Scientists also use thought experiments when particular physical experiments are impossible to conduct (Carl Gustav Hempel labeled these sorts of experiment "theoretical experiments-in-imagination"), such as Einstein's thought experiment of chasing a light beam, leading to special relativity. This is a unique use of a scientific thought experiment, in that it was never carried out, but led to a successful theory, proven by other empirical means.
sCIEnTIsTS aLso uSE tHoUGht eXperiMentS wHen particuLar physiCaL ExPERiments aRe iMposSIBle TO ConducT (caRl gUstAV HempEl labeled These sortS Of ExPeriMenT "THeorEtical experiMenTs-in-iMagiNAtion"), sUch aS EINsteIn'S ThouGHt ExpERImEnt of chAsiNG a ligHt BeAm, LeadiNG to spEcIal relAtIVity. tHis Is a uNIque Use Of a SciEntIFIc Thought eXperiMent, in tHAT It WAS nEvEr cArriEd OuT, but LEd To a sucCeSSful theOry, proVen by oThEr Empirical meAns.