    Speaking of bricks... There is a test for such people. If she doesn't believe that the laws of nature are "constant", have her stand a distance away, and throw a brick at her head. If she ducks, then she should reconsider her disbelief about the "constancy" of physics. :smile:

    Of course, there is another sort of person, the "contrarian", who will take such positions just to bait people. As with other such personality types, the question is "how much of my time do I want to waste" versus "will I have fun pressing the debate [with someone with a different logic/reality structure]". Your choice: be frustrated, have fun, or walk away.

    (It appears that I'm annoyed by these "silly semantics" too :rolleyes: )
    Last edited: Jun 27, 2006
  17. Jul 5, 2006 #16
    I always hate the term 'laws of physics'. Strictly speaking they are 'laws of physicists'.

    It's always seemed a bit odd to me that the 'laws' of relativity are actually based not on a law but on a 'principle'......that of equivalence of gravitational and inertial masses. Nobody has ever shown why they are equal, which is why it remains a 'principle' to this day. Einstein just assumed that it must mean something. The whole of relativity is actually based upon a staggeringly accurate numerical coindidence......that has yet to gain the status of 'law'.
  18. Jul 5, 2006 #17
    Is there a term or phrase to describe this very thing of stating a theory based on the unprovability of its opposite?
  19. Jul 5, 2006 #18

    Andrew Mason

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    If a theory is not testable, it is not science. So no scientific theory can depend on the unproveability of a contrary fact. Rather it depends on the lack of proof of the existence of a contrary fact. An important distinction.

    This is known as the principle of 'falsifiability'. See here, for example.

  20. Jul 6, 2006 #19

    I guess I don't understand what you want a "law" to be. As I understand "law", it just means something that has been found to be true under all relevant circumstances.

    Hmm, then why is principle defined in terms of "law"?

    principle - a basic truth or law or assumption;

    Secondly, the deeper "why" of most all physical observations break down at some level given our current limits of understanding. So, saying that F=ma, isn't a "law", because of the problem of knowing exactly what "mass" is, doesn't seem like a worthwhile of productive line of thought, since in all known cases F=ma is true, and we have no reason to suspect otherwise.

    This drives toward morass of epistemology, that can be fun and all, but is more philosophy than science (which is concerned with what can be observed and demonstrated).

    Relativity is just as good a "law" as Newtonian physics. Both are true and useful, but only in defined boundaries, i.e. not at quantum levels.
  21. Jul 6, 2006 #20
    Great link. I just read an article by someone suggesting that Wikipedia will eventually become unreliable to the point of uselessness due to the unregulated edit feature. I'd hate to see links like the above (which certainly seems authoritative and unbiased), vandalized or subverted in more subtle ways. I was curious if anybody knew how all this is progressing with Wiki...
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