# Category Archives: featured

## The short arm of coincidence

James Tanton tosses off number theory problems the way John D. Rockefeller handed out dimes. I wrote about one of Tanton’s problems back in January. Then a few weeks ago this tweet about factorials and squares snagged my attention, and … Continue reading

## Prime After Prime

Are the prime numbers sprinkled randomly along the number line, like windblown seeds?Of course not: Primality is not a matter of chance but a product of simple arithmetic. A number is prime if and only if no smaller positive integer … Continue reading

## Traffic Jams in Javascript

Building bigger roads can make traffic worse. The usual explanation for this counterintuitive and counterproductive outcome is that bigger roads attract bigger shopping malls, which in turn attract more cars. But that’s not the whole story. In the 1960s Dietrich … Continue reading

## Sunshine In = Earthshine Out

No computer simulations have ever had broader consequences for human life than the current generation of climate models. The models tell us that rising levels of atmospheric carbon dioxide and other greenhouse gases can trigger abrupt shifts in the planet’s … Continue reading

## Dancing with the Spheres

In my latest American Scientist column I’m packing spheres again. The goal this time is to maximize the number of contact points where spheres touch each other. For example, four spheres in a tetrahedral cluster have six contacts; this is … Continue reading