Total solar eclipse is to visit China on July 22, and it will last for more than two hours, scientists here said. The eclipse would begin at about 8 a.m., and people in the middle and lower reaches of the Yangtze River would observe the longest total solar eclipse in this century.
Then, what are major hallmarks of the upcoming total solar eclipse, where is the best place to observe it, and what particular heed should people give to their conduct while observing the solar eclipse?
All these questions were asked and answered a joint press conference held on Tuesday, May 19 in the National Astronomical Observatory of the Chinese Academy of Sciences (CAS) in the national capital of Beijing.
China is the best place in the world to observe the forthcoming "great eclipse", said Jiang Xiezhu, a spokesman for the CAS General Office, who is also director of the office, at the joint press conference, and the length of the total eclipse of the sun will run for up to six minutes within the country's territories.
The width of the track of a central eclipse varies according to the relative apparent diameters of the Sun and the Moon. As the upcoming total eclipse occurs very close to perigee, the track in China can be more than 250 km with from the west to the east. The path of the moon's umbral shadow would begin in India, and cross Nepal, Bangladesh, Bhutan, and Myanmar, before it covers China's southern Tibet Autonomous Region, Central Sichuan province, southern Hubei, Henan, Anhui and Jiangsu provinces, northern Zhejiang province and Shanghai municipality, where more than 300 million people would likely witness the eclipse.
In a total solar eclipse, the sun, the moon and the Earth are directly aligned as the sun swings into the cone of shadow cast by the moon. Total solar eclipses are very rare events, said Professor Zhao Gang, deputy director of the CAS National Astronomical Observatories.
Although they occur somewhere on earth approximately every 18 months, Zhao explained, it has been estimated that they recur at any given place only once every 370 years, on average… and the two eclipses will thus not be visible from the same place on earth.
Besides, total solar eclipses used to cross mostly sparsely-populated, secluded or inconveniently-located areas of the Arctic, Russia and China. So the occurrence of the "great eclipse" in the middle and lower reaches of the Yangtze valley is extremely rare. "Some people would consider it most fortunate to see the 'great eclipse' in their life," said Prof. Zhao.
During the total solar (great) eclipse, Chinese scientists would study the sun's chromosphere and corona, and the gravity variations of the solar system planets, said Li Ding, director of the Bureau of Basic Sciences of the CAS, at the press conference.
Observers on the Earth will see the intensely-bright disk of the sun replaced by the dark silhouette of the moon, surrounded by a much fainter corona. So, eye protection is necessary when viewing a solar eclipse. At some given phases of the solar eclipse, people might harm their eyesight if they do not resort to the scientific observation methods, Prof. Zhao admonished. People cannot observe the total solar eclipse with their naked eyes or by means of telescopes without light-baffling gears and, otherwise, it could cause retinal damage as the sunlight is a million-fold stronger than the moonlight.
Since the solar eclipse is so popular and to facilitate or acquaint people with it, said Liu Xiaoqun, deputy director of the National Astronomical Observatories, the Chinese Astronomical Society and the National Astronomical Observatories would arrange a series of eclipse observation and popular science activities through their cooperative efforts with eight cities along the central path of the 2009 total solar eclipse, including Tongling, Tongcheng, Jiaxing, Suzhou, Changzhou and Wuxi.
A five-or-six-minute abrupt "blackout" can possibly inflict hidden dangers on road transport, shipping, air travel and outdoor, open-field operation and even possible hazards in the spheres of building construction, medical service, teaching and business activities, and social security, said Yan Jun, director of the National Astronomical Observatories. It could also produce a likely undefined impact upon the optical telecom system, integrated telecom web services and power transmission due to sudden changes in astronomic gravity and light intensity.
With the absence of emergency measures, grave misfortunes and catastrophes could possibly occur, Yan acknowledged, and he urged government institutions to confer with relevant experts for working out viable plans to guard against and prevent any consequences that could arise from this rare total solar eclipse.
By People's Daily Online and contributed PD reporter Zhao Yongxin