In this era of Photoshop, every day sees a batch of new, bizarre photos from online pranksters. But the photos in this list are not as easy to dismiss. Most of them are from a time before we could edit in a ghost with one click, and all of them have held up to professional scrutiny, time and time again. Experts still can’t explain what’s going on in these eerie images. Think you can solve the mystery? Read on.