Society

Experts tame worries over 'supermoon'

By Chen Xin (China Daily)
Updated: 2011-03-16 08:17

BEIJING - Astronomers have refuted rumors that the devastating earthquake and ensuing tsunami in Japan were closely related to or even caused by the "supermoon" that will appear in the sky on Saturday.

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The word "supermoon" was introduced in a report by the British newspaper Daily Mail on March 9, which said amateur scientists were warning that such an astronomical phenomenon could disrupt the Earth's climate patterns and may even cause earthquakes and volcanic activity.

The moon will be 356,577 kilometers from the Earth on Saturday, the closest in 19 years, and the closest point in its oval orbit coincides with a full moon, the report said.

However, Saturday's moon is not actually the closest to Earth in 19 years, Tang Haiming, an astronomer with Shanghai Astronomical Observatory under the Chinese Academy of Sciences, told Xinhua News Agency. A shorter distance of 356,570 km between the two bodies was reached in January 2005, and a distance of 356,566 km was seen in December 2008.

Yet some people suggest that previous supermoons have occurred prior to extreme weather events.

In 1974 the phenomenon was followed by Cyclone Tracy in Darwin, Australia, and in 2005 it occurred shortly before a deadly tsunami in Indonesia.

Coincidentally, two fresh disasters happened in Asia right before Saturday's supermoon.

The public's concern about their connection with the moon boomed after Japan's devastating earthquake and tsunami and a tremor in Southwest China's Yunnan province that killed 25 people on March 10.

But astronomers are trying to reassure people that such rumors are merely groundless.

"A supermoon could cause high tides but has no direct relation with natural disasters such as earthquakes," Liu Jie, a researcher with the China Earthquake Network Center, told China Daily on Tuesday.

"We can't find any necessary connection between previous supermoons and earthquakes. And the quake in Japan occurred because the Earth's internal energy had accumulated to some extent, and it's not related to the moon," he said.

James Garvin, chief scientist at the Goddard Space Flight Center under NASA, said in an article on NASA's website that "the effects on Earth from a supermoon are minor."

"The combination of the moon being at its closest to Earth in its orbit, and being in its 'full moon' configuration (relative to the Earth and sun), should not affect the internal energy balance of the Earth, since there are lunar tides every day.

"The Earth has stored a tremendous amount of internal energy within its thin outer shell or crust, and the small differences in the tidal forces exerted by the moon (and sun) are not enough to fundamentally overcome the much larger forces within the planet due to convection," he said.

Zhu Jin, curator of the Beijing Planetarium, said there is no scientific term for "supermoon", but the moon moves around the earth in an elliptical path, so each orbit has a perigee - its closest approach, and an apogee - its furthest distance.

A lunar perigee occurs once a month and there are very small differences in distances between perigees, he said.

Those tiny differences are far from enough to cause earthquakes or eruption of a volcano, he added.

On average, at perigee the moon is as close as 363,300 km and at apogee it gets 405,500 km away, astronomers say.

Wang Qian contributed to this story.