The world's nuclear powers have set off thousands of the warheads since they were first developed. This map, from Radical Cartography designer Bill Rankin, tracks every nuclear explosion since 1945:

As the two military superpowers of the past six decades, the United States and Soviet Union are obviously on the top of the list.

But France has notably tested a lot of nuclear weapons in the past five decades — more than four times as many as China. The enormous number of tests in the Pacific islands triggered a diplomatic crisis with New Zealand, when in 1985 French operatives sank a Greenpeace boat parked in the Oceanic country that was on its way to protest a French nuclear test in the island of Moruroa.

The map also includes one event, labeled with a question mark, that may not have been a nuclear test at all: the Vela incident. In 1979, a US satellite picked up a double flash, which can sometimes indicate a nuclear explosion, off the coast of South Africa. It's been widely speculated that the flashes showed a joint nuclear test by South Africa and Israel, which has an officially undeclared nuclear program. A presidential panel concluded that the incident could have been a result of a meteorite hitting the satellite and causing a malfunction, but other groups, including the Defense Intelligence Agency, dispute the panel's conclusions to this day.

These nuclear tests can seem terrifying, and they are certainly horrible for the environment, especially in the effected areas. Still, the weapons are also one reason, as Vox's Zack Beauchamp explains, that there's less war in the world today: