🚀 go-pugleaf

On Sat, 15 Apr 1995, Steve Luzader wrote:

>    By the way, a football makes a nice large-scale tippy top.  Lay it on its
> side, give it a good spin, and it will stand up on one end.  (Before Donald
> Simanek asks, I'm afraid I haven't made a study to see if the end it goes to
> depends on the initial direction of spin.  But I might check it out...)

When I was in high school, way back in the '50s, kids who had those class
rings with heavy rounded metal on one side, would spin them on a table top
and they'd rise and spin with the heavy side up. Much later, after I'd
told students about that other interesting toy, the 'rattleback' or 'celt'
and shown them the commercial version (sometimes called 'twizzler' or
'space pet') one student used a plastic spoon (from Wendy's), broke off
the handle, filled the spoon bowl with putty and put the handle across it
at a slight angle. It made a good rattleback. This student had taken my
advice and read Martin Gardner's column 'Mathematical Games' in the
Scientific American, where he discussed these toys. When walking with my
nephews and nieces along roads in Michigan, roads 'paved' with pebbles
which are well-rounded creek stones, we'd have fun spotting potential
stones with this behavior, fill our pockets and and then test them when we
got home. We got so we had a high percent reliability in choice.

Steve raises a good point, that the football, and the class ring, while
operating on the same principle as the tippy top, have one big difference.
They do not turn completely over! Therefore they never get a chance to
reverse their spin direction relative to their own axis.  Actually I
misled you in a recent post on this. The rotation never goes to zero about
the object's own axis. In the tippy top, the rotation axis changes
position with respect to the body of the object, until the *axis* moves
180 degrees and is coincident (but opposite to) the original direction. It
is these details which need to be observed before one can claim to have a
conceptual understanding of these objects. Obviously I have to work a bit
on my concepts, and my description. But never fear, once students have
sufficient math background (calculus) and understanding of the VECTOR math
of Torque = (Moment of Inertia)x(angular acceleration), and have a solid
grasp of gyroscopic motion it all makes sense. (As in Barger and Olssen.)
Another triumph for conceptual physics (?) ;-) (How *do* you make a
sarcastic smiley?) This is another example that a simple and inexpensive
demonstration can require far more than casual, informal, conceptual
physics for its understanding.

The better and more 'honest' conceptual physics books don't cover
tippy-tops and related devices, I'll bet. Their authors know better than
to try, for this can't be done satisfactorily with the very limited
concepts they use.

This relates to a long-standing concern of mine, the current fad for
'conceptual physics' courses. Don't get me wrong, we *must* develop
physics concepts if physics is to be understood. My reservations about
the 'so-called' conceptual courses is that some textbook authors and some
teachers give students the impression that all physics can be done, and
understood, with minimal mathematics. Some small parts of it can, and if
you strip away the tough parts, strip away the difficult mathematics, then
dummy down the rest, you can fool everybody into thinking it's possible.

But in the process you have done physics itself a disservice. You have
given students the false impression that physics concepts can be formed
without mathematics. Physics has struggled to understand the world from
earliest times, and if you look at this history you find that the most
important progress was made when we moved from informal, casual, vague
concepts, and put those concepts on a solid mathematical foundation. The
logic of mathematics is the cement, which holds everything in physics
together. Remove the math, and you have a largely ineffectual parody of
physics. To make a crude analogy, the result is as useful as removing the
entire skeleton from an invertebrate. You get something which doesn't
function very well.

And when we de-emphasize math in science teaching, we give aid and comfort
to those new-age crackpots with their clap-trap about 'holistic'
understanding of the universe, 'everything is relativistic' and carrying
the uncertainty principle far beyond its intended limits. Then there are
those 'paradigmwits' talking moonily about 'parardigm shifts', as if by
giving this age-old process a name they'd discovered something new. All of
these are reactions *against* the mathematical nature of physics, and seem
motivated by a desire to make science more emotionally appealing, indeed
to 'judge' science on its emotional appeal.

One of the few things we can do to counter this cultural movement is to
point out that compared to other ways of knowing, the methods of physics
*work*, giving us testable, reliable descriptions of the world.
Unfortunately when we do a demonstration, and find that it's understanding
requires knowledge beyond the course, and that the 'concepts' already
learned are impotent to deal with it, our goal is undermined. We can't
avoid this. There are many things easily observable in daily life which
are beyond the Physics I understanding. As many here have pointed out, to
'scare' students away with mathematics denies them exposure to any
physics. To expose them to a little physics in a non-mathematical context
gives them a taste of physics, but no realization of the *power* of
physics, and no feeling for how *physicists* think and work. It gives some
an 'illusion' of understanding, and a false confidence in incompleted
concepts. It misleads some into thinking physics *should* be less
mathematical, causing them to neglect further study of mathematics. It's a
dilemma with which we all must cope.

Fortunately, those who *really* have the 'stuff' to be good scientists,
will not be distracted by the deficiencies of their courses, but will
perservere on their own curiosity and motivation, to learn math and
science on their own, in their own way.

        -- Donald