Originally Posted By: Alex
The fact is - the heavily used sewing needles eventually became magnetic. IMHO, Rob's physics sounds somewhat perfunctory, he is probably just doing something wrong.
He showed that even unused needles are often magnetised. To show that usage made a difference, you'd need to show they weren't magnetised to start with.

They may have become magnetised by stray fields in the factory etc. I suspect that they can also pick up the Earth's magnetic field eventually, eg in storage.
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