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Does the Earth actually revolve around the Sun

  1. Nov 4, 2012 #1
    Ok...My idea is a bit ridiculous.But i just wanted to know more about it from you experts.
    Scientists say that the earth is revolving around the sun and so also the other planets.
    Newton and all the other guys who were experimenting and developping physics were observing our external world while they were standing on the earth.I mean from the earths point of view.
    Then they proposed some set of laws from these observations and found that the earth is revolving around the sun.
    They did set aside the theory of sun and other planets revolving around the earth, because it didn't agree with the laws of physics.
    But today we know that there are weaknesses in our classical mechanics.
    Can there be a more improved laws of physics that explains the revolution of earth around the sun in different way.For exaple: something like sun and other planets revolving around the earth.
    Are we so sure that the earth is revolving around the sun?
     
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  3. Nov 4, 2012 #2

    russ_watters

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    With some caveats about what the statement actually means, yes we are sure that the Earth is revolving around the Sun and not the other way around.

    Physics has progressed some since Newton's time and physicists have been able to calculate the orbits of a lot of celestial bodies, not just the Earth. The flaws in Newton's model have been corrected with the adoption of General Relativity. GR explains/predicts orbits to a very high degree of accuracy.
     
  4. Nov 4, 2012 #3

    K^2

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    I do not want to try and explain accelerated frames of reference on this level. Anyone?

    Short answer, we can describe motion relative to any center, but choosing Sun as the center gives you a far more natural description. So simply put, yes, we know that Earth goes around the Sun and not the other way around.

    (Ninja'd by Russ.)
     
  5. Nov 4, 2012 #4

    russ_watters

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    I suspect the level of the question is such that it isn't necessary.
     
  6. Nov 4, 2012 #5
    But aren't we adopting that model simply because it appear to be simple.Because we believe that the things are simple in this universe.
    Because if we consider it in the other way around, it would produce a bizarre image.
    Isn't it the fact that we are accepting those laws are correct because it produces simple to understand images.
     
  7. Nov 4, 2012 #6

    russ_watters

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    No, the model we use was adopted because it works. Really really really really well.
    No.
     
  8. Nov 4, 2012 #7
    Of course i agree, adopting a different model won't make any difference to our understanding of the universe.
    For an exaple we say no object can exceed the speed light, how much the energy is supplied to it.
    Aren't we approach this limit due to a weakness in the base of our physics.Can't a different base reconstructed will explain it In a different manner.
    Similar in this case....
     
  9. Nov 5, 2012 #8
    It falls under the domain of Occam's Razor. All other things being equal, the explanation with the fewest assumptions is best. For example, take the heliocentric model vs geocentric model. The geocentric model had a complex system of orbits within orbits that predicted the motion of the planets with accuracy close to that of observations of the time. The heliocentric view is just one orbit for each planet and is just as accurate, if not more. By Occam's Razor alone, the geocentric view should be discarded.

    Having said that, the geocentric view was not thrown away only because a heliocentric world was simpler. It was thrown away because repeated and improved measurement revealed that Newtonian mechanics with a heliocentric view was better at explaining not just the motion of the planets, but all macroscopic motion.

    Adopting a different model does make a difference in our understanding of the universe. A heliocentric world is fundamentally different from a geocentric world. This isn't a "weakness" of physics.

    Take your example of the speed of light as the cosmic speed limit. The mathematics of General Relativity state that if an object is traveling through space slower than the speed of light, it is physically impossible to construct a different frame where that object is traveling through space faster than the speed of light. Again, this isn't a "weakness" of physics as we know it, it is a consequence of the math and there is no way around it.
     
  10. Nov 5, 2012 #9
    Now you are talking about newtonian mechanics.I agree with your point.
    But i was wondering whether some completely different laws of physics with a seperate base other than the newton‘s resting will explain things more differently.
    For example objects can exceed speed of light.
     
  11. Nov 5, 2012 #10

    Drakkith

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    It is mostly irrelevant. Do we observe objects moving faster than c? No. Because we don't observe this happening, and our laws of physics tell us that it is impossible, we can say that to the best of our knowledge it is impossible for something with mass to ever reach or exceed c. Whether it can actually happen and we just haven't observed it yet is irrelevant, for if we haven't observed it and we have no basis to say it can happen, then we can't talk about it as if it is possible.

    If we suddenly see neutrinos or something exceeding c, and we make sure we aren't having errors or malfunctions with our equipment, THEN we can say "Ok, we know our laws are wrong".

    Remember that we make our laws based on what we observe, not the other way around. We don't just hand wave some laws into existence and try to make the universe fit according to them.
     
  12. Nov 5, 2012 #11
    Ok..I agree with you.
    But my point is this.Do we know whether we are floating in a medium of Aether?
    Has our experiments proved the existence of aether? No they haven't. Then can we simply arrive at a conclusion that aether is just theory but nothing in existence? No we can't. We haven't dissaproved the theory of aether yet.
    It may or may be not there.But we don't know for sure.
    Because our laws of physics doesn't permit us to find it out.
     
  13. Nov 5, 2012 #12

    A.T.

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    Yes, we prefer the simplest model. As frogjg2003 said (Occam's Razor).

    No, we accept them as "correct" because they give correct predictions. But among those that give the correct predictions we prefer the simple ones.
     
  14. Nov 5, 2012 #13

    A.T.

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    It's not the job of physics to rule out the existence of all possible things that somebody might come up with.
     
  15. Nov 5, 2012 #14
    With the right coordinate system you can make anything look like anything (seriously - picking coordinates is a major part of advanced mechanics). In fact with clever manipulation of coordinate systems you can make the world revolve around yourself, but the paths of everything else would be really complicated and there'll be all sorts of inertial forces and stuff.
     
  16. Nov 5, 2012 #15

    A.T.

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    An fun example of this is a coordinate inversion on some sphere, the Earth for example. In this coordinates the outside and inside of the sphere are swapped. So we live on the inside of a spherical cavity that contains all the stars and galaxies. The laws of physics become very complicated when expressed in this coordinates, but there is no way to prove that the model is wrong, because it is not a theory that makes different predictions, just a weird coordinate choice.
     
  17. Nov 5, 2012 #16

    Drakkith

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    Nothing is known "for sure". It is impossible to 100% prove or disprove anything. In fact, science doesn't even "prove" things, it merely makes predictions based on models which come from theories. These predictions are either accurate to a certain amount or in certain circumstances or they are not. If they are not accurate, then the theory is considered "disproven", at least in it's current incarnation. But no matter how accurate a theories predictions are, a theory is never considered 100% "proven", only accepted.
     
  18. Nov 5, 2012 #17
    Does That mean we are not sure about every phenomenon in the universe?
    While we are walking its the earth sliding down our feet.Not we are moving.
    Different peoples different movements make the earth slide below our feet differently like earth is made of small pieces which can move independtly according to their will and laws of physics doesn't allow those pieces to separate by controlling our movements in a manner which we don't distinguish in our day to day lives.
     
  19. Nov 5, 2012 #18

    A.T.

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    Yes, you can describe the world from your rest frame, where the Earth is moving under your feet.

    No, in any frame there will be constraints how the earth's pieces can move, based on how the rest moves. Note that in your rest frame the other people also move differently than in the Earth’s frame.
     
  20. Nov 5, 2012 #19
    This thread smells of apologetics for false ideas that were eradicated 350 years ago and I won't have it. The reason why people could get the idea that the planets and the sun move around the earth is due to poor measurements. A periodic linear motion in the sky can usually be approximated by some kind of circular function. People could have realized that something is wrong when they noticed that planets sometimes move backwards through the heavens. Once you measure in three dimensions it is irrevocable that the planets move around the sun. This has nothing to do with physics, but simply with the laws of geometry, and we have measured the planets positions with incredible precision. As you might have noticed sometimes we get a better understanding of the laws of physics. For example the earth's orbit is not perfectly round, but an ellipsis with one focal point in the sun, and the other one close to it. Newtonian mechanics is almost perfect and can explain all of this. The only noticeable error that was left is the fact that mercury's ellipsis rotates with a speed of one revolution per 225000 years. This is a shift of 29 kilometers per year -- barely noticeable on planetary scales, ten percent of this could not be accounted for. This hole was fixed when GRT was found by Einstein, and of the ten percent error is an error of 0.02% left. So this is about 4 meters per year -- this is the maximum margin of error. Probably less these days. It is inconceivable that any physicist in the future will find that a rotation of the sun around the earth will be a better description of the system.
     
  21. Nov 5, 2012 #20

    A.T.

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    They did. And they developed complicated kinematic models to fit this observation.

    In don't see how 2D vs 3D is relevant here.

    I don't see why pure geometry should care what circles around what.

    A position always needs a reference coordinate system. Pure geometry doesn’t tell you where to put it.

    But that is physics, not just geometry. Newtonian mechanics is simpler than the old models and can explain much more. Therefore we use it.
     
    Last edited: Nov 5, 2012
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