Regarding "From digits to dust" (Science & Technology, Apr. 20), information on a CD is created by burning tiny pits in the surface of the disk using a laser. There is nothing magnetic involved, and a CD cannot be affected by magnetism. Try running a magnet over a CD, then try to use in your computer; you should not have any problems. It is also unlikely that humidity would have much of an effect on a CD, whose base is typically made of aluminum. Oxidation and material decay could have an effect, but I believe these concerns are very long-term and would depend on the storage environment.

Joseph Warren

Burlingame, Calif.

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