8
ON DISTRIBUTED COMMUNICATIONS
Real wires take up room.
—W. DANIEL HILLIS1
The latest developments in telecommunications are all-optical data networks. So were the first. The recorded history of high-speed optical data transmission began with the fall of Troy to the Mycenaean army, allegedly in 1184 B.C. Across the Aegean in Mycenae, as legend has it, Clytaemnestra awaited news from her husband, Agamemnon, absent for ten years in the course of the siege. When Troy was taken, a prearranged signal was relayed overnight to Mycenae, via a line of fire beacons, a distance of some 375 miles, much of it over sea. The tragedy of Agamemnon, chronicled by Aeschylus (525–456 B.C.), opens with Clytaemnestra receiving news of the signal from her watchman while the chorus asks: “And what messenger is there that could arrive with such speed as this?”
Clytaemnestra answers: “Hephaistos [God of fire], sending forth from Ida a bright radiance. And beacon ever sent beacon hither by means of the courier fire: Ida (sent it) to the rock of Hermes in Lemnos; and a huge torch from the island was taken over in the third place by Zeus’ peak of Athos; and paying more than what was due, so as to skim the back of the sea . . . transmitting, like a sun, its golden radiance to the look-out of Makistos. And he, not dallying nor heedlessly overcome by sleep, did not neglect his share in the messenger’s duty, and afar, over the streams of Euripus, the beacon’s light gave the watchers of Messapion the sign of its arrival. They kindled an answering flare and sent the tidings onward, by setting fire to a stack of aged heath. And the vigorous torch, not yet growing dim, leaped, like the shining moon, over the plain of Asopus to the rock of Kithairon and there waked a new relay of the sender fire. And the far-sent light . . . shot down over the Gorgon-eyed lake and reaching the mountain of the roaming goats. . . . And they with stintless might kindled and sent on a great beard of flame, and it passed beyond the promontory that looks down on the Saronic straits, blazing onward, and shot down when it reached the Arachnaean peak, the watch-post that is neighbour to our city; and then it shot down here to the house of the Atridae, this light, the genuine offspring of its ancestor, the fire from Mount Ida . . . transmitted to me by my husband from Troy.”2
The link between Troy and Mycenae was a one-way, one-time, and one-bit channel, encoded as follows: no signal meant Troy belonged to the Trojans; a visible signal meant Troy belonged to the Greeks. Communications engineers have been improving the bandwidth ever since. Suffering a fate that still afflicts brief messages after three thousand years, Clytaemnestra’s message acquired a header—a cumulative listing of gateways that handled the message along the way—longer than the message she received.
A thousand years later, the Greek historian Polybius (ca. 200–118 B.C.) reported how torch telegraphy had been improved. “The most recent method, devised by Cleoxenus and Democleitus and perfected by myself, is quite definite and capable of dispatching with accuracy every kind of urgent message.” The key was to “take the alphabet and divide it into five parts, each consisting of five letters.” These five divisions of the twenty-four-letter Greek alphabet were inscribed on five tablets. The transmitting station, after signaling and receiving acknowledgment of the beginning of a transmission by raising two torches, “will now raise the first set of torches on the left side indicating which tablet is to be consulted, i.e., one torch if it is the first, two if it is the second, and so on. Next he will raise the second set on the right on the same principle to indicate what letter of the alphabet the receiver should write down.”3 It would be another two thousand years before modern telegraphy instituted a digital coding of the alphabet as concise and unambiguous as this.
In the seventeenth century, the 5-bit ciphers invented by Francis Bacon were elaborated by John Wilkins (1614–1672) in a treatise on cryptography, binary coding, and telecommunications titled Mercury, or the Secret and Swift messenger: Shewing, How a Man may with Privacy and Speed communicate his Thoughts to a Friend at any distance, published in 1641. Wilkins, who founded the “Experimentall Philosophicall Clubbe” at Oxford in 1649, married Oliver Cromwell’s sister in 1656. He was appointed master of Trinity College, Cambridge, in 1659, first secretary of the Royal Society in 1662, and bishop of Chester in 1668.
Wilkins noted that “two letters of the alphabet, being transposed through five places, will yield thirty-two differences, and so will more than serve for the foure and twenty letters unto which they may be thus applyed.”4 After showing how this 5-bit binary coding could be conveyed by torch signals and enciphered in numerous ingenious ways, Wilkins described how to transmit alphabetic text as a sequence of binary acoustic signals, anticipating the modern use of binary coding to transmit text-based intelligence, .and to feed the acoustic delay-line storage that gave the stored-program computer industry its start. “It is requisite, that there be two Bels of different notes, or some such other audible and loud sounds, which we may command at pleasure,” wrote Wilkins. “By the various soundes of these (according to the former table) a man may easily espresse any letter and so consequently any sense.”5
Two distinct functions are required of a successful telegraphic code: the encoding of protocols that regulate the process of communication, and the encoding of symbols representing the message to be conveyed. Meaning—in telegraphy as in biology—is encoded hierarchically: first by mapping elementary symbols to some kind of alphabet, then by mapping this alphabet to words, phrases, standard messages, and anything else that can be expressed by brief sequences of code. Higher levels of meaning arise as further layers of interpretation evolve. Protocols, or handshaking, initiate the beginning and end of a transmission and may be used to coordinate error correction and flow control. As Gerard Holzmann and Björn Pehrson observed in their definitive Early History of Data Networks, “Some type of protocol has to be established between sender and receiver to deal minimally with the basic problems of synchronization (‘after you,’ ‘no, after you!’), visibility (‘repeat please’), and transmission speed (‘not so fast!’).”6
Telecommunications systems have appeared, disappeared, and reappeared across the centuries: fire beacons, heliographs, and primitive forms of semaphore based on hanging or waving anything from flags to lanterns in the air. When the Spanish armada entered the English Channel in July 1588, a network of fire beacons raised the alarm, cradling the newborn Thomas Hobbes with fear. The invention of the telescope in the early seventeenth century extended the distance between relay stations and allowed more complex symbols to be distinguished. The feasibility of a “method of discoursing at a Distance, not by Sound, but by Sight” was addressed by Robert Hooke in a lecture, “Shewing a Way how to communicate one’s Mind at great Distances,” delivered to the Royal Society on 21 May 1684. Having advanced the optical instruments of his day, Hooke showed that “‘tis possible to convey Intelligence from any one high and eminent Place, to any other that lies in Sight of it, tho’ 30 or 40 Miles distant, in as short a Time almost, as a Man can write what he would have sent, and as suddenly to receive an Answer as he that receives it hath a Mind to return it. . . . Nay, by the Help of three, four, or more such eminent Places, visible to each other . . . ‘tis possible to convey Intelligence, almost in a Moment, to twice, thrice, or more Times that Distance, with as great a Certainty as by Writing.”7
Robert Hooke (1635–1703) was a brilliant but difficult character whose “temper was Melancholy, Mistrustful and Jealous, which more increas’d upon him with his Years.”8 Possessed of “indefatigable Genius,” his creative output was astounding, despite ill humor and ill health. “He is of prodigious inventive head,” reported his contemporary John Aubrey, adding that “now when I have sayd his Inventive faculty is so great, you cannot imagine his Memory to be excellent, for they are like two Bucketts, as one goes up, the other goes downe. He is certainly the greatest Mechanick this day in the world.”9 In 1655, Hooke was appointed assistant to Robert Boyle, executing the construction of Boyle’s air pump or pneumatic engine with an in
genuity that descended directly, via Thomas Newcomen’s atmospheric engine, to the steam engines of the Industrial Revolution and thence to all internal combustion engines in circulation today. After a meeting of the Royal Society on 15 February 1664 (adjourned to the Crown Tavern until ten o’clock that night), Samuel Pepys noted in his diary that “Above all, Mr. Boyle was at the meeting, and above him Mr. Hooke, who is the most, and promises the least, of any man in the world that ever I saw.”10
In November 1662, Newton, Boyle, and others on the Royal Society’s Council established the position of curator of experiments “and order’d that Mr Hooke should come and sit among them, and both bring in every Day three or four of his own Experiments, and take care of such others as should be recommended to him.”11 The ensuing thirty-six years of experimental research were interrupted only by a brief recess during the worst months of the plague in 1665, followed by a period of distraction after the great fire of 1666, when Hooke was commissioned to help survey the City of London so that property could be rebuilt. He was paid handsomely by the landowners, but continued to live penuriously, “as was evident by a large Iron Chest of Money found after his Death, which had been lock’d down with the Key in it, with a date of the Time, by which it appear’d to have been so shut up for above thirty Years.”12
Hooke’s pendulum clock escapement saw universal use, as did countless other inventions of his, including the universal joint, that have helped our world go round smoothly ever since. His mechanism for regulating pocket watches and chronometers, based on the oscillation of a delicately coiled spring, regulated industry, commerce, and navigation for the next three hundred years. Although Hooke did not invent the microscope, he greatly improved it, and with the publication of his Micrographia in 1665, he established the cellular structure of living organisms and otherwise defined the field. He dabbled as an architect, designing the buildings that housed the Royal Society, the College of Physicians, the British Museum, and the Hospital of St. Mary of Bethlehem, or Bedlam. He is remembered for Hooke’s law of elasticity and forgotten as the discoverer of the optical interference patterns known as Newton’s rings.
When new inventions were presented to the Royal Society, Hooke either claimed to have invented them earlier or showed how they could be improved. When Leibniz exhibited a calculating machine in January 1673, Hooke complained, “it seemed to me so complicated with wheels, pinions, cantrights, springs, screws, stops, and truckles, that I could not perceive it ever to be of any great use. . . . It could only be fit for great persons to purchase, and for great force to remove and manage, and for great wits to understand and comprehend.” In contrast, Hooke announced that “I have an instrument now making, which will perform the same effects [and] will not have a tenth part of the number of parts, and not take up a twentieth part of the room.”13 The record shows that on 5 March 1673, “he produced his arithmetical engine, mentioned by him in the meeting of February 5, and showed the manner of its operation, which was applauded.” But Hooke’s invention “whereby in large numbers, for multiplication or division, one man may be able to do more than twenty by the common way of working arithmetic” remained as sparsely documented as his spring-powered model representing one of some thirty different envisioned species of flying machines. The arithmetic engine was listed among the artificial rarities in the collection of Gresham College in 1681, and thereafter disappeared.
Hooke neglected most opportunities to reap reward. “Whether this mistake resulted from the multiplicity of his Business which did not allow him a sufficient time,” wrote Richard Waller, “or from the fertility of his Invention which hurried him on, neglecting the former Discoveries . . . tho’ there wanted some small matter to render their use more practicable and general, I know not.”14 If anyone could be said to have thought of everything, it was Hooke. He developed a philosophical algebra by which to grasp multiple avenues of thought at a single time, making it inevitable, even without unscrupulous behavior on the part of some of his colleagues, that competitors would appear to be taking credit for his ideas. His contributions included a theory of gravitation and celestial mechanics, of which, said Aubrey, “Mr. Newton haz made a demonstration, not at all owning he receiv’d the first Intimation of it from Mr. Hooke.” Eventually, Hooke grew bitter over both real and perceived expropriations of his work and revealed many of his later inventions only in the form of cryptic anagrams, carrying the details with him to his grave. “I wish he had writt plainer, and afforded a little more paper,” was Aubrey’s chief complaint.15
Hooke was acquainted with the elder Thomas Hobbes, but “found him to lard and seal every asseveration with a round oath, to undervalue all other men’s opinions and judgments, to defend to the utmost what he asserted though never so absurd.”16 Their destinies were intertwined: it was Hooke’s concept of long-distance communication that would bring Hobbes’s Leviathan to life. Although Hooke did not go as far as Hobbes in assigning a material existence to the soul, he speculated more precisely on the physical operation of the mind.
The mystery, to Hooke, was not that we are able to perceive, remember, and generate new concepts from one moment to the next, but how the mind keeps track of temporal sequence while preserving random access to its store of memories and ideas. Hooke’s solution—like the mechanism he developed for the regulation of chronometers—took the form of a coiled spring: “There is as it were a continued Chain of Ideas coyled up in the Repository of the Brain, the first end of which is farthest removed from the Center or Seat of the Soul where the Ideas are formed, which is always the Moment present when considered: And therefore according as there are a greater number of [layers of] these Ideas between the present Sensation or Thought in the Center, and any other, the more is the Soul apprehensive of the Time interposed.”17
To estimate the storage capacity of the human brain, Hooke calculated the number of thoughts that could be registered per second, hour, day, year, and lifetime—“to take a round sum but 21 hundred Millions.” He reduced to 100 million the number that the average person might remember, who “consequently must have as many distinct Ideas.” Hooke then drew on his firsthand observations of microorganisms to argue that this many ideas might easily fit inside the brain: “I see no Reason why all these may not actually be contained within the Sphere of Activity of the Soul. . . . For if we consider in how small a bulk of Body there may be as many distinct living creatures as are here supposed Ideas, and every of these Creatures perfectly formed and endued with all its Vegetative and Animal Functions, and with sufficient room also left for it to move it self to and fro among and between all the rest . . . we shall not need to fear any Impossibility to find out room in the Brain.”18
As early as 17 February 1664 the Royal Society urged “that Mr. Hooke set down in writing and produce to the Council his whole apparatus and management for speedy intelligence,”19 but nothing was forthcoming until 29 February 1672, when “he proposed a way for a very speedy conveyance of intelligence from place to place by the sight assisted with telescopes, to be employed on high places, by the correspondents using a secret character. . . . The paper of this proposition, and the particulars of the manner of practising it, were read, but not left by Mr. Hooke to be registered, but taken away by him.”20 The council ordered “that some experiment should be made of this proposition at the next meeting,” and on 7 March a test was conducted across the Thames. “The contrivance was applauded as very ingenious . . . [but] the President objected, that the use of it would be often hindered by hazy weather.”21
In a disclosure that was finally delivered and recorded in 1684, Hooke prescribed an alphabet of twenty-four symbols, constructed of thin wood and rigged via pulleys and control lines so as to be exposed as required from behind an elevated wooden screen. “By these Contrivances, the Characters may be shifted almost as fast, as the same may be written; so that a great Quantity of Intelligence may be, in a very short Time, communicated.”22 For nighttime use, Hooke proposed a 2 × 5 array of lanterns “d
isposed in a certain Order, which may be veiled, or discovered, according to the Method of the Character agreed on; by which, all Sorts of Letters may be discovered clearly, and without Ambiguity,”23 foreshadowing the shutter telegraphs that would be instituted by the British Admiralty in another hundred years. Finally, confirming the intimate association between telecommunications and cryptography, Hooke noted that by “cruptography” (as he spelled it) the arbitrary mapping between symbols and letters permits “the whole alphabet [to] be varied 10,000 ways; so that none but the two extreme correspondents shall be able to discover the information conveyed.”24
Hooke specified single-character control codes to be displayed above the message area during transmission, providing eleven examples of these out-of-band signals, of which Holzmann and Pehrson noted that “at least eight are control codes that can be found in most modern data communication protocols, and some of these (i.e., the rate control codes) only in the most recent designs.”25 Hooke confidently predicted that “things may be made so convenient, that the same Character may be seen at Paris, within a Minute after it hath been exposed at London, and the like in Proportion for greater Distances; and that the Characters may be exposed so quick after one another, that a Composer shall not much exceed the Exposer in Swiftness.”26
By the end of the next century, optical telegraph networks spanned most of Europe, led by a system constructed by Claude and Abraham Chappe in France. In 1801, with designs on England, Napoléon commissioned an optical telegraph able to span the English Channel; when tested over equivalent distances, it worked. Claude Chappe (1763–1805) had attempted to construct an electric telegraph in 1790, but soon abandoned electricity in favor of optical signals relayed by mechanical display. The French Revolution was in full swing. The new government was open to new ideas, but Chappe’s prototype installation was destroyed twice by revolutionary mobs who suspected it was a device for communicating with the imprisoned Louis XVI. Chappe’s network, inaugurated by a 130-mile line between Paris and Lille in 1794, reached a total length of approximately 3,000 miles, staffed by some three thousand operators at 556 stations, in 1852. Stations were about 6 miles apart. Signals could be relayed in a few seconds, but the lines ran much slower in practice, with actual throughput about two signals per minute or less. Transit over the 475 miles and 120 stations from Paris to Toulon (on the Mediterranean) took “10 or 12 minutes” if the weather was clear. Messages were encrypted against interception or adulteration en route.
Darwin Among the Machines Page 19