MadSci Network: Zoology

Re: Why is it that a common ant will not

Date: Sat Mar 3 09:24:24 2001
Posted By: Edward Peterson, Staff, Chemical Engineering, S&B Engineers and Constructors
Area of science: Zoology
ID: 983233624.Zo


You have discovered a very important reason for cleaning your microwave 
oven.  The energy in a microwave oven generaly does not kill the insects 
that are attracted by the food matter left behind.

Ants, roaches and other insects can tolerate cold, heat and radiation much 
better than life forms, such as people, dogs and mice.  However, if you 
put an ant in a microwave oven like a kernal of popcorn, the popcorn will 
explode and the ant will not.  The secret is in the way the energy of a 
microwave oven works.

Microwave energy is selective.  It heats those things best that have a lot 
of water or fat best.  The microwaves in your oven are also big.  They are 
about 2 inches long.  Therefore, physics tells us that objects that are 
the size (about 1 inch wide) and composition (mostly water and fat) of a 
chicken egg heat the best in a standard microwave oven. As objects get 
smaller, they tend to lose heat more easily.  A single kernal of popcorn 
is at the small end for microwave heating, but because it has a very hard 
outer coating and is about 10% water inside, the water will heat to very 
high pressure before the outside coating will break.  Popcorn is then 
created.  A normal ant weighs much less than a kernal of popcorn.  Also, 
the ants external coat, its exoskeleton, is very porous and cannot build 
up pressure.  Because of its size, the ant loses any heat it gains from 
microwave energy very easily.  Remember that the air in a microwave oven 
does not get hot, so an ant being heated by microwave energy can lose that 
heat energy to the air surrounding it.  Therefore, an ant might heat up to 
about 90 degrees Fahrenheit in a microwave oven if the air temperature is 
about80 degrees Fahrenheit (I have not verified this), while food is 
boiling or burning on a plate.  Therefore, because an ant is small and the 
air is cool, the ant survives the energy it absorbs by getting rid of it 

Note that the same thing will not occur in aregular heat oven.  The ant is 
then heated by the hot air around it rather than by the energy that 
converts to heat inside its body.  Very quickly, it will absorb the 
external heat and reach the oven temperature.  In this case, being small 
and being able to absorb the heat so quickly works against it.

Dr. Ed Peterson

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