• Kyodo

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The atomic bomb dropped on Hiroshima by the United States in August 1945 may have exploded about two minutes later than commonly thought, according to data found Tuesday at a former weather station in the city.

An atmospheric pressure graph recorded at the station about 3.6 km south-southwest of the hypocenter shows a bomb blast at 8:18 a.m. on Aug. 6, 1945, contradicting records from the U.S. bomber Enola Gay that the atomic bomb was dropped at 8:15 a.m. and exploded about 43 seconds later.

If the graph is accurate, it would mean that the bomb was dropped at around 8:17 a.m.

“Meteorological data at that time were military secrets, and time was recorded strictly based on Japan Standard Time,” Fumitaka Wakabayashi, head of the Hiroshima City Ebayama Museum of Meteorology, told Kyodo News.

“Equipment error, if any, would have been within one minute, and I believe (the data) recorded the explosion time quite accurately,” he added.

On the graph recorded at the now-defunct Ebayama weather station, the line for atmospheric pressure stops about three minutes after 8:15 a.m., possibly due to the explosion’s effect on the equipment. Pointing to the end of the line are pencil markings saying “bomb blast” and “8h18m6,” or 8:18 a.m.

The discovery follows a similar one made in Nagasaki three years ago in which data at the Nagasaki marine observatory showed the other atomic bomb dropped on Japan by the U.S. detonated there at either 10:52 or 10:45 a.m. on Aug. 9, 1945, instead of the commonly assumed 11:02 a.m.

Kazuhiko Takano, deputy head of the Hiroshima Peace Memorial Museum, cautioned, “Matters such as the weather station’s geographical situation, the path and amount of time taken for the blast to reach it must also be considered.

The data contradict Enola Gay records, but I believe they would be difficult to verify.”

Reports along with witness accounts in Japan indicate explosion times that range between 8:10 a.m. and 8:20 a.m.

U.S. documentation also fails to agree on the exact timing of the Hiroshima bomb.

Aviation records from the Enola Gay indicate the bomb was dropped 30 seconds after 8:15 a.m., while some crew members recalled 17 seconds. A U.S. investigative team reported in 1947 that the atomic bomb exploded at around 8:17 a.m.

The bomb dropped on Hiroshima created a massive fireball that brought temperatures at the hypocenter to an estimated 3,000 to 4,000 C. Approximately 140,000 people had died by the end of December 1945 as a result of the bomb and many others suffered radiation illnesses.