TAI as a time scale is a weighted average of the time kept by over 200 atomic clocks in over 50 national laboratories worldwide.

Early atomic time scales consisted of quartz clocks with frequencies calibrated by a single atomic clock ; the atomic clocks were not operated continuously.

Two of the most well-known applications of the pure elements are rubidium and caesium atomic clocks, of which caesium atomic clocks are the most accurate representation of time known as of.

Since then, caesium has been widely used in atomic clocks.

ET was used for the calibration of atomic clocks in the 1950s.

Increasingly, after the calibration in 1958 of the cesium atomic clock by reference to ephemeris time, cesium atomic clocks running on the basis of ephemeris seconds began to be used and kept in step with ephemeris time.

The atomic clocks offered a further secondary realization of ET, on a quasi-real time basis that soon proved to be more useful than the primary ET standard: not only more convenient, but also more precisely uniform than the primary standard itself.

Such secondary realizations were used and described as ' ET ', with an awareness that the time scales based on the atomic clocks were not identical to that defined by the primary ephemeris time standard, but rather, an improvement over it on account of their closer approximation to uniformity.

The availability of atomic clocks, together with the increasing accuracy of astronomical observations ( which meant that relativistic corrections were at least in the foreseeable future no longer going to be small enough to be neglected ), led to the eventual replacement of the ephemeris time standard by more refined time scales including terrestrial time and barycentric dynamical time, to which ET can be seen as an approximation.

Caesium atomic clocks became operational in 1955, and quickly confirmed the evidence that the rotation of the earth fluctuated randomly.

Pulsars, when first discovered, were called LGMs ( Little Green Men ), because of the precise repetition of their pulses ( they rival the best atomic clocks ).

In 1956, the German-American physicist Friedwardt Winterberg proposed a test of general relativity ( for time slowing in a strong gravitational field ) using accurate atomic clocks placed in orbit inside artificial satellites.

( To achieve accuracy requirements, GPS uses principles of general relativity to correct the satellites ' atomic clocks.

Gravitational time dilation in the Earth's gravitational field has been measured numerous times using atomic clocks, while ongoing validation is provided as a side effect of the operation of the Global Positioning System ( GPS ).

In 1911, Ernest Rutherford gave a model of the atom in which a central core held most of the atom's mass and a positive charge which, in units of the electron's charge, was to be approximately equal to half of the atom's atomic weight, expressed in numbers of hydrogen atoms.

In addition, Moseley predicted the two more undiscovered elements, those with the atomic numbers 72 and 75, and gave very strong evidence that there were no other gaps in the Periodic Table between the elements aluminium ( atomic number 13 ) and gold ( atomic number 79 ).

The chemical element tantalum ( symbol Ta, atomic number 73 ) is named after the mythological Tantalus ; its lack of reactivity, and the resulting difficulty in isolating the pure metal from ore, gave the element its name, by analogy ; the pure metal tantalized chemists.

* In 2009, when the International Organization for Standardization published updated versions of ISO 80000, it gave mixed messages as to whether or not the unified atomic mass unit had been deprecated: ISO ISO 80000-1: 2009 ( General ), identified the dalton as having " earlier called the unified atomic mass unit u ", but ISO 80000-10: 2009 ( atomic and nuclear physics ) catalogued both as being alternatives for each other.

Dalton communicated his atomic theory to Thomson who, by consent, included an outline of it in the third edition of his System of Chemistry ( 1807 ), and Dalton gave a further account of it in the first part of the first volume of his New System of Chemical Philosophy ( 1808 ).

" This equivalence had been pointed out by Hamilton a century earlier, and published by him around 1830, in an era where no experience gave proof of the fundamental principles of physics being involved in the description of atomic phenomena.

Theodore Alvin Hall ( October 20, 1925 – November 1, 1999 ) was an American physicist and an atomic spy for the Soviet Union, who, during his work on US efforts to develop the first and second atomic bombs during World War II ( the Manhattan Project ), gave a detailed description of the " Fat Man " plutonium bomb, and of several processes for purifying plutonium, to Soviet intelligence.

A number of project members — some high-profile — voluntarily gave secret information to Soviet agents, many because they were ardent communists or were sympathetic to the Soviet Union's role in the war and did not feel the U. S. should have a monopoly on atomic weapons.

Hegel responded to Kant's philosophy by suggesting that the unsolvable contradictions given by Kant in his Antinomies of Pure Reason applied not only to the four areas Kant gave ( world as infinite vs. finite, material as composite vs. atomic, etc.

After the dropping of atomic bombs on Hiroshima and Nagasaki, several women close to ground zero who had been pregnant at the time gave birth to children with microcephaly.

Two of the spies who gave atomic secrets to Russia were tried and executed.

While the test gave a good approximation of many of the explosion's effects, it did not give an appreciable understanding of Nuclear fallout, which was not well understood by the project scientists until well after the atomic bombings of Hiroshima and Nagasaki.

In atomic physics, spectroscopy gave observational data on atomic transitions arising from the interactions of atoms with light quanta.

Einstein's statistical discussion of atomic behavior gave experimentalists a way to count atoms by looking through an ordinary microscope.

Ironically the Russians may have seen it first — atomic spy Klaus Fuchs gave Harry Gold a copy which arrived in Moscow on October 29, 1945, and was noted upon that the physicists ' " feelings of distrust toward the government are very strong.

The Authority was established on 19 July 1954 when the Atomic Energy Authority Act 1954 received Royal Assent and gave Authority the power “ to produce, use and dispose of atomic energy and carry out research into any matters therewith ”.

He gave a preliminary age estimate of 10 < sup > 11 </ sup >/ A years, where A is the mean atomic weight of the nuclei in the star.

This corrugation gives rise to strong electric field gradients in the near-tip zone ( on the order of an atomic radii or less from the tip ), which during ionisation deflects ions away from the electric field normal.

With the rise of new ideas after the ground break of Saussure's work, prestructuralist diachronic semantics was considerably criticized for the atomic study of words, the diachronic approach and the mingle of nonlinguistics spheres of investigation.

Vitalism survived for a while even after the rise of modern atomic theory and the replacement of the Aristotelian elements by those we know today.

While the 19th century had seen the success of the wave theory at describing light, it had also witnessed the rise of the atomic theory at describing matter.

The rise of fascist governments in Europe, new discoveries about the nature of atoms and the fear that Nazi Germany was working on developing atomic bombs converged in the plans of the United States, the United Kingdom, and Canada to develop powerful weapons using nuclear fission as their primary source of energy.

In the case of a battery, charge separation that gives rise to a voltage difference is accomplished by chemical reactions at the electrodes ; a voltaic cell can be thought of as having a " charge pump " of atomic dimensions at each electrode, that is:

The rise in popularity has been linked with the real-life development of the atomic bomb in 1945 and subsequent nuclear testing in the 1950s ; the fear of annihilation paralleling its depiction in popular media.

These miscuts give rise to atomic steps on the surface.

Some atomic nuclei possess a magnetic moment ( nuclear spin ), which gives rise to different energy levels and resonance frequencies in a magnetic field.

Top scientists have warned that an area hit by an atomic missile of massive power would be engulfed in a suffocating fire storm which would persist for a long time.

International Atomic Time ( TAI, from the French name Temps atomique international ) is a high-precision atomic coordinate time standard based on the notional passage of proper time on Earth's geoid.

The latter is not to be confused with TA ( NPL ), which denotes an independent atomic time scale, not synchronised to TAI or to anything else.

This time scale is expressed in the form of tables of differences UTC-UTC ( k ) ( equivalent to TAI-TAI ( k )) for each participating institution k. ( The same circular also gives tables of TAI-TA ( k ), for the various unsynchronised atomic time scales.

UTC is a discontinuous time scale composed from segments that are linear transformations of atomic time, the discontinuities being arranged so that UTC approximated UT2 until the end of 1971, and UT1 thereafter.

This was a compromise arrangement for a broadcast time scale: a linear transformation of the BIH's atomic time meant that the time scale was stable and internationally synchronised, while approximating UT1 means that tasks such as navigation which require a source of Universal Time continue to be well served by public time broadcasts.

It is instrumental for keeping time, in that UTC is basically the atomic time synchronized to Earth's rotation by means of exact observations.

" Ever since the time of my ancestor Ali, the first Imam, that is to say over a period of thirteen hundred years, it has always been the tradition of our family that each Imam chooses his successor at his absolute and unfettered discretion from amongst any of his descendants, whether they be sons or remote male issue and in these circumstances and in view of the fundamentally altered conditions in the world in very recent years due to the great changes which have taken place including the discoveries of atomic science, I am convinced that it is in the best interest of the Shia Muslim Ismailia Community that I should be succeeded by a young man who has been brought up and developed during recent years and in the midst of the new age and who brings a new outlook on life to his office as Imam.

The structure of the 70 nm core was determined in 1998 and was at the time the largest atomic structure to be solved.

The naming of various substances now known as elements precedes the atomic theory of matter, as names were given locally by various cultures to various minerals, metals, compounds, alloys, mixtures, and other materials, although at the time it was not known which chemicals were elements and which compounds.

This practice can lead to the controversial question of which research group actually discovered an element, a question that has delayed naming of elements with atomic number of 104 and higher for a considerable time.