Source: [[Reference Notes/Scale]] Max Kleiber was a physiologist who published a paper in an obscure Danish journal in 1932. He surveyed the metabolic rates of a range of animals from a dove weighing about 150 grams to a large steer weighing almost 1,000 kilograms. He found that metabolic rates scaled with the weight of the animal with a power law exponent of $3/4$. This means that metabolic rate increase by 3 orders of magnitude for every 4 orders of magnitude increase in mass. A cat that is 100 times heavier than a mouse will have a metabolic rate that is 32 times higher, which is an economy of scale. Since then, researchers have extended his analysis to incude the smallest of mammals, the shrew, to the largest, the blue whale, covering more than 8 orders of magnitude. The same scaling has been found to occur across all multicellular taxonomic groups, including fish, birds, insects, crustacea, and plants, and down to bacteria and other unicellular organisms, covering 27 orders of magnitude. This is one of the most persistent and universal scaling laws in the universe. This data is plotted logarithmically, because it would require a piece of paper 100km wide in order to distinguish the points along 8 orders of magnitude (from shrew to blue whale) using a normal linear scale