In August 6, 1945, at 08h15, the first nuclear bomb was dropped by the United States on the city of Hiroshima, Japan. Around 63% of all buildings were completely destroyed. A huge cloud of smoke, the famous “mushroom”, reached 12 km high, a few minutes after the explosion. Three days later, a second bomb devastated the city of Nagasaki. More than 140 thousand people died in the two cities.

What makes these weapons of mass destruction different is the enormous concentration of energy that exists within the atomic nucleus and is liberated when this is split. Oppenheimer is reported to have quoted from the Indian book “Bhagavad Gita” when he witnessed the first tests of the nuclear bomb:

If the radiance of a thousand suns were to burst at once into the sky, that would be like the splendour of the Mighty One.
 

Later, he mentioned another verse that was on his mind, namely

I am become Death, the destroyer of worlds.

Fortunately, these are the only two occasions on which nuclear bombs have been used, since their conception. One of the scientists who helped create the bomb, the physicist Philip Morrison, went to Japan soon after the event and was shocked: 

There was just one, enormous, flat, rust-red scar, and no green or grey, because there were no roofs or vegetation left. I was pretty sure then that nothing I was going to see later would give me as much of a jolt.
 

Jo Rotblat