WHILE NORTH KOREA claimed to have successfully tested a nuclear weapon this week, according to the Washington Times, U.S. officials remain skeptical. But whatever it was that the North Koreans exploded underneath a mountain, the blast registered somewhere in the neighborhood of 4.0 on the Richter scale, which probably translates to a yield of less than 1 kiloton, or the equivalent of 1,000 tons of conventional explosives. Of course, estimating yields is a science of "considerable imprecision" according to John Pike, the founder and director of globalsecurity.org, who cautioned against drawing any conclusive assessments of North Korea's success or failure.

For its part, the New York Times described the yield as "fairly small by traditional standards, and possibly a failure or a partial success." The paper justified this verdict by basing it on the fact that "the first detonations of aspiring nuclear powers have tended to pack the destructive power of 10,000 to 60,000 tons . . . of conventional high explosives." But viewing the North Korean test in that context may be misleading.

On July 16, 1945, the U.S. military staged the world's first successful nuclear test at the Trinity Test Site near Alamagordo, New Mexico. The bomb, or the "gadget," as it was referred to by the scientists working on the Manhattan project, used a hollowed out sphere of high explosives to create a fission reaction in its plutonium core. At the time, it was estimated the bomb would yield no more than 20 kilotons, a force

Four years later, on August 29, 1949, the Soviet Union went nuclear. The Soviets detonated a bomb which was a replica of the "Fat Man" plutonium weapons tested at Alamagordo (and subsequently dropped on Nagasaki). The Soviet bomb, nicknamed "Joe 1" by the American military, produced a yield of 22 kilotons. Over the next 10 years, the Russians mastered the technology of both fission and fusion weapon design, and by late 1961 the Soviets had detonated a thermonuclear H-Bomb with a yield of 50 megatons, or the equivalent of 50,000,000 tons of TNT. That test still holds the record as the largest man-made explosion in history. (The largest explosion in recorded history was the 200 megaton blast created by the eruption of the Indonesian volcanic island Krakatoa in 1883).

In May of 1974, India detonated a nuclear weapon which was officially called the "Peaceful Nuclear Explosive," and unofficially dubbed the "Smiling Buddha." The Indians, too, employed a design similar to that of the American "Fat Man" bomb, using conventional explosives to detonate a plutonium core. The Indian government claimed that the test, carried out in India's Thar Desert, yielded a blast of 12 kilotons, though analysis of the crater and seismic activity led experts to put the actual yield closer to 8 kilotons. This was the last test conducted by India until five devices were tested in early May of 1998.

In response to India's renewed testing, Pakistan claimed to have tested five devices in the Chagai District of Baluchistan Province in 1998. The tests were conducted underground and, though estimates vary, the initial blast probably produced a yield of roughly 8 kilotons (though Pakistani sources have claimed it was as powerful as 40 kilotons) and registered at 4.8 on the Richter scale.