Yesterday we looked at computing before computers. Now let’s look at networking before the Internet. Before electric wires, did people have a way to transmit information faster than horses and pigeons? Yes! It was called the optical telegraph and was invented in the 18th century.
Imagine a network of these towers, one every 10 miles or so. The two arms can be moved to create about 100 different symbols. Tower operators observed neighboring towers with a telescope, and then passed on the message—at a rate of 2-3 symbols per minute. en.wikipedia.org/wiki/Semaphore… 
Even though the "bandwidth" was minuscule, it revolutionized communication because messages could travel at a thousand miles per hour! (In other words, low latency.)
By 1830 France had a nationwide network of over 500 towers, then many other countries. lowtechmagazine.com/2007/12/email-…
By 1830 France had a nationwide network of over 500 towers, then many other countries. lowtechmagazine.com/2007/12/email-…
Napoleon was a big proponent of the optical telegraph. It changed the course of wars by enabling early warnings of troop movements. Another major use: transmitting stock and commodity prices. But due to its low bandwidth and other limitations it didn’t find more widespread use.
The electric telegraph was invented soon after & quickly took over, perhaps because the optical telegraph had proven the usefulness of a communication network. Exponential b/w growth started 170 years ago and has resulted in a trillion-fold improvement. people.eng.unimelb.edu.au/rtucker/talks/…
If the electric telegraph hadn’t been invented, would engineers have continued to optimize the optical telegraph? How high a bandwidth could they have achieved? It's an intriguing thought experiment, and at least once the subject of sci-fi: en.wikipedia.org/wiki/Technolog…
HT @ncweaver
HT @ncweaver
The optical telegraph presaged issues that we deal with today. In the first ever information security breach, two traders in 1834 started bribing telegraph operators to secretly encode market movements as error messages. It wasn't detected until 1836! 1843magazine.com/technology/rew…
Following the telegraph hack, fearing that the ability of private parties to transmit data was too dangerous (or perhaps using the hack as an excuse), the French government promptly passed a law in 1837 banning private telegraph lines. The modern-day parallels are interesting.
One last bit of trivia for this thread: Telegraph Hill in San Francisco is named for an optical telegraph that was installed there in 1850 to signal ship arrivals. This was of great interest during the Gold Rush as supplies came in by ship.
nps.gov/features/safr/…
nps.gov/features/safr/…
