Does a hard drive weigh more when full..? - Page 19

Originally Posted by Art Vanelay 

It's impossible for all particles to be stopped because of it. I never looked into it; my dad took quantum physics in university, and he told me that.

Originally Posted by Blindrage606 

A HDD enclosure is vacuumed shut upon factory, which is more relevant than a one that is not in this discussion.

Great credibility reference there. Its still incorrect, as to Duckie and I trying to explain it to you.

Originally Posted by Blindrage606 

A HDD enclosure is vacuumed shut upon factory, which is more relevant than a one that is not in this discussion.

Originally Posted by Art Vanelay 

You cite the sources that Wikipedia lists.

Originally Posted by Sean Webster 

nope lol

Originally Posted by Blindrage606 

A HDD enclosure is vacuumed shut upon factory, which is more relevant than a one that is not in this discussion.
And also to 1 rep-wiki scholars, law of conservation of mass is not in any form dependent upon a closed system.
(i.e. burning a match does not equate to net loss weight but merely the carbon mass is dissipated through the atmosphere and heat.)

Originally Posted by Atomfix 

But but..... Why does a HDD have a breathing hole? It's not vaccumed huh

Originally Posted by Art Vanelay 

True vacuums don't exist. This is a thread labelled Does a hard drive weigh more full; why would I care about credibility. I later provided an explanation from wikipedia; could someone explain to me why that explanation was false? It proved the relation between ground state and the uncertainty principle through math.

Originally Posted by xbowtiekillax 

http://www.youtube.com/watch?feature=player_embedded&v=WaUzu-iksi8 this answers everything

Data stored on the disk do not change it's mass.

Bit's are stored by changing magnetisation of small grains in the
recording medium.
http://www.tvhandbook.com/support/pdf_files/audio/Chapter6_1.pdf

This is the same process (on microscopic scale) as magnetising a needle by
rubbing it with a permanent magnet. The process does not adds or removes mass
to or from the object.

Since you asked to include even the smallest changes in mass, we
need to consider the energy content of empty vs full disk. Increase
in energy by amount E will increase it's mass by amount E/ (c * c) - a
very small amount.

The writing of the disk requires energy, but that energy is not stored.
Magnetisation of the grain is a bistable system
http://www-civ.eng.cam.ac.uk/dsl/Bistable_actuation/main_project_page.html
Writing a bit is similar to rolling a stone up the hill, across the top,
from one valley to another. So, energy delivered on the way up is
returned on the way down. So far answer is still: Enefgy content is
not changed.
However, some of that energy will be dissipated as heat. Immediately
after recording, disk will be warmer and therefore heavier (not in a
measurable way). But that temperature rise will equilibrate to
enviroment - so that change is not permanent.

Finally, there is an interaction of magnetic moments with each other
and with external magnetic field ( e.g. Earth magnetism).

Each magnetic dipole (a grain seen as small permanent magnet) has energy
which depends on orientation of the dipole relative to external field.
http://hyperphysics.phy-astr.gsu.edu/hbase/magnetic/magpot.html

By writing on the disk, the total number if dipoles on one direction,
(let's say) pointing North, changes. However, number depends on the pattern
written, and empty disk has a pattern written on it when disk is formated.

So, this very small change depends on the data, and also on the orientation of
the whole disk as a unit. Becouse of this last fact (dependence on the
orientation of the object) I would summarise answer as follow:

Writing the data on the hard disk may change (increase or decrease)
total magnetic moment of the unit. That does not changes the mass of
the unit.
However, orientation of the unit in external magnetic field will effect total
energy of the unit. If we include mass equivalent of that energy in the term
'mass of the unit', that quantity may go up or down as a result of recording or
erasing (reformating the disk) of the data.