In point of fact, it is possible to tell the difference between a small nuclear explosion and a large one by a very simple method. The calling card of a nuclear bomb is the blinding flash that is far more dazzling than any light on earth. Brighter even than the sun itself - and it is by the duration of this flash that we are able to determine the size of the weapon. After the flash, a fireball can be seen to rise, sucking up under it the debris, dust and living things around the area of the explosion. And as this ascends, it soon becomes recognizable as the familiar "mushroom cloud".As a demonstration of the flash duration test, let's try and count the number of seconds for the flash emitted by a very small bomb; then a more substantial, medium sized bomb; and finaly, one of our very powerfull high-yield bombs.