```Will some physical scientist help me clarify the question
of whether microwave radiation COULD cause cancer?  Robert
L. Park, to whom I am grateful for much enlightenment on
many matters, tirelessly reiterates that the only known
way for electromagnetic radiation to cause cancer is by
breaking a bond in DNA, and this requires a photon of
much higher frequency than microwaves have.  This seems
to me to be relevant but incomplete, for reasons I will
give, but Park didn't reply to my query on the point
(probably misidentifying me as a microwave-alarmist), so
I'm looking for help from others.
What we must talk about is a high-amplitude wave
at a frequency too low to break organic bonds, by a factor
of a few million.  Right?  Park says it doesn't matter how
high the amplitude is: strengthening the microwave signal
is (in his metaphor) just increasing the number of rocks
you try to throw across the Potomac, this doesn't get any
of them across the river because EACH ROCK has too low an
energy.  I object that this isn't the whole story, because
a periodic wave is not exactly sinusoidal, the sine wave at
its fundamental frequency comes accompanied by harmonics at
multiples thereof.  In quantum terms, that means that the
electromagnetic signal consists of photons at the energy
belonging to the fundamental frequency, accompanied by a
cloud of photons at multiples of that energy.  Now (as I
have explained to many undergraduate classes) the higher
the harmonic the lower the amplitude: for the n-th
harmonic, the amplitude goes down like 1/n, meaning that
the power goes down like 1/n^2.  By the time n is around
a million, this factor is around a trillion.  But not zero.
(True, a very smooth wave has weaker higher harmonics.)
In order to be sure a very very strong microwave signal
could not break a chemical bond, I would have to know
quantitatively HOW strong.
Maybe somebody here will tell me the numbers on
this, I haven't looked them up.  It seems evident even
without having the numbers that putting a mobile phone to
my ear will not endanger me.  Thus I am as mystified as
Park by the new, more credible study pointing to some
correlation with cancer.  But it also seems to me that
further discussion of the matter ought to include the
little wrinkle of HIGHER HARMONICS.
Chandler
```