|MadSci Network: Other|
Magnetic fields will erase or scramble the information on cassette tapes if the fields are strong enough. Refrigerator magnets are plenty strong enough. You can shield things from electrical fields by wrapping them in a conductor. Unlike the case of electrical fields, there really is no simple shielding for magnetic fields (except of course superconductors). Cassette tapes are really a thin layer of magnets. The magnetized (recorded) tape can "print through" from one layer to another over time. You can minimize this phenomenon, by fast forwarding and rewinding stored tapes every year or so. You protect tapes by keeping magnets away from them. Educate people about this danger; don't carry magnets around with tapes or computer disks. Hope this helps. David Winsemius.
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