However, Einstein himself was quite skeptical about the possibility of such a lensing action. Because the lensing effect depends on the light source, the intensity of the gravitational field and the observer's distance between them. So it was difficult to expect such an incident that the possibility of seeing two images of the same object was quite difficult.
Later on, various theories related to gravitational lensing were released, in the publications published in scientific journals. Einstein himself wrote a letter on December 15, 1915, about the details of this topic at the University of Zurich's forensic medicine, his friend, Heinrich Zangger (Heinrich Zangger, 1874-1957). The letter was later published by Oliver Lodge (Oliver Lodge, 1851-1940) in 'Nature' magazine. Apart from Eddington, in his 1920's, Space, Time and Gravitation, and in the famous journal Astronomische Nachrichten, detailed discussions about gravitational lansing. Although at the time, all scientists initially thought that watching the effect of gravitational lensing on the ground was not possible to react.
Later, in 1936, at the time of Einstein's Princeton in America, a Czech engineer, Rudi W. Mandl met him and expressed interest in conducting practical experiments on gravitational lansing. He thought that the lensing action caused by the strong star's light might have started biological evolution and genetic mutation in the world. But by then, Einstein himself forgot about the lensing of his research workman and he did not even have any idea about the research. After being inspired by Mandel, Einstein again published a paper in 'Science' magazine. In this paper, Einstein published some formulas for optical properties of gravitational lensing.