<human>:  Why do the Halley’s Comets have such a long orbital period?
<bot>: Halley’s Comet has an orbital period of 76 years. It was named after Edmund Halley, who was the first to propose that comets were not a random occurrence, but were instead the result of the gravitational perturbations of the planets. Halley was a British astronomer and mathematician, who made several important contributions to astronomy and mathematics, including the eponymous law of universal gravitation.