| Trinity Explosion at White Sands, Alamogordo, New Mexico. The mushroom cloud eventually reached 70,000 feet. Within 10 days of the explosion, radioactive fallout reached 46 states, Canada and Mexico. The famous mushroom cloud at 12 seconds after detonation. At the instant of detonation – 0529 Hours Mountain War Time on July 16, 1945 — came an incredible burst of light, bathing the surrounding mountains in an unearthly brilliance. Then came the shock wave that knocked over 2 men at the S-10000 bunker 10,000 yards (9,100 meters) south of the tower, then the thunderous roar. A vast multi-colored cloud surged and billowed upward. The steel tower that held the bomb vanished, the tower that held “Jumbo,” the discarded thick metal container to reclaim the plutonium in case the test failed, 800 feet away, lay crumpled and broken on the ground. Wrote Enrico Fermi (September 29, 1901 – November 28, 1954) shortly after the test: “My first impression of the explosion was the very intense flash of light, and a sensation of heat on the parts of my body that were exposed. Although I did not look directly towards the object, I had the impression that suddenly the countryside became brighter than in full daylight. I subsequently looked in the direction of the explosion through the dark glass and could see something that looked like a conglomeration of flames that promptly started rising. After a few seconds the rising flames lost their brightness and appeared as a huge pillar of smoke with an expanded head like a gigantic mushroom that rose rapidly beyond the clouds, probably to a height of the order of 30,000 feet (9,100 meters). After reaching full height, the smoke stayed stationary for a while before the wind started dispersing it.” Fermi then went on to explain the simple experiment he took time to conduct that helped considerably in making the 1st early estimates of the bomb’s success. “About forty seconds after the explosion the air blast reached me. I tried to estimate its strength by dropping from about six feet small pieces of paper before, during and after the passage of the blast wave. Since, at the time, there was no wind, I could observe very distinctly and actually measure the displacement of the pieces of paper that were in the process of falling while the blast was passing. The shift was about two and a half meters, which at the time, I estimated to correspond to the blast that would be produced by ten thousand tons of Trinitrotoluene (TNT).” Hans Bethe (July 2, 1906 – March 6, 2005) wrote that “it looked like a giant magnesium flare which kept on for what seemed a whole minute but was actually one or two seconds. The white ball grew and after a few seconds became clouded with dust whipped up by the explosion from the ground and rose and left behind a black trail of dust particles. The rise, though it seemed slow, took place at a velocity of 120 meters per second. After more than half a minute the flame died down and the ball, which had been a brilliant white became a dull purple. It continued to rise and spread at the same time, and finally broke through and rose above the clouds which were 15,000 feet (4,500 meters) above the ground. It could be distinguished from the clouds by its color and could be followed to a height of 40,000 feet (12,000 meters) above the ground.” Joe McKibben, another scientist, (1912 – 2001) recalls that “we had a lot of flood lights on for taking movies of the control panel. When the bomb went off, the lights were drowned out by the big light coming in through the open door in the back. After I threw my last switch I ran out to take a look and realized the shock wave hadn’t arrived yet. I ducked behind an earth mound. Even then I had the impression that this thing had gone really big. It was just terrific.” “The shot was truly awe-inspiring,” Norris E. Bradbury (May 30, 1909 – August 20, 1997), said. “Most experiences in life can be comprehended by prior experiences but the atom bomb did not fit into any preconception possessed by anybody. The most startling feature was the intense light.” Harvard physicist Kenneth T. Bainbridge (July 27, 1904 – July 14, 1996) has said that the light was the 1 place where theoretical calculations had been off by a big factor. “Much more light was produced than had been anticipated.” | |
| Image Filename | wwii2176.jpg |
| Image Size | 648.22 KB |
| Image Dimensions | 2091 x 2898 |
| Photographer | |
| Photographer Title | Department of Energy |
| Caption Author | Written or Adapted by Jason McDonald |
| Date Photographed | July 16, 1945 |
| Location | |
| City | Alamogordo |
| State or Province | New Mexico |
| Country | United States |
| Archive | National Archives and Records Administration |
| Record Number | NWDNS-434-N-65(7539) |
| Status | Caption ©2026 MFA Productions LLC Please Do Not Duplicate or Distribute Without Permission; Image in the Public Domain |
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