There isn't any scientific method that I know of which could tell us if the orbs are spirits beginning to manifest or spiritual energy showing itself to us in the form of a sphere, unfortunately, so we have to leave it to educated guesses along with circumstantial evidence. Not ideal but until the metaphysical can be shown to exist - by way of seeing it, measuring it, examining it in a controlled enviroment and checking the effects of outside stimuli and thereby taking it from metaphysical to physical - we have no accepted method of postulating agreeable and acceptable theories which can be shown to give the same results time after time. One way of getting a theory which quite a few tend to find more acceptable is by asking a Medium for an explanation. I have never really heard a Medium explain in-depth about orbs, I have only heard them say that they are indeed linked to spiritual presences and that they are spheres of energy. Hence you will quite often hear people refer to orbs as spirit-energy.

What is very interesting is the appearance of orbs on infra-red or 'night-shot' video cameras as they are often called. In these cases, the orbs can be seen to dart about and make some very interesting mid-course changes at acute angles. They sometimes seem to appear from nowhere, zoom across the viewable screen and then fade away or just simply disappear from sight - most often the case with dark rooms and infra-red cameras that only allow for a reasonable increase in brightness of the surroundings. The most fascinating aspect of video-captured orbs is that in my mind, at least, they rule out dust particles as being the culprits since they move quickly and make course changes - sometimes around people - with noticeable variances in speed. In a room with no movement and no draughts, I find it hard to believe that we are witnessing just one dust particle that happens to be visible to the camera and happens to make striking velocity changes.