by Adrian Berry
The bugs in such vast programs cannot all be found by printing out the source code and scanning it by eye. The program has to be exhaustively tested, which means discovering how it will behave in all conceivable circumstances. But there will always be circumstances that the programmer has not thought of, and there the bugs will lurk. In the words of , a computer expert at SRI International in Menlo Park, California: ‘Guaranteed system behaviour is impossible to achieve.’
Obvious errors are easily spotted. If part of the program that asks the user for information contains the word IMPUT instead of INPUT, the program will pronounce: ‘syntax error’, and wait for it to be corrected. But more subtle errors will be less easily found. Some have had amusing consequences, and some tragic:
• A ‘Political Analyst’ program of the seventies, designed as an experiment to make computers behave ‘intelligently’, announced that the Communist Chinese must have built the Berlin Wall. It concluded this because China, under ’s dictatorship, appeared to be the most militant Communist power. The programmer had failed to tell the program that the Chinese did not have access to Berlin.
• A journalist writing an article about the climate on his word processor included the phrase ‘furious gales’. On putting the article through the program’s grammar checker, he was told: ‘This is a disrespectful way to refer to women.’(The programmer had allowed ‘gales’ to be construed as ‘gals’.)
• A popular book on computing contained the source code for what was claimed to be a powerful chess-playing program. I copied it out carefully, checking each line. But when executed, it merely said: ‘Thank you for playing. Another game (Y/N).’
• In 1991, an ‘improvement’ was introduced to the program that runs the American telephone system. ‘It was only a minor change,’ said Newmann, ‘so they assumed they could release it without testing it.’ But it disrupted phones in Pittsburgh, Los Angeles, San Francisco and Washington, and it took weeks to find the bugs.
• During the Gulf War, a seemingly tiny error in the radar and tracking system of the Patriot missile changed its timing by one third of a second. On 25 February 1991, it missed an incoming Scud missile which killed 29 American soldiers in a Saudi Arabian barracks.
Since even a comparatively simple program can be more complicated than a motor car, commercial programs are usually not written by individuals but by teams. Each member writes his own ‘module’, and at the end they are all stuck together to make one entity.
The danger comes when one team-member has tried to be too clever or not imaginative enough, and the modules do not fit properly. Bugs can often be eliminated by introducing a new ‘rule’ to the existing program that says: ‘If such-and-such is the case, then do so-and-so.’ The Literary Analyst would not have made its mistake about Dickens if the programmer had remembered to tell it that people reach intellectual maturity at the age of 18.
Tentacles from the Sea
People who take Mediterranean holidays cannot always plunge safely into the cool sea. For they may be in peril from that most dangerous and beautiful marine object, the ubiquitous jellyfish.
From the English coasts to the beaches of Australia, hundreds of swimmers and divers are killed or severely injured by jellyfish every year. Whether it is due to some peculiarity of wind and current, or the reopening of the Suez Canal (theories abound, but nobody really knows the reason), Mediterranean waters seem more infested than ever. Glittering Aegean bays that yesterday were free of them can turn today into menageries of sinister floating shapes. The deadliest species of all is Chironex fleckeri, the so-called box jelly, also known as the sea wasp. It can kill in seconds.
On the northern coast of Australia, beach guards have adopted an extraordinary means of protecting themselves. They wear two pairs of women’s pantyhose, one for the legs and the other worn upside down for the torso, with a hole cut in the crotch for the head. Experts assure us that the box jellies are to be found only between the Tropic of Capricorn and the Equator, that is to say in the southern seas. But experts are often wrong, particularly in the mysteries of marine biology.
These creatures might, for all we know, be migrating northwards. A box jelly is similar in appearance to many other species of jellyfish. It has a small bell-shaped body, about 25 centimetres across and, less visibly, some sixty 18-metre tentacles trailing beneath them. The tentacles are covered with millions of ‘nematocysts’, derived from the Greek word , meaning thread. They contain the stings. A nematocyst fires out toxins like a tiny gun with such force that it can penetrate a glove, although not, apparently, pantyhose.
A single jellyfish can have several types of nematocyst, each with a different poison. Some stop the heart of an adult by interfering with the passage of calcium through the myocardial membrane. Another disrupts the circulatory system by destroying red blood cells. A third can penetrate the brain and stop the victim from breathing.
More commonly, multiple stings can produce hideous welts all over the body, accompanied by headache, nausea and fever. These welts, found on two dead men formed the mystery of the story ‘The Lion’s Mane’. They seemed to have been flogged to death: but had made a rare mistake, for the stings of that huge lion’s mane jellyfish with its 600-metre tentacles are usually too mild to be dangerous.
Only a few dozen of the approximately 500 known species of jellyfish are dangerous to humans. And people are affected in different ways. Some take no ill effect; others, with allergies, are laid low.
Why has nature, in the form of evolution by natural selection, filled the seas with such horrible creatures? The answer, according to scientists, is that the jellyfish need their stings for protection and to prey on fish, and it is just bad luck that humans are poisoned by their venom.
A jellyfish has nothing that we could call a brain. A shark is a genius by comparison. Like the ’s fly-trap plant, a jellyfish attacks by instinct rather than by calculation. Yet instinctive behaviour can be extraordinarily complex. There is one species of jellyfish known as Velella velella which, instead of moving with the current, actually sails. It sticks a fin out of the water which the wind propels. It is not a particularly ‘good’ sailor, for it ‘tacks’ up to 60 degrees from the wind direction. And stranger still, there appear to be two species of velella, those that sail on the starboard tack and those that sail on the port.
Do these species intermingle? Nobody knows. Big jellyfish like the Portuguese man-of-war and the box jelly are formidable enough, but who knows what monstrous jelly-cousins, with awful destructive powers, may exist at the bottom of the deepest oceans, tens of thousands of metres down, where animals grow to gigantic sizes? Those who explore the depths of the seas in manned submersibles may soon be making some unpleasant discoveries.
Rushing for Emerald
An ‘emerald rush’ may follow reports that explain for the first time the ideal natural conditions for the production of these most lustrous green gems. Ever since the Spanish conquistadors looted the silver, diamond and emerald mines of South America in the sixteenth century, it has been known that emeralds with the finest inner lustre are found only in Colombia, the world’s leading emerald producer, where - unlike diamonds or other precious gems -they are formed differently from anywhere else.
The reports have set off a search for new emerald mines whose gem quality may match that of Colombia, and also put an end to the dreams of alchemists through the ages who have tried to manufacture them.
Emeralds are much rarer than diamonds and, ounce for ounce, are thousands of times more valuable than gold. In one recent year alone, Colombian exports of emeralds produced revenues of £41 million. This may explain why, in Colombia, emeralds can fetch 50 times more money than cocaine, and dealing in them can be an extremely violent business. An estimated 4,000 people were killed in a five-year ‘green war’ that ended in 1992.
It was once believed that producing the best emeralds was a matter of alchemical skill. , of the Scottish Universities Research and Reactor Centre in , wr
iting in Nature, has unearthed this splendid passage from an anonymous tract called the Papyrus Graecus Holmiensis, written in Egypt about AD 400:
‘For the preparation of emerald: mix together in a small jar Vi drachma of copper green (verdigris), lh drachma of Armenian blue (chrysocolla), xh cup of the urine of an uncorrupted youth and % the fluid of a steer’s gall. Put into this the stones, about 24 pieces weighing about V2 obolus [a gold or silver coin] each. Put the lid on the jar, seal the lid all around with clay, and heat for six hours over a gentle fire made of olive-wood. You will find they have become emeralds.’
But Colombian geology creates emeralds much more efficiently than the lavatorial leavings of uncorrupted youths. Most important is the presence of sulphur. At Muzo, in bandit-infested country some 60 miles from Bogota and Colombia’s most famous emerald mine, geologists discovered a region where millions of years ago sulphates dissolved in salty hot water. As Fallick points out: ‘When the sulphur reacts with organic matter to release chromium, vanadium and beryllium, the essential ingredients of the best quality emeralds, it removes from them the iron impurities which elsewhere quench their natural luminescence.’
Emerald lovers will be enthusiastic for many reasons. Prized for their beauty at least since 1650 bc when emeralds were mined in Upper Egypt, they have long been reputed in legend as cures for bad eyesight and epilepsy, an aid for women in childbirth, and for driving away evil spirits and blinding snakes and dragons.
Two stories, ‘The Beryl Coronet’ and ‘The Six Napoleons’, are about stolen emeralds while the anonymous 1889 poem ‘Birth-stones’ contains this sentimental verse:
Who first beholds the light of day
In Spring’s sweet flowery month of May
And wears an emerald all her life,
Shall be a loved and happy wife.
One of the world’s largest emeralds, a 430-carat carved gem the size of a small apple, was recently sold to an anonymous buyer at Bonhams in London for £231,000. Although this was the largest single emerald ever sold at an auction, it barely compared in size with an 86,136-carat gem found in Brazil in 1974, valued at £718,000.
The 430-carat emerald had a typical history. Originating in Colombia, it was carved for a high official at the Mogul court in India in about 1695. Indian rulers wore emeralds as often as possible in the mystical belief that displaying them in public would preserve their wealth.
The search for emerald mines to match the quality of Colombia has thrown up geologically favourable areas in Brazil, Australia, Pakistan, India and Afghanistan. Of these, Afghanistan, where the Mujahideen used emeralds to finance their war against the Soviet Union, may be a hazardous place to look.
Nature is by far the best producer of emeralds. It will probably never be safe to make them at home in basements. ‘The element beryllium is extremely dangerous to handle and its dust and fumes can cause fatal illness,’ said , of the Royal Ontario Museum in Toronto.
Spitting Images and Fatal Errors
When Aberdeen University zoologist and his staff enter their laboratory they wear surgical masks and goggles and carry grappling sticks. It is the home of 12 deadly snakes, including several spitting cobras whose venom can cause blindness, serious injury or even death.
‘Unlike the cunning rock python Kaa in ’s Jungle Book, snakes are extremely stupid,’ says . ‘They do not recognize individual people, and spitting cobras in particular are very bad tempered. They can cover you with venom from a range of two metres.’
With the aid of computerized databases, he and his colleague are making remarkable discoveries about venomous snakes, leading to important changes in the treatment of people who suffer snakebite.
‘There are about 400 species of deadly snakes,’ says , ‘and about 2,500 non-deadly ones. About 40,000 people are killed by the deadly variety every year, and more than 10 times that number suffer lasting injuries, ranging from dead skin-tissue to gangrene. The problem, all too often, is that victims are given the wrong antidote, because it was designed to counter the venom of a different snake.
‘Detailed studies, never carried out until now, have shown us that many of these animals belong to completely different species, with common ancestors who lived millions of years ago. The result of these evolutionary divergences is that they have different venoms which require different antidotes.’
Asiatic cobras, found from semi-desert Central Asia to tropical Indonesia, look the same at a cursory glance and are lumped together as a single species known as Naja naja. But that name ought to belong solely to the Indian spectacled cobra, found in India, Sri Lanka, Pakistan, Nepal and Bangladesh.
The misunderstanding among experts outside the sub-continent is ‘little short of stunning’, says Wuster. Because the difference was not appreciated, cobra victims elsewhere in Asia have been treated with the antidote for Naja naja, often with fatal results. and his team have now found from the evidence of their snakes’ scales, colour patterns and position of internal organs that there are at least ten species of Asiatic cobra.
Unfortunately the attitudes of the snake scientists have differed as markedly as the snakes themselves. Biologists who study snakes for general scientific reasons, and those like and Wuster who try to classify them into species with an eye to developing correct antidotes, seem to live in different parallel universes. ‘They hold us in disdain,’ Wuster complains. ‘We are often regarded as rather pompous people sitting in museum back rooms, counting scales all day and confusing everyone by changing scientific names for no good reason.’
One case of bad decision-making resulting from this attitude led to considerable loss of life among rice farmers living in a densely populated region of Malaysia and Thailand. Also living there are two species of snake of almost identical appearance, the monocellate cobra and the equatorial spitting cobra.
Despite obvious differences in size, colour patterns and behaviour, the distinction between the two species was largely unreported in scientific literature. Authorities added to the confusion. Thailand manufactured and distributed an antidote against the venom of the first snake, while the Malaysian antidote was effective only against that of the second. Not surprisingly, people bitten by the one and treated for a bite by the other died or became seriously ill.
Nobody is proposing the extermination of venomous snakes, since non-venomous kinds would inevitably be destroyed along with them, and without snakes the rat population would explode, with consequent destruction of crops. ‘Only a snake is narrow enough to crawl into a rat burrow and eat their litter,’ says .
Instead, there is a growing belief that dangerous animals must be protected to preserve genetic diversity. ‘To do both this and protect human life at the same time,’ says Wuster, ‘the best approach is to ask the simple but fundamental question: What’s what? ‘
Nonsense on the Screen
Why did the science fiction film Terminator II, Judgement Day pack cinemas throughout the country when it appeared in 1991?
It was not just that its estimated budget of $100 million made it the most expensive film ever made, nor because of its tremendous special effects; but rather because audiences found the exciting story plausible and therefore suspected it might be good science. While some of its scenes are over the top, its general scientific quality is an extraordinary improvement on the kind of SF films that were being made in earlier decades.
In those days producers knew practically nothing about science; they made no effort to learn any, and their ignorance showed. Laughter rather than fascination or horror was the reaction they all too often evoked. Typical of this genre was The Blob (1958) about a ‘creature’ that invades a small town. Where this creature comes from is unclear, but the most ridiculous scene is in a cinema where the film mysteriously stops because the Blob is eating the projectionist. Yet its theme song was a classic:
Beware of the Blob.
It creeps and leaps
And slides and glides
Right through the floor
> Around the wall.
A splotch, a blotch,
Be careful of the Blob!
Another creature intended to frighten but which only evoked mirth was the dinosaur aroused from age-long marine slumber by nuclear bomb tests in The Beast from Twenty Thousand Fathoms (1953). ‘It’s hiding somewhere in the Wall Street area,’ says a character hilariously as the beast rampages through New York in a predictable imitation of the first King Kong (1933).
But the real problem with The Beast was its title. With two metres to a fathom, it must have lived at 36,000 metres beneath the sea. But this demonstrated inexcusable ignorance by the producers. For only two years before the film was made, the British survey ship Challenger had located the deepest part of the ocean then known (in the Marianas Trench in the Pacific) at only 11,000 metres. For an air breathing animal to live at the bottom of the sea would be odd, but for it to survive for millions of years 16 miles under the sea bed was downright amazing.
Some ignorance was excusable. Until the flight of in 1961 and unmanned missions to the Moon and planets in the 60s, even scientists knew little about space. And the astronomer had misled everyone in the 1890s when he claimed to have observed signs of an intelligent civilization on Mars. This made possible such splendid films as The War of the Worlds (1953), a story of the invasion of Earth by advanced and ruthless Martians, and the ominous Quatermass Experiment (1955).
Quatermass was particularly sinister since it implied that space - not planetary surfaces but space itself - was filled with blood-drinking animals that were liable to break into spaceships and devour their inmates. On his return to Earth, the one surviving astronaut gradually turns into the giant fungus that has eaten him, which leads to an unforgettable climax where he covers the walls of St Paul’s Cathedral.