Between 6 and 9 p.m. on the full moon night of the eleventh lunar month (October), the final night of Buddhist Lent, smokeless, scentless, soundless fireballs begin to rise from the deep of the Mekong River up into the air. This year it will happen on the 26 and 27 October.
For centuries the fireballs were kept a closely guarded secret amongst the villagers, but now thousands of locals, tourists and skeptics gather to watch this phenomenon on the remote border between Thailand and Laos.
One theory is that fermentation of sediment in the river causes methane and nitrogen to ignite into the spectacular display. Investigations by the Thai Ministry of Science and Technology in 2002 seem to favour this theory. However, they do not explain how sediments form in the fast moving water.
Northern Thais have no doubt it is the work of Naga, the serpent of Buddhist lore that haunts the northern reaches of the Mekong. ‘Sightings’ of an eight-meter long, crested silvery eel-like fish are often reported at this time and are the subject of the usual grainy photographs which generate so much controversy.