All Stories by Ivars Peterson
- Math
Computing on a Cellular Scale
The behavior of leaf pores resembles that of mathematical systems known as cellular automata.
- Math
Hunting e
Of the irrational, transcendental numbers, pi seems to get all the attention. Web sites and books celebrate its quirks and quandaries. Its digits have been computed to 1,241,100,000,000 decimal places. Lagging far behind in the celebrity sweepstakes is the number known as e. Carried to 20 decimal places, e is 2.71828 18284 59045 23536. Only […]
- Math
Turning a Snowball Inside Out
Turning a sphere inside out without allowing any sharp creases along the way is a tricky mathematical maneuver. Carving an intricate snow sculpture depicting a crucial step in this twisty transformation presents its own difficulties. This was the challenge facing a team led by mathematician Stan Wagon of Macalester College in St. Paul, Minn., last […]
- Math
Amicable Pairs, Divisors, and a New Record
The Pythagoreans of ancient Greece were fascinated by whole numbers. One particular interest involved what we now call amicable numbers. Amicable numbers come in pairs in which each number is the sum of the proper divisors of the other. The smallest such pair is 220 and 284. The number 220 is evenly divisible by 1, […]
- Math
Folding Paper in Half—Twelve Times
You can’t fold a sheet of paper in half more than seven or eight times, no matter how large the sheet or thin the paper may be. How often have you heard that statement? Perhaps you’ve even put this assertion to the test. And, indeed, it is difficult to get beyond about seven or eight […]
- Math
Global contest nets encryption standard
A data-scrambling scheme called Rijndael was selected to become the federal government's new formula for protecting sensitive, unclassified information.
- Math
Extreme Tides
If Earth had been somewhat larger, it’s possible that it would not have survived tides induced by its moon or even by an encounter with a passing asteroid. That’s one scenario suggested by a recent investigation of a venerable equation that serves as a model for planetary tidal effects. Tidal effects are caused by the […]
- Math
Splitting Terrorist Cells
How can you tell if enough members of a terrorist cell have been captured or killed so there’s a high probability that the cell can no longer carry out an attack? A mathematical model of terrorist organizations might provide some clues. The question is what sort of mathematical model would work best. In this hypothetical […]
- Math
Perfect Magic Cubes
A magic cube is a three-dimensional array of whole numbers, in which each row, column, and body diagonal (corner to corner, through the center) adds up to the same total. A perfect magic cube is one in which the diagonals of each vertical or horizontal slice through the cube also sum to the same value. […]
- Math
Sculpting with a Twist
There’s more than one way to slice a bagel. A bagel (or a doughnut) can serve as a physical model for a mathematical surface called a torus. You can slice it horizontally (or longitudinally) so that you end up with two halves, each containing a hole. That’s great for making sandwiches because the cut exposes […]
- Math
Tricky Crossings
Have you heard the one about an itinerant entertainer traveling with a wolf, a goat, and a basket of cabbages? E. Roell The showman comes to a river and finds a small boat that holds only himself and one passenger. For obvious reasons, he can’t leave the wolf alone with the goat, or the goat […]
- Math
Megaprime Champion
The catalog of humongous prime numbers has a new entry–the champion prime (220996011 – 1), which has 6,320,430 decimal digits. It’s the largest known prime number and the 40th Mersenne prime ever found. A prime is a whole number (other than 1) that is evenly divisible by only itself and 1. Written in the form […]
