P5 5 Investigating the feasibility of Dr. Stone’s sweat-lens

Abstract

In this paper we look at a scene in the popular anime Dr. Stone, where a convex lens made of sweat and glass is used to ignite a leather cloth with sunlight. We have assumed that the radius of the lens r = 2.5 cm, the Solar Intesity I_0 = 1366 W/m^-2 and the temperature that the leather ignites at is 300 °C on a sunny day. Our results show that rather than taking 60 seconds to ignite like it did in the show, this process in real life would take 154 seconds. This suggests that the scene in Dr. Stone is inaccurate.