Claude Shannon was a 22-year-old graduate student in 1938, at the Massachusetts Institute of Technology, the renowned US research university, when he published his master’s thesis, “A Symbolic Analysis of Relay and Switching Circuits”, in the 12 December edition of the journal *Electrical Engineering*.

“It was a transformative work, turning circuit design from an art into a science, and is now considered to have been the starting point of digital circuit design,” says the 22 December 2020 edition of *Quanta* magazine.

A 2002 article in *Scientific American* magazine said his thesis “has been called the most important of the 20th century”.

In it, Shannon “showed how the logical algebra of 19th century mathematician George Boole could be implemented using electronic circuits of relays and switches. This most fundamental feature of digital computers’ design – the representation of ‘true’ and ‘false’ and ‘0’ and ‘1’ as open or closed switches, and the use of electronic logic gates to make decisions and to carry out arithmetic – can be traced back to the insights in Shannon’s thesis.”

Shannon was in good company at MIT: Vannevar Bush (1890–1974) was the school’s dean of engineering and promoted the publication of Shannon’s thesis. Bush’s analog mechanical computer, called a “differential analyser”, was in operation while Shannon was a student, and he had a hand in its development and operation.

Shannon was born on 30 April 1916 in Petoskey, a resort town on the shores of Lake Michigan’s Little Traverse Bay in north-west lower Michigan. He earned bachelor’s degrees in both electrical engineering and mathematics from the University of Michigan and then headed to MIT for graduate studies, receiving there both a master’s degree in electrical engineering, and his doctorate in mathematics in 1940.

In 1941 he went to work at Bell Labs, in New Jersey, one of the most dynamic technological research and development facilities in the US. Towards the end of the Second World War, he submitted a confidential report titled “A Mathematical Theory of Cryptography”, dated 1 September 1945, which wasn’t declassified until 1949.

According to an article published by the New York-based Institute of Electrical and Electronics Engineers (IEEE), his ideas went into the development of a system over which US president Franklin Roosevelt and British prime minister Winston Churchill communicated during the war.

“When his results were finally declassified and published, they revolutionised the field of cryptography,” the IEEE says.

Shannon, meanwhile, in 1948 published what the IEEE calls his “most important paper”, ‘A Mathematical Theory of Communication’.

“This fundamental treatise both defined a mathematical notion by which information could be quantified and demonstrated that information could be delivered reliably over imperfect communication channels like phone lines or wireless connections,” the IEEE says. “These groundbreaking innovations provided the tools that ushered in the information age.”

According to an obituary for Shannon, published by the *Bulletin of the London Mathematical Society *and attributed to “an anonymous obituary in *The Times* newspaper on 12 March 2001”, his paper described “a mathematics, a general set of theorems rather misleadingly called information theory”.

“The information content of a message, as he defined it, has nothing to do with its inherent meaning, but simply with the number of binary digits that it takes to transmit it. Thus, information, hitherto thought of as a relatively vague and abstract idea, was analogous to physical energy and could be treated like a measurable physical quantity.

“His definition was both self-consistent and unique in relation to intuitive axioms. To quantify the deficit in the information content in a message, he characterised it by a number, the entropy, adopting a term from thermodynamics.

“Building on this theoretical foundation, Shannon was able to show that any given communications channel has a maximum capacity for transmitting information. The maximum, which can be approached but never attained, has become known as the Shannon limit. So wide were its repercussions that the theory was described as one of humanity’s proudest and rarest creations, a general scientific theory that could profoundly and rapidly alter humanity’s view of the world.

“Few other works of the 20th century have had a greater impact; he altered most profoundly all aspects of communication theory and practice.”

In the obituary for Shannon published by *Time* magazine, it notes that he “had been famous for juggling while riding a unicycle around the halls of Bell Labs, which he left in 1958 to join the faculty at MIT.

“He never taught much, and after a few semesters, told the university he didn’t wish to teach at all. (Proof that he was a big deal: MIT didn’t object.)” *Time* says.

It says Shannon spent much of his time “enjoying himself in the basement of his suburban Boston home”, in his “toy room”, where he designed contraptions such as “flame-throwing trumpets, rocket-powered Frisbees, and plastic foam shoes that he used to navigate a nearby lake, where, to an observer, it would appear as if he were walking on water”.

He was eventually diagnosed with Alzheimer’s disease, entered a nursing home in 1993, and died on 24 February 2001.