Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Could gravity affect human evolution?

  1. Jul 17, 2011 #1
    I am wondering if millions of years from now if the Earth and Moon became a true double planetary system, where one side of each body continually face eachother, if it could have affects on the height of humans. If people living on the "lunar side" would be taller on average than people on the opposite side of Earth because of the extra permanent affects of the Moons gravity?
  2. jcsd
  3. Jul 17, 2011 #2
    I'm not sure that locking the orbits would make the Earth-Moon system a "true double planetary system", but I could me mistaken about some definition involved.

    That aside, I don't think you would get the gravitation affect you describe any more than we currently would with a full Moon directly overhead or directly beneath our feet. You are in free fall (and therefor weightless) with respect to the Moon.
  4. Jul 18, 2011 #3


    User Avatar
    Staff Emeritus
    Science Advisor

    If this were to happen it wouldn't be a product of evolution, biological evolution refers to inheritable traits with variation under environmental attrition. I'm not sure how to work it out but I suppose the lunar side would have slightly weaker gravity than the other side.

    However how long away is this event? I doubt homo sapiens will be here in millions of years (some of our descendants might but that's another discussion)
  5. Jul 18, 2011 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    A couple of points.
    It would take billions, not millions of years for this to happen.
    Our Sun will expand into a red giant before it can happen.
    The Moon would have to be further away from the Earth when it happens, lessening its gravitational effect on the Earth from what its now.
    The gravitational effect that we do feel on the Surface of the Earth is due to tidal effects, which actually pull outward on both the Lunar side and Anti-lunar side. (this is why we get two high tides a day.)
    Even today, this tidal pull is very weak. The difference in the weight of your body with it and without it works out to something like 1/50th of an ounce. Maintaining a short haircut would have more effect on your on your weight. So, no, you would not expect to see any difference in height in people depending on where they live.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook