By Benjamin Radford on January 24th, 2013 on livescience.com
The circles are mostly found in the United Kingdom, but have spread to dozens of countries around the world in past decades. But who — or what — is making them?
Early claims of crop circles
Some claim that the first crop circles (though they were not called that at the time) appeared near the small town of Tully, Australia. In 1966 a farmer said he saw a flying saucer rise up from a swampy area and fly away; when he went to investigate he saw a roughly circular area of debris and apparently flattened reeds and grass, which he assumed had been made by the alien spacecraft (but which police investigators said was likely caused by a natural phenomena such as a dust devil or waterspout). Referred in the press as "flying saucer nests," this story is more a UFO report than a crop circle report.
As in the 1678 mowing devil legend, the case for it being linked to crop circles is especially weak when we consider that the impression or formation was not made in a crop of any kind but instead in ordinary grass. A round impression in a lawn or grassy area is not necessarily mysterious (as anyone with a kiddie pool in the back yard knows). Indeed, mysterious circles have appeared in grass throughout the world that are sometimes attributed to fairies but instead caused by disease.
In fact the first real crop circles didn't appear until the 1970s, when simple circles began appearing in the English countryside. The number and complexity of the circles increased dramatically, reaching a peak in the 1980s and 1990s when increasingly elaborate circles were produced, including those illustrating complex mathematical equations such as fractals.
Theories & explanations
Crop circle enthusiasts have come up with many theories about what creates the patterns, ranging from the plausible to the absurd. One explanation in vogue in the early 1980s was that the mysterious circle patterns were accidentally produced by the especially vigorous sexual activity of horny hedgehogs. Some people have suggested that the circles are somehow created by incredibly localized and precise wind patterns, or by scientifically undetectable Earth energy fields and meridians called ley lines.
Many who favor an extraterrestrial explanation claim that aliens physically make the patterns themselves from spaceships; others suggest that they do it using invisible energy beams from space, saving them the trip down here. Still others believe that it is human, not extraterrestrial, thought and intelligence that is behind the patterns — not in the form of hoaxers but some sort of global psychic power that manifests itself in wheat and other crops.
While there are countless theories, the only known, proven cause of crop circles is humans. Their origin remained a mystery until September 1991, when two men confessed that they had created the patterns for decades as a prank to make people think UFOs had landed (they had been inspired by the 1966 Tully UFO report). They never claimed to have made all the circles — many were copycat pranks done by others — but their hoax launched the crop circle phenomena.
Most crop circle researchers admit that the vast majority of crop circles are created by hoaxers. But, they claim, there's a remaining tiny percentage that they can't explain. The real problem is that (despite unproven claims by a few researchers that stalks found inside "real" crop circles show unusual characteristics), there is no reliable scientific way to distinguish "real" crop circles from man-made ones. [Related: Crop-Circle Artists Becoming High Tech]
Crop circle features
No obvious human trace
Access to roads
There are many theories about what creates crop circles, from aliens to mysterious vortices to wind patterns, but they all lack one important element: good evidence. Perhaps one day a mysterious, unknown source will be discovered for crop circles, but until then perhaps they are best thought of as collective public art.