Our brain or a computer is essentially an electrically propelled machine. Electrical pulses may not need a body in the normal sense to create intelligence. Many religious references refer to creatures of light, light of the soul or the indwelling spirit of God. Some experts feel the orbs are from another dimension. They are physical objects but are not quite in our time and space.
Some witnesses claim to see the orbs form into alien beings or craft.
Photographs have shown first an orb or spot of light. The shots in sequence seem to show a craft growing in structure and detail. The final shots show a what appears to be a solid craft. When they return to their dimension they turn into orb like objects and depart. Theoretically, time may be only a second different from our own and we could not see the objects.