|
Bureau International De L'Heure
The International Time Bureau (french: Bureau International de l'Heure, abbreviated BIH), seated at the Paris Observatory, was the international bureau responsible for combining different measurements of Universal Time. The bureau also played an important role in the research of time keeping and related fields: Earth rotation, reference frames, and atomic time. In 1987 the responsibilities of the bureau were taken over by the International Bureau of Weights and Measures (BIPM) and the International Earth Rotation and Reference Systems Service (IERS). History The creation of the BIH was decided upon during the 1912 ''Conférence internationale de l'heure radiotélégraphique''. The following year an attempt was made to regulate the international status of the bureau through the creation of an international convention. However, the convention wasn't ratified by its member countries due to the outbreak of World War I. In 1919, after the war, it was decided to make the bureau the execu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paris Observatory
The Paris Observatory (french: Observatoire de Paris ), a research institution of the Paris Sciences et Lettres University, is the foremost astronomical observatory of France, and one of the largest astronomical centers in the world. Its historic building is on the Left Bank of the Seine in central Paris, but most of the staff work on a satellite campus in Meudon, a suburb southwest of Paris. The Paris Observatory was founded in 1667. Construction was completed by the early 1670s and coincided with a major push for increased science, and the founding of the Royal Academy of Sciences. King Louis XIV's minister of finance organized a "scientific powerhouse" to increase understanding of astronomy, maritime navigation, and science in general. Through the centuries the Paris Observatory has continued in support of astronomical activities, and in the 21st century connects multiple sites and organizations, supporting astronomy and science, past and present. Constitution Administrat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Universal Time
Universal Time (UT or UT1) is a time standard based on Earth's rotation. While originally it was mean solar time at 0° longitude, precise measurements of the Sun are difficult. Therefore, UT1 is computed from a measure of the Earth's angle with respect to the International Celestial Reference Frame (ICRF), called the Earth Rotation Angle (ERA, which serves as a modern replacement for Greenwich Mean Sidereal Time). UT1 is the same everywhere on Earth. UT1 is required to follow the relationship :ERA = 2π(0.7790572732640 + 1.00273781191135448'' · Tu'') radians where ''Tu'' = ( Julian UT1 date - 2451545.0). History Prior to the introduction of standard time, each municipality throughout the clock-using world set its official clock, if it had one, according to the local position of the Sun (see solar time). This served adequately until the introduction of rail travel in Britain, which made it possible to travel fast enough over long distances to require continuous ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Time Keeping
Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to compare the duration of events or the intervals between them, and to quantify rates of change of quantities in material reality or in the conscious experience. Time is often referred to as a fourth dimension, along with three spatial dimensions. Time has long been an important subject of study in religion, philosophy, and science, but defining it in a manner applicable to all fields without circularity has consistently eluded scholars. Nevertheless, diverse fields such as business, industry, sports, the sciences, and the performing arts all incorporate some notion of time into their respective measuring systems. 108 pages. Time in physics is operationally defined as "what a clock reads". The physical nature of time is addressed ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Earth Rotation
Earth's rotation or Earth's spin is the rotation of planet Earth around its own axis, as well as changes in the orientation of the rotation axis in space. Earth rotates eastward, in prograde motion. As viewed from the northern polar star Polaris, Earth turns counterclockwise. The North Pole, also known as the Geographic North Pole or Terrestrial North Pole, is the point in the Northern Hemisphere where Earth's axis of rotation meets its surface. This point is distinct from Earth's North Magnetic Pole. The South Pole is the other point where Earth's axis of rotation intersects its surface, in Antarctica. Earth rotates once in about 24 hours with respect to the Sun, but once every 23 hours, 56 minutes and 4 seconds with respect to other distant stars ( see below). Earth's rotation is slowing slightly with time; thus, a day was shorter in the past. This is due to the tidal effects the Moon has on Earth's rotation. Atomic clocks show that a modern day is longer by about 1.7 milli ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
