Estimates of the yield of the North Korean May 25 nuclear test continue to surface. Currently, estimates range from 2 to 20 kilotons, based on calculations using seismographic readings. The magnitude of the explosion has been estimated from around 4.5 to as high as 5.3 on the Richter scale, with the latter number coming from the Japan Meteorological Agency. Both Russia and South Korea have now released estimates on the high end of the scale, indicating a 10-20 kiloton yield. These higher numbers would suggest a successful demonstration of a nuclear detonation on par with that of the Fat Man, the atomic bomb dropped on Nagasaki on August 9, 1945, though the Comprehensive Nuclear-Test-Ban Treaty Organization has released estimates in the 'low single digit' kiloton range. With such a wide range of estimates, it is hard to make any definitive statements on the matter. (The results of atmospheric samples are generally classified and their implications take longer to emerge.) What does seem to be clear is that this test was significantly more powerful than Pyongyang's 2006 attempt. That attempt, by almost all estimates, fizzled or otherwise failed. According to some reports, North Korea was attempting what it had estimated would be a 4 kiloton test. Seismographic data from that test indicated that it was less than a kiloton. One theory associated with the lower estimates of the 2009 test has been that this may be a successful test of a newer version of the same 4-kiloton device that failed in 2009. Pyongyang could be attempting to keep the device small and light enough for considerations related to delivery. But smaller devices with lower yields can be more technically challenging. The lower estimates could also suggest a fizzle or failure of a significantly larger device. North Korea's work on its nuclear weapons design has no doubt continued apace in the intervening years, and it is very difficult to say what lessons were gleaned from the 2006 test and what changes to the program were subsequently made. Though North Korea's 2006 nuclear test was unsuccessful in demonstrating a definitive nuclear capability, Pyongyang's engineers no doubt gathered valuable insight from that failure. Indeed, in weapons testing, engineers can often learn more from failures than successes. Admittedly, North Korea has not demonstrated much. STRATFOR has noted the immense challenges that stand between detonating a crude device and actually fabricating miniaturized, ruggedized nuclear weapons. The status of Pyongyang's work in these areas is obviously difficult to discern, but the detonation of a device — potentially successful — should not be interpreted as North Korea having the capability to mount that device on a ballistic missile or even fit it in the small bomb bay of one of its H-5 light bombers — North Korea's heaviest combat aircraft. The H-5 is a Chinese copy of the 1950s era Il-28 "Beagle," and a nuclear device would have to be smaller and significantly lighter than the Fat Man to fit inside its bomb bay. But while it remains to be seen what consensus emerges on seismographic data (and there is much that may never be known about the tests), one of the single most important points about this test is not parsing out just how powerful the device was at all, but rather recognizing the value of ongoing testing. North Korea is the only country in the world to have tested a nuclear device in the 21st century. It has now done so twice. In so doing, Pyongyang has provided North Korean engineers with a wealth of technical data and information on the performance of its weapons architecture and design. The North Korean nuclear program marches on.