Paranormal events are purported phenomena described in popular culture, folk, and other non-scientific bodies of knowledge, whose existence within these contexts is described as beyond normal experience or scientific explanation. Proposals regarding the paranormal are different from scientific hypotheses or speculations extrapolated from scientific evidence because scientific ideas are grounded in empirical observations and experimental data gained through the scientific method. In contrast, those who argue for the existence of the paranormal explicitly do not base their arguments on empirical evidence but rather on anecdote, testimony, and suspicion. Notable paranormal beliefs include those that pertain to extrasensory perception (for example, telepathy), spiritualism and the pseudosciences of ghost hunting, cryptozoology, and ufology. The term 'paranormal' has existed in the English language since at least 1920. The word consists of two parts: para and normal. The definition implies that the scientific explanation of the world around us is 'normal' and anything that is above, beyond, or contrary to that is 'para'. On the classification of paranormal subjects, Terence Hines in his book Pseudoscience and the Paranormal (2003) wrote: In traditional ghostlore and fiction featuring ghosts, a ghost is a manifestation of the spirit or soul of a person. Alternative theories expand on that idea and include belief in the ghosts of deceased animals. Sometimes the term 'ghost' is used synonymously with any spirit or demon, however in popular usage the term typically refers to a deceased person's spirit. The belief in ghosts as souls of the departed is closely tied to the concept of animism, an ancient belief which attributed souls to everything in nature. As the 19th-century anthropologist George Frazer explained in his classic work, The Golden Bough (1890), souls were seen as the creature within that animated the body. Although the human soul was sometimes symbolically or literally depicted in ancient cultures as a bird or other animal, it was widely held that the soul was an exact reproduction of the body in every feature, even down to clothing the person wore. This is depicted in artwork from various ancient cultures, including such works as the ancient Egyptian Book of the Dead (ca. (1550 BCE), which shows deceased people in the afterlife appearing much as they did before death, including the style of dress. Although the evidence for ghosts is largely anecdotal, the belief in ghosts throughout history has remained widespread and persistent. The possibility of extraterrestrial life is not, by itself, a paranormal subject. Many scientists are actively engaged in the search for unicellular life within the solar system, carrying out studies on the surface of Mars and examining meteors that have fallen to Earth. Projects such as SETI are conducting an astronomical search for radio activity that would show evidence of intelligent life outside the solar system. Scientific theories of how life developed on Earth allow for the possibility that life developed on other planets as well. The paranormal aspect of extraterrestrial life centers largely around the belief in unidentified flying objects and the phenomena said to be associated with them.