Contact: Liz Zubritsky
elizabeth.a.zubritsky@nasa.gov
301-614-5438
NASA/Goddard Space Flight Center

Using Quasars to Measure the Earth's Extra Second: A Brief History of VLBI

Caption: VLBI, or Very Long Baseline Interferometry, is a technique that uses multiple radio telescopes to very precisely measure the Earth's orientation. It was originally invented back in the 1960s to take better pictures of quasars, but scientists soon found out that if you threw the process in reverse, you could measure how the ground beneath the telescopes moves around, how long days really are, and how the Earth wobbles on its axis as it revolves around the sun.

Credit: NASA/SVS

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