            By 1912, however, Einstein had reached an impasse  , realizing that he needed to go beyond the mathematics that he knew and was familiar with.
<meaning-changed>             By 1912, however, Einstein had reached an impasse  , realizing that he needed to go beyond the mathematics that he knew and was familiar with.
 Einstein then considered sending a continuous electromagnetic beam of frequency (as measured at ) from to in a homogeneous gravitational field. The frequency of the light as measured at will be a larger value given by By 1912, however, Einstein had reached an impasse , realizing that he needed to go beyond the mathematics that he knew and was familiar with.