A surprising solution to the (in)famous "Cross the Network" puzzle

My father introduced me to the "Cross the Network" puzzle when I was a kid. Here it is, as described by Martin Gardner in one of his early Mathematical Recreations columns, which ran in Scientific American from the 1930s to the 1980s.

One of the oldest of topological puzzles, familiar to many a schoolboy, consists of drawing a continuous line across the closed network shown in Figure 51 so that the line crosses each of the 16 segments of the network only once. The curved line shown here does not solve the puzzle because it leaves one segment uncrossed. No "trick" solutions are allowed, such as passing the line through a vertex or along one of the segments.

It turns out there is a solution. Is it a "trick?" That's up for you to decide.

This puzzle, and many others, are in Gardner's Hexaflexagons and Other Mathematical Diversions: The First Scientific American Book of Puzzles and Games. Used copies available cheap! Read the rest

Free: scanned copy of Martin Gardner's Logic Machines and Diagrams (1958)

I love Martin Gardner's puzzle, math, magic, and philosophy books. I just learned from visiting Clifford Pickover's website about a Gardner book that's new to me: Logic Machines & Diagrams (1958).

From the introduction:

A logic machine is a device, electrical or mechanical, designed specifically for solving problems in formal logic. A logic diagram is a geometrical method for doing the same thing. The two fields are closely intertwined, and this book is the first attempt in any language to trace their curious, fascinating histories.

I think I need the hard copy.

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