Scientists say they're not certain what causes them. Have proposed several. For example, some scientists say that "microbursts" of wind created the circles. A microburst is a downward rush of cool air the same downward rush of air that sometimes causes an airplane to crash. Other scientists say that forces within the earth cause the circles to appear. But circles often appear in forms. It is hard to believe that any natural force could create those forms. Moreover, recently farmers have discovered not only circles but also other shapes such as triangles in their fields. Could any natural forces created a perfect triangle in a field of grain?
In the summer of 1990 some scientists spent three weeks in the scene of England where many circles have appeared. They had all the latest equipment of the time. This equipment worth 1.8 million dollars recorded nothing. But one night, as the scientists were watching a field, circles formed in the field behind them. These circles are shown in the photograph. The scientists had neither seen nor heard anything.