For example, if city A is twice as large as city B, does it have twice as many gas stations? It turns out that it has something like 1.77 times as many. Or, if mammal X is twice as large as mammal Y, does it need twice as many calories to live? It turns out that it needs something like 1.74 times as many. Why is this, and is it a coincidence that these numbers are so close? The answer seems to be that we have some ideas, but no definite answers. Perhaps we should think of a city as one big organism with each person living there as one “cell”?