Thursday, October 04, 2012

The Christy Gadget

Christy was one of the last Manhattan Project survivors.
NYTimes: Robert F. Christy, who as a young Canadian-born physicist working on the Manhattan Project came up with a critical insight that led to the creation of the world’s first atom bomb, died on Wednesday at his home in Pasadena, Calif. He was 96.

... The first bomb, developed in secrecy during World War II at Los Alamos, N.M., relied on implosion. The plan was to detonate a sphere of conventional explosives, the blast from which would compress a central ball of nuclear fuel into an incredibly dense mass; that in turn would start a chain reaction that would end in a nuclear explosion.

But the Los Alamos team discovered that the interface between the detonating explosives and the hollow sphere could become unstable and ruin the crushing power of the blast wave.

Dr. Christy, while studying implosion tests, realized that a solid core could be compressed far more uniformly, and he worked hard in the days that followed to convince his colleagues of its superiority. He succeeded, and the hollow core was replaced with one made of solid plutonium metal.

A 1993 book, “Critical Assembly,” sponsored by the Department of Energy, which maintains the nation’s nuclear arsenal, said Dr. Christy’s insight reduced the risk that the core would lose its spherical form and thus fail to explode.

And Robert S. Norris, an atomic historian and the author of “Racing for the Bomb,” called Dr. Christy’s breakthrough, known as the Christy pit, “a conservative solution to a problem they were having” that “increased the likelihood of a successful detonation.”

[ The bomb itself was called the "Christy Gadget". ]

Robert Frederick Christy was born May 14, 1916, in Vancouver and studied physics at the University of British Columbia. He was a graduate student at the University of California, Berkeley, under J. Robert Oppenheimer, a leading theoretical physicist who became known as the father of the atomic bomb.

After completing his studies in 1941, Dr. Christy worked at the University of Chicago before being recruited to join the Los Alamos team when Oppenheimer became its scientific director.

After the war, Dr. Christy joined Caltech in theoretical physics and stayed at the university for the rest of his academic career, serving as a faculty chairman, vice president, provost (from 1970 to 1980) and acting president (1977-78). He was elected to the National Academy of Sciences.
Caltech Oral History:
Then, in the examinations at the end of grade twelve, they gave us general exams — and this was given to the whole province of British Columbia ... I could get top marks in anything, in that kind of exam. So I got the highest marks on these exams of anyone in the province.


MtMoru said...

"Then, in the examinations at the end of grade twelve, they gave us
general exams — and this was given to the whole province of British
Columbia ... I could get top marks in anything, in that kind of exam.
So I got the highest marks on these exams of anyone in the province."

And in Shitmerica such a person wouldn't even get an interview at CalTech if he had less than a 3 pt at his shitty American public high school.

Richard Seiter said...

@MtMoru do you know of a case where someone with that kind of test scores (note that if he got a uniquely distinguishable "highest score in the province" the test had a high ceiling, unlike the current SAT) failed to get an interview with Caltech? I went to an undistinguished rural non-college town public high school (which nonetheless managed to send a half dozen people to HYM from my class and the few following) and Caltech actually sent an interviewer to the school my year. Of my college interviews, that interviewer seemed to be the one who most looked for (and best assessed) a passion for math/science. I was impressed. (I wonder how Caltech admissions would react to stellar, say +4SD which would be my ballpark guess for "highest in BC" circa 1930's, test scores with a GPA < 3. Can anyone who knows comment?)

More on-topic, does anyone know how many WWII Los Alamos scientists are still alive?

Paul said...

Prof. Hsu posted an interview with the economist Vernon Smith, a CalTech grad, who mentioned that he had had a very low high-school GPA but still managed to gain admission after he aced a bunch of courses at a local college and then took the entrance exams (and presumably did very well). He would be roughly a decade younger than Christy, I believe.

A very different era. In some ways much more meritocratic, in other ways much less so. Reading the histories as recounted by people like Christy, Delbruck, Mayr, Coleman etc, you get the sense that the most important thing for securing a faculty position, or even a spot in a graduate program, was having a person, especially a prominent person, "inside" who would recommend you. Linus Pauling application to Berkeley's graduate program was thrown in the trash because he had attended the "Oregon Agricultural College," which nobody at Berkeley had ever heard of.

Richard Seiter said...

Thanks. Link for anyone else interested:

David E Long said...

I think the elided part is of some importance in general (though not to your comment about Caltech admissions). If you read the full text at the link you'll see that in school he received excellent grades in science and math, but didn't do well in English and history. However, the general exams were all true/false or multiple choice. He mentions that and only then states "I could get top marks in anything, in that kind of exam." He then follows up with "...[I]t was solely because of the type of exam. It makes a big difference to a quantitative mind."

My impression from interviewing with an area Caltech alum when I applied was that they were looking mostly for passion and talent in science and math, not for "well-rounded" students. I know that my verbal SATs were definitely below their norm, and my grades in non-STEM subjects were fairly good but not stellar. I was still accepted.

Blog Archive