Forget movies like “Ghostbusters” there is no way you can capture a ghost or bring a dead body of a ghost (because they are dead to begin with). The only way ghosts can be documented is with a cassette recorder to capture EVP & good videos of objects moving by themselves or apparitions. But since some scientists are skeptical what other proof do they need?
Well, they are looking for some kind of manifestations that can be observed with the human senses or with more advanced instrumentation that can be detected as an abnormal phenomena that is not caused by people. Floating objects or things flying through the air would definitely be good examples. Lights or shadows are possibilities. Sounds or interactive communication would be great examples. But in each case it would have to be substantiated that it was not caused by people trying to create tricks or just ordinary explanations like an old building breaking down or an animal.
The images could be made by other objects.
Science is based on experiments that can be repeated by different people and get the same results. For example, if I drop a ball in Florida, it will fall to the floor. If you drop a ball where you live, it will also fall to the floor, as would a ball dropped by almost anyone, almost anywhere.
Parapsychologists study ghosts as part of their living. A parapsychologist seeks to understand paranormal phenomena. Paranormal phenomena is described as any phenomenon or occurrence that exceeds the bounds of what is possible, according to the established principles and laws of science.
None. If ghosts are real they are in the realm of the supernatural, and therefore outside the realm of science. Science is the study of the natural universe in natural terms.