How a Failed Satellite Launch Was Used To Test General Relativity

In 2014 the 5th and 6th satellites from Europe's Galileo navigation system were launched into the wrong orbit because of a design flaw in the Soyuz/Fregat upper stage. The satellites used on board station keeping fuel to put them into a semi useful orbit, and now, scientists have used the fantastically accurate clocks on board to test gravitational time dilation.
The result is the most accurate test yet of this effect, to within a factor of 0.0019% of what Einstein predicted a century ago.

Видео How a Failed Satellite Launch Was Used To Test General Relativity канала Scott Manley