# Computer science professor claims e-books get heavier with each book stored. **URL:** \ **Category:** Miscellaneous and Personal Stuff I Must Share\ **Created:** [October 31, 2011, 1:36am UTC](https://boards.straightdope.com/t/computer-science-professor-claims-e-books-get-heavier-with-each-book-stored/601342 "2011-10-31T01:36:50Z")\ **Posts on this page:** 6\ **Page:** 2
**Author:** ![davidm](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/davidm/32/225_2.png) [@davidm](https://boards.straightdope.com/u/davidm)\ **Post date:** [October 31, 2011, 7:16pm UTC](https://boards.straightdope.com/t/computer-science-professor-claims-e-books-get-heavier-with-each-book-stored/601342/21 "2011-10-31T19:16:49Z")
> [@davidm](#): > > I’m not sure that that follows. Simply expending energy can’t always increase the weight. You expend energy to write a book to memory, but you also expend energy to erase it (or at least to remove it from the file index, bits are necessarily zeroed when a file is “erased”). So if expending energy increased weight, the device would gain weight every time you did anything with it! The editing window has passed, but that should have read 'bits _are **n’t** _ necessarily zeroed when a file is “erased” ’ ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 31, 2011, 7:47pm UTC](https://boards.straightdope.com/t/computer-science-professor-claims-e-books-get-heavier-with-each-book-stored/601342/22 "2011-10-31T19:47:44Z")
There isn’t enough information here to determine anything. I don’t know what this professor’s actual words were, or what type of memory is in these devices, or what state the memory is in before books are loaded. The device could actually be using memory that has been set to all 1s or all 0s initially, which requires more energy to maintain than after data has been loaded. Addressing some specific eBook device is kind of pointless without those details. ---
**Author:** ![Terr](https://avatars.discourse-cdn.com/v4/letter/t/839c29/32.png) [@Terr](https://boards.straightdope.com/u/Terr)\ **Post date:** [October 31, 2011, 8:06pm UTC](https://boards.straightdope.com/t/computer-science-professor-claims-e-books-get-heavier-with-each-book-stored/601342/23 "2011-10-31T20:06:37Z")
> [@TriPolar](#): > > The device could actually be using memory that has been set to all 1s or all 0s initially, which requires more energy to maintain than after data has been loaded. I think with flash memory (which is what those devices use) one bit state (call it 1) has more potential energy than the other (call it 0). So if it is all set to 0s initially, then a book gets loaded, the total potential energy increases, and so does the mass. ---
**Author:** ![mhendo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mhendo/32/3159_2.png) [@mhendo](https://boards.straightdope.com/u/mhendo)\ **Post date:** [November 2, 2011, 10:49pm UTC](https://boards.straightdope.com/t/computer-science-professor-claims-e-books-get-heavier-with-each-book-stored/601342/24 "2011-11-02T22:49:18Z")
Still wondering, **Lynn** what it is that makes you think that this professor, who works at one of the nation’s most highly-respected universities, is “misinformed” or “plain stupid”? ---
**Author:** ![Snarky\_Kong](https://avatars.discourse-cdn.com/v4/letter/s/a183cd/32.png) [@Snarky\_Kong](https://boards.straightdope.com/u/Snarky_Kong)\ **Post date:** [November 3, 2011, 2:00am UTC](https://boards.straightdope.com/t/computer-science-professor-claims-e-books-get-heavier-with-each-book-stored/601342/25 "2011-11-03T02:00:41Z")
> [@mhendo](#): > > Still wondering, **Lynn** what it is that makes you think that this professor, who works at one of the nation’s most highly-respected universities, is “misinformed” or “plain stupid”? I imagine she saw several of the very well respected scientific dopers on here agreeing with the professor (or at least saying that whatever he actually said is probably reasonable) and bailed. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [November 3, 2011, 2:31am UTC](https://boards.straightdope.com/t/computer-science-professor-claims-e-books-get-heavier-with-each-book-stored/601342/26 "2011-11-03T02:31:31Z")
> [@Terr](#): > > I think with flash memory (which is what those devices use) one bit state (call it 1) has more potential energy than the other (call it 0). > > So if it is all set to 0s initially, then a book gets loaded, the total potential energy increases, and so does the mass. But is it all set to 0s initially. Have these devices been through a QC process? They might be left full of information, possibly all 1s. The empty book could get lighter by loading new data. It is interesting to consider that the weight of these devices increases with certain types of data, even that tiny bit. I assume the data is compressed and will tend towards a balance of 1s and 0s once the book is full. [Previous page](https://boards.straightdope.com/t/computer-science-professor-claims-e-books-get-heavier-with-each-book-stored/601342.md?page=1)