The Experiment of the Century


The Jornada Del Muerto, the Dead Man’s Trail, a waterless seventy-five-mile stretch of alkaline desert in southern New Mexico north of Alamogordo, was named in an age when transportation depended on water and grass rather than refined hydrocarbons. In secrecy, in the spring of 1945, the last year of the Second World War, dedicated and determined men moved equipment into that emptiness to prepare to conduct the largest physics experiment ever attempted up to that time.

The United States government was sponsoring the experiment, an attempt to trigger the first full-scale fast-neutron chain reaction—that is, to explode an atomic bomb. Some government leaders believed a successful test would confirm their monopoly on an invincible new weapon of war. But the scientists who were preparing the experiment understood otherwise. They understood that success would challenge the international political system as no other innovation had challenged it before, offering it a choice between destruction or radically limited belligerency. That prospect mitigated the remorse they felt at introducing into the world a weapon capable of leveling a city. The physicist responsible for the weapon’s development, a subtle and literate theoretician named Robert Oppenheimer, embedded the paradox of a violence that might also redeem in the name he gave the test site. He called it Trinity, which alluded, he explained later, to the holy sonnet of John Donne that begins “Batter my heart, three-person’d God …” and concludes ”… for I / Except you enthrall me, never shall be free, / Nor ever chaste, except you ravish me.”

The U.S. Army leased the David McDonald ranch in the middle of the Jornada site for a field laboratory. The physicist Kenneth T. Bainbridge, in charge of the Trinity test, marked out ground zero thirty-four hundred yards northwest. Contractors built earthsheltered bunkers, with concrete slab roofs supported by oak beams thicker than railroad ties, at compass points north, west, and south, ten thousand yards away—two for cameras, recording instruments, and searchlights, one for use as a control bunker. A base camp of tents and barracks took shape five miles south. Twenty miles northwest Compañia Hill served as a VIP scenic overlook. When the first manmade slow-neutron nuclear reaction had started up in a pile of graphite and uranium stacked on the floor of a doubles squash court under the west stands of the University of Chicago football stadium three years earlier, the VIP scenic overlook had been no farther away than the squash-court balcony. The change of scale calibrated the difference in energy release between the two historic experiments, half a watt compared with the equivalent of eighteen thousand tons of TNT.

A hundred-foot prefabricated steel tower went up at ground zero with a corrugated-iron cab at the top to house the test device. The device itself, which its inventors insouciantly called a “gadget,” was delivered in two separate shipments. The core—two silver-plated plutonium hemispheres the size of a baseball and a little walnut-sized initiator of goldplated beryllium and polonium— rode down from Los Alamos on July 12,1945, in a shock-mounted carrying case in the back seat of an Army sedan, like a visiting general. The high-explosive assembly in its five-foot conical duralumin case left Los Alamos on the back of a truck just after midnight on Friday the thirteenth, deliberate bravado timing against the day’s unlucky reputation.

Friday morning the pit-assembly team clicked the initiator into place between the two plutonium hemispheres, nested the core in a hollowed plug of uranium, and drove the heavy cylinder to the tower. A crew there, Oppenheimer among them, worked through the day to insert the pit assembly into the center of the high-explosive arrangement and button it up. They bandaged the multiple holes in the case, where detonators would be inserted, with crosses of white tape. Saturday, twisting slowly and looking wounded, the gadget winched its way into the cab at the top of the tower as the scientists watched nervously in the hot sun. With the device settled safely on its skid, another crew unbandaged it, inserted its multiple detonators, and connected them through a harness of cables to a bank of battery-powered capacitors that would charge them. Oppenheimer gave his offspring a final inspection Sunday evening; it crouched in the high cab ugly as Caliban.

The test was scheduled for Monday morning, July 16, just before dawn. Los Alamos scientists, project leaders flown down from Washington, and Army men gathered to watch it. A front off the Gulf of Mexico had blown in. Thunderstorms began lashing the Jornada at about 0200 hours. “It was raining cats and dogs, lightning and thunder,” the Columbia University physicist I. I. Rabi remembered, and everyone was “really scared [that] this object there in the tower might be set off accidentally.” But by 0315 the clouds had begun to open and a few stars were shining. The countdown started in the control bunker ten thousand yards south of ground zero. At 0529:45 the firing circuit closed.