Did the Difference Engine make a difference?

I have been reading a few steampunk novels lately – I have a great fondness for the genre. Charles Babbage’s planned “Difference Engine” and “Analytical Engine” always play a large part in the fictional universe of such books. However, as Francis Spufford has pointed out, this does rely on some counterfactual history.


Reconstructed “Difference Engine No. 2” in the Science Museum, London (photo: “Geni”)

Babbage never completed any of his major devices, although redesigned working difference engines were built by Per Georg Scheutz (1843), Martin Wiberg (1859), and George B. Grant (1876). With much fanfare, the Science Museum, London reconstructed Babbage’s “Difference Engine No. 2” between 1985 and 2002, making only essential fixes to the original design – and it works! However, the pinnacle of this kind of technology was probably the beautiful handheld Curta calculator, produced in Liechtenstein by Curt Herzstark from 1947.

The world’s first programmable digital computer was in fact built four years before the Curta, in 1943, by English electrical engineer Tommy Flowers. The wartime secrecy associated with his work has kept this monumental achievement largely in the dark.


Colossus in action at Bletchley Park in 1943 (photo: National Archives)

The significance of the Colossus has also been obscured by a kind of “personality cult” built up around Alan Turing, much like the one built up around Babbage. Turing was one of a number of people who contributed to the design of the cryptographic “Bombe” at Bletchley Park, and Turing also did important theoretical work – although the fundamental result in Turing’s 1936 paper, “On Computable Numbers, with an Application to the Entscheidungsproblem” was not actually new, as is revealed on the second page of Turing’s paper, where Turing admits “In a recent paper Alonzo Church has introduced an idea of ‘effective calculability,’ which is equivalent to my ‘computability,’ but is very differently defined. Church also reaches similar conclusions about the Entscheidungsproblem . The proof of equivalence between ‘computability’ and ‘effective calculability’ is outlined in an appendix to the present paper.

Turing’s life was more colourful than either Church’s or Flowers’s, however, and this may be why he is far more famous. In a similar way, Babage lived a more colourful life than many of his contemporaries, including his collaboration with the forward-thinking Countess of Lovelace.


1: Charles Babbage, 2: Augusta Ada King-Noel (née Byron, Countess of Lovelace), 3: Alonzo Church, 4: Alan Turing, 5: Tommy Flowers

The chart below (click to zoom) puts the work of Babbage and Flowers in a historical context. Various devices are ranked according to their computational power in decimal digits calculated per second (from 1 up to 1,000,000,000,000,000). Because this varies so dramatically, a logarithmic vertical scale is used. The Colossus marks the beginning of a chain of “supercomputers,” often built for government use, with power doubling every 1.84 years (pink line). Starting with the Intel 4004 in 1971, there is also a chain of silicon chips, with power doubling every 1.74 years (blue line). At any given point in time, supercomputers are between 1,000 and 3,000 times more powerful than the chips, but the chips always catch up around 20 years later. The revolutionary PDP-8 of 1965 sits between the two chains.

One of the things that stand out on this chart is the gap between Babbage’s Difference Engine and the later digital computers – even the Colossus was around 280 times more powerful than the Difference Engine (carrying out a simpler task much more quickly). Steampunk fiction often suggests that steam power would have made the Difference Engine faster. However, it turns out that the mechanism jams if it is cranked too quickly. Complex mechanical calculating devices simply cannot operate that fast.


Morse telegraph key (photo: Hp.Baumeler)

In fact, Charles Babbage may actually have distracted people from the way forward. Samuel Morse’s improved telegraph was officially operational in 1844. It used electromechanical principles that were also used in the Colossus a century later. Electricity also has the advantage of travelling at the speed of light, along wires that can be made extremely thin. What might the world have been like had electromechanical computing developed earlier? The chart also shows the 1964 fluidic computer FLODAC. This was a fascinating idea that was abandoned after a successful proof of concept (although a 1975 film portrayed it as the future). What if that idea had been launched in Victorian Britain?


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Aircraft size comparison

Time for something not about solar cars…

Revisiting my post on the R100 airship, here is a more detailed aircraft size comparison (click to zoom). All aircraft are to scale.


ASC 20: Solar cars and the Oregon Trail

Given that the American Solar Challenge is going to be following the Oregon Trail this year, I thought that it would be fun to do a comparison between the “prairie schooners” of two centuries ago and the solar cars of today.

At the time of the “Great Emigration” of 1843, aluminium was known, but could not yet be produced on an industrial scale (that came in 1854, and was initially very expensive). Steel likewise existed, but the Bessemer process for producing it came later (1855). Fibreglass composites came a century later (1936), and carbon fibre later still. Modern electronics could not even have been imagined. The “prairie schooners” were built using a much older technology.


Prairie schooner and solar car – picture credits NPS (left) and Anthony Dekker (right)

ATTRIBUTE PRAIRIE SCHOONER SOLAR CAR
Dimensions (W × L) 1.2 × 3 m (4 × 10 ft) for wagon bed Up to 2 × 5 m (7 × 16 ft) for entire car
Horsepower 4 to 12 hp 1 hp solar power for Challengers (SOV), up to 4 hp mixed solar/grid power for Cruisers (MOV)
Sustained speed 3 km/h (2 mph) 50 to 75 km/h (30 to 45 mph)
Empty weight 600 kg (1300 lb) 150 to 450 kg (350 to 1000 lb)
Load 900 kg (2000 lb) 80 to 320 kg (200 to 700 lb)
Motive power Horses or oxen Solar cells, battery, and electric motor(s)
Body materials Wood, cotton canvas Steel, aluminium, carbon fibre, fibreglass
Tires Iron Rubber, low rolling resistance

Prairie schooner and solar car – picture credits Albert Bierstadt (left) and Anthony Dekker (right)


Medieval sustainability

There’s a sustainability theme on Scientific Gems this month, and I thought I’d take a look at sustainability in the Middle Ages. The Middle Ages get a lot of unjustified bad press (people did not think the world was flat, for example).

It is more accurate to describe the Middle Ages as a search for sustainability. The rise of Christianity meant the phasing out, and eventual elimination, of slavery in Europe. That meant a need to replace the use of slaves as an energy source. The Middle Ages therefore saw a steady increase in the use of water power, tidal power, and wind power.

Another transformation was needed in agriculture. The collapse of the Western Roman Empire and the Arab invasion of Egypt meant that the rich Egyptian grainfields could no longer feed Europe. European agricultural productivity therefore had to be increased to feed the population, while being sustainable on a time scale of centuries. The mouldboard plough was an important piece of technology here.

Another key development was the introduction of three-way crop rotation. A field produced grain for a year, and was used as pasture the next, thus fertilising the soil with manure. The third year, the field produced legumes, which added nitrogen to the soil, and the cycle repeated again with grain. Three-way crop rotation was both more productive and more sustainable than the older two-way system. There’s a lesson to be learned here, I think.


Fourth of July!

It’s the 4th of July, so I’m celebrating with my American friends.

On this day in 1817, construction began on the Erie Canal in New York state. When completed, it was the second longest canal in the world.

In 1868, Henrietta Swan Leavitt was born. She would go on to discover the period–luminosity relationship for Cepheid variable stars, which provided a way of measuring the universe.

In 1951, Bell Labs and William Shockley announced a successful junction transistor. And in 1997, the Mars Pathfinder (incorporating the Sojourner rover) landed on Mars.


The constellation Scorpius

Winter is here (in the Southern Hemisphere, at least), and the constellation Scorpius always heralds the southern winter’s icy sting. The image below is based on a vintage astronomical illustration, but I have corrected the star positions of the major stars and indicated their apparent magnitude (brightness) and approximate colour (based on spectral class). It is interesting to compare the image with this quality photograph.

Generations of astronomers have memorised the O–B–A–F–G–K–M stellar classification system developed by Annie Jump Cannon with the mnemonic “Oh, Be A Fine Girl/Guy/Gal/Gentleman, Kiss Me.” Scorpius does not contain any bright O-class stars, but it is easy to see stars ranging from the hot blue-white B class to the cooler orange-red M class (stars which are only “red hot”).

The most obvious star in Scorpius is the enormous red supergiant Antares, which has that name because it is easily confused with the planet Mars (Ares). It is also known as “Cor Scorpii” (the heart of the scorpion). It is easy to recognise the curved tail as well, with the stingers Shaula and Lesath at its tip. It is less obvious which stars are the scorpion’s claws – the artist here has drawn the left claw extended so as to reach the dim white star Psi Scorpii. Other artists draw the scorpion facing more to the right, with the line of blue-white stars being the claws.

Infographic constructed using R (with lm to map true sky coordinates to image coordinates, rasterImage for the background, and the showtext package for fonts).


Eureka! – a book review


Eureka!: The Birth of Science by Andrew Gregory

I recently read Eureka!: The Birth of Science by Andrew Gregory. The book deals with a topic that has long fascinated me – the birth of science. In a previous post I argued that this took place in the 12th century, the age of cathedrals. Gregory takes the view that it happened with the ancient Greeks, and sees Aristotle and Archimedes as among science’s pioneers. He gives a brief defence of this thesis, and provides a quick summary of Greek scientific thought.


Aristotle and Archimedes

I found this book rather short for the subject (177 pages, including bibliography), was disappointed at the lack of endnotes, and found some annoying errors (the Greeks did not consider the universe small, for example – Archimedes took it to be 2 light-years across). But the big unanswered question is: what went wrong? Gregory includes a list of key people at the back of the book, and if you turn that list into a bar chart, you can see that Greek science basically fell off a cliff around 200 BC.

In a brief two-page section towards the end, Gregory suggests that Christianity was somehow responsible for the decline of Greek science, but that simply makes no sense. Was it instead Roman conquest, beginning around 280 BC? Was it the growing separation of aristocratic philosophy from plebeian technology? Was it the replacement of original science by encyclopaedic systematisation (such as that of Pliny)? It would have been nice to have those questions answered.

Goodreads gives this book 3.4 stars; I was rather less enthusiastic.


Eureka!: The Birth of Science by Andrew Gregory: 2 stars