Free Astronomy Magazine July-August 2015

37 T he light from a galaxy dis- tributed along an almost full ring – and this is essen- tially SDP.81. [ALMA (NRAO/ESO/ NAOJ)/Y. Tamura (The University of Tokyo)] The video on the side shows the gravitational lensing distorting a galaxy by turn- ing it into a ring. [ALMA (NRAO/ESO/ NAOJ)/Luis Cal- çada (ESO)] precedented JULY-AUGUST 2015 A s predicted by Albert Einstein's the- ory of general relativity, a celestial body of great mass bends space- time and the amount of curvature is proportional to the mass. One of the consequences of that highly- verified prediction is that a mass in- terposed between a light source and the observer will deviate the photons emitted by the source from the straight line of propaga- tion, causing them to be perceived as coming from a different position than the original one. Depending on the amount and distribution of the interposed mass, the original COSMOLOGY image of the source could be intensified, re- versed, inverted, multiplied and distorted in various ways. From the Earth we perceive