It’s an endlessly interesting shape, although not quite in the way generally believed.
Ancestors of today’s Chambered Nautilus, nautilus pompilius, have been propelling themselves through the depths of Earth’s oceans for 500 million years. They were there as the dinosaurs came, and went. Living hundreds of meters below the ocean surface, they’re mainly scavengers. No doubt they consumed some of the many dinosaur carcasses that drifted down after the asteroid impact…
The Nautilus shell appears often in Renaissance art, and was especially popular in the Victorian era when it became a symbol of scientific knowledge of the natural world. An abstract Nautilus-like spiral shows up in countless photography and art sites, suggested as a guide in composition (I have another post about that). While I’m not quite sure about the applicability of this principle to photography, the shell itself- especially when its numerous chambers are exposed in cross section – is a great photographic subject.
You’ll also see this gracefully expanding spiral as an example of the “golden ratio” or the closely related Fibonacci sequence. While it’s close to those numbers, it’s not an exact fit; in fact, the spiral is logarithmic, and here is a site that explains the difference very well. I’m not a math guy; it’s just a nice shape, showing how evolution creates elegant complexity in geometric ways. But nature is an engineer, not an artist; it’s not really the Golden Spiral that people find in paintings of the masters.
The exterior of a Nautilus shell is typically striped in dull browns. But it can be buffed and polished to reveal an iridescent layer beneath.
The many-chambered Nautilus shell has also become a metaphor for personal growth and aging. We make progress in life by creating a new ‘room’, moving into it, and closing off our past – without really cutting it loose. But what good are all those old rooms? The Nautilus uses them to regulate the depth at which it swims, by letting in water to adjust buoyancy. So, even with its 500 million years of ancestral history, it isn’t weighed down by its past – it makes use of it selectively, to stay afloat and maintain an even keel.