Megalopoli (Ancient Greece), c. 150. Polybial historians (c. 200-118) invented a communication system that allowed complex information to be disseminated at high speed at long distances. He assigned a number to each alphabetical character in Greek and used several hogueras or torches to transmit it remotely. In a word, the smoke was what caused the different sets of numbers to be transmitted, and if the Polybio code was known, the sets of numbers were converted into words. This number translation code in letters is known as the Polybio Square and throughout history has been a very popular system and used in cryptography.

But the Greeks were not the only ones who used smoke signals in ancient times. Also in the vast Chinese Empire, a rapid and effective communication system was needed, and to do so, an excellent road had been built: Great Wall. To report the enemy's attacks, the soldiers of the wall sent out smoke signals. Tower by tower, the message could travel hundreds of miles in a few hours.

In the case of films, the main users of the smoke signals were the American Indians. We've seen that they weren't the only ones or the first ones, and their systems didn't have any sophistication of the Polybio code. Originally, each tribe had its own signal system, probably so that the enemy wouldn't understand the messages they wanted to convey. But colonization brought them a common enemy and unified some basic signs: a smoke ball meant being alert, two balls indicated that everything was quiet and three predicted problems and dangers.

In general, although smoke signals have been used to warn of the presence of foreigners, Australian Aborigines used an inverse method: they sent out smoke signals from which they entered foreign territory to warn the natives that they were there and that they did not want problems.

Today, there's an institution that still uses the smoke signal that we all understand: white smoke means Habemus Papam.