modern wall clocks designs

About modern wall clocks designs Android App

Only in the 1500s a locksmith from Germany found the hours until home with 10cm diameter of 12.5 cm and a thickness of 7.5 cm
At the end of the sixteenth century, the bells began to be made up, in the seventeenth century clockwork began to be fortified with a layer of brass and glass cover and stylus minutes
In 1656, was born Grandfather's Clock [clock with bells berpendulum] as a measure of time
Then its role as a reliable timepiece replaced by Kristal Quatrz which began to be applied on the hour with a very low error rate

At first, the second term in English is known as
"second minute" (second minute), which means that a small part of an hour.
The first part is known as the "prime minute" (minute premiere)
The same with minutes as it is known today.

The magnitude of this division fixated on 1/60, ie, there are 60 minutes in an hour
and there are 60 seconds in a minute.
This may be caused by the influence of the Babylonians,
which uses a count system based sexagesimal (base 60).

The term clock itself has been discovered by the Egyptians
the rotation of the earth as 1/24 of the mean solar day.
This makes the second as 1 / 86,400 of the mean solar day.

In 1956, the International Committee for Weights and Measures (CIPM)
under the mandate given by the General Conference on Weights and Measures (CGPM)
to ten in 1954, lays seconds in the period of rotation of the earth around the sun in the current epoch.

Because at that time have realized that the rotation of the earth on its axis is not quite uniform
to be used as the standard time.
Earth movement was described in Newcomb's Tables of the Sun (solar List Newcomb),
which gives a formula for the sun's movement in the epoch in 1900
based on astronomical observations made during the eighteenth and nineteenth centuries.

Thus the second is defined as
1 / 31,556,925.9747 part of the solar year in the date of January 1900 0 12 hours ephemeris time.
This definition was ratified by the General Conference on Weights and Measures to eleven in 1960.

A reference to the year 1900 does not mean that this is the epoch of the mean solar day contains 86,400 seconds.
Rather it is the epoch of the tropical year which contains 31,556,925.9747 seconds of Ephemeris Time.
Time Ephemeris (Ephemeris Time - ET) has been defined as a measure of time that gives
the position of celestial objects visible in accordance with Newton's theory of dynamic movement.

With the making of the atomic clock, it was determined the use of the atomic clock
as the basis for the definition of seconds, no longer with the rotation of the earth.

From the work of several years, two astronomers at the United States Naval Observatory (USNO)
and two astronomers at the National Physical Laboratory (Teddington, England)
determine the relationship of the hyperfine transition frequency of the cesium atom and the ephemeris second.

By using common-view measurement method based on signals received from radio station WWV,
they determine that the orbital motion of the moon around the earth
From which the apparent motion of the sun can be guessed, in units of atomic clock time.

As a result, in 1967, the General Conference on Weights and Measures defined the second of atomic time
in the International System of Units (SI) as the duration of 9,192,631,770
radiation with respect to the period of transition between the two hyperfine levels of the ground state of the cesium-133 atom.

Ground state is defined in the lack of circumstances (zero) magnetic field.
Seconds are defined the same as the second ephemeris.
Definition of seconds later was perfected in meetings BIPM to include the sentence

This definition refers to a cesium atom silent at a temperature of 0 K.
In practice, this means that the realization of seconds with high accuracy must compensate the effects of radiation around
to try mengextrapolasikan to the second price as mentioned above