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Tuesday, February 19, 2013

The Mass of Digital Data?


I said my laptop was too heavy, so someone suggested that I should delete some files so it would weigh less……. I was in dilemma whether I should laugh at him or believe him.

Time and again I questioned myself,  does raw stuff (like a song or a movie) weigh anything when it is in a hard drive. Because for me to be able to watch a movie on my computer, it has to get that information from somewhere in my hard drive.
I mean that the thing that I download in my hard disk contains mass or  is it  something mass less? 
Let’s approach to more clearer portion. The digital data that is stored in the hard disk or any other memory contains any mass i.e. the combinations of 1’s and 0’s have any mass?

In order to remove the crunch out of my head I began a study on the matter. The first thing I searched was , the  ways by which the digital data can be stored.
I found that there can be number of methods by which the digital data can be stored. A recent research at  Stanford University in California revealed that digital information can even  be stored in the DNA of living organisms. So leaving all the extraordinary methods of storing digital information behind let’s see the three basic methods by which the digital data are stored. They are:-
  1. Magnetic (eg. Hard Disk)
  2. Optical (eg.CD-ROM)
  3. Electrical (eg: Memory like SRAM,DRAM)


  • Magnetic:-

 Our computer’s hard drive uses magnets to store data. All magnets have a north and south pole. The hard drive has a magnetic disk that spins around and a small write head will flip the polarity of tiny magnetic poles on the disk. So it can create a positive pole for a 1 and a negative pole for a 0.
The only way in which energy is also stored in the disc is via the magnetic field. Misaligned magnets store more energy in the magnetic field than do aligned magnets.
i.e. organized data  has less entropy than pure randomness. So one can argue that there is difference of energy and show the mass of the data by energy mass relation(E=mc2 ). But the mass of the data is so small that it is even negligible in front of the mass of the dust in the hard disk.

  • Optical:-

There are basically millions of tiny etches on the cd. The cd spins and a laser is either reflected or absorbed by the cd, indicating a 1 or 0. Density depends on the wave length of the laser used to read and write. 
It is clear that the digital data stored in such way don’t have any mass.

  • Electrical

Memory in a computer comes in two types generally, SRAM and DRAM. DRAM, (Dynamic random access memory) uses a tiny capacitor to store a charge, indicating a 1, or the absence of electrical charge, to indicate a 0. This charge dissipates very quickly and must be refreshed thousands of times per second to maintain its state. Static RAM uses a circuit called a flip-flop which holds a 1 or 0 pretty much indefinitely. 
Both of these types of data storage require electric charge, and must be powered at all times.
When a capacitor is charged, electrons flow out of one plate and into the other plate, so the actual number of electrons in the capacitor remains the same - they have just been moved around.
Hence , the mass of the charged capacitor is same as that of the uncharged material.
But , according to classical physics it does depend on the types of substance that  is used for  making of capacitor.  If you have a material that cannot liberate electrons, so that the only way to charge it is by introducing electrons, then a charged capacitor may contain many more electrons than the uncharged one. The same thing as in magnetic disks  repeats here that the mass is negligible.

I finally got answer to my question . Now , I will give a slight smile (neither laugh at him nor follow his suggestion ) to that person who suggests me to erase my laptop data so that it weighs less.








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