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Trinity Site
Wsmr P Route 10
Alamogordo, New Mexico 88310

The First Atomic Test

On Monday morning July 16, 1945, the world was changed forever when the first atomic bomb was tested in an isolated area of the New Mexico desert. Conducted in the final month of World War II by the top-secret Manhattan Engineering District, this test was code named Trinity. The Trinity test took place on the Alamogordo Bombing and Gunnery Range, about 230 miles south of the Manhattan Project's headquarters at Los Alamos, New Mexico. Today this 3,200 square mile range, partly located in the desolate Jornada del Muerto Valley, is named the White Sands Missile Range and is actively used for non-nuclear weapons testing.

Before the war the range had been public and private grazing land that had always been thinly populated. During the war it was even more lonely and deserted because the ranchers had vacated their homes in January 1942. They left because the land had been withdrawn by the War Department for use as an artillery and bombing practice area shortly after the December 7, 1941, Japaneses attack on Pearl Harbor. In September 1944, a remote 18 by 24 square mile portion of the northeast corner of the Bombing Range was selected for the Trinity test by the military.

The selection of this remote location in the Jornada del Muerto (Journey of Death) Valley for the Trinity test was from an initial list of eight possible test sites. Based on a number of criteria that included availability, distance from Los Alamos, good weather, few or no settlements, and that no Indian land be seized, the choices for the test site were narrowed down to two in the summer of 1944. The first choice was the military training area in southern California. Second choice, was the Jornada del Muerto Valley in central New Mexico. The final site selection was made in late August 1944 by Major General Leslie R. Groves, the military head of the Manhattan Project and the Trinity test. When General Groves discovered that in order to use the California location he would have to talk to its commander, General George Patton, Groves quickly decided on the Jornada del Muerto.

The Trinity test was originally set for July 4, 1945. However, final preparations for the test, which included the assembly of the bomb's plutonium core, did not begin in earnest until Thursday, July 12. The abandoned George McDonald ranch house located about two miles south of the test site served as the assembly point for the device's core. After assembly, the plutonium core was transported to Trinity Site to be inserted into the thing or gadget as the device was called. But, on the first attempt to insert the core, it stuck! After letting the temperatures of the core and gadget equalize, the core fit perfectly, to the great relief of all present. The completed device was raised to the top of a 100-foot steel tower on Saturday, July 14. During this process workers piled up mattresses beneath the device to cushion a possible fall. When the bomb reached the top of the tower without mishap, installation of the explosive detonators began. The 100-foot tower (a surplus Forest Service fire-watch tower) was designated Point Zero. Ground Zero was at the base of the tower.

Technicians installed seismographic and photographic equipment at varying distances from the tower. Other instruments were set up for recording radioactivity, temperature, air pressure, and similar data wanted by the project scientists.

Workers built three observation points 5.68 miles (10,000 yards), north, south, and west of Ground Zero. Code named Able, Baker, and Pittsburgh, these heavily-built wooden bunkers were reinforced with concrete, and covered with earth. The bunker designated Baker or South 10,000 served as the control center for the test. This is where head scientist J. Robert Oppenheimer would be for the test. A fourth observation point was the test's Base Camp, (the abandoned Dave McDonald ranch) located about ten miles southwest of Ground Zero. A fifth was on Compania Hill, 20 miles to the northwest near the Stallion Gate. Most of the scientists and observers present for the test were on Compania Hill.

The test scheduled for 4 a.m., Monday, July 16, had to be postponed due to a severe thunderstorm that would have increased the amount of radioactive fallout locally, and would have interfered with the test results. However, the rain finally stopped, and at 5:29:45 a.m. Mountain War Time, the device exploded successfully and the Atomic Age was born. The nuclear blast created a flash of light brighter than a dozen suns. It was seen over the entire state of New Mexico and in parts of Arizona and Texas. The resultant mushroom cloud rose to over 38,000 feet within minutes, and the heat of the explosion was 10,000 times hotter than the surface of the sun! Felt at ten miles away, this heat was like standing directly in front of a furnace. Every living thing within a mile of the tower was obliterated. The yield of the Bomb was estimated to equal 20,000 tons of TNT, or equivalent to the bomb load of 2,000 fully loaded World War II B-20, Super fortresses!

Immediately after the test, a Sherman M-4 tank, painted white, equipped with its own air supply, and lined with two inches of lead went out to explore the site. The lead added 12 tons to the tank's weight, but was necessary to protect the tank's occupants from the dangerous high radiation levels at ground zero. The tank's passengers found that the 100-foot steel tower had virtually disappeared, with only the metal stumps of its legs imbedded in concrete remaining. Surrounding the area where the tower had been was a crater almost 2,400 feet across and about ten feet deep. Desert sand in the crater had been fused by the intense heat of the blast into a glass-like solid the color of jade.

Due to the intense secrecy surrounding the test, no accurate information was released to the public until after the first atomic bomb had been dropped on Japan. However, people in New Mexico were aware that something extraordinary had happened early that morning of July 16, 1945. The blinding flash of light, followed by the shock wave, made a vivid impression on people who lived within a radius of at least 160 miles from Ground Zero. Windows were shattered 120 miles away in Silver City, NM. Residents of Albuquerque, New Mexico's largest city, saw the bright light of the explosion on the southern horizon and felt the tremor of the shock waves moments later.

The true story of the Trinity test first became known to the public on August 6, 1945. This is when the world's second nuclear bomb, nicknamed Little Boy, exploded 1,850 feet over Hiroshima, Japan, destroying a large portion of the city and killing an estimated 70,000 to 130,000 of its inhabitants. Three days later on August 9, a third atomic bomb devastated the city of Nagasaki and killed thousands more Japanese (70,000 by the end of 1945). The Nagasaki weapon was a plutonium bomb, similar to the Trinity device, and it was nicknamed Fat Man. On Tuesday August 14, at 7 p.m. Eastern War Time, President Truman made a brief formal announcement that Japan had finally surrendered and World War II was over.

Pictures and information were provided by US Department of Energy

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