http://www.eso.org/public/outreach/press-r...8/pr-26-08.html
This is needed to build the next generation of spectrographs to enable detection of Earth-like planets, dark energy etc. The required accuracy really is quite astonishing:
QUOTE
In fact, they must be accurate to about one part in 30 billions - a feat equivalent to measuring the circumference of the Earth to about a millimetre!
