Short answers, pulled from the story.
An orrery is a mechanical model of the solar system that illustrates or predicts the relative positions and motions of the planets and moons. It is typically driven by a clockwork mechanism, with a globe representing the Sun at the centre and planets mounted on extending arms. Orreries range in size from hand-held instruments to room-sized installations.
The word orrery comes from Charles Boyle, the 4th Earl of Orrery, for whom the instrument maker John Rowley produced a copy of a clockwork planetary model around 1712. Rowley had first built a copy for Prince Eugene of Savoy before receiving the commission for Boyle, whose earldom lay in County Cork, Ireland. The naming is often wrongly credited to Richard Steele; the error traces to a mistake in the writings of the lecturer John T. Desaguliers.
The Antikythera mechanism is a geocentric bronze device discovered in a shipwreck near the Greek island of Antikythera in 1901 and dated between 205 and 87 BC. Scholars consider it one of the first known orreries, likely used as a mechanical calculator to determine the positions of the Sun, Moon, and five planets.
The Eisinga Planetarium, built by the wool carder Eise Eisinga between 1774 and 1781 in Franeker, Netherlands, is an orrery that displays the planets across the width of a living room ceiling. It is powered by a pendulum clock with nine weights and has run almost without interruption since completion. The Dutch Royal family purchased the house and awarded Eisinga a pension.
An orrery models the solar system as a whole, while a tellurion shows only the Earth, Moon, and Sun, demonstrating the tilt of Earth's axis and its orbit. A lunarium is a device focused solely on the Moon's complex orbit around the Earth. Benjamin Martin proposed separating these three functions into distinct instruments in 1764.
A human orrery is a large-scale model in which people move as the planets and other solar system objects. Armagh Observatory in Northern Ireland has a permanent human orrery representing the six ancient planets, Ceres, and comets Halley and Encke. The human orrery at Sky's the Limit Observatory in Twentynine Palms, California, operates at a scale of twenty billion to one and is accurate to within four days.