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Space-Time Dilemma

  1. Jun 24, 2011 #1
    Hi there

    I understand the general idea about the Theory of Relativity and the idea of a 4 dimensional space-time fabric, how the sun ( a mass ) sits on the fabric and creates a well on which the planets sit and therefore orbit the sun due to gravity. But how does one explain the case of Eris, who's orbit is around the sun as well, yet completely off this so called plane. How can, say, Earth and Eris exist at the same time, each moving across this fabric while orbiting the sun? If you visualise this space-time fabric from the point of someone watching both Eris and the Earth orbiting the Sun, how would the fabric look like? Theoretically wouldn't the well that the Sun creates in this fabric push the Sun closer to Earth? Does Eris's elliptical orbit contribute in any way?

    To incorporate both orbits at the same time wouldn't this imply that it has to be bent so that the Earth orbits the Sun but at the same time Eris orbits it. This seems a bit strange to comprehend, maybe I'm thinking of it incorrectly but could anyone answer this?
  2. jcsd
  3. Jun 24, 2011 #2


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    The idea of a bent fabric is just an analogy to help you understand - it should not be taken too literally. In fact, it is the four-dimensional space-time 'fabric' which is distorted by the mass of the sun. Since the sun is spherically symmetric, this distortion is spherically symmetric as well, meaning the distortion is the same at any distance from the sun, regardless of the direction. So an orbit around the sun can be in any plane, and multiple bodies can orbit in different planes, as is the case with Earth and Eris. I know it is hard to visualize - try studying the mathematics of general relativity and I think you will understand better.
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