Halley’s Comet
Halley's Comet is the best-known of the short-period comets, and is visible from Earth every 75 to 76 years. Halley is the only short-period comet that is clearly visible to the naked eye, and thus, the only naked-eye comet that might appear twice in a human lifetime. Other naked-eye comets may be brighter and more spectacular, but will appear only once in thousands of years. Halley's returns to the inner solar system have been observed by astronomers since at least 240 BC, and recorded by Chinese, Babylonian, and mediaeval European chroniclers.
Al-Jazari created a programmable drum machine with pegs (cams) that bump into little levers that operated the percussion. The drummer could be made to play different rhythms and different drum patterns if the pegs were moved around. According to Charles B. Fowler, the automata were a “robot band” which performed “more than fifty facial and body actions during each musical selection.”
The elephant clock was described by Al-Jazari in 1206 is notable for several innovations. It was the first clock in which an automaton reacted after certain intervals of time (in this case, a humanoid robot striking the cymbal and a mechanical robotic bird chirping) and the first water clock to accurately record the passage of the temporal hours to match the uneven length of days throughout the year. 
