The fellow across the aisle is a stranger to me, but I know we share a destination. He’s scanning the index of the meeting program, presumably looking for friends or colleagues delivering a paper. When I unfold myself from seat 22D and stroll toward the back of the plane, I spot a few more of […]

It’s time for my bimonthly self-promotional horn toot. The new issue of American Scientist is now available online, and paper copies should soon be stuffing mailboxes everywhere. My “Computing Science” column is on a new class of “holographic” algorithms invented a few years ago by Leslie G. Valiant of Harvard. The ideas have been further […]

Whenever Norm Abram tells me to “measure twice, cut once,” I wonder what I’m supposed to do if the two measurements disagree. Perhaps I should measure a third time, in hope of settling the question by majority rule; but then I might well wind up with three discrepant values.
Strolling by a construction site the […]

Don Elgee, a retired teacher of mathematics and computer science from Ottawa, sends the following inquiry:

In hockey, when a team is down by a goal with about one minute to go, the goalie is pulled in favor of another offensive player. This illustrates a key point in the strategy of most games.
The object is not […]

Saturday’s New York Times had a story by Sam Roberts about a newly released Census Bureau study of the frequency of surnames in the U.S. The Times story was mainly about the names at the top of the list, and especially the increasing prominence of Hispanic names (Garcia and Rodriguez have made it into the […]

Barry Cipra, my friend and former neighbor, and a frequent bit-player commentator, is the Talk of the Town this week. A story in The New Yorker by Lizzie Widdicombe highlights Barry’s work on the mathematics of the following calendrical problem.
Doing all arithmetic modulo 100, if you were born in the year X, you reach age […]

When is a tree (large, woody plant) not a tree (connected acyclic graph)?

This has something or other to do with the topic of the previous post.
(The tree (?) is a crepe myrtle near the campus of North Carolina State University in Raleigh.)

The drawing below, brazenly swiped from a 1964 Martin Gardner column, illustrates the solution to a well-known puzzle. If you stack n bricks on a table, how far can you make them extend over the edge without toppling?

The answer given, for bricks of unit length, is one-half the nth harmonic number, the sum of the […]

This morning I am enjoying the benefits of jet lead. My watch says it’s 7:30, but the hotel-room clock reads 4:30, so I have a few hours free to lie awake and solve the world’s problems. As a warmup exercise I’m doing mental arithmetic. I’m dividing integers, and trying to figure out how I do […]

From the Dorling Kindersley Eyewitness Travel Guide to the Pacific Northwest, page 218:
In spite of its name, False Creek is not a creek at all….