Science & Math

A Lake Jaunt

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In 1972 Canadian scientists R.W. Sheldon and S.R. Kerr set out to reason out the number of monsters that occupy Loch Ness. Because the creatures are reportedly large and rarely seen, it follows that their numbers must be small. (“It has been suggested from time to time that as the monsters are never caught it must therefore follow that they do not exist. This is both irresponsible and illogical.”)

By estimating the fish stock available in the loch, they determined that the total mass of monsters is between 3,135 and 15,675 kg. Taking the minimum monster size as 100 kg (“anything smaller is not suitably monstrous”), they estimate that the loch contains between 1 and 156 monsters. The high end of this range seems unlikely; and since monsters have been reported for centuries they’re probably breeding, which would require a population of at least 10.

Given the available quantity of fish and assuming a stable population, monsters weighing 100 kg would have to die at a rate of at least 3 per year. Larger animals would die less frequently, and this seems likely since dead monsters are never found (and since the juveniles that must replace them are never seen). So it seems the lake probably contains a small number of large monsters, perhaps 10-20 monsters weighing up to 1,500 kg each and measuring about 8 meters, “a size that agrees well with observational data.”

“We would like to thank Kate Kranck for drawing our attention to this problem, because until she mentioned it we were unaware that monsters were a problem.”

(“The Population Density of Monsters in Loch Ness,” Limnology and Oceanography 17:5, 796–798)

Nontransitive Dice

Label the faces of a fair set of dice with these numbers:

Die A: 3, 3, 3, 3, 3, 6
Die B: 2, 2, 2, 5, 5, 5
Die C: 1, 4, 4, 4, 4, 4

This gives them a curious property. In the long run Die A will tend to beat Die B, Die B will tend to beat Die C, and Die C will tend to beat Die A. The three dice form a ring in which each die beats its successor. No matter which die our opponent chooses, we can select another that is likely to beat it.

Business magnate Warren Buffet once challenged Bill Gates to such a game using four nontransitive dice. “Buffett suggested that each of them choose one of the dice, then discard the other two,” wrote Janet Lowe in her 1998 book Bill Gates Speaks. “They would bet on who would roll the highest number most often. Buffett offered to let Gates pick his die first. This suggestion instantly aroused Gates’s curiosity. He asked to examine the dice.”

“It wasn’t immediately evident that because of the clever selection of numbers for the dice, they were nontransitive,” Gates said. “Assuming the dice were rerolled, each of the four dice could be beaten by one of the others.” He invited Buffett to choose first.

Special Projects

Facilities suggested by Lewis Carroll for a school of mathematics at Oxford, 1868:

  1. A very large room for calculating Greatest Common Measure. To this a small one might be attached for Least Common Multiple: this, however, might be dispensed with.
  2. A piece of open ground for keeping Roots and practising their extraction: it would be advisable to keep Square Roots by themselves, as their corners are apt to damage others.
  3. A room for reducing Fractions to their Lowest Terms. This should be provided with a cellar for keeping the Lowest Terms when found, which might also be available to the general body of Undergraduates, for the purpose of “keeping Terms.”
  4. A large room, which might be darkened, and fitted up with a magic lantern for the purpose of exhibiting Circulating Decimals in the act of circulation. This might also contain cupboards, fitted with glass-doors, for keeping the various Scales of Notation.
  5. A narrow strip of ground, railed off and carefully levelled, for investigating the properties of Asymptotes, and testing practically whether Parallel Lines meet or not: for this purpose it should reach, to use the expressive language of Euclid, “ever so far.”

He introduced this topic with an administrator by writing, “Dear Senior Censor,–In a desultory conversation on a point connected with the dinner at our high table, you incidentally remarked to me that lobster-sauce, ‘though a necessary adjunct to turbot, was not entirely wholesome.’ It is entirely unwholesome. I never ask for it without reluctance: I never take a second spoonful without a feeling of apprehension on the subject of possible nightmare. This naturally brings me to the subject of Mathematics …”

Round and Round

Since demolishing 78 traffic signals and installing 80 roundabouts, the northern Indiana city of Carmel has reduced the number of accidents by 40 percent and the number of accidents with injuries by 78 percent.

“It’s nearly impossible to have a head-on or T-bone collision when using the roadways, and collisions that do happen tend to occur at much lower speeds,” noted Governing magazine. “Other benefits of roundabouts include reduced fuel consumption, due to a lack of idling, and a construction cost that is at least $150,000 less than installing traffic lights.”

“We have more than any other city in the U.S.,” says mayor James Brainard. “It’s a trend now in the United States. There are more and more roundabouts being built every day because of the expense saved and, more importantly, the safety.”

Bear Facts

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The Veterinary Record of April 1, 1972, contained a curious article: “Some Observations on the Diseases of Brunus edwardii.” Veterinarian D.K. Blackmore and his colleagues examined 1,598 specimens of this species, which they said is “commonly kept in homes in the United Kingdom and other countries in Europe and North America.”

“Commonly-found syndromes included coagulation and clumping of stuffing, resulting in conditions similar to those described as bumble foot and ventral (rupture in the pig and cow respectively) alopecia, and ocular conditions which varied from mild squint to intermittent nystagmus and luxation of the eyeball. Micropthalmus and macropthalmus were frequently recorded in animals which had received unsuitable ocular prostheses.”

They found that diseases could be either traumatic or emotional. Acute traumatic conditions were characterized by loss of appendages, often the result of disputed ownership, and emotional disturbances seemed to be related to neglect. “Few adults (except perhaps the present authors) have any real affection for the species,” and as children mature, they tend to relegate these animals to an attic or cupboard, “where severe emotional disturbances develop.”

The authors urged their colleagues to take a greater interest in the clinical problems of the species. “It is hoped that this contribution will make the profession aware of its responsibilities, and it is suggested that veterinary students be given appropriate instruction and that postgraduate courses be established without delay.”

Stick Fight

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The Rod of Asclepius, left, with a single snake, is the symbol of medicine. Unfortunately, a large number of commercial American medical organizations instead use the caduceus, right, which has two snakes. Asclepius was the Greek god of healing, but the caduceus was wielded by Hermes and connotes commerce, negotiation, and trickery.

The confusion began when the American military began using the caduceus in the late 19th century, and it persists today. In a survey of 242 healthcare logos (reported in his 1992 book The Golden Wand of Medicine), Walter Friedlander found that 62 percent of professional associations used the rod of Asclepius, while 76 percent of commercial organizations used the caduceus.

“If it’s got wings on it, it’s not really the symbol of medicine,” the communications director of the Minnesota Medical Association told author Robert Taylor. “Some may find it hard to believe, but it’s true. It’s something like using the logo for the National Rifle Association when referring to the Audubon Society.”

Unconvinced

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In February 1962 John Glenn circled Earth three times on Friendship 7.

When he landed, he received a card from the International Flat Earth Research Society.

It said, “OK wise guy.”

Insight

In 1945, Oxford University’s Museum of the History of Science realized that 14 astrolabes were missing from its collection. Curator Robert T. Gunther had arranged for storage of the museum’s objects during the war, but both he and the janitor who had helped him had died in 1940. The missing instruments, the finest of the museum’s ancient and medieval astrolabes, were irreplaceable, the only examples of their kind. Where had Gunther hidden them?

The museum consulted the Oxford city police and Scotland Yard, who searched basements and storerooms throughout the city. The Times, the Daily Mail, and the Thames Gazette publicized the story. Inquiries were extended to local taxi drivers and 108 country houses. At Folly Bridge, Gunther’s house, walls were inspected, flagstones lifted, and wainscoting prised away. A medium and a sensitive were even consulted, to no avail. Finally the detective inspector in charge of the case reviewed the evidence and composed a psychological profile of Gunther, a man he had never met:

Clever professor type, a bit irascible, who didn’t get on too well with his colleagues. Single minded. Lived for the Museum. Hobby in Who’s Who ‘… founding a Museum’. Used to gloat over the exhibits and looked upon them as his own creation. Never allowed anyone else to handle them. Reticent, even secretive. Never told anyone what he what he was going to do. Didn’t trust them, perhaps. Not even his friends the Rumens, who would have offered their car to move the things. Had original ideas though. Safe from blast below street level. Germans would never bomb Oxford. Why, its total war damage was £100 and that from one of our own shells. How right he was. He never expected to die then. Believed he’d live to 90. Hadn’t made any plans; like most of us he thought he might get bumped off when the war started. That’s what he was telling his son in those letters. There was only one conclusion with a man like that anyhow: he’d never let the things out of his reach if he could have helped it. Didn’t even take the trouble to pack his own treasures away in Folly Bridge.

In 1948 the new curator found the missing instruments — they were right “within reach” in the museum’s basement. Gunther had disguised their crate with a label reading “Eighteenth-Century Sundials,” and it had evaded detection throughout the searches.

From A.E. Gunther, Early Science in Oxford, vol. XV, 1967, 303-309.

(Thanks, Diane.)

Art Appreciation

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If we stand immediately below a painting in a gallery, it appears foreshortened. But if we stand on the other side of the room, it appears small. Somewhere between these two points must be the optimum viewing position, where the painting fills the widest possible angle in our vision. How can we find it?

The German mathematician Regiomontanus posed this question in 1471. We can solve it using calculus, but it also yields to simple geometry: Draw a circle defined by the top and bottom of the painting and our eye level. That’s the point we want — any other point at eye level will define a larger circle, in which the picture makes a smaller chord and subtends a smaller angle.

(Thanks, David.)

Equal Opportunity

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The Pythagorean theorem works for any similar shapes, not just squares.

In the figure above, A + B = C.

If the three sides of a right triangle are made the diameters of three circles, then the combined area of the two smaller circles equals that of the largest. That’s also the area of the circumcircle, since a right triangle’s hypotenuse forms the diameter of its circumscribing circle.

Digit Count

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A letter from John Phillips of the Yale University School of Medicine to the New England Journal of Medicine, Feb. 14, 1991:

When referring to the hand, the names digitus pollicis, indicis, medius, annularis, and minimus specify the five fingers. In situations of clinical relevance the use of such names can preclude anatomical ambiguity. These time-tested terms have honored the fingers, but the toes have been labeled only by number, except of course the great toe, or hallux. Is it not time for the medical community to have the toes no longer stand up and merely be counted? I submit for consideration the following nomenclature to refer to the pedal digits: for the hallux, porcellus fori; for the second toe, p. domi; for the third toe, p. carnivorus; for the fourth toe, p. non voratus; and for the fifth toe, p. plorans domum.

Using porcellus as the diminutive form of porcus, or pig, one can translate the suggested terminology as follows: piglet at market, piglet at home, meat-eating piglet, piglet having not eaten, and piglet crying homeward, respectively.

(Thanks, Scott.)

Words and Numbers

alphamagic square 1

Spell out each number in this magic square and count its letters (25 -> TWENTY-FIVE -> 10), and you’ll produce another magic square:

alphamagic square 2

David Brooks points out that this works also in Pig Latin.

Lee Sallows extends the idea into geometry:

Casket Trouble

“If Socrates died, he died either when he was alive or when he was dead. He did not die when he was alive — for then the same man would have been both living and dead. Nor when he was dead; for then he would have been dead twice. Therefore Socrates did not die.”

– Sextus Empiricus, Against the Physicists

Going Down

In antiquity Aristotle had taught that a heavy weight falls faster than a light one. In 1638, without any experimentation, Galileo saw that this could not be true. What had he realized?

Click for Answer

Double Indemnity

This past February, brothers named Elwin and Yohan were arrested for six rapes in France, but both denied the charges. Deciding which is guilty is a tricky affair — they’re identical twins, so the genetic difference between them is very slight. Marseille police chief Emmanual Kiehl said, “It could take thousands of separate tests before we know which one of them may be guilty.”

This is only the latest in a series of legal conundrums involving identical twins and DNA evidence. During a jewel heist in Germany in January 2009, thieves left behind a drop of sweat on a latex glove. A crime database showed two hits — identical twins Hassan and Abbas O. (under German law their last name was withheld). Both brothers had criminal records for theft and fraud, but both were released. The court ruled, “From the evidence we have, we can deduce that at least one of the brothers took part in the crime, but it has not been possible to determine which one.”

Later that year, identical twins Sathis Raj and Sabarish Raj escaped hanging in Malaysia when a judge ruled it was impossible to determine which was guilty of drug smuggling. “Although one of them must be called to enter a defence, I can’t be calling the wrong twin to enter his defence,” the judge told the court. “I also can’t be sending the wrong person to the gallows.”

In 2003, a Missouri woman had sex with identical twins Raymon and Richard Miller within hours of one another. When she became pregnant, both men denied fathering the child. In Missouri a man can be named a legal father only if a paternity test shows a 98 percent or higher probability of a DNA match, but the Miller twins both showed a probability of more than 99.9 percent.

“With identical twins, even if you sequenced their whole genome you wouldn’t find difference,” forensic scientist Bob Gaensslen told ABC News at the time. More recent research shows that this isn’t the case, but teasing out the difference can be expensive — in the Marseilles case, police were told that such a test would cost £850,000.

It goes on. Last month British authorities were trying to decide how to prosecute a rape when DNA evidence identified both Mohammed and Aftab Asghar. “It is an unusual case,” said prosecutor Sandra Beck. “They are identical twins. The allegation is one of rape. There is further work due.”

Misc

  • Fathers can mother, but mothers can’t father.
  • The Mall of America is owned by Canadians.
  • Neil Armstrong was 17 when Orville Wright died.
  • LONELY TYLENOL is a palindrome.
  • 258402 + 437762 = 2584043776
  • “The mind is not a vessel to be filled, but a fire to be kindled.” — Plutarch

Edward Gorey’s pen names included Ogdred Weary, Raddory Gewe, Regera Dowdy, D. Awd­rey-Gore, E.G. Deadworry, Waredo Dyrge, Deary Rewdgo, Dewda Yorger, and Dogear Wryde. Writer Wim Tigges responded, “God reward ye!”

Thought Chemistry

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How many ideas hover dispersed in my head of which many a pair, if they should come together, could bring about the greatest of discoveries! But they lie as far apart as Goslar sulphur from East India saltpeter, and both from the dust in the charcoal piles on the Eichsfeld — which three together would make gunpowder. How long the ingredients of gunpowder existed before gunpowder did! There is no natural aqua regia. If, when thinking, we yield too freely to the natural combinations of the forms of understanding and of reason, then our concepts often stick so much to others that they can’t unite with those to which they really belong. If only there were something in that realm like a solution in chemistry, where the individual parts float about, lightly suspended, and thus can follow any current. But since this isn’t possible, we must deliberately bring things into contact with each other. We must experiment with ideas.

– G.C. Lichtenberg, Aphorisms

Almost Home

A drunk man arrives at his doorstep and tries to unlock his door. There are 10 keys on his key ring, one of which will fit the lock. Being drunk, he doesn’t approach the problem systematically; if a given key fails to work, he returns it to the ring and then draws again from all 10 possibilities. He tries this over and over until he gets the door open. Which try is most likely to open the door?

Surprisingly, the first try is most likely. The probability of choosing the right key on the first try is 1/10. Succeeding in exactly two trials requires being wrong on the first trial and right on the second, which is less likely: 9/10 × 1/10. And succeeding in exactly three trials is even less likely, for the same reason. The probability diminishes with each trial.

“In other words, it is most likely that he will get the right key at the very first attempt, even if he is drunk,” writes Mark Chang in Paradoxology of Scientific Inference. “What a surprise!”

A Losing Game

You and I each have a stack of coins. We agree to compare the coins atop our stacks and assign a reward according to the following rules:

  • If head-head appears, I win $9 from you.
  • If tail-tail appears, I win $1 from you.
  • If head-tail or tail-head appears, you win $5 from me.

After the first round each of us discards his top coin, revealing the next coin in the stack, and we evaluate this new outcome according to the same rules. And so on, working our way down through the stacks.

This seems fair. There are four possible outcomes, all equally likely, and the payouts appear to be weighted so that in the long run we’ll both break even. But in fact you can arrange your stack so as to win 80 cents per round on average, no matter what I do.

Let t represent the fraction of your coins that display heads. If my coins are all heads, then your gain is given by

GH = -9t + 5(1 – t) = -14t + 5.

If my coins are all tails, then your gain is

GT = +5t – 1(1 – t) = 6t – 1.

If we let GH = GT, we get t = 0.3, and you gain GH = GT = $0.80.

This result applies to an entire stack or to any intermediate segment, which means that it works even if my stack is a mix of heads and tails. If you arrange your stack so that 3/10 of the coins, randomly distributed in the stack, display heads, then in a long sequence of rounds you’ll win 80 cents per round, no matter how I arrange my own stack.

(From J.P. Marques de Sá, Chance: The Life of Games & the Game of Life, 2008.)

“On Professor Freud”

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The ignorant pronounce it Frood,
To cavil or applaud.
The well-informed pronounce it Froyd,
But I pronounce it Fraud.

– G.K. Chesterton

Higher Things

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In 1966 a Swedish encyclopedia publisher requested a photograph of Richard Feynman “beating a drum” to give “a human approach to a presentation of the difficult matter that theoretical physics represents.” Feynman responded:

Dear Sir,

The fact that I beat a drum has nothing to do with the fact that I do theoretical physics. Theoretical physics is a human endeavor, one of the higher developments of human beings, and the perpetual desire to prove that people who do it are human by showing that they do other things that a few other human beings do (like playing bongo drums) is insulting to me.

I am human enough to tell you to go to hell.

Yours,

RPF

Single Cases

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If we roll a fair die an infinite number of times, the outcome 4 occurs in 1/6 of the cases. In this light we can say that the probability of rolling a 4 with this die is 1/6. But suppose that, instead of repeating the experiment forever, we roll the die only once. Now it still seems natural to say that there’s a 1/6 chance of rolling a 4, but in fact either we’ll roll a 4 … or we won’t. Can it make sense to assign a probability to a single outcome? Charles Sanders Peirce writes:

If a man had to choose between drawing a card from a pack containing twenty-five red cards and a black one, or from a pack containing twenty-five black cards and a red one, and if the drawing of a red card were destined to transport him to eternal felicity, and that of a black one to consign him to everlasting woe, it would be folly to deny that he ought to prefer the pack containing the larger proportion of red cards, although, from the nature of the risk, it could not be repeated. It is not easy to reconcile this with our analysis of the conception of chance. But suppose he should choose the red pack, and should draw the wrong card, what consolation would he have? He might say that he had acted in accordance with reason, but that would only show that his reason was absolutely worthless. And if he should choose the right card, how could he regard it as anything but a happy accident? He could not say that if he had drawn from the other pack, he might have drawn the wrong one, because an hypothetical proposition such as, ‘if A, then B,’ means nothing with reference to a single case.

Peirce’s solution to this problem is curiously humanistic. Our inferences must extend to include the interests of all races in all epochs. A soldier storms a fort knowing that he may die but that his zeal, if carried through the regiment, will win the day. The man trying to draw a red card “cannot be logical so long as he is concerned only with his own fate” but “should care equally for what was to happen in all possible cases … and would draw from the pack with the most red cards.”

“He who would not sacrifice his own soul to save the whole world, is, as it seems to me, illogical in all his inferences, collectively.”

Pursuit of Truth

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Can animals reason without using language? Sextus Empiricus writes:

[Chrysippus] declares that the dog makes use of the fifth complex indemonstrable syllogism when, on arriving at a spot where three ways meet …, after smelling at the two roads by which the quarry did not pass, he rushes off at once by the third without stopping to smell. For, says the old writer, the dog implicitly reasons thus: ‘The animal went either by this road, or by that, or by the other: but it did not go by this or that, therefore he went the other way.’

So, perhaps. There’s a limit, though.

The Lakes of Wada

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Find a square island and establish a blue lake on it, bringing blue water within a certain distance of every point on the island’s remaining dry land. Then create a red lake, bringing red water even closer to every point on the remaining land, and a green lake bringing green water still closer.

If you continue this indefinitely, irrigating the island more and more aggressively from each lake in turn, you’ll reach the perplexing state where the three lakes have the same boundary. Japanese mathematician Kunizo Yoneyama offered this example in 1917.