1. Hi all,

OK, I got a very interesting question posed to me, and honestly, I know not the answer...

I am the IT Manager of a K-8 charter school. The science teacher for the 5th and 6th grade posed this to me, and since I couldn't answer, I find myself here seeking it! I hope you can help...

Let's say that someone has an iPod. And this gadget has nothing on it, no music, no files, etc... Of course, it has a certain mass. Now, let's say that the owner adds ONE music file to it, a 5 megabyte file. Does the mass of the device increase? Do digital files have mass?

I hope I'm explaining my question correctly. I am not a scientist! I understand 0's & 1's... But I never even thought of something like this before... And it interested me when I heard it.

What do you think??

Thanks!

Chris

2.

3. I think it is the orientation of magnetic particles that causes the file to be saved - they are arranged towards or away from the reader, giving the 1s and 0s. So, the energy of the hard drive does not change, and nor does its relative mass.

I may be wrong, though. But this is my opinion.

4. That's kind of my understanding, too... The "space" (probably a terribly incorrect term) is there whether a "file" is or not... I don't think the mass would change, but if anyone can offer a definitive answer, I'd be very interested in hearing it. Thanks for the thoughts!

5. For magnetic storage devices, no, the mass won't change since, as drowsy said, it's just the orientation of magnetic particles. Turning something around won't make it any heavier, even on those scales (not that it's actually quite that simple).

For something like regenerative capacitor memory, the increase in energy may mean that an on-bit is slightly more massive than an off-bit, except that that energy came from the batteries, so if the bit is more massive, the battery is less so. (In fact, in total, the device is losing energy, so it'd be getting lighter. Of course, the amount of energy in question is small enough that I doubt any modern equipment could measure the difference.)

One of the two should apply to any type of modern computer memory as well as to any type of qubit, once we have quantum computers.

6. The answer to your question, "Do digital files have mass?" depends on the medium used. Also since files are nothing more than a combination of bits I will focus on how bits are stored.

As pointed out by previous posters a magnetic storage device (i.e. hard drive and in the olden days magnetic tape) stores bits by reversing the polarity of the magnetic medium. Writing or erasing does not change the mass of the medium.

Optical storage is different. CDs and DVDs store bits as pits and peaks on the readable surface. A blank CD or DVD has its surface smooth. A CD or DVD writer etches the pits onto the surface. Thus burning bits onto an optical disc would indicate that it actually looses mass. However since there are re-writable CDs and DVDs I highly doubt that, but I'm not sure. In short bits stored on an optical disc do not have mass.

Most portable electronics today use solid-state memory (Flash in particular). Flash stores its bits by trapping electrons inside its transistors. I would assume that a blank Flash drive did not have any trapped electrons, thus writing a file to it would theoretically increase the mass of the storage device. However a bigger file need not be more "massive". Since a transistor with trapped electrons is a 0 and one without the trapped electrons is 1, then it is possible that a larger file might have less 0's than a smaller file.

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