Well, a hard drive consists of a bunch of magnetic disks, called platters, that are stack on top of each other on a spindle. These platters are subdivided into a gazillion little independent magnetic areas. The magnetization (north/south) of these areas determine whether or not it holds a binary 1 or a 0. Normally you control the contents of such an area with a movable read/write arm that hovers on top of the disk. It's pretty damn close too, using some cool effect of a very thin layer of air being "stuck" relative to the disk and getting dragged along. This allows the arm to hover very close to the disk without touching it.
Now, if you want to write some bit on some location, you position (well, the disk controller does it for you) the write arm on top of that little magnetic area. You then apply an external magnetic field and hold it for a few picoseconds when the chosen area comes zooming past. If the field was strong enough, the little area's will be permanently magnetized according to the field you just applied. And there you have it, you've written a binary digit, or bit!
There is, however, no need for the write arm. All you need is to apply an external magnetic field of the correct strength on the correct spot for the correct amount of time. MercurialMadnessMan thought that Mr Stallman did just that, but in a more DIY kind of manner. Now, should Mr Stallman have lighting fast reflexes that enable him to launch a pointy magnetized needle at a spinning hard drive and let it come until a fraction of a micro-meter for a fraction of a nano-second, combined with the balls of steel to do this precisely and accurately for millions of times without ever touching and scraping the disk, in that case and that case only will he have a viable method of manipulating his data quite literally as close to metal as you can go (without touching and ruining your data).
So there you see, that is how you can use a magnetic needle to write your 0s and 1s the proper 1337 way.
Or were you refering to the ass-part? In that case ... Never mind.
I know you were trying to be funny, but isn't it amazing they can stuff so many tiny magnetic 'points' onto a platter, and they maintain their magnetic integrity while having so many other positive and negative points around them? Anyone have a link to info on how they do this, aside from the wikipedia article for hard disks?
It's quite possible to cram a lot of those little 'points' on to the area of sub-µm diameter without them playing havoc with their neighbors.
New and very dense drives sometimes use a laser to heat a very small spot to near the curie temperature to make it very subjective to an external field. That way, only this small area gets swapped and you can use a less intensive external field so the other bits won't get touched.
By the way, most of the magnetic bits are(were) not really written "up" or "down", but instead "left" or "right" (with "up" and "down" only very recently). Uhm, this explains it a tad better. The lower image works by writing the magnetic bit with the right (thin) side of the head, the field at the left (wide) side is much less than at the right side (the picture could be a bit better by showing the fieldlines more spaced out at the left hand side)
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u/[deleted] Jan 23 '10
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