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A murmuration of starlings

Emergence and the unity of science.
Hester_Jeff
The starling seems an unexceptional bird, but gather thousands together into a murmuration (named for the sound of a multitude of rapidly beating wings) and they become the grandest show in the sky. A murmuration in flight looks a bit like an amoeba on steroids as it morphs through a never-ending sequence of complex shapes. (Type “murmuration” into a web browser and play a video. Now. Really!)

Why do starlings do what they do? Ancient Romans believed that starlings foretold the will of the gods. The word auspicious comes from the Latin auspicium, or “divination by observing the flight of birds.” In the 1930s, ornithologist Edmund Selous asserted that starlings are telepathic. Even today, biologist Rupert Sheldrake attributes starling behavior to his hypothetical “morphic resonances.”

The real answer is a lot cooler!

Some of computing’s most revolutionary and frankly fun contributions to science have come from an ability to answer seemingly straightforward questions like, “When you combine lots of simple things into a larger system, what happens?” The flocking behavior of starlings is a gorgeous example.

Individual starlings all obey the same few flight rules: Watch your seven nearest neighbors. Fly toward each other, but don’t crowd. If any of your neighbors turn, turn with them.

Simplicity itself, right? But now put a bunch of virtual starlings into a computer, each programmed to obey those same rules, turn the crank, and see what happens. There are no gods, telepathy, or morphic resonances at work in the computer simulation. Even so, the computer-simulated flock behaves exactly like the real thing!

In December 2017, the story came full circle when those mesmerizing flocks of virtual birds took wing — or rather propeller — back into the real sky. Artists Lonneke Gordijn and Ralph Nauta programmed 300 drones to obey starling flight rules, then turned them loose above Miami Beach, much to the wonderment of onlookers. Welcome to the burgeoning science of emergence.

ASYJH0718_36395293copy
A huge flock of starlings creates a wonderfully complex shape as it lifts into the sky in this image taken in 2013. Such shapes tell us a lot about how science works.
© Thomas Langlands | Dreamstime.com
By definition, an emergent property is one that is possessed by a system as a whole but not by the components from which the system is made. While computer simulations of emergence may be a fairly new thing, the idea of emergence has been crucial to science for a long time.

At one extreme, physics is a remarkably successful quest for a few fundamental rules describing how matter and energy behave. At the other extreme, physics encompasses a complex universe filled with stars, planets, galaxies, and much more. That’s quite a chasm, but we don’t have to jump. Near the first end, nuclear physics emerges from interactions among particles. Atomic physics emerges when nuclei and electrons interact. Chemistry emerges from complex electromagnetic interactions among atoms. On things go as step by step, emergence bridges the divide, unifying science into a coherent whole.

Full disclosure: Like most scientists, when I talk about emergence, I mean physics-is-fundamental-but-as-things-get-complex-it-can-really-surprise-you emergence. Philosophers often mean a very different woo-woo-like-morphic-field-pops-up-and-snarfs-the-controls-away emergence. Mischief managed!

You might guess that emergence would be uncommon, but actually it’s hard to avoid. From chemical reactions, to weather patterns, to the beating of your heart, emergence is ubiquitous in the world around us. (As you read this, somewhere an unanticipated emergent behavior is costing an engineer her sanity.) And when life emerges from the chemistry of molecules that encode and replicate information, things get really interesting. Inventing emergent properties is sort of evolution’s gig.

Starlings have one more flight rule: If you spot a predator, fly away! As a falcon dives, the first starlings to notice hightail it. Their neighbors quickly respond, then their neighbors’ neighbors respond, and so on. Before the falcon even arrives, birds throughout the murmuration are flying about in chaotic, unpredictable ways in response to a predator that only a few have even seen. Surrounded by prey but unable to single out an individual target, the fastest raptor on the planet usually goes home hungry.

It turns out that watching seven neighbors is a sweet spot where the strategy works best. So when the falcon comes to visit, any starlings tracking something other than seven neighbors make easier targets. The falcon is more than happy to remove the nonconformists from the gene pool. Thus did evolution happen upon and fine-tune the starlings’ successful emergent strategy.

It is hard to count the number of times throughout history when authorities have pointed to a gap in then-current knowledge about the natural world and proclaimed, “This is obviously beyond the reach of science!” Science seldom fails to answer such a challenge, and quite often it is emergence that fills the gap. To be honest, there aren’t an awful lot of gaps left in which to look.

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