kiloton of TNT

The kiloton is a convention before it is a measurement. Real TNT releases anywhere from about 4.1 to 4.7 MJ per kilogram depending on how it detonates, so yield reporting pinned the kiloton to a round 10¹² thermochemical calories, exactly 4.184 TJ, and that is the figure every published yield is denominated in. No actual TNT is involved in a modern yield estimate.

The scale it names predates the bomb. The 1917 Halifax explosion, a munitions ship fire in the harbour, is benchmarked at about 2.9 kt and stood as the largest man-made explosion until the Trinity test of 1945, itself roughly 20 kt. Converted to grid units a kiloton is startlingly small: 4.184 TJ is 1.16 GWh, roughly an hour's output of one large power station. What separates a weapon from a power plant is not the quantity of energy but the microseconds it is released in.

Seismology runs the unit backwards: underground test yields are estimated from seismic body-wave magnitude, and published magnitude-to-kiloton relations are how test-ban monitoring turns a seismogram into a yield claim without anyone visiting the site. Here, the kinetic energy solver is the usual road into this unit: half the mass times velocity squared for a meteor or an impactor, converted from joules to kilotons, is the arithmetic behind every headline that counts an event in Hiroshimas.