Loading ...
Sorry, an error occurred while loading the content.
 

bumble bee myth article

Expand Messages
  • Novella, Robert
    I have a preliminary draft of my article about the bumblebee myth below. It will soon be published in the New England Journal of Skepticism. If anyone has any
    Message 1 of 2 , Oct 15, 1999
      I have a preliminary draft of my article about the bumblebee myth below. It
      will soon be published in the New England Journal of Skepticism. If anyone
      has any comments or suggestions I would appreciate any input.

      Thank You
      Bob Novella




      The worst misconceptions are those, which everyone knows to be true,
      and yet are completely false. Once a false idea gets into the public
      consciousness, however, they are very difficult to expunge, and rarely go
      away completely. This is the second article in our new series that examines
      the most common myths and misconceptions in our society.

      When I was in High School we had school meetings every Friday during
      which we would discuss current events, see movies, listen to speakers etc.
      One morning we listened to an accomplished disabled man who started his
      speech by describing how science has proven that bumblebees cannot fly. He
      continued by saying that the bumblebee did not know this, however, and
      therefore is able to fly. His point was, of course, that disabled people
      could transcend the limitations and expectations society places on them by
      hard work and perseverance. I wholeheartedly agree with this attitude but
      the bumblebee example he used is not only erroneous, it illustrates one of
      the pervasive myths in our culture that are accepted without much scrutiny
      and rarely questioned.
      Often this bumblebee story is used to discredit scientific
      conclusions about the impossible nature of supernatural events or feats. For
      example, if someone claims to know a successful dowser and I describe that
      science and experiments repeatedly show this to be impossible, the advocate
      might say that his friend is like the bumblebee in that he doesn't know that
      science says his feats are impossible. Or he might say, "What does science
      know, science also tells us that bumblebees can't fly".
      This myth can lead the way to one of several different beliefs. One of these
      beliefs is that people can transcend their physical limitations and achieve
      the impossible regardless of what science tells us. The high school speaker
      mentioned above really seemed to believe this. Although he drew strength and
      inspiration from this it seems inevitable that unrealistic expectations
      would be created that can only lead to disappointment. Most importantly, one
      can derive from the bumble bee myth the pernicious belief that science is an
      unreliable and overrated enterprise After all bees obviously fly and
      anything that concludes otherwise is at best flawed and at worst a complete
      waste of time. One other possible interpretation of this myth could
      mistakenly support the belief that the power of the mind alone can overcome
      impossibilities, even if it's a bee's mind, I guess.
      Some light has been shed on the origin of the bumble bee myth by
      author and aerodynamicist J.H. Mcmasters. (Zetie, '96) He states that it
      all started in German technical universities in the 1930's. Apparently, a
      famous and unnamed Swiss aerodynamics expert was having dinner with a
      biologist when the latter asked a question regarding the flying abilities of
      bees. A preliminary calculation showed that there was insufficient lift to
      allow bees to fly. Only about one third to one half of the required lift
      could be generated. The biologist started spreading the word about
      scientific "proof" that bees can't fly and somehow the media got hold of the
      information. Today, decades later it is a ubiquitous myth that is rarely
      questioned and is often used to disparage science.
      The issue seems cut and dried. Either science has determined that
      bees can fly or it has not. What's the problem? The problem lies in the
      difference between insect flight and airplane flight. Conventional
      aerodynamics, the kind developed for airplanes and helicopters, focus on
      "steady state" situations. This refers to fixed wings or a rotating
      propeller. The motion of insect wings, in contrast, is very different,
      involving complicated 3D movements and rotations. Other differences were
      also ignored including the size of insects themselves. At the scale of bees
      the medium through which they fly (air) becomes more important for
      aerodynamics considerations. To bees, the air seems much more viscous than
      it does to us, almost like molasses. Aerodynamicists ignored all of these
      concerns primarily because it was not believed that insects could generate
      any exotic forms of lift. Charles Ellington, a zoologist from the University
      of Cambridge, has this to say: "Since the 1950s, we've been looking at
      insect flight with the wrong picture in mind." (Martin, 1997)
      Modern jet planes flying at 1500 miles per hour rely on similar
      principles of aerodynamics as the Wright brother's plane did at Kitty Hawk
      almost a century ago. The wings on both types of planes have a very special
      shape, called an airfoil, which is curved more on the top than the bottom.
      When an air stream meets the airfoil it splits into two separate air
      streams. Because the top air stream has a longer distance to travel (due to
      the curvature) it moves faster. Faster moving air exerts less pressure than
      slower moving air (by Bernoulli's principle) and this is a key component to
      lift. It is this pressure difference that produces the lift necessary to
      keep airplanes in the sky. (to be fair, there is some disagreement about the
      relative contribution of the airfoil to overall lift compared to other
      lifting forces like the downward flow of air off the wing) Think of sipping
      a soda using a straw. When you suck some of the air out of the straw you are
      lowering the air pressure in the straw which causes the higher pressure
      elsewhere to push the soda into your mouth.
      When science "proved" that insects can't fly the only thing it
      really proved was that insects with smooth and rigid wings could not glide.
      Experiments have actually been carried out demonstrating that this is indeed
      true. Clearly, conventional aerodynamics was not formulated to account for
      small insects with a small wing size. Once this was recognized, however,
      research began uncovering startling new aerodynamic oddities of insect
      flight that produce previously unknown sources of lift.
      One of the most significant discoveries involves the rotation of the
      wings during flight. Michael Dickinson of the University of California,
      discovered in his studies of flying insects that their brains were
      inordinately concerned with the minutiae of wing rotations. Hoping to reveal
      new insights into aerodynamic lift, Dickinson took a close look at wing
      rotations and noticed that it primarily occurred at the end of each wing
      stroke. To further analyze his findings he created a scaled up version of a
      fruit fly's wings. To simulate the viscosity of air from the fly's point of
      view Dickinson placed his robotic wings in mineral oil and flapped them
      slowly. Using sensors attached to his robotic wing he determined that by
      precisely timing the rotation of its wing, bees could generate 35% extra
      lift. What Dickinson and other scientists have discovered is that precise
      wing rotations at the end of a stroke causes the vortices of air on the
      wings to increase their speed thereby increasing lift.
      A similar discovery by Charles Ellington (mentioned above)
      attributes previously unknown sources of lift to a phenomenon called delayed
      stall. This occurs when a wing is at a high angle of attack (close to
      vertical) and the airstream detaches from the top of the wing forming a
      leading edge vortex. This vortex causes a low-pressure region on the wing
      temporarily increasing lift. Visualize a paper airplane near the end of its
      flight with the tail end dipping down and its nose pointing close to
      vertical. There is a brief moment of added lift just before it lands. This
      is delayed stall (Brookes, 1997) and it is normally a transitory phenomenon
      because it is so unstable.. Ellington, like Dickinson, also created a larger
      than life mechanical apparatus (this one called Flapper) to better visualize
      the phenomenon. His results astonished him. During each stroke of his
      over-sized robo-bug's wing, a leading edge vortex formed but instead of
      quickly dissipating, it traveled along the outer edge of the wing for most
      of the entire stroke of the wing. This was never noticed earlier primarily
      because the vortex is so tiny. It took something the size of Flapper to make
      it noticeable.
      It seems clear that science has not proven that bumblebees cannot
      fly. This myth began after attempting to use the equations of aerodynamics,
      which beautifully describe the flight of manmade objects, to describe the
      flight of nature's best aerialists, the insects. But when the differences
      between planes and bees are not accounted for it leaves one with the feeling
      that either science knows nothing or there something magical about insect
      flight. Neither is true.


      K.P. Zetie ; The Strange Case Of The Bumble Bee Which Flew. 1996. Winner of
      the Science in Print competition sponsored by the Institute of Phyics.
      http://www.iop.org/Physics/News/0012i.1

      Brookes, Martin. On a Wing and a Vortex, New Scientist, 11 October 1997
    • John Forester
      This goes to the full list because Robert did not list his own e-mail address. Sorry. My comment regards the following: It is this pressure difference that
      Message 2 of 2 , Oct 15, 1999
        This goes to the full list because Robert did not list his own e-mail
        address. Sorry.

        My comment regards the following: "It is this pressure difference that
        produces the lift necessary to keep airplanes in the sky. (to be fair,
        there is some disagreement about the
        relative contribution of the airfoil to overall lift compared to other
        lifting forces like the downward flow of air off the wing) "

        The downward flow of air off the wing is caused by the upward force on the
        wing; they are one and the same. Assume, just for discussion, a
        flat-bottomed airfoil (still used for beginner's model aircraft because
        they provide lift at slow speeds, although they have little speed range)
        with all the curvature on the top. The air curves over the upper surface of
        the wing, producing a pressure that is lower than ambient. This lifts the
        wing, pulls it up. It also, to exactly the same extent, pulls the air
        down. To every action there is an equal and opposite reaction. The result
        is that the air that leaves the trailing edge of the wing is moving
        downward (even if the lower air didn't move downward, as the upper air hits
        it at the trailing edge, the downward momentum of the upper air is added to
        that of the lower air, to produce downward motion of both streams, now
        rejoined. Of course, this can't happen unless the wing is moving through
        the air (or, as in this discussion, the air is described as moving past the
        wing, as in a wind tunnel). Impulse is force times time. The impulse must
        equal the weight of the aircraft (or it wouldn't stay up). Force equals
        mass times acceleration. Therefore, the greater the mass of air affected by
        the aircraft per second, the slower it has to move, so that with a faster
        aircraft the downward velocity of the air is less than with a slower
        aircraft of equal weight. Similarly, since a greater wingspan allows more
        air to be affected per second, with longer wings the downward velocity of
        the air behind the wing is less. As the aircraft flies along, all behind
        its wing is a downward movement of air, and at the wingtips that has to
        meet the unaffected air, so at each wingtip there is a spiral vortex
        trailing behind, each with its side nearest the plane going downward.



        John Forester
        7585 Church St., Lemon Grove CA 91945-2306
        619-644-5481 forester@...
      Your message has been successfully submitted and would be delivered to recipients shortly.