A few friends have brought to my attention an article that was posted by Yahoo News about the ‘Supermoon’. They were asking what I thought about the possibility that because the March 19th Full Moon will be closer to the Earth than at any time during the past 18 years that we will see all sorts of natural disasters. Apparently, an Astrologer, Richard Nolle (who I have already just given more attention than he deserves) believes that the close proximity of the moon will cause the standard panoply of natural disasters – you know – volcanoes, earthquakes, etc. So what is going on? What is this all about?
Well, for starters, there will hardly be chaos outside of the chaos that already takes place in the world without a ‘Supermoon’. In fact, his statement is false on its face: Clearly the world experienced no major chaos due to the Moon 18 years ago when the Moon was closer than it will be Saturday. Nor do Astronomers recognize the term ‘Supermoon’.
What is true is that the Moon does revolve around the Earth in an elliptical orbit. The Moon typically gets as close to the Earth as 363,100 km (225,600 mi) and as far from it as 405,700 km (252,100 mi). The closest point in the orbit is called perigee while the most distant point is call apogee. These two words come from Greek. Gee refers to the Earth while peri- and apo- mean “near” and “far”, respectively.
The perigee and apogee distances that I mentioned above are not actually constant. All of the objects in the solar system are under the influence of the gravity from all of the other objects in the solar system. The Sun and Jupiter have the strongest gravitational fields in the solar system, and they pull and tug at all of the other objects the most. Meanwhile, all of the objects in the solar system are moving relative to one another. The net effect is that all orbits change slightly over time and it just happens that the Moon will be rather close this coming weekend.
Because the Moon is closer to the Earth at perigee, tides on the Earth are higher. This is because the force of gravity from the Moon is inversely proportional to the its distance, squared, and the Moon’s gravitational pull on Earth is a little more 20% stronger at perigee than it is at apogee. This has nothing to do with the Moon being either Full or New, however. Whether the Full Moon happens while the Moon is at perigee, apogee or at some other point in its orbit depends on the relative angle between the Sun, Earth and Moon – and that changes during the course of the year. Right now, during the Moon is near Full Phase when it is at perigee and by Fall, it will be Full right around apogee.
John Bellini, a geophysicist from the U.S. Geological Survey, mentions that even with the slight fluctuation in the gravitational force from the Moon as it revolves around the Earth, that there is little correlation between lunar perigee and earthquakes on the Earth. That is because the forces that cause plate tectonics are not driven by astronomical sources (and certainly not astrological sources!) – they are driven by currents in Earth’s mantle. There is, however, a noticeable difference in the heights of tides.
Now that you are relieved, I will mention that the Full Moon will look about 8% larger than average and it will look about 14% larger than when it is at Apogee Saturday night, so if the weather is permitting, go out and check it out. The Moon will rise around 7:30pm and it will be high in the sky by midnight or 1am on the 20th, so go out and have a look – it will be pretty!