We cleared a bunch of space in our deep storage area over the summer, and one of the things we found was a box full of old student theses from the 1950′s and 1960′s. The library already had copies of them, but I thought it was sort of cool to have a look into the past of the department, so we put them up on a shelf in the office. Yesterday, I was glancing over this, and spotted a thin volume, pictured in the “featured image” above, which was a Master’s thesis from 1960 (when we used to give MS degrees in physics…) titled “A Monte Carlo Study of Neutron Scintillation Detection with a Hydrogenous Crystal” by Edward Lantz and picked it up to look at.
If you’re not familiar with the jargon, it might not seem like something worth a look, but the title is referring to the Monte Carlo method, which uses random numbers to predict the results of simulated experiments. You assign probabilities to the possible outcomes at each step of the simulation, then use a random number to pick one of those. You repeat this lots of times, and compile the results to get average trajectories and the like.
This is, as you might imagine, somewhat computationally intensive. So when I saw “Monte Carlo simulation” and “1960″ on the spine of this thesis, I said “What the hell? How did they do Monte Carlo simulations in 1960? With dice?”
I was being a little unfair to 1960- they did have computers for this purpose, specifically an IBM 704 computer, capable of up to 4000 operations per second (it’s not clear whether this was at Union or elsewhere– the thesis has some gaps in its reporting of relevant information like that). They cite a 1956 publication from the Nuclear Division of the American Radiator and Standard Sanitary Corp. as the source of the code for their simulation. Reading this was a fun reminder of how different things used to be in the not all that distant past– the author was a NASA scientist during the Apollo era, and was about the age of my own grandparents.
While they did have access to a computer for this work, there were some major differences in the approach. Unlike theorists of today, they didn’t write a specialized program to do the analysis, because:
In recent years, it has been discovered that the development of a program, such as this, which not only works satisfactorily but also gives correct answers, is a formidable and time consuming job even for an experienced digital computer programmer.
Thus if one is not an experiences programmer, and does not have the resources to have the theory programmed, he must resort to the second, and not wholly undesirable, method. this is to use a proven general program and to get the output in as close to the desired form as possible by making minor changes.
So, basically, they used the output of a more general Monte Carlo program and re-interpreted its results in terms of the properties of the neutrons. The program they were using “prints out the number of neutrons from each type of collision for each energy interval of the incident neutron and each material.” They combine this with information about the position and direction of each individual neutron, “which can be obtained by converting the binary information which is stored on one of the tapes” (!!!) to determine the results.
They repeated this 30,100 times (well, 100 runs of a simulation involving 301 neutrons), and compiled the results by hand to determine the number of neutrons they would be able to detect using this material as a scintillation detector. Most of the incident neutrons wet through without hitting anything, but they still ended up analyzing the results of 2340 collisions between incident neutrons and hydrogen atoms in their simulated sample. This would be a ridiculously small sample for such a project today, but let me repeat, they analyzed the collisions BY HAND.
In large part because of these historical computing limitations, the acknowledgements are a really interesting read:
M. S. Ketchum put the desired cross sections and energy intervals into the [General Monte Carlo] program. She laboriously key punched and set up numerous problems, deciphered computer memory stop locations and came up with corrections, merged output tapes, and reran problems.
My wife counted and sorted thousands of collisions, and typed and retyped rough drafts.
I’ll try to keep this stuff in mind the next time I find myself cursing at flaky VPython simulations. Because, really, as irritating as a lot of modern computing can be, it’s so much easier than it used to be that it’s not even funny.
(Also, the obituary linked above suggested that he remained married to his collision-counting wife until his death in 2011, which is kind of nice to know…)
Another interesting factor has to do with the document preparation. Not only does he acknowledge his wife’s typing, but:
Rose Kabalian typed the multilith masters so we would not have to read blurred carbons.
While Word can be maddening, I will try to remember to be thankful that I don’t have to read blurred carbon copies of important documents, because Oh. My. God. Also, check out the hand-drawn data graph:
I’m just barely old enough to have been required to learn traditional drafting in woodshop in the 8th grade– I think it was only a couple of years later that they discontinued that in favor of a “technology” course that didn’t involve actually doing anything. So I have some idea of just how much that sort of plotting would suck. And that’s one of at least 15 (sorry, XV– they’re labeled with Roman numerals for that extra touch of class) such figures.
So, there you go. A tangible relic from the days when non-experienced programmers walked uphill through the snow to the lab to convert binary information from tapes and sort collisions by hand. Kids these days, be grateful for what you’ve got…