Abstract
Ghosh and Hirsch [Phys. Rev. B 86, 054511 (2012)] claimed that many micrometer-size particles in liquid nitrogen, as large as 25 to 32 mu m, could be aggregated into balls by shaking. Ghosh and Hirsch performed their experiments with liquid nitrogen in open air; therefore, moisture condensed on the particle surface, leading to ball aggregation by shaking. This phenomenon has nothing to do with the electric field-induced formation of superconducting balls. In addition, their claim that a large electric field still exists in the interior of the capacitor when the electrodes are insulated is flawed. The electric field-induced superconducting ball formation reveals that the area of interaction between electric field and superconductors requires more investigation. However, the phenomenon can be explained within the BCS theory. DOI: 10.1103/PhysRevB.87.056503