Galileoís Semaphore Telegraph

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    Communications serves as the nervous system of civilization. Without the ability to transmit information rapidly and efficiently, a society plods through History. Speeding up communications can certainly help a society to pick up the pace of its development and operation.

    It certainly made France a force to be reckoned with from the end of the Eighteenth Century onward. In 1792 Claude Chappe and his brother invented a semaphore telegraph (and also invented the words "semaphore" and "telegraph") that the government used in a network spread across the country and into some neighboring countries (one line went from Paris, through Lyon, and ended in Venice). It gave Napoleon just enough advantage that the English and their allies had greater difficulty than they had anticipated in defeating him (and then only because of that little visit to Russia). At its greatest extent the network consisted of 556 stations spanning 4800 kilometers and it could send messages at speeds greater than 400 kilometers per hour (in one test 36 symbols went from Paris to Lille, a distance of 230 kilometers, in 32 minutes). The system lasted until 1854, when it was completely replaced by the electric telegraph.

    But suppose that the Chappe system had been invented 180 years earlier, in 1612. We may actually be astonished that it wasnít. After all, Galileo Galilei understood the value of obtaining information quickly over great distances: he had stood on a tower and used his new telescope, a little 10-power spyglass, to spot ships coming in to Venice before other people saw them and thereby gained his employer an economic advantage. Surely, we think, the idea of sending signals back and forth over great distances by viewing them through telescopes must have occurred to him. Now suppose that it had and that he had acted on the idea.

    Galileo made his first perspicillum in July 1609, the year after it was invented in the Netherlands by Hans Lippershey, Zacharias Janssen, and Jacob Metius. (The word telescope was introduced in 1611 by the mathematician Giovanni Demisiani.) Galileo immediately turned his instrument toward the sky and began making important astronomical discoveries. He also used it to sight ships at sea for the benefit of his patron, Cosimo Medici II. And he got into a controversy with the Jesuits over whether the instrument showed the truth of whatever the observer saw through it.

    In that latter action Galileo demonstrated the telescope to the Jesuits by asking them to look through the telescope at objects that they could then walk over to and examine close up. But that experiment only showed that the telescope was good over short distances. To prove the proposition that the telescope presents visual truth over longer distances, Galileo might have conceived the idea of sending a man to a hilltop with a set of flags. The man would hold up the flags in a pattern that he chooses when he reaches the hill and a Jesuit watches him through the telescope. Comparing the flagmanís report with their own manís observations would tell the Jesuits that the telescope is good over distances that we would measure in kilometers. That particular experiment might also have inspired Galileo to conceive a means of transmitting detailed information over great distances.

    A person with 20-20 vision can resolve a pair of lines (that is, see them as two lines instead of one) separated by an angle of 1.2 arc minute (3.49x10-4 radian), which corresponds to an object one meter wide at a range of 30 kilometers. A 10-power telescope makes that meter-wide object much easier to see or it enables an observer to see that panel, given appropriate contrast, at a range of 300 kilometers. Seeing that distance over level ground would require that the observer stand on a tower a little over seven kilometers tall in order to accommodate Earthís curvature. But Galileo doesnít need to see 300 kilometers from one tower.

    In the Thirteenth Century Italy suffered a tower-building craze. Families vied with each other to see who could build the tallest tower in town. Some towers approached heights of 100 meters (La Torre degli Asinelli in Bologna reaches 97.2 meters) and even fairly short towers, such as the Leaning Tower of Pisa, exceeded 50 meters, the height of a 17-storey building. From a tower 50 meters tall the horizon appears a little over 25 kilometers away, so two 50-meter towers 50 kilometers apart would be just within eyeshot of each other, though their mutual line of sight would graze the ground at a point midway between them. Putting the towers closer together would raise that line of sight off the ground. Building the towers on hilltops would be even better. The continued existence of the Medieval towers in modern Italy testifies to the skill with which the Italian builders could erect towers.

    So, perhaps inspired by the Roman aqueducts, Galileo would have conceived his Scientiaduct (knowledge carrier). It would comprise a series of towers, built on hilltops or high ground, between 30 and 50 kilometers apart. If the towers stand an average of 40 kilometers apart, then the line from Rome to Paris needs about 30 towers, the line from Rome to Madrid needs 35 towers, and the line from Rome to Warsaw needs 38 towers. The time that a message takes to pass from one end of a line to the other roughly equals the time taken to transmit the whole message to the first tower plus a number obtained by multiplying the number of towers in the line by the time it takes to receive (or transmit) one block of the message (in essence, the time it takes the beginning of the message to pass through the entire line).

    The genius of the system lies in the coding. This would be the hard part for Galileo, though as a mathematician he was well-equipped to meet that particular challenge. He had to determine in which form the message was to be transmitted. When modern people see the word telegraph, they tend to think of Morse code, spelling out words letter by letter through a series of dots and dashes. But the Chappe system used a coding technique that would have been more natural for Galileo: the semaphores transmitted numbers that referred to pages in a code book and the order of the words on the page. Galileo would likely have conceived the idea of using a similar vocabulary book, a dictionary without the definitions. It would all be done in Latin, of course, so the first few pages of the coding book would include the codes for the declension of nouns and the conjugation of verbs as well as certain very common phrases (e.g. The Holy, Roman, Catholic, and Apostolic Church or His Holiness, the Pope). Thus, for example, if Galileo transmits the numbers (24, 15), the person receiving the message will go to page 24 and note the 15th word on that page. The book would also contain codes for the letters of the alphabet in order to include proper names and foreign words.

    Binary code provides the best way to transmit numbers through the system and we may assume that the numbers in the coding book would be accompanied by their binary equivalents to ease the task of coding the message. The binary numbers would not likely be depicted as arrays of ones and zeroes: they would more likely be depicted as simplified pictures of the flags or panels used to send the messages and that includes the page numbers. Decoding a message would be difficult at first, but would become easier as the coders got accustomed to reading the binary code. In the same way telegraphers using the electric telegraph learned early on that they did not need the dots and dashes printed on a paper tape; they could read the letters directly from listening to the clicks of the telegraph itself. Of course, the semaphore itself would have to possess a binary nature and the easy system consists of five meter-wide panels set one meter apart in an horizontal array (roughly twenty feet wide) set against a dark background. The parapet over which those panels faced would be whitewashed to provide a shallow square U to bracket the semaphore. When a panel is turned to the horizontal it effectively disappears from the sight of an observer in the next tower and thus codes a zero and when the panel is turned to the vertical it becomes visible to the next tower and codes a one. The panels are manipulated by five levers mounted to the tower floor behind them and the positions of the levers tell the sender what number is being transmitted.

    But five panels can only encode the numbers from zero to 31. The coding book will certainly have more than 31 pages (likely fewer than 1024 [the square of 32], carrying fewer than 32,768 [the cube of 32] words in total), so each word will have to be represented by a trio of 5-digit binary numbers. The first two of those numbers will be the equivalent of a 10-digit binary number, encoding the numbers from zero to 1023. That should be enough to encode the pages in the coding book and there would likely be fewer than 32 words on a page. To transmit a word, then, the sender manipulates the semaphore to display the three numbers and then displays a code to represent the space between words.

    So imagine the scene on the top floor of one of the relay towers. Two semaphores sit on opposite sides of the room and a two-man crew sits by each of them: the operator sits behind the levers and looks through a telescope and the recorder stands by a coding pegboard (which looks like a cribbage board with five rows instead of four) and a basket of pegs. Each row on the pegboard represents a number, so three rows represent a word or its inflection. If the pegboard has 30 holes in each row, the board will hold five words.

    On the receiving side of the tower the operator has his semaphore set to neutral (all five panels horizontal, representing 0-0-0-0-0) and looks through his telescope at the next tower down the chain. He reads the number being transmitted and the recorder puts pegs into the holes to represent ones, leaving the empty holes to represent zeroes. The recorder acknowledges having the number and the operator flashes the ready sign on the semaphore (likely flipping the center panel up and then lowering it) and reads the next number. If receiving a number takes five seconds, then the recorder can fill the pegboard in two and one half minutes. If thatís a typical receiving (and retransmission) rate, then one block of a message (one full pegboard) from the Pope in Rome to the King of France in Paris (a distance of a little over 1200 kilometers) in an hour and a quarter. It will take eight and one third hours to feed a 1000-word document into the system, so the King of France will get the Popeís message a little over nine and a half hours after the transmission begins.

    On the sending side of the tower the recorder takes the filled pegboard from the apprentice, who spends his day shuttling pegboards and pegs back and forth between the teams. The recorder reads a number off the pegboard, starting at the top, and the operator sets his semaphore to display that number. When he sees the acknowledgment sign through his telescope, he asks for the next number. As he works his way down the pegboard, the recorder removes the pegs from each row as the operator sets the semaphore and drops them into a basket. For the operator, who canít actually see the panels of his semaphore, the positions of the levers show him what number heís displaying to the next tower up the line. In using flat panels the Galilean telegraph resembles the system proposed in 1795 by Lord George Murray and built in Great Britain.

    Building and operating a trans-European telegraph system in the early Seventeenth Century would have been a daunting challenge. There was really only one institution that had the means and the incentive to meet that challenge Ė the Holy, Roman, Catholic, and Apostolic Church. Still reeling from the effects of the Protestant Reformation and deeply concerned about the religious wars plaguing Northern Europe, high officials in the Catholic Church would have seen the value in having a system that gave them the ability to communicate rapidly over long distances.

    Some years earlier, in 1597, Sir Francis Bacon wrote in Meditationes Sacrae that "knowledge itself is power" and, more explicitly, "Human knowledge and human power meet in one; for where the cause is not known the effect cannot be produced." That doctrine would have been made manifest in the Scientiaduct: if knowledge is power, then the ability to spread knowledge rapidly will enhance that power. But, in addition to its practical aspect, the Scientiaduct would do more to enhance the Churchís power: it would serve as an advertisement of the Churchís divine authority.

    Consider one simple fact. It would be possible to send a short message from Rome to Madrid (about 1380 kilometers, requiring 35 relay towers) and receive the reply back in Rome the same day. That fact would have left the people of the time utterly flabbergasted. If the message had been sent by something equivalent to the Pony Express, covering a little over 300 kilometers per day, the message and its reply would have taken nine days to go around the circuit. People would have stood in awe of the Scientiaduct and of the institution that built and operated it.

    To make the system less expensive to operate and to associate it more closely with the Church, the relay towers would be built near monasteries and convents (or monasteries and convents would be established near the towers). Monks and nuns would operate the system, providing the additional advantage of security on the messages.

    Of course, the Church would not have held the monopoly on the telegraph system for long. The kings of France, Spain, and Poland would certainly want their own systems. The Protestants, fragmented like a stomped eggshell, would have been at a disadvantage: only the kings of England and Denmark would have possessed the wherewithal to build and operate a telegraph system (remember that Norway and Sweden were provinces of Denmark at the time, only gaining independence in 1814). As for the German principalities, the French and the Poles, able to coordinate their actions rapidly by communicating through the telegraph line that ran through Northern Italy, would have clapped their armies together and turned Germany Catholic again. They might even have united the German states under a Catholic kaiser, producing a unified Germany over two centuries before Bismarck did. And they certainly would have caused an outflux of Protestants, who would seek refuge in America, thereby increasing the non-native populations of the colonies there.

    The Americas would not have been neglected by the telegraph builders. The Spanish would certainly have built a trunk line through Mexico and on into California, following the missions. This would have happened in the late 1700's. The French would have built their American telegraph along the west bank of the Mississippi River from New Orleans to Saint Louis and perhaps beyond. The eventual United States would have ended at the Mississippi River, facing the roughly equally large French-speaking nation of Louisiana. The British would have established their system running from Georgia to Maine, with branch lines extending into Canada and over the Appalachian Mountains to the Mississippi River.

    In this world of semaphore telegraphs History would have gone along a path very different from the one it actually followed for us. Settlers would have followed the telegraph lines, as settlers followed the railroads in our history. More people would have settled the interior of Louisiana, especially if the British, aided by the telegraph line and associated road going up the Hudson Valley and into Canada, had succeeded in conquering Quebec and sending more Acadians (Cajuns) to Louisiana. With a more productive state built in that territory, the French government, in 1803, would not have sold the land to the Americans. In time Louisiana would have evolved into an independent French-speaking nation.

    The American Revolution, if it had occurred at all, would have been altered by the telegraph, but not, I think, in favor of the British. The Revolutionary War was a fairly typical guerilla war: the British occupied the cities and the Americans owned the countryside, making British troop movements difficult, if not impossible, as Johnny Burgoyne and Charlie Cornwallis discovered. The Americans thus would have controlled access to most, if not all, of the telegraph towers. At worst they would have denied use of the system to the British. At best they would have used the telegraph themselves, enabling George Washington to coordinate troop movements over the entire battlespace in a matter of days rather than weeks. The Americans might even have taken Canada, sending the loyalists to England and thence to other British colonies, such as Australia. The western expansion of the United States would then have gone to British Columbia rather than California.

    Yes, imagine what might have been and what might have happened if only one man had discovered a practical use for the telescope around 1610. It would have been such an easy thing to do. So for the reason he didnít do it we must look to the psychological analysis of human endeavor. We do know that the Christian churches discouraged innovation. Novelties were disparaged and even taken as signs that the innovator might be practicing witchcraft. Even in fairly liberal areas the presence of the Inquisition had a chilling effect. Galileo may have been inhibited by a subconscious sense that in his work with the telescope he was pushing his luck. Perhaps we should ask whether we are doing something similar to ourselves.


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