On Sat, Jan 28, 2012 at 09:41:27PM -0800, meekerdb wrote: > On 1/28/2012 3:42 PM, Russell Standish wrote: > >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. > > I don't think this is quite right. A higher temperature means that > there are more energy states available. But the concept of > 'temperature' implies that these are occupied in a random way > (according to the micro-canonical ensemble). For us to read and > write data requires that the act of reading or writing a bit moves > the distribution of states in phase space enough that it is > distinguishable from the random fluctuations due to temperature. > So > if the medium is hotter, you need to use more energy to read and > write a bit. This of course runs into the problems you note below.
Hence the requirement that technology not be fixed. It is a theoretician's answer :). > So in practice it is often colder systems that allow us to store > more data because then we can use small energy differences to encode > bits. Absolutely! But at zero kelvin, the information storage capacity of the device is precisely zero, so cooling only works to a certain point. > > Brent > > > > >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 > >> > > -- > 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 > everything-list+unsubscr...@googlegroups.com. > For more options, visit this group at > http://groups.google.com/group/everything-list?hl=en. -- ---------------------------------------------------------------------------- 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 everything-list+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/everything-list?hl=en.
