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Cliff and others who have responded to my thoughts...

    Yes, we can demonstrate the phenomena and give folks an
explanation (the air is too busy or the pressure is less because
it moves faster above than below the object...) but are we helping
them understand that this is really complex and this is the way we
talk about it, verses this is a scientific truth.  This is the thing I am
really wrestling with... teaching science as explanations that are
known things verses this is the way we talk about what we see
happening based on our current understanding...
     I agree with many of you who have commented that our job
is to create curiosity... but where is the boundary between telling
folks how we currently explain things (scientific phenomena) and
causing them to look at the world and say 'gee I wonder what is
going on there?'
     I sometimes try to make the analogy with learning to play a
musical instrument... when you are first learning you learn the
techniques and accept the length of notes as a fixed entity that
you are trying to reproduce... but at some point you become
proficient enough with technique and basic knowledge about
music that you transcend and forget about consciously thinking
about technique and really connect with the music... that is the
experience I really enjoy when I get that AHHA moment with
understanding something in science and what I would love to be
better at passing on to others.  At that point I move from knowing
to understanding.... which is why my company tag line is
"Now I Understand"

David

                  Dave Taylor
       AHHA Museum Services
           'Now I Understand'
        1560 NW Woodbine Way
             Seattle, WA 98177
               (206) 363-8126
      e-mail:   [log in to unmask]
   http://www.AHHA-MuseumServices.com

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~


> From: Clifford Wagner <[log in to unmask]>
> Reply-To: Informal Science Education Network <[log in to unmask]>
> Date: Fri, 3 Sep 2004 00:50:09 -0400
> To: <[log in to unmask]>
> Subject: Re: Bernouilli exhibits
>
> ISEN-ASTC-L is a service of the Association of Science-Technology Centers
> Incorporated, a worldwide network of science museums and related institutions.
> *****************************************************************************
>
> I have a favorite explaination that I came up with for the Bernoulli effect.
> Simple enough to get across to kids yet completely factual:  Ready?
>
> Air, so busy going in this direction can't push much in that direction (90
> degrees to the first direction).
>
> With the Einstein quote in mind-"Things should be as simple as possible-but
> no simpler!"  you might have to add that still air is actually pushing in
> all directions; that it has pressure, and that it can often push more than .
> (How to explain pressure?  Air at sea level is under about 14.1 pounds per
> square inch.  How to explain that?  Picture a one inch square on your hand.
> Now if you visuallize that one inch square as the column of air going from
> you hand straight up all the way out to space, that column of air weighs
> 14.1 pounds.  Because air is a fluid it pushes in all directions, not just
> down, but it is the weight of the air above that gives it the pressure.   Go
> up the mile higher to Denver and the air pressure is considerably less- less
> 5,280 feet x1"x1" of air than you have on top of you at sea level
> So the complete explaination for why the ball stays in the fast moving air
> column is that air busy moving up can't push as much sideways as the still
> air around it.  It is the pressure of the still air that holds the ball in
> place.
>
> My favorite bernoulli device is the upside down funnel with air coming out
> pointing straight down.  Put a ball inside the funnel and it stays up,
> defying both gravity and the air pushing down.  But with the explaination
> above, it is explainable.  The air has to escape between the sides of the
> ball and the inside of the funnel.  That air, so busy going past the ball,
> pushes less directly on the ball (yes, it exerts less pressure)  than the
> still air underneath the ball.  The still air holds the ball up.  If you do
> this device make a clear funnel so you can see the ball and the nothing else
> holding the ball up.  (heat and bend 3/8"plexi is how I did  a pretty
> indestructable version)
> We did at the Franklin Institute a whole series of devices on one Bernoulli
> table in our 1984 version of an Aviation exhibit.  It worked really well
> having the multiple examples all next to each other:  The upside down funnel
> (with compressed (Pressured! I never made made that connection clearly
> before! ) air) and four other devices all worked by manipulating vacuum
> cleaner hoses that were blowing out instead of in.  They were: a vertical
> plexi tube with a whiffle ball (without holes) inside the tube.  Blow the
> air across the top and the ball rises in the tube.  A cross section of an
> airplane wing with little balls inside little tubes all vertical, spaced
> evenly apart visible inside the wing.  Blow the air over the wing and just
> like the big tube and ball most of the little balls rise. We were looking
> for visitors to connect between the two and I think many did.   We also had
> a clear 8inch square house with a thin plastic slanted roof taped to the
> rest of the house with scotch tape on one edge.  Blow the air over the roof
> and -voila!  the roof lifts off.  Put a weather channel video there next to
> it and you've got visitors inspired to act mighty powerfully on the model,
> while thinking through Bernoulli lifts roofs!   We also had the hanging on
> 3' long pivoting rods bowling balls that would come together when you blew
> air between them as was mentioned before.   Having all of these together
> helped get the idea across.
>
> Bill Booth was the project leader for this Aviation exhibit.  I think it was
> his idea to have tham all together.
>  There was one other great device in the exhibit that I haven't seen
> elsewhere that really should be done again.  Titled "Air can do work" or
> "Air Does Work"  it was two 4" diameter graphite pistons in precision glass
> tubing, each glass tube about a foot long.  They were connected to each
> other to form a U shape on the table with bent 4" glass tubing forming the
> curved parts, so you could see that the only connection between them was the
> air inside the tubing.   Each piston had a handle sticking out so you could
> push and pull them.  There was a vacuum/pressure guage connected to the
> airspace between the pistons.   Push one piston in and the other would push
> out with almost the same amount of force.  Two visitors would often "fight"
> each other, proving to them in their play that Air indeed can and does work.
> Push both in at the same time and you got a bit of pressure reading on the
> guage.  It was hard to get much pressure, even when pushing hard, again a
> personalized demo of air having force/resistance, and, without too much
> imagination necessary,  the ability to keep airplanes aloft.
> You could also pull both and get a bit of a vacuum.
> A classic device.
> It only lasted five years until someone broke one of the glass tubes (they
> had a wall thickness of 3/8" to 1/2")  and for some reason it was deemed too
> costly or hard or something to get replacement glass.  A mistake not to fix
> it in my book.  It's easy enough to design it so a plexi cover would keep
> the most determined urchin from having the ability to break the glass.   The
> graphite pistons were as good when the device died as they were when it was
> born, so without the breakage it's a reliable device.
>
> So much for simple Bernoulli explainations.
>
> A still constantly learning Clifford Wagner
>
> It
> -----Original Message-----
> From: Andrea Stark [mailto:[log in to unmask]]
> Sent: Monday, August 30, 2004 3:02 PM
> To: [log in to unmask]
> Subject: Bernouilli exhibits
>
>
> ISEN-ASTC-L is a service of the Association of Science-Technology
> Centers Incorporated, a worldwide network of science museums and related
> institutions.
> ************************************************************************
> *****
>
> We'd like to make changes to our Bernouilli exhibit, which now consists
> essentially of several small blowers that can be moved around to keep
> ping pong balls in the air and/or "make a basket" with them.  Does
> anyone have examples of more interesting exhibits that demonstrate
> Bernouilli's principle or otherwise deal with air flow and could capture
> the attention of older visitors, yet be operable by younger visitors to
> our children's museum?
>
> Andrea Stark
> Executive Director
> Maine Discovery Museum
> 74 Main St., Bangor, ME 04401
> 207-262-7200; FAX: 207-947-6281
>
> www.mainediscoverymuseum.org
>
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