Suppose L is the typical size (e.g., diameter) of the animal. Its surface area is proportional to L2, and its weight is proportional to L3.

We will use slightly different numbers from Haldane, rounding up the human-to-mouse size ratio to 20 for simplicity.

The person coming out of the bath has a film of water of thickness ∼ 1 mm. In the January 2023 column (“Shrub sphericity”), we estimated the surface area of a typical adult to be about 2 m2. Therefore, the volume of water on the human is ∼10−3 m3, and since the density of water is 103 kg/m3, its mass is ∼1 kg, so the mass (and hence weight) ratio of human to water is ∼80, negligible for her or him. For the mouse, its mass is (1/20)3 × 80 = 10−2 kg...

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