Three girls dressed up in white, green, and blue dresses. They also wore shoes of these three colors. Only Ann wore a dress of the same color as her shoes. Neither Betty’s dress nor her shoes were white, and Carol’s shoes were green. What was the color of each girl’s dress?
Richard Jefferies’ 1885 novel After London is one of the first post-apocalypse stories, an adventure tale set in a future England after an unspecified catastrophe has destroyed civilization, cut off communication with the continent, and set the surviving human population back to a quasi-medieval existence among the overgrown ruins of the “ancients.” The nature of the disaster is never explained, but it must have been prodigious — the interior of the island is now filled with an immense freshwater lake, and the old capital is now choked under poisonous vapors; one old house collapses like salt at the hero’s touch.
The first section, called “The Relapse Into Barbarism,” reads like a nonfiction natural history, describing in detail how nature reclaims the ruins in the decades after the conflagration. The longer second section, “Wild England,” recounts the adventures of the young nobleman Felix Aquila as he leaves the stultifying court life in which he has been raised and rows out onto the lake in a homemade canoe.
Why invent such a richly detailed future when the story is essentially a medieval romance? Why withhold the nature of the disaster? Felix’s adventures in this world seem to unfold as if unplanned, as if Jefferies invented it simply to explore it, to commune with his own creative faculty. He doesn’t seem to know what he’ll find in his own imagination.
The full text is available at Project Gutenberg and on Google Books, and there’s a free audio version at Librivox.
In 1784, in the margin of a math notebook, English schoolboy Richard Beale drew a chicken wearing trousers.
The Museum of English Rural Life tweeted the find after acquiring 41 Beale family diaries in 2016. Program manager Adam Koszary told the Guardian, “When you see a 13-year-old from the 18th century doing the kind of doodles that kids are doing today, it is so relatable — there’s an instant connection. Also, there’s the fact it’s just so stupid.”
A (probably!) unrelated chicken in trousers. Homework doodles from 13th-century Russia.
Four people are traveling in the dark when they arrive at a river. The narrow bridge can accommodate only two people at a time, and the group has only one torch, which must accompany each party that makes a crossing. Persons A, B, C, and D can cross in 1, 2, 5, and 8 minutes, respectively, and any pair of travelers can move only at the pace of the slower person. The torch will go out in 15 minutes. Can they all get safely across?
The least knotted of all knots is a simple closed loop, the “unknot.” Certainly this is easy to spot on its own, but adding even a few twists can make it hard to recognize:
An elaborately draped loop can be quite difficult to distinguish from a knottier knot. Is this an unknot?
(Yes, it is.)
Surprisingly, while research is ongoing, it remains unknown whether the challenge of recognizing unknots is efficiently solvable — whether an algorithm can accomplish the task in polynomial time. It’s an open question.
In the 18th century Leonhard Euler famously addressed the question whether it was possible to walk through the city of Königsberg and return to one’s home having crossed each of seven bridges exactly once.
The answer, briefly, was no, but in 2013 network scientist Thilo Gross noticed that the city of Bristol has a similar layout, and here the task is possible: If you’re willing to walk 30 miles, you can cross each of the 45 bridges on this map and return to your starting point.
Rinaldo Carnielo’s sculpture Tenax Vitae stands in the Galleria Rinaldo Carnielo in Florence.
After meeting the sculptor in 1893, Helen Zimmern observed that “for him, the shadow of death pervades all existence,” but “he cares not one jot whether his statues find purchasers so long as he himself is satisfied with the results.”
A paradox by Columbia University logician Haim Gaifman:
line 1: The sentence on line 1 is not true.
line 2: The sentence on line 1 is not true.
line 3: The sentence on line 2 is not true.
line 4: The sentence on line 3 is not true.
line n + 1: The sentence on line n is not true.
All these sentence are equivalent, because each essentially restates its predecessor. Since the sentence on line 1 isn’t true, the sentence on line 3 isn’t true either. “[B]ut what I have just stated is not true, because it is the sentence on line 4 (or an obviously equivalent reformulation of it), and also this last statement of mine is not true, because it is the sentence on line 5, etc. None of these sentences can be successfully asserted, because none of them is true; but again I find myself slipping into nontruth: what I have just said is not true for it obviously includes the conjunction of these very same sentences; and also this last assertion is not true, and so on ad infinitum.”
(Haim Gaifman, “Pointers to Truth,” Journal of Philosophy 89:5 [May 1992], 223-261. See Yablo’s Paradox.)
In the middle of winter when fogs and rains most abound they have a great festival which they call Exmas and for fifty days they prepare for it in the fashion I shall describe. First of all, every citizen is obliged to send to each of his friends and relations a square piece of hard paper stamped with a picture, which in their speech is called an Exmas-card. But the pictures represent birds sitting on branches, or trees with a dark green prickly leaf, or else men in such garments as the Niatirbians believe that their ancestors wore two hundred years ago riding in coaches such as their ancestors used, or houses with snow on their roofs. And the Niatirbians are unwilling to say what these pictures have to do with the festival; guarding (as I suppose) some sacred mystery. And because all men must send these cards the marketplace is filled with the crowd of those buying them, so that there is great labour and weariness.
But having bought as many as they suppose to be sufficient, they return to their houses and find there the like cards which others have sent to them. And when they find cards from any to whom they also have sent cards, they throw them away and give thanks to the gods that this labour at least is over for another year. But when they find cards from any to whom they have not sent, then they beat their breasts and wail and utter curses against the sender; and, having sufficiently lamented their misfortune, they put on their boots again and go out into the fog and rain and buy a card for him also. And let this account suffice about Exmas-cards.
— C.S. Lewis, “Xmas and Christmas: A Lost Chapter From Herodotus,” Time and Tide, Dec. 4, 1955
