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The Interpretation of Theory (In the Context of Gravitation)

  1. Jul 17, 2005 #1
    About a week back I posted in the strings forum asking about how current theories interpret gravitation and how they differ from general relativity. But the main subject of the thread wasn't how physical theories should be interpreted, so I'd like to pose that question again, in greater detail here. I had wanted to post this in the relativity forum because I am most interested in the opinions of those who are fond of general relativity, but I realize this question may be a little too far into the field of philosophy, so decided to spare the mentors some time and go ahead and post it here :redface:.

    My question is, how important is the exact interpretation of theories, rather than just their predictions? In particular, is it better to think of gravity in terms of space-time actually, physically being warped, or should one only take the idea of space-time curvature as a model that merely yields accurate predictions to the current extent that we can test with technology?

    As Greene points out in The Elegant Universe, Newton found it "inconceivable that inanimate brute matter, should, without the mediation of something else, which is not material, operate upon and affect other matter without mutual contact". Newton, of course, never came to any solutions to what the agent of gravity actually is, and left that to a future generation to decide.

    And, as you all know, Einstein found a reason that gravity could act between distant bodies. In Einstein's general theory of relativity, the agent of gravity is space-time itself, as it becomes warped due to the existance of matter. I have to say, I love this interpretation of gravity, and one of the major things I dislike about string theory is that it changes the agent of gravity from space-time to a string vibration. But, string theorists will state that the general theory of relativity is a special circumstance of their equations, just like Newton's theories are special circumstances of Einstein's. This raises a dilemna because, whether or not string theory's equations reduce to Einstein's, they absolutely seem to go against Einstein's belief in what the agent of gravity is.

    Thorne seems to prefer the idea that the only important thing about a theory is its predictions, and not the specific way it interprets the world:
    - Kip S. Thorne, Black Holes and Time Warps, pg. 85-86

    D'Inverno agrees with this sentiment, stating:
    - Ray D'Inverno, Introducing Einstein's Relativity, Section 2.1

    However, it is also true that physicists are fond of aesthetics and simplicity. There seem to be many who claim to have aether theories that give the same predictions as relativity, but differ mainly in the interpretation of what causes time dilation and length contraction. The difference is they require a luminiferous aether, which Einstein showed to be a useless concept, and, in the spirit of Ockham's razor, the aether has been viewed as extra baggage and discarded. Also, as stated previously, Newton was aware that his theory of gravity wouldn't be the end of the story because it doesn't even have an interpretation. Newton didn't have any ideas about what could cause gravity, but realized that there must be something that causes it. So, on this level, there is some importance to both the predictions of physical theories as well as their unique interpretations of the world.

    I'd like to know how some of you feel about this. Should one take the stance that it isn't important what actually causes gravitation in reality as long as we can accurately predict it? Is there even any such thing as a physical agent of gravitation, or is it merely an idea that we've made up to make things easier for us to picture? Or should one take the stance that gravity really is caused by curvature in space-time or a particular string vibration or some other specific mediator?
    Last edited: Jul 17, 2005
  2. jcsd
  3. Aug 3, 2005 #2
    One might call this the holy grail. It's most definitely important to explain it with perfect precision.
    My answer to this would be no. Thats because my interpretation of the entire universe says that none of it is physical at all.
    Gravity wouldn't be caused, but rather just is. Just as matter, antimatter, gravity, weak force, strong force, electromagnetic force, and Big Jims BBQ ribs are all the same thing.
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