Lateran Council, Second, 1139, 10th ecumenical council of the Roman Catholic Church, convened at the Lateran Palace, Rome, by Pope Innocent II. The council attempted to heal the wounds left by the schism of the antipope Anacletus II (d. 1138) and condemned the theories of Arnold of Brescia. Among the council's canons were prohibitions of clerical concubinage and marriage and of the use of bows and crossbows in fighting Christians; simony and usury were also condemned.
Vatican Council, Second, popularly called Vatican II, 1962-65, the 21st ecumenical council (see council, ecumenical) of the Roman Catholic Church, convened by Pope John XXIII and continued under Paul VI. Its announced purpose was spiritual renewal of the church and reconsideration of the position of the church in the modern world. The most spectacular innovation of the council, which convened Oct. 11, 1962, was the invitation extended to Protestant and Orthodox Eastern churches to send observers; the meetings were attended by representatives from many of those churches. Another obvious feature was the diversity of national and cultural origins shown among those who attended from all over the world.

One of the announced aims of the conference was to consider reform of the liturgy, primarily to bring the layman into closer participation in the church services and therefore to encourage some diversity in language and practice. Great emphasis was also laid from the beginning upon the pastoral duties of the bishops, as distinguished from administrative duties. The procedure at the conference accorded with democratic practice, and there was lively debate between the "progressive" and "conservative" groups. By the time of its adjournment the council had issued four constitutions, nine decrees, and three declarations. The nature of these statements was conciliatory, avoiding rigid definitions and condemning anathemas.

Session II (Sept.-Dec., 1963) produced the Constitution on the Sacred Liturgy (permitting vernacularization of the liturgy and stressing greater lay participation in the ritual) and the decree on the media of social communication. Out of Session III (Sept.-Nov., 1964) came the Dogmatic Constitution on the Church (which espoused the principle of episcopal collegiality with the pope), the decrees on ecumenism and on the Eastern Catholic churches, and the proclamation of the Blessed Virgin Mary as the "Mother of the Church."

Pope Paul VI opened Session IV (Sept.-Dec., 1965) with the announcement that he was establishing an episcopal synod to assist the pope in governing the church. That final session issued the Dogmatic Constitution on Divine Revelation and the Pastoral Constitution on the Church in the Modern World; the decrees on the bishops' pastoral office, on the appropriate renewal of the religious life (i.e., the life of the religious orders), on education for the priesthood, on the ministry and life of priests, on the apostolate of the laity, and on the church's missionary activity; and declarations on Christian education, on religious freedom, and on the relationship of the church to non-Christian religions (which included an important passage condemning anti-Semitism and recognizing "the bond that spiritually ties the people of the New Covenant to Abraham's stock"). Even before the close of the council Pope Paul began to establish a series of commissions to implement the council's wide-ranging decisions.


See H. Küng, The Council, Reform, and Reunion (tr. 1962); H. Daniel-Rops, The Second Vatican Council (tr. 1962); D. C. Pawley, An Anglican View of the Vatican Council (1962, repr. 1973); W. M. Abbot, ed., Documents of Vatican II (1966); A. Gilbert, The Vatican Council and the Jews (1968); X. Rynne, Vatican Council II (1968); A. Flannery, ed., Vatican Council II: Constitutions, Decrees, Declarations (repr. 1996) and Vatican Council II: Conciliar and Post Conciliar Documents (2 vol., repr. 1996).

Sino-Japanese War, Second, 1937-45, conflict between Japanese and Chinese forces for control of the Chinese mainland. The war sapped the Nationalist government's strength while allowing the Communists to gain control over large areas through organization of guerrilla units. Thus, it was an important factor in the eventual Communist defeat of the Nationalist forces in 1949. In its early stage, the war was often called the China Incident.


Following the Manchurian Incident (Sept., 1931), the Japanese Kwantung army occupied Manchuria and established the puppet state of Manchukuo (Feb., 1932). Japan pressed China to recognize the independence of Manchukuo, suppress anti-Japanese activities, and form autonomous regional governments in N China. The Japanese were partially successful in 1933 and 1935 when they forced China to form two demilitarized autonomous zones bordering Manchuria.

Outbreak of War

Growing domestic opposition to the Nationalist government's policy of self-strengthening before counterattacking in N China and Manchuria led to the kidnapping of Chiang Kai-shek was kidnapped at Xi'an in Dec., 1936, by Chang Hsüeh-liang. Chiang was forced to agree to a united anti-Japanese front with the Communists as a condition for his release. The situation was tense, and in 1937 full war commenced. A clash (July, 1937) between soldiers of the Japanese garrison at Beijing and Chinese forces at the Marco Polo Bridge was the pretext for Japanese occupation at Beijing and Tianjin. Chiang Kai-shek refused to negotiate an end to hostilities on Japanese terms and placed crack troops outside the Japanese settlement at Shanghai. After a protracted struggle Shanghai and the national capital, Nanjing, fell to the Japanese. The Chinese broke the Huang He dikes (June, 1938) to slow the enemy advance. In late 1938, Hankou and Guangzhou were taken.

Japanese strategy was aimed at taking the cities, the roads, and the railroads, thereby gaining a net of control. Thus, although the Japanese by 1940 had swept over the eastern coastal area, guerrilla fighting still went on in the conquered regions. The Nationalist government, driven back to a temporary capital at Chongqing, struggled on with little help from outside. Chinese resources were inadequate, and the supplies sent over the Burma Road were far from sufficient. The Chinese cause continued to decline despite vast resistance and bloody fighting. Dubious of China's ability to sustain a protracted war, Wang Ching-wei broke with Chiang Kai-shek and established a collaborationist regime at Nanjing (1940).

World War II

The Japanese bombing of Pearl Harbor brought the United States into the war and merged the Sino-Japanese War into World War II as China declared war on Japan, Germany, and Italy. American and British loans and supplies, the establishment of military air bases in China, and the aid of an increasing number of U.S. and British advisers helped relieve China as Japan diverted armies elsewhere. Nevertheless, China's military position continued to deteriorate until Apr., 1945. In May the Chinese launched a successful offensive at Zhijiang (Chihkiang) that lasted until Japanese capitulation on Aug. 14. The Japanese troops in China formally surrendered Sept. 9, 1945. By the provisions of the Cairo Declaration, Manchuria, Taiwan, and the Pescadores were restored to China.


See H. Feis, The China Tangle (1953); F. C. Jones, Japan's New Order in East Asia (1954); D. J. Lu, From the Marco Polo Bridge to Pearl Harbor (1961); J. H. Boyle, China and Japan at War, 1937-1945 (1972); L. Li, The Japanese Army in North China (1975).

second, abbr. sec or s, fundamental unit of time in all systems of measurement. In practical terms, the second is 1/60 of a minute, 1/3,600 of an hour, or 1/86,400 of a day. Since the length of the day varies, however, the second must be defined in more precise terms. For many years it was defined as 1/86,400 of the mean solar day (see solar time), thus eliminating seasonal variations. Because the rotation of the earth itself is not constant, the second was redefined (1956) in terms of ephemeris time (ET), which is calculated from the motions of celestial bodies in accordance with the laws of motion; 1 sec is 1/31,556,925.9747 of the length of the tropical year for 1900. In 1967 the second was redefined to be 9,192,631,770 periods of vibration of the radiation emitted at a specific wavelength by an atom of cesium-133.
The second (SI symbol: s), sometimes abbreviated sec., is the name of a unit of time, and is the International System of Units (SI) base unit of time. It may be measured using a clock.

SI prefixes are frequently combined with the word second to denote subdivisions of the second, e.g., the millisecond (one thousandth of a second) and nanosecond (one billionth of a second). Though SI prefixes may also be used to form multiples of the second (such as “kilosecond,” or one thousand seconds), such units are rarely used in practice. More commonly encountered, non-SI units of time such as the minute, hour, and day increase by multiples of 60 and 24 (rather than by powers of ten as in the SI system).

The second was also the base unit of time in the centimetre-gram-second, metre-kilogram-second, metre-tonne-second, and foot-pound-second systems of units.

International second

Under the International System of Units, the second is currently defined as
the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom.
This definition refers to a caesium atom at rest at a temperature of 0 K (absolute zero). The ground state is defined at zero magnetic field. The second thus defined is equivalent to the ephemeris second, which was based on astronomical measurements. (See History below.)

The international standard symbol for a second is s (see ISO 31-1)

The realization of the standard second is described briefly in NIST Special Publication 330; Appendix 2, pp. 53 ff, and in detail by National Research Council of Canada

Equivalence to other units of time

1 international second is equal to:


The Egyptians subdivided daytime and nighttime into twelve hours each since at least 2000 BC, hence their hours varied seasonally. The Hellenistic astronomers Hipparchus (c. 150 BC) and Ptolemy (c. AD 150) subdivided the day sexagesimally and also used a mean hour (day), but did not use distinctly named smaller units of time. Instead they used simple fractions of an hour.

The day was subdivided sexagesimally, that is by , by of that, by of that, etc., to at least six places after the sexagesimal point (a precision of less than 2 microseconds) by the Babylonians after 300 BC, but they did not sexagesimally subdivide smaller units of time. For example, six fractional sexagesimal places of a day was used in their specification of the length of the year, although they were unable to measure such a small fraction of a day in real time. As another example, they specified that the mean synodic month was 29;31,50,8,20 days (four fractional sexagesimal positions), which was repeated by Hipparchus and Ptolemy sexagesimally, and is currently the mean synodic month of the Hebrew calendar, though restated as 29 days 12 hours 793 halakim (where 1 hour = 1080 halakim). The Babylonians did not use the hour, but did use a double-hour, a time-degree lasting four of our minutes, and a barleycorn lasting 3⅓ of our seconds (the helek of the modern Hebrew calendar).

In 1000, the Muslim scholar al-Biruni gave the times of the new moons of specific weeks as a number of days, hours, minutes, seconds, thirds, and fourths after noon Sunday. In 1267, the medieval scientist Roger Bacon stated the times of full moons as a number of hours, minutes, seconds, thirds, and fourths (horae, minuta, secunda, tertia, and quarta) after noon on specified calendar dates. Although a third for of a second remains in some languages, for example Polish (tercja) and Arabic (ثالثة), the modern second is subdivided decimally.

The first attempt at creating a clock that could measure time in seconds was created by Taqi al-Din at the Istanbul observatory of al-Din between 1577-1580. He called it the "observational clock" in his In the Nabik Tree of the Extremity of Thoughts, where he described it as "a mechanical clock with three dials which show the hours, the minutes, and the seconds." He used it as an astronomical clock, particularly for measuring the right ascension of the stars.

The second first became accurately measurable with the development of pendulum clocks keeping mean time (as opposed to the apparent time displayed by sundials), specifically in 1670 when William Clement added a seconds pendulum to the original pendulum clock of Christian Huygens. The seconds pendulum has a period of two seconds, one second for a swing forward and one second for a swing back, enabling the longcase clock incorporating it to tick seconds. From this time, a second hand that rotated once per minute in a small subdial began to be added to the clock faces of precision clocks.

In 1956 the second was defined in terms of the period of revolution of the Earth around the Sun for a particular epoch, because by then it had become recognized that the Earth's rotation on its own axis was not sufficiently uniform as a standard of time. The Earth's motion was described in Newcomb's Tables of the Sun, which provides a formula for the motion of the Sun at the epoch 1900 based on astronomical observations made between 1750 and 1892. The second thus defined is

the fraction 1/31,556,925.9747 of the tropical year for 1900 January 0 at 12 hours ephemeris time.

This definition was ratified by the Eleventh General Conference on Weights and Measures in 1960. The tropical year in the definition was not measured, but calculated from a formula describing a mean tropical year which decreased linearly over time, hence the curious reference to a specific instantaneous tropical year. Because this second was the independent variable of time used in ephemerides of the Sun and Moon during most of the twentieth century (Newcomb's Tables of the Sun were used from 1900 through 1983, and Brown's Tables of the Moon were used from 1920 through 1983), it was called the ephemeris second.

With the development of the atomic clock, it was decided to use atomic clocks as the basis of the definition of the second, rather than the revolution of the Earth around the Sun.

Following several years of work, Louis Essen from the National Physical Laboratory (Teddington, England) and William Markowitz from the United States Naval Observatory (USNO) determined the relationship between the hyperfine transition frequency of the caesium atom and the ephemeris second. Using a common-view measurement method based on the received signals from radio station WWV, they determined the orbital motion of the Moon about the Earth, from which the apparent motion of the Sun could be inferred, in terms of time as measured by an atomic clock. As a result, in 1967 the Thirteenth General Conference on Weights and Measures defined the second of atomic time in the International System of Units as

the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium-133 atom.

During the 1970s it was realized that gravitational time dilation caused the second produced by each atomic clock to differ depending on its altitude. A uniform second was produced by correcting the output of each atomic clock to mean sea level (the rotating geoid), lengthening the second by about 1. This correction was applied at the beginning of 1977 and formalized in 1980. In relativistic terms, the SI second is defined as the proper time on the rotating geoid.

The definition of the second was later refined at the 1997 meeting of the BIPM to include the statement

This definition refers to a caesium atom at rest at a temperature of 0 K.

The revised definition would seem to imply that the ideal atomic clock would contain a single caesium atom at rest emitting a single frequency. In practice, however, the definition means that high-precision realizations of the second should compensate for the effects of the ambient temperature (black-body radiation) within which atomic clocks operate and extrapolate accordingly to the value of the second as defined above.

For approximately twenty years, it has been possible to confine an ion to a region of space smaller than one cubic micrometre (10-6 m)3. Such an ion is almost completely isolated from the surrounding environment and suggests a frequency or time standard with a reproducibility and stability several orders of magnitude superior to the best caesium time standards. Such standards are under development. See magneto-optical trap and Trapped ion optical frequency standards. National Physical Laboratory. .

SI multiples

SI prefixes are commonly used to measure time less than a second, but rarely for multiples of a second. Instead, the non-SI units minutes, hours, days, Julian years, Julian centuries, and Julian millennia are used.

See also


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