Physicist Robert Scherrer calculated two effects of primordial black hole passing through human body. He suggested that a black hole weighing about 1.4 × 10¹⁷ grams could generate lethal shock waves while smaller ones would pass through body unnoticed. Black holes weighing 7 × 10¹⁸ to 7 × 10¹⁹ grams could generate tidal forces that can tear the cells apart.