Original sentence: "   A number of witnesses say they have observed circles being created, saying that it takes only a few seconds and the corn falls flat like a fan being opened.Because many circles occur in the Avebury area of southern England, near Neolithic sites such as earth barrows or mounds, white horses carved in the chalk hills, and stone circles, it has been hypothesised that crop circles are of paranormal origin.Other ideas on the formation of crop circles have included tornadoes, freak wind patterns, ball lightning, and plasma vortices, described as "small, local whirlwinds of ionized air.Other theories state that crop circles are created by extraterrestrials, either as a means of communication or as an effect of spacecraft engines' heat.Various alternative theories say that some crop circles are not created by humans
Edited sentence: Because many circles occur in the Avebury area of southern England, near ancient sites such as earth barrows or mounds, white horses carved in the chalk hills, and stone circles, it has been hypothesised that crop circles are of paranormal origin.Other ideas on the formation of crop circles have included tornadoes, freak wind patterns, ball lightning, and "plasma vortices".Some believe that crop circles are created by extraterrestrials, either as a means of communication or as an effect of spacecraft engines' heat.There are alternative theories that say some crop circles are in fact not created by humans.These plasma vortices are best described as “small, local whirlwinds of ionized air.”   A number of witnesses say they have observed circles being created, saying that it takes only a few seconds and the corn falls flat like a fan being opened