[Dark Matter, Dark Energy] Science?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Tristan, Feb 22, 2006.

  1. Tristan Leave your World Behind Valued Senior Member

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    I had a discussion with my physics teacher about two weeks ago. It went along the lines of the type of science being done nowadays. I presented the example of Dark Matter and Dark Energy. See, the problem with this is that it currently only exists in the minds of researchers. Granted there is math that complements it, but basically it went like this: there is a discrepancy that we can solve by creating a matter and energy that we cant see, measure, or know of.
    Now, I dont know about you, but that really bad science. Sure, there have been some things discovered in history by this method: simply creating something that should be there in the minds of the researches (then down the line it is verified).

    But what I find the funniest is how easily dark matter and dark energy was accepted. It might as well be fact... we talk about it in my astronomy class... its mentioned in lecture like a mere scribble. The media has even eaten it up and created video games with "dark matter weapons"...

    Interestingly, there are other ideas that solve the problem of dark matter at least in part. And Im sure they need to be explored more. However, they dont get nearly the attention that the famed dark matter gets. Take MOND for instance. Modified Newtonian Dynamics. It proposes a mathematical tweak to newtons laws to create solutions through newtons laws of gravitation for large scale objects (more specifically galactic rotation curves).

    Care to share your opinion?
     
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  3. 2inquisitive The Devil is in the details Registered Senior Member

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    MOND was created to solve exactly the galactic rotation curves. It does that because the rotation curves of galaxies was plugged into the theory to arrive at the theory. But it has problems. You see, clusters of galaxies also do not rotate as they should, based on standard theory. The problem for MOND is that it fails to explain these observations. What worked based on individual galaxies does not work with clusters of galaxies. MOND also fails to explain the observed gravitational lensing that has been detected caused by dark matter. Again, this is not the normal gravitational lensing of ordinary matter, but lensing due to unseen and undetected dark matter. MOND has evolved since its first incarnation to try to address these omissions, but has not been successful as of yet. There are versions named AQUAL, RAQUAL, newer TeVeS theory, and of course, Brans-Dicke theory which is not based on MOND, but is a modified gravity theory. Here is a cut and paste and link to a new paper embracing MOND-type theories, but also recognizing some their current shortfalls. (from Feb. 8, 2006)

    "It allows one to address a number of
    issues on which MOND is silent: gravitational lensing, cosmology, structure
    formation, anisotropies in the CMB. The theory is complicated– considerably
    more complicated than GR– in that involves additional dynamical elements
    and is characterised by three additional free parameters and a free function–
    i.e., a function that is not specified by any a priori considerations but may
    be adjusted to achieved the desired result. In this sense, TeVeS, like MOND
    itself, is a phenomenologically driven theory. It is entirely “bottom-up” and
    thereby di ers from what is normally done in gravity theory or cosmology.
    As the name implies it is a multi-field theory; i.e., there are fields present
    other than the usual tensor field gµ of GR. It appears that any viable theory
    of MOND as a modification of gravity must be a multi-field theory; no
    theory based upon a single metric field can work [43]. In TeVeS, the MOND
    phenomenology appears as a “fifth force” mediated by a scalar field."
    http://arxiv.org/PS_cache/astro-ph/pdf/0601/0601431.pdf
     
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  5. squishysponge Registered Senior Member

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    Yea I personally find a lot of the science in cosmology very 'unscience' like too. They are mostly theories with very little concrete proof. For example I dont really like the explaination they give for big bang. I think the furthest they can go back timewise, is explain that bigbang was caused by the collision of parralell branes? The collision caused this energy to come out of nowhere in our universe, and since einstein's theory of special relativity states that E=mc^2, this energy was interchangable to mass! Wow! I cant remember exactly. But frankly, thats not ggood enough cause they need to now explain how and why these two time branes can move. Where is the energy comming from, for that, in which case you can furthur go down the road to a seemingly neverending quest for an absolute beginning.

    The problem is though, we always judge all sciences based on the first law of therodynamics stating energy conservation. What if this is not the case in terms of cosmology and the big wide universe and beyond. Yet I think all models are modelled around this theory, which may not even apply beyond our known universe.

    Anyways back to your point. I think dark energy and dark matter are missing pieces that they know has to exist due to astronomical observations to explain the irregularities they see with stars and galaxies. The construction of the periodic table was similar in fashion where mendeleev ordered chemicals based on atomic mass and realized there has to be missing elements to be discovered. Even thought his table was inaccurate compared to todays understanding, he was right in his prediction of the existance of the missing elements.
     
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  7. Anomalous Banned Banned

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    the prediction of dark matter says that there is something wrong with our science.
     
  8. Tristan Leave your World Behind Valued Senior Member

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    But see, thats the problem. We are looking at a galaxy and calculating a mass x. It should have a mass x. But then the gravitational lensing and our observations indicate it has a mass x+z. So we assume, naturally, that z is simply unseen dark matter. Could there not be another explanation? Some error in the calculations.

    Indeed the periodic table is one example where this kind of science worked. But dark matter is untestable. It just fits nicely into a mathematical formula... and the problem with that is that if you have a formula and you apply it to nature... and it doesnt work... you could always just tweak it here or there, make up a number to make it work.... and thats what it seems like we are doing with dark matter.
     
  9. Tristan Leave your World Behind Valued Senior Member

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    Btw, thanks for the information on MOND and sister theories. Much appreciated.
     
  10. RoyLennigan Registered Senior Member

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    you guys just don't understand how science works. you can't expect scientists to know exactly everything that goes on in our universe. scientists have to make a prediction before it can be disproven, thats how science works. they observed the universe and saw that their predictions of gravitational interactions did not fit their observations of them. so they developed a new theory which fit their observations more accurately. whether its right or wrong, it works right now with every observation made. if there is evidence that contradicts this model, then the theory will be modified again.

    also, the prediction of dark matter and energy is based almost entirely on mathematical interactions--equations that actually work. we have to assume something about the universe around us because none of our theories are 100% correct.
     
  11. Tristan Leave your World Behind Valued Senior Member

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    Yeah BUT dark matter is already considered fact... its not talked about as a theory anymore... thats the problem! If it was, "the theory of dark matter explains alot...." then it would be a different story but its not a theory in alot of people's minds.
     
  12. squishysponge Registered Senior Member

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    Exactly what einstein did. He added a cosmological constant to his general relativity due to his personal belief that the universe is fixed. It took hubble and a priest I believe, to convince him that the universe was expanding, so he corrected his theory back to the original.
     
  13. Anomalous Banned Banned

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    Just to prove that their calculations are right they cameup with DarkMatter theory. These are the darkest times in science.
     
  14. Physics Monkey Snow Monkey and Physicist Registered Senior Member

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    Tristan,

    Dark matter is a fact! Neutrinos are a perfect example of a kind of matter that is massive yet does not interact directly with light. They were very hard to detect in the first place and their existence was actually first inferred from the observation of missing energy. Does this sound familiar? The fact that something isn't there can be as telling as the fact that something is there. Another great example is black holes; do you believe black holes exist? By your reasoning it must be silly science to talk about black holes since we can't see them directly (unless they are very small) and must instead infer their existence based on their gravitiational effects. Dark matter is very similar since its existence is inferred from observation using a very well tested theory. It is really a prediction of the theory, namely that we should some day be able to find (perhaps in a particle accelerator) just exactly what dark matter is.

    The bottom line is that dark matter is not just some silly nonsense that people came up with one day and suddenly the whole world of science was blinded by it and no one could think anymore. Nothing could be further from the truth. If you actually look at the early history of dark matter, it is full of poor communication with several different groups realizing independently the need for dark matter in very different contexts. Dark matter is only generally accepted now because there is considerable and consistent evidence for its existence. Most of the other ideas that you mention continue not to have the same level of success. I urge you to reconsider your opinion on the matter and have a little faith in your astrophysicists and astronomers.
     
  15. RoyLennigan Registered Senior Member

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    it is not considered fact by a lot of people. there are still many scientists who are collecting data to disprove other scientists idea of dark matter. and to most it is still a very theoretical idea.
     
  16. Tristan Leave your World Behind Valued Senior Member

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    Good argument Monkey. Duly noted
     
  17. Dinosaur Rational Skeptic Valued Senior Member

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    Like most theories, dark matter is merely the best explanation we have for certain observations. If somebody came up with a new set of gravitaional equations which explained the observations, dark matter theories would be junked.

    Initially, they talked about Macho's (Massive Cold Halo Objects) & Wimp's (Weakly Acting Massive Particles). For various reasons, the Wimp's won (mainly because it was thought that Macho's could be detected if they existed in large quantities).

    The observations definitely indicate that either our gravitational equations are wrong (or not applicable to stellar movement in galaxies) or there is something which we cannot detect except via its gravitarional effects.

    The scientists could have come up with some clumsy phrase like Unknown Gravitational Phenomena and/or Unknown Error in Gravitational Equations, but dark matter seemed like a handier term, and they had no reason to suspect that the GR Equations were erroneous.

    I suspect that there was a brief period of time when some MOND-like theory was being investigated at the same time that dark matter theories were being proposed.
     

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