Apart from Jaina studies, Jacobi was interested in Indian mathematics, astrology and the natural sciences, and using astronomical information available in the Vedas, he tried to establish the date of their composition.

[citation needed] Jacobi's studies in astronomy have regained importance today in the context of the Out of India theory, because his calculations led him to believe that the hymns of the Rigveda were to be dated as early as 4500 B.C.

Thus he is the only renowned Western Indologist whose research supports the claim of the proponents of the theory that the Vedas are to be dated back much earlier than the first half of the second millennium B.C.

When Jacobi published his views in an article on the origin of Vedic culture in the Journal of the Royal Asiatic Society (1908), he therefore triggered off a major controversy in Indology.

[citation needed] In his later life, Jacobi interested himself in Ppoetry, epics, and philosophy, particularly the school of Nyaya-Vaisheshika.