Ko da yake Oppenheimer ya rubuta wa Ernest Rutherford yana neman izinin yin aiki a dakin gwaje-gwaje na Cavendish. Bridgman ya ba Oppenheimer shawarwari, wanda ya yarda cewa rashin lafiyar Oppenheimer a cikin dakin gwaje-gwaje ya nuna cewa ƙarfinsa ba gwaji ba ne amma ilimin lissafi ne. Rutherford ba shi da sha'awar, amma Oppenheimer ya tafi Cambridge a cikin bege na saukowa wani tayin. Daga bisani J. J. Thomson ya yarda da shi a kan yanayin da ya kamata ya kammala wani tsari na asali na dakin gwaje-gwaje. Ya ci gaba da dangantaka mai ban sha'awa tare da malamin sa, Patrick Blackett, wanda ya kasance 'yan shekaru kaɗan ne kawai. Yayin da yake hutu, kamar yadda abokinsa Francis Fergusson ya tuna, Oppenheimer ya rubuta wa Ernest Rutherford yana neman izinin yin aiki a dakin gwaje-gwaje na Cavendish.
Oppenheimer ya kasance mara kyau