[1] His older brother, Edward Hutchinson Synge (1890-1957), who was known as Hutchie, also won a Foundation Scholarship in Trinity for Mathematics, though he never graduated.

There he attended lectures by Ludwik Silberstein on the theory of relativity, stimulating him to contribute "A system of space-time co-ordinates", a letter in Nature in 1921.

[5][6] Synge returned to Trinity College Dublin, in 1925, where he was elected to a fellowship and was appointed the University Professor of Natural Philosophy[7] (the old name for physics).

In 1940, he supervised three Chinese students, Guo Yonghuai, Chien Wei-zang and Chia-Chiao Lin, who later became leading applied mathematicians in China and the United States.

Three years later he became Head of the Mathematics Department of the Carnegie Institute of Technology in Pittsburgh, where John Nash was one of his students.

He returned to Ireland in 1948, accepting the position of Senior Professor in the School of Theoretical Physics at the Dublin Institute for Advanced Studies.

This school had been set up in 1940, and had several outstanding members, including Erwin Schrödinger (who contributed to quantum mechanics), who was also a Senior Professor.

He studied an extensive range of mathematical physics problems, but his best known work revolved around using geometrical methods in general relativity.

[12] In pure mathematics, he is perhaps best known for Synge's theorem, which concerns the topology of closed orientable Riemannian manifold of positive sectional curvature.

He also created the game of Vish in which players compete to find circularity (vicious circles) in dictionary definitions.

Professor Hermann Bondi, who gave the first J. L. Synge Public Lecture in 1992, had this to say: "Every one of the other 88% has been deeply influenced by his geometric vision and the clarity of his expression".