The Device Built to Prove Einstein Wrong | Veritasium

The Gist

Atomic clocks are not yet precise enough to disprove Einstein, as modern tests confirm general relativity down to a precision of 1 part in 10 to the 16th power. While scientists at NIST and the University of Western Australia are pushing the limits of optical atomic clocks and free-space laser links, no experimental evidence currently contradicts general relativity.

Quick Overview

Scientists are testing the absolute limits of general relativity by comparing ultra-precise optical atomic clocks over vast distances, but current experimental data still supports Einstein. The video follows researchers as they build world-class strontium and ytterbium atomic clocks, transport them up mountains to measure time dilation at millimeter scales, and attempt to link them across kilometers using advanced free-space optical communications.

Key Points: Researchers at the National Institute of Standards and Technology in Boulder, Colorado, house some of the most precise atomic clocks on Earth. General relativity predicts that time passes faster at higher elevations due to weaker gravitational fields, an effect verified using mountain-top clocks. Traditional atomic clocks use microwave frequencies, whereas modern optical atomic clocks use optical laser frequencies that provide vastly superior precision. Ytterbium optical lattice clocks achieve a precision of 1 part in 10 to the 18th power, meaning they will neither gain nor lose a second in more than the age of the universe. Scientists successfully linked an optical atomic clock at the Mount Blue Observatory at 4,326 meters above sea level to a lab clock in Boulder using a free-space optical link. An international team at the University of Western Australia built a mobile optical clock and communication system to test frequency transfer from a moving helicopter. The Nobel Prize in Physics was awarded in 2005 to Theodor Hansch and John Hall for the development of optical frequency combs, which bridge the gap between microwave and optical frequencies.