The Tunguska Event is still unexplained, but it’s afterglow provided days of virtual 24 hour daylight as far away as the UK!

On 30th June, 1908, in the early morning, something exploded over the Tunguska region of Siberia. Witnesses many miles away reported a blinding light and an enormous explosion, but despite much speculation the cause has never been adequately determined to the satisfaction of scientists investigating the incident. Theories include the impact from a comet or asteroid, to more bizarre propositions involving alien spacecraft and Tesla death rays.
Funnily enough, it took twenty years before any expedition went to the region to investigate what had happened. Despite the remoteness and difficulty of travel, this seems very odd since the impact of the event was so great it was experienced round the globe.
For example, for several days after the explosion, fine dust was thrown up into the atmosphere, scattering the sun’s light, making it perfectly possible to read a newspaper at midnight in the UK and turning night into day! The sky across northern Europe was lighter for several weeks. Another odd fact about the explosion was that trees immediately under the epicentre of the blast remained standing while those for several hundred miles around were blown over, a pattern of destruction similar to a nuclear explosion!
Perhaps we will never know the truth.
Sources:
BBC h2g2
Telegraph