Water vapour forms on top of the wing as an F-18 makes a tight turn. It may also be called ectoplasm by nutters. Ectoplasm is a term used in spiritualism to denote a substance or spiritual energy "exteriorized" by physical mediums. There is no scientific evidence that ectoplasm exists and many purported examples were exposed as hoaxes fashioned from cheesecloth, gauze or caused by other natural phenomena. Picture by Jenni.