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From: js2j@mhuxt.UUCP (sonntag)
Newsgroups: net.puzzle
Subject: Re:  Does the hole expand when heated?
Message-ID: <1230@mhuxt.UUCP>
Date: Wed, 30-Oct-85 16:29:20 EST
Article-I.D.: mhuxt.1230
Posted: Wed Oct 30 16:29:20 1985
Date-Received: Sat, 2-Nov-85 01:29:17 EST
References: <1114@decwrl.UUCP>
Organization: AT&T Bell Laboratories, Murray Hill
Lines: 39

> Does the hole expand when the metal around the hole is heated?
> Try it for yourself!  Here's how...
> [This experiment is given in the 7th grade General Science book published
> by D.C. Heath, 1961.  I used it many times in my former junior high science
> teaching days to prove that metal expands when heated.]
>  
> You need 2 pieces of apparatus:
> 	1) loop of 1/4" thick metal, attached to a wooden handle so it can
> 	   be held in a flame without burning yourself.
> 	2) ball that just fits through the metal loop, attached to a wooden
> 	   handle so you can hold it easily.
>  
> Procedure:  Holding the loop by its handle, place the metal end in a flame
> 	for a minute or so (We used a gas burner, but even a fireplace will 
> 	do).  Then try to fit the ball apparatus through the loop.  You
> 	will find that the heated metal has expanded in all directions 
> 	(including inward into the space of the hole), making the hole smaller
>  	so that the ball no longer fits through the loop.  Once the loop cools 
> 	off, the ball will once again be able to fit through.

     This from someone who used to *teach* junior high science!
     Apparently it's been a long time since you tried this experiment.
     Try it again.
     Or use a Xerox machine which has scaling capabilities.  Draw a circle
on a piece of paper.  Have the Xerox machine scale it to 160% (or whatever
yours does easily).  Is the inside of the circle bigger?  Or did the line
expand, making the inside of the circle smaller?  
     Or consider a coin.  Think of an arbitrary circle on the surface of the 
coin.  Imaging heating the coin.  The circular piece inside the circle expands,
right?  If the (imaginary) hole in the torus-like piece outside the circle
got smaller, the coin would explode, wouldn't it?  Do coins do that when
heated?  No?  So the hole must expand too, right?  Right.
     If I ever have a kid to send through school, I guess I'll have to be
very wary of the quality of science teachers they get.  We've just seen
proof that some science 'teachers' are ignorant of the most basic concepts.
-- 
Jeff Sonntag
ihnp4!mhuxt!js2j
    "What would Captain Kirk say?"