The Original Transatlantic Communication

Transcription

1 Menooa Badalian The Original Transatlantic Communication Abstract: The Transatlantic cable, running under the Atlantic Ocean, is the groundbreaking achievement of the late 19 th century. Since it was the first technology of its kind, engineers were faced by impending decisions regarding the required material, sending signals efficiently, and physically laying the cable across the Atlantic Ocean. Some of the problems they faced along the way led to the development of some of the most notable concepts in physics and electromagnetics. Since 1866, it has paved the way for future scientists and engineers to constantly improve on the technology and create newer ones. The most notable advancements that have been conceived from the Transatlantic Cable are the transatlantic telephone cable and later on radio communication. Keywords: Transatlantic Cable, Atlantic Ocean, communication, telegraph, Field Page 1 of 13

2 Figure 1: The British Lion and the American Eagle connecting both continents by the Transatlantic Telegraph wire [2]. Introduction: One hundred fifty years ago, the first telegraphic message was sent across the Atlantic from Queen Victoria to President James Buchanan congratulating him on the success of the transatlantic cable. This was officially the first telegraph exchange over the new cable, and it was one of the greatest engineering achievements of the 19 th century, enabling Europe to be directly connected to the North Americas [1]. A message that would have taken twelve days to travel from Europe to the North Americas was being sent in matter of minutes; enabling people to share news and common knowledge with each other across the two continents [2]. This article will discuss the history of the Transatlantic Cable; how the idea came about, the problems faced by the engineers and the solutions for these problems. Furthermore, it will also examine how this Page 2 of 13

3 groundbreaking technology paved the way for the future generations to discover and create new modes of communication. History: In 1937, C. Wheatstone and W. F. Cooke patents a workable telegraph [3]. In 1842, Samuel F. B. Morse, the co-inventor of the Morse code and a well-known painter, experiments with telegraph cable and sends the first message through a wire, enabling long distance communication between two sources. In the same year, the United States Congress approves a thirty thousand dollar bill to be used in construction of the first telegraph line across the United States [4]. Two years later, in 1844, Morse builds the first North American telegraph system between Washington, DC and Baltimore, Maryland [1]. By the next decade, the era of instant communication was born; not only the United States but also most countries in Europe were able to communicate with each other through wires. This allowed new sources of commerce to develop and people were able to share common local knowledge throughout the United States and Europe. Although, people in the Americas and people in Europe were able to communicate with each other locally, oceans isolated the Americas from the rest of the world and international news was still carried by wind and sail. It was still a dream for both Europeans and Americans to be able to instantly communicate [4]. It was not until 15 years later, in 1857, when a young American businessman by the name of Cyrus West Field got together with local investors and convinced them to invest in a project that would attempt to link Europe and America through a wire. Even though in the mid-19 th century electricity was still a mystery and there was no adequate vocabulary to talk about electricity, the investors agreed and invested large sums of money into the project. Cyrus West Page 3 of 13

4 Field became the leading promoter of the great Transatlantic Telegraph Cable project and the idea went into development [1, 4]. Cyrus Field and the Atlantic Telegraph Company decided that the best route for the cable was from Telegraph Field, Foilhommerum Bay, Valentia Island in western Ireland to Heart's Content in eastern Newfoundland. Once in place, locally connected cables on both sides of the Atlantic would then distribute the signal within various cities inside the United States and Europe [3]. Figure 2: The map of the submarine Atlantic Telegraph [8]. Page 4 of 13

5 Manufacturing: The project required the right kind of wires, and overall wires are nothing more than a conductor and an insulator. Even for a colossal wire such as the Transatlantic Cable, all that was required was a conductor and an insulator. The challenge was to figure out a technique to construct it in such a way that it would be strong enough to support different forces, flexible enough to be coiled on board, and most importantly be salt-water proof [1]. Since the invention of the telegraph in the 1820 s, copper had been, and still is, the most conductive non-precious metal, with a conductivity σ=5.96x10 7 Siemens per meter, known to mankind [5]. With a distance of 2300 miles to travel, a heavy-duty conductor such as copper was required to ensure that the signals traveled efficiently. An astounding 107 pounds of copper was used for each mile of cable, totaling 246,100 pounds of copper for the 2300 mile cable [1]. With the conductor in place, the next obstacle was to create the optimal insulation. At the time, guttapercha, a rubber-like substance extracted from the sap of the gutta-percha tree, had proven to be a great insulator [6]. This substance, when heated to 150 C, could be easily molded into any shape desired [7]. Once cooled, it was very flexible and strong. Above all, unlike rubber, instead of deteriorating in sea-water, gutta-percha thrived in it [8]. It is interesting to note that this great material is virtually unknown today and is used mainly in the field of dentistry to backfill cavities [8]. Traveling Signals: In order to insure that the signal would travel the great distance successfully, engineers had to determine how much time was needed to recharge the capacitor that released charge into the cable for every telegraphic pulse. For this, engineers relied on Lord Kelvin s distance squared Page 5 of 13

6 law for cable transmission. The law states that the time needed for the recharging of the capacitor is proportional to Resistance x Capacitance per unit length squared [1]. To put this into better perspective, we can apply Ohm s law and capacitance law to the equation as follows: Eq1: Distance squared law: t = rcl 2 Eq2: Ohm s law: v=ir r = v/i Eq3: Capacitance law: c =Q/v where t = time for recharging capacitor r = resistance c = capacitance L= length v = voltage i = current Q = Charge To make the substitutions with Eq1 and Eq2: t = (v/i)cl 2 To substitute further with Eq3: t = (v/i)(q/v)l 2 When we simplify (cancel v s): t = (Q/i)L 2 The final equation we obtain is therefore a version of Kelvin s Distance Squared Law in terms of charge (Q) and current (i). In this equation, length (L), which is the length of the cable itself, and charge (Q) are always constants. Therefore the only variable that can potentially effect the time for recharging capacitor is current (i). We can see based on the equation that if we increase current (i), time for recharging capacitor (t) will decrease; meaning that signal will reach its destination at a shorter time because capacitor will need less time to recharge and will be ready to release the charge. Next, we need to look at how exactly we can increase current. For this, we look at Ohm s Law (Eq2) v=ir i=v/r. Here, resistance (r) will always be a constant. Therefore in order to increase current (i) we must increase voltage (v). The final result obtained is: In order to recharge the capacitor faster, voltage needs to be high. The higher the voltage, the faster the capacitor will recharge and the faster the signals will be able to travel across the cable. Equation 1: Lord Kelvin s distance squared law and Ohm s law [1]. Page 6 of 13

7 During the initial development phase, it was estimated that 500 volts of electricity would be sufficient to transmit the signal across the Atlantic. However after more experimentation, it was concluded that a voltage of 60 would be adequate [8]. To provide the necessary power, engineers relied on a series of batteries. This included stacks of lead and acid cells as well as more complex plate and electrolyte combinations known as the voltaic pile [8]. As a side note, an electrolyte is any chemical compound that ionizes when dissolved to produce an electrically conductive medium [9]. This combination, created about 50 years prior by Alessandro Volta, was comprised of stacks of alternating copper and zinc disks. These disks were separated by a layer of electrolyte made up of saltwater [10]. Transatlantic Journey: With such a colossal cable, a powerful and equally colossal ship would be required to transport it. With the technology of the late 1800 s, there was no such ship that could carry the 2300 mile cable in its entirety. What the engineers decided would be the best solution was to split the cable in half. The United States and Britain would each construct half of the cable. Ships from both ends of the Atlantic would carry each half to be connected at the midpoint of the route [3]. The idea was feasible enough, however, engineers needed to ensure that the cable would be connected uniformly, without any seams, to prevent breakage if it came in contact with a strong enough force. This became possible due to the unique clay-like properties of gutta-percha. With a melting point of 150 C, it was easy enough to melt the substance, shape it around the seam, and mold it to create a continuous layer of insulation [8]. Page 7 of 13

8 Problems? With such a well thought out plan, why is it that the first attempt for transatlantic communication failed miserably on September 18, 1858? The answer is very simple; there wasn t enough knowledge of electricity at the time. Knowledge of electricity or electronics, as it was known at the time, was very limited in the late 1800 s. This combined with the fact that the chief technical advisor for the transatlantic cable, Edward Orange Wildman Whitehouse, was only a physician who possessed the knowledge on electricity by teaching himself through the years, led to the failure of the first attempt in transatlantic communication [2, 6]. The first problem arose when it took 11 days for a message to travel through the cable to the United States. As a solution, Whitehouse increased the number of batteries used to operate the cable, hence increasing the voltage to 2000 volts [8]. He believed that with such a long distance to travel, the signal needed a jump-start in order to travel faster and more efficiently. Based on the simple derivation of the time to charge capacitor equation provided above in equation 1, we can see how he came to that conclusion; the higher the voltage, the faster the capacitor would charge and could send a signal across the wire. Looking at this in hindsight, anyone with basic knowledge of Ohm s law can quickly understand why this solution did not work. According to Ohm s law, voltage = Current x Resistance. Due to a constant number of copper strands, the resistance of the cable was constant and Figure 3: Ohm s law was approximately 3 Ohm/nautical mile [1]. As he increased the voltage, current traveling though the cable increased as well. An increase in current Page 8 of 13

9 meant that more electrons were passing though the cable at any given time. The increased number of electrons generated more energy which was converted to heat and eventually melted the cable from the inside. Second Round of Celebrations: In the next few years, the British government set up an official panel to investigate the reasons behind the failure of the cable. On April 1861, the panel published a report that clearly blamed the manufacturing in the copper core and insulation for the failure of the project [1]. The panel also blamed Dr. Wildman Whitehouse, for having Figure 5: Shallow and deep water versions of 1865 Cable [1]. tried to speed up the transmission by an increase in the voltage as the cable worsened. After some research and field trials, the committee released a report in 1863, which recommended feasible improvements in manufacture, handling, and design of the cable. This meant an increase in the copper wires that would withstand the voltage passing through it. Where originally the weight of the copper conductor was 107 pounds per mile of wire, it was now up to 300 pounds per mile [1]. The end result, a 2300 mile cable consisting of seven strands of copper and four layers of gutta-percha Figure 4: The Great Eastern [1]. Page 9 of 13

10 weighing 5000 tons [1, 8]. This new cable was both heavier and bulkier. Also, transporting it via two ships was not viable anymore due to the increase in size. To solve this problem, a new ship, which was five to six times the size of any other ship built, was bought. The Great Eastern, as the ship was called, was capable of transporting 4000 passengers around the world without refueling [1]. Since operating it was really costly, even with tickets purchased by 4000 passengers, the company was going bankrupt; which meant that the Atlantic Telegraph Cable Company was able to purchase it for two percent of what it had cost to build it [4]. With everything in order, 20 miles a day, 2300 miles of cable weighting 5000 tones were loaded in three tanks abroad the Great Eastern [1]. Additionally, while transporting the cable to the other end of the Atlantic, telegraphic messages were continuously sent from the ship to mainland in order to ensure that the signals were being transported. By doing so, if anything was to happen with the cable, engineers could figure out where in the transportation process the problem had occurred [4]. Another major improvement to this new cable was being able to detect even the faintest signals transmitted through it. For this, scientists turned to Kelvin s Galvanometer. This was a simple contraption made of the telegraph wire, a kerosene lamp and a mirror. By attaching a mirror to the wire and focusing the flame on the mirror, even the slightest movement of the wire could be visible. This ingenious device could detect signals 1000 times fainter than any other device that was around during that time [4]. Page 10 of 13

11 A Pioneering Technology: The Transatlantic Telegraph Cable became the pioneer in international communication. In 1870, four years after the successful voyage, with the participation and help of the Great Eastern, an all-sea cable route to India was completed. In the year after, another voyage was set out which enabled the telegraph network to extend out to the Empire in the Far East and eventually to Australia. Later, in 1866, Florida and Cuba were connected. In 1874, using a 5386 km long wire via the Cape Verde Islands, Portugal and Brazil were connected as well [1]. Not only did the number of cables across the globe increase, but also their speeds increased too. The original cable was very slow and it was only able to transmit a few words per hour. The 1866 cable was a bigger improvement and was able to transmit 6-8 words per minute. In the later decades, with Oliver Heaviside s development of the transmission line theory and the telegrapher s equation, great improvements were made to the speed of the transmission [1]. In 1928, with all these new theories, equations, and the right kind of materials such as an improved loading using a nickel-iron magnetic alloy, an improved insulation, and automatic transmitting and receiving equipment, a 400 per minute message was able to easily transmit between two sources [1]. With the development of cable technology, it was time to solve a new problem; transmitting speech across the Atlantic. In 1901, Guglielmo Marconi, the father of long distance radio transmission, accomplished the first transatlantic speech transmission. This resulted in radio transmission being continually developed. However, due to technical problems and worldwide catastrophes, it was not until 100 years after the first telegraph message that transatlantic telephone cable service was developed. It is important to note that submarine cables still played a major role in communication as radio bands were unstable because of seasonal and daily variations [1]. Page 11 of 13

12 Conclusion: The successful transportation and usage of the Transatlantic Telegraph Cable not only proved to be a great business venture, it also became the pioneering technology for modern worldwide communication. Through the trials and errors made during the process of establishing transatlantic communication, mankind developed some of the core laws for electromagnetics. This in turn made it easier and more feasible to create better communication channels which would eventually lead to wireless communication. Page 12 of 13

13 References [1] Schwartz, M.; Hayes, J., "A history of transatlantic cables." Communications Magazine, IEEE, vol.46, no.9, pp.42-48, September [2] Cookson, G. The TransAtlantic telegraph cable: Eighth wonder of the world. History Today, vol. 50, no. 3, pp , March [3] Bowers, Brian, The first Atlantic telegraphs." Proceedings of the IEEE, vol. 88, no. 7, pp , July [4] Public Broadcasting Service (PBS). The Great Transatlantic Cable. Internet: November 30, 2004 [March 6, 2013]. [5] Giancoli, Douglas. Electric Currents and Resistance, in Physics for Scientists and Engineers with Modern Physics, 4th ed., Upper Saddle River, New Jersey: Prentice Hall, 2007, pp [6] Schils, René. How James Watt Invented the Copier. New York, NY: Springer New York, 2012, pp [7] DiaDent Group Int l. Inc. Diadent Gutta Percha - Root Canal Filling Material - Material Safety Data Sheet. Internet: July 1, 2009 [March 26, 2013]. [8] Woods, Robert O. "A Cable to Shrink the Earth." Mechanical Engineering, vol. 133, no. 1, pp , Jan [9] The Free Dictionary by Farlex. Electrolyte. Internet: [March 27, 2013]. [10] Routledge, Robert. A popular history of science. California: University of California Libraries, 1881, pp Page 13 of 13