Compact disc

Compact disc The invention: A plastic disk on which digitized music or computer data is stored. The people behind the invention: Akio Morita (1921- ), a Japanese physicist and engineer who was a cofounder of Sony Wisse Dekker (1924- ), a Dutch businessman who led the Philips company W. R. Bennett (1904-1983), an American engineer who was a pioneer in digital communications and who played an important part in the Bell Laboratories research program Digital Recording The digital system of sound recording, like the analog methods that preceded it, was developed by the telephone companies to improve the quality and speed of telephone transmissions. The system of electrical recording introduced by Bell Laboratories in the 1920s was part of this effort. Even Edison’s famous invention of the phonograph in 1877 was originally conceived as an accompaniment to the telephone. Although developed within the framework of telephone communications, these innovations found wide applications in the entertainment industry. The basis of the digital recording system was a technique of sampling the electrical waveforms of sound called PCM, or pulse code modulation. PCM measures the characteristics of these waves and converts them into numbers. This technique was developed at Bell Laboratories in the 1930’s to transmit speech. At the end of World War II, engineers of the Bell System began to adaptPCMtechnology for ordinary telephone communications. The problem of turning sound waves into numbers was that of finding a method that could quickly and reliably manipulate millions of them. The answer to this problem was found in electronic computers, which used binary code to handle millions of computations in a few seconds. The rapid advance of computer technology and the semiconductor circuits that gave computers the power to handle complex calculations provided the means to bring digital sound technology into commercial use. In the 1960’s, digital transmission and switching systems were introduced to the telephone network. Pulse coded modulation of audio signals into digital code achieved standards of reproduction that exceeded even the best analog system, creating an enormous dynamic range of sounds with no distortion or background noise. The importance of digital recording went beyond the transmission of sound because it could be applied to all types of magnetic recording in which the source signal is transformed into an electric current. There were numerous commercial applications for such a system, and several companies began to explore the possibilities of digital recording in the 1970’s. Researchers at the Sony, Matsushita, and Mitsubishi electronics companies in Japan produced experimental digital recording systems. Each developed its own PCM processor, an integrated circuit that changes audio signals into digital code. It does not continuously transform sound but instead samples it by analyzing thousands of minute slices of it per second. Sony’s PCM-F1 was the first analog-to-digital conversion chip to be produced. This gave Sony a lead in the research into and development of digital recording. All three companies had strong interests in both audio and video electronics equipment and saw digital recording as a key technology because it could deal with both types of information simultaneously. They devised recorders for use in their manufacturing operations. After using PCM techniques to turn sound into digital code, they recorded this information onto tape, using not magnetic audio tape but the more advanced video tape, which could handle much more information. The experiments with digital recording occurred simultaneously with the accelerated development of video recording technology and owed much to the enhanced capabilities of video recorders. At this time, videocassette recorders were being developed in several corporate laboratories in Japan and Europe. The Sony Corporation was one of the companies developing video recorders at this time. Its U-matic machines were successfully used to record digitally. In 1972, the Nippon Columbia Company began to make its master recordings digitally on an Ampex video recording machine. Links Among New Technologies There were powerful links between the new sound recording systems and the emerging technologies of storing and retrieving video images. The television had proved to be the most widely used and profitable electronic product of the 1950’s, but with the market for color television saturated by the end of the 1960’s, manufacturers had to look for a replacement product.Amachine to save and replay television images was seen as the ideal companion to the family TV set. The great consumer electronics companies—General Electric and RCAin the United States, Philips and Telefunken in Europe, and Sony and Matsushita in Japan—began experimental programs to find a way to save video images. RCA’s experimental teams took the lead in developing an optical videodisc system, called Selectavision, that used an electronic stylus to read changes in capacitance on the disc. The greatest challenge to them came from the Philips company of Holland. Its optical videodisc used a laser beam to read information on a revolving disc, in which a layer of plastic contained coded information. With the aid of the engineering department of the Deutsche Grammophon record company, Philips had an experimental laser disc in hand by 1964. The Philips Laservision videodisc was not a commercial success, but it carried forward an important idea. The research and engineering work carried out in the laboratories at Eindhoven in Holland proved that the laser reader could do the job. More important, Philips engineers had found that this fragile device could be mass produced as a cheap and reliable component of a commercial product. The laser optical decoder was applied to reading the binary codes of digital sound. By the end of the 1970’s, Philips engineers had produced a working system. Ten years of experimental work on the Laservision system proved to be a valuable investment for the Philips corporation. Around 1979, it started to work on a digital audio disc (DAD) playback system. This involved more than the basic idea of converting the output of the PCM conversion chip onto a disc. The lines of pits on the compact disc carry a great amount of information: the left- and right-hand tracks of the stereo system are identified, and a sequence of pits also controls the motor speed and corrects any error in the laser reading of the binary codes. This research was carried out jointly with the Sony Corporation of Japan, which had produced a superior method of encoding digital sound with its PCM chips. The binary codes that carried the information were manipulated by Sony’s sixteen-bit microprocessor. Its PCM chip for analog-to-digital conversion was also employed. Together, Philips and Sony produced a commercial digital playback record that they named the compact disc. The name is significant, as it does more than indicate the size of the disc—it indicates family ties with the highly successful compact cassette. Philips and Sony had already worked to establish this standard in the magnetic tape format and aimed to make their compact disc the standard for digital sound reproduction.Philips and Sony began to demonstrate their compact digital disc (CD) system to representatives of the audio industry in 1981. They were not alone in digital recording. The Japanese Victor Company, a subsidiary of Matsushita, had developed a version of digital recording from its VHD video disc design. It was called audio high density disc (AHD). Instead of the small CD disc, the AHD system used a ten-inch vinyl disc. Each digital recording system used a different PCM chip with a different rate of sampling the audio signal.The recording and electronics industries’ decision to standardize on the Philips/ Sony CD system was therefore a major victory for these companies and an important event in the digital era of sound recording. Sony had found out the hard way that the technical performance of an innovation is irrelevant when compared with the politics of turning it into an industrywide standard. Although the pioneer in videocassette recorders, Sony had been beaten by its rival, Matsushita, in establishing the video recording standard. This mistake was not repeated in the digital standards negotiations, and many companies were persuaded to license the new technology. In 1982, the technology was announced to the public. The following year, the compact disc was on the market. The Apex of Sound Technology The compact disc represented the apex of recorded sound technology. Simply put, here at last was a system of recording in which there was no extraneous noise—no surface noise of scratches and pops, no tape hiss, no background hum—and no damage was done to the recording as it was played. In principle, a digital recording will last forever, and each play will sound as pure as the first. The compact disc could also play much longer than the vinyl record or long-playing cassette tape. Despite these obvious technical advantages, the commercial success of digital recording was not ensured. There had been several other advanced systems that had not fared well in the marketplace, and the conspicuous failure of quadrophonic sound in the 1970’s had not been forgotten within the industry of recorded sound. Historically, there were two key factors in the rapid acceptance of a new system of sound recording and reproduction: a library of prerecorded music to tempt the listener into adopting the system and a continual decrease in the price of the playing units to bring them within the budgets of more buyers. By 1984, there were about a thousand titles available on compact disc in the United States; that number had doubled by 1985. Although many of these selections were classical music—it was naturally assumed that audiophiles would be the first to buy digital equipment—popular music was well represented. The firstCDavailable for purchase was an album by popular entertainer Billy Joel. The first CD-playing units cost more than $1,000, but Akio Morita of Sony was determined that the company should reduce the price of players even if it meant selling them below cost. Sony’s audio engineering department improved the performance of the players while reducing size and cost. By 1984, Sony had a small CD unit on the market for $300. Several of Sony’s competitors, including Matsushita, had followed its lead into digital reproduction. There were several compact disc players available in 1985 that cost less than $500. Sony quickly applied digital technology to the popular personal stereo and to automobile sound systems. Sales of CD units increased roughly tenfold from 1983 to 1985. Impact on Vinyl Recording When the compact disc was announced in 1982, the vinyl record was the leading form of recorded sound, with 273 million units sold annually compared to 125 million prerecorded cassette tapes. The compact disc sold slowly, beginning with 800,000 units shipped in 1983 and rising to 53 million in 1986. By that time, the cassette tape had taken the lead, with slightly fewer than 350 million units. The vinyl record was in decline, with only about 110 million units shipped. Compact discs first outsold vinyl records in 1988. In the ten years from 1979 to 1988, the sales of vinyl records dropped nearly 80 percent. In 1989, CDs accounted for more than 286 million sales, but cassettes still led the field with total sales of 446 million. The compact disc finally passed the cassette in total sales in 1992, when more than 300 million CDs were shipped, an increase of 22 percent over the figure for 1991. The introduction of digital recording had an invigorating effect on the industry of recorded sound, which had been unable to fully recover from the slump of the late 1970’s. Sales of recorded music had stagnated in the early 1980’s, and an industry accustomed to steady increases in output became eager to find a new product or style of music to boost its sales. The compact disc was the product to revitalize the market for both recordings and players. During the 1980’s, worldwide sales of recorded music jumped from $12 billion to $22 billion, with about half of the sales volume accounted for by digital recordings by the end of the decade. The success of digital recording served in the long run to undermine the commercial viability of the compact disc. This was a playonly technology, like the vinyl record before it. Once users had become accustomed to the pristine digital sound, they clamored for digital recording capability. The alliance of Sony and Philips broke down in the search for a digital tape technology for home use. Sony produced a digital tape system calledDAT, while Philips responded with a digital version of its compact audio tape called DCC. Sony answered the challenge of DCC with its Mini Disc (MD) product, which can record and replay digitally. The versatility of digital recording has opened up a wide range of consumer products. Compact disc technology has been incorporated into the computer, in which CD-ROM readers convert the digital code of the disc into sound and images. Many home computers have the capability to record and replay sound digitally. Digital recording is the basis for interactive audio/video computer programs in which the user can interface with recorded sound and images. Philips has established a strong foothold in interactive digital technology with its CD-I (compact disc interactive) system, which was introduced in 1990. This acts as a multimedia entertainer, providing sound, moving images, games, and interactive sound and image publications such as encyclopedias. The future of digital recording will be broad-based systems that can record and replay a wide variety of sounds and images and that can be manipulated by users of home computers.

Community antenna television

The invention: 

Asystem for connecting households in isolated areas to common antennas to improve television reception, community antenna television was a forerunner of modern cabletelevision systems.

The people behind the invention: 

Robert J. Tarlton, the founder of CATV in eastern Pennsylvania
Ed Parsons, the founder of CATV in Oregon
Ted Turner (1938- ), founder of the first cable superstation,WTBS

Communications satellite

The invention: Telstar I, the world’s first commercial communications satellite, opened the age of live, worldwide television by connecting the United States and Europe. The people behind the invention: Arthur C. Clarke (1917- ), a British science-fiction writer who in 1945 first proposed the idea of using satellites as communications relays John R. Pierce (1910- ), an American engineer who worked on the Echo and Telstar satellite communications projects Science Fiction? In 1945, Arthur C. Clarke suggested that a satellite orbiting high above the earth could relay television signals between different stations on the ground, making for a much wider range of transmission than that of the usual ground-based systems. Writing in the February, 1945, issue of Wireless World, Clarke said that satellites “could give television and microwave coverage to the entire planet.” In 1956, John R. Pierce at the Bell Telephone Laboratories of the American Telephone & Telegraph Company (AT&T) began to urge the development of communications satellites. He saw these satellites as a replacement for the ocean-bottom cables then being used to carry transatlantic telephone calls. In 1950, about one-and-a-half million transatlantic calls were made, and that number was expected to grow to three million by 1960, straining the capacity of the existing cables; in 1970, twenty-one million calls were made. Communications satellites offered a good, cost-effective alternative to building more transatlantic telephone cables. On January 19, 1961, the Federal Communications Commission (FCC) gave permission for AT&T to begin Project Telstar, the first commercial communications satellite bridging the Atlantic Ocean.AT&T reached an agreement with the National Aeronautics and Space Administration (NASA) in July, 1961, in which AT&T would pay $3 million for each Telstar launch. The Telstar project involved about four hundred scientists, engineers, and technicians at the Bell Telephone Laboratories, twenty more technical personnel at AT&T headquarters, and the efforts of more than eight hundred other companies that provided equipment or services. Telstar 1 was shaped like a faceted sphere, was 88 centimeters in diameter, and weighed 80 kilograms. Most of its exterior surface (sixty of the seventy-four facets) was covered by 3,600 solar cells to convert sunlight into 15 watts of electricity to power the satellite. Each solar cell was covered with artificial sapphire to reduce the damage caused by radiation. The main instrument was a two-way radio able to handle six hundred telephone calls at a time or one television channel. The signal that the radio would send back to Earth was very weak—less than one-thirtieth the energy used by a household light bulb. Large ground antennas were needed to receive Telstar’s faint signal. The main ground station was built by AT&T in Andover, Maine, on a hilltop informally called “Space Hill.” A horn-shaped antenna, weighing 380 tons, with a length of 54 meters and an open end with an area of 1,097 square meters, was mounted so that it could rotate to track Telstar across the sky. To protect it from wind and weather, the antenna was built inside an inflated dome, 64 meters in diameter and 49 meters tall. It was, at the time, the largest inflatable structure ever built. A second, smaller horn antenna in Holmdel, New Jersey, was also used.International Cooperation In February, 1961, the governments of the United States and England agreed to let the British Post Office and NASAwork together to test experimental communications satellites. The British Post Office built a 26-meter-diameter steerable dish antenna of its own design at Goonhilly Downs, near Cornwall, England. Under a similar agreement, the French National Center for Telecommunications Studies constructed a ground station, almost identical to the Andover station, at Pleumeur-Bodou, Brittany, France. After testing, Telstar 1 was moved to Cape Canaveral, Florida, and attached to the Thor-Delta launch vehicle built by the Douglas Aircraft Company. The Thor-Delta was launched at 3:35 a.m. eastern standard time (EST) on July 10, 1962. Once in orbit, Telstar 1 took 157.8 minutes to circle the globe. The satellite came within range of the Andover station on its sixth orbit, and a television test pattern was transmitted to the satellite at 6:26 p.m. EST. At 6:30 p.m. EST, a tape-recorded black-and-white image of the American flag with the Andover station in the background, transmitted from Andover to Holmdel, opened the first television show ever broadcast by satellite. Live pictures of U.S. vice president Lyndon B. Johnson and other officials gathered at Carnegie Institution inWashington, D.C., followed on the AT&T program carried live on all three American networks. Up to the moment of launch, it was uncertain if the French station would be completed in time to participate in the initial test. At 6:47 p.m. EST, however, Telstar’s signal was picked up by the station in Pleumeur-Bodou, and Johnson’s image became the first television transmission to cross the Atlantic. Pictures received at the French station were reported to be so clear that they looked like they had been sent from only forty kilometers away. Because of technical difficulties, the English station was unable to receive a clear signal. The first formal exchange of programming between the United States and Europe occurred on July 23, 1962. This special eighteenminute program, produced by the European Broadcasting Union, consisted of live scenes from major cities throughout Europe and was transmitted from Goonhilly Downs, where the technical difficulties had been corrected, to Andover via Telstar. On the previous orbit, a program entitled “America, July 23, 1962,” showing scenes from fifty television cameras around the United States, was beamed from Andover to Pleumeur-Bodou and seen by an estimated one hundred million viewers throughout Europe.Consequences Telstar 1 and the communications satellites that followed it revolutionized the television news and sports industries. Before, television networks had to ship film across the oceans, meaning delays of hours or days between the time an event occurred and the broadcast of pictures of that event on television on another continent. Now, news of major significance, as well as sporting events, can be viewed live around the world. The impact on international relations also was significant, with world opinion becoming able to influence the actions of governments and individuals, since those actions could be seen around the world as the events were still in progress. More powerful launch vehicles allowed new satellites to be placed in geosynchronous orbits, circling the earth at a speed the same as the earth’s rotation rate. When viewed from the ground, these satellites appeared to remain stationary in the sky. This allowed continuous communications and greatly simplified the ground antenna system. By the late 1970’s, private individuals had built small antennas in their backyards to receive television signals directly from the satellites.

Colossus computer

The invention: The first all-electronic calculating device, the Colossus computer was built to decipher German military codes during World War II. The people behind the invention: Thomas H. Flowers, an electronics expert Max H. A. Newman (1897-1984), a mathematician Alan Mathison Turing (1912-1954), a mathematician C. E. Wynn-Williams, a member of the Telecommunications Research Establishment An Undercover Operation In 1939, during World War II (1939-1945), a team of scientists, mathematicians, and engineers met at Bletchley Park, outside London, to discuss the development of machines that would break the secret code used in Nazi military communications. The Germans were using a machine called “Enigma” to communicate in code between headquarters and field units. Polish scientists, however, had been able to examine a German Enigma and between 1928 and 1938 were able to break the codes by using electromechanical codebreaking machines called “bombas.” In 1938, the Germans made the Enigma more complicated, and the Polish were no longer able to break the codes. In 1939, the Polish machines and codebreaking knowledge passed to the British. Alan Mathison Turing was one of the mathematicians gathered at Bletchley Park to work on codebreaking machines. Turing was one of the first people to conceive of the universality of digital computers. He first mentioned the “Turing machine” in 1936 in an article published in the Proceedings of the London Mathematical Society. The Turing machine, a hypothetical device that can solve any problem that involves mathematical computation, is not restricted to only one task—hence the universality feature. Turing suggested an improvement to the Bletchley codebreaking machine, the “Bombe,” which had been modeled on the Polish bomba. This improvement increased the computing power of the machine. The new codebreaking machine replaced the tedious method of decoding by hand, which in addition to being slow, was ineffective in dealing with complicated encryptions that were changed daily. Building a Better Mousetrap The Bombe was very useful. In 1942, when the Germans started using a more sophisticated cipher machine known as the “Fish,” Max H. A. Newman, who was in charge of one subunit at Bletchley Park, believed that an automated device could be designed to break the codes produced by the Fish. Thomas H. Flowers, who was in charge of a switching group at the Post Office Research Station at Dollis Hill, had been approached to build a special-purpose electromechanical device for Bletchley Park in 1941. The device was not useful, and Flowers was assigned to other problems. Flowers began to work closely with Turing, Newman, and C. E. Wynn-Williams of the Telecommunications Research Establishment (TRE) to develop a machine that could break the Fish codes. The Dollis Hill team worked on the tape driving and reading problems, and Wynn-Williams’s team at TRE worked on electronic counters and the necessary circuitry. Their efforts produced the “Heath Robinson,” which could read two thousand characters per second. The Heath Robinson used vacuum tubes, an uncommon component in the early 1940’s. The vacuum tubes performed more reliably and rapidly than the relays that had been used for counters. Heath Robinson and the companion machines proved that high-speed electronic devices could successfully do cryptoanalytic work (solve decoding problems). Entirely automatic in operation once started, the Heath Robinson was put together at Bletchley Park in the spring of 1943. The Heath Robinson became obsolete for codebreaking shortly after it was put into use, so work began on a bigger, faster, and more powerful machine: the Colossus. Flowers led the team that designed and built the Colossus in eleven months at Dollis Hill. The first Colossus (Mark I) was a bigger, faster version of the Heath Robinson and read about five thousand characters per second. Colossus had approximately fifteen hundred vacuum tubes, which was the largest number that had ever been used at that time. Although Turing and Wynn-Williams were not directly involved with the design of the Colossus, their previous work on the Heath Robinson was crucial to the project, since the first Colossus was based on the Heath Robinson. Colossus became operational at Bletchley Park in December, 1943, and Flowers made arrangements for the manufacture of its components in case other machines were required. The request for additional machines came in March, 1944. The second Colossus, the Mark II, was extensively redesigned and was able to read twentyfive thousand characters per second because it was capable of performing parallel operations (carrying out several different operations at once, instead of one at a time); it also had a short-term memory. The Mark II went into operation on June 1, 1944. More machines were made, each with further modifications, until there were ten. The Colossus machines were special-purpose, programcontrolled electronic digital computers, the only known electronic programmable computers in existence in 1944. The use of electronics allowed for a tremendous increase in the internal speed of the machine. Impact The Colossus machines gave Britain the best codebreaking machines of World War II and provided information that was crucial for the Allied victory. The information decoded by Colossus, the actual messages, and their influence on military decisions would remain classified for decades after the war. The later work of several of the people involved with the Bletchley Park projects was important in British computer development after the war. Newman’s and Turing’s postwar careers were closely tied to emerging computer advances. Newman, who was interested in the impact of computers on mathematics, received a grant from the Royal Society in 1946 to establish a calculating machine laboratory at Manchester University. He was also involved with postwar computer growth in Britain. Several other members of the Bletchley Park team, including Turing, joined Newman at Manchester in 1948. Before going to Manchester University, however, Turing joined Britain’s National Physical Laboratory (NPL). At NPL, Turing worked on an advanced computer known as the Pilot Automatic Computing Engine (Pilot ACE). While at NPL, Turing proposed the concept of a stored program, which was a controversial but extremely important idea in computing. A“stored” program is one that remains in residence inside the computer, making it possible for a particular program and data to be fed through an input device simultaneously. (The Heath Robinson and Colossus machines were limited by utilizing separate input tapes, one for the program and one for the data to be analyzed.) Turing was among the first to explain the stored-program concept in print. He was also among the first to imagine how subroutines could be included in a program. (Asubroutine allows separate tasks within a large program to be done in distinct modules; in effect, it is a detour within a program. After the completion of the subroutine, the main program takes control again.)

Color television

The invention: 

System for broadcasting full-color images over the
airwaves.

The people behind the invention:

Peter Carl Goldmark (1906-1977), the head of the CBS research
and development laboratory
William S. Paley (1901-1990), the businessman who took over
CBS
David Sarnoff (1891-1971), the founder of RCA

Color film

The invention:Aphotographic medium used to take full-color pictures. The people behind the invention: Rudolf Fischer (1881-1957), a German chemist H. Siegrist (1885-1959), a German chemist and Fischer’s collaborator Benno Homolka (1877-1949), a German chemist The Process Begins Around the turn of the twentieth century, Arthur-Louis Ducos du Hauron, a French chemist and physicist, proposed a tripack (threelayer) process of film development in which three color negatives would be taken by means of superimposed films. This was a subtractive process. (In the “additive method” of making color pictures, the three colors are added in projection—that is, the colors are formed by the mixture of colored light of the three primary hues. In the “subtractive method,” the colors are produced by the superposition of prints.) In Ducos du Hauron’s process, the blue-light negative would be taken on the top film of the pack; a yellow filter below it would transmit the yellow light, which would reach a green-sensitive film and then fall upon the bottom of the pack, which would be sensitive to red light. Tripacks of this type were unsatisfactory, however, because the light became diffused in passing through the emulsion layers, so the green and red negatives were not sharp. To obtain the real advantage of a tripack, the three layers must be coated one over the other so that the distance between the bluesensitive and red-sensitive layers is a small fraction of a thousandth of an inch. Tripacks of this type were suggested by the early pioneers of color photography, who had the idea that the packs would be separated into three layers for development and printing. The manipulation of such systems proved to be very difficult in practice. It was also suggested, however, that it might be possible to develop such tripacks as a unit and then, by chemical treatment, convert the silver images into dye images.Fischer’s Theory One of the earliest subtractive tripack methods that seemed to hold great promise was that suggested by Rudolf Fischer in 1912. He proposed a tripack that would be made by coating three emulsions on top of one another; the lowest one would be red-sensitive, the middle one would be green-sensitive, and the top one would be bluesensitive. Chemical substances called “couplers,” which would produce dyes in the development process, would be incorporated into the layers. In this method, the molecules of the developing agent, after becoming oxidized by developing the silver image, would react with the unoxidized form (the coupler) to produce the dye image. The two types of developing agents described by Fischer are paraminophenol and paraphenylenediamine (or their derivatives). The five types of dye that Fischer discovered are formed when silver images are developed by these two developing agents in the presence of suitable couplers. The five classes of dye he used (indophenols, indoanilines, indamines, indothiophenols, and azomethines) were already known when Fischer did his work, but it was he who discovered that the photographic latent image could be used to promote their formulation from “coupler” and “developing agent.” The indoaniline and azomethine types have been found to possess the necessary properties, but the other three suffer from serious defects. Because only p-phenylenediamine and its derivatives can be used to form the indoaniline and azomethine dyes, it has become the most widely used color developing agent.Impact In the early 1920’s, Leopold Mannes and Leopold Godowsky made a great advance beyond the Fischer process. Working on a new process of color photography, they adopted coupler development, but instead of putting couplers into the emulsion as Fischer had, they introduced them during processing. Finally, in 1935, the film was placed on the market under the name “Kodachrome,” a name that had been used for an early two-color process. The first use of the new Kodachrome process in 1935 was for 16- millimeter film. Color motion pictures could be made by the Kodachrome process as easily as black-and-white pictures, because the complex work involved (the color development of the film) was done under precise technical control. The definition (quality of the image) given by the process was soon sufficient to make it practical for 8-millimeter pictures, and in 1936, Kodachrome film was introduced in a 35-millimeter size for use in popular miniature cameras. Soon thereafter, color processes were developed on a larger scale and new color materials were rapidly introduced. In 1940, the Kodak Research Laboratories worked out a modification of the Fischer process in which the couplers were put into the emulsion layers. These couplers are not dissolved in the gelatin layer itself, as the Fischer couplers are, but are carried in small particles of an oily material that dissolves the couplers, protects them from the gelatin, and protects the silver bromide from any interaction with the couplers. When development takes place, the oxidation product of the developing agent penetrates into the organic particles and reacts with the couplers so that the dyes are formed in small particles that are dispersed throughout the layers. In one form of this material, Ektachrome (originally intended for use in aerial photography), the film is reversed to produce a color positive. It is first developed with a black-and-white developer, then reexposed and developed with a color developer that recombines with the couplers in each layer to produce the appropriate dyes, all three of which are produced simultaneously in one development. In summary, although Fischer did not succeed in putting his theory into practice, his work still forms the basis of most modern color photographic systems. Not only did he demonstrate the general principle of dye-coupling development, but the art is still mainly confined to one of the two types of developing agent, and two of the five types of dye, described by him.

COBOL computer language

The invention: The first user-friendly computer programming language, COBOL was originally designed to solve ballistics problems. The people behind the invention: Grace Murray Hopper (1906-1992), an American mathematician Howard Hathaway Aiken (1900-1973), an American mathematician Plain Speaking Grace Murray Hopper, a mathematician, was a faculty member at Vassar College when World War II (1939-1945) began. She enlisted in the Navy and in 1943 was assigned to the Bureau of Ordnance Computation Project, where she worked on ballistics problems. In 1944, the Navy began using one of the first electronic computers, the Automatic Sequence Controlled Calculator (ASCC), designed by an International Business Machines (IBM) Corporation team of engineers headed by Howard Hathaway Aiken, to solve ballistics problems. Hopper became the third programmer of the ASCC. Hopper’s interest in computer programming continued after the war ended. By the early 1950’s, Hopper’s work with programming languages had led to her development of FLOW-MATIC, the first English-language data processing compiler. Hopper’s work on FLOW-MATIC paved the way for her later work with COBOL (Common Business Oriented Language). Until Hopper developed FLOW-MATIC, digital computer programming was all machine-specific and was written in machine code. A program designed for one computer could not be used on another. Every program was both machine-specific and problemspecific in that the programmer would be told what problem the machine was going to be asked and then would write a completely new program for that specific problem in the machine code.Machine code was based on the programmer’s knowledge of the physical characteristics of the computer as well as the requirements of the problem to be solved; that is, the programmer had to know what was happening within the machine as it worked through a series of calculations, which relays tripped when and in what order, and what mathematical operations were necessary to solve the problem. Programming was therefore a highly specialized skill requiring a unique combination of linguistic, reasoning, engineering, and mathematical abilities that not even all the mathematicians and electrical engineers who designed and built the early computers possessed. While every computer still operates in response to the programming, or instructions, built into it, which are formatted in machine code, modern computers can accept programs written in nonmachine code—that is, in various automatic programming languages. They are able to accept nonmachine code programs because specialized programs now exist to translate those programs into the appropriate machine code. These translating programs are known as “compilers,” or “assemblers,” andFLOW-MATIC was the first such program. Hopper developed FLOW-MATIC after realizing that it would be necessary to eliminate unnecessary steps in programming to make computers more efficient. FLOW-MATIC was based, in part, on Hopper’s recognition that certain elements, or commands, were common to many different programming applications. Hopper theorized that it would not be necessary to write a lengthy series of instructions in machine code to instruct a computer to begin a series of operations; instead, she believed that it would be possible to develop commands in an assembly language in such a way that a programmer could write one command, such as the word add, that would translate into a sequence of several commands in machine code. Hopper’s successful development of a compiler to translate programming languages into machine code thus meant that programming became faster and easier. From assembly languages such asFLOW-MATIC, it was a logical progression to the development of high-level computer languages, such as FORTRAN (Formula Translation) and COBOL.The Language of Business Between 1955 (when FLOW-MATIC was introduced) and 1959, a number of attempts at developing a specific business-oriented language were made. IBM and Remington Rand believed that the only way to market computers to the business community was through the development of a language that business people would be comfortable using. Remington Rand officials were especially committed to providing a language that resembled English. None of the attempts to develop a business-oriented language succeeded, however, and by 1959 Hopper and other members of the U.S. Department of Defense had persuaded representatives of various companies of the need to cooperate. On May 28 and 29, 1959, a conference sponsored by the Department of Defense was held at the Pentagon to discuss the problem of establishing a common language for the adaptation of electronic computers for data processing. As a result, the first distribution of COBOL was accomplished on December 17, 1959. Although many people were involved in the development of COBOL, Hopper played a particularly important role. She not only found solutions to technical problems but also succeeded in selling the concept of a common language from an administrative and managerial point of view. Hopper recognized that while the companies involved in the commercial development of computers were in competition with one another, the use of a common, business-oriented language would contribute to the growth of the computer industry as a whole, as well as simplify the training of computer programmers and operators. Consequences COBOL was the first compiler developed for business data processing operations. Its development simplified the training required for computer users in business applications and demonstrated that computers could be practical tools in government and industry as well as in science. Prior to the development of COBOL, electronic computers had been characterized as expensive, oversized adding machines that were adequate for performing time-consuming mathematics but lacked the flexibility that business people required. In addition, the development of COBOL freed programmers not only from the need to know machine code but also from the need to understand the physical functioning of the computers they were using. Programming languages could be written that were both machine- independent and almost universally convertible from one computer to another.Finally, because Hopper and the other committee members worked under the auspices of the Department of Defense, the software was not copyrighted, and in a short period of time COBOL became widely available to anyone who wanted to use it. It diffused rapidly throughout the industry and contributed to the widespread adaptation of computers for use in countless settings.

Cloud seeding

The invention: Technique for inducing rainfall by distributing dry ice or silver nitrate into reluctant rainclouds. The people behind the invention: Vincent Joseph Schaefer (1906-1993), an American chemist and meteorologist Irving Langmuir (1881-1957), an American physicist and chemist who won the 1932 Nobel Prize in Chemistry Bernard Vonnegut (1914-1997), an American physical chemist and meteorologist Praying for Rain Beginning in 1943, an intense interest in the study of clouds developed into the practice of weather “modification.” Working for the General Electric Research Laboratory, Nobel laureate Irving Langmuir and his assistant researcher and technician, Vincent Joseph Schaefer, began an intensive study of precipitation and its causes. Past research and study had indicated two possible ways that clouds produce rain. The first possibility is called “coalescing,” a process by which tiny droplets of water vapor in a cloud merge after bumping into one another and become heavier and fatter until they drop to earth. The second possibility is the “Bergeron process” of droplet growth, named after the Swedish meteorologist Tor Bergeron. Bergeron’s process relates to supercooled clouds, or clouds that are at or below freezing temperatures and yet still contain both ice crystals and liquid water droplets. The size of the water droplets allows the droplets to remain liquid despite freezing temperatures; while small droplets can remain liquid only down to 4 degrees Celsius, larger droplets may not freeze until reaching -15 degrees Celsius. Precipitation occurs when the ice crystals become heavy enough to fall. If the temperature at some point below the cloud is warm enough, it will melt the ice crystals before they reach the earth, producing rain. If the temperature remains at the freezing point, the ice crystals retain their form and fall as snow. Schaefer used a deep-freezing unit in order to observe water droplets in pure cloud form. In order to observe the droplets better, Schaefer lined the chest with black velvet and concentrated a beam of light inside. The first agent he introduced inside the supercooled freezer was his own breath. When that failed to form the desired ice crystals, he proceeded to try other agents. His hope was to form ice crystals that would then cause the moisture in the surrounding air to condense into more ice crystals, which would produce a miniature snowfall. He eventually achieved success when he tossed a handful of dry ice inside and was rewarded with the long-awaited snow. The freezer was set at the freezing point of water, 0 degrees Celsius, but not all the particles were ice crystals, so when the dry ice was introduced all the stray water droplets froze instantly, producing ice crystals, or snowflakes. Planting the First Seeds On November 13, 1946, Schaefer took to the air over Mount Greylock with several pounds of dry ice in order to repeat the experiment in nature. After he had finished sprinkling, or seeding, a supercooled cloud, he instructed the pilot to fly underneath the cloud he had just seeded. Schaefer was greeted by the sight of snow. By the time it reached the ground, it had melted into the first-ever human-made rainfall. Independently of Schaefer and Langmuir, another General Electric scientist, Bernard Vonnegut, was also seeking a way to cause rain. He found that silver iodide crystals, which have the same size and shape as ice crystals, could “fool” water droplets into condensing on them. When a certain chemical mixture containing silver iodide is heated on a special burner called a “generator,” silver iodide crystals appear in the smoke of the mixture. Vonnegut’s discovery allowed seeding to occur in a way very different from seeding with dry ice, but with the same result. Using Vonnegut’s process, the seeding is done from the ground. The generators are placed outside and the chemicals are mixed. As the smoke wafts upward, it carries the newly formed silver iodide crystals with it into the clouds. The results of the scientific experiments by Langmuir, Vonnegut, and Schaefer were alternately hailed and rejected as legitimate. Critics argue that the process of seeding is too complex and would have to require more than just the addition of dry ice or silver nitrate in order to produce rain. One of the major problems surrounding the question of weather modification by cloud seeding is the scarcity of knowledge about the earth’s atmosphere. Ajourney begun about fifty years ago is still a long way from being completed. Impact Although the actual statistical and other proofs needed to support cloud seeding are lacking, the discovery in 1946 by the General Electric employees set off a wave of interest and demand for information that far surpassed the interest generated by the discovery of nuclear fission shortly before. The possibility of ending drought and, in the process, hunger excited many people. The discovery also prompted both legitimate and false “rainmakers” who used the information gathered by Schaefer, Langmuir, and Vonnegut to set up cloud-seeding businesses.Weather modification, in its current stage of development, cannot be used to end worldwide drought. It does, however, have beneficial results in some cases on the crops of smaller farms that have been affected by drought. In order to understand the advances made in weather modification, new instruments are needed to record accurately the results of further experimentation. The storm of interest—both favorable and nonfavorable—generated by the discoveries of Schaefer, Langmuir, and Vonnegut has had and will continue to have far-reaching effects on many aspects of society.

Cloning

The invention: Experimental technique for creating exact duplicates of living organisms by recreating their DNA. The people behind the invention: Ian Wilmut, an embryologist with the Roslin Institute Keith H. S. Campbell, an experiment supervisor with the Roslin Institute J. McWhir, a researcher with the Roslin Institute W. A. Ritchie, a researcher with the Roslin Institute Making Copies On February 22, 1997, officials of the Roslin Institute, a biological research institution near Edinburgh, Scotland, held a press conference to announce startling news: They had succeeded in creating a clone—a biologically identical copy—from cells taken from an adult sheep. Although cloning had been performed previously with simpler organisms, the Roslin Institute experiment marked the first time that a large, complex mammal had been successfully cloned. Cloning, or the production of genetically identical individuals, has long been a staple of science fiction and other popular literature. Clones do exist naturally, as in the example of identical twins. Scientists have long understood the process by which identical twins are created, and agricultural researchers have often dreamed of a method by which cheap identical copies of superior livestock could be created. The discovery of the double helix structure of deoxyribonucleic acid (DNA), or the genetic code, by JamesWatson and Francis Crick in the 1950’s led to extensive research into cloning and genetic engineering. Using the discoveries ofWatson and Crick, scientists were soon able to develop techniques to clone laboratory mice; however, the cloning of complex, valuable animals such as livestock proved to be hard going. Early versions of livestock cloning were technical attempts at duplicating the natural process of fertilized egg splitting that leads to the birth of identical twins. Artificially inseminated eggs were removed, split, and then reinserted into surrogate mothers. This method proved to be overly costly for commercial purposes, a situation aggravated by a low success rate. Nuclear Transfer Researchers at the Roslin Institute found these earlier attempts to be fundamentally flawed. Even if the success rate could be improved, the number of clones created (of sheep, in this case) would still be limited. The Scots, led by embryologist Ian Wilmut and experiment supervisor Keith Campbell, decided to take an entirely different approach. The result was the first live birth of a mammal produced through a process known as “nuclear transfer.” Nuclear transfer involves the replacement of the nucleus of an immature egg with a nucleus taken from another cell. Previous attempts at nuclear transfer had cells from a single embryo divided up and implanted into an egg. Because a sheep embryo has only about forty usable cells, this method also proved limiting. The Roslin team therefore decided to grow their own cells in a laboratory culture. They took more mature embryonic cells than those previously used, and they experimented with the use of a nutrient mixture. One of their breakthroughs occurred when they discovered that these “cell lines” grew much more quickly when certain nutrients were absent.Using this technique, the Scots were able to produce a theoretically unlimited number of genetically identical cell lines. The next step was to transfer the cell lines of the sheep into the nucleus of unfertilized sheep eggs. First, 277 nuclei with a full set of chromosomes were transferred to the unfertilized eggs. An electric shock was then used to cause the eggs to begin development, the shock performing the duty of fertilization. Of these eggs, twenty-nine developed enough to be inserted into surrogate mothers. All the embryos died before birth except one: a ewe the scientists named “Dolly.” Her birth on July 5, 1996, was witnessed by only a veterinarian and a few researchers. Not until the clone had survived the critical earliest stages of life was the success of the experiment disclosed; Dolly was more than seven months old by the time her birth was announced to a startled world.Impact The news that the cloning of sophisticated organisms had left the realm of science fiction and become a matter of accomplished scientific fact set off an immediate uproar. Ethicists and media commentators quickly began to debate the moral consequences of the use— and potential misuse—of the technology. Politicians in numerous countries responded to the news by calling for legal restrictions on cloning research. Scientists, meanwhile, speculated about the possible benefits and practical limitations of the process. The issue that stirred the imagination of the broader public and sparked the most spirited debate was the possibility that similar experiments might soon be performed using human embryos. Although most commentators seemed to agree that such efforts would be profoundly immoral, many experts observed that they would be virtually impossible to prevent. “Could someone do this tomorrow morning on a human embryo?” Arthur L. Caplan, the director of the University of Pennsylvania’s bioethics center, asked reporters. “Yes. It would not even take too much science. The embryos are out there.” Such observations conjured visions of a future that seemed marvelous to some, nightmarish to others. Optimists suggested that the best and brightest of humanity could be forever perpetuated, creating an endless supply of Albert Einsteins and Wolfgang Amadeus Mozarts. Pessimists warned of a world overrun by clones of selfserving narcissists and petty despots, or of the creation of a secondary class of humans to serve as organ donors for their progenitors. The Roslin Institute’s researchers steadfastly proclaimed their own opposition to human experimentation. Moreover, most scientists were quick to point out that such scenarios were far from realization, noting the extremely high failure rate involved in the creation of even a single sheep. In addition, most experts emphasized more practical possible uses of the technology: improving agricultural stock by cloning productive and disease-resistant animals, for example, or regenerating endangered or even extinct species. Even such apparently benign schemes had their detractors, however, as other observers remarked on the potential dangers of thus narrowing a species’ genetic pool. Even prior to the Roslin Institute’s announcement, most European nations had adopted a bioethics code that flatly prohibited genetic experiments on human subjects. Ten days after the announcement, U.S. president Bill Clinton issued an executive order that banned the use of federal money for human cloning research, and he called on researchers in the private sector to refrain from such experiments voluntarily. Nevertheless, few observers doubted that Dolly’s birth marked only the beginning of an intriguing—and possibly frightening—new chapter in the history of science.

Cell phone

The invention: 

Mobile telephone system controlled by computers
to use a region’s radio frequencies, or channels, repeatedly,
thereby accommodating large numbers of users.

The people behind the invention:

William Oliver Baker (1915- ), the president of Bell
Laboratories
Richard H. Fefrenkiel, the head of the mobile systems
engineering department at Bell

CAT scanner

The invention:

 A technique that collects X-ray data from solid,
opaque masses such as human bodies and uses a computer to
construct a three-dimensional image.


The people behind the invention:

Godfrey Newbold Hounsfield (1919- ), an English
electronics engineer who shared the 1979 Nobel Prize in
Physiology or Medicine
Allan M. Cormack (1924-1998), a South African-born American
physicist who shared the 1979 Nobel Prize in Physiology or
Medicine
James Ambrose, an English radiologist

Cassette recording

The invention: Self-contained system making it possible to record and repeatedly play back sound without having to thread tape through a machine. The person behind the invention: Fritz Pfleumer, a German engineer whose work on audiotapes paved the way for audiocassette production Smaller Is Better The introduction of magnetic audio recording tape in 1929 was met with great enthusiasm, particularly in the entertainment industry, and specifically among radio broadcasters. Although somewhat practical methods for recording and storing sound for later playback had been around for some time, audiotape was much easier to use, store, and edit, and much less expensive to produce. It was Fritz Pfleumer, a German engineer, who in 1929 filed the first audiotape patent. His detailed specifications indicated that tape could be made by bonding a thin coating of oxide to strips of either paper or film. Pfleumer also suggested that audiotape could be attached to filmstrips to provide higher-quality sound than was available with the film sound technologies in use at that time. In 1935, the German electronics firm AEG produced a reliable prototype of a record-playback machine based on Pfleumer’s idea. By 1947, the American company 3M had refined the concept to the point where it was able to produce a high-quality tape using a plastic- based backing and red oxide. The tape recorded and reproduced sound with a high degree of clarity and dynamic range and would soon become the standard in the industry. Still, the tape was sold and used in a somewhat inconvenient open-reel format. The user had to thread it through a machine and onto a take-up reel. This process was somewhat cumbersome and complicated for the layperson. For many years, sound-recording technology remained a tool mostly for professionals. In 1963, the first audiocassette was introduced by the Netherlands-based PhilipsNVcompany. This device could be inserted into a machine without threading. Rewind and fast-forward were faster, and it made no difference where the tape was stopped prior to the ejection of the cassette. By contrast, open-reel audiotape required that the tape be wound fully onto one or the other of the two reels before it could be taken off the machine. Technical advances allowed the cassette tape to be much narrower than the tape used in open reels and also allowed the tape speed to be reduced without sacrificing sound quality. Thus, the cassette was easier to carry around, and more sound could be recorded on a cassette tape. In addition, the enclosed cassette decreased wear and tear on the tape and protected it from contamination. Creating a Market One of the most popular uses for audiocassettes was to record music from radios and other audio sources for later playback. During the 1970’s, many radio stations developed “all music” formats in which entire albums were often played without interruption. That gave listeners an opportunity to record the music for later playback. At first, the music recording industry complained about this practice, charging that unauthorized recording of music from the radio was a violation of copyright laws. Eventually, the issue died down as the same companies began to recognize this new, untapped market for recorded music on cassette. Audiocassettes, all based on the original Philips design, were being manufactured by more than sixty companies within only a few years of their introduction. In addition, spin-offs of that design were being used in many specialized applications, including dictation, storage of computer information, and surveillance. The emergence of videotape resulted in a number of formats for recording and playing back video based on the same principle. Although each is characterized by different widths of tape, each uses the same technique for tape storage and transport. The cassette has remained a popular means of storing and retrieving information on magnetic tape for more than a quarter of a century. During the early 1990’s, digital technologies such as audio CDs (compact discs) and the more advanced CD-ROM (compact discs that reproduce sound, text, and images via computer) were beginning to store information in revolutionary new ways. With the development of this increasingly sophisticated technology, need for the audiocassette, once the most versatile, reliable, portable, and economical means of recording, storing, and playing-back sound, became more limited. Consequences The cassette represented a new level of convenience for the audiophile, resulting in a significant increase in the use of recording technology in all walks of life. Even small children could operate cassette recorders and players, which led to their use in schools for a variety of instructional tasks and in the home for entertainment. The recording industry realized that audiotape cassettes would allow consumers to listen to recorded music in places where record players were impractical: in automobiles, at the beach, even while camping. The industry also saw the need for widespread availability of music and information on cassette tape. It soon began distributing albums on audiocassette in addition to the long-play vinyl discs, and recording sales increased substantially. This new technology put recorded music into automobiles for the first time, again resulting in a surge in sales for recorded music. Eventually, information, including language instruction and books-on-tape, became popular commuter fare. With the invention of the microchip, audiotape players became available in smaller and smaller sizes, making them truly portable. Audiocassettes underwent another explosion in popularity during the early 1980’s, when the Sony Corporation introduced the Walkman, an extremely compact, almost weightless cassette player that could be attached to clothing and used with lightweight earphones virtually anywhere. At the same time, cassettes were suddenly being used with microcomputers for backing up magnetic data files. Home video soon exploded onto the scene, bringing with it new applications for cassettes. As had happened with audiotape, video camera-recorder units, called “camcorders,” were miniaturized to the point where 8-millimeter videocassettes capable of recording up to 90 minutes of live action and sound were widely available. These cassettes closely resembled the audiocassette first introduced in 1963.

Carbon dating

The invention: Atechnique that measures the radioactive decay of carbon 14 in organic substances to determine the ages of artifacts as old as ten thousand years. The people behind the invention: Willard Frank Libby (1908-1980), an American chemist who won the 1960 Nobel Prize in Chemistry Charles Wesley Ferguson (1922-1986), a scientist who demonstrated that carbon 14 dates before 1500 b.c. needed to be corrected One in a Trillion Carbon dioxide in the earth’s atmosphere contains a mixture of three carbon isotopes (isotopes are atoms of the same element that contain different numbers of neutrons), which occur in the following percentages: about 99 percent carbon 12, about 1 percent carbon 13, and approximately one atom in a trillion of radioactive carbon 14. Plants absorb carbon dioxide from the atmosphere during photosynthesis, and then animals eat the plants, so all living plants and animals contain a small amount of radioactive carbon. When a plant or animal dies, its radioactivity slowly decreases as the radioactive carbon 14 decays. The time it takes for half of any radioactive substance to decay is known as its “half-life.” The half-life for carbon 14 is known to be about fifty-seven hundred years. The carbon 14 activity will drop to one-half after one half-life, onefourth after two half-lives, one-eighth after three half-lives, and so forth. After ten or twenty half-lives, the activity becomes too low to be measurable. Coal and oil, which were formed from organic matter millions of years ago, have long since lost any carbon 14 activity. Wood samples from an Egyptian tomb or charcoal from a prehistoric fireplace a few thousand years ago, however, can be dated with good reliability from the leftover radioactivity. In the 1940’s, the properties of radioactive elements were still being discovered and were just beginning to be used to solve problems. Scientists still did not know the half-life of carbon 14, and archaeologists still depended mainly on historical evidence to determine the ages of ancient objects. In early 1947,Willard Frank Libby started a crucial experiment in testing for radioactive carbon. He decided to test samples of methane gas from two different sources. One group of samples came from the sewage disposal plant at Baltimore, Maryland, which was rich in fresh organic matter. The other sample of methane came from an oil refinery, which should have contained only ancient carbon from fossils whose radioactivity should have completely decayed. The experimental results confirmed Libby’s suspicions: The methane from fresh sewage was radioactive, but the methane from oil was not. Evidently, radioactive carbon was present in fresh organic material, but it decays away eventually. Tree-Ring Dating In order to establish the validity of radiocarbon dating, Libby analyzed known samples of varying ages. These included tree-ring samples from the years 575 and 1075 and one redwood from 979 b.c.e., as well as artifacts from Egyptian tombs going back to about 3000 b.c.e. In 1949, he published an article in the journal Science that contained a graph comparing the historical ages and the measured radiocarbon ages of eleven objects. The results were accurate within 10 percent, which meant that the general method was sound. The first archaeological object analyzed by carbon dating, obtained from the Metropolitan Museum of Art in New York, was a piece of cypress wood from the tomb of King Djoser of Egypt. Based on historical evidence, the age of this piece of wood was about fortysix hundred years. A small sample of carbon obtained from this wood was deposited on the inside of Libby’s radiation counter, giving a count rate that was about 40 percent lower than that of modern organic carbon. The resulting age of the wood calculated from its residual radioactivity was about thirty-eight hundred years, a difference of eight hundred years. Considering that this was the first object to be analyzed, even such a rough agreement with the historic age was considered to be encouraging. The validity of radiocarbon dating depends on an important assumption— namely, that the abundance of carbon 14 in nature has been constant for many thousands of years. If carbon 14 was less abundant at some point in history, organic samples from that era would have started with less radioactivity. When analyzed today, their reduced activity would make them appear to be older than they really are.Charles Wesley Ferguson from the Tree-Ring Research Laboratory at the University of Arizona tackled this problem. He measured the age of bristlecone pine trees both by counting the rings and by using carbon 14 methods. He found that carbon 14 dates before 1500 b.c.e. needed to be corrected. The results show that radiocarbon dates are older than tree-ring counting dates by as much as several hundred years for the oldest samples. He knew that the number of tree rings had given him the correct age of the pines, because trees accumulate one ring of growth for every year of life. Apparently, the carbon 14 content in the atmosphere has not been constant. Fortunately, tree-ring counting gives reliable dates that can be used to correct radiocarbon measurements back to about 6000 b.c.e. Impact Some interesting samples were dated by Libby’s group. The Dead Sea Scrolls had been found in a cave by an Arab shepherd in 1947, but some Bible scholars at first questioned whether they were genuine. The linen wrapping from the Book of Isaiah was tested for carbon 14, giving a date of 100 b.c.e., which helped to establish its authenticity. Human hair from an Egyptian tomb was determined to be nearly five thousand years old.Well-preserved sandals from a cave in eastern Oregon were determined to be ninety-three hundred years old. A charcoal sample from a prehistoric site in western South Dakota was found to be about seven thousand years old. The Shroud of Turin, located in Turin, Italy, has been a controversial object for many years. It is a linen cloth, more than four meters long, which shows the image of a man’s body, both front and back. Some people think it may have been the burial shroud of Jesus Christ after his crucifixion. Ateam of scientists in 1978 was permitted to study the shroud, using infrared photography, analysis of possible blood stains, microscopic examination of the linen fibers, and other methods. The results were ambiguous. A carbon 14 test was not permitted because it would have required cutting a piece about the size of a handkerchief from the shroud. Anew method of measuring carbon 14 was developed in the late 1980’s. It is called “accelerator mass spectrometry,” or AMS. Unlike Libby’s method, it does not count the radioactivity of carbon. Instead, a mass spectrometer directly measures the ratio of carbon 14 to ordinary carbon. The main advantage of this method is that the sample size needed for analysis is about a thousand times smaller than before. The archbishop of Turin permitted three laboratories with the appropriate AMS apparatus to test the shroud material. The results agreed that the material was from the fourteenth century, not from the time of Christ. The figure on the shroud may be a watercolor painting on linen. Since Libby’s pioneering experiments in the late 1940’s, carbon 14 dating has established itself as a reliable dating technique for archaeologists and cultural historians. Further improvements are expected to increase precision, to make it possible to use smaller samples, and to extend the effective time range of the method back to fifty thousand years or earlier.

CAD/CAM

The invention: Computer-Aided Design (CAD) and Computer- Aided Manufacturing (CAM) enhanced flexibility in engineering design, leading to higher quality and reduced time for manufacturing The people behind the invention: Patrick Hanratty, a General Motors Research Laboratory worker who developed graphics programs Jack St. Clair Kilby (1923- ), a Texas Instruments employee who first conceived of the idea of the integrated circuit Robert Noyce (1927-1990), an Intel Corporation employee who developed an improved process of manufacturing integrated circuits on microchips Don Halliday, an early user of CAD/CAM who created the Made-in-America car in only four months by using CAD and project management software Fred Borsini, an early user of CAD/CAM who demonstrated its power Summary of Event Computer-Aided Design (CAD) is a technique whereby geometrical descriptions of two-dimensional (2-D) or three-dimensional (3- D) objects can be created and stored, in the form of mathematical models, in a computer system. Points, lines, and curves are represented as graphical coordinates. When a drawing is requested from the computer, transformations are performed on the stored data, and the geometry of a part or a full view from either a two- or a three-dimensional perspective is shown. CAD systems replace the tedious process of manual drafting, and computer-aided drawing and redrawing that can be retrieved when needed has improved drafting efficiency. A CAD system is a combination of computer hardware and software that facilitates the construction of geometric models and, in many cases, their analysis. It allows a wide variety of visual representations of those models to be displayed.Computer-Aided Manufacturing (CAM) refers to the use of computers to control, wholly or partly, manufacturing processes. In practice, the term is most often applied to computer-based developments of numerical control technology; robots and flexible manufacturing systems (FMS) are included in the broader use of CAM systems. A CAD/CAM interface is envisioned as a computerized database that can be accessed and enriched by either design or manufacturing professionals during various stages of the product development and production cycle. In CAD systems of the early 1990’s, the ability to model solid objects became widely available. The use of graphic elements such as lines and arcs and the ability to create a model by adding and subtracting solids such as cubes and cylinders are the basic principles of CADand of simulating objects within a computer.CADsystems enable computers to simulate both taking things apart (sectioning) and putting things together for assembly. In addition to being able to construct prototypes and store images of different models, CAD systems can be used for simulating the behavior of machines, parts, and components. These abilities enable CAD to construct models that can be subjected to nondestructive testing; that is, even before engineers build a physical prototype, the CAD model can be subjected to testing and the results can be analyzed. As another example, designers of printed circuit boards have the ability to test their circuits on a CAD system by simulating the electrical properties of components. During the 1950’s, the U.S. Air Force recognized the need for reducing the development time for special aircraft equipment. As a result, the Air Force commissioned the Massachusetts Institute of Technology to develop numerically controlled (NC) machines that were programmable. A workable demonstration of NC machines was made in 1952; this began a new era for manufacturing. As the speed of an aircraft increased, the cost of manufacturing also increased because of stricter technical requirements. This higher cost provided a stimulus for the further development of NC technology, which promised to reduce errors in design before the prototype stage. The early 1960’s saw the development of mainframe computers. Many industries valued computing technology for its speed and for its accuracy in lengthy and tedious numerical operations in design, manufacturing, and other business functional areas. Patrick Hanratty, working for General Motors Research Laboratory, saw other potential applications and developed graphics programs for use on mainframe computers. The use of graphics in software aided the development of CAD/CAM, allowing visual representations of models to be presented on computer screens and printers. The 1970’s saw an important development in computer hardware, namely the development and growth of personal computers (PCs). Personal computers became smaller as a result of the development of integrated circuits. Jack St. Clair Kilby, working for Texas Instruments, first conceived of the integrated circuit; later, Robert Noyce, working for Intel Corporation, developed an improved process of manufacturing integrated circuits on microchips. Personal computers using these microchips offered both speed and accuracy at costs much lower than those of mainframe computers. Five companies offered integrated commercial computer-aided design and computer-aided manufacturing systems by the first half of 1973. Integration meant that both design and manufacturing were contained in one system. Of these five companies—Applicon, Computervision, Gerber Scientific, Manufacturing and Consulting Services (MCS), and United Computing—four offered turnkey systems exclusively. Turnkey systems provide design, development, training, and implementation for each customer (company) based on the contractual agreement; they are meant to be used as delivered, with no need for the purchaser to make significant adjustments or perform programming. The 1980’s saw a proliferation of mini- and microcomputers with a variety of platforms (processors) with increased speed and better graphical resolution. This made the widespread development of computer-aided design and computer-aided manufacturing possible and practical. Major corporations spent large research and development budgets developing CAD/CAM systems that would automate manual drafting and machine tool movements. Don Halliday, working for Truesports Inc., provided an early example of the benefits of CAD/CAM. He created the Made-in-America car in only four months by using CAD and project management software. In the late 1980’s, Fred Borsini, the president of Leap Technologies in Michigan, brought various products to market in record time through the use of CAD/CAM. In the early 1980’s, much of theCAD/CAMindustry consisted of software companies. The cost for a relatively slow interactive system in 1980 was close to $100,000. The late 1980’s saw the demise of minicomputer-based systems in favor of Unix work stations and PCs based on 386 and 486 microchips produced by Intel. By the time of the International Manufacturing Technology show in September, 1992, the industry could show numerous CAD/CAM innovations including tools, CAD/CAM models to evaluate manufacturability in early design phases, and systems that allowed use of the same data for a full range of manufacturing functions. Impact In 1990, CAD/CAM hardware sales by U.S. vendors reached $2.68 billion. In software alone, $1.42 billion worth of CAD/CAM products and systems were sold worldwide by U.S. vendors, according to International Data Corporation figures for 1990. CAD/ CAM systems were in widespread use throughout the industrial world. Development lagged in advanced software applications, particularly in image processing, and in the communications software and hardware that ties processes together. A reevaluation of CAD/CAM systems was being driven by the industry trend toward increased functionality of computer-driven numerically controlled machines. Numerical control (NC) software enables users to graphically define the geometry of the parts in a product, develop paths that machine tools will follow, and exchange data among machines on the shop floor. In 1991, NC configuration software represented 86 percent of total CAM sales. In 1992, the market shares of the five largest companies in the CAD/CAM market were 29 percent for International Business Machines, 17 percent for Intergraph, 11 percent for Computervision, 9 percent for Hewlett-Packard, and 6 percent for Mentor Graphics. General Motors formed a joint venture with Ford and Chrysler to develop a common computer language in order to make the next generation of CAD/CAM systems easier to use. The venture was aimed particularly at problems that posed barriers to speeding up the design of new automobiles. The three car companies all had sophisticated computer systems that allowed engineers to design parts on computers and then electronically transmit specifications to tools that make parts or dies. CAD/CAM technology was expected to advance on many fronts. As of the early 1990’s, different CAD/CAM vendors had developed systems that were often incompatible with one another, making it difficult to transfer data from one system to another. Large corporations, such as the major automakers, developed their own interfaces and network capabilities to allow different systems to communicate. Major users of CAD/CAM saw consolidation in the industry through the establishment of standards as being in their interests. Resellers of CAD/CAM products also attempted to redefine their markets. These vendors provide technical support and service to users. The sale of CAD/CAM products and systems offered substantial opportunities, since demand remained strong. Resellers worked most effectively with small and medium-sized companies, which often were neglected by the primary sellers of CAD/CAM equipment because they did not generate a large volume of business. Some projections held that by 1995 half of all CAD/CAM systems would be sold through resellers, at a cost of $10,000 or less for each system. The CAD/CAM market thus was in the process of dividing into two markets: large customers (such as aerospace firms and automobile manufacturers) that would be served by primary vendors, and small and medium-sized customers that would be serviced by resellers. CAD will find future applications in marketing, the construction industry, production planning, and large-scale projects such as shipbuilding and aerospace. Other likely CAD markets include hospitals, the apparel industry, colleges and universities, food product manufacturers, and equipment manufacturers. As the linkage between CAD and CAM is enhanced, systems will become more productive. The geometrical data from CAD will be put to greater use by CAM systems. CAD/CAM already had proved that it could make a big difference in productivity and quality. Customer orders could be changed much faster and more accurately than in the past, when a change could require a manual redrafting of a design. Computers could do automatically in minutes what once took hours manually. CAD/ CAM saved time by reducing, and in some cases eliminating, human error. Many flexible manufacturing systems (FMS) had machining centers equipped with sensing probes to check the accuracy of the machining process. These self-checks can be made part of numerical control (NC) programs. With the technology of the early 1990’s, some experts estimated that CAD/CAM systems were in many cases twice as productive as the systems they replaced; in the long run, productivity is likely to improve even more, perhaps up to three times that of older systems or even higher. As costs for CAD/ CAM systems concurrently fall, the investment in a system will be recovered more quickly. Some analysts estimated that by the mid- 1990’s, the recovery time for an average system would be about three years. Another frontier in the development of CAD/CAM systems is expert (or knowledge-based) systems, which combine data with a human expert’s knowledge, expressed in the form of rules that the computer follows. Such a system will analyze data in a manner mimicking intelligence. For example, a 3-D model might be created from standard 2-D drawings. Expert systems will likely play a pivotal role in CAM applications. For example, an expert system could determine the best sequence of machining operations to produce a component. Continuing improvements in hardware, especially increased speed, will benefit CAD/CAM systems. Software developments, however, may produce greater benefits. Wider use of CAD/CAM systems will depend on the cost savings from improvements in hardware and software as well as on the productivity of the systems and the quality of their product. The construction, apparel, automobile, and aerospace industries have already experienced increases in productivity, quality, and profitability through the use of CAD/CAM. A case in point is Boeing, which used CAD from start to finish in the design of the 757.

Buna rubber

The invention: The first practical synthetic rubber product developed, Buna inspired the creation of other other synthetic substances that eventually replaced natural rubber in industrial applications. The people behind the invention: Charles de la Condamine (1701-1774), a French naturalist Charles Goodyear (1800-1860), an American inventor Joseph Priestley (1733-1804), an English chemist Charles Greville Williams (1829-1910), an English chemist A New Synthetic Rubber The discovery of natural rubber is often credited to the French scientist Charles de la Condamine, who, in 1736, sent the French Academy of Science samples of an elastic material used by Peruvian Indians to make balls that bounced. The material was primarily a curiosity until 1770, when Joseph Priestley, an English chemist, discovered that it rubbed out pencil marks, after which he called it “rubber.” Natural rubber, made from the sap of the rubber tree (Hevea brasiliensis), became important after Charles Goodyear discovered in 1830 that heating rubber with sulfur (a process called “vulcanization”) made it more elastic and easier to use. Vulcanized natural rubber came to be used to make raincoats, rubber bands, and motor vehicle tires. Natural rubber is difficult to obtain (making one tire requires the amount of rubber produced by one tree in two years), and wars have often cut off supplies of this material to various countries. Therefore, efforts to manufacture synthetic rubber began in the late eighteenth century. Those efforts followed the discovery by English chemist Charles GrevilleWilliams and others in the 1860’s that natural rubber was composed of thousands of molecules of a chemical called isoprene that had been joined to form giant, necklace- like molecules. The first successful synthetic rubber, Buna, was patented by Germany’s I. G. Farben Industrie in 1926. The success of this rubber led to the development of many other synthetic rubbers, which are now used in place of natural rubber in many applications.From Erasers to Gas Pumps Natural rubber belongs to the group of chemicals called “polymers.” Apolymer is a giant molecule that is made up of many simpler chemical units (“monomers”) that are attached chemically to form long strings. In natural rubber, the monomer is isoprene (dimethylbutadiene). The first efforts to make a synthetic rubber used the discovery that isoprene could be made and converted into an elastic polymer. The synthetic rubber that was created from isoprene was, however, inferior to natural rubber. The first Buna rubber, which was patented by I. G. Farben in 1926, was better, but it was still less than ideal. Buna rubber was made by polymerizing the monomer butadiene in the presence of sodium. The name Buna comes from the first two letters of the words “butadiene” and “natrium” (German for sodium). Natural and Buna rubbers are called homopolymers because they contain only one kind of monomer. The ability of chemists to make Buna rubber, along with its successful use, led to experimentation with the addition of other monomers to isoprene-like chemicals used to make synthetic rubber. Among the first great successes were materials that contained two alternating monomers; such materials are called “copolymers.” If the two monomers are designated Aand B, part of a polymer molecule can be represented as (ABABABABABABABABAB). Numerous synthetic copolymers, which are often called “elastomers,” now replace natural rubber in applications where they have superior properties. All elastomers are rubbers, since objects made from them both stretch greatly when pulled and return quickly to their original shape when the tension is released. Two other well-known rubbers developed by I. G. Farben are the copolymers called Buna-N and Buna-S. These materials combine butadiene and the monomers acrylonitrile and styrene, respectively. Many modern motor vehicle tires are made of synthetic rubber that differs little from Buna-S rubber. This rubber was developed after the United States was cut off in the 1940’s, during World War II, from its Asian source of natural rubber. The solution to this problem was the development of a synthetic rubber industry based on GR-S rubber (government rubber plus styrene), which was essentially Buna-S rubber. This rubber is still widely used.Buna-S rubber is often made by mixing butadiene and styrene in huge tanks of soapy water, stirring vigorously, and heating the mixture. The polymer contains equal amounts of butadiene and styrene (BSBSBSBSBSBSBSBS). When the molecules of the Buna-S polymer reach the desired size, the polymerization is stopped and the rubber is coagulated (solidified) chemically. Then, water and all the unused starting materials are removed, after which the rubber is dried and shipped to various plants for use in tires and other products. The major difference between Buna-S and GR-S rubber is that the method of making GR-S rubber involves the use of low temperatures. Buna-N rubber is made in a fashion similar to that used for Buna- S, using butadiene and acrylonitrile. Both Buna-N and the related neoprene rubber, invented by Du Pont, are very resistant to gasoline and other liquid vehicle fuels. For this reason, they can be used in gas-pump hoses. All synthetic rubbers are vulcanized before they are used in industry. Impact Buna rubber became the basis for the development of the other modern synthetic rubbers. These rubbers have special properties that make them suitable for specific applications. One developmental approach involved the use of chemically modified butadiene in homopolymers such as neoprene. Made of chloroprene (chlorobutadiene), neoprene is extremely resistant to sun, air, and chemicals. It is so widely used in machine parts, shoe soles, and hoses that more than 400 million pounds are produced annually. Another developmental approach involved copolymers that alternated butadiene with other monomers. For example, the successful Buna-N rubber (butadiene and acrylonitrile) has properties similar to those of neoprene. It differs sufficiently from neoprene, however, to be used to make items such as printing press rollers. About 200 million pounds of Buna-N are produced annually. Some 4 billion pounds of the even more widely used polymer Buna-S/ GR-S are produced annually, most of which is used to make tires. Several other synthetic rubbers have significant industrial applications, and efforts to make copolymers for still other purposes continue.

Bullet train

The invention: An ultrafast passenger railroad system capable of moving passengers at speeds double or triple those of ordinary trains. The people behind the invention: Ikeda Hayato (1899-1965), Japanese prime minister from 1960 to 1964, who pushed for the expansion of public expenditures Shinji Sogo (1901-1971), the president of the Japanese National Railways, the “father of the bullet train” Building a Faster Train By 1900, Japan had a world-class railway system, a logical result of the country’s dense population and the needs of its modernizing economy. After 1907, the government controlled the system through the Japanese National Railways (JNR). In 1938, JNR engineers first suggested the idea of a train that would travel 125 miles per hour from Tokyo to the southern city of Shimonoseki. Construction of a rapid train began in 1940 but was soon stopped because of World War II. The 311-mile railway between Tokyo and Osaka, the Tokaido Line, has always been the major line in Japan. By 1957, a business express along the line operated at an average speed of 57 miles per hour, but the double-track line was rapidly reaching its transport capacity. The JNR established two investigative committees to explore alternative solutions. In 1958, the second committee recommended the construction of a high-speed railroad on a separate double track, to be completed in time for the Tokyo Olympics of 1964. The Railway Technical Institute of the JNR concluded that it was feasible to design a line that would operate at an average speed of about 130 miles per hour, cutting time for travel between Tokyo and Osaka from six hours to three hours. By 1962, about 17 miles of the proposed line were completed for test purposes. During the next two years, prototype trains were tested to correct flaws and make improvements in the design. The entire project was completed on schedule in July, 1964, with total construction costs of more than $1 billion, double the original estimates. The Speeding Bullet Service on the Shinkansen, or New Trunk Line, began on October 1, 1964, ten days before the opening of the Olympic Games. Commonly called the “bullet train” because of its shape and speed, the Shinkansen was an instant success with the public, both in Japan and abroad. As promised, the time required to travel between Tokyo and Osaka was cut in half. Initially, the system provided daily services of sixty trains consisting of twelve cars each, but the number of scheduled trains was almost doubled by the end of the year. The Shinkansen was able to operate at its unprecedented speed because it was designed and operated as an integrated system, making use of countless technological and scientific developments. Tracks followed the standard gauge of 56.5 inches, rather than the more narrow gauge common in Japan. For extra strength, heavy welded rails were attached directly onto reinforced concrete slabs. The minimum radius of a curve was 8,200 feet, except where sharper curves were mandated by topography. In many ways similar to modern airplanes, the railway cars were made airtight in order to prevent ear discomfort caused by changes in pressure when trains enter tunnels. The Shinkansen trains were powered by electric traction motors, with four 185-kilowatt motors on each car—one motor attached to each axle. This design had several advantages: It provided an even distribution of axle load for reducing strain on the tracks; it allowed the application of dynamic brakes (where the motor was used for braking) on all axles; and it prevented the failure of one or two units from interrupting operation of the entire train. The 25,000-volt electrical current was carried by trolley wire to the cars, where it was rectified into a pulsating current to drive the motors. The Shinkansen system established a casualty-free record because of its maintenance policies combined with its computerized Centralized Traffic Control system. The control room at Tokyo Station was designed to maintain timely information about the location of all trains and the condition of all routes. Although train operators had some discretion in determining speed, automatic brakes also operated to ensure a safe distance between trains. At least once each month, cars were thoroughly inspected; every ten days, an inspection train examined the conditions of tracks, communication equipment, and electrical systems. Impact Public usage of the Tokyo-Osaka bullet train increased steadily because of the system’s high speed, comfort, punctuality, and superb safety record. Businesspeople were especially happy that the rapid service allowed them to make the round-trip without the necessity of an overnight stay, and continuing modernization soon allowed nonstop trains to make a one-way trip in two and one-half hours, requiring speeds of 160 miles per hour in some stretches. By the early 1970’s, the line was transporting a daily average of 339,000 passengers in 240 trains, meaning that a train departed from Tokyo about every ten minutes The popularity of the Shinkansen system quickly resulted in demands for its extension into other densely populated regions. In 1972, a 100-mile stretch between Osaka and Okayama was opened for service. By 1975, the line was further extended to Hakata on the island of Kyushu, passing through the Kammon undersea tunnel. The cost of this 244-mile stretch was almost $2.5 billion. In 1982, lines were completed from Tokyo to Niigata and from Tokyo to Morioka. By 1993, the system had grown to 1,134 miles of track. Since high usage made the system extremely profitable, the sale of the JNR to private companies in 1987 did not appear to produce adverse consequences. The economic success of the Shinkansen had a revolutionary effect on thinking about the possibilities of modern rail transportation, leading one authority to conclude that the line acted as “a savior of the declining railroad industry.” Several other industrial countries were stimulated to undertake large-scale railway projects; France, especially, followed Japan’s example by constructing highspeed electric railroads from Paris to Nice and to Lyon. By the mid- 1980’s, there were experiments with high-speed trains based on magnetic levitation and other radical innovations, but it was not clear whether such designs would be able to compete with the Shinkansen model.

Bubble memory

The invention: An early nonvolatile medium for storing information on computers. The person behind the invention: Andrew H. Bobeck (1926- ), a Bell Telephone Laboratories scientist Magnetic Technology The fanfare over the commercial prospects of magnetic bubbles was begun on August 8, 1969, by a report appearing in both The New York Times and TheWall Street Journal. The early 1970’s would see the anticipation mount (at least in the computer world) with each prediction of the benefits of this revolution in information storage technology. Although it was not disclosed to the public until August of 1969, magnetic bubble technology had held the interest of a small group of researchers around the world for many years. The organization that probably can claim the greatest research advances with respect to computer applications of magnetic bubbles is Bell Telephone Laboratories (later part of American Telephone and Telegraph). Basic research into the properties of certain ferrimagnetic materials started at Bell Laboratories shortly after the end of World War II (1939-1945). Ferrimagnetic substances are typically magnetic iron oxides. Research into the properties of these and related compounds accelerated after the discovery of ferrimagnetic garnets in 1956 (these are a class of ferrimagnetic oxide materials that have the crystal structure of garnet). Ferrimagnetism is similar to ferromagnetism, the phenomenon that accounts for the strong attraction of one magnetized body for another. The ferromagnetic materials most suited for bubble memories contain, in addition to iron, the element yttrium or a metal from the rare earth series. It was a fruitful collaboration between scientist and engineer, between pure and applied science, that produced this promising breakthrough in data storage technology. In 1966, Bell Laboratories scientist Andrew H. Bobeck and his coworkers were the first to realize the data storage potential offered by the strange behavior of thin slices of magnetic iron oxides under an applied magnetic field. The first U.S. patent for a memory device using magnetic bubbles was filed by Bobeck in the fall of 1966 and issued on August 5, 1969. Bubbles Full of Memories The three basic functional elements of a computer are the central processing unit, the input/output unit, and memory. Most implementations of semiconductor memory require a constant power source to retain the stored data. If the power is turned off, all stored data are lost. Memory with this characteristic is called “volatile.” Disks and tapes, which are typically used for secondary memory, are “nonvolatile.” Nonvolatile memory relies on the orientation of magnetic domains, rather than on electrical currents, to sustain its existence. One can visualize by analogy how this will work by taking a group of permanent bar magnets that are labeled withNfor north at one end and S for south at the other. If an arrow is painted starting from the north end with the tip at the south end on each magnet, an orientation can then be assigned to a magnetic domain (here one whole bar magnet). Data are “stored” with these bar magnets by arranging them in rows, some pointing up, some pointing down. Different arrangements translate to different data. In the binary world of the computer, all information is represented by two states. A stored data item (known as a “bit,” or binary digit) is either on or off, up or down, true or false, depending on the physical representation. The “on” state is commonly labeled with the number 1 and the “off” state with the number 0. This is the principle behind magnetic disk and tape data storage. Now imagine a thin slice of a certain type of magnetic material in the shape of a 3-by-5-inch index card. Under a microscope, using a special source of light, one can see through this thin slice in many regions of the surface. Darker, snakelike regions can also be seen, representing domains of an opposite orientation (polarity) to the transparent regions. If a weak external magnetic field is then applied by placing a permanent magnet of the same shape as the card on the underside of the slice, a strange thing happens to the dark serpentine pattern—the long domains shrink and eventually contract into “bubbles,” tiny magnetized spots. Viewed from the side of the slice, the bubbles are cylindrically shaped domains having a polarity opposite to that of the material on which they rest. The presence or absence of a bubble indicates either a 0 or a 1 bit. Data bits are stored by moving the bubbles in the thin film. As long as the field is applied by the permanent magnet substrate, the data will be retained. The bubble is thus a nonvolatile medium for data storage.Consequences Magnetic bubble memory created quite a stir in 1969 with its splashy public introduction. Most of the manufacturers of computer chips immediately instituted bubble memory development projects. Texas Instruments, Philips, Hitachi, Motorola, Fujitsu, and International Business Machines (IBM) joined the race with Bell Laboratories to mass-produce bubble memory chips. Texas Instruments became the first major chip manufacturer to mass-produce bubble memories in the mid-to-late 1970’s. By 1990, however, almost all the research into magnetic bubble technology had shifted to Japan. Hitachi and Fujitsu began to invest heavily in this area. Mass production proved to be the most difficult task. Although the materials it uses are different, the process of producing magnetic bubble memory chips is similar to the process applied in producing semiconductor-based chips such as those used for random access memory (RAM). It is for this reason that major semiconductor manufacturers and computer companies initially invested in this technology. Lower fabrication yields and reliability issues plagued early production runs, however, and, although these problems have mostly been solved, gains in the performance characteristics of competing conventional memories have limited the impact that magnetic bubble technology has had on the marketplace. The materials used for magnetic bubble memories are costlier and possess more complicated structures than those used for semiconductor or disk memory. Speed and cost of materials are not the only bases for comparison. It is possible to perform some elementary logic with magnetic bubbles. Conventional semiconductor-based memory offers storage only. The capability of performing logic with magnetic bubbles puts bubble technology far ahead of other magnetic technologies with respect to functional versatility. Asmall niche market for bubble memory developed in the 1980’s. Magnetic bubble memory can be found in intelligent terminals, desktop computers, embedded systems, test equipment, and similar microcomputer- based systems.