An early Arabic navigational instrument for determining the Sun’s altitude by means of a transom and a knotted cord.
- Planets travel in elliptical (rather than circular or epicyclic) orbits, with the Sun at one of the foci.
- The line joining the Sun and the planet sweeps out equal areas of space in equal time intervals (so that the planet moves faster when it is nearer the Sun, and establishing the Sun as the main controller of the planets)
- The link between the size of the planet’s orbit and its period of rotation is described mathematically.klimata: (pron. clim-arta) part of an astrolabe, it is a disk rotating on the mater with the north celestial pole in the centre and showing almucantar lines for the design location. After the Ancient Greek meaning “angle of the Sun’s rays”, and hence the modern word “climate”.