From how far away could we survive a nuclear explosion?

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Although you may not know it, you may live close to a nuclear bomb. If one was to go off, how far away would you need to be to survive?

It has been more than 70 years since the nuclear bombs were dropped on Hiroshima and Nagasaki, killing at least 129,000 people and causing devastating effects for long term health. Until now, these are the only two nuclear bombs that have been dropped in the context of war, but almost 15,000 nuclear warheads remain in the world nowadays, many of them being much more powerful than those used during the Second World War. So, what exactly would happen if one was to explode tomorrow? How far away would you need to be to survive the cataclysm? The AsapSCIENCE team has a few answers for you….

First and foremost, it is important to note that several factors must be taken into account, including the time at which the bomb explodes (day or night), the geographical configuration of the area in which the explosion occurs, and whether the bomb explodes on land or in the air. But in general, there are a few predictions that can be made. As explained in the video below, around 35% of the energy released from a nuclear bomb is emitted in the form of thermal radiation. This can move almost as quickly as the speed of light, meaning that the first thing to hit you would be a huge flash of blinding lightning and intense heat.

The light itself is enough to cause flash blindness, a temporary form of blindness that could last a few minutes. The video here deals with a potential 1 megaton bomb, thus 80 times more powerful that the bomb that exploded in Hiroshima, but much less powerful than several modern nuclear weapons. With a bomb of this calibre, people within an 85 km radius would be temporarily blinded. In terms of the heat, minor first degree burns would be caused at a distance of 11 km away from the bomb, and third degree burns would be experienced at 8km from the site of detonation. If the third degree burns covered more than 24% of the surface of the body, they would probably be fatal in the absence of urgent medical attention.

Note that these distances could vary depending not only on the weather, but also on what you are wearing. White clothes could reflect part of the energy from an explosion, while darker clothes would absorb it. Of course, these measures wouldn’t make much of a difference for the unfortunate people located at the centre of the explosion.

The temperatures near the site of the Hiroshima explosion were estimated at 300,000 degrees Celsius -around 300 times hotter than in an incinerator, meaning that people located near the explosion would have been immediately reduced to ashes. For the others, within a 6 km radius, the shock waves would have produced over 180 tons of force on the walls of all the two story buildings and the wind speed would have reached around 255 km/h. Within a one kilometer radius, the pressure would have been 4 times higher and the wind speed would have reached around 756 km/h. Technically, humans can tolerate such pressure, but most people would be killed by flying debris.

Note that this video was published in response to that published a few days previous by American bloggers who sounded the alarm: thousands of nuclear bombs could be situated close to large cities in the United States, Europe, Turkey, Israel, Russia, Pakistan, India, China and in North Korea.