One hundred years ago this month, Albert Einstein published his theory of general relativity, one of the most important scientific achievements in the last century.A key result of Einstein’s theory is that matter warps space-time, and thus a massive object can cause an observable bending of light from a background object.  The first success of the theory was the observation, during a solar eclipse, that light from a distant background star was deflected by the predicted amount as it passed near the sun.Astronomers have since found many examples of this phenomenon, known as “gravitational lensing.” More than just a cosmic illusion, gravitational lensing provides astronomers with a way of probing extremely distant galaxies and groups of galaxies in ways that would otherwise be impossible even with the most powerful telescopes.

Source: Where Alice in Wonderland Meets Albert Einstein | NASA