Herds of reindeer were incinerated as they stampeded away from the explosion, and all wildlife in the area was ignited by the searing heat blast. Thirty-seven miles from the blast, the tents that the frightened Evenki people had taken refuge in were lifted high into the air by the resulting atmospheric shock wave, and the Evenki's horses galloped off in terror, dragging their ploughs with them.

At the centre of the explosion a monstrous mushroom cloud rose steadily over Siberia. Such a strange and unsettling sight would not be witnessed for another thirty-seven years at Hiroshima and Nagasaki. But this explosion was even fiercer than the A bombs which were dropped on the Japanese cities. The blast from the Tunguska explosion felled trees as if they were matchsticks for 20 miles around and set whole forests alight.

The shockwave generated by the mysterious cataclysm travelled around the world twice and shook the recording pens of the microbargraphs at three meteorlogical stations in London, where they were interpreted as seismic jolts from some distant earthquake.

mushroom cloud

At a distance of 400 miles from the epicentre of the Tunguska blast, the relentless shockwave showed no signs of abating, and knocked fishermen from their boats on the River Kan. By the time the blast had deteriorated into a hurricane-like storm, a strange black rain started to fall over the Tunguska valley. Days later, strange scabs started to break out on animals that had been too far away to be directly burnt by the blast, and weeks later, curious investigators who ventured to the site of the explosion became sick and complained of strange burning sensations within their bodies. Were these signs of radiation sickness?

But what meteoric object could be radioactive? Stranger still, why was there no crater at the site of the explosion? All meteorites leave a crater. And how would a meteorite travel horizontally for hundreds of miles and change course twice? Then there were other strange occurrences which seemed to suggest that the object which had exploded over Siberia was not a meteor at all, but perhaps some nuclear-powered spacecraft from another world which had had made an emergency crash-landing in a forbidding area of our world.

The first reports of a strange glow in the sky came from across Europe. Shortly after midnight on 1 July 1908, Londoners were intrigued to see a pink phosphorescent night sky over the capital. People who had retired awoke confused as the strange pink glow shone into their bedrooms. The same ruddy luminescence was reported over Belgium.

The skies over Germany were curiously said to be bright green, while the heavens over Scotland were of an incredible intense whiteness which tricked the wildlife into believing it was dawn. Birdsong started and cocks crowed - at two o'clock in the morning. The skies over Moscow were so bright, photographs were taken of the streets without using a magnesium flash. A captain on a ship on the River Volga said he could see vessels on the river two miles away by the uncanny astral light.

One golf game in England almost went on until four in the morning under the nocturnal glow, and in the following week The Times of London was inundated with letters from readers from all over the United Kingdom to report the curious 'false dawn'. A woman in Huntingdon wrote that she had been able to read a book in her bedroom solely by the peculiar rosy light. There were hundreds of letters from people reporting identical lighting conditions that went on for weeks after the Tunguska explosion.