Armillary sphere, 1731
This model of the solar system, or armillary sphere, was made for Frederick, George III's father, by Jonathan Sisson in 1731. The Earth, Moon and planets rotate about the Sun which is at the centre of the solar system. The horizontal ring is engraved with the Julian calendar and the signs of the zodiac. Each sign of the zodiac occurs eleven days earlier than they do today. This is because the calendar changed in 1752.
© Science Museum/Science & Society Picture Library