What they are
A crop circle is an area of standing cereal, usually wheat, barley or rapeseed, flattened in a pattern. The simplest is a single swirled disc a few meters across. The elaborate ones, which appeared from the late 1980s onward, run to hundreds of elements over several hundred meters, with fractals, knots, spirals and, in one 2008 case near Barbury Castle, the first ten digits of pi encoded in a ratchet of arcs. They appear overnight, mostly between May and August, mostly in southern England, and most densely in the chalk downland of Wiltshire around Avebury, Silbury Hill and the Vale of Pewsey. Reports from the 1970s through the 1990s run to several thousand worldwide, the great majority of them in England.
The claim
Believers hold that the formations are too large, too precise and too quick to be the work of people in the dark, and that the stalks are bent rather than broken in ways no plank could manage. Proposed makers include UFOs, earth energies, plasma vortices, a message-sending intelligence and, in the case of the meteorologist Terence Meaden, a natural whirlwind. The field acquired a name, cerealogy, a literature, and a tourist economy of helicopter flights, guided walks and tea rooms.
The history
Flattened circles in crops are old. In July 1880 John Rand Capron, a Surrey solicitor and amateur spectroscopist, wrote to the journal Nature describing a neighbor’s wheat field after a storm: patches beaten down into circular spots, each with a few standing stalks at the center and the fallen ones laid around it, which he attributed to cyclonic wind. The modern phenomenon, though, begins in the late 1970s in Hampshire and Wiltshire, with simple circles that drew press attention in the early 1980s and became a national story by the end of the decade, as the designs grew into pictograms. Researchers such as Pat Delgado and Colin Andrews published books declaring them beyond human capability.
On September 9, 1991, the tabloid Today announced that two men from Hampshire, Doug Bower and Dave Chorley, both in their sixties, had been making circles since 1978 as a joke that got out of hand. They had started after a pub conversation about the 1966 saucer nest found in a Queensland reed bed, and their equipment was a plank with a rope loop at each end, a length of string to mark the radius and a baseball cap with a wire sight to walk a straight line. They claimed hundreds of formations. To prove it they made one for the paper’s reporters; by the accounts of the day, Delgado, invited to inspect it, pronounced it genuine before being told who had made it.
The explanations
After Bower and Chorley, the question was not whether people could make circles but how good they could get. The answer was very. In 2002 the science writer Matt Ridley described in Scientific American making circles himself, and noted that every claimed test of genuineness, from bent nodes to magnetic particles to dowsing, had failed when the makers were known. In 2011 the physicist Richard Taylor, writing in Physics World, recalled watching three men confer over a sheet of paper in a pub car park near Avebury one night in July 1996 and finding, the next morning, a 194-circle triple Julia set 115 meters across in a field at Windmill Hill. He suggested that the best teams now use GPS, lasers and possibly portable microwave sources, and called the circle-makers the most science-oriented art movement in history. Teams of makers have since produced formations to order for advertisers and film companies.
Where it stands
No crop formation has ever been shown to require anything beyond people, tools and a summer night. A small residue of simple early circles may be wind or animal damage of the kind Capron described; none of them needs a spacecraft. The hoax origin story is on record, the methods are published, and the artists sign their work when it suits them. What the formations really are is a folk-art movement that found its audience by letting them believe. The verdict is mostly false: the fields are real, the patterns are real, and the mystery is manufactured.