Data storage has been a concern ever since man started to make significant scientific discoveries (from fire to the wheel to the steam engine).While cave paintings and papyrus seemed a means to preserve their observations of the world around them, only a few documents have made it to this day and age, but many valuable, informative historically significant documents were washed away in the depths of time…sometimes due to lack of proper preservation and sometimes due to natural calamities.
We have progressed since then, and so has our data storage methodology. Recent discoveries in this field by Jeroen de Vries at the University of Twente in the Netherlands have given us a means to preserve our thoughts and discoveries for the sake of posterity. They have designed and built a disk capable of storing data over a timescale of a million years. And they have performed accelerated ageing tests which show it should be able to store data for 1 million years and possibly longer.
As it is impractical to conduct an ageing experiment in real time, particularly when the periods involved are measured in millions of years, there seems to be a way to accelerate the process of ageing.
This is based on the idea that data must be stored in an energy minimum that is separated from other minima by an energy barrier. So to corrupt data by converting a 0 to a 1, for example, requires enough energy to overcome this barrier.
The probability that the system will jump in this way is governed by an idea known as Arrhenius law. This relates the probability of jumping the barrier to factors such as its temperature, the Boltzmann constant and how often a jump can be attempted, which is related to the level of atomic vibrations.
Some straightforward calculations reveal that to last a million years, the required energy barrier is 63 KT or 70 KT to last a billion years. “These values are well within the range of today’s technology,” say de Vries and co.
And to prove the point, they go ahead and build a disk capable of storing information for this period of time. The disk is simple in conception. The data is stored in the pattern of lines etched into a thin metal disc and then covered with a protective layer.
The metal in question is tungsten, which they chose because of its high melting temperature (3,422 degrees C) and low thermal expansion coefficient. The protective layer is silicon nitride (Si3N4) chosen because of its high resistance to fracture and its low thermal expansion coefficient.
They made their disc using standard patterning techniques and stored data in the form of QR codes with lines 100nm wide. They then heated the disks at various temperatures to see how the data fared.
The results are impressive. According to Arrhenius law, a disk capable of surviving a million years would have to survive 1 hour at 445 Kelvin(172 oC), a test that the new disks passed with ease. Indeed, they survived temperatures up to 848 Kelvin(575 oC), albeit with significant amounts of information loss.
That compares well with the Rosetta Project, a proposal by the Long Now Foundation to create archival materials capable of storing information for periods in excess of 10,000 years.
The new work suggests we ought to be able to preserve a significant amount of information for future civilizations, perhaps even alien ones.
There are limitations, of course. The theory behind accelerated aging only applies in very specific circumstances and says nothing about survivability in other cases. It’s hard to imagine the new disk surviving a meteor strike (for example). Indeed, it would be unlikely to survive the temperatures that can occur in an ordinary house fire.
Researchers are confident that they can make more durable data storage systems. Their work is an interesting step towards preserving our data for future civilizations.
