I've seen a lot of programs about Ghosts and they often get disproved, same regarding UFO'S...

notice that in the 1800's it was flying ships like objects with balloon like propulsion.

during the 30 it was Zeppelin type objects.

50's the comical saucer sightings....

and since the advent of special effects - irredescent and brightly coloured crafts.

the power of suggestion and effects of room conditions etc on the human mind!!!