Massive objects warp the fabric of space to create natural cosmic magnifying glasses.

Gravitational lensing was first proposed as a consequence of Albert Einstein's General Theory of Relativity, published in 1915. Einstein suggested that gravity is not just a force between masses but a curvature of spacetime itself. In 1919, Sir Arthur Eddington confirmed this during a solar eclipse by observing stars near the Sun appearing slightly out of position.When a massive 'lens' like the galaxy cluster Abell 2218 sits between Earth and a distant object, it acts like a telescope. The gravity of the cluster bends the light paths from the background galaxy, often creating a circular distortion known as an Einstein Ring. This magnification can make distant objects appear up to 50 times brighter than they actually are.Modern astronomers use the Hubble Space Telescope and the James Webb Space Telescope to study these lenses. By analyzing the distortion, scientists can calculate the mass of the foreground object, including invisible dark matter. This technique has allowed researchers to observe galaxies formed only 500 million years after the Big Bang, providing a window into the early universe.