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From: jqj@gvax.cs.cornell.edu (J Q Johnson)
Newsgroups: net.arch
Subject: Re: electrons as a bound on memory size (was VLMM, crypt)
Message-ID: <505@gvax.cs.cornell.edu>
Date: Tue, 16-Sep-86 10:32:09 EDT
Article-I.D.: gvax.505
Posted: Tue Sep 16 10:32:09 1986
Date-Received: Wed, 17-Sep-86 06:16:58 EDT
References: <15505@ucbvax.BERKELEY.EDU> <5100124@ccvaxa> <972@cit-vax.Caltech.Edu>
Reply-To: jqj@gvax.cs.cornell.edu (J Q Johnson)
Organization: Cornell Univ. CS Dept, Ithaca NY
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Keywords: :-)

JRB3 writes:
>The point is that our memory is based on electrons.

It has been argued that the number of electrons in the universe puts a bound
on the potential maximum memory size of a computer.  Reflection should convince
you that this argument is specious:  the real limitation is the number of
different energy states possible, and hence is constrained only by the Pauli
exclusion principal and by your imagination.  As a simple example, you can
encode more than 1 bit of data with a single electron in the shell of a
hydrogen atom simply by using different energy states.  For that matter you
can encode data within a nucleus by using different energy states.

Going one step further out, why use matter to encode data at all?   If you 
want bulk sequential storage, simply modulate an EM wave directed at a
distant point (that destination might be a reflector of some kind if you
know you will want to retrieve your data at the same location you generated
it).  Result:  effectively infinite bulk storage at the cost of a finite
and small number of electrons.  Granted it's not random access, but neither
are lots of existing technologies.

Of course, such storage techniques must come to grips with uncertainty, but
then, so must a memory based on the presence of electrons (note that even the
number of electrons in a container cannot be precisely specified!).