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Gravity and fishing line.

  1. Feb 12, 2007 #1
    While introducing the equivalence principle in "The Meaning of Relativity" (6th ed. 1954, p.59), Einstein considered how special relativity requires that circular motion distort the ratio (pi) between the measured diameter and perimeter of a rotating circle, compared with its value in a non-rotating frame. He pointed out that the equivalence principle (which says that an accelerated frame with no gravitational field is equivalent to a non-accelerated frame with a gravitational field) then requires that "the gravitational field influences and even determines the metrical laws of the space-time continuum".

    This (as I see it, faultless) reasoning can be extended to argue that the earth's orbit in the sun's gravitational field is a geodesic trajectory through a (slightly) curved space-time.

    But suppose (very hypothetically) that instead the earth moved along its orbit while tethered to a fixed point (substituted for the sun) by a length of (very) strong fishing line.

    Would one then be justified in arguing that the fishing line, by virtue of its electromagnetic-based cohesion, "influences and even determines the metrical laws of the space-time continuum" ?

    And if not, why not?
  2. jcsd
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