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Topic Review
Transition of State
In quantum mechanics, particularly Perturbation theory, a transition of state is a change from an initial quantum state to a final one.
  • 302
  • 08 Nov 2022
Topic Review
Transit of Venus, 2012
The 2012 transit of Venus, when the planet Venus appeared as a small, dark spot passing across the face of the Sun, began at 22:09 UTC on 5 June 2012, and finished at 04:49 UTC on 6 June. Depending on the position of the observer, the exact times varied by up to ±7 minutes. Transits of Venus are among the rarest of predictable celestial phenomena and occur in pairs. Consecutive transits per pair are spaced 8 years apart, and consecutive pairs occur more than a century apart: The previous transit of Venus took place on 8 June 2004 (preceded by transits on 9 December 1874 and 6 December 1882); the next pair of transits will occur on 10–11 December 2117 and in December 2125.
  • 439
  • 28 Nov 2022
Topic Review
Transit of Venus, 1639
The first known observations and recording of a transit of Venus were made in 1639 by the English astronomers Jeremiah Horrocks and his friend and correspondent William Crabtree. The pair made their observations independently on 4 December that year (24 November under the Julian calendar then used in England); Horrocks from Carr House, then in the village of Much Hoole, Lancashire, and Crabtree from his home in Broughton, near Manchester. The friends, followers of the new astronomy of Johannes Kepler, were self-taught mathematical astronomers who had worked methodically to correct and improve Kepler's Rudolphine tables by observation and measurement. In 1639, Horrocks was the only astronomer to realise that a transit of Venus was imminent; others became aware of it only after the event when Horrocks's report of it was circulated. Although the friends both died within five years of making their observations, their ground-breaking work was influential in establishing the size of the Solar System; for this and their other achievements Horrocks and Crabtree, along with their correspondent William Gascoigne, are considered to be the founding fathers of British research astronomy.
  • 534
  • 06 Dec 2022
Topic Review
Transit
File:Moon transit of sun large.ogv In astronomy, a transit (or astronomical transit) is a phenomenon when a celestial body passes directly between a larger body and the observer. As viewed from a particular vantage point, the transiting body appears to move across the face of the larger body, covering a small portion of it. The word "transit" refers to cases where the nearer object appears smaller than the more distant object. Cases where the nearer object appears larger and completely hides the more distant object are known as occultations. However, the probability of seeing a transiting planet is low because it is dependent on the alignment of the three objects in a nearly perfectly straight line. Many parameters of a planet and its parent star can be determined based on the transit.
  • 1.2K
  • 02 Dec 2022
Topic Review
Transient Reactor Test Facility (TREAT)
Coordinates: 43°41′11″N 112°45′36″W / 43.68647°N 112.75998°W / 43.68647; -112.75998 Lua error in Module:Location_map at line 522: Unable to find the specified location map definition: "Module:Location map/data/Idaho" does not exist. The Transient Reactor Test Facility (TREAT) is an air-cooled, graphite moderated, thermal spectrum test nuclear reactor designed to test reactor fuels and structural materials. Constructed in 1958, and operated from 1959 until 1994, TREAT was built to conduct transient reactor tests where the test material is subjected to neutron pulses that can simulate conditions ranging from mild transients to reactor accidents. TREAT was designed by Argonne National Laboratory, and is located at the Idaho National Laboratory. Since original construction, the facility had additions or systems upgrades in 1963, 1972, 1982, and 1988. The 1988 addition was extensive, and included upgrades of most of the instrumentation and control systems. The U.S. Department of Energy (DOE) has decided to resume a program of transient testing, and plans to invest about $75 million to restart the TREAT facility by 2018. The renewed interest in TREAT was sparked by the 2011 Fukushima Daiichi nuclear disaster, which prompted the shutdown of Japan's and Germany's nuclear plants. One use for TREAT is planned to be testing of new accident tolerant fuel for nuclear reactors. TREAT was successfully restarted in November 2017.
  • 322
  • 13 Oct 2022
Topic Review
Transactinide Element
In chemistry, transactinide elements (also, transactinides, or super-heavy elements) are the chemical elements with atomic numbers from 104 to 120. Their atomic numbers are immediately greater than those of the actinides, the heaviest of which is lawrencium (atomic number 103). Glenn T. Seaborg first proposed the actinide concept, which led to the acceptance of the actinide series. He also proposed the transactinide series ranging from element 104 to 121 and the superactinide series approximately spanning elements 122 to 153. The transactinide seaborgium was named in his honor. By definition, transactinide elements are also transuranic elements, i.e. have an atomic number greater than uranium (92). The transactinide elements all have electrons in the 6d subshell in their ground state. Except for rutherfordium and dubnium, even the longest-lasting isotopes of transactinide elements have extremely short half-lives, measured in seconds, or smaller units. The element naming controversy involved the first five or six transactinide elements. These elements thus used systematic names for many years after their discovery had been confirmed. (Usually the systematic names are replaced with permanent names proposed by the discoverers relatively shortly after a discovery has been confirmed.) Transactinides are radioactive and have only been obtained synthetically in laboratories. None of these elements has ever been collected in a macroscopic sample. Transactinide elements are all named after physicists and chemists or important locations involved in the synthesis of the elements. IUPAC defines an element to exist if its lifetime is longer than 10−14 seconds, which is the time it takes for the nucleus to form an electron cloud.
  • 2.9K
  • 01 Dec 2022
Topic Review
Traditional Chinese Timekeeping
The traditional Chinese time systems refers to the time standards for divisions of the day used in China until the introduction of the Shixian calendar in 1628 at the beginning of the Qing dynasty.
  • 473
  • 30 Oct 2022
Topic Review
Traditional Chinese Star Names
Traditional Chinese star names (Chinese: 星名, xīng míng) are the names of stars used in ancient Chinese astronomy and astrology. Most of these names are enumerations within the respective Chinese constellations, but a few stars have traditional proper names.
  • 845
  • 29 Sep 2022
Topic Review
Topological and Dissipative Solitons in Liquid Crystals
Solitons are self-sustained localized packets of waves in nonlinear media that propagate without changing shape. They are found everywhere in our daily life from nerve pluses in our bodies to eyes of storms in the atmosphere and even density waves in galaxies. Solitons in liquid crystals have received increasing attention due to their importance in fundamental physical science and potential applications in various fields. 
  • 682
  • 21 Jan 2022
Topic Review
Tonti Diagram
The Tonti diagram, created by the Italian physicist and mathematician Enzo Tonti, is a diagram that classifies variables and equations of physical theories of classical and relativistic physics. The theories involved are: particle dynamics, analytical mechanics, mechanics of deformable solids, fluid mechanics, electromagnetism, gravitation, heat conduction, and irreversible thermodynamics. The classification stems from the observation that each physical variable has a well-defined association with a space and a time element, as shown in Fig. 1, which can be grasped from the corresponding global variable and from its measuring process.
  • 1.5K
  • 29 Sep 2022
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