Science is the quintessential double-edged sword. Humanity has wielded it to radically improve and extend life, but also to end life. Nowhere is the latter better exemplified than with nuclear weapons.
Originally welded into reality by the legendary scientists of the Manhattan Project, nuclear fission weapons make use of enriched uranium or plutonium to fuel a nuclear chain reaction. Atomic nuclei fly apart, and because of energy-mass equivalence (E = mc2), an enormous amount of energy is released on the order of tens of thousands of tons of TNT.
Years later, scientists took destruction to the next level, designing thermonuclear weapons -- fusion bombs. These devices make use of a an atom-splitting fission reaction to ignite an even more powerful fusion reaction, in which two isotopes of hydrogen (tritium and deuterium) join together, releasing a monumental amount of energy. These bombs yield destructive power on the order of tens of millions of tons of TNT.
Nuclear weapons also give rise to insidiuous radioactive contamination, which pollutes the environment and causes cancer. Partly because of this, a nuclear bomb's mushroom cloud has come to ominously symbolize death and devastation. (Although, it should be noted that any large explosion will produce a mushroom cloud.)
Thankfully, nuclear weapons have been used against humans only twice in the course of history. Both instances were perpetrated by the United States against Japan during World War II. However, nuclear weapons have actually been detonated over two thousand times for testing purposes, a combined yield of 510.3 megatons.
In 1996, the Comprehensive Nuclear Test Ban Treaty was formulated by the United Nations General Assembly in the hopes of putting an official end to nuclear testing. Though it has not yet officially gone into effect, nuclear testing has slowed to a near standstill.
What follows is a list of the eight countries which have conducted the most nuclear weapons tests.
(Image: Four Types of Nnuclear Tests via Wikimedia Commons)