I get this question quite a bit. "Sc.D." is Doctor of Science. It is M.I.T.'s equivalent of a Ph.D. degree. It is identical to a Ph.D. M.I.T. gives doctoral graduates the option of choosing between Ph.D. and Sc.D. when they graduate, because it is M.I.T. and they do things differently. And I chose an Sc.D. because I'm the same way.