Theory of communication

We all owe a great debt to mathematician Claude Shannon and his landmark paper, “A Mathematical Theory of Communication.”

It began life as an influential 1948 article and was renamed “The Mathematical Theory of Communication” when published as a book, a small but significant title change that proved both the generality of his work and his theory of information.

Every system of communication - not just the ones existing in 1948, not just the ones made by human hands, but every system conceivable - could be reduced to a radically simple essence.

Information source > Transmitter > Channel > Noise source > Receiver > Destination

- Information source produces a message.

- Transmitter encodes the message into a form capable of being sent as a signal.

- Channel is the medium through which the signal passes.

- Noise source represents the distortions and corruptions that afflict the signal on its way to the receiver.

- Receiver decodes the message, reversing the action of the transmitter.

- Destination is the recipient of the message.

The beauty of this stripped-down model is that it applies universally. It’s a story that messages cannot help but play out - human messages, messages in circuits, messages in the neurons, messages in the blood. You speak into a phone (source); the phone encodes the sound pressure of your voice into an electrical signal (transmitter); the signal passes into a wire (channel); a signal in a nearby wire interferes with it (noise); the signal is decoded back into sound (receiver); the sound reaches the ear at the other end (destination).

In one of your cells, a strand of your DNA contains the instructions to build a protein (source); the instructions are encoded in a strand of messenger RNA (transmitter); the messenger RNA carries the code to your cell’s sites of protein synthesis (channel); one of the ‘letters’ in the RNA code is randomly switched in a ‘point mutation’ (noise); each three-‘letter’ code is translated into an amino acid, protein’s building block (receiver); the amino acids are bound into a protein chain, and the DNA’s instructions have been carried out (destination).

Those six elements are flexible enough to apply even to the messages the world had not yet conceived of. They encompass human voices as electromagnetic waves that bounce off satellites and the ceaseless digital churn of the Internet. They pertain just as well to the codes written into DNA. Although the molecule’s discovery was still five years in the future, Shannon was arguably the first to conceive of our genes as information bearers, an imaginative leap that erased the border between mechanical, electronic, and biological messages.

In time, the thoughts developed in Shannon’s 77 pages in the Bell System Technical Journal would give rise to a digital world. Satellites speaking to earth in binary code, discs that could play music through smudges and scratches (because storage is just another channel, and a scratch is just another noise), the world’s information distilled into a black rectangle two inches across.

And the very bits of information that sparkle and startle through our world every millisecond of every second of every day.

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