Portal:History of science/Picture/16

This armillary sphere is one of many astronomical instruments designed by Danish astronomer Tycho Brahe. In his Astronomiæ Instauratæ Mechanica (1598), he describe the unique features of this particular armillary device, the "equatorial armillary instrument." It featured a balanced design that circumvented problems in earlier spheres in which the weight of the poles would pull the rotating planes into a rest position.