March 19: Is ‘super moon’ a myth or science?

On March 19, 2011, the moon will be 3,56,577km away from the earth, its closest in 18 years. The average distance of a normal lunar perigee (moon's closest point to earth) is 364,397 kilometers. In other words, compared to its distance on other lunar perigees, the moon will be 7,600 kilometers closer to the earth on March 19. Moreover, the moon will appear about 14% larger than normal in size when the full moon rises in the sky. It is because of its large size that it is called the 'Super Moon'.

Though Super Moons are natural phenomenon, many people, including astrologers, link their occurrence to natural disasters such as earthquakes, tsunami and hurricanes. The recent quake in Japan that was followed by a powerful tsunami has once again sparked a debate on the role of the 'Super Moon' in causing disasters. To find out more about the celestial phenomenon, DNA spoke to Dr Narendra Bhandari, who was Senior Professor at Physical Research Laboratory in Ahmedabad for almost 40 years.

He is currently Honorary Scientist of INSA, Delhi.

Bhandari said that a Super Moon alone cannot cause disasters on earth. He said that the moon exercises a gravitation pull on the waters of the ocean which cause high tides every day. Lunar gravity also causes changes in atmospheric pressure. "But that is about all that can be said about the visible effects of the moon on earth," he said.

In addition, the Super Moon can exercise a minor gravitational pull on the molten lava beneath the earth's crust but it does not have the energy to cause volcanic eruptions, Bhandari said. Similarly, the moon cannot cause tsunamis on earth but can increase the height of tidal waves if a tsunami were to occur when the moon is at its closest to earth. "A tsunami which occurs during Super Moon can have higher waves and cause more damage," the scientist said.

Bhandari further said that geological events like earthquakes and volcanic eruptions occur because of the energy within the earth and are not caused by any outside agency. He explained that the earth's crust is formed of nine tectonic plates which move against each other, collide and, in areas of collision, cause stress to build up over the years.

Earthquakes occur when this accumulated stress overwhelms the rocks which collapse under pressure and re-adjust, thereby causing quakes on earth. If the rocks under stress are already at a point of collapse, then any small event can trigger a quake, he said. In such a situation, it is possible for a Super Moon's gravity to provide a trigger for quakes or for some event which has attained a critical point, Bhandari added.