> The problem is that the current IPK has lost a tiny bit of weight, in comparison with 40 similar cylinders held in other countries, which is a significant flaw in an object used to define a unit of mass. So the Avogadro Project has created two softball-sized, near-perfect spheres, made entirely of silicon-28 atoms, that should remain exactly one kilogram in perpetuity.

I seem to remember reading a while ago that no-one was quite sure why the reference kilogram was losing mass. Why should one therefore be confident that the new spheres will not do so?—or is this another 'distortion for convenience' of the article, like:

> Lie group E8, for instance, is a set of 248 different forms of symmetry that apply to a theoretical 57-dimensional object.

E_8 as a Lie group is 'continuous', and therefore infinite, and E_8 as a Weyl group has size much, much, much bigger than 248. The number 248 presumably comes from the dimension of the Lie group E_8 (and I suppose that one could twist words to accept that the dimension of the Lie group is somehow a reflection of the "number of different kinds of symmetries" that it contains); I'm not sure (but am not an expert on this, and so might just not know) whence comes the 57.