If I remove data from my hard drive, why doesn’t it weigh less?

A STAFF REPORT FROM THE STRAIGHT DOPE SCIENCE ADVISORY BOARD

Dear Straight Dope:

Why is it if I format my hard drive and get rid of a whole 4 gigabytes of data, the computer still feels like it weighs the same. Where did all that information go? Is there no weight to the programs I install on my computer?

Mac replies:

Of course not. Disk drives store things by magnetizing the surface of the disk … magnetized or not, the material is still there. Think of your hard drive as a deck of cards, some black, some white. When the disk is full of data, the black cards (the 1s) and the white cards (the 0s) are organized in a certain order. When you erase the disk, the cards are thoroughly scrambled, flipped over, whatever. But the weight of the cards–and the weight of the disk–stays the same.

Strictly speaking, most of the cards weren’t even scrambled–the name of the file was just changed in the HD’s “file allocation table” (index). That’s why you can recover the file using “undelete” utilities. But even if you used a utility that did scramble all the data, such as the one that comes with Norton Utilities, the drive would still weigh the same.

Send questions to Cecil via cecil@straightdope.com.

STAFF REPORTS ARE WRITTEN BY THE STRAIGHT DOPE SCIENCE ADVISORY BOARD, CECIL'S ONLINE AUXILIARY. THOUGH THE SDSAB DOES ITS BEST, THESE COLUMNS ARE EDITED BY ED ZOTTI, NOT CECIL, SO ACCURACYWISE YOU'D BETTER KEEP YOUR FINGERS CROSSED.

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