Smart people only. When is lunar gravity greatest on earth?

OK, I'm a bit of a numbers geek and like to research ideas. On TV, I heard this theory by a geologist (James Berkland) who claims, when there was a "new moon at perigee" that he believed there was a higher incidence of earthquakes due to the sun and moons combined gravitational pull on tectonic plates (I'm not knowlegable about astronomy). It seemed like a good theory, but it also seems too obvious, like others would have thought of that before, but I thought it would be fun to look at some data (I'm a bit of a geek).

I looked up the new moon calander and the perigee (not apogee) calander and got them in a spread sheet and found the dates where they closely matched up for 2007. But, I found no strong correlation between 2007 earhquakes and these dates. So I was wondering if there is some convenient table of lunar and solar gravitational pull and when it was the absolute strongest during the past few years (or any time frame you can point me too).


good thought quackpot, I started looking at high tides, but don't understand the time delay between maximum gravity force and movement of water.

6 Answers

  • Anonymous
    1 decade ago
    Favorite Answer

    Perigee has nothing to do with the tides. The Moon orbits in a slight ellipse, with the point of perigee and apogee at the ends of the long axis, and the Earth at the focus closest to perigee. The orientation of the long axis is not constant, and in fact precesses, so that it is constantly pointing in a different (but predictable) direction.

    In answer to your question, the end result of the earth's revolution around the sun means that every 7.5 synodic months (which is 29.5 days, the length of a lunar phase cycle), there is a "perigean tide," where perigee coincides with a spring tide (where the moon, sun and earth are in syzygy, which is perhaps my favorite word!). That means the gravitational tides are strongest at those times.

    I have heard of the perigee theory about earthquakes, but if I remember correctly, the geologist in question did not do a study or survey of earthquake rates, which you are intrepidly doing. Rather, he was attempting to use the perigean tides to PREDICT earthquakes, and had done so in some major newspapers.

    Of course, what any reputable geologist will tell you is that if you take any time frame and predict that a major earthquake will occur, you will be right because major earthquakes are constantly occurring and recorded by the thousands of seismograph stations around the world. In fact, there has been no convincing evidence that the perigean tides have any significant effect on the earthquake rate on a day-to-day basis, so these claims are, more likely than not, just a bunch of hooey.

    incidentally, here's a perigee/apogee and tide calculator site:

  • 1 decade ago

    My friend, the delay between maximum gravity force and movement of water is due to friction within the water masses and the ocean floor.

    The maximum force of the moon upon earth is at its perigee because it is closest to earth. The combined lunar-solar force is greatest when at full moon or new moon because of the alignment of the Sun and the Moon. I suppose that when both sun and moon are at the perigee AND there is a full or a new moon the effect is maximised.

    As for earthquakes I am not an expert but I think that there is no correlation with astronomical events.

    Hope I have helped

  • 1 decade ago

    The lunar gravitational pull is the strongest on the 12th 13th and 14th of moon (full moon). During these nights, the waves of the oceans, the so called high tides, come deeper into inner land.

    On these nights the stronger gravity not only had effect on material nature (sea waves etc) but it also effects the human behaviour.

    The witchkraft, black magic, Condomble and some of the indian rituals have the maximum effect on these nights. The older civilization used to sacrifice human beings on these nights. The Kali Devi of Indian mythology was the bloodthirstiest on these nights

    Remember the story of were-wolfs, hound dogs and draculas etc all have something to do with moon exercising its maximum gravitation pull.

    In 2006, it was not only the coordinated effect of full moon and sun, but planet mars was also the nearest to earth after along time. It also exerted its gravitational pull.

    The trianglular effect of martian, lunar and solar gravitational and magnetic forces created the possible devastating effects.

    These triangular forces were further supplemented by the underground nuclear tests by certain unknown country, which possibly is the reason of Devastating effect at Tsunami.

    All of these forces are being complemented by the vacuum or big holes ctreated by the

    oil, gas nd mineral extraction from the earth.

    The force-vectors of natural forces and humanly created forces produced,at a particular time, a linear resultant vector of immense magnitude, which disturbed the harmony of existing balances and caused the disturbace in form of tsunami,tidal waves, eartquakes,storms etc

    Not to forget the prophecy that before the arrival of THE SAVIOUR their will be disturbances of higher magnitude earthquakes, floods, storms, bloodshed etc etcforcescame together at a certain moment

  • 1 decade ago

    I would believe that at this stage of the earth's evolution that everything has settled to a point that the impact would be minimal. Think of it as continually dropping a ten pound weight at the same spot of ground. Eventually the soil will compact to a density equal to the force of the impact. Since the cycles of lunar and solar gravity have been fairly constant for a few million years, I would think the earth has reached a point where the effect is negligible on tectonic level otherwise we would be having massive earthquakes at a fairly regular basis at roughly the same time in the lunar cycle.

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  • 1 decade ago

    Perigee is when the moon is at its closest to the earth, and distance is a determinate for gravitational force (the closer you are, the more gravitation force there is). Perigee at new moon means the gravitation force is also in the same direction as the sun. But gravitation force is so weak, I doubt there are higher incidents of earthquakes...

  • 1 decade ago

    Supposedly lunar gravity is greatest at the equator so you'll be a few pounds lighter. My guess is to stand in somewhere along that equator during a full moon that is directly above you.

  • ?
    Lv 7
    1 decade ago

    On a full moon day when moon is just rising.

  • 1 decade ago

    high tides

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