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15 August 2007
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The Birds, the Bats, and the Humans

Every few months, it seems, I read an article about aerodynamic derring-do.  It used to be about the birds.  They are capable of astonishing feats of maneuvering.  Unlike helicopters, which "beat the air into submission" and fixed-wing aircraft, which typically require long runways to begin and end their flights, birds can take off almost instantly, turn in a tiny radius, and maneuver in most astonishing ways.  (You can read about these astonishing ways by putting "bird aerodynamic feats" into a search engine and find thousands of articles.)

More recently, research into bat's flight has revealed even more impressive maneuvering than that of which birds are capable.  For example, from a recent article:

Unlike birds or insects, whose wings are comparatively rigid, bats have wings with more than two dozen independent joints, much like a human hand. That allows them to manipulate the thin, flexible membrane that covers the wings in ways that can generate more lift or greatly reduce drag.

Surfaces of bat wings also curve more than a bird's -- providing greater lift for less energy -- while their extraordinary flexibility allows them to make a 180-degree turn in less than half their wingspan, a radius impossible for any bird or existing plane, according to the initial findings.

As I was reading this, I remembered an observation I made a number of years ago while a friend and I were swimming in a pool.  He was in maneuvering "flight" so to speak, and I was sort of bobbing.  As he moved about, I turned to keep him in view and to make conversation easier despite the usual appalling acoustics of swimming pools.  As I was turning, I realized I was turning, with, as it now appears, a bat's radius.  Here was an (alleged, of course,) human in a totally foreign element, with no contact with any fixed frame on which to exert torque, rotating at will and seemingly without effort.  Astonished, I looked at my limbs and noticed that they were making short, energetically economical movements.  My hands twisted, my arms moved, my legs slithered.  All without a single conscious thought of control, but rather with the desire to keep my eyes focused on my conversation partner.

I mention this with awe, not because I am capable of some mysterious feat, but rather, because everyone can do it, trivially, without thinking about it.  The most remarkable thing, in fact, is that nobody does think about it.  Any more than the bat, turning in half his body radius, stops to marvel at his two dozen independent joints.  How on earth did we learn to exert a torque on a viscous liquid?  Sure, when I was a kid I took swimming lessons.  But torque lessons?  I don't remember that!

Speaking of swimming...

Immersion Temperature

Q:  What happens when the human body is immersed in water?
A:  The telephone rings.

That's such an old joke that you might not realize why it was funny.  You see, back when I heard it first, the "telephone" was attached by "wires" to the "wall."  There was only one of them, and when it "rang" you had to get up to answer it.  If you were immersed in water at the time, you left a trail between the bath and the telephone about which you would undoubtedly receive complaints.  Your response "it's water" never seemed to ameliorate the complaints.  But that has nothing to do with this item, it's just an old stupid joke.  That you probably haven't heard recently, or maybe ever.  And may never again.

What also happens is that you perceive the water, usually as a phenomenon of changing temperature.  Almost inevitably, as you begin the immersion process, your skin (my favorite organ!) notices a change in temperature.  Usually it's a benign onea feeling of warmth when entering the bath, a chill to which you quickly acclimate when diving into a swimming pool.  But what if the body of water is at the precise temperature of your skin?

I say "precise" because, at least from personal experience, one almost always feels hot or cold at the moment of immersion.  But there seems to be a very narrow temperature range in which, if your skin is at a fairly uniform temperature as well, you don't feel any temperature change at all.  And when this happens, a new feeling takes over - weightlessness!  Unfortunately, it doesn't last more than a few seconds, but it is quite impressive when it does.  This has only happened to me a few times, which leads me to believe that a precise set of conditions is required, one that is typically met only accidentally.  And yet, I would think that the conditions could be determined experimentally and replicated without great difficulty.  And certainly a lot more inexpensively than flying in the Vomit Comet!


NP:  "Candy" - Iggy Pop (With the incredible ooohooohoooh of Kate Pierson)

2007
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