Eminent scientist Stephen Hawking warned that the biggest threat to human existence is advancement of science and technology. One of the main technological dangers he mentioned were nuclear weapons.
Precisely so, as we already know the havoc a nuclear bomb can cause. No one can forget the damage by Fat Man and the Little Boy, the political friction caused when Buddha Smiled or accidental disasters in Chernobyl and Fukushima.
Significantly, North Korea carried out an underground nuclear test of an explosive device on 6 January, 2015 and has threatened western powers of an attack.
But in the post second World War era, having a nuclear arsenal means staying ahead.
What can be the magnitude of destruction? Which country has the highest number of nuclear warheads?
These numbers will give you some answers.
All multi-story brick buildings in both cities, at an average distance of 5,000 feet, were completely decimated.
Such terror struck mankind for the first time. Japan's Emperor Hirohito surrendered unconditionally on 15 August, ascribing the reason to "a new and most cruel bomb".
The following years were marked by a mad race for nuclear weapons between the USSR and the USA. In 1949, USSR detonated its first atomic bomb, called First Lightning and USA in 1952 detonated the world's first hydrogen or thermonuclear bomb, much powerful than atom bombs.
During the cold war period, the world did come close to a nuclear war but thankfully, it never happened.
France has 300 warheads, China has 250, UK has 225.
Apart from these countries, Pakistan has 120 nuclear warheads, India has 110, Israel has 80 and North Korea has about 10.
There's some good news. As of 2015, all these nine states had about 15,850 nuclear warheads, about 500 warheads lesser than 2014.
But the main threat isn't from nuclear war but from nuclear disasters. Nuclear energy, apart from making bombs, is used for generating electricity.
On 26 April, 1986 a chemical explosion released 520 dangerous chemicals that contaminated Belarus, Ukraine and Russia that immediately killed 31 people and exposed 600,000 lakh people to radiation.
Millions still live in under continuous exposure to radiation.
From cancer risks and psychological effects of relocation, the adverse effects of Fukushima will take a long time to reduce.
This in turn would 'shorten the agricultural season around the world and reduce global food supply'.
The result: Another climatic disaster of epic proportions.