Do ghosts really exist? 5 possible scientific explanations for paranormal activity REVEALED

Whether we like to admit it or not, many of us have probably questioned if a bump in the night was actually a ghost at some point or another. And if you're really unlucky, you might even believe you've see a spirit in the flesh. But what exactly makes us feel like we are in the presence of something beyond the grave? Exploding head syndrome, sleep paralysis and even mould can be the source of a chill down your spine or the inkling that someone is watching. So, brace yourselves, as MailOnline explores five possible scientific explanations behind experiences of paranormal activity.