current issue web exclusives blog multimedia archive subscribe advertisers
Feature Articles
Editor's Note
Audubon View
Field Notes
Audubon In Action
Audubon Family
Earth Almanac
Green Guru
One Picture
Bookmark and Share

Green Guru
Advice for the eco-minded


What causes the northern lights?
—Allan Chisholm, Orono, ME

Painting the sky blue, green, and red, the northern lights, or aurora borealis, is a spectacular natural phenomenon often associated with cold nights in northern latitudes. The scientific explanation of the shimmering colors lies in the relationship between the sun and the earth.

The sun is so hot that it evaporates, releasing a stream of high-speed charged particles. This solar wind—made up of protons and electrons collectively called plasma—makes its way to earth. There it encounters a magnetic shield that extends from the poles and surrounds our planet. As the plasma clashes with oxygen atoms in earth’s atmosphere along the magnetic field lines, the electrons release energy, and the color green lights up the night. If the solar winds are strong enough, a chain of processes causes the electrons to penetrate deeper into the atmosphere, where they encounter nitrogen atoms and turn the sky purple and pink.

The strength of the aurora borealis depends on the sun. Generally the northern lights follow an 11-year solar cycle, says Dirk Lummerzheim, of the University of Alaska’s Geophysical Institute. “Halfway in between we will have a maximum of the solar activity,” he says. When that happens, a few times per solar cycle, people as far south as Florida and Texas sometimes see the northern lights. Look for them from September to April when it’s clear and dark.
Back to Top


Is there an easy way to stop the flow of unwanted catalogs?
—Abigail Andrews, Washington, DC

If a heap of catalogs slides out of your mailbox every day, you’re not alone. Retailers sent some 17 billion catalogs to American households last year, says April Smith, a managing director for Catalog Choice, a nonprofit that helps consumers manage mailings. Though these glossy publications are effective marketing tools, the paper they’re printed on depleted forests, and transporting them contributes to carbon emissions. Thankfully, it’s possible to stop the overflow.

Consumers can log on to the Direct Marketing Association’s website and request having their names removed from all direct-mail lists. For those who can’t live without one or two specific catalogs, Catalog Choice might be a better option. “Our mission is to provide a free and convenient way to reduce the number of unwanted catalogs in the mail,” says Smith. Just sign up for an account online and ask that any of the more than 1,000 participating retailers take your name off of their list or send you fewer catalogs. Catalog Choice is expanding this year to include credit-card offers and coupons., and also allow anyone buried beneath the glossy pages to slow the torrent of catalogs, but they charge up to $41 for the service.
Back to Top


Does eating local honey help prevent allergies?
—Wei Ja, Gainesville, GA

A spoonful of honey is often touted as the best natural medicine to combat the sneezing and itchy eyes brought on by pollen-filled blooms. After all, bees make honey from the nectar collected from plants close to their hives, so it stands to reason that eating the sweet stuff would prompt your body to build up a resistance to the cause of your discomfort. Alas, no scientific studies show that local honey combats allergies.

Still, future research may prove otherwise, says Peter Gallmann, head researcher at the Swiss Bee Research Centre. “There are hints in the literature that some relief can be due to the intake of pollen,” he says. “But pollen in honey is only in the range of parts per thousand. So it’s really not very much of an effect.” Until the honey connection is proven, be wary—some people have reported allergic reactions to the honey itself.

Even if local honey doesn’t clear your sinuses, it does offer benefits. It’s increasingly easy to buy, thanks to the growing trend of urban beekeeping, and purchasing honey from a farmers’ market means you’re supporting local agriculture and reducing emissions spewed from trucking the golden liquid.
Back to Top

Send your most vexing questions to