Speed Of Light Defines The Meter

For over a century, the world's standard for length was a physical object: a bar of platinum-iridium alloy stored under lock and key in Paris. This "International Prototype Metre" had a major flaw: it was unique and subject to physical change. Scientists around the world had to rely on less accurate copies, and the original itself could be damaged or degrade over time, making it an imperfect foundation (Review) for precision science. This created a need for a standard that was not based on a single artifact, but on a universal, unchanging property of nature itself.

The quest for a more universal standard led first to atomic physics, redefining the meter in 1960 based on the wavelength of light from krypton-86 atoms. But the ultimate