(c) Anthony K. Grafton 2003

Weather from the Stars

For hundreds of years, South American Indians have used the stars to forecast the weather. In modern times, many people would doubt that the stars can tell us how much rain to expect, but scientists have recently discovered that, at least in one case, they can.

Some native people in Peru and Boliva have observed the constellation known as the Pleiades (pronounced plee-a-deez) during June (winter, in South America) to predict the amount of rain during the next growing season. If the stars in the Pleiades appear dim, and seem to be smaller and fewer in number, then a dry summer is predicted, and potato crops are planted later.

A couple of years ago, scientists discovered that this centuries-old method of predicting the weather may actually work. It turns out that when El Niño (weather activity associated with the Pacific ocean) is active, more moisture is present high in the atmosphere causing the stars in the Pleiades to be dimmer and appear smaller, and it makes some of the smaller stars hard to see at all. When El Niño is active, Peru and Boliva tend to get less rain in the summer. So looking at these stars can actually help predict the weather months in advance! How many stars can you count in this constellation?