(CNN) -- Skywatchers are gathering from parking lots in western India to music festivals on remote Japanese islands to witness what NASA describes as an "exceptionally long" total solar eclipse that will cross half the planet on Wednesday.



People try out "solar view goggles" ahead of the eclipse on the outskirts of Ahmedabad, India.



"This eclipse has the potential to be observed by more people than any eclipse in all of history," said MIT astronomer Richard Binzel, who will be in Shanghai leading an expedition of observers and a group of eclipse chasers.   "Essentially, every inhabitant of all of India and China will be able to see at least part of the sun covered throughout the day," he said.



The path of the total eclipse will stretch across the heart of Asia -- from India's Bay of Cambay, over the Himalayas and across China and the southern islands of Japan.



The eclipse is expected to reach its peak over India at around 12:40 a.m. GMT Wednesday (8:40 p.m. ET Tuesday).



Though the duration of greatest eclipse will occur over the Pacific Ocean at six minutes, 39 seconds, people in some areas of China and Japan will experience up to more than six minutes of darkness, according to predictions by Fred Espenak of NASA's Goddard Space Flight Center and J. Anderson of the Royal Astronomical Society of Canada.  Watch as eclipse-watchers head to China »



The 15,150-kilometer (9,415-mile) journey of the moon's shadow across the Earth will last nearly three-and-a-half hours and be "one of the longest eclipses, if not the longest eclipse, in this century," Binzel said.



Forecasters predict stormy weather for Wednesday morning in Shanghai, but this prognosis has not deterred astronomers and tourists from flooding the city. Send us your photos of the eclipse



Professor Zhao Junliang of the Shanghai Astronomical Observatory said the weather could be unpredictable but staying away from such an historic event would be a mistake.



"In 1987, I chased a total solar eclipse in (the western region of) Xinjiang. At the time, the sun was entirely blocked by stormy clouds. Two minutes before the eclipse began, the clouds suddenly cleared," Zhao said. "You just never know, so you have to go." Read blog on how eclipse-chasers are gambling on weather



Rick Gille and his wife flew in from Atlanta, Georgia, to catch the eclipse in Shanghai. They were heading to what is known as the "centerline" -- where the eclipse will last nearly six minutes.



They are armed with high resolution digital cameras and telescopes. "You'll know us when you see us," said Gille, who travels the world chasing solar eclipses. "We're all wearing beige t-shirts which read 'Eclipse 2009.'"



Total eclipses happen about once a year or a little less often somewhere on the Earth's surface and are visible in a narrow band, Benzil said.



"This band starts at sunrise in India and ends at sunset over the Pacific, just east of Hawaii about four hours later. The shadow path of the moon is sweeping across the surface of the Earth at about 3,000 kilometers per hour," he said. "The partial eclipse is also visible throughout Thailand and Vietnam, as far south at the top tip of Australia and as far north as Siberia."



In some cultures, legends and folklore surrounds eclipses.



In India, an eclipse is considered inauspicious. Women forbid pregnant daughters-in-law from going outside out of the belief that their children could be born with marks. Some temples won't offer any prayers on the day of an eclipse -- such as the one next to the planetarium in Mumbai, which said it won't even light a stick of incense.



In Chinese tradition, there is a story about a heavenly dog eating the sun. As the story goes, people would make noise to scare off the dog and rescue the sun, said Bill Yeung, president of the Hong Kong Astronomical Society.



"In ancient China, we shared the same impression with
What does the MIT astronomer say? is any special equipment needed to see it? What does NASA say? What will strecth across the heart of Asia? What was exceptionally long? Where can people see the eclipse? when will it happen? What kind of events people watch the eclipse?
"This eclipse has the potential to be observed by more people than any eclipse in all of history," "solar view goggles" an "exceptionally long" total solar eclipse that will cross half the planet on Wednesday. The path of the total eclipse total solar eclipse from India's Bay of Cambay, over the Himalayas and across China and the southern islands of Japan. 12:40 a.m. GMT Wednesday (8:40 p.m. ET Tuesday). chasers.
question: What does the MIT astronomer say?, answer: "This eclipse has the potential to be observed by more people than any eclipse in all of history," | question: is any special equipment needed to see it?, answer: "solar view goggles" | question: What does NASA say?, answer: an "exceptionally long" total solar eclipse that will cross half the planet on Wednesday. | question: What will strecth across the heart of Asia?, answer: The path of the total eclipse | question: What was exceptionally long?, answer: total solar eclipse | question: Where can people see the eclipse?, answer: from India's Bay of Cambay, over the Himalayas and across China and the southern islands of Japan. | question: when will it happen?, answer: 12:40 a.m. GMT Wednesday (8:40 p.m. ET Tuesday). | question: What kind of events people watch the eclipse?, answer: chasers.