“On the morning of June the 30th 1908 something came hurtling out of the sky. An enormous ball of fire which exploded above the Siberian forest with a sound that was heard a thousand miles away and a blast that laid waste the trees over an area the size of London and New York put together.”

This edition opens by giving us numerous suggestions about what this strange object could have been – a meteorite, a piece of antimatter, a small black hole, an atomic bomb (decades before the first recorded one was created) or even an exploding flying saucer.  But more noteworthy than this is that the pre-credits section features a different piece of introductory footage of Arthur C. Clarke.  For the previous six editions, Gordon Honeycombe’s narration about Clarke (author of 2001, inventor of the communications satellite, etc) has been combined with shots of him strolling down a Sri-Lankan beach, umbrella in hand.  But here we see him walking through the streets instead.  It’s a small point, but after watching the episodes in quick succession it does stand out – possibly the programme makers decided it was time for a change, a wise move if so.

The effects of the explosion seemed to be far reaching.  In southern England the evening was unusually light – well past midnight it was still bright enough to play golf, for example.  Whether this was connected at the time to the Siberian explosion isn’t clear, but it is interesting that the investigation into the explosion only began in 1927, nearly twenty years after the event.

One of the things that impresses about Arthur C. Clarke’s Mysterious World is how often the programme-makers were able to talk to individuals who had direct experience of the strange events featured across the series.  The Great Siberian Explosion is no exception as Dr Leonid Krinov, who investigated the explosion back in the 1920’s, gives an account of what he learnt from the eye-witnesses he interviewed.  Even though he was asking them to remember back some twenty years it seems they had no difficulty – but then such an event would be something that would no doubt stick in the memory.

Usually the series would feature several different mysteries across a single edition, but here they concentrate on just one.  The Siberian explosion is strong enough to fill the twenty five minute running time, although the widely held belief that it was a meteor or comet that exploded in the atmosphere – which explains why no crater was discovered – might disappoint those who favour a more outlandish answer.  This webpage neatly sums up the main facts, whilst the comments underneath offers some wackier explanations.  Arthur sums up all the possibilities, although he finds it difficult to keep a straight face when describing some of them (an exploding nuclear engine from a flying saucer, for example) .