Accurate Measurement of Large Distances Using Laser Technology at Nanometer Precision

A new method of measuring distance using lasers can measure lengths from more than 100 kilometers to within a thousandth of the width of a human hair, and could be used to build better space telescopes.

In a laboratory setting, scientists can use lasers to measure extremely precise distances within a few nanometers. However, over long distances of 1 kilometer or more, these techniques tend to be much less accurate, to within about 1 millimeter.