I recently read Jon Mooallem’s book Serious Face (which I highly recommend), and one of his essays got me thinking about clouds. I’ve always loved looking at them and imagining that their shapes looked like something (“That one’s a bear.” “No, it’s a dog.”), but I haven’t been one of those folks who could look at the sky and tell what kind of cloud they were seeing, or what the different types meant.
So I decided to find out a little more.
Philosophers throughout history have considered clouds, of course. Chinese scholars developed their own understanding of weather, including the ideas of Feng-Shui (wind and water). Aristotle talked about nephology (the study of clouds), and even theorized that it was the heat from the sun that caused cold water from the earth to rise in vapor form.
It was the Jesuit philosopher René Descartes who described clouds most clearly in the 1600s. He said that clouds were most likely small water droplets or ice particles. He thought these droplets come together to form little groups and develop into clouds. When they become too heavy to float in the air, they fall as precipitation. Pretty remarkable for the pre-scientific age.
It was in 1802 that a young scientist named Luke Howard was the first to describe clouds in four separate groups: cirrus (from the Latin for hair), cumulus (from the Latin for heap), stratus (from the Latin for sheet), and nimbus, which was a combination of all the three other types.
It was his categorization of cloudforms that helped others to recognize that each type had specific properties. Two of them more likely led to rain showers (the nimbostratus and cumulonimbus), and like animals and plants, they could be understood in families and species.
This was a huge breakthrough in the scientific community — a categorical description of something that had previously only been considered to be as fluid as water. He wrote an essay called On the Modification of Clouds, and he became widely recognized as the world’s finest meteorologist and nephologist.
A Closer Look
That was pretty much our understanding of cloudforms until 1960. That’s when a Polish mathematician, Benoit Mandelbrot, got interested in apparently random patterns in nature. He worked in many fields, but is most noted for his work in fractal geometry — shapes that have an infinitely complicated boundary, which changes with increasing magnifications. Like clouds. Or, as it turns out, like lots of things in nature.
Mandelbrot noted that: ‘Clouds are not spheres, mountains are not cones, coastlines are not circles, and bark is not smooth, nor does lightning travel in a straight line,’ (Fractal Geometry of Nature, 1982). He said, “the overwhelming smoothness paradigm with which mathematical physics had attempted to describe Nature was radically flawed and incomplete. Fractals and pre-fractals once noticed were everywhere.”
The work that Mandelbrot did was mostly higher level math, with lots of equations. One of the coolest things about fractals (and Mandelbrot sets, in particular) is that when you graph them and color them for different levels of magnification, they are beautiful:
They also start to look an awful lot like many things that we find in nature.
It was this connection to nature that gave impetus to the idea that this new fractal geometry had real usefulness in describing the complexity that we see all around us. Fractals tell us that even though waves and bubbles and clouds look randomly put together, there is a real order behind it. The work that Mandelbrot did was an attempt to bring order to the chaos we see.
Clouds were a perfect example for Mandelbrot. He noted that their irregularity doesn’t change at different levels of magnification, or depend on how close you are to them. This is why it is hard to tell how far away a cloud is — it looks just as random from 500 feet as it does from 20 miles. There are lots of other items in nature that have the same property. Without some context, a coastline picture could be taken from a helicopter, and airplane, or a satellite, and it would still look like a randomly shaped coastline.
What Mandelbrot showed is that clouds are not “just random.” They are organized according to principles that don’t vary. His contributions are still at work in the scientists who are working on chaos theory, who are studying everything from cell organization to the stars.
I love the fact that all this complexity takes nothing away from the beauty of what we see when we look at the sky. Now I have even more to contemplate when I sit back and look up.
