Observational history of comets
Halley at first agreed with the longtime consensus that each comet was a different entity making a single visit to the solar system. In 1705, he applied Newton's method to 23 cometary apparitions that had occurred between 1337 and 1698. Halley noted that three of these, the comets of 1531, 1607, and 1682, had very similar orbital elements, and he was further able to account for the slight differences in their orbits in terms of gravitational perturbation by Jupiter and Saturn. Confident that these three apparitions had been three appearances of the same comet, he predicted that it would appear again in 1758–9. (Earlier, Robert Hooke had identified the comet of 1664 with that of 1618, while Giovanni Domenico Cassini had suspected the identity of the comets of 1577, 1665, and 1680. Both were incorrect.) Halley's predicted return date was later refined by a team of three French mathematicians: Alexis Clairaut, Joseph Lalande, and Nicole-Reine Lepaute, who predicted the date of the comet's 1759 perihelion to within one month's accuracy. Halley died before the comet's return; when it returned as predicted, it became known as Halley's Comet (with the latter-day designation of 1P/Halley). The comet next appears in 2061.
Gunvalkyrie
The game takes place in an alternate history in 1906 where the British Empire rules all of Earth and several extrasolar colony worlds, powered by technology brought to the planet by Halley's Comet in 1835. An unknown substance known as Halley's Core was found throughout the world, and certain individuals who came in contact with it and gained superhuman abilities became known as "Halley's Chosen." The first of these was a scientist named Dr. Hebble Gate, who was affected by the comet while in his mother's womb. With his superhuman mind he harnessed the power of Halley's Core and discovered a wide range of scientific breakthroughs, including fusion and nuclear power, genetic engineering, computers, space travel and countless others. With these technologies the British Empire quickly conquered the earth, and Gate is famous as the man responsible. A complete mystery to all, Gate also holds great power over economic, political and military affairs, and is the founder of the Hebble Foundation and the GunValkyrie (GV) Organization, composed of Halley's Chosen throughout the world to prevent the misuse of technology. He suddenly disappears, throwing the world into shock, and has been missing for four years by the time the game begins.