The Tunguska event of 1908

The largest explosion ever to occur in historical times on Planet Earth took place at 7.40 a.m. on 30^th June 1908. It is extremely fortunate that it happened in a remote part of the vast northern Siberian forest, because its consequences would have been catastrophic had it affected a populated area.

The explosion, which had the force of 1,000 Hiroshima bombs, took place four miles above the Tunguska Forest. Half a million acres of forest were devastated, and trees were knocked flat twenty miles from the epicentre of the blast. They formed a vast circle of felled timber, with the trees pointing away from the direction of the explosion. People were knocked off their feet sixty miles away. The flash of the explosion, in the form of a huge blue fireball, could be seen 500 miles away.

What caused the big bang?

There has been considerable debate as to the cause of the Tunguska event.  The most likely explanation is that a cosmic object detonated when it hit the Earth’s atmosphere at a speed of around 60,000 miles an hour. There is speculation over whether it was an asteroid, possibly weighing as much as 100,000 tons, a large meteorite or a comet.

Some less probable suggested causes include a matter/antimatter detonation and the nuclear drive of a visiting UFO exploding.

The chances of finding a final answer are not good, given that the explosion left no crater and no apparent fragments of the original object.

Could it happen again?

There’s absolutely no reason why not! The Solar System is awash with thousands of objects that either never became parts of planets or moons or have broken away from larger bodies after collisions that may have occurred millions of years ago. We know that large objects have caused devastation in the distant past – such as the events that led to mass extinctions and craters such as the one in Arizona – and it would be bizarre to believe that Planet Earth has had its last such encounter.

However, astronomers are now far better placed to spot objects heading our way than they were back in 1908. This is especially true of lumps of rock of similar size to the one that caused the Tunguska event. At present there is no sign of anything out there that is likely to cause a catastrophic impact with Earth within the lifetime of anyone now living.

However, should another Tunguska rock come our way, the wilds of Siberia are just about the best place for it to hit us. An explosion over a major population area, or even one over the open ocean that caused a massive tsunami, would lead to enormous loss of life.

© John Welford