Transcript:

This month, we celebrate the solstice. In the Northern hemisphere, we experience our longest days and
shortest nights. In the southern hemisphere, it's the winter solstice, with short days and long nights. For
farmers in the Andes Mountains of South America, it's the time to look at the stars and decide when to plant
their crops. I'm Jim Metzner and this is the Pulse of the Planet, presented by DuPont. For hundreds of years,
people in Peru and Bolivia have chosen a night around the June solstice to go up on a mountaintop and look at
the group of stars known as the Pleiades. Exactly what they're looking for varies from village to village.

"For most, it's whether the constellation simply looks brighter or dimmer, for some it's whether stars are more or
less off center. But the general idea seems to be pretty much the same through the region -- do we see this
clearly or do we not see it clearly?"

Mark Cane is a climatologist at Columbia University. He says that if the farmers cannot see the Pleiades clearly
on this chosen night in June, they'll predict low rainfall during the growing season and set a later date for
planting their potato crops.

"Now you might think that if the sky is dimmer, it's cloudier and it's gonna rain more and it should be a better
growing season, but you must keep in mind that the observation is made in June, the planting isn't going to
begin until the following October. The rain in June is not terribly important one way or another."

But it turns out that the visibility of the Pleiades is important in predicting rainfall later in the growing season.
What connects the two is El Nino. The global weather phenomenon that scientists only recently learned how to
predict has been forecast by South American farmers for centuries. Pulse of the Planet is presented by DuPont,
bringing you the miracles of science, with additional support provided by the National Science Foundation.