On Sat, Jan 28, 2012 at 12:05:57PM +0100, Evgenii Rudnyi wrote:
> Let us take a hard disk. Can I save more information on it at higher
> or lower temperatures?

This is a strictly ambiguous question. If we take the usual meaning of
hard disk as including a particular apparatus (heads, controller
logic, SATA interface and so on) to read and write the data, then
there will be a limited range of temperatures over which that
apparatus will operate. Outside of that range, (both higher and lower)
the information storage will fall to zero. That is a purely
engineering question.

On the other hand, if you just gave me the metallic platter from the
hard disk, and did not restrict in any way the technology used to read
and write the data, then in principle, the higher the temperature, the
more information is capable of being encoded on the disk. 

In practice, various phase transitions will make this more difficult
to achieve as temperature is increased. Passing the curie point, for
instance, will mean we can no longer rely on magnetism, although
presumably even below the curie point we can increase the information
storage in some other way (eg moving atoms around by an STM) and
ignoring the ferromagnetic behaviour. By the same token, passing the
freezing and boiling points will make it even harder - but still
doable with sufficiently advanced technology.

> >
> >>From an engineering viewpoint it looks a bit strange.
> > How so?
> >
> If engineers would take the statement "the maximum possible value
> for information increases with temperature" literally, they should
> operate a hard disk at higher temperatures (the higher the better
> according to such a statement). Yet this does not happens. Do you
> know why?
> In general we are surrounded devices that store information (hard
> discs, memory sticks, DVD, etc.). The information that these devices
> can store, I believe, is known with accuracy to one bit. 

Because they're engineered that way. It would be rather inconvenient if
one's information storage varied with temperature. 

> Can you
> suggest a thermodynamic state which entropy gives us exactly that
> amount of information?
> Here would be again a question about temperature. If I operate my
> memory stick in some reasonable range of temperatures, the
> information it contains does not change. Yet, the entropy in my view
> changes.

Sure - because they're engineered that way, and they operate a long
way from the theoretical maximum storage capability of that
matter. What's the problem with that?

> So these are my doubts for which I do not see an answer.
> Evgenii


Prof Russell Standish                  Phone 0425 253119 (mobile)
Principal, High Performance Coders
Visiting Professor of Mathematics      hpco...@hpcoders.com.au
University of New South Wales          http://www.hpcoders.com.au

You received this message because you are subscribed to the Google Groups 
"Everything List" group.
To post to this group, send email to everything-list@googlegroups.com.
To unsubscribe from this group, send email to 
For more options, visit this group at 

Reply via email to