There is a push to redefine the kilogram into something beyond a mass kept in a lab somewhere. While standard length of 1 meter and standard time of 1 second are tied to various fundamental constant, the standard mass of 1 kilogram is still tied to some fiducial object. This latest attempt at a precise measurement of Avogadro's number using silicon-28 strengthened the case to redefine the kilogram.
The latest result from a team led by Peter Becker of the Federal Institute of Physical and Technical Affairs (PTB) in Braunschweig, Germany, published on arXiv (P. Andreas et al. Preprint at http://arxiv.org/abs/1010.2317; 2010), comes closer than ever to ending the cylinder's reign. The team has measured the number of atoms in a sphere of silicon-28 to calculate Avogadro's constant to nine significant figures: 6.02214084(18) × 1023 mol−1. The constant refers to the number of atoms in a sample whose bulk mass in grams equals the relative atomic mass of the element. This general relationship makes Avogadro's constant a fixed point from which to define mass.