The history of clocks, sundials of Atomic Clocks

Humanity has always been concerned about the measuring and recording the passage of time. Timing was essential for the development of civilization to know when to plant or harvest crops to identify the most important events of the year.

Time has always been measured against the movement of the Earth, one day is a revolution of the planet, while a year is a full orbit of the sun. Calendars were developed from the lines up to 20,000 years, when hunter-gatherers scratched and dug holes in sticks and bones may count the days between phases of the moon.

Civilization of the ancient Egyptians to the Roman Empire have used different methods to find out what day of the year. However, the measurement time when he went the whole day had always been difficult for mankind begins. Sundials are perhaps the first time, and the pieces can trace their origins to more than five thousand years, obelisks, when they were built, probably to allow the story of time through the distribution of their shadows.

However, time has told a sundial is based on the movement of the sun in the sky, which differs according to the seasons and of course, do not work during cloudy days or at night. Other methods, such as water clocks or simply act as an hourglass timer crude. Telling time of day, it would be difficult with people on the basis of comparison of time as references, such as: "As long it would take a man to walk a quarter of a mile.

People were dependent on these methods and others such as the bell rings to indicate the important moments until the 14th century, when mechanical clocks appeared to have been guided by the weight is regulated by a point-and exhaust Foliot (a system of gears that advance the gear train at regular intervals or 'ticks'). These clocks were much more reliable than solar clocks or other reliable methods to tell the precise time of day for the first time in human history.

The next step in the middle of the night came in the 17th century, when the pendulum was developed to help maintain the accuracy of the clock. Watches spread rapidly and it was not for another three hundred years that the next revolutionary step the clock will take place with the development of electronic watches. They were sitting on the motion of a vibrating crystal (usually quartz) to create an electrical signal with an exact frequency.

While electronic watches were much more accurate than mechanical watches, it has the development of atomic clocks and about fifty years ago that modern technologies such as satellite communications, GPS and computer networks around the world became possible.

Most atomic clocks use the resonance of cesium-133, which vibrates only at a frequency of 9,192,631,770 every second. Since 1967, the international system of Units (SI) has defined the oscillators as the number of cycles of this atom makes atomic clocks (sometimes called cesium seconds) standard for measuring time.

Atomic clocks are accurate to less than 2 nanoseconds per day, equivalent to about one second in 1.4 million years. Because of this precision, a universal time scale UTC (Coordinated Universal Time or Universal Time Coordinated) was developed, which maintains a continuous scale and stable over time and supports features such as leap seconds - added to compensate for the slow rotation of the Earth .

However, atomic clocks are extremely expensive and are usually found in the physics laboratory scale. However, the NTP (Network Time Protocol), the standard way to obtain time synchronization networks of computers, you can synchronize networks of an atomic clock, using the Global Positioning System (GPS) network or specialist radio transmissions.

The development of atomic clocks, GPS and NTP time servers was vital to the modern technology that allows networks of computers around the world to be synchronized with the UTC.