... Credit Copyright: NASA , ESA , Hubble Heritage/ESA-Hubble Collaboration - Acknowledgment: Nick Rose Explanation: Want to use a cluster of galaxies as a telescope? It's easier than you might think as distant galaxy clusters naturally act as strong gravitional lenses. In accordance with Einstein's theory of general relativity, the cluster gravitational mass, dominated by dark matter, bends light and creates magnified, distorted images of even more distant background galaxies. ...