After graduating , he started work at the Underwater Explosives Laboratory of the Woods Hole Oceanographic Institute . While there , according to one obituary , he received an invitation to begin a new job , but he was not told what his duties would be , nor , initially , to where he would relocate . At first he refused , but Harvard University President James B. Conant helped persuade him to reconsider . Thus , he joined the Los Alamos Laboratory , where he was a group leader in the Manhattan Project . He worked on the firing unit that was used for the implosion of the plutonium device . He helped prepare the first atomic bomb , Trinity , and witnessed its explosion , the first detonation of a nuclear device . He was sent up to the top of the tower twice the previous day to reassure a nervous Robert Oppenheimer that all was well
Trinity
Trinity (nuclear test)
Donald Hornig