Re. Floppy disks and magnets

[Geoff Hart <geoff-h -at- MTL -dot- FERIC -dot- CA>]

     Mike Thompson asked about the dangers of X-rays and magnets to floppy
     disks. Mike, this one raises lots of vocal opinions on both sides,
     none with any really strong "scientific" evidence to back it up. For
     your consideration, I offer the following:

     1. A MacUser editor conducted a simple test with four high-density
     disks a few years ago; after the first pass through the X-rays, one
     disk was unreadable, and after four passes, not one was readable.
     (Actual numbers differ... I'm doing this from memory.) Conclusion: it
     was an old X-ray machine, and possibly poorly maintained. X-rays in
     low doses won't harm magnetic media, but the electromagnetic fields
     used to generate and control the X-rays surely can.

     2. Another author has set diskettes on the top of monitors, has rubbed
     them with speaker magnets and has had them X-rayed countless times
     with no damage whatsoever. Similarly, _Toronto Computes_ has tested
     diskettes atop the electric motors of the subway cars with no
     discernible effect.

     3. A friend lost data on a diskette subjected to the fields from one
     of those magic wands they use to scan you for metal if you fail to
     pass through the walk-through metal detector without a beep.

     In short (all together now!): your mileage may vary. I err on the side
     of caution, but there's considerable anecdotal evidence that it really
     doesn't make any difference what you do to your floppies, so long as
     you don't sit on them. Presumably the same applies to the much better
     shielded hard disks on a laptop. Note, however, that you should still
     ask security to check your laptop manually: I've seen so many bags
     flung off the end of the conveyor past the X-rays (or crushed by other
     bags) that I'd hold out for a manual check... and insist to see the
     manager and ask for his written guarantee to pay for any damage if
     they won't let you get away with a manual check.

     --Geoff Hart    @8^{)}
     geoff-h -at- mtl -dot- feric -dot- ca

     Disclaimer: If I didn't commit it in print in one of
     our reports, it don't represent FERIC's opinion.