A curious puzzle from Pi Mu Epsilon Journal, Fall 1968 [Volume 4, Issue 9]:

Where must a man stand so as to hear simultaneously the report of a rifle and the impact of the bullet on the target?

Click for Answer


On the second day of Apollo 16’s trip to the moon in 1972, command module pilot Ken Mattingly lost his wedding ring. “It just floated off somewhere, and none of us could find it,” lunar module pilot Charlie Duke told Wired in 2016.

Mattingly looked for it intermittently over the ensuing week, with no luck. By the eighth day, Duke and Commander John Young had visited the moon and rejoined him, but there was still no sign of the ring.

But during a spacewalk the following day, Mattingly was just heading back toward the open hatch when Duke said, “Look at that!” The ring was floating just outside the hatch. “I grabbed it,” he said, “and we put it in the pocket. We had the chances of a gazillion to one.”

Duke said later, “You plan and plan and plan but the unexpected always jumps up and bites you.”

(From Ben Evans, Foothold in the Heavens: The Seventies, 2010.)

Three in One
Image: Wikimedia Commons

A stunning geometric alphamagic square by Lee Sallows. The 3 × 3 grid is a familiar magic square in which each number is spelled out: The first cell contains the number 25, the second 2, and so on. Interpreted in this way, each row, column, and long diagonal sums to 45.

But there’s more: The English name of the number in each cell has been arranged onto a distinctive tile, such that the three tiles in any row, column, or long diagonal can be combined to form the same 21-cell figure, as shown. (Shapes with dotted outlines have been turned over.)

And yet more: Count the number of letters in each of the number names (or, equivalently, count the number of cells that make up each tile). So, for example, TWENTY-FIVE has 10 letters, so replace the TWENTYFIVE tile with the number 10. Similarly, replace TWO with 3, EIGHTEEN with 8, and so on. This produces another magic square:

10  3  8
 5  7  9
 6 11  4

Each row, column, and long diagonal totals 21.

Image: Wikimedia Commons

I’m just sharing this because I think it’s pretty — it’s the smallest arrangement of identical non-crossing matchsticks that one can make on a tabletop in which each match-end touches three others.

Presented by German mathematician Heiko Harborth in 1986, it’s known as the Harborth graph.

Intangible Assets

A perplexing story from logician Raymond Smullyan:

Oh, one other thing. I must tell you of a certain great Sage in the East who was reputed to be the wisest man in the world. A philosopher heard about him and was anxious to meet him. It took him fifteen years to find him, but when he finally did, he asked him: ‘What is the best question that can be asked, and what is the best answer that can be given?’ The great Sage replied: ‘The best question that can be asked is the question you have asked, and the best answer that can be given is the answer I am now giving.’

It’s at the very end of his last book, A Mixed Bag, from 2016.


A normal die is painted so that it has four green faces and two red. Then it’s shaken in a cup and thrown repeatedly onto a table. You’re invited to guess which of these three sequences results. If you guess wrong you lose $10; and if you guess right you win $30.

  1. RGRRR

Most people express the preferences 2, 1, 3, in that order. Red is less likely than green, but it predominates in all three sequences, so many subjects explain that sequence 2 is more “balanced,” and therefore more probable. In fact 65 percent of all subjects (excluding expert statisticians and people whose business is probability) show a strong propensity to vote for sequence 2, even when it’s pointed out explicitly that sequence 1 is just sequence 2 minus the first throw — so sequence 2 cannot be more likely!

“The longer the sequence, the less probable it is, independently of its being ‘balanced’ or ‘unbalanced,'” writes Massimo Piattelli-Palmarini in Inevitable Illusions. “This shows how resistant certain cognitive illusions are. Many other more complex examples have been advanced, and these show that even professional statisticians are sometimes subject to the same illusion.”

Three Predictions

In Season 8, Episode 7 of Penn & Teller’s magic competition show Fool Us, magician Hans Petter Secker appears to predict the outcome of three successive rounds of rock-paper-scissors, though Secker oversees the game remotely from Norway and the players are invited to exchange items before each round. How is this accomplished?

Click for Answer

A Welcome Outcome

Just a charming little anecdote: When German chemist Adolf von Baeyer achieved a long-sought result, he tipped his hat to it:

Eventually, however, even Baeyer was supersaturated with these hydrogenations, and the sorely tried assistants hailed with deep relief the transference of his interest to succinylsuccinic ester and diketocyclohexane. By means of a dodge (‘Kunstgriff’) of which Baeyer was very proud (treatment with sodium amalgam in presence of sodium bicarbonate), the diketone was reduced to quinitol. At the first glimpse of the crystals of the new substance Baeyer ceremoniously raised his hat!

It must be explained here that the Master’s famous greenish-black hat plays the part of a perpetual epithet in Prof. Rupe’s narrative. As the celebrated sword-pommel to Paracelsus, so this romantic hard-hitter or ‘alte Melone’ to Baeyer: the former was said to contain the vital mercury of the mediaeval philosophers; the latter certainly enshrined one of the keenest chemical intellects of the modern world. … Baeyer’s head was normally covered. Only in moments of unusual excitement or elation did the Chef remove his hat: apart from such occasions his shiny pate remained in permanent eclipse.

(From his colleague John Read’s 1947 book Humour and Humanism in Chemistry.)

Second Strike

The Paradox of the Court is a logic problem from ancient Greece. Protogoras took on a pupil, Euathlus, on the understanding that Euathlus would pay him after he won his first court case. After Protogoras taught him the law, Euathlus decided not to practice, and Protogoras sued him for the amount owed.

Protagoras argued that if he won this lawsuit, he’d be paid the money he was owed, and if Euathlus won the suit, then he’d have won his first case and would owe Protagoras the money anyway under the terms of their contract. So he ought to be paid either way.

Euathlus argued that if he won the suit then by the court’s decision he owed nothing, and if he lost the suit then he still would not have won his first case, and thus owed Protagoras nothing under the contract.

One lawyer suggested that the court should decide in favor of the student and declare that he doesn’t have to pay for his education. Then Protagoras should sue him a second time — since then, incontrovertibly, the student will have won his first case!

Lodging a Complaint
Image: Wikimedia Commons

Among the most compelling anecdotes suggesting that dolphins have concepts of ‘wrong’ behavior is Thomas White’s description of how a human snorkeler observing Atlantic spotted dolphins off the Bahamas went outside the bounds of the norms of behavior expected by the dolphins of human observers at that site. The swimmer approached a calf engaged in learning to fish with its mother, a no-no in the rules of engagement between swimmers and these dolphins built up over years. When this happened, the mother then swam not to the hapless trespasser but to the leader of the group of swimmers, whom she could identify, and tail-slapped, her displeasure apparently directed at the leader who had not controlled the behavior of those being led.

— Hal Whitehead and Luke Rendell, The Cultural Lives of Whales and Dolphins, 2015