Re: Centrifuge in "World Book"

[John Clement <clement@HAL-PC.ORG>]

The definition of heavy also refers to the mass.  I would submit that an
article on science should use consistent terminology, and "where possible"
use words which are easily understood.  Heavy is commonly used to denote
things of greater mass, while the usage of heavy to denote density is less
common.  In either case if it is an ambiguous word, then it should be
avoided.  I am reminded of the riddle which is heavier a pound of feathers
or a pound of lead.  The generally agreed upon answer is neither.  While
there may be some debate over the word heavy, there can be no debate over
the fact that solid particles do not always move to the bottom.  In water,
both pumice and styrofoam will move to the top, and mercury will sink.  I
will grant that in most normal uses of the centrifuge that the commonly
encountered solid particles go to the bottom.  However, I seem to recall
that some uses of the centrifuge capture DNA strands in a boundary layer
between fluids of different density.

World Book is used in both elementary, middle school, and even in HS.  It is
also used by many adults as well.  Families buy it for their children, and
then continue to use it long after the children have graduated from school.
This particular case is one where the use of the word heavy is reinforcing a
misconception, while the word density is introducing correct usage.  If one
buys into the idea that elementary school children will not notice any
difference, then the accuracy of elementary science texts is also a moot
point.  Elementary school children have all heard the word dense, so
introducing and using the word density should not be a problem.
Unfortunately, with the current lack of reading among children, the contents
of both the texts and the encyclopedias may be irrelevant!

John M. Clement
Houston, TX

> At 05:31 PM 5/20/01 -0500, John Clement wrote:
> > After perusing the article on centrifugal force in the Wold Book
> > Encyclopedia, I glanced at the centrifuge article.  It says it
> "causes the
> > heavier liquid or the solid particles to move to the bottom of the
> > container, leaving the lighter substances on the top."  Don't
> they have any
> > good scientists on their staff to proofread this stuff!
> >
> > One wonders how any student can learn science when this sort of
> nonsense is
> > published in both the texts and the encyclopedias.
>
>
> With heavy heart I must report that the encyclopedia passage is
> *not* wrong
> (barring nitpicks about the meaning of "top" and "bottom").
>
> In the M-W dictionary, look up "heavy".
>    http://www.m-w.com/cgi-bin/dictionary?va=heavy
>
> You will see that "high specific gravity" is definition 1b.
> Other dictionaries agree.
>
> Is the encyclopedia passage open to misinterpretation?  Perhaps.
> Is it outrageous nonsense?  Certainly not.
>
> Would the intended readership (young children) be better served
> by an unambiguous, technical, precise description?  Probably not.