Hunting Subatomic Particles
One of the earliest devices (but not the first) that physicists used to detect, track and measure subatomic particles is something called a cloud chamber. The cloud chamber was invented in 1911 by the Scottish physicist Charles Wilson. A cloud chamber is actually a rather simple device. A glass container is saturated with water or alcohol vapor and a temperature gradient is created by placing dry ice on the bottom and a hot water pack on top. This gradient produces an atmosphere that allow clouds to form. When a radioactive substance is introduced in the chamber, it releases subatomic particles like electrons and beta particles (a helium nucleus). These particles acts as the “condensation” nuclei, and as they stream out of the radioactive source, they produce visible streams of ‘clouds’. We can not actually see the subatomic particles; what we see is water vapor (or alcohol vapor) nucleated by the particles. Different particles behave differently in different situations, like in a magnetic field across the chamber. Electrons and beta particles have opposite charges, for example, so they will bend in opposite directions in a magnetic field. Beta particles are more massive than electrons, so they will not bend as sharply.
“Seeing” electrons and beta particles is relatively easy. Any radioactive substance will do. You can actually purchase Tritium (radioactive helium isotope) or other radioactive sources and build your own cloud chamber with household items. In the past 100 years, more sophisticated devices have been invented to track subatomic particles, but the basic tracking principles are the same.
To find particles like the Higgs boson, we also need to know where and how to look for them. Physicists come up with complicated mathematics models to figure out the conditions and variables needed to produce the particles, and then try to produce them by creating the conditions and manipulating the necessary variables. There is a rather simple 3-step formula that physicists follow either knowingly or by habit. First (step 1) you study the tracks and behavior of particles in ideal conditions or situations that are easy to discern. You build on what we already know, essentially. That’s why physicists spend so much time and effort in school before actually working in a laboratory. In step 2, you manipulate the conditions and collect data in different situations following the same kind of thought processes. Then once you have enough data, you use that data to construct a working hypothesis of where and how to find the next particle. From this hypothetical reconstruction you look for the most likely place to find tracks or other evidence of new particles (step 3). The Higgs boson, for example, has made it to step 2 of this formula (enough data has been collected to develop a working hypothesis that it exists), and recently, after overcoming some complications, made it to step 3 (actually finding evidence of it’s existance). If the Higgs boson did not exist we would have had to come up with a new hypothesis.
This thought process is sometimes called the scientific method or deductive reasoning (or call it the hypothetico-deductive method if you really want to impress people), and it’s greatest power is that it allows us to know about things and processes we cannot see. This is a quite powerful and effective tool, and it has had a profound effect on how humans function in the world. We are often taught that the scientific method was first fully developed by Europeans sometime between the Renaissance and the industrial revolution, or the era loosely known as the age of Enlightenment. It is, in fact, often claimed to be directly responsible for the European ‘Enlightenment’. Other sources credit ancient Greek philosophers with first articulating the reasoning process, or at least the legitimate system of reasoning. In 350 B.C., Aristotle wrote a book titled Organon in which he articulates the art of reasoning. Unfortunately, this system did not help Aristotle in figuring out that the earth revolves around the Sun, however.
Sometime in the 1980s, a man from South Africa by the name of Louis Liebenberg started his academic career by studying physics and mathematics at the University of Cape Town and was initially interested in particle physics. After taking a course in the philosophy of science, however, he became interested in an idea that the origins of science began not with the age of Enlightenment or with the Greeks but rather with our hunting and gathering ancestors, and that tracking sub-atomic particles is not much different, conceptually at least, than hunting wild game.
Having grown up in South Africa during apartheid, Liebenberg had never worked with a black African until studying hunting techniques with the Kalahari San or !Kung people in Botswana and Namibia (often popularly known as Bushmen). Liebenberg wrote a book in 1990 titled the Art of Tracking: the Origins of Science where he states that the tracking ability of foragers and hunters “is science that requires fundamentally the same intellectual abilities as modern physics and mathematics.” When tracking down animals, for example, you can’t just follow the tracks because they disappear eventually. The hunter-gatherers gather data about the feeding habits, breeding behavior, and migrating patterns of animals, for example (step 1 of the 3-step process mentioned above). They then use the that information to create hypotheses and models about where to find more animals (step 2). The hunters then follows the models to track down and ‘confirm’ their models (step 3). This knowledge underpins “a process of creative problem-solving in which hypotheses are continuously tested against spoor evidence, rejecting those which do not stand up and replacing them with better hypotheses.” In essence, this ability is what makes us human, and for more than 200,000 years, we have used this ability for hunting animals and gathering plants, and only recently have we co-opted this strategy for finding other things like subatomic particles, criminals, and lower prices on houses, stocks and bonds, and household items.
The two major differences between hunters of Kalahari and the particle trackers at CERN are the things they are looking for and the instruments used to record data of the things’ whereabouts. Concerning the first difference, you might say that the CERN physicists have a more inefficient and indirect way of obtaining their food. They use their hunting skills to find particles they can not eat but they keep detailed records and write down their predictions and discoveries which they use to impress other people who provide them the means to obtain their food. Concerning the second difference, the San depend primarily on their memories to record data, whereas CERN physicists are somewhat deficient in their memory skills so they have come to depend on other recording devices. To be fair, the physicists have a very massive load of data to work with. They have so much data and information they share with physicists from all over the world that one of their former engineers, Tim Berners-Lee, developed in 1989 a protocol for hypertext documentation known as the ‘World Wide Web’ to make things a little easier (it initially didn’t help much with that effort, but other people outside of CERN found the protocol useful).
In 1997, Liebenberg got together with Justin Steventon, a software developer at Microsoft to found a company called CyberTracker. CyberTracker makes software for portable electronic devices that could be used to track and record wildlife. The idea was inspired by Liebenberg’s interactions among the Kalahari San. CyberTracker software is not only used to track wild game, but is also being used in wildlife preservation efforts, search and rescue missions, and even in finding criminals.
Leon Lederman. 1996. The God Particle: If the Universe is the Answer, What is the Question? New York: Houghton Mifflin.
Louis W. Liebenberg. 1990. The Art of Tracking: The Origins of Science. Cape Town, South Africa: David Phillip.
Online Resources for Creating a Cloud Chamber
Building a Cloud Chamber for detecting Cosmic Rays, from the American Museum of Natural History.