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!

For more information about NASA’s Space Geodesy Project, click here!

NASA is now making movies in 3D!  If you want to see this movie in all live-action fun of 3D, click on this link.

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