Nuclear weapons
Nuclear weapons owe their origin to the work of the great physicist Albert Einstein even though he took no part in the development of nuclear weapons. As part of his work on relativity he produced his famous energy equation E=MC2. In expanded form this means that the energy of an object is its weight multiplied by the speed of light squared. The speed of light is over 180,000 miles per second, so what Einstein demonstrated was that there is a huge amount of energy contained in even small amounts of matter. If that energy could be released quickly it would result in a very powerful explosion.
When Ernest Rutherford succeeded in creating the first nuclear reaction in 1917 it was only a matter of time before military use of this technology would be explored, and the driving force was the upsurge of Nazism in Germany and the outbreak of the Second World War. It was widely believed that the Nazis were making progress on the development of a nuclear weapon and the US set up the Manhattan Project in 1942 to ensure the US was not left behind in this area. The project had the participation of physicists from the US, Canada and the UK as well as immigrant physicists from other countries. They succeeded in their mission and the first nuclear powered explosion took place in July 1945. The test proved to be spectacularly successful and the bomb they had created, which was about the size of a torpedo, created an explosion equivalent to 20,000 tons of TNT.
Less than one month later a nuclear bomb was dropped on Hiroshima in Japan completely destroying an area of about 5 square miles and instantly killing at least 70,000 people. The Hiroshima bomb was followed three days later by the dropping of a second bomb on Nagasaki. Nagasaki was not the mission’s primary target, which had been obscured by cloud, and even though the explosive power was greater than at Hiroshima, the bomb exploded over an industrial area of the city thereby taking a lower death toll of around 35,000 people. A third bombing was planned for later that August and six more over the following two months, but the Japanese surrender meant these attacks were not required.
To date, these are the only two occasions that nuclear weapons have been exploded but work has continued on developing even more lethal weapons such as hydrogen and neutron bombs with explosive charges measured in the equivalent of millions of tons of TNT. And the US is no longer the only nation with the technology. Russia, China, the United Kingdom, France, India, Pakistan and North Korea have all exploded test devices and there may be other countries with nuclear weapons capacity.
The biggest threat from nuclear weapons in the present day seems not to be from countries at war with each other but from rogue nations or terrorists managing to detonate a small device in a major city. It is almost inevitable that this will happen.