I finished Season 4 of 24 yesterday. In one episode a hiker found a tiny radio transmitter under the leather of a briefcase with a compass. Then in a later episode the baddies trashed an apartment looking for a hidden portable hard drive. There's very strong magnets in a hard drive. Couldn't a compass reveal those fields? Could they have used the compass trick to find the hard drive?
It was easy to put my hands on my compass and a portable hard drive so I tried it out.
The compass definitely jumped all over the place when I put it near the hard drive. But it has to be REALLY near it.
|Compass held above the hard drive so it points|
to natural North.
|This is how close I had to get before it moved|
the needle significantly.
|So if you cram a hard drive between the cushions|
of your upholstered furniture nobody will find it
with a compass.
|Hmm. That's a magnetic field.|
|Up above the speaker is where it should point.|
I moved the speaker and moved the compass around the computer. Much less deflection of the needle. The high end driver of that speaker is a horn. The compression driver has a strong magnet quite close to where the Mac mini is. The midrange driver magnet is about the same distance the other direction.
But so what? Well, so what nothing. It's just interesting. Modern hard drives are virtually immune to normal everyday natural magnets. Besides, erasure requires a hard drive to MOVE THROUGH a magnetic field to reverse the polarity of the magnetic particles on the platters. And as you can see by the pictures, the field drops off quickly with distance. I'd need to rub the biggest speaker magnet I've got right on the case of the hard drive to have a chance of erasing it. And it probably still wouldn't count. The computer performs just fine in this magnetic field.
|Here's a piece of art I made out of hard drives from work I was told to destroy. |
Several parts spin.
For more fun with a compass I recommend running it over your iPad. It clatters around like mad. Very strong magnets in the smart cover.
*In case you missed it, Can you find a hidden hard drive with a compass? No. But you can have fun.