The detonation took place in such a remote area of northern Siberia that it was not noticed internationally (or indeed outside the immediate area it occurred in) at the time that it took place. Although it's now estimated that the incident produced almost 200 times more energy than the Hiroshima atomic bomb, and flattened 80 million trees over 830 square miles of taiga, human casualties, if any, would have been limited to small groups of nomadic reindeer-hunters, and the first Russian expedition to the area did not take place until 1927. What was noticed at the time was the seismographic and atmospheric phenomena associated with the explosion.
Moving progressively away from the site of the blast, we have evidence from a farmer sitting on his porch around 40 miles away, who reported "a great flash of light. There was so much heat that I was not able to remain where I was - my shirt was almost burned off my back. I saw a huge fireball that covered an enormous part of the sky... Afterwards it became dark and at the same time I felt an explosion that three me several feet from the porch. I lost consciousness for a few moments, and when I came to I heard a noise that shook the whole house and nearly moved it off its foundations." Windows were smashed in a town a similar distance away. A witness described seeing "the sky split in two, and high above the forest the whole northern part of the sky appeared covered with fire." This sight was accompanied by "a bang in the sky and a mighty crash... followed by a noise like stones falling from the sky, or guns firing."
A 1939 British newspaper report added that "a luminous silvery vapour, formed at the height of some 50 miles... illuminated a great part of Russia. The glow was visible at almost any point in Siberia, and was even seen as far away as the Caucasus."
In Britain, a reader wrote to The Times to enquire why the night sky had suddenly become so bright, and seismographs recorded what was assumed to be a distant earthquake. A 1991 report in The Guardian suggests, perhaps apocryphally, that it was light enough in Scotland in the aftermath of the detonation for someone to play a round of golf on the famous golf course at St Andrews at 2.30am.
