Comment by zeotroph | Hacker News Reader

Comment by zeotroph | Hacker News Reader

On the '5D' claim: "The information encoding inside the disc is realised in five dimensions - the size and orientation of the nanostructures, in additional to their three-dimensional positions inside the disc." Those nanostructures are generated by a laser which alters the polarization of the material.

Is that even five dimensional? Polarization is one more, but can each point in space contribute to an arbitrary (or even just large) number of different polarization? I do not see where the fifth might come from.

The billion year claim does not seem to be validated, unlike similar research which used tungsten and silicon carbide[1], i.e. two different materials. The million/billion year durability was verified by substituting long periods of time with higher temperatures, i.e. heating the storage medium, and then checking the error rate.

[1]: https://doc.utwente.nl/74827/1/Vries2010MME.pdf / https://www.utwente.nl/en/news/!/2013/10/141415/a-mega-to-gi... (not peer reviewed?)

As I read it: 1. size 2. orientation 3-5. the usual dimensions.

Reading it as "five measurements" might be clearer.

Orientation is at least 2 dimensions (see e.g. spherical coordinates).

Orientation of a vector is 2 dimensions (spherical coordinates), orientation of a 3D object is 3 dimensions (Euler angles). It all boils down to the fact that you can rotate the vector using itself as its axis and it stays the same, but you can't do that with, say, a cube.

Hence I said "at least" :)

In the image of the data being read it looks like the laser only hits the structures from one direction. I think the "orientation" parameter is actually the polarization angle for the ray, so only one dimension.

Could be true, but then those spatial dimensions should probably be 2 instead of 3 (laser coming from one direction means you lose that direction).

Yeah, it's a bit sensationalist. By that logic you could argue that writing on a piece of paper is 4-D: horizontal and vertical position, what letter/symbol is there, and color. You could add font and underlines/italics to encode even more data per symbol if you wanted.

Well yea because a dimension is infinitely divisiable. so a dimension can hold infinite dimensions within it.

like i.e numbers.

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