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Food for thought, is law of inertia wronghum

  1. Feb 10, 2010 #1
    So just a thought that popped into my head, and I wanted other peoples opinion on it.
    What if a fundamental law in science is not quite right, I was thinking about the first law of motion. I realize that sounds stupid, but I was reading an article about dark matter…
    Link and excerpt bellow…
    http://www.scientificamerican.com/article.cfm?id=dark-matter-modified-gravity"

    The bad news is that in order for modified versions of general relativity to work, some sort of unseen—or "dark"—presence must be in play, which in some cases can look a lot like dark matter. "If you try and build a consistent, relativistic theory that gives you modified Newtonian dynamics, you have no choice but to introduce extra stuff," Ferreira says. "I don't think it will be described by particles, in the way that dark matter is described—it may be described in a more wavelike form or a more fieldlike form."

    Note the comment, “modified Newtonian dynamics”, he means inertia.
    So ok, then what if there is no dark matter, then what? Thats when this idea hit me…. What if the laws of inertia were wrong, lets say space-time, aether (whatever you call it) had a natural resistance to change, meaning it didn’t like to expand or curve. That very concept could account for dark matter. Then apply to a smaller scale because all matter curves space-time even small pieces of matter, like all the satellites experiencing the pioneer anomaly. Maybe we don’t need dark matter, maybe all we need is to understand that space-time has a natural resistances to change and that could apply a force onto matter…of course that would mean we would have to rewrite the law of motion.

    What do you all think?
     
    Last edited by a moderator: Apr 24, 2017
  2. jcsd
  3. Feb 10, 2010 #2

    russ_watters

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    Newton's laws are definitely right and definitely wrong. It's all a matter of domain of applicability.
     
  4. Feb 15, 2010 #3
    kind of a slow fourm huh
     
  5. Feb 15, 2010 #4
    I suspect you are not getting responses because vague ideas are a dime a dozen...

    it doesn't...takes energy,mass or pressure to curve it....after those effects pass it is again flate spacetime....within experimental levels of accuracy energy is conserved so none is loss to space time in the manner you suggest....

    maybe we don't need dark matter...but we do need to understand why spiral galaxies spin in the manner observed. All ideas and theories might be considered "great" until proven otherwise by actual experimental results....
    Thos darn actuals seem to screw up otherwise great theories rather often...
     
  6. Feb 16, 2010 #5

    Sorry if the frist post was vague..

    Energy is conserved so none is loss... thats kind of what I was getting at, is all the energy really conserved, has that been proven or is what we just believed for years and years, and we take this for granted? Cause it would seem with pioneer anomally some energy is loss somewhere, and with the expansion of the universe things don't expand as fast as it's suppose to. Why couldn't space, aether, or strings...whatever absorb some the energy?
    The proof is in the pudding, and seem like most the motion in space is slightly off on how we think it's suppose to be and some energy is or could be lost somewhere. Maybe spiral galaxies work more like spinning stuff around in water which why they all seem to that black hole in the center.
     
    Last edited: Feb 16, 2010
  7. Feb 16, 2010 #6

    Vanadium 50

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    Again, this is vague. "Maybe things are just different than we think" is not something that will lead anywhere useful - you need to be specific, and quantitative. (And if you want to do it here, please read the section in the PF rules on overly speculative posts)
     
  8. Feb 16, 2010 #7
    Wait most of science is speculative, for example dark matter can't be proven as of yet it's speculation. The bases of me ask this was from a real interview that appaired in Scientific American (link in first post). Basicaly a comment in the story when talking about if there is no drak matter was.....

    If you try and build a consistent, relativistic theory that gives you modified Newtonian dynamics

    ...read the whole if you want it in more context..

    I'm simply asking what peoples opinion on that is, and what if there is no dark matter, could we really have to modify Newtonian physiscs? I don't have a theory I just have a question based on this artical.
     
  9. Feb 16, 2010 #8
    Where was this first post again and what were you asking in it?

    I will take a look back at it and see a) if and where you went wrong in your logic, if you did at all b) if your logic is somehow correct, I will try to clarify what you are asking on your part for everyone else before they answer.

    (Your original post at the top of this thread just seems to be all over the place thus I state what I did above.)
     
  10. Feb 22, 2010 #9
    Ok let me see If I clarify this….

    Scientific American did an interview with Pedro Ferreira, from University of Oxford . The Title of the interview was, Tweak Gravity: What If There Is No Dark Matter?
    Link is here http://www.scientificamerican.com/article.cfm?id=dark-matter-modified-gravity[/URL]

    To paraphrase, a question was asked what would the model of our universe look like if there was no Dark Matter. This was part of the response…

    [quote]
    The bad news is that in order for modified versions of general relativity to work, some sort of unseen—or "dark"—presence must be in play, which in some cases can look a lot like dark matter. [b] "If you try and build a consistent, relativistic theory that gives you modified Newtonian dynamics, you have no choice but to introduce extra stuff," Ferreira says.[/b]
    "I don't think it will be described by particles, in the way that dark matter is described—it may be described in a more wavelike form or a more fieldlike form."
    [/quote]

    In that paragraph notice the statement in bold…

    So if I’m understanding the his saying we have to have extra stuff (matter drak matter) or change Newtonian dynamics (meaning Newton’s laws of motion)

    So what my post was trying to ask what do you think about this comment?
    Could the idea of dark matter be wrong, and Newton’s laws of motion need tweaking or not so much Newton’s laws but the fact that maybe some energy is lost to space time…or perhaps a better what to say it that space-time has a thickness to it, keep this mind when thinking about it….

    1. There is a problem with motion of things in space which why dark matter came about.
    2. the only man made objects that I know that have travel at any long distance for any long period of time are satellites like pioneer which all seem to suffer from an anomaly were they are not moving as fast as they should.
    3. Dark matter has not be detect and is theoretical and was introduced to explain problems with motion is space.


    What do you all think about that comment from the article?

    (hope that is more clear)
     
    Last edited by a moderator: Apr 24, 2017
  11. Feb 23, 2010 #10
    Maybe he means force does not go as 1 over distance squared. Which has nothing to do with inertia.
     
  12. Feb 23, 2010 #11

    Matterwave

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    MOND (modified Newtonian Dynamics) is indeed a theory which tries to explain the rotation curve of galaxies. Here is an article on it: http://en.wikipedia.org/wiki/Modified_Newtonian_Dynamics

    I'm not too familiar with the current acceptance/usability of MOND, but it definitely isn't as successful as general relativity! I think...but I'm not sure, that it introduces new problems while solving old ones...
     
  13. Feb 23, 2010 #12
    see the book "Reinventing Gravity: a physicist goes beyond Einstein" by John Moffat.
     
  14. Feb 24, 2010 #13
    From the wiki site you link too...
    Well, that kind of sounds like inertia although it’s not directly said on the site.
     
  15. Feb 24, 2010 #14
    ...to add, I know people here hate personal opinions on this forum, but personally I don't think there is dark matter, I think we're missing something and due the fact science hates to go back on ideas (speaking in General), its going to be very hard for new ideas to come out. Many scientists are dead set on ideas like dark matter and will attempt to find holes in new theories instead of trying to help patch holes to make better theories.
     
  16. Feb 24, 2010 #15
    I think that there is a lot of confusion as to what modified Newtonian dynamics means here.

    One idea that has been bounced around is that there is either no dark matter or less dark matter than we think and that the law of gravity is just different than we assume. In order to get some numbers out, what you do is to take Newton's law of universal gravity, change it and then see if you can get things that look sensible. Now if you just ended up with different equation that seems to fit everything, you might be on to something, but the trouble is that you sort of have to have a different equation for each galaxy which suggests that maybe the problem isn't modified gravity.

    I don't think anyone has suggested modifying the rules of inertia, and I think that's because it's not obvious how that will help solve the problem,
     
  17. Feb 24, 2010 #16
    What gives you that idea? It would be really boring if we thought we understood everything. Personally it's more interesting when everything you think you know is wrong, because if everything you think you know is right then there wouldn't be much need for research scientists.

    Anyway there are reasons why dark matter is preferred over modified gravity theories, and you can do a search of this forum for the specific reasons.
     
  18. Feb 24, 2010 #17
    No he doesn't. He means changing the laws of gravity to get things to work. Here is a search of the literature database

    http://adsabs.harvard.edu/cgi-bin/basic_connect?qsearch=modified+newtonian+dynamics&version=1

    It has 872 papers on the topic.

    The trouble is that this doesn't work, because if you change things at small scales, lots of experiments break. Something about is true all of the modified Newtonian dynamics proposals is that they go out of their way to make sure that you get the same behavior as standard gravity at small scales.

    There are 872 papers on this topic. The consensus answer right now is "probably not." Short answer is that once you do the math, you don't end up with anything too convincing.
     
  19. Feb 26, 2010 #18
    When I get a little time I will read some of the papers. However I would like to make a few quick comments. I don't think any of the math has been working out 100%, I believe no matter what theory we look at we can find a few flaws in math. Theses satellite anomaly is a good example of that, something not working out right. I believe saying ever satellite having this problem is leaking gas is just stupid.

    Now per modifying gravity theories, gravity is said to be the curvature of space-time, any theory that modifies gravity, modifies this space-time curvature, thus changes the way we think of space-time. It doesn’t seem like you can change the rules for gravity without changing the rules for space.
     
  20. Feb 26, 2010 #19
    I don't think so. It's pretty simple to get your math right. Now it may be that your math isn't describing the actual situation, but that's something different.

    Why? It could be correct. It's well know that the orbits of asteroids can be changed by radiation pressure or by outgassing. I mean, people went on a wild goose chase looking for planet X for about 150 years because people miscalculated the mass of Neptune.

    Also if you do figure out that Pioneer is leaking gas, that doesn't end the question, but just opens up a whole new set of questions. One thing to look at is how observationalists are very careful to eliminate silly things before you make extraordinary claims. Are we really seeing the big bang, or is that just pigeon poop.

    People haven't gotten that far yet. Right now people are basically in "curve fitting" mode. Can we come up with *any* modified theory of gravity that nicely matches observations, and the answer is more or less "not really"? Once you come up with something that works *then* you think about how that modifies space-time.
     
  21. Feb 26, 2010 #20
    Last edited: Feb 26, 2010
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