NO I think I’ve read it in PC WORLD that they can only recover data if it has been overwritten up to 7 or 8 times after that it virtually impossible. I will try to find the article for you
No need... it isnt really that important, ok, maybe not 50 times. But ill bet you could recover it after quite a few more times with it being overwritten by only zeroes as compared to a cross random pattern of both ones and zeroes.
Unless there's some way for one writing to move up a chain of "past writes" after being overwritten, and be recoverable by specialized means, I can't see how this is true
Its isnt rocket science, just pretty advanced physics regarding elecromagnetism(i think?). Ill bet a relative of mine could answer you correctly, he is a doctor in theoretical physics and doctored by inventing a new magnetoresistive head that was more sensitive then what is in their normal measuring equipment. Its some kind of special cross reading head with double reading heads/coils at intersecting angles(Or something like that).
Anyway, a harddrive's plates aint by no means a perfect binary medium showing 1's or 0's. But showing something very close to 1 or 0. The heads dont register anything below a certain threshold, but that doesnt mean it isnt there, and can be read by something more sensitive, like an electron microscope that can see individual molecules. And residue charges that isnt seeable by a normal GMT(Giant Magnetoresistive) head is there.
IIRC it was something along these lines, although it was years since i read any physics so feel free to correct me if you find any holes. But its something along these lines.