Reloj

Reloj

A clock is an instrument used to indicate, keep, and co-ordinate time. In general usage today a "clock" refers to any device for measuring and displaying the time. The clock is one of theoldest human inventions, meeting the need to consistently measure intervals of time shorter than the natural units: the day; the lunar month; and the year. Devices operating on several differentphysical processes have been used over the millennia. The sundial, which measures the time of day by using the sun casting a shadow onto a cylindrical stone, was widely used in ancient times. Awell-constructed sundial can measure local solar time with reasonable accuracy, and sundials continued to be used to monitor the performance of clocks until the modern era. However, its practical limitations itrequires the sun to shine and does not work at all during the night encouraged the use of other techniques for measuring time.

Brujula

A compass is a navigational instrument that measuresdirections in a frame of reference that is stationary relative to the surface of the earth. The frame of reference defines the four cardinal directions north, south, east, and west. Usually, a diagram calleda compass rose, which shows the directions, with their names usually abbreviated to initials, is marked on the compass. When the compass is in use, the rose is aligned with the real directions in theframe of reference. The compass was used in Song Dynasty China by the military for navigational orienteering

Telegrafo

Telegraph is the long-distance transmission of messages without thephysical exchange of an object bearing the message. Thus semaphore is a method of telegraphy Telegraphy requires that the method used for encoding the message be known to both sender and receiver. Suchmethods are designed according to the limits of the signalling medium used. The use of smoke signals, beacons, reflected light signals, and flag semaphore signals are early examples. In the 19th...