On 30 June 1908
N.S. (cited as 17 June 1908
O.S. before the implementation of the
Soviet calendar in 1918), at around 7:17 AM local time,
Evenki natives and Russian settlers in the hills northwest of
Lake Baikal observed a bluish light, nearly as bright as the
Sun, moving across the sky and leaving a thin trail. Closer to the horizon, there was a flash producing a billowing cloud, followed by a pillar of fire that cast a red light on the landscape. The pillar split in two and faded, turning to black. About ten minutes later, there was a sound similar to artillery fire.
Eyewitnesses closer to the explosion reported that the source of the sound moved from the east to the north of them. The sounds were accompanied by a shock wave that knocked people off their feet and broke windows hundreds of kilometres away.
[2] The explosion registered at seismic stations across Eurasia, and air waves from the blast were detected in Germany, Denmark, Croatia, and the United Kingdom – and as far away as Batavia, Dutch East Indies, and Washington, D.C.[12] It is estimated that, in some places, the resulting shock wave was equivalent to an earthquake measuring 5.0 on the Richter magnitude scale.
[13] Over the next few days, night skies in Asia and Europe were aglow.
[14] There are contemporaneous reports of brightly lit photographs being successfully taken at midnight (without the aid of flashbulbs) in Sweden and Scotland.
[12] It has been theorized that this sustained glowing effect was due to light passing through high-altitude ice particles that had formed at extremely low temperatures as a result of the explosion – a phenomenon that decades later was reproduced by
Space Shuttles.
[15][16] In the United States, a
Smithsonian Astrophysical Observatory program at the
Mount Wilson Observatory in California observed a months-long decrease in
atmospheric transparency consistent with an increase in suspended dust particles.
[17] 
