Although last year's mislaunching of two Galileo satellites into the wrong orbit by the European Space Agency (ESA) made them inoperable due to their elliptical orbits from 13,713 km up to 25,900 km until they made their way back down, according to The Guardian, a team of researchers have successfully repurposed the satellites in order to test one aspect of Einstein's theory of general relativity, according to Public Radio International.
"They were supposed to go in a circular orbit, but now they go in an eccentric orbit," said experimental physicist Sven Herrmann. "And that gives us an excellent opportunity to test ... a very basic prediction of general relativity. That clock [on board the satellite] that is closer to a massive object like Earth will seem to tick a bit more slowly than a clock that is located further away. And the clocks on board those satellites, they are now doing exactly this. They are approaching Earth and going back and forth with every revolution on the orbits that they do about twice a day."
The clocks on each of the satellites are designed for the purpose of positioning and navigation, leading Herrmann to believe that they are sufficient to test Einstein's theory of relativity. If the experiment goes according to plan, Herrmann believes that the clocks will shift microseconds as they make their way around the Earth, and this shifting will support Einstein's theory. This experiment will last a year in order to control for any systematic errors.
"This general relativity is just such a very basic theory. It's essentially defining our understanding of space and time. So it's a very basic [theory] of physics that I think we are obliged really to test to the best of what technology can provide us with," Herrmann said. "Especially if you look at the problem that is something many physicists try to tackle today - the unification of gravity theory that's General Relativity and Quantum Theory on the other hand. They're two big theories in physics that are seemingly incompatible."
The two satellites form a part of the Galileo system, the European Union's billion-dollar satellite navigation system that has cost them £4.8 billion as of now and has a total budget of £7 billion, according to The Independent.
