Then Fermi gave the command, "ZIP out!" ZIP was drawn up on its balcony rope and the ticking of the counters at once became faster.
Then Fermi turned to the man who controlled the last rod. This rod was marked in feet and inches, and Fermi said: "Pull it out to thirteen feet."
All eyes were on the instruments. Not yet. A little more. Pull it out another foot. Not yet. The men grew more and more tense as the careful work went on.
chain reaction
Finally, at about 3:25 in the afternoon, Fermi made a last check of his instruments and his calculations. Then he said: "Pull it out another foot. This is going to do it!"
No one dared breathe. The ticks of the counters became so rapid they sounded like a steady hum. The pointers on the instruments swung all the way over—and stayed there. The first atomic chain reaction had been achieved!
The pile was allowed to run for 28 minutes. Then the control rods were put back. Suddenly, all was quiet. There were no ticks from the counters.
Not only had these men started a chain reaction, they had also been able to stop it. At last man could control the energy of the atom.
One of the men present, Arthur H. Compton, ran to the phone to call James B. Conant, chairman of the U. S. National Defense Research Committee. But since our country was at war in 1942, it wasn't safe to talk about this important secret over the telephone. And so, on the spur of the moment, a quick-witted and historic conversation took place.