Crop circles – a phenomenon which began in the 1970s – were areas in fields where crops (usually cereal crops such as wheat and barley, but circles have been known to occur in oilseed rape, maize, linseed and grass) had been flattened in circular, geometric patterns.
These patterns would appear mysteriously, usually overnight, especially in the UK, but later in parts of the US, Japan, and a handful of other places.
The phenomenon had no known cause, baffling experts but providing plenty of work for producers of TV specials.
Despite conspiracy theorists being convinced that aliens were behind the phenomenon, the crop circle mystery was finally solved in 1987.
The tricksters who spent years making them in the 70s and 80s were revealed to be Dave Chorley, from Winchester in Hampshire, and his friend Doug Bower.
The pair travelled the countryside at night using a plank and a piece of rope to make the curious shapes, which appeared throughout Wiltshire and Hampshire.
The scientific consensus on crop circles is that they are constructed by human beings as hoaxes, advertising, or art. The most widely known method for a person or group to construct a crop formation is to tie one end of a rope to an anchor point and the other end to a board which is used to crush the plants.
Since the start of the 21st century, crop formations have increased in size and complexity, with some featuring as many as 2,000 different shapes and some incorporating complex mathematical and scientific characteristics.
Since becoming the focus of widespread media attention in the 1980s, crop circles have – perhaps inevitably – become the subject of speculation by various paranormal, ufological, and anomalistic investigators ranging from proposals that they were created by bizarre meteorological phenomena to messages from extraterrestrial beings.
There has also been speculation that crop circles have a relation to ley lines and many New Age groups incorporate crop circles into their belief systems.
Some paranormal advocates think that crop circles are caused by ball lighting and that the patterns are so complex that they have to be controlled by some entity. Some proposed entities are Gaia asking to stop global warming and human pollution, God, supernatural beings (for example Indian devas), the collective minds of humanity through a proposed “quantum field”, or extraterrestrial beings.