This curiosity was discovered by T.E. Lobeck. The square on the left is a conventional magic square — each row, column, and long diagonal totals 65. Replacing each number with the corresponding digit of pi (for example, replacing 17 with the 17th digit of pi, which is 2) yields the square on the right, in which the rows and columns yield equivalent sums.

Suppose [a] man who underwent [a] radical change of character — let us call him Charles — claimed, when he woke up, to remember witnessing certain events and doing certain actions which earlier he did not claim to remember, and that under questioning he could not remember witnessing other events and doing other actions which earlier he did remember. … [Suppose that] all the events he claims to have witnessed and all the actions he claims to have done point unanimously to the life-history of some one person in the past — for instance, Guy Fawkes. Not only do all Charles’ memory-claims that can be checked fit the pattern of Fawkes’ life as known to historians, but others that cannot be checked are plausible, provide explanations of unexplained facts, and so on. Are we to say that Charles is now Guy Fawkes, that Guy Fawkes has come to life again in Charles’ body, or some such thing?

— Bernard Williams, “Personal Identity and Individuation,” Proceedings of the Aristotelian Society, 1957

“If it is logically possible that Charles should undergo the changes described, then it is logically possible that some other man should simultaneously undergo the same changes: e.g., that both Charles and his brother Robert should be found in this condition. What should we say in that case? They cannot both be Guy Fawkes: if they were, Guy Fawkes would be in two places at once, which is absurd.”

5⁹ + 3⁹ + 4⁹ + 4⁹ + 9⁹ + 4⁹ + 8⁹ + 3⁹ + 6⁹ = 534494836

A perpetual-motion scheme by William Congreve. A, B, and C are three horizontal rollers fixed in a frame. They’re surrounded by a continuous band of sponge, a, and that’s surrounded by a chain of weights, b. Immerse the whole thing partially in a cistern. The sponge on the left will absorb water by capillary action, say from x to y; the sponge on the right will not (because the weights squeeze it out!). “The band will begin to move in the direction A B; and as it moves downwards, the accumulation of water will continue to rise, and thereby carry on a constant motion.”

From Henry Dircks, Perpetuum Mobile; or, Search for Self-Motive Power, 1861.

In 1921, chemists at Arthur D. Little Inc. reduced 100 pounds of sows’ ears to glue, converted it to gelatin, forced it into fine strands, and wove these into a purse “of the sort which ladies of great estate carried in medieval days — their gold coin in one end and their silver coin in the other.”

“We made this silk purse from a sow’s ear because we wanted to, because it might serve as an example to clients who come to us with their ambitions or their troubles, and also as a contribution to philosophy,” they reported. “Things that everybody thinks he knows only because he has learned the words that say it, are poisons to progress.”

The cheetah can reach speeds over 70 mph. In a dive, the peregrine falcon can reach 200 mph. But in 1927, entomologist Charles Townsend estimated that the deer botflies he’d observed in New Mexico surpassed both of these, reaching 400 yards per second. That’s 818 mph.

This claim stood for 11 years, until in 1938 chemist Irving Langmuir debunked it in Science:

• The power needed to maintain this speed amounts to 370 watts, or about half a horsepower. To deliver it, the fly would have to consume 1.5 times its own weight in food every second.
• Ballistics formulas show that the wind pressure on the fly’s head would amount to 8 pounds per square inch, probably enough to crush the fly.
• An 800 mph fly would strike the skin with a force of 310 pounds. “It is obvious that such a projectile would penetrate deeply into human flesh.”
• A supersonic fly would be invisible to the eye, not the “brownish blur” that Townsend had described.

Not to mention that an 800 mph fly would create its own sonic boom. After weighing the facts, Langmuir concluded, “The description given by Dr. Townsend of the appearance of the flies seems to correspond best with a speed in the neighborhood of 25 m/hr.”

When an explosion crippled Apollo 13’s command module, the crew used the lunar module as a “lifeboat.” The two modules had been built by different contractors, so when the mission was over Grumman sent a tongue-in-cheek bill to Rockwell for “towing” the ship to the moon and back:

The Associated Press reported that “North American Rockwell replied that the invoice had been examined by the company’s auditor, who pointed out that North American Rockwell had not yet received payment for ferrying LMs to the moon on previous missions.”

(Thanks, Perry.)