Analysis of Mechanical Traces Left Probably by Ball Lightning

A possible ball lightning (BL) incident, reported in a local TV as a thunderbolt which during heavy storm entered the room through one of windows and left it through the other, is analyzed. Precise reports, concerning the course of the incident and caused damages, were collected over the next few days in talks with seven eyewitnesses. To verify the reports, photographic documentation, pieces of the window panes, front-window meshes and other fragments of damaged objects were collected simultaneously on the scene. Reconstruction of the glass panes in the laboratory and analysis of Wallner lines existing on surfaces of radial cracks of the panes enabled to identify the direction of force causing the pane breakage. Since the forces turned out to be external for both windows, it excludes the reported movement of BL through the room. From the analysis of traces, the object which destroyed the window pane from the outside should have the following properties differing from those of an ordinary stone: it should be able to break the mesh mechanically on a small circular area, then becoming a larger and softer object be able to push the glass pane forcefully and violently. BL may be responsible for the damages if a solid-like non-hot BL core, capable to explode, is assumed. It is postulated that the BL core is composed of positively-charged crystalline nanoparticles of covalently-bonded nitrogen ions N+ and electron gas inside.