Digital cameras don't turn on the flash at night, how can there be double images, and there is no such situation without turning on the flash during the day? What's going on here?

Insufficient exposure, due to the dark light at night, the shutter speed of digital cameras will decrease when they shoot night scenes without flashing, usually about half a second or even longer. When the shutter is opened, all the images will be recorded. Open the shutter for a long time, no matter whether the camera or shooting, there will be weak movement, the more obvious the movement, the more obvious the ghost. That's why there are ghosts.