Preserving a DVD with Liquid Nitrogen


Written by:

Robert McIntyre

Here's the game: you have a message that's about 1 Gigabyte long, and you want to preserve it for as long as possible. Not just a few years, or even a few decades or centuries, but for thousands to millions of years!

It's a cool engineering question because you can explore what happens if society collapses for a time, or if the climate changes dramatically.

Some good ideas I've heard so far have been:

I was surprised to learn that modern DVDs won't really last for much more than around 50 years, because the dyes and plastic they're made of slowly chemically degrade over time. However, if you put a DVD in liquid nitrogen, the extreme cold stretches that 50+ years into trillions upon trillions of years! I was curious as to whether I could cool down a DVD to liquid nitrogen temperature, warm it up, and then read the data again.

So, here are a few scripts to help in the experiment:

One to create a DVD image, which is around 3.5GB.

mkisofs -iso-level 4 -r -o ./test-image.iso \
        -graft-points test-files=test-files

One to burn the image to the DVD.

growisofs -dvd-compat -Z /dev/cdrom=./test-image.iso

And another to compare the DVD to the image files.

mkdir -pv cd-mount
sudo mount /dev/sr0 cd-mount
diff -sr test-files cd-mount/test-files
sudo umount cd-mount
rmdir cd-mount

And without further ado, the experiment!

An experiment was carried out to determine whether a DVD could survive exposure to extreme cold.

Contained within the boiling liquid nitrogen, all chemical reactions cease. The only things that interact with the DVD are light (put it in a dark container), cosmic rays (which don't damage the relatively large data storage components of the DVD), and the kinetics of the liquid nitrogen itself (embed the DVD in a solid container and don't let it touch the LN).

If only it was for people as it is for DVDs…

Author: Robert McIntyre

Created: 2015-04-19 Sun 19:55

Emacs 24.4.1 (Org mode 8.3beta)