Discover, February 1, 1993

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Without electricity we would perish. We could learn to do without the flow of electrons that power VCRs and food processors, but the currents inside our bodies are vital. The brain needs electricity to issue its commands from neuron to neuron. When these signals reach a muscle, they set up a wave of electrical excitation in the fibers, which in turn triggers the chemical reactions that make the fibers contract or relax. The most important muscle is the heart; it shudders under a wave of electricity about once each second.

Continue reading “The Body Electric” →

Discover, January 31, 1993

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Last April a bat-eared alien appeared on the television news. Its name was Blue Devil, and it was the first aye-aye–one of the rarest primates in the world–ever to be born in captivity.

The nocturnal Madagascar native was probably seen by more people than all the other aye-ayes in history combined. Aye-ayes are so hard to track that they have barely been studied, and conservationists are hard-pressed to estimate their total population. It’s just as well that aye-ayes are so elusive: on Madagascar they are often killed by their human neighbors, who consider the bushy-tailed mammals bad luck.

Continue reading “Four E’s and a P” →

Discover, January 31, 1993

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When paleontologists dissolve a chunk of limestone in acid, they often find hundreds or even thousands of cone-shaped, toothlike objects called conodonts (which is Greek for cone-shaped, toothlike object). In limestones that were laid down on the ocean floor between 515 million and 208 million years ago–that is, from the Late Cambrian through the Triassic periods–conodonts are all but ubiquitous. But what are they, and who did they belong to? Paleontologists have debated the question for well over a century, and at one time or another they have pinned conodonts on all manner of animals and plants.

Continue reading “In the Beginning Was the Tooth” →

Discover, January 31, 1993

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Mathematics is an ancient science. Yet even its simplest puzzles still mock us with their intractability. Take the problem of prime numbers. Primes are like elementary particles; they can’t be divided by any whole numbers except 1 and themselves. The numbers 2, 11, 19, and 10,957, for example, are all prime. Unfortunately, there’s no apparent pattern to the sequence of primes. Mathematicians have been trying to tease out a formula for finding a pattern since the days of Euclid, but to no avail. They’ve had to resort to making good guesses, then testing these prime candidates by trying to divide them into smaller numbers. If they can’t, a new prime joins the list.

Continue reading “A Broken Record” →

Discover, January 31, 1993

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Among mathematics’ more complex puzzles is one known as the traveling salesman problem. Imagine you’re an Avon lady about to visit a group of cities. Your cheapskate boss won’t pay for the gas, so you want to map the shortest possible route that hits all your destinations and brings you back to your starting point.

Using brute force on the traveling salesman problem gets you nowhere. Even a short, five-city tour offers five choices for a starting point, four choices for the second destination, three for the third, and so on. Considering all the possible combinations of cities (which you get by multiplying 5 x 4 x 3 x 2 x 1) leaves you with 120 routes to check. A little tedious, but doable.

Continue reading “And One for the Road” →