NASA | Using Quasars to Measure the Earth: A Brief History of VLBI - 3D

The video explains how the Earth's ground moves and wobbles on its axis, affecting the length of a day. Scientists use a technique called Very Long Baseline Interferometry (VLBI) to measure these movements precisely. Originally developed to take pictures of quasars, VLBI uses radio waves emitted by quasars to determine the relative movement of telescopes. By analyzing the time differences in wave reception, scientists can calculate the distance between telescopes and observe the Earth's movements. This technique helps understand the Earth's orientation and its subtle changes over time.

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