[rescue] nuking from orbit

[G W Adkins]

> >left on the disk.  Try to tell John Voight from Christopher Walken
through a
> >picture of Anna Kournikova's backside.
>
> Your error is in assuming that the bits that will be changed will be
> exactly the same.
> Do you think that just one or two molecules is enough for the head to pick
> up the bit?  No, there are many many molecules that are charged, even with
> today's high bit densities.
> Do you think that the head, as it is flying over the surface, stays in
> EXACTLY EXACTLY the same location each time?  No, it does vary, by a small
> amount to be sure, but enough to figure out what is going on.
all these reasons are why after 27 write cycles, each with a MICROSCOPICALLY
different head alignment, the whole zone will be OBLITERATED.

>
> Do you think that you are dealing with an entirely digital process when
> dealing with a hard drive?  No, you are not.  Not every molecule is
charged
> in the area of a particular bit.
No, of course not, actually, the "charge" you speak of requires Multiple
Molecules in the first place.  And no, ti is not an entirely digital
process,  it is a digital process made up of fine grained analog values.
All computer systems we use today are...  even the switching done at the
transistor level in a CPU is analog if you look at it close enough.
My point is, even if you can erase only 90% of the blackboard, after I fill
and erase it 10 times, you will never be able to make out the 0.0005% image
of the first write among the 10% image of the last 100% coverage, stepping
bit, test pattern write.  it's analogous to:

filling a blackboard with text,
erasing it, leaving a 10% image
    let I=10:for 1 to I do;
        scribbling it over with 100% coverage with chalk
        and erasing it again
    loop:attempt to read text
end