What could explain seeing a dim blue orb at night?

I’d start with the room and the window before trying to label the experience. Reflections from outdoor lights, passing vehicles, screens, or another light source can look like a floating shape in a dark room. If it happens again, note the time, weather, lights that are on, and where the glow appears. A phone not capturing it doesn’t settle the question either way. Cameras can miss dim or out-of-focus light.

There’s also the possibility that the glow was a visual effect rather than something in the room. Low light, tiredness, and the moments around falling asleep or waking can all affect what someone perceives. That doesn’t mean the experience was made up. It just means the memory alone may not tell you what caused it. If similar visual changes start happening often, especially while fully awake or alongside other symptoms, a clinician or eye-care professional could help check for ordinary causes.

I’d keep the explanation open instead of jumping straight to a spirit, an unusual being, or any one theory. The feeling of familiarity can be part of an intense experience, but it isn’t proof of what the object was. If the goal is to learn more, write down what was directly observed separately from what it seemed to mean. That gives you something clearer to compare if it happens again.