In 1907, Einstein first
thought of the germ of a relativistic theory of
gravity.
This insight was to lead to the general theory of relativity in 1915 after a titanic
intellectual struggle.
“I was sitting in a chair in the patent
office in Bern when all of a sudden a
thought occurred to me: ‘If a person falls freely he
will not feel his own weight.’ I was startled. This simple
thought made a deep impression upon me. It impelled me
towards a theory of gravitation.”