Does a full 3TB hard drive weigh more than an empty one?

[Curl]

I'm not sure why you are bringing up 'time' all of a sudden, but it's not conceptually difficult to incorporate time into thermodynamics.

As for being 'bothered' that one can assign a quantitative amount of information to a word of English: there's not much I can do about that, other than to encourage you to keep learning until your conceptual conflict is resolved to your satisfaction.

Your thought experiment is flawed: the information about the system is then encoded in cupcakes: the number of cupcakes the demon ate is equal to the number of measurements taken. So the demon made an unauthorized copy of the information.

But the information about the particle (which could have yielded kT*log2 Joules of energy) is all of the sudden useless because the demon failed to act on the system in time. Thus the information is not destroyed, but becomes useless. This is why I don't understand how some declare that all information means decrease in entropy. This seems false, logically.

 

[Andy Resnick]

But the information about the particle (which could have yielded kT*log2 Joules of energy) is all of the sudden useless because the demon failed to act on the system in time. Thus the information is not destroyed, but becomes useless. This is why I don't understand how some declare that all information means decrease in entropy. This seems false, logically.

But the demon did *not* fail to act, unless the demon failed to eat a cupcake.

 

[Hellabyte]

If I define 'empty' as 'devoid of information' (i.e. all bits set to '0'), and 'full' as 'maximum information' (which would be a random string of 1's and 0's), then because there is a difference in entropy, there is a difference in total energy, and thus a difference in mass. The entropy per bit is kT ln(2), and from that you can calculate the change in mass.

I am very confused about the reasoning given here. Is the statement about the system having a different energy and therefore a different mass based on E=mc^2? The changing of 0s to 1s only affects the energy of the magnetic moment orientation. This doesn't have anything to do with the rest mass energy, or the rest mass associated with it...

I can't see how entropy can say anything one way or another about the mass of a system. Mass is not a thermodynamic quantity as far as I know.

 

[Andy Resnick]

I am very confused about the reasoning given here. Is the statement about the system having a different energy and therefore a different mass based on E=mc^2?

Yes.

The changing of 0s to 1s only affects the energy of the magnetic moment orientation. This doesn't have anything to do with the rest mass energy, or the rest mass associated with it...

Information is not the storage medium. Information is a way to quantify how far a message is from equilibrium.

 

[Hellabyte]

Yes.



Information is not the storage medium. Information is a way to quantify how far a message is from equilibrium.

To me, the usage of E=mc^2 is completely unfounded in this situation. It says that energy and mass can be converted into one another but just because a system has more "energy" that doesn't mean it has more mass. If i lift up a stone it has more gravitational potential energy, but it didn't gain any mass. You've given the magnetic dipoles more potential energy because of their orientation, but similarly the dipole doesn't gain any mass.