White smoke from the Sistine Chapel yesterday signaled church leaders had selected a new pope. People hear this and say things like “Smoke signals? Really? Is this some relic from the Council of Nicaea (325 CE) or something?” 
The actual usefulness of signalling by smoke is not as old as it seems to some of us today. Until the 19th Century, information couldn’t move faster than people. Horseback was the fastest communication means.
In 1794, the government of France set up a multi-hop communication system based on Semaphore flag stations located a few miles apart. In 1844, the US government spent roughly a half million dollars setting up a telegraph line running 40 miles from Washington DC to Baltimore. When the line was officially opened, Samuel Morse sent the famous first message: What hath God wrought
In the 1850s, the high-tech startup, Atlantic Telegraph Company, raised the equivalent of $40 million (2013 USD) from investors to set up a cable across the atlantic. There were no repeaters. The transmission line characteristics were poor, so the on-off-keyed symbols (i.e. dots and dashes) had to be very long to prevent intersymbol interference. The cable also greatly attenuated signals, requiring the development of sensitive receivers.
Simply laying the cable was a problem in mechanical engineering. The cable rested on the bottom of the ocean, so the weight of the cable behind the ship laying the cable was enormous. On one attempt the cable broke. On another attempt the ships encountered dangerous weather that threatened to destroy the ships. 
When the cable was complete in 1858, there was a large celebration in New York City. Before the cable, it could take months for news of major events to reach even the most powerful and connected people. Politicians and commentators suggested this new technology could change the whole human race and possibly lead to an end to war.
This first transatlantic telegraph system was crude. It took hours to send short messages. The cable only lasted a month.
Better cables were laid, and eventually transatlantic communication came to be taken for granted. The fantastical predictions when the first telegraph cables were laid and when the internet was commercialized in the 90s, such as an end to war, are slowly coming true. In a world where much value is stored in information that can be transmitted electronically, there are fewer spoils of war. Anecdotes, videos, memes, and fictional stories easily published around the world trick us into putting ourselves in other people’s shoes.
It is not an exaggeration to say people working on wireless communication are changing the world. A hundred years ago smoke signals would have been a reasonable way to communicate information wirelessly to a city. Now it’s something we laugh about. What hath God wrought, indeed.
Further Reading:
A Thread Across the Ocean - Details the story of raising money for and laying the cable.
NYT: Cardinals Elect new Pope - Image Source