Feynman, Richard P.

A REMARKABLE AND MOMENTOUS LETTER PROVIDING AN EYEWITNESS ACCOUNT OF THE "TRINITY" TEST, THE FIRST MAN-MADE NUCLEAR EXPLOSION, ON JULY 16, 1945

Feynman was recruited to work on what would eventually become the Manhattan Project as a graduate student at Princeton in 1942, by physicist Robert R. Wilson. Wilson was attempting to separate uranium-235 and uranium-238 by creating a device known as an isotron. In 1943, Robert Oppenheimer made an offer to Wilson's team to come to Los Alamos, which, "Like a bunch of professional soldiers," Wilson later recalled, "we signed up, en masse, to go."

While at Los Alamos, Feynman was made a group leader in Hans Bethe's Theoretical Division. Feynman would work with Bethe to develop the Bethe-Feynman Formula for calculating the yield of a fission bomb; he would also worked with the Los Alamos "Water Boiler," a small nuclear reactor, to understand chain reactions and, in particular, to study the criticality of a certain amount of nuclear material.

In his letter, Feynman describes the Trinity test bomb explosion ("I was blinded by a terrific silver white flash...In the sky I saw white clouds from above the gadget...caused by the sudden expansion following the blast wave"), the excitement of the viewing party ("We jumped up + down, we screamed, we ran around slapping each other on the backs...it had worked...as well as anyone could dare to have expected"), and the hope that the "gadget" might end the hostilities of World War II ("when we got back I had the fun of telling lots of people about it. The fellows working for me all gathered in the hall with open mouths, while I told them. They were proud as hell of what they had done. Maybe we could end the war soon. It was too much to hope. We went back to work").

Feynman claimed to be the only person to have seen the Trinity test unobstructed, having eschewed the use of the protective glasses provided. As a result, Feynman may have been the only person able to give a truly "eyewitness" account of the first nuclear explosion.

Although Feynman was proud of his work on the atomic bomb, he "ultimately expressed concern about the implications of the technology," and would later "develop safer methods for storing radioactive waste, an innovation responsible for saving the lives of many power plant workers."

Richard Feynman's autograph letter, dated "Aug 9", [1945] reads, in part:

"Dear Mom:

[...]

There is lots in the newspaper about the atomic bomb now, so I know some things I can tell you about. Remember, I left Sat. night on the plane. I got in Sunday near noon at Alb. + got met by an army car + taken to the site arriving 3 o'clock...We were all scheduled to leave on buses at 5 P.M. (so I made it by 2 hours) to go south, about 100 mi south of Alb. because we were to witness an experimental trial of our bomb. It was scheduled for 4 AM Monday morning ⁠— weather permitting.

[...]

We eventually arrived at our vantage point on a ridge overlooking a great bowl or desert at the center of which, 20 miles away, was our gadget. It was mounted on a 100 ft steel tower but we couldn't see that. We knew where to look because of searchlights which were shined on it + alternately on the clouds ⁠— the weather looked bad.

[...]

In a few minutes of listening (around 5 AM) then I heard them say, "The shot will be at 5:30, it is now minus 30 minutes." Everyone set their watches + crowded around the radio. "Minus 10 minutes." Then, "minus 3 minutes." People scattered over the hill so they wouldn't be in each others' way. They took out their dark glasses. Some even put on suntan oil. A bunch of crazy optimists, I thought. I had helped to figure out how powerful the bomb should be. I knew how many things had to go just right to get a really big blast, and I wanted a full solid experience if it did go ⁠— so I was going to look at it directly ⁠— no dark glasses for me.

[...]

I was blinded by a terrific silver white flash ⁠— I had to look away...The sky was lit up with a bright yellow light ⁠— the earth appeared white. The yellow gradually became darker ⁠— turning gradually to orange. In the sky I saw white clouds from above the gadget. (Caused by the sudden expansion following the blast wave ⁠—the expansion cools the air + fog ⁠— clouds form ⁠— we had expected this). Some thing, creates clouds! The orange got deeper but where the gadget was it was still bright, a big orange flaming ball-like mass. This started to rise, leaving a column of smoke behind below looking much like the stem of a mushroom [pencil drawing of a mushroom cloud]. The orange mass continued to rise, the orange to fade and flicker. A great ball of smoke and flame three miles across it was. Like a great oil fire billowing + churning, now black smoke now orange flame. Soon the orange died out + only churning smoke. But this was enveloped in a wonderful purple glow.

[...]

We jumped up + down, we screamed, we ran around slapping each other on the backs, shaking hands, congratulating each other, guessing at the energy released,— it had worked — as well as anyone could dare to have expected. Everything was perfect but the aim, the next one would be aimed for Japan, not New Mexico.

[...]

Later pictures and observations showed that an area about 1 mile in diameter was covered by a green glass like glaze formed by melting the sand at the surface. The sand Is brown, the glaze is bright green. It is a wonderful sight from the air to see this green area with the crater at the center, in the brown desert.

Well, when we got back I had the fun of telling lots of people about it. The fellows working for me all gathered in the hall with open mouths, while I told them. They were all proud as hell of what they had done. Maybe we could end the war soon. It was too much to hope. We went back to work."

RELATED LOTS:

See Lot 27 for Feynman's letter discussing the atmosphere at Los Alamos after the bombing of Hiroshima

REFERENCES:

See Atomic Heritage website for Robert Wilson's participation in the war effort

See NSF website for Richard Feynman's work at Oak Ridge on radioactive waste storage