Some 100 years ago, renowned physicist Albert Einstein came up with his General Theory of Relativity that hypothesised the existence of gravitational waves, which are said to be ripples in the fabric of time and space.

Now, the European Space Agency (ESA) is embarking on a mission to prove Einstein's century-old idea on gravitational waves.

On Thursday, the ESA launched the LISA Pathfinder on a Vega rocket from a spaceport in Kourou, French Guiana. This spacecraft will particularly test the "extraordinary technology" needed to observe gravitational waves in space.

The ESA's mission can be considered ambitious, since gravitational waves have never been observed before due to their extremely small size.

"Einstein's theory predicts that these fluctuations should be universal, generated by accelerating massive objects. However, they have not been directly detected to date because they are so tiny," the ESA explained in a statement posted on its website.

"For example, the ripples emitted by a pair of orbiting black holes would stretch a million kilometre-long ruler by less than the size of an atom," the European space agency further explained.

Alvaro Giménez Cañete, ESA's Director of Science and Robotic Exploration, even described gravitational waves as "the next frontier for astronomers."

"We have been looking at the Universe in visible light for millennia and across the whole electromagnetic spectrum in just the past century. But by testing the predictions made by Einstein one hundred years ago with LISA Pathfinder, we are paving the road towards a fundamentally new window on the Universe," Cañete was quoted as saying in the ESA statement.

To be able to accomplish its mission, the LISA Pathfinder has in its core identical 46 mm gold–platinum cubes separated by 38 cm. These cubes will be isolated from external and internal forces acting on them, except for gravity.

"The mission will put these cubes in the purest free-fall ever produced in space and monitor their relative positions to astonishing precision, laying the foundations for gravitational wave observatories in space," the ESA statement explained.