Sayyed Mahmoud Hessaby (in Persian سید محمود حسابی - alternative spellings: Mahmood Hesabi) (February 23, 1903, Tehran – September 3, 1992, Geneva) was a prominent Iranian scientist, researcher and distinguished professor of University of Tehran. During the congress on "60 years of physics in Iran" the services rendered by him were deeply appreciated and he was called "the father of modern physics in Iran".

Hessaby was born in Tehran to Abbas and Goharshad Hessaby. When he was seven, the family moved from Iran to Beirut in Lebanon where he attended school.

At seventeen he obtained his Bachelor's in Arts and Sciences from the American University of Beirut. Later he obtained his B.A. in civil engineering while working as a draftsman. He continued his studies and graduated from Engineering school of Beirut.

Hessaby was admitted to the École Superieure d'Electricité and in 1925 graduated while he was employed by the SNCF (French National Railway). He started working in the electric locomotive maintenance department. Hew was a scientific mind and continued his research in Physics at the Sorbonne University and obtained his Ph.D. in Physics from that University at the age of twenty-five.

Albert Einstein ( /ˈælbərt ˈaɪnstaɪn/; German: [ˈalbɐt ˈaɪnʃtaɪn] ( listen); 14 March 1879 – 18 April 1955) was a German theoretical physicist who developed the theory of general relativity, effecting a revolution in physics. For this achievement, Einstein is often regarded as the father of modern physics. While best known for his mass–energy equivalence formula E = mc² (which has been dubbed "the world's most famous equation"), he received the 1921 Nobel Prize in Physics "for his services to theoretical physics, and especially for his discovery of the law of the photoelectric effect". The latter was pivotal in establishing quantum theory within physics.

Near the beginning of his career, Einstein thought that Newtonian mechanics was no longer enough to reconcile the laws of classical mechanics with the laws of the electromagnetic field. This led to the development of his special theory of relativity. He realized, however, that the principle of relativity could also be extended to gravitational fields, and with his subsequent theory of gravitation in 1916, he published a paper on the general theory of relativity. He continued to deal with problems of statistical mechanics and quantum theory, which led to his explanations of particle theory and the motion of molecules. He also investigated the thermal properties of light which laid the foundation of the photon theory of light. In 1917, Einstein applied the general theory of relativity to model the structure of the universe as a whole.