An international team of scientists has confirmed the existence of the gravitational redshift predicted by Albert Einstein in the framework of general relativity. For this, physicists used data from satellites GSAT-0201 and GSAT-0202, which in 2014 were launched into an incorrect elliptical orbit. This is reported by Science News.
Gravitational redshift is the effect in which light moving away from massive objects with strong gravity is shifted towards the red region of the spectrum. In addition, when approaching an object, any processes begin to go slower, which is called gravitational time dilation.
The satellites GSAT-0201 and GSAT-0202 were intended to test the European satellite navigation system Galileo, but there was a failure during launch, as a result of which the vehicles lay in an elongated orbit instead of a circular one. The satellites carried hydrogen masers, which are a form of atomic clocks, emitting electromagnetic waves of strict frequency. This gave scientists the opportunity to accurately measure the gravitational time dilation, since the vehicles, as they rotated around the Earth, moved away and approached it by 8.5 thousand kilometers.
The results showed that the clocks slowed and accelerated by tiny fractions of a second, consistent with the predictions of general relativity.