What, When, Where, How, Who?
Month
Introduction, Important Definitions and Related Concepts:
The month is a unit of time, used with calendars, which is approximately as long as some natural period related to the motion of the Moon; month and Moon are cognates. The traditional concept arose with the cycle of moon phases; such months (lunations) are synodic months and last approximately 29.53 days. From excavated tally sticks, researchers have deduced that people counted days in relation to the Moon's phases as early as the Paleolithic age. Synodic months are still the basis of many calendars today. The motion of the Moon in its orbit is very complicated and its period is not constant. Moreover, many cultures (most notably those using the ancient Hebrew (Jewish) calendar and the Islamic calendar) start a month with the first appearance of the thin crescent of the new moon after sunset over the western horizon. The date and time of this actual observation depends on the exact geographical longitude as well as latitude, atmospheric conditions, the visual acuity of the observers, etc. Therefore the beginning and lengths of months in these calendars can not be accurately predicted. Most Jews currently follow a precalculated calendar, but the Karaites rely on actual moon observations. The period of the Moon's orbit as defined with respect to the celestial sphere is known as a sidereal month because it is the time it takes the Moon to return to a given position among the stars (Latin: sidus): 27.321661 days (27 d 7 h 43 min 11.5 s). This type of month has been observed among cultures in the Middle East, India, and China in the following way: they divided the sky into 27 or 28 lunar mansions, defined by asterisms (apparent groups of stars), one for each day of the sidereal month. Time is a basic component of the measuring system used to sequence events, to compare the durations of events and the intervals between them, and to quantify the motions of objects. Time has been a major subject of religion, philosophy, and science, but defining time in a non-controversial manner applicable to all fields of study has consistently eluded the greatest scholars. In physics and other sciences, time is considered one of the few fundamental quantities.[2] Time is used to define other quantites – such as velocity – and defining time in terms of such quantities would result in circularity of definition.[3] An operational definition of time, wherein one says that observing a certain number of repetitions of one or another standard cyclical event (such as the passage of a free-swinging pendulum) constitutes one standard unit such as the second, has a high utility value in the conduct of both advanced experiments and everyday affairs of life. The operational definition leaves aside the question whether there is something called time, apart from the counting activity just mentioned, that flows and that can be measured. Investigations of a single continuum called space-time brings the nature of time into association with related questions into the nature of space, questions that have their roots in the works of early students of natural philosophy. Among philosophers, there are two distinct viewpoints on time. One view is that time is part of the fundamental structure of the universe, a dimension in which events occur in sequence. Sir Isaac Newton subscribed to this realist view, and hence it is sometimes referred to as Newtonian time.[4][5] The opposing view is that time does not refer to any kind of "container" that events and objects "move through", nor to any entity that "flows", but that it is instead part of a fundamental intellectual structure (together with space and number) within which humans sequence and compare events. This second view, in the tradition of Gottfried Leibniz[6] and Immanuel Kant,[7][8] holds that time is not itself some thing and therefore is not to be measured.
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27 28 29 30 31
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24 25 26 27 28 29
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11 12 13 14 15 16 17
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27 28 29 30 31
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10 11 12 13 14 15 16
17 18 19 20 21 22 23
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The orbital period is the time taken for a given object to make one complete orbit about another object.
When mentioned without further qualification in astronomy this refers to the sidereal period of an astronomical object, which is calculated with respect to the stars. There are several kinds of orbital periods for objects around the Sun: The sidereal period is the time that it takes the object to make one full orbit around the Sun, relative to the stars. This is considered to be an object's true orbital period. The synodic period is the time that it takes for the object to reappear at the same point in the sky, relative to the Sun, as observed from Earth; i.e. returns to the same elongation (and planetary phase). This is the time that elapses between two successive conjunctions with the Sun and is the object's Earth-apparent orbital period. The synodic period differs from the sidereal period since Earth itself revolves around the Sun. The draconitic period is the time that elapses between two passages of the object at its ascending node, the point of its orbit where it crosses the ecliptic from the southern to the northern hemisphere. It differs from the sidereal period because the object's line of nodes typically precesses or recesses slowly. The anomalistic period is the time that elapses between two passages of the object at its perihelion, the point of its closest approach to the Sun. It differs from the sidereal period because the object's semimajor axis typically precesses or recesses slowly. The tropical period, finally, is the time that elapses between two passages of the object at right ascension zero. It is slightly shorter than the sidereal period because the vernal point precesses. The Moon (Latin: Luna) is Earth's only natural satellite and the fifth largest natural satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is 384,403 km, about thirty times the diameter of the Earth. The Moon's diameter is 3,474 km,[6] a little more than a quarter that of the Earth. This means that the Moon's volume is about 2 percent that of Earth and the pull of gravity at its surface about 17 percent that of the Earth. The Moon makes a complete orbit around the Earth every 27.3 days, and the periodic variations in the geometry of the Earth–Moon–Sun system are responsible for the lunar phases that repeat every 29.5 days. The Moon is the only celestial body to which humans have travelled and upon which humans have landed. The first artificial object to escape Earth's gravity and pass near the Moon was the Soviet Union's Luna 1, the first artificial object to impact the lunar surface was Luna 2, and the first photographs of the normally occluded far side of the Moon were made by Luna 3, all in 1959. The first spacecraft to perform a successful lunar soft landing was Luna 9, and the first unmanned vehicle to orbit the Moon was Luna 10, both in 1966.[6] The United States (U.S.) Apollo program achieved the only manned missions to date, resulting in six landings between 1969 and 1972. Human exploration of the Moon ceased with the conclusion of the Apollo program, although several countries have announced plans to send people or robotic spacecraft to the Moon. Unlike the moons of other planets, the moon of the Earth has no proper English name other than "the Moon" (capitalized[7]). A phase is one point or portion in a recurring series of changes. Phase or phases may also refer to:
[edit]In science and engineering
-
Phase (matter), a physically distinctive form of
a substance, such as the solid, liquid, and gaseous
states of ordinary matter
Phase (systems), in a complex system, a
behaviour that emerges from the interactions of
components at a small scale The initial condition of
a cyclic phenomenon
- Phase (waves), initial angle of a sinusoid function at its origin Continuous Fourier transform, angle of a complex coefficient representing the phase of one sinusoidal component
- Lunar phase, the appearance of the Moon as viewed from the Earth Planetary phase, the appearance of the illuminated section of a planet Instantaneous phase, generalization for both cyclic and non-cyclic phenomena
- Single-phase electric power Three-phase electric power Basics of three-phase electric power Three-phase Mathematics of three-phase electric power
[edit]In fiction
- "Phases" (Buffy episode), an episode of the TV series Buffy the Vampire Slayer Phases (.hack), fictional boss monsters from the .hack franchise Phase, an incarnation of the DC Comics character usually known as Phantom Girl Phase IV, a 1974 science fiction movie directed by Saul Bass
[edit]Other
- Phase (syntax), a syntactic domain hypothesized by Noam Chomsky Phase 10, a card game created by Fundex Games Phase (game), a music game for the iPod developed by Harmonix Music Systems
[edit]See also
-
Faze
Phaser
Phasor
FASOR. The two different ways to measure a month
are called sidereal and synodic.
The siderial month is the time it takes for the Moon to complete one full orbit of the Earth, measured with respect to the distant stars. The major assumption in determing a sidereal month is that the distant stars are fixed relative to Earth, and for the most part they are stationary. The sidereal month is the Moon's true orbital period and is equal to 27.3 days. That is, it takes the Moon 27.3 days to be in the same position relative to the distant stars. The synodic month is the time it takes for the Moon to complete one cycle of phases. For example, it is the time it takes the Moon to complete one full cycle of phases. That is, the time between successive new moons. Therefore the synodic month is measured with respect to the Sun and is approximately 29.5 days. Why is there a difference between the sidereal and synodic periods? Well, the Earth keeps orbiting the Sun while the Moon is going through its phases. A day (symbol: d) is a unit of time equivalent to 24 hours. It is not an SI unit but it is accepted for use with SI.[1] The SI unit of time is the second. The term comes from the Old English dæg. The day has several definitions.
[edit]International System of Units (SI) A day contains 86,400 SI seconds.[1] Each 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.
In the 19th century it had also been suggested to make a decimal fraction (1⁄10,000 or 1⁄100,000) of an astronomic day the base unit of time. This was an afterglow of the decimal time used with the French Republican Calendar, which had already been given up.
[edit]Astronomy A day of exactly 86,400 SI seconds is the fundamental unit of time in astronomy.
For a given planet, there are two types of day defined in astronomy: 1 apparent sidereal day
- The period of light when the Sun is above the
local
horizon (i.e., the period from sunrise to
sunset), opposed to
night. See
Daytime (astronomy). The full day covering a
dark and a light period, beginning from the
beginning of the dark period or from a point near
the middle of the dark period. A full dark and light
period, sometimes called a
nychthemeron in
English, from the
Greek for night-day. The period from
06:00 to 18:00 or 21:00 or some other fixed clock
period overlapping or set off from other periods
such as "morning", "evening", or "night". The mostly
regular interval of one awaking, usually in the
morning (personal day).
= a single rotation of a planet with respect to the distant stars (for Earth it is 23.934 solar hours)
[edit]Colloquial The word refers to various relatedly defined ideas, including the following: