• Confusing statements in Sect. 4.3 on predetonation yield have been clarified.
• Section 4.5, also new, describes the physics of the neutron initiators that were
developed during the Manhattan Project to trigger Little Boy and Fat Man.
• Section 5.4, also new, investigates the amusing claim that the energy of fission
can make a grain of sand visibly jump.
The fact that you are reading this indicates that you appreciate that the discovery
of nuclear energy and its liberation via nuclear weapons was one of the pivotal
events of the twentieth century. The strategic and military implications of this
development drove much of cold-war geopolitics for the last half of that century,
and remain with us today in the form of weapons stockpiles and deployments,
proliferation, fissile-material security concerns, test-ban treaties, and concern with
the possibility that terrorists or unstable international players might be able to
acquire enough fissile material to assemble a crude nuclear weapon. For better or
worse, stabilizing or destabilizing, the legacies of the United States Army’s
“Manhattan Engineer District,” Los Alamos, Oak Ridge, Hanford, Trinity, Little
Boy, Fat Man, Hiroshima, and Nagasaki will continue to influence events for
decades to come, even as the number of deployed nuclear weapons in the world
declines.
To sensibly assess information and claims regarding these concerns, one needs
some knowledge of the physics that backgrounds nuclear weapons. Should you be
merely concerned or downright alarmed if you learn that a potential adversary
country is “enriching uranium to 20%
235 U” or “developing fuel-rod reprocessing
technology”? Why is there is such a thing as a critical mass, and how can one
estimate it? How does a nuclear reactor differ from a nuclear weapon? Why can’t a
nuclear weapon be made with a common metal such as aluminum or iron as its
“active ingredient”? How did the properties of various uranium and plutonium
isotopes lead to the development of the “gun” and “implosion” weapons used at
Hiroshima and Nagasaki? How did the developers of those devices estimate their
expected energy yields? How can you arrange to assemble a critical mass in such a
way as to avoid blowing yourself up beforehand? This book is an effort to address
such questions at about the level of a junior-year undergraduate physics student.
This work grew out of three courses that I taught at Alma College, supplemented
with information drawn from a number of my own and other published research
articles. One of the courses was a conventional undergraduate sophomore-level
“modern physics” class for physics majors which contained a unit on nuclear
physics. Another was an algebra-level general-education class on the history of the
making of nuclear weapons in World War II, and the third was a junior-level topics
class for physics majors that used much of the present volume as its text. What
originally motivated this book was that there seemed to be no one source available
for a reader with a college-level background in physics and mathematics who
desired to learn something of the technical aspects of the Manhattan Project in more
detail than is typically presented in conventional texts or popular histories. As my
own knowledge of these issues grew, I began assembling a collection of derivations
and results to share with my students, and which evolved into the present volume.
viii
Preface to the Fourth Edition
• Section 4.5, also new, describes the physics of the neutron initiators that were
developed during the Manhattan Project to trigger Little Boy and Fat Man.
• Section 5.4, also new, investigates the amusing claim that the energy of fission
can make a grain of sand visibly jump.
The fact that you are reading this indicates that you appreciate that the discovery
of nuclear energy and its liberation via nuclear weapons was one of the pivotal
events of the twentieth century. The strategic and military implications of this
development drove much of cold-war geopolitics for the last half of that century,
and remain with us today in the form of weapons stockpiles and deployments,
proliferation, fissile-material security concerns, test-ban treaties, and concern with
the possibility that terrorists or unstable international players might be able to
acquire enough fissile material to assemble a crude nuclear weapon. For better or
worse, stabilizing or destabilizing, the legacies of the United States Army’s
“Manhattan Engineer District,” Los Alamos, Oak Ridge, Hanford, Trinity, Little
Boy, Fat Man, Hiroshima, and Nagasaki will continue to influence events for
decades to come, even as the number of deployed nuclear weapons in the world
declines.
To sensibly assess information and claims regarding these concerns, one needs
some knowledge of the physics that backgrounds nuclear weapons. Should you be
merely concerned or downright alarmed if you learn that a potential adversary
country is “enriching uranium to 20%
235 U” or “developing fuel-rod reprocessing
technology”? Why is there is such a thing as a critical mass, and how can one
estimate it? How does a nuclear reactor differ from a nuclear weapon? Why can’t a
nuclear weapon be made with a common metal such as aluminum or iron as its
“active ingredient”? How did the properties of various uranium and plutonium
isotopes lead to the development of the “gun” and “implosion” weapons used at
Hiroshima and Nagasaki? How did the developers of those devices estimate their
expected energy yields? How can you arrange to assemble a critical mass in such a
way as to avoid blowing yourself up beforehand? This book is an effort to address
such questions at about the level of a junior-year undergraduate physics student.
This work grew out of three courses that I taught at Alma College, supplemented
with information drawn from a number of my own and other published research
articles. One of the courses was a conventional undergraduate sophomore-level
“modern physics” class for physics majors which contained a unit on nuclear
physics. Another was an algebra-level general-education class on the history of the
making of nuclear weapons in World War II, and the third was a junior-level topics
class for physics majors that used much of the present volume as its text. What
originally motivated this book was that there seemed to be no one source available
for a reader with a college-level background in physics and mathematics who
desired to learn something of the technical aspects of the Manhattan Project in more
detail than is typically presented in conventional texts or popular histories. As my
own knowledge of these issues grew, I began assembling a collection of derivations
and results to share with my students, and which evolved into the present volume.
viii
Preface to the Fourth Edition