At 11:02 a.m., at an altitude of 1,650 feet, Fat Man exploded over Nagasaki. The yield of the explosion was later estimated at 21 kilotons, 40 percent greater than that of the Hiroshima bomb.
Although the destruction at Nagasaki has generally received less worldwide attention than that at Hiroshima, it was extensive nonetheless. Almost everything up to half a mile from ground zero was completely destroyed, including even the earthquake-hardened concrete structures that had sometimes survived at comparable distances at Hiroshima. According to a Nagasaki Prefectural report "men and animals died almost instantly" within 1 kilometer (0.62 miles) of the point of detonation. Almost all homes within a mile and a half were destroyed, and dry, combustible materials such as paper instantly burst into flames as far away as 10,000 feet from ground zero. Of the 52,000 homes in Nagasaki, 14,000 were destroyed and 5,400 more seriously damaged. Only 12 percent of the homes escaped unscathed
source:Office of History and resources US dept of energy
The atomic bomb resulted from research intially carried out in Germany and then moved to the USA. The following is an letter written by Albert Einstine to President Franklin Delano Roosevelt urging the US government to support research in this area before the German Government leads the way in building an exteremely powerful bomb (later known as the Manhattan project).
note: double click to read the letter clearly
