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Error-riddled astronomical tables inspired the first computer—and the first vaporware
During Charles Babbage’s lifetime, this 2,000-part clockwork was as near to completion as his Difference Engine ever got.
It was an idea born of frustration, or at least that’s how Charles Babbage would later recall the events of the summer of 1821. That fateful summer, Babbage and his friend and fellow mathematician John Herschel were in England editing astronomical tables. Both men were founding members of the Royal Astronomical Society, but editing astronomical tables is a tedious task, and they were frustrated by all of the errors they found. Exasperated, Babbage exclaimed, “I wish to God these calculations had been executed by steam.” To which Herschel replied, “It is quite possible.“
Babbage and Herschel were living in the midst of what we now call the Industrial Revolution, and steam-powered machinery was already upending all types of business. Why not astronomy too?
Babbage set to work on the concept for a Difference Engine, a machine that would use a clockwork mechanism to solve polynomial equations. He soon had a small working model (now known as Difference Engine 0), and on 14 June 1822, he presented a one-page “Note respecting the Application of Machinery to the Calculation of Astronomical Tables” to the Royal Astronomical Society. His note doesn’t go into much detail—it’s only one page, after all—but Babbage claimed to have “repeatedly constructed tables of squares and triangles of numbers” as well as of the very specific formula x2 + x + 41. He ends his note with much optimism: “From the experiments I have already made, I feel great confidence in the complete success of the plans I have proposed.” That is, he wanted to build a full-scale Difference Engine.
Perhaps Babbage should have tempered his enthusiasm. His magnificent Difference Engine proved far more difficult to build than his note suggested.
It wasn’t for lack of trying, or lack of funds. For Babbage managed to do something else that was almost as unimaginable: He convinced the British government to fund his plan. The government saw the value in a machine that could calculate the many numerical tables used for navigation, construction, finance, and engineering, thereby reducing human labor (and error). With an initial investment of £1,700 in 1823 (about US $230,000 today), Babbage got to work.
The 19th-century mathematician Charles Babbage’s visionary contributions to computing were rediscovered in the 20th century.The Picture Art Collection/Alamy
Babbage based his machine on the mathematical method of finite differences, which allows you to solve polynomial equations in a series of iterative steps that compare the differences in the resulting values. This method had the advantage of requiring simple addition only, which was easier to implement using gear wheels than one based on multiplication and division would have been. (The Computer History Museum has an excellent description of how the Difference Engine works.) Although Babbage had once dreamed of a machine powered by steam, his actual design called for a human to turn a crank to advance each iteration of calculations.
Difference Engine No. 1 was divided into two main parts: the calculator and the printing mechanism. Although Babbage considered using different numbering systems (binary, hexadecimal, and so on), he decided to stick with the familiarity of the base-10 decimal system. His design in 1830 had a capacity of 16 digits and six orders of difference. Each number value was represented by its own wheel/cam combination. The wheels represented only whole numbers; the machine was designed to jam if a result came out between whole numbers.
As the calculator cranked out the results, the printing mechanism did two things: It printed a table while simultaneously making a stereotype mold (imprinting the results in a soft material such as wax or plaster of paris). The mold could be used to make printing plates, and because it was made at the same time as the calculations, there would be no errors introduced by humans copying the results.
Difference Engine No. 1 contained more than 25,000 distinct parts, split roughly equally between the calculator and the printer. The concepts of interchangeable parts and standardization were still in their infancy. Babbage thus needed a skilled craftsman to manufacture the many pieces. Marc Isambard Brunel, part of the father-and-son team of engineers who had constructed the first tunnel under the Thames, recommended Joseph Clement. Clement was an award-winning machinist and draftsman whose work was valued for its precision.
Babbage and Clement were both brilliant at their respective professions, but they often locked horns. Clement knew his worth and demanded to be paid accordingly. Babbage grew concerned about costs and started checking on Clement’s work, which eroded trust. The two did produce a portion of the machine [shown at top] that was approximately one-seventh of the complete engine and featured about 2,000 moving parts. Babbage demonstrated the working model in the weekly soirees he held at his home in London.
The machine impressed many of the intellectual society set, including a teenage Ada Byron, who understood the mathematical implications of the machine. Byron was not allowed to attend university due to her sex, but her mother supported her academic interests. Babbage suggested several tutors in mathematics, and the two remained correspondents over their lifetimes. In 1835, Ada married William King. Three years later, when he became the first Earl of Lovelace, Ada became Countess of Lovelace. (More about Ada Lovelace shortly.)
Despite the successful chatter in society circles about Babbage’s Difference Engine, trouble was brewing—cost overruns, political opposition to the project, and Babbage and Clement’s personality differences, which were causing extreme delays. Eventually, the relationship between Babbage and Clement reached a breaking point. After yet another fight over finances, Clement abruptly quit in 1832.
Ada Lovelace championed Charles Babbage’s work by, among other things, writing the first computer algorithm for his unbuilt Analytical Engine.Interim Archives/Getty Images
Despite these setbacks, Babbage had already started developing a more ambitious machine: the Analytical Engine. Whereas the Difference Engine was designed to solve polynomials, this new machine was intended to be a general-purpose computer. It was composed of several smaller devices: one to list the instruction set (on punch cards popularized by the Jacquard loom); one (called the mill) to process the instructions; one (which Babbage called the store but we would consider the memory) to store the intermediary results; and one to print out the results.
In 1840 Babbage gave a series of lectures in Turin on his Analytical Engine, to much acclaim. Italian mathematician Luigi Federico Menabrea published a description of the engine in French in 1842, “Notions sur la machine analytique.” This is where Lady Lovelace returns to the story.
Lovelace translated Menabrea’s description into English, discreetly making a few corrections. The English scientist Charles Wheatstone, a friend of both Lovelace and Babbage, suggested that Lovelace augment the translation with explanations of the Analytical Engine to help advance Babbage’s cause. The resulting “Notes,” published in 1843 in Richard Taylor’s Scientific Memoirs, was three times the length of Menabrea’s original essay and contained what many historians consider the first algorithm or computer program. It is quite an accomplishment to write a program for an unbuilt computer whose design was still in flux. Filmmakers John Fuegi and Jo Francis captured Ada Lovelace’s contributions to computing in their 2003 documentary Ada Byron Lovelace: To Dream Tomorrow. They also wrote a companion article published in the IEEE Annals of the History of Computing, entitled “Lovelace & Babbage and the Creation of the 1843 ‘Notes’.”
Although Lovelace’s translation and “Notes” were hailed by leading scientists of the day, they did not win Babbage any additional funding. Prime Minister Robert Peel had never been a fan of Babbage’s; as a member of Parliament back in 1823, he had been a skeptic of Babbage’s early design. Now that Peel was in a position of power, he secretly solicited condemnations of the Difference Engine. In a stormy meeting on 11 November 1842, the two men argued past each other. In January 1843, Babbage was informed that Parliament was sending the finished portion of Difference Engine No. 1 to the King’s College Museum. Two months later, Parliament voted to withdraw support for the project. By then, the government had spent £17,500 (about US $3 million today) and waited 20 years and still didn’t have a working machine. You could see why Peel thought it was a waste.
But Babbage, perhaps reinvigorated by his work on the Analytical Engine, decided to return to the Difference Engine in 1846. Difference Engine No. 2 required only 8,000 parts and had a much more elegant and efficient design. He estimated it would weigh 5 tons and measure 11 feet long and 7 feet high. He worked for another two years on the machine and left 20 detailed drawings, which were donated to the Science Museum after he died in 1871.
In 1985, a team at the Science Museum in London set out to build the streamlined Difference Engine No. 2 based on Babbage’s drawings. The 8,000-part machine was finally completed in 2002.Science Museum Group
Although Difference Engine No. 2, like all the other engines, was never completed during Babbage’s lifetime, a team at the Science Museum in London set out to build one. Beginning in 1985, under the leadership of Curator of Computing Doron Swade, the team created new drawings adapted to modern manufacturing techniques. In the process, they sought to answer a lingering question: Was 19th-century precision a limiting factor in Babbage’s design? The answer is no. The team concluded that if Babbage had been able to secure enough funding and if he had had a better relationship with his machinist, the Difference Engine would have been a success.
That said, some of the same headaches that plagued Babbage also affected the modern team. Despite leaving behind fairly detailed designs, Babbage left no introductory notes or explanations of how the pieces worked together. Much of the groundbreaking work interpreting the designs was done by Australian computer scientist and historian Allan G. Bromley, beginning in 1979. Even so, the plans had dimension inconsistencies, errors, and entire parts omitted (such as the driving mechanism for the inking), as described by Swade in a 2005 article for the IEEE Annals of the History of Computing.
The team had wanted to complete the Difference Engine by 1991, in time for the bicentenary of Babbage’s birth. They did finish the calculating section by then. But the printing and stereotyping section—the part that would have alleviated all of Babbage’s frustrations in editing those astronomical tables—took another nine years. The finished product is on display at the Science Museum.
A duplicate engine was built with funding from former Microsoft chief technology officer Nathan Myhrvold. The Computer History Museum displayed that machine from 2008 to 2016, and it now resides in the lobby of Myhrvold’s Intellectual Ventures in Bellevue, Wash.
The title of the textbook for the very first computer science class I ever took was The Analytical Engine. It opened with a historical introduction about Babbage, his machines, and his legacy. Babbage never saw his machines built, and after his death, the ideas passed into obscurity for a time. Over the course of the 20th century, though, his genius became more clear. His work foreshadowed many features of modern computing, including programming, iteration, looping, and conditional branching. These days, the Analytical Engine is often considered an invention 100 years ahead of its time. It would be anachronistic and ahistorical to apply today’s computer terminology to Babbage’s machines, but he was clearly one of the founding visionaries of modern computing.
Part of a continuing series looking at photographs of historical artifacts that embrace the boundless potential of technology.
An abridged version of this article appears in the June 2022 print issue as “The Clockwork Computer."
Allison Marsh is a professor at the University of South Carolina and codirector of the university's Ann Johnson Institute for Science, Technology & Society. She combines her interests in engineering, history, and museum objects to write the Past Forward column, which tells the story of technology through historical artifacts.
LEDs came only in shades of red—until George Craford expanded the palette
Walk through half a football field’s worth of low partitions, filing cabinets, and desks. Note the curved mirrors hanging from the ceiling, the better to view the maze of engineers, technicians, and support staff of the development laboratory. Shrug when you spot the plastic taped over a few of the mirrors to obstruct that view.
Go to the heart of this labyrinth and there find M. George Craford, R&D manager for the optoelectronics division of Hewlett-Packard Co., San Jose, Calif. Sitting in his shirtsleeves at an industrial beige metal desk piled with papers, amid dented bookcases, gym bag in the corner, he does not look like anybody’s definition of a star engineer.
This article was first published as “M. George Craford.” It appeared in the February 1995 issue of IEEE Spectrum. A PDF version is available on IEEE Xplore. The photographs appeared in the original print version.
“Take a look around during the next few days,” advised Nick Holonyak Jr., the John Bardeen professor of electrical and computer engineering and physics at the University of Illinois, Urbana, and the creator of the first LEDs. “Every yellow light-emitting diode you see—that’s George’s work.”
Holonyak sees Craford as an iceberg—showing a small tip but leaving an amazing breadth and depth unseen. Indeed, Craford does prove to be full of surprises—the gym bag, for example. He skips lunch for workouts in HP’s basement gym, he said, to get in shape for his next adventure, whatever that might be. His latest was climbing the Grand Teton; others have ranged from parachute jumping to whitewater canoeing.
His biggest adventure, though, has been some 30 years of research into light-emitting diodes.
When Craford began his education for a technical career, inthe 1950s, LEDs had yet to be invented. It was the adventure of outer space that called to him.
The Iowa farm boy was introduced to science by Illa Podendorf, an author of children’s science books and a family friend who kept the young Craford supplied with texts that suited his interests. He dabbled in astronomy and became a member of the American Association of Variable Star Observers. He built rockets. He performed chemistry experiments, one time, he recalls with glee, generating an explosion that cracked a window in his home laboratory. When the time came, in 1957, to pick a college and a major, he decided to pursue space science, and selected the University of Iowa, in Iowa City, because space pioneer James Van Allen was a physics professor there.
Wife, Carol; two adult sons, David and Stephen
BA in physics, University of Iowa, 1961; MS and PhD in physics, University of Illinois, 1963 and 1967
Analyzing satellite data from space
Explorer and adventurer Sir Richard Burton, photographer Galen Rowell, Nobel Prize winner John Bardeen, LED pioneer Nick Holonyak Jr.
Scientific American, Sports Illustrated, National Geographic, Business Week
“I don’t use one”
Dining room at San Francisco’s Ritz Carlton Hotel
Bridge on the River Kwai, Butch Cassidy and the Sundance Kid, The Lion in Winter
Hiking, walking, snow skiing, bicycling, tennis, and, most recently, technical mountain climbing.
Sable Wagon (a company car)
“People that work for me who don’t come to me with little problems, which fester and turn into big ones.”
IEEE, Society for Information Display
National Academy of Engineering, IEEE Fellow, IEEE Morris N. Liebmann Memorial Award; but “everything you do is a team thing, so I have mixed feelings about awards.”
As the space race heated up, Craford’s interest in space science waned, in spite of a summer job analyzing data returned from the first satellites. He had learned a bit about semiconductors, an emerging field, and Van Allen pointed him toward the solid-state physics program at the University of Illinois, where Craford studied first for a master’s degree, then a PhD.
For his doctoral thesis, Craford began investigating tunneling effects in Josephson junctions. He had invested several years in that research when Holonyak, a pioneer in visible lasers and light-emitting diodes, left his position at General Electric Co. and joined the Illinois faculty. Craford met him at a seminar, where Holonyak was explaining his work in LEDs. Recalled Craford: “He had a little LED—just a red speck—and he plunged it into a Dewar of liquid nitrogen, and it lit up the whole flask with a bright red light.”
Entranced, Craford immediately spoke to his thesis adviser about switching, a fairly unusual proposal, since it involved dropping years of work. “My thesis adviser was good about it; he had been spending less time around the lab lately, and Holonyak was building up a group, so he was willing to take me on.”
Craford believes he persuaded the laser pioneer to accept him, the senior man recalls things differently.
Craford’s adviser “was running for U.S. Congress,” Holonyak said, “and he told me, ‘I’ve got this good student, but I’m busy with politics, and everything we do someone publishes ahead of me. I can’t take good care of him. I’d like you to pick him up.”’
However it happened, Craford’s career path was finally set—and the lure of the glowing red Dewar never dimmed.
Holonyak was growing gallium arsenide phosphide and using it successfully to get bright LEDs and lasers. He assigned his new advisee the job of borrowing some high-pressure equipment for experiments with the material. After finding a professor with a pressure chamber he was willing to lend, Craford set up work in the basement of the materials research building. He would carry GaAsP samples from the lab to the materials research basement, cool them in liquid nitrogen, increase the pressure to study the variation of resistivity, and see unexpected effects.
“Just cooling some samples would cause the resistance to go up several times. But add pressure, and they would go up several orders of magnitude,” Craford said. “We couldn’t figure out why.”
Eventually, Craford and a co-worker, Greg Stillman, determined that variations in resistance were related not only to pressure but also to light shining on the samples. “When you cooled a sample and then shone the light on it, the resistance went down—way down—and stayed that way for hours or days as long as the sample was kept at low temperature, an effect called persistent photoconductivity.” Further research showed that it occurred in samples doped with sulfur but not tellurium. Craford and Stillman each had enough material for a thesis and for a paper published in the Physical Review.
The phenomenon seemed to have little practical use, and Craford put it out of his mind, until several years later when researchers at Bell Laboratories found it in gallium aluminum arsenide. “Bell Labs called it the DX Center, which was catchy, studied it intensively, and over time, many papers have been published on it by various groups,” Craford said. Holonyak’s group’s contribution was largely forgotten.
“He doesn’t promote himself,” Holonyak said of Craford, “and sometimes this troubles me about George; I’d like to get him to be more forward about the fact that he has done something.”
After receiving his PhD, Craford had several job offers. The most interesting were from Bell Laboratories and the Monsanto Co. Both were working on LEDs, but Monsanto researchers were focusing on gallium arsenide phosphide, Bell researchers on gallium phosphide. Monsanto’s research operation was less well known than Bell Labs’ and taking the Monsanto job seemed to be a bit of a risk. But Craford, like his hero—adventurer Richard Burton, who spent years seeking the source of the Nile—has little resistance to choosing the less well-trodden path.
Besides, “Gallium phosphide just didn’t seem right,” said Craford, “but who knew?”
In his early days at Monsanto, Craford experimented with both lasers and LEDs. He focused on LEDs full time when it became clear that the defects he and his group were encountering in growing GaAsP on GaAs substrates would not permit fabrication of competitive lasers.
[He] didn’t toot his own horn. “When George [Craford] published the work, he put the names of the guys he had growing crystals and putting the things together ahead of his name.” —Nick Holonyak
The breakthrough that allowed Craford and his team to go beyond Holonyak’s red LEDs to create very bright orange, yellow, and green LEDs was prompted, ironically, by Bell Labs. A Bell researcher who gave a seminar at Monsanto mentioned the use of nitrogen doping to make indirect semiconductors act more like direct ones. Direct semiconductors are usually better than indirect for LEDs, Craford explained, but the indirect type still has to be used because of band gaps wide enough to give off light in the green, yellow, and orange part of the spectrum. The Bell researcher indicated that the labs had had considerable success with Zn-O doping of gallium phosphide and some success with nitrogen doping of gallium phosphide. Bell Labs, however, had published early experimental work suggesting that nitrogen did not improve GaAsP LEDs.
Nonetheless, Craford believed in the promise of nitrogen doping rather than the published results. “We decided that we could grow better crystal and the experiment would work for us,” he said.
A small team of people at Monsanto did make it work. Today, some 25 years later, these nitrogen-doped GaAsP LEDs still form a significant proportion—some 5-10 billion—of the 20-30 billion LEDs sold annually in the world today.
“The initial reaction was, ‘Wow, that’s great, but our customers are very happy with red LEDs. Who needs other colors?’” —George Craford
Again, Holonyak complains, Craford didn’t toot his own horn. “When George published the work, he put the names of the guys he had growing crystals and putting the things together ahead of his name.”
His peers, however, have recognized Craford as the creative force behind yellow LEDs, and he was recently made a member of the National Academy of Engineering to honor this work.
Craford recalls that the new palette of LED colors took some time to catch on. “The initial reaction,” he said, “was, ‘Wow, that’s great, but our customers are very happy with red LEDs. Who needs other colors?’”
After the LED work was published, a Monsanto reorganization bumped Craford up from the lab bench to manager of advanced technology. One of his first tasks was to select researchers to be laid off. He recalls this as one of the toughest jobs of his life, but subsequently found that he liked management. “You have more variety; you have more things that you are semi-competent in, though you pay the price of becoming a lot less competent in any one thing,” he told IEEE Spectrum.
Soon, in 1974, he was bumped up again to technology director, and moved from Monsanto’s corporate headquarters in St. Louis to its electronics division headquarters in Palo Alto, Calif. Craford was responsible for research groups developing technology for three divisions in Palo Alto, St. Louis, and St. Peters, Mo. One dealt with compound semiconductors, another with LEDs, and the third with silicon materials. He held the post until 1979.
Even as a manager, he remained a “scientist to the teeth,” said David Russell, Monsanto’s director of marketing during Craford’s tenure as technology director. “He is a pure intellectual scientist to a fault for an old peddler like me.”
Though always the scientist, Craford also has a reputation for relating well to people. “George is able to express complicated technical issues in a way that all of us can understand,” said James Leising, product development manager for HP’s optoelectronics division.
Leising recalled that when he was production engineering manager, a position that occasionally put him in conflict with the research group, “George and I were always able to work out the conflicts and walk away friends. That wasn’t always the case with others in his position.” One time in particular, Leising recalled, Craford convinced the production group of the need for precise control of its processes by graphically demonstrating the intricacies of the way semiconductor crystals fit upon one another.
As an executive, Craford takes credit for no individual achievements at Monsanto during that time, but said, “I was proud of the fact that, somehow, we managed to be worldwide competitors in all our businesses.” Even so, Monsanto decided to sell off its optoelectronics business and offered Craford a job back in St. Louis, where he would have been in charge of research and development in the company’s silicon business.
Craford thought about this offer long and hard. He liked Monsanto; he had a challenging and important job, complete with a big office, oak furniture, a private conference room, and a full-time administrative assistant. But moving back to St. Louis would end his romance with those tiny semiconductor lights that could make a Dewar glow, and when the time came, he just couldn’t do it.
He did the Silicon Valley walk: across the street to the nearest competitor, in this case, Hewlett-Packard Co.
Instead, he did the Silicon Valley walk: across the street to the nearest competitor, in this case, Hewlett-Packard Co. The only job it could find that would let him work with LEDs was a big step down from technology director—a position as R&D section manager, directing fewer than 20 people. This meant a cut in salary and perks, but Craford took it.
The culture was different, to say the least. No more fancy office and private conference room; at HP Craford gets only “a cubby, a tin desk, and a tin chair.”
And, he told Spectrum, “I love it.”
He found the HP culture to be less political than Monsanto’s, and believes that the lack of closed offices promotes collaboration. At HP, he interacts more with engineers, and there is a greater sense that the whole group is pulling together. It is more open and communicative—it has to be, with most engineers’ desks merely 1.5 meters apart. “I like the whole style of the place,” he declared.
Now he has moved up, to R&D manager of HP’s optoelectronics division, with a larger group of engineers under him. (He still has the cubby and metal desk, however.)
As a manager, Craford sees his role as building teams, and judging which kinds of projects are worth focusing on. “I do a reasonably good job of staying on the path between being too conservative and too blue sky,” he told Spectrum. “It would be a bad thing for an R&D manager to say that every project we’ve done has been successful, because then you’re not taking enough chances; however, we do have to generate enough income for the group on what we sell to stay profitable.”
Said Fred Kish, HP R&D project manager under Craford: “We have embarked upon some new areas of research that, to some people, may have been questionable risks, but George was willing to try.”
Craford walks that path between conservatism and risk in his personal life as well, although some people might not believe it, given his penchant for adventurous sports: skydiving, whitewater canoeing, marathon running, and rock climbing. These are measured risks, according to Craford: ‘‘The Grand Teton is a serious mountain, but my son and I took a rock-climbing course, and we went up with a guy who is an expert, so it seemed like a manageable risk.”
Holonyak recalls an occasion when a piece of crystal officially confined to the Monsanto laboratory was handed to him by Craford on the grounds that an experiment Holonyak was attempting was important. Craford “could have gotten fired for that, but he was willing to gamble.”
“I hope to see the day when LEDs will illuminate not just a Dewar but a room.” —George Craford
Craford is also known as being an irrepressible asker of questions.
“His methods of asking questions and looking at problems brings people in the group to a higher level of thinking, reasoning, and problem-solving,’’ Kish said.
Holonyak described Craford as “the only man I can tolerate asking me question after question, because he is really trying to understand.”
Craford’s group at HP has done work on a variety of materials over the past 15 years, including gallium aluminum arsenide for high-brightness red LEDs and, more recently, aluminum gallium indium phosphide for high-brightness orange and yellow LEDs.
The latest generation of LEDs, Craford said, could replace incandescent lights in many applications. One use is for exterior lighting on automobiles, where the long life and small size of LEDs permit car designers to combine lower assembly costs with more unusual styling. Traffic signals and large-area display signs are other emerging applications. He is proud that his group’s work has enabled HP to compete with Japanese LED manufacturers and hold its place as one of the largest sellers of visible-light LEDs in the world.
Craford has not stopped loving the magic of LEDs. “Seeing them out and used continues to be fun,” he told Spectrum. “When I went to Japan and saw the LEDs on the Shinkansen [high-speed train), that was a thrill.”
He expects LEDs to go on challenging other forms of lighting and said, “I still hope to see the day when LEDs will illuminate not just a Dewar but a room.”
Editor’s note: George Craford is currently a fellow at Philips LumiLEDs. He got his wish and then some.