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Solstice Gallery
A solstice is the time when the Sun reaches its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around 20–22 June and 20–22 December. In many countries, the seasons of the year are defined by reference to the solstices and the equinoxes. The term ''solstice'' can also be used in a broader sense, as the day when this occurs. For locations not too close to the equator or the poles, the dates with the longest and shortest periods of daylight are the summer and winter solstices, respectively. Terms with no ambiguity as to which hemisphere is the context are "June solstice" and "December solstice", referring to the months in which they take place every year. Etymology The word ''solstice'' is derived from the Latin () and (), because at the solstices, the Sun's declination appears to "stand still"; that is, the seasonal movement of the Sun's daily path (as seen from Earth) pauses at a northern or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sun Path
Sun path, sometimes also called day arc, refers to the diurnal motion, daily (sunrise to sunset) and seasonal arc (geometry), arc-like path that the Sun appears to follow across the sky as the Earth Earth's rotation, rotates and Earth's orbit, orbits the Sun. The Sun's path affects the length of daytime experienced and amount of daylight received along a certain latitude during a given season. The relative position of the Sun is a major factor in the solar gain, heat gain of buildings and in the performance of solar energy systems. Accurate location-specific knowledge of sun path and climatic conditions is essential for economic decisions about solar thermal collector, solar collector area, orientation, landscaping, summer shading, and the cost-effective use of solar trackers. Angles Effect of the Earth's axial tilt Sun paths at any latitude and any time of the year can be determined from basic geometry. The Earth's axis of Earth's rotation, rotation tilts about Axial ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Summer Solstice
The summer solstice or estival solstice occurs when one of Earth's poles has its maximum tilt toward the Sun. It happens twice yearly, once in each hemisphere ( Northern and Southern). The summer solstice is the day with the longest period of daylight and shortest night of the year in that hemisphere, when the sun is at its highest position in the sky. At either pole there is continuous daylight at the time of its summer solstice. The opposite event is the winter solstice. The summer solstice occurs during the hemisphere's summer. In the Northern Hemisphere, this is the June solstice (20, 21 or 22 June) and in the Southern Hemisphere, this is the December solstice (20, 21, 22 or 23 of December). Since prehistory, the summer solstice has been a significant time of year in many cultures, and has been marked by festivals and rituals. Traditionally, in temperate regions (especially Europe), the summer solstice is seen as the middle of summer and referred to as midsum ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Celestial Navigation
Celestial navigation, also known as astronavigation, is the practice of position fixing using stars and other celestial bodies that enables a navigator to accurately determine their actual current physical position in space or on the surface of the Earth without relying solely on estimated positional calculations, commonly known as dead reckoning. Celestial navigation is performed without using satellite navigation or other similar modern electronic or digital positioning means. Celestial navigation uses "sights," or timed angular measurements, taken typically between a celestial body (e.g., the Sun, the Moon, a planet, or a star) and the visible horizon. Celestial navigation can also take advantage of measurements between celestial bodies without reference to the Earth's horizon, such as when the Moon and other selected bodies are used in the practice called "lunars" or the Lunar distance (navigation), lunar distance method, used for determining precise time when time is u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isaac Newton
Sir Isaac Newton () was an English polymath active as a mathematician, physicist, astronomer, alchemist, theologian, and author. Newton was a key figure in the Scientific Revolution and the Age of Enlightenment, Enlightenment that followed. His book (''Mathematical Principles of Natural Philosophy''), first published in 1687, achieved the Unification of theories in physics#Unification of gravity and astronomy, first great unification in physics and established classical mechanics. Newton also made seminal contributions to optics, and Leibniz–Newton calculus controversy, shares credit with German mathematician Gottfried Wilhelm Leibniz for formulating calculus, infinitesimal calculus, though he developed calculus years before Leibniz. Newton contributed to and refined the scientific method, and his work is considered the most influential in bringing forth modern science. In the , Newton formulated the Newton's laws of motion, laws of motion and Newton's law of universal g ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Absolute Space And Time
Absolute space and time is a concept in physics and philosophy about the properties of the universe. In physics, absolute space and time may be a preferred frame. Early concept A version of the concept of absolute space (in the sense of a preferred frame) can be seen in Aristotelian physics. Robert S. Westman writes that a "whiff" of absolute space can be observed in Copernicus's '' De revolutionibus orbium coelestium'', where Copernicus uses the concept of an immobile sphere of stars. Newton Originally introduced by Sir Isaac Newton in '' Philosophiæ Naturalis Principia Mathematica'', the concepts of absolute time and space provided a theoretical foundation that facilitated Newtonian mechanics. According to Newton, absolute time and space respectively are independent aspects of objective reality: Absolute, true and mathematical time, of itself, and from its own nature flows equably without regard to anything external, and by another name is called duration: relative, appar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Albert Einstein
Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence formula , which arises from special relativity, has been called "the world's most famous equation". He received the 1921 Nobel Prize in Physics for . Born in the German Empire, Einstein moved to Switzerland in 1895, forsaking his German citizenship (as a subject of the Kingdom of Württemberg) the following year. In 1897, at the age of seventeen, he enrolled in the mathematics and physics teaching diploma program at the Swiss ETH Zurich, federal polytechnic school in Zurich, graduating in 1900. He acquired Swiss citizenship a year later, which he kept for the rest of his life, and afterwards secured a permanent position at the Swiss Patent Office in Bern. In 1905, he submitted a successful PhD dissertation to the University of Zurich. In 19 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Principle Of Relativity
In physics, the principle of relativity is the requirement that the equations describing the laws of physics have the same form in all admissible frames of reference. For example, in the framework of special relativity, the Maxwell equations have the same form in all inertial frames of reference. In the framework of general relativity, the Maxwell equations or the Einstein field equations have the same form in arbitrary frames of reference. Several principles of relativity have been successfully applied throughout science, whether implicitly (as in Newtonian mechanics) or explicitly (as in Albert Einstein's special relativity and general relativity). Basic concepts Certain principles of relativity have been widely assumed in most scientific disciplines. One of the most widespread is the belief that any law of nature should be the same at all times; and scientific investigations generally assume that laws of nature are the same regardless of the person measuring them. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frame Of Reference
In physics and astronomy, a frame of reference (or reference frame) is an abstract coordinate system, whose origin (mathematics), origin, orientation (geometry), orientation, and scale (geometry), scale have been specified in physical space. It is based on a set of reference points, defined as point (geometry), geometric points whose position (geometry), position is identified both mathematically (with numerical coordinate values) and physically (signaled by conventional markers). An important special case is that of ''inertial reference frames'', a stationary or uniformly moving frame. For ''n'' dimensions, reference points are sufficient to fully define a reference frame. Using Cartesian coordinate system, rectangular Cartesian coordinates, a reference frame may be defined with a reference point at the origin and a reference point at one unit distance along each of the ''n'' coordinate Cartesian coordinate system, axes. In Theory of relativity, Einsteinian relativity, referen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Relative Velocity
The relative velocity of an object ''B'' relative to an observer ''A'', denoted \mathbf v_ (also \mathbf v_ or \mathbf v_), is the velocity vector of ''B'' measured in the rest frame of ''A''. The relative speed v_ = \, \mathbf v_\, is the vector norm of the relative velocity. Classical mechanics In one dimension (non-relativistic) We begin with relative motion in the classical, (or non- relativistic, or the Newtonian approximation) that all speeds are much less than the speed of light. This limit is associated with the Galilean transformation. The figure shows a man on top of a train, at the back edge. At 1:00 pm he begins to walk forward at a walking speed of 10 km/h (kilometers per hour). The train is moving at 40 km/h. The figure depicts the man and train at two different times: first, when the journey began, and also one hour later at 2:00 pm. The figure suggests that the man is 50 km from the starting point after having traveled (by walking and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Houghton Mifflin Harcourt
Houghton Mifflin Harcourt Company ( ; HMH) is an American publisher of textbooks, instructional technology materials, assessments, and reference works. The company is based in the Financial District, Boston, Boston Financial District. It was formerly known as the Houghton Mifflin Company, but it changed its name following the 2007 acquisition of Harcourt (publisher), Harcourt Publishing. Prior to March 2010, it was a subsidiary of EMPG, Education Media and Publishing Group Limited, an Irish-owned holding company registered in the Cayman Islands and formerly known as Riverdeep. In 2022, it was acquired by Veritas Capital, a New York-based private-equity firm. Company history In 1832, William Ticknor and John Allen purchased a bookselling business in Boston and began to involve themselves in publishing; James T. Fields joined as a partner in 1843. Fields and Ticknor gradually gathered an impressive list of writers, including Ralph Waldo Emerson, Nathaniel Hawthorne, and Henry Dav ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
The American Heritage Dictionary Of The English Language
''The American Heritage Dictionary of the English Language'' (''AHD'') is a dictionary of American English published by HarperCollins. It is currently in its fifth edition (since 2011). Before HarperCollins acquired certain business lines from Houghton Mifflin Harcourt in 2022, the family of American Heritage dictionaries had long been published by Houghton Mifflin Harcourt and its predecessor Houghton Mifflin. The first edition appeared in 1969, an outgrowth of the editorial effort for Houghton Mifflin's ''American Heritage'' brand of history books and journals. The dictionary's creation was spurred by the controversy during the 1960s over the perceived permissiveness of the ''Webster's Third New International Dictionary'' (1961). A college dictionary followed several years later. The main dictionary became the flagship title as the brand grew into a family of various dictionaries, a dictionary-thesaurus combination, and a usage (language), usage guide. History James Parton ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Natural History (Pliny)
The ''Natural History'' () is a Latin work by Pliny the Elder. The largest single work to have survived from the Roman Empire to the modern day, the ''Natural History'' compiles information gleaned from other ancient authors. Despite the work's title, its subject area is not limited to what is today understood by natural history; Pliny himself defines his scope as "the natural world, or life". It is encyclopedic in scope, but its structure is not like that of a modern encyclopedia. It is the only work by Pliny to have survived, and the last that he published. He published the first 10 books in AD 77, but had not made a final revision of the remainder at the time of Pliny the Elder#Death, his death during the Eruption of Mount Vesuvius in 79 AD, AD 79 eruption of Vesuvius. The rest was published posthumously by Pliny's nephew, Pliny the Younger. The work is divided into 37 books, organised into 10 volumes. These cover topics including astronomy, mathematics, geography, ethn ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
