The number one question I get asked on investigations is: Why does it have to be night?
Honestly, it doesn't. I can walk into the warehouse during the day, set up a ghost box, and get responses. Quite a few times, Garry has done this during the day, and has gotten some great evidence from it (see the player below to listen to a few).
But why do most ghost investigations happen at night?
Well, for the most part, it's quieter at night. Especially where our building is, during the day, you have a lot of traffic from pedestrians in the area and car traffic, as we are a block and a half from the end of the I-16 freeway. If we brought people in there during the day, you would hear all sorts of outside noise that would spoil the investigation.
Also, orbs are better captured in the dark. The energy from your flash is a big part of what makes them manifest. During the day, you wouldn't need a flash to take pictures and the sun itself would cause a lot of light abnormalities in your photos due to glares and flares.
Furthermore, think of your senses. At night, it's dark (sorry to state the obvious), and your sense of sight is weakened, thus heightening your other senses, such as hearing and smell. This cues you in more to what is going on around you because you can't physically see it. It's amazing how the body reacts to this.
Some believe in a "Dead Time" or "Witching Hour" which is around 3am, when spirits are most active (supposedly), but we don't necessarily believe that is true. If the place you are visiting is haunted, you can probably talk to anyone who has ever lived there, worked there, etc., and they will all tell you that the time of day means very little.
Broad daylight or dead of night, something will happen when the spirits choose to have it happen.