In the first of a series of videos, Kurzgesagt takes on a scientific subject that has always fascinated me: how the sizes of animals governs their interaction with the physical world, behavior, biology and appearance. The video starts with a great demonstration of the Square-cube law, because volume and therefore mass increase according to the law, if you double the length/height of a creature its mass increases by a factor of 8. So, if you drop a mouse, dog and elephant from a great height very different things will happen to each animal.

When humans get smaller, the world and its resources get bigger. We’d live in smaller houses, drive smaller cars that use less gas, eat less food, etc. It wouldn’t even take much to realize gains from a Honey, I Shrunk Humanity scheme: because of scaling laws, a height/weight proportional human maxing out at 3 feet tall would not use half the resources of a 6-foot human but would use somewhere between 1/4 and 1/8 of the resources, depending on whether the resource varied with volume or surface area. Six-inch-tall humans would potentially use 1728 times fewer resources.

There’s also a very interesting bit about how insects can breathe underwater due to some nifty interplay between water’s surface tension and the insect itself. A lot of it reminds me of a great article on The Biology of B-Movie Monsters, which you should most definitely read.

When the Incredible Shrinking Man stops shrinking, he is about an inch tall, down by a factor of about 70 in linear dimensions. Thus, the surface area of his body, through which he loses heat, has decreased by a factor of 70 x 70 or about 5,000 times, but the mass of his body, which generates the heat, has decreased by 70 x 70 x 70 or 350,000 times. He’s clearly going to have a hard time maintaining his body temperature (even though his clothes are now conveniently shrinking with him) unless his metabolic rate increases drastically.


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