Ghosts have become popular in the last decade or so. Paranormal investigation, or “ghost hunting,” shows chronicle the adventures of people armed with an assortment of sensory equipment, most of which is easily available online in case you want to start your own investigative team. Or you can apply for admission to one of the many teams already in existence. For those who want to dabble in exploring hauntings, but not jump into the life of a researcher, there are scores of haunted sites and ghost tours you can pay to visit. What has stirred up this interest in ghosts?