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I Earth's rotation and tilt

  1. Nov 1, 2016 #1


    Staff: Mentor

    That raised an interesting question in my mind. Wikipedia was not helpful providing answers.

    Surely we must have estimates of Earth rotation rate and tilt both pre and post impact with Theia. What are those numbers?
    Last edited by a moderator: May 8, 2017
  2. jcsd
  3. Nov 1, 2016 #2


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    Staff: Mentor

    I'm not sure, but have you searched on the NASA pages? And it's more than two numbers, because the moon is gradually moving away from us, so it's rather a function of time.
  4. Nov 2, 2016 #3
    According to a 2013 simulation, the Earth's rotation rate immediately after the Theia impact was 3.795 ± 0.405 hours. With Earth's axial tilt of 23.3° ± 1.2°. The moon's orbit about the Earth initially took 18.15 ± 0.24 hours, with an initial distance of 43,807.6 ± 416.4 km (just outside Earth's Roche Limit), with an eccentricity of 0.0775 ± 0.0005.

    However, http://www.nature.com/nature/journal/vaop/ncurrent/pdf/nature19846.pdf, is suggesting a much faster rotation rate for Earth at ~2 hours immediately after the Theia impact, and that Earth's axial tilt was between 70° and 75° at the time of the impact.

    As far as I was able to find, nobody knows what the orbital rate of Earth prior to Theia's impact might have been.

    http://www.nature.com/nature/journal/vaop/ncurrent/pdf/nature19846.pdf - Nature, October 31, 2016, doi: 10.1038/nature19846
    Tidal Evolution of the Moon from a Fast-Spinning High-Obliquity Earth - 47th Lunar & Planetary Science Conference (2016) [PDF]
    N-Body Simulation of the Formation of the Earth-Moon System from a Single Giant Impact - arXiv 1307.7062
    Last edited by a moderator: May 8, 2017
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