Humans are visual animals. Just as a dog, suddenly aware of the unexpected, turns his nose toward it and starts sniffing, we humans turn our eyes toward things to try to figure them out. Of course, many things are invisible because of distance, size, lack of light, or obstruction. Much of the history of technology has been about overcoming these problems, with telescopes, microscopes, infrared sensors, radar, television, etc. Once we can see something clearly, we can usually figure it out.
But some things are just inherently not visible. Epidemics, for instance. So we humans, clever creatures that we are, have devised ways to make even them visible. When cholera broke out in London in 1854, no one had a clue as to why or how the disease was spreading. A physician named John Snow stuck a pin in a map of London to indicate the residence of everyone who had developed cholera. It was quickly evident that the cases were clustered tightly around a particular public well from which people were drawing water for household use. Close the well, said Snow, and the epidemic will end. Snow, widely considered the father of epidemiology, was right, and the epidemic quickly abated when authorities closed the well.
Statistics, too, are a way of making the inherently invisible visible because they can be converted into graphs and charts. Add the power of computers and you can produce charts that border on the magical. Consider this one published in Business Insider. It charts the fertility rate (the number of babies born per woman) against life expectancy over the past 50 years for a large number of countries. Each country is represented by a circle, its size a function of that country’s population.
The first thing you notice is that the fertility rate has been dropping sharply in most countries, while life expectancy has been rising equally sharply. The circles migrate toward the lower right of the chart over time to show this. But one of the large circles suddenly drops off a cliff beginning about 1970 as its fertility rate drops precipitously. How come? Click on the bubble and its name comes up: China and its one-child-per-family policy. And some countries suddenly reverse course, and their life expectancy collapses, moving their circles rapidly back toward the left of the chart. What is causing that? Click on the circles and the names of the countries come up: Rwanda, Cambodia, etc.
In other words, this chart makes history itself visible. Is that cool, or what?