#1. United States

Number of Tests: 1032

No country has more prolifically explored nuclear weapons than the United States, spending approximately $8.52 trillion to develop them. The U.S. currently maintains a stockpile of around 5,000 warheads.

In 2009, President Obama outlined plans to achieve a "world without nuclear weapons." Over the past decades, the world's nuclear superpowers have been slowly but surely working toward such a goal. The U.S. and Russia have both substantially de-nuclearized since the arms race of the Cold War, which, as Carl Sagan opined, was analogous to “two sworn enemies standing waist deep in gasoline, one with three matches, the other with five.”

It remains to be seen whether the world will be able to douse and do away with the remaining matches.

Sources: Yang et. al., Brookings, Reuters

(Image: Wikimedia Commons)