A Deep-Sky Look at Lensing by Paul Gilster on January 13, 2011 As we continue to investigate the parameters of the proposed FOCAL mission to the SunÂ’s gravitational lens, itÂ’s worth recalling how the idea of lensing has taken hold in recent decades. Einstein noted the possibilities of such lensing as far back as 1936, but it wasnÂ’t until 1964 that Sydney Liebes (Stanford University) worked out the mathematical theory, explaining how a galaxy between the Earth and an extremely distant object like a quasar could focus the latterÂ’s light in ways that should be detectable by astronomers. And...