Model of the transit of Venus, 1748-1761.
© Science Museum / Science & Society Picture Library
This model was made by the London instrument maker Benjamin Cole. It shows the transit of Venus, demonstrating how Venus pases in front of the Sun as seen from the Earth. By turning the handle, the bras Venus arm rotates about the Sun, indicating a transit when the pivot on the bras ring aligns with the Earth globe. This model was made for the Royal Society as a demonstration device to popularise such rare celestial events. Transits of Venus occurred in 1761 and 1769 and then not for more than a century. By timing these events from far-flung parts on the world, astronomers were for the first time able to determine an accurate distance to the Sun, and hence the size of the Solar System.