Explainer Zone on Instagram: "In one of his lectures, Professor Lewin set out to test his grandmother’s claim that a person lying down is longer (i.e., taller when measured) than when standing. He first calibrated his measuring apparatus using an aluminium bar, measuring it vertically as 149.9 cm and horizontally as 150.0 cm (with an uncertainty of about ±1 mm). He then asked a student volunteer to stand and measured his height at 183.2 cm (±0.1 cm). Next the student lay down and the professor m