Dr. Claude E. Shannon was born 100 years ago tomorrow. He contributed greatly to the fields of engineering, communications, and computer science but is not a well known figure, even to those in the field. However, his work touches us all many times each day. The network which delivered this article to your computer or smartphone was designed upon important theories developed by Dr. Shannon.
Shannon was born and raised in Michigan. He graduated from the University of Michigan with degrees in Mathematics and Electrical Engineering. He continued his graduate studies at Massachusetts Institute of Technology (MIT) where he obtained his MS and PhD. He worked for Bell Laboratories on fire-control systems and cryptography during World War II and in 1956 he returned to MIT as a professor.
Shannon’s first impactful contribution was his masters thesis which took the Boolean Algebra work of George Boole and applied it to switching circuits (then made up of relays). Before his work there was no formal basis for the analysis of switching systems, like telephone networks or elevator control systems. Shannon’s thesis developed the use of symbolic notation to represent networks and applied simplifying rules to optimize the system. These same rules later translated to vacuum tube and transistor logic aiding in the development of today’s computer systems. The thesis — A Symbolic Analysis of Relay and Switching Circuits — was completed in 1937 and subsequently published in 1938 in the Transactions of the American Institute of Electrical Engineers.
Shannon’s doctoral work continued in the same vein of applying mathematics someplace new, this time to genetics. Vannevar Bush, his advisor, commented, “It occurred to me that, just as a special algebra had worked well in his hands on the theory of relays, another special algebra might conceivably handle some of the aspects of Mendelian heredity”. Shannon’s work again is revolutionary, providing a mathematical basis for population genetics. Unfortunately, it was a step further than geneticists of time could take. His work languished, although interest increased over time.
Shannon’s best known work is a 1948 article A Mathematical Theory of Communication published while working at Bell Laboratories. We’ve written about this work previously here on Hackaday since it is so fundamental to many of our activities. This first aspect of Shannon’s work determines the theoretical limit to how much information, how many bits, can be transferred over a communications channel. The second aspect is how to use error correction codes to approach that limit. Telephone circuits, radio communications, disk to read head data transfers, and the Internet are all are impacted by Shannon’s work.
The final contribution I’ll mention is the Nyquist-Shannon Sampling Theorem. This is important because it specifies how to sample an analog signal so that it can be reproduced accurately without creating aliases. If you are using an Arduino to sample a 1,000 Hz signal the samples must be at least twice the signal rate, in this case 2,000 Hz. An interesting implication from the theorem applies when a signal of interest is not based at zero-frequency. For example, an FM radio signal at 100-102 MHz can be sampled at 4 Mhz, twice the frequency of the interval, to extract a 4 Mhz bandwidth signal for decoding.
In addition to his more academic achievements, Shannon tinkered, or hacked, in other areas. There is a bit of confusion whether he or Marvin Minsky, the artificial intelligence guru, created what we now call the “Useless Machine” but which Shannon named “The Ultimate Machine”. It’s clear that Shannon created a nicely polished version of the machine that turns itself off.
Shannon also built a maze solving mouse. Again, the build is as nicely done as the concept. Like today’s micromouse competitions, Shannon’s mouse would work through the maze learning the pattern. It could then be placed anywhere on the maze and find its way to the end. The mouse was driven from beneath the ‘floor’ of the maze by a moving magnet. Appropriate to his MS thesis the computing mechanism is a large bank of relays. The mouse, Theseus, received attention from the press in its day.
Chess and juggling were favorite activities of Shannon so he turned his genius to creating machine versions of them. He created a W. C. Fields robot that could juggle and a relay based chess player. His analysis of an automated chess player is one of the first to address the problem.
Shannon battled Alzheimer’s disease late in life and passed away in 2001. Unfortunately he did not live to see, or understand, all the results of his achievements — especially how the impact of his work was magnified with the birth of the information age.