Mens Discount Luxury Watches > History of Watches
History of Watches
Time measurement dates to approximately 2000 BC. The Ancient Egyptians divided the day into two 12-hour periods and used large obelisks to track the movement of the Sun.
The earliest clocks relied on shadows cast by the sun, so they were not useful in cloudy weather or at night, and required recalibration as the seasons changed. The first clock with an escapement, which converts continuous rotational motion into an oscillating or back and forth motion., appeared in China Europe at the turn of the 14th century, and became the standard timekeeping device until the 20th century. During the 20th century, quartz oscillators were invented, followed by atomic clocks. Although first used in laboratories, quartz oscillators were both easy to produce and accurate, leading to their use in wristwatches. Atomic clocks are far more accurate than any previous timekeeping device, and are used to calibrate other clocks and to calculate the proper time on Earth; a standardized civil system, Coordinated Universal Time, is based on atomic time.
Escapement - An escapement drives the timekeeping element, usually a pendulum or balance wheel, in a clock or watch. It is powered by a gear train which is typically turned by a coiled spring or weight. Without the escapement, the system would simply unwind uncontrollably, but the escapement regulates this motion, controlled by the periodic swing of the pendulum or balance wheel. It allows the gears to advance or 'escape' a fixed amount with each swing, moving the timepiece's hands forward at a steady rate. A second function of the escapement is to keep the pendulum or balance wheel moving by giving it small pushes.
Each swing of the pendulum releases the escapement, making it change from a "locked" state to a "drive" state for a short period that ends when the next tooth on the gear hits the locking surface on the escapement. It is this periodic release of energy and rapid stopping that makes a clock "tick;" it is the sound of the gear train suddenly stopping when the escapement locks again.
A crystal oscillator is an electronic circuit that uses the mechanical resonance of a vibrating crystal of piezoelectric material to create an electrical signal with a very precise frequency. This frequency is commonly used to keep track of time (as in quartz wristwatches), to provide a stable clock signal for digital integrated circuits, and to stabilize frequencies for radio transmitters/receivers.
An atomic clock is a type of clock that uses an atomic resonance frequency standard as its timekeeping element. They are the most accurate time and frequency standards known, and are used as primary standards for international time distribution services, and to control the frequency of television broadcasts and GPS satellite signals.
Atomic clocks do not use radioactivity, but rather the precise microwave signal that electrons in atoms emit when they change energy levels. Early atomic clocks were masers
with attached equipment. Today's best atomic frequency standards (or clocks) are based on absorption spectroscopy of cold atoms in atomic fountains.