A stack of crates containing nearly 102 tonnes of high explosive sits atop a high wooden platform. Its detonation was a trial test for the Trinity Project, the first explosion of a nuclear weapon, which happened on July 16th 1945 in New Mexico. At that time data on blast effects was limited to that produced by a few tonnes of explosives. Trinity had an expected yield equivalent to 4000 tonnes of explosives so the trial was proposed to allow calibration of the instruments for blast and shock measurements. Trace samples of fission products were dispersed throughout the stack to provide data on radioactive fall out patterns.