The longest solar eclipse of the 21st century covered much of Asia in near darkness on Wednesday morning [Reuters] An eclipse is caused when the Moon covers the Sun completely to cast a shadow on Earth [Reuters] At its peak, the eclipse lasted six minutes and 39 seconds [Reuters] The eclipse was visible only in Asia, including in India, Nepal, Myanmar, Bangladesh, Bhutan and China [Reuters] It is the longest such eclipse since 1991, when a total eclipse lasting six minutes and 53 seconds was visible from Hawaii to South America [Reuters] Millions across Asia gathered to watch the phenomenon [Reuters] Wednesday's eclipse may end up being the most watched in history due to its path over the world's most densely populated areas [AFP]