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

The moon.

  1. Jun 10, 2003 #1
    The research says that the moon is getting away from the earth a few cm yearly, what will happen to the earth if we completely lose the moon?[?]
  2. jcsd
  3. Jun 10, 2003 #2


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    A slightly different question is
    would multicell life have evolved on the earth if
    it wasnt essentially part of a double-planet system

    People might possibly dismiss Saint's question because
    it will take a very very long time for the moon to get significantly farther away and life has already evolved here and if it survives its own vices and stuff it can certainly survive losing the moon but that is so far in the future it .....well

    But suppose in another galaxy there was a star like the sun that had a planet like the earth with lots of good water and atmosphere and stuff----only this earth did not have a moon.

    Would this be as hospitable to life?

    Would, for example, that earth's axis be as stable as ours has been. Or would it wobble all around and wreck evolution by
    huge swings in climate?

    Are tides important to evolution. I dont have any idea myself but maybe somebody does. Anyway to me it seems like an interesting thing to ask. How might things have gone for us if the earth had not had its moon.

    Important fact-----the moon is 1/80 of the mass of the earth.

    Compared with that (a moon over 1 percent of your mass) Mars has zilch moon. Jupiter has zilch moons. Saturn's moons are negligible compared with the planet's mass. But Earth-Moon is, in a very real sense, a double planet.
  4. Jun 10, 2003 #3
    Uh, no more eclipses? Hmm?
    No more seeing craters with my 35 year old 30X Tasco zoom telescope. or with Mount Polamar's 200 incher.

    No more place for lunar landers to land.
    No more lunar rocks to be brought back only to be stolen and offered for sale at outrageous prices on e-bay.

    No more speculation whether life exists on the moon.
    No more odd ball stories in Popular Mechanic's magazine about how we plan to colonize the moon in the next ten years.

    No more worry about having to wait for darkness of 'new moon' before bombing the crup out of Iraq (or any other 'evil' dictator).

    Best of all : No more lunar light pollution plaguing deep sky observation and astrophotography.

    Yep, it going to be a boring place to live.

    Last edited: Jun 10, 2003
  5. Jun 10, 2003 #4
    Re: Re: The moon.

    very much so. several (hundreds or more) species are dependant on the motion of the tides for movement and food regulation and hundreds more are dependant on those creatures and so on and so on. it's the old web of life.
  6. Jun 10, 2003 #5
    If we had no moon, would our earth be much scorched?

    As for other things, I believe the earth would spin faster, it wouldn't be in the same stable orbit, as for where it would go, I don't know.

    Rotating faster would cause huge storm systems and high winds.

    That's all I have to add
  7. Jun 10, 2003 #6

    i don't know if this is true. the earth is rotation very rapidly as it is, and our winds have little or no connection to this effect. but you are right, our orbit would change dramatically.
  8. Jun 10, 2003 #7
    Hm...Jupiter rotates much faster, and very stormy weather, I was simply applying the same uneducated guess to the earth. I don't care much for thinking of "what-ifs" so I have not researched this subject, although I do know that Discovery had a show a long while back on this, and there is a book on it.

    The wind comes from the air between pressure systems, I guess. Would the absense of the moon cause fewer clouds to form, as the majority of the water would be sitting still?
  9. Jun 10, 2003 #8

    i also don't know to much on the subject, but i bet there are other reasons to describe the weather of jupiter.

    this seems more plausable, but like i said, i'm no meteoroligist. i pupose water would still evaporate and form clouds, but the clouds might not move as much.
  10. Jun 10, 2003 #9


    User Avatar

    Staff: Mentor

    Losing the moon will not cause in increase in the rotation rate - but it will cause a DECREASE in the rate the earth's rotation slows due to tidal friction.
  11. Jun 10, 2003 #10


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    Last edited by a moderator: Apr 20, 2017
  12. Jun 11, 2003 #11


    User Avatar
    Science Advisor
    Gold Member
    Dearly Missed

    this is a pretty nice fact----here's what it says at Phobos' link:

    [[Is the Moon moving away from the Earth?

    Yes it is, but very slowly. The current rate at which the Earth day is increasing is 0.0018 seconds/century. The semi-major axis of the lunar orbit is increasing by 3.8 centimeters/year according to laser ranging measurements made since the 1970's using the Apollo 'corner cube reflectors' deposited on the surface by the astronauts. It is expected that in 15 billion years, the orbit will stabilize at 1.6 times its present size, and the Earth day will be 55 days long equal to the time it will take the Moon to orbit the Earth. Of course, in less than 6 billion years, the Sun will have evolved into a red giant star and engulfed the Earth-Moon system, thereby incinerating it!]]

    Executive summary: the moon will keep moving away until the sun goes red giant. (After that doesnt seem to matter)

    This is interesting partly because it illustrates something about the transfer of angular momentum by tides. Tides slow down the rotation of the earth and pump angular momentum into the moon's orbit. As long as the day is shorter than the month----that is, as long as the earth's turning is faster than the moon's revolving----the tide mechanism gradually bleeds angular momentum out of the more rapid rotation and transfers it into the moon's orbit. This transfer of angular momentum swings the moon farther and farther out.

    But (Phobos' link indicates) the transfer is so slow that it would not be finished for 15 billion years even if allowed to continue uninterrupted!---and long before then (namely by 6 billion years) the sun will
    go red giant.

    Apologies for my earlier post turning out to be off topic! I didnt mean to hijack but to add a dimension to the discussion namely what practical stuff does the moon do for us (besides look beautiful all the time.)
    Last edited by a moderator: Apr 20, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook