The Los Alamos Primer — Section II

“We knew the world would not be the same. A few people laughed, a few people cried. Most people were silent. I remembered the line from the Hindu scripture, the Bhagavad Gita; Vishnu is trying to persuade the Prince that he should do his duty and, to impress him, takes on his multi-armed form and says, ‘Now I am become Death, the destroyer of worlds.’ I suppose we all thought that, one way or another.”

Robert Oppenheimer

“I don’t want to see that son-of-a-bitch in this office ever again.”

US President Truman (About Oppenheimer to Undersecretary of State Dean Acheson)

Julius Robert Oppenheimer (April 22, 1904 – February 18, 1967) was an American theoretical physicist and professor of physics at the University of California, Berkeley. Oppenheimer was the wartime head of the Los Alamos Laboratory and is among those who are credited with being the “father of the atomic bomb” for their role in the Manhattan Project, the World War II undertaking that developed the first nuclear weapons used in the atomic bombings of Hiroshima and Nagasaki.

The ‘Los Alamos Primer’ is perhaps the most important single document of the 20th Century. Yet, it is a rather simple document that could have been written by many others “elsewhere”, and possibly several years earlier. Thus, the History of this world could have been drastically different. In this post, I  discus the second  section of the  document. Follow us on Twitter: @INTEL_TODAY

RELATED POST: The Los Alamos Primer — An Introduction

RELATED POST: The Los Alamos Primer — Section I

RELATED POST: Significant Uncertainties in the Yield Estimate of North Korea H Bomb


Here is Section 2 of the document followed by my analysis and comments.


— — —

2. Energy of Fission Process

The direct energy release in the fission process is of the order of 170 MeV per atom. This is considerably more than 10^7 times the heat of reaction per atom in ordinary combustion processes.

This is 170 * 10^6  * 4.8 * 10^-10 /300

=  2.7 * 10^4 erg/nucleus.

Since the weight of 1 nucleus of 25 is 3.88 * 10^22 gram/nucleus, the energy release is

 7 *  10^17  erg/gram

The energy release in TNT is 4 * 10^10 erg/gram or 3.6 * 10^16 erg/ton.

Hence, 1 kg of 25 = 20 000 tons of TNT

— — —

— — —

Discussion & Analysis

The numbers are a bit fuzzy but 20 kt per kg of Uranium 235 is a rather accurate estimate of the destructive power of this new weapon. The first scientist — Was he/she a physicist or a chemist? — who made that estimate must have felt thunderstruck!

To put things in perspective, let us just say that a fleet of 20 000 bombers each carrying a  bomb weighting 1000 kg could be replaced by a single bomber carrying one nuclear weapon weighting merely 1 kg of U-235. Do I have you attention, General?

Some have argued that Ettore Majorana may have been the first to foresee the nuclear age and that would be why he disappeared without a trace, perhaps having committed suicide.

I simply don’t know but I have some stories about this because I was one of the first Westerners– perhaps the first — allowed to visit the office of Bruno Pontecorvo in Dubna. Pontecorvo kept a folder on Majorana and I had the opportunity to look at the letters. More about these later…

The CGS System? For the young people, this simple introduction must me a shock! What system of units is Serber using? Well, the CGS, of course!

Back in these days, the CGS system was predominantly used by physicists.

The Berkeley  physics courses were all developed in the atmosphere of urgency about science education created in the West by Sputnik (1957).

RELATED POST: Sputnik: 60 Years Later, the CIA Releases Declassified Documents

These courses were written in the CGS units. And so was the infamous ‘Electrodynamics’ textbook by Jackson.

It is only recently that the second volume of the Berkeley course (Electromagnetism) and some chapters of Jackson’s textbook were ‘translated’ in the MKSA system.

Richard Feynman was — as always — the exception to the rule. Right from the start, he opted for the MKSA system. But — to my knowledge — he never explained the reasons behind his choice. Some will argue that the issue is simply not worthy of Feynman’s time.

I would be willing to argue otherwise. Feynman knew when to stay away from very difficult topics… Ask yourself a simple question: what is a kilogram? And, do you know that — unlike most of us — the ‘kilogram’ is losing weight? That is funny or what?


While teaching in Bogotá in the early 2000s, I was invited to the Senate to explain the importance of the Meter Convention. I am glad that my lecture was useful and convince the Colombian senators to sign the Treaty of the Meter. [I am quite proud of this one!]

Colombia is now a full member of the Convention since 2013.  As the Dalai Lama once said:

“A good man is never at the wrong place.”

I really believe this to be true. But, if you happen to live in Belgium, ‘things’ can be quite challenging because there has never been a failed state like Belgium in History.

“The complexity of governing in Belgium — which some critics have called the world’s wealthiest failed state — may create a welcoming environment for corruption.” [New York Times]

To this day, the ‘contracts & Treaties’ — some of them known to have been antedated– between Belgium and the US during and just after the end of WWII regarding the delivery of the uranium — from the Congo — needed for the A bombs and the US control of the Belgian nuclear science and nuclear scientists after the war have never been investigated.

Let us say that none of it happened according to democratic rules… This is quite painful and I will not expand at this time. Many good people have suffered greatly. Obviously, Historians have a job to do…

Meeting John Jackson — I met Jackson in the early 90’s while visiting UC Berkeley where I had been invited to give a lecture on the topic of “second class weak currents”, aka the infamous “weak charged induced tensor”.

I did not feel much connection to Jackson, and when introduced to him, I simply told him that I had read his book. (Of course, we were all forced to study his book!) Jackson was quite funny and simply replied:

“And you still shake my hand?”

Meeting Eugene Commins — I met Commins in the summer 89. [Commins made important contribution to the Berkeley Physics Courses and chaired its steering committee.] This meeting was quite different. I suspect that Ernest Henley had asked him to push me very hard and see how ‘serious’ I was.

For sure, Commins pushed me very hard. He was quite brutal in his style, questions and comments. But I guess, he was also fair. A few months later, I received a very large US DOE grant to start my first research project.

J. Robert Oppenheimer: “I am become Death, the destroyer of worlds.” 


Revisiting The Los Alamos Primer — Physics Today

The Los Alamos Primer — Original pdf


The Los Alamos Primer — Section II

This entry was posted in Los Alamos Primer and tagged . Bookmark the permalink.

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s