Asked by: Stuart Bye, Fareham
Although exact figures are secret, the Federation of American Scientists estimates there are around 19,000 nuclear warheads, 95 per cent of which are Russian and American – the UK has around 200.
Their explosive power varies enormously: the strategic thermonuclear weapons of the superpowers pack a punch measured to be equivalent to several million tonnes of TNT (1 million tonnes of TNT is a megatonne), while warheads tested by India and Pakistan are around 100 times less powerful.
But assuming every warhead had a megatonne rating, the energy released by their simultaneous detonation wouldn’t destroy the Earth. It would, however, make a crater around 10km across and 2km deep.
The huge volume of debris injected into the atmosphere would have far more widespread effects. This ‘aerosol’ of particles would reduce the amount of heat reaching the surface from the Sun, producing a so-called nuclear winter with huge environmental impact. The nuclear explosion would also unleash a pulse of electromagnetic energy that would wreck everything from national power grids to microchips around the world.