Photo Finish

In February 1985, British birder David Hunt led a tour around India. One of the stops was Jim Corbett National Park, in Uttar Pradesh, which has a large tiger population. The park provides an armed guard to each group of visitors, and they’re required to stay on the trails. As his party explored the park, though, Hunt heard an unknown call and walked a short distance off the track. Minutes later there was a scream. When his friends rushed to help, they discovered his mauled body in a clearing nearby. His friend Bill Oddie wrote:

When David’s body was recovered, so was his camera. Later on, the slides were developed … The first one is a nice close-up of a Spotted Owlet sitting on a branch … Then he must have heard a noise behind him, or maybe just sensed that he was not alone. Keeping crouched, he turned and saw a tiger pacing to and fro at the edge of the clearing. The next slide is of the tiger. It is some way away, walking to the right. On the next picture it is walking to the left. In the next one, it is facing the camera. In the next, it has begun to move forward, still looking straight at the lens. The next is closer. Then closer. And closer still. The final picture is of a frame-filling shot of the tiger’s head, eyes blazing and teeth exposed in a snarl.

“If David had kept shooting on his motor-drive, the whole thing must have happened in barely ten seconds,” Oddie added. “Crouched behind a camera, looking through the viewfinder and especially when using a telephoto lens, you don’t realise how close your subject has got. Neither, at the time, do you care. All you are focusing on is the picture. Press cameramen in war situations call it ‘camera blindness.’ It has proved fatal before.”

(From Oddie’s Follow That Bird!, quoted in Stephen Moss’ A Bird in the Bush, 2004.)

June 19, 2018June 19, 2018 | Death · Technology

The Way of Things

“Pyramid of Capitalist System,” from a 1911 edition of Industrial Worker, a newspaper of the international labor union Industrial Workers of the World.

“The inherent vice of capitalism is the unequal sharing of blessings,” said Churchill. “The inherent virtue of socialism is the equal sharing of miseries.”

June 19, 2018June 18, 2018 | Society

Close Quarters

Paulo Guarini di Forli offered this puzzle in 1512. On this tiny 3 × 3 board, which is the smallest number of moves in which the white knights can exchange places with the black ones?

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Henry Dudeney presented this solution in his 1917 Amusements in Mathematics; it’s now known as the “method of buttons and strings.” No knight will ever visit the center square, so we can ignore that; regard each of the remaining squares as a button and connect it by a string to each square that’s a knight’s move away. That produces diagram B. Now if we untangle the strings we get diagram C, a unique cycle that any knight must follow in making its way around this board. The four knights must follow this cycle, and no two knights may ever occupy the same square. The white knights start on squares 1 and 3, the black on 6 and 8. So to exchange the white and black knights, we must advance all four knights four steps along the circle, either clockwise or counterclockwise. Since the four knights make four moves each, the task is done in 16 moves. That’s the minimum. (Somewhat paradoxically, if three white knights oppose three black ones in the starting position, the minimum number of moves drops to 8.)

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June 18, 2018 | Puzzles

Podcast Episode 205: The White Mouse

In 1928 Nancy Wake ran away from her Australian home and into an unlikely destiny: She became a dynamo in the French resistance, helping more than a thousand people to flee the Germans and then organizing partisans to fight them directly. In this week’s episode of the Futility Closet podcast we’ll tell the story of the White Mouse, one of the bravest heroes of World War II.

We’ll also marvel at mailmen and puzzle over an expensive homework assignment.

See full show notes …

June 18, 2018June 25, 2018 | History · Podcast

For What It’s Worth

In an effort to attract female worshippers and tourists, Taiwan’s Southwest Coast National Scenic Area erected the “High-Heel Wedding Church” in 2016 in Budai Township, Chiayi County. It’s 17 meters tall and contains about 320 pieces of blue-tinted glass; Guinness has certified it as the “world’s largest high-heel shoe-shaped structure.” The BBC reports:

The shoe was inspired by a local story. According to officials in the 1960s, a 24-year-old girl surnamed Wang from the impoverished region suffered from Blackfoot disease. Both of her legs had to be amputated, leading to the cancellation of her wedding. She remained unmarried and spent the rest of her life at a church. The high heel is intended to honour her memory.

The church will be used for weddings and pre-wedding photo shoots, not regular services. Pan Tsuei-ping, the administration’s recreation section manager, said, “In our planning, we want to make it a blissful, romantic avenue. … Every girl imagines how they will look like when they become the bride.” The building will contain “100 female-oriented features,” including “chairs for lovers, maple leaves, biscuits, and cakes,” all suited for romantic photographs.

But the project has also been criticized as sexist and patronizing. On the Chinese microblogging site Weibo, Jessie Chou wrote, “I wear flip flops anyway.”

June 17, 2018 | Oddities

The No-Three-in-Line Problem

In 1917 Henry Dudeney asked: What’s the maximum number of lattice points that can be placed on an n × n grid so that no three points are collinear?

The answer can’t be more than 2n, since if we place one point more than this, we’re forced to put three into the same row or column. (The 10 × 10 grid above contains 20 points.)

For a grid of each size up to 52 × 52, it’s possible to place 2n points without making a triple. For larger grids it’s conjectured that fewer than 2n points are possible, but today, more than a century after Dudeney posed the question, a final answer has yet to be found.

June 16, 2018 | Science & Math

The Double Day

Lyndon Johnson averaged only 3 to 4 hours of sleep a night and worked most of the rest; his wife once said, “Lyndon acts as if there is never going to be a tomorrow.” He arranged his time in a curious pattern:

Johnson began every day with a bedroom conference at 6:30 a.m., then worked straight through until 2:00 p.m., when he had lunch, relaxed, sometimes with a swim, and took a quick nap. By 4:00 p.m. he was ready to go again. ‘It’s like starting a new day,’ Johnson observed, and he would then proceed to work straight through to one or two in the morning. This Johnsonian ‘double day’ amazed the press and exhausted and frustrated his over-worked aides. His assistant Jack Valenti opined that Johnson had ‘extra glands’ that gave him energy that ordinary men did not possess: ‘He goes to bed late, rises early, and the words I have never heard him say are “I’m tired.”‘

He once called a congressman at 3 a.m. to discuss a piece of pending legislation. When Johnson asked, “Were you asleep?” the congressman thought quickly and said, “No, Mr. President, I was just lying here hoping you’d call.”

(From Larry F. Vrzalik and Michael Minor, From the President’s Pen, 1991.)

June 15, 2018June 15, 2018 | History

Side-Eye

jealousy glass

This is sneaky: Operagoers in the 18th century could spy on their neighbors using a “jealousy glass” — you’d appear to be watching the stage but a mirror would direct your view to the side, like a horizontal periscope. Marc Thomin, optician to the queen of France, wrote in 1749:

It is sufficient to turn this opening in the direction of whatever one wishes to observe and the curiosity is immediately satisfied. Its usefulness is confined to letting us see surreptitiously a person we seem not to be observing. This lorgnette may have been called a decorum glass because there is nothing more rude than to use an ordinary opera glass for looking at some one face to face.

Hanneke Grootenboer writes in Treasuring the Gaze, “Apparently, it was very convenient in allowing one to keep track of latecomers entering the opera without having to turn one’s head.”

(From J. William Rosenthal, From Spectacles and Other Vision Aids: A History and Guide to Collecting, 1996.)

June 15, 2018June 14, 2018 | Society · Technology

Lost Voices

In 2009 three historians engaged forensic lip reader Jessica Rees to analyze silent film shot at the Battle of the Somme in 1916.

Soldiers of the Essex Regiment washing at a pool shout “Hi Mum!” and “Hello Mum, it’s me.” A soldier with a wounded foot repeats, “Jesus, Jesus, Jesus, Jesus.” And another soldier tells the crew, “Stop filming, this is awful.”

“What struck me the most was the optimism of the soldiers and their bravery,” Rees said. “They all seemed very positive, full of team spirit and jocular. Yet, as I was stunned to learn, many of them did not even survive the day of filming. I came away feeling a bit humble.”

June 14, 2018June 14, 2018 | History

The Nimm0 Property

In the 17th century the French mathematician Bernard Frénicle de Bessy described all 880 possible order-4 magic squares — that is, all the ways in which the numbers 1 to 16 can be arranged in a 4 × 4 array so that the long diagonals and all the rows and columns have the same sum.

These squares share a curious property: If we subtract 1 from each cell, to get a square of the numbers 0-15, then each of the rows and columns has a nim sum of 0. A nim sum is a binary sum in which 1 + 1 is evaluated as 0 rather than “0, carry 1.” For example, here’s one of Frénicle’s squares:

$\displaystyle \begin{matrix} 0 & 5 & 10 & 15\\ 14 & 11 & 4 & 1\\ 13 & 8 & 7 & 2\\ 3 & 6 & 9 & 12 \end{matrix}$

Translating each of these numbers into binary we get

$\displaystyle \begin{bmatrix} 0000 & 0101 & 1010 & 1111\\ 1110 & 1011 & 0100 & 0001\\ 1101 & 1000 & 0111 & 0010\\ 0011 & 0110 & 1001 & 1100 \end{bmatrix}$

And the binary sums of the four rows, evaluated without carry, are

0000 + 0101 + 1010 + 1111 = 0000
1110 + 1011 + 0100 + 0001 = 0000
1101 + 1000 + 0111 + 0010 = 0000
0011 + 0110 + 1001 + 1100 = 0000

The same is true of the columns. (The diagonals won’t necessarily sum to zero, but they will equal one another. And note that the property described above won’t necessarily work in a “submagic” square in which the diagonals don’t add to the magic constant … but it does work in all 880 of Frénicle’s “true” 4 × 4 squares.)

(John Conway, Simon Norton, and Alex Ryba, “Frenicle’s 880 Magic Squares,” in Jennifer Beineke and Jason Rosenhouse, eds., The Mathematics of Various Entertaining Subjects, Vol. 2, 2017.)

June 14, 2018June 13, 2018 | Science & Math