Some of the crop circles reported around the world obviously were made by pranksters, a retired University of Wisconsin-River Falls agronomy professor said Wednesday at the Midwest Farm Show at the La Crosse Center.
But Lou Greub says aliens or another dimension seem to be the most likely explanation for others.
His presentation on crop circles will be repeated from noon to 12:30 p.m. today in the center's arena as part of the two-day farm show.
Greub acknowledged crop circles are a controversial topic.
"It's interesting," said Bob Redig, a rural Winona, Minn., farmer who listened to Greub's PowerPoint presentation. "I tend to believe it's done by people," he said, adding it would be easy for someone to use a rope to knock down plants and create a circle.
But Greub says he is curious and open-minded.
Greub became interested in crop circles when news media first reported their mysterious appearances in the English countryside in the late 1970s and early 1980s. They began as simple circles, but the designs have become increasingly complex over the years.
He visited crop circles for the first time in August, as part of a tour group in England led by Barbara Lamb, a long-time crop circle investigator and author from California. The tour group visited eight formations, which were anywhere from two weeks to 12 hours or less old.
Greub estimated 80 percent of reported crop circles are in England. English farmers who allow the public to see the circles usually have a collection box where people typically deposit the equivalent of about $3, he said. That helps offset the loss of the crop that was laid down in the circle and trampled by visitors. But some farmers detest the circles, prohibit visitors and quickly destroy the formations, Greub said.
"There are some fakes" among England's crop circles, he said. "There's one group, especially, that's kind of organized and they go out (creating crop circles) for the sport of it."
Crop circles in England usually are created at night, Greub said. Witnesses sometimes report seeing bright flashes of light or balls and columns of light in the fields where the formations are found the next day.
Greub said he knows of no government research into crop circles. The consensus among private researchers, he said, seems to be that crop circles have been made by someone or something that is trying to communicate something.
While he thinks aliens or another dimension of some kind are the two most likely causes, Greub doesn't rule out other possible explanations: "People talk about another dimension that's actually right here around us somewhere, and things can come out of it or go back into it and we really have no understanding of it."
Greub estimated 9,000 to 10,000 crop circles have been reported in the world since 1980. He knows of two reported in Wisconsin in the summer of 2004, one in an oat field near Tilden and the other in a barley field near Wausau.