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Tidal lock due to rotation of displaced mass

  1. Jan 19, 2012 #1
    As I understand it, the rate of rotation of a body is slowed as a consequence of the grater gravitational attraction on the mass displaced by tidal forces as this displacement is pulled forward by the effected bodies rotation thus acting to provide a counter rotational force until tidal lock is achieved.

    If this is correct it implies that an ideal rigid body would be immune to the slowing of its rotation due to tidal forces.

    Has my understanding lead me astray from the actual mechanics involved in achieving tidal lock?
  2. jcsd
  3. Jan 19, 2012 #2
    For the most part you are correct.
    Tidal forces, in general, can both slow down or speed up the rotation of a body. Additionally, while the tidal 'distortion' can increase the effects of tidal interactions, its the general asymmetry which is required. In practice the asymmetry is introduced by deformations/distortions, but an oblong object (like an asteroid) would still feel tidal torques even if perfectly rigid.
    An important aspect, however, is dissipation---tidal locking (usually) requires the dissipation of spin angular momentum of the orbiting body, and this usually happens from deformations. Thus a perfectly rigid body, and especially a symmetric one, is generally not going to be effected much by tidal torque.
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