In astronomy, a syzygy is a straight-line configuration of three or more celestial bodies in a gravitational system. The word is used in reference to the Sun and either the Moon or a planet, where the latter is in conjunction or opposition. Solar and lunar eclipses occur at times of syzygy, as do occultations; the term is applied when the Sun and Moon are in conjunction or opposition. The word syzygy is used to describe interesting configurations of astronomical objects in general. For example, one such case occurred on March 21, 1894, around 23:00 GMT, when Mercury transited the Sun as would have been seen from Venus, Mercury and Venus both transited the Sun as seen from Saturn, it is used to describe situations when all the planets are on the same side of the Sun although they are not in a straight line, such as on March 10, 1982. On June 3, 2014, the Curiosity rover on Mars observed the planet Mercury transiting the Sun, marking the first time a planetary transit has been observed from a celestial body besides Earth.
Syzygy sometimes results in transit, or eclipse. An occultation occurs when an larger body passes in front of an smaller one. A transit occurs. In the combined case where the smaller body transits the larger, an occultation is termed a secondary eclipse. An eclipse occurs when a body or disappears from view, either by an occultation, as with a solar eclipse, or by passing into the shadow of another body, as with a lunar eclipse. Transits and occultations of the Sun by Earth's Moon are called solar eclipses regardless of whether the Sun is or covered. By extension, transits of the Sun by a satellite of a planet may be called eclipses, as with the transits of Phobos and Deimos shown on NASA's JPL photojournal, as may the passage of a satellite into the planet's shadow, as with this eclipse of Phobos; the term eclipse is used more for bodies passing in front of one another. For example, a NASA Astronomy Picture of the Day refers to the Moon eclipsing and occulting Saturn interchangeably; as electromagnetic rays are somewhat bent by gravitation, when they pass by a heavy mass they are bent.
Thus, the heavy mass acts as a form of gravitational lens. If the light source, the diffracting mass and the observer stand in a line, one sees what is termed as an Einstein ring. Syzygy causes the bimonthly phenomena of neap tides. At the new and full moon, the Sun and Moon are in syzygy, their tidal forces act to reinforce each other, the ocean both rises higher and falls lower than the average. Conversely, at the first and third quarter, the Sun and Moon are at right angles, their tidal forces counteract each other, the tidal range is smaller than average. Tidal variation can be measured in the earth's crust, this may affect the frequency of earthquakes
In law, common law is that body of law derived from judicial decisions of courts and similar tribunals. The defining characteristic of "common law" is. In cases where the parties disagree on what the law is, a common law court looks to past precedential decisions of relevant courts, synthesizes the principles of those past cases as applicable to the current facts. If a similar dispute has been resolved in the past, the court is bound to follow the reasoning used in the prior decision. If, the court finds that the current dispute is fundamentally distinct from all previous cases, legislative statutes are either silent or ambiguous on the question, judges have the authority and duty to resolve the issue; the court states an opinion that gives reasons for the decision, those reasons agglomerate with past decisions as precedent to bind future judges and litigants. Common law, as the body of law made by judges, stands in contrast to and on equal footing with statutes which are adopted through the legislative process, regulations which are promulgated by the executive branch.
Stare decisis, the principle that cases should be decided according to consistent principled rules so that similar facts will yield similar results, lies at the heart of all common law systems. The common law—so named because it was "common" to all the king's courts across England—originated in the practices of the courts of the English kings in the centuries following the Norman Conquest in 1066; the British Empire spread the English legal system to its historical colonies, many of which retain the common law system today. These "common law systems" are legal systems that give great precedential weight to common law, to the style of reasoning inherited from the English legal system. Today, one-third of the world's population lives in common law jurisdictions or in systems mixed with civil law, including Antigua and Barbuda, Bahamas, Barbados, Botswana, Cameroon, Cyprus, Fiji, Grenada, Hong Kong, Ireland, Jamaica, Liberia, Malta, Marshall Islands, Namibia, New Zealand, Pakistan, Papua New Guinea, Sierra Leone, South Africa, Sri Lanka and Tobago, the United Kingdom, the United States, Zimbabwe.
Some of these countries have variants on common law systems. The term common law has many connotations; the first three set out here are the most-common usages within the legal community. Other connotations from past centuries are sometimes seen and are sometimes heard in everyday speech; the first definition of "common law" given in Black's Law Dictionary, 10th edition, 2014, is "The body of law derived from judicial decisions, rather than from statutes or constitutions. This usage is given as the first definition in modern legal dictionaries, is characterized as the “most common” usage among legal professionals, is the usage seen in decisions of courts. In this connotation, "common law" distinguishes the authority. For example, the law in most Anglo-American jurisdictions includes "statutory law" enacted by a legislature, "regulatory law" or “delegated legislation” promulgated by executive branch agencies pursuant to delegation of rule-making authority from the legislature, common law or "case law", i.e. decisions issued by courts.
This first connotation can be further differentiated into pure common law arising from the traditional and inherent authority of courts to define what the law is in the absence of an underlying statute or regulation. Examples include most criminal law and procedural law before the 20th century, today, most contract law and the law of torts. Interstitial common law court decisions that analyze and determine the fine boundaries and distinctions in law promulgated by other bodies; this body of common law, sometimes called "interstitial common law", includes judicial interpretation of the Constitution, of legislative statutes, of agency regulations, the application of law to specific facts. Publication of decisions, indexing, is essential to the development of common law, thus governments and private publishers publish law reports. While all decisions in common law jurisdictions are precedent, some become "leading cases" or "landmark decisions" that are cited often. Black's Law Dictionary 10th Ed. definition 2, differentiates "common law" jurisdictions and legal systems from "civil law" or "code" jurisdictions.
Common law systems place great weight on court decisions, which are considered "law" with the same force of law as statutes—for nearly a millennium, common law courts have had the authority to make law where no legislative statute exists, statutes mean what courts interpret them to mean. By contrast, in civil law jurisdictions, courts lack authority to act. Civil law judges tend to give less weight to judicial precedent, which means that a
A supermoon is a full moon or a new moon that nearly coincides with perigee—the closest that the Moon comes to the Earth in its elliptic orbit—resulting in a larger-than-usual apparent size of the lunar disk as viewed from Earth. The technical name is a full Moon around perigee; the term supermoon has no precise astronomical definition. The real association of the Moon with both oceanic and crustal tides has led to claims that the supermoon phenomenon may be associated with increased risk of events like earthquakes and volcanic eruptions, but no such link has been found; the opposite phenomenon, an apogee syzygy or a full Moon around apogee, has been called a micromoon. The name supermoon was coined by astrologer Richard Nolle in 1979, in Dell Horoscope magazine arbitrarily defined as:... a new or full moon which occurs with the Moon at or near its closest approach to Earth in a given orbit. In short, Earth and Sun are all in a line, with Moon in its nearest approach to Earth, he came up with the name while reading “Strategic Role Of Perigean Spring Tides in Nautical History and Coastal Flooding” published in 1976 by NOAA Hydrologist Fergus Wood.
Nolle never outlined why he chose 90%, but explained in 2011 that he based calculations on 90% of the difference in lunar apsis extremes for the solar year. In other words, a full or new moon is considered a supermoon if l d s ≤ l d p + 0.1 ∗ where l d s is the lunar distance at syzygy, l d a is the lunar distance at apogee, l d p is the lunar distance at perigee. In practice, there is no official or consistent definition of how near perigee the full Moon must occur to receive the supermoon label, new moons receive a supermoon label. Sky and Telescope magazine refers to full Moon which comes within 223,000 miles, TimeandDate.com prefers a definition of 360,000 kilometres. EarthSky uses Nolle's definition comparing their calculations to tables published by Nolle in 2000; the term perigee-syzygy or perigee full/new moon is preferred in the scientific community. Perigee is the point at which the Moon is closest in its orbit to the Earth, syzygy is when the Earth, the Moon and the Sun are aligned, which happens at every full or new moon.
Astrophysicist Fred Espenak uses Nolle's definition but preferring the label of full Moon at perigee. Wood used the definition of a full or new moon occurring within 24 hours of perigee and used the label perigee-syzygy. Wood coined the less used term proxigee where perigee and the full or new moon are separated by 10 hours or less. Of the possible 12 or 13 full moons each year three or four may be classified as supermoons, as defined; the most recent full supermoon occurred on February 19, 2019, the next one will be on March 21, 2019. The one on November 14, 2016 was the closest full supermoon since January 26, 1948, will not be surpassed until November 25, 2034; the closest full supermoon of the 21st century will occur on December 6, 2052. The oscillating nature of the distance to the full or new moon is due to the difference between the synodic and anomalistic months; the period of this oscillation is about 14 synodic months, close to 15 anomalistic months. A supermoon coincides with a total lunar eclipse.
The most recent occurrence of this was in January 2019, the next will be in May 2021. A full moon at perigee appears 14% larger in diameter than at apogee. Many observers insist; this is due to observations shortly after sunset when the moon is near the horizon and the moon illusion is at its most apparent. While the moon's surface luminance remains the same, because it is closer to the earth the illuminance is about 30% brighter than at its farthest point, or apogee; this is due to the inverse square law of light which changes the amount of light received on earth in inverse proportion to the distance from the moon. While a typical summer full moon at temperate latitudes provides only about 0.05-0.1 lux, a supermoon directly overhead in the tropics could provide up to 0.36 lux. Claims that supermoons can cause natural disasters, the claim of Nolle that supermoons cause "geophysical stress", have been refuted by scientists. Despite lack of scientific evidence, there has been media speculation that natural disasters, such as the 2011 Tōhoku earthquake and tsunami and the 2004 Indian Ocean earthquake and tsunami, are causally linked with the 1–2 week period surrounding a supermoon.
A large, 7.5 magnitude earthquake centred 15 km north-east of Culverden, New Zealand at 00:03 NZDT on November 14, 2016 coincided with a supermoon. Scientists have confirmed that the combined effect of the Sun and Moon on the Earth's oceans, the tide, is greatest when the Moon is either new or full, and that during lunar perigee, the tidal force is somewhat stronger, resulting in perigean spring tides. However at its most powerful, this force is still weak, causing tidal differences of inches at most. Total lunar eclipses which fall on supermoon and micromoon days are rare. In 21st century, there are 87 total lunar eclipses, of which 28 are supermoons and 6 are micromoons. All total lunar eclipses in Lunar Saros 129 are micromoon eclipses. Apsis Moon illu
In astronomy, a conjunction occurs when two astronomical objects or spacecraft have either the same right ascension or the same ecliptic longitude as observed from Earth. The astronomical symbol for conjunction is handwritten; the conjunction symbol is not used in modern astronomy. It continues to be used in astrology; when two objects always appear close to the ecliptic—such as two planets, the Moon and a planet, or the Sun and a planet—this fact implies an apparent close approach between the objects as seen on the sky. A related word, appulse, is the minimum apparent separation on the sky of two astronomical objects. Conjunctions involve either two objects in the Solar System or one object in the Solar System and a more distant object, such as a star. A conjunction is an apparent phenomenon caused by the observer's perspective: the two objects involved are not close to one another in space. Conjunctions between two bright objects close to the ecliptic, such as two bright planets, can be seen with the naked eye.
More in the particular case of two planets, it means that they have the same right ascension. This is called conjunction in right ascension. However, there is the term conjunction in ecliptic longitude. At such conjunction both objects have the same ecliptic longitude. Conjunction in right ascension and conjunction in ecliptic longitude do not take place at the same time, but in most cases nearly at the same time. However, at triple conjunctions, it is possible. At the time of conjunction – it does not matter if in right ascension or in ecliptic longitude – the involved planets are close together upon the celestial sphere. In the vast majority of such cases, one of the planets will appear to pass north or south of the other. However, if two celestial bodies attain the same declination at the time of a conjunction in right ascension, the one, closer to the Earth will pass in front of the other. In such a case, a syzygy takes place. If one object moves into the shadow of another, the event is an eclipse.
For example, if the Moon passes into the shadow of Earth and disappears from view, this event is called a lunar eclipse. If the visible disk of the nearer object is smaller than that of the farther object, the event is called a transit; when Mercury passes in front of the Sun, it is a transit of Mercury, when Venus passes in front of the Sun, it is a transit of Venus. When the nearer object appears larger than the farther one, it will obscure its smaller companion. An example of an occultation is when the Moon passes between Earth and the Sun, causing the Sun to disappear either or partially; this phenomenon is known as a solar eclipse. Occultations in which the larger body is neither the Sun nor the Moon are rare. More frequent, however, is an occultation of a planet by the Moon. Several such events are visible every year from various places on Earth. A conjunction, as a phenomenon of perspective, is an event that involves two astronomical bodies seen by an observer on the Earth. Times and details depend only slightly on the observer's location on the Earth's surface, with the differences being greatest for conjunctions involving the Moon because of its relative closeness, but for the Moon the time of a conjunction never differs by more than a few hours.
As seen from a planet, superior, if an inferior planet is on the opposite side of the Sun, it is in superior conjunction with the Sun. An inferior conjunction occurs. In an inferior conjunction, the superior planet is "in opposition" to the Sun as seen from the inferior planet; the terms "inferior conjunction" and "superior conjunction" are used in particular for the planets Mercury and Venus, which are inferior planets as seen from the Earth. However, this definition can be applied to any pair of planets, as seen from the one farther from the Sun. A planet is said to be in conjunction, when it is in conjunction with the Sun, as seen from the Earth; the Moon is in conjunction with the Sun at New Moon. In a quasiconjunction, a planet in retrograde motion — always either Mercury or Venus, from the point of view of the Earth — will "drop back" in right ascension until it allows another planet to overtake it, but the former planet will resume its forward motion and thereafter appear to draw away from it again.
This will occur before dawn. The reverse may happen in the evening sky after dusk, with Mercury or Venus entering retrograde motion just as it is about to overtake another planet; the quasiconjunction is reckoned as occurring at the time the distance in right ascension between the two planets is smallest though, when declination is taken into account, they may appear closer together shortly before or after this. In early December 1899 the Sun and the naked-eye planets appeared to lie within a band 35 degrees wide along the ecliptic as seen from the Earth; as a consequence, over the period 1–4 December 1899, the Moon reached conjunction with, in order, Uranus, the Sun, Mars and Venus. Most of these conjunctions were not visible because of the glare of the Sun. Over the period 4–6 February 1962, in a rare series of events and Venus reached conjunction as observed from the Earth, followed by Venus and Jupiter by Mars and Saturn. Conjunctions took
In astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the unaided eye, except when silhouetted during a solar eclipse. Daylight outshines the earthlight; the actual phase is a thin crescent. The original meaning of the term new moon, still sometimes used in non-astronomical contexts, was the first visible crescent of the Moon, after conjunction with the Sun; this crescent moon is visible when low above the western horizon shortly after sunset and before moonset. A lunation or synodic month is the average time from one new moon to the next. In the J2000.0 epoch, the average length of a lunation is 29.530588 days. However, the length of any one synodic month can vary from 29.26 to 29.80 days due to the perturbing effects of the Sun's gravity on the Moon's eccentric orbit. In a lunar calendar, each month corresponds to a lunation; each lunar cycle can be assigned a unique lunation number to identify it.
The length of a lunation is about 29.53 days. Its precise duration is linked to many phenomena in nature, such as the variation between spring and neap tides. An approximate formula to compute the mean moments of new moon for successive months is: d = 5.597661 + 29.5305888610 × N + × N 2 where N is an integer, starting with 0 for the first new moon in the year 2000, and, incremented by 1 for each successive synodic month. To obtain this moment expressed in Universal Time, add the result of following approximate correction to the result d obtained above: − 0.000739 − × N 2 daysPeriodic perturbations change the time of true conjunction from these mean values. For all new moons between 1601 and 2401, the maximum difference is 0.592 days = 14h13m in either direction. The duration of a lunation varies in this period between 29.272 and 29.833 days, i.e. −0.259d = 6h12m shorter, or +0.302d = 7h15m longer than average. This range is smaller than the difference between mean and true conjunction, because during one lunation the periodic terms cannot all change to their maximum opposite value.
See the article on the full moon cycle for a simple method to compute the moment of new moon more accurately. The long-term error of the formula is approximately: 1 cy2 seconds in TT, 11 cy2 seconds in UT The moment of mean conjunction can be computed from an expression for the mean ecliptical longitude of the Moon minus the mean ecliptical longitude of the Sun. Jean Meeus gave formulae to compute this in his Astronomical Formulae for Calculators based on the ephemerides of Brown and Newcomb; these are now outdated: Chapront et al. published improved parameters. Meeus's formula uses a fractional variable to allow computation of the four main phases, uses a second variable for the secular terms. For the convenience of the reader, the formula given above is based on Chapront's latest parameters and expressed with a single integer variable, the following additional terms have been added: constant term: Like Meeus, apply the constant terms of the aberration of light for the Sun's motion and light-time correction for the Moon to obtain the apparent difference in ecliptical longitudes:Sun: +20.496" Moon: −0.704" Correction in conjunction: −0.000451 daysFor UT: at 1 January 2000, ΔT was +63.83 s.
The term includes a tidal contribution of 0.5×. The most current estimate from Lunar Laser Ranging for the acceleration is:"/cy2. Therefore, the new quadratic term of D is = -6.8498"T2. Indeed, the polynomial provided by Chapront et alii provides the same value; this translates to a correction of +14.622×10−12N2 days to the time of conjunction. For UT: analysis of historical observations shows that ΔT has a long-term increase of +31 s/cy2. Converted to days and lunations, the correction from ET to UT becomes:−235×10−12N2 days; the theoretical tidal contribution to ΔT is about +42 s/cy2 the smaller observed value is thought to be due to changes in the shape of the Earth. Because the discrepancy is not explained, uncertainty of our prediction of UT may be as large as the difference between these values: 11 s/cy2; the error in the position of the Moon itself is only maybe 0.5"/cy2, or (because the apparent mean angular velocit
The full moon is the lunar phase when the Moon appears illuminated from Earth's perspective. This occurs when Earth is located between the Moon; this means that the lunar hemisphere facing Earth – the near side – is sunlit and appears as a circular disk, while the far side is dark. The full moon occurs once every month; when the Moon moves into Earth's shadow, a lunar eclipse occurs, during which all or part of the Moon's face may appear reddish due to the Rayleigh scattering of blue wavelengths and the refraction of sunlight through Earth's atmosphere. Lunar eclipses happen only during full moon and around points on its orbit where the satellite may pass through the planet's shadow. A lunar eclipse does not occur every month because the Moon's orbit is inclined 5.14° with respect to the ecliptic plane of Earth. Lunar eclipses happen only. Therefore, a lunar eclipse occurs every 6 months and 2 weeks before or after a solar eclipse, which occurs during new moon around the opposite node; the interval period between a new or full moon and the next same phase, a synodic month, averages about 29.53 days.
Therefore, in those lunar calendars in which each month begins on the day of the new moon, the full moon falls on either the 14th or 15th day of the lunar month. Because a calendar month consists of a whole number of days, a lunar month may be either 29 or 30 days long. A full moon is thought of as an event of a full night's duration; this is somewhat misleading because its phase seen from Earth continuously wanes. Its maximum illumination occurs at the moment waxing. For any given location, about half of these maximum full moons may be visible, while the other half occurs during the day, when the full moon is below the horizon. Many almanacs list full moons not only by date, but by their exact time in Coordinated Universal Time. Typical monthly calendars that include lunar phases may be offset by one day when used in a different time zone. Full moon is a suboptimal time for astronomical observation of the Moon because shadows vanish, it is a poor time for other observations because the bright sunlight reflected by the Moon, amplified by the opposition surge outshines many stars.
On 12 December 2008, the full moon occurred closer to the Earth than it had been at any time for the previous 15 years, called a supermoon. On 19 March 2011, another full supermoon occurred, closer to the Earth than at any time for the previous 18 years. On 14 November 2016, a full supermoon occurred closer to the Earth than at any time for the previous 68 years; the date and approximate time of a specific full moon can be calculated from the following equation: d = 20.362000 + 29.530588861 × N + 102.026 × 10 − 12 × N 2 where d is the number of days since 1 January 2000 00:00:00 in the Terrestrial Time scale used in astronomical ephemerides. The true time of a full moon may differ from this approximation by up to about 14.5 hours as a result of the non-circularity of the moon's orbit. See New moon for an explanation of the formula and its parameters; the age and apparent size of the full moon vary in a cycle of just under 14 synodic months, referred to as a full moon cycle. Full moons are traditionally associated with temporal insomnia and various "magical phenomena" such as lycanthropy.
Psychologists, have found that there is no strong evidence for effects on human behavior around the time of a full moon. They find that studies are not consistent, with some showing a positive effect and others showing a negative effect. In one instance, the 23 December 2000 issue of the British Medical Journal published two studies on dog bite admission to hospitals in England and Australia; the study of the Bradford Royal Infirmary found that dog bites were twice as common during a full moon, whereas the study conducted by the public hospitals in Australia found that they were less likely. Month names are names of moons in lunisolar calendars. Since the introduction of the solar Julian calendar in the Roman Empire, the Gregorian calendar worldwide, people no longer perceive month names as "moon" names; the traditional Old English month names were equated with the names of the Julian calendar from an early time. Some full moons have developed new names in modern times, e.g. the blue moon, the names "harvest moon" and "hunter's moon" for the full moons of autumn.
Lunar eclipses only happen during a full moon and cast a reddish tint over the face of the moon. This has been called a blood moon in popular culture; the "harvest moon" and "hunter's moon" are traditional terms for the full moons occurri
In astrodynamics or celestial mechanics, an elliptic orbit or elliptical orbit is a Kepler orbit with an eccentricity of less than 1. In a stricter sense, it is a Kepler orbit with the eccentricity greater than 0 and less than 1. In a wider sense, it is a Kepler orbit with negative energy; this includes the radial elliptic orbit, with eccentricity equal to 1. In a gravitational two-body problem with negative energy, both bodies follow similar elliptic orbits with the same orbital period around their common barycenter; the relative position of one body with respect to the other follows an elliptic orbit. Examples of elliptic orbits include: Hohmann transfer orbit, Molniya orbit, tundra orbit. Under standard assumptions the orbital speed of a body traveling along an elliptic orbit can be computed from the vis-viva equation as: v = μ where: μ is the standard gravitational parameter, r is the distance between the orbiting bodies. A is the length of the semi-major axis; the velocity equation for a hyperbolic trajectory has either + 1 a, or it is the same with the convention that in that case a is negative.
Under standard assumptions the orbital period of a body traveling along an elliptic orbit can be computed as: T = 2 π a 3 μ where: μ is the standard gravitational parameter, a is the length of the semi-major axis. Conclusions: The orbital period is equal to that for a circular orbit with the orbital radius equal to the semi-major axis, For a given semi-major axis the orbital period does not depend on the eccentricity. Under standard assumptions, specific orbital energy of elliptic orbit is negative and the orbital energy conservation equation for this orbit can take the form: v 2 2 − μ r = − μ 2 a = ϵ < 0 where: v is the orbital speed of the orbiting body, r is the distance of the orbiting body from the central body, a is the length of the semi-major axis, μ is the standard gravitational parameter. Conclusions: For a given semi-major axis the specific orbital energy is independent of the eccentricity. Using the virial theorem we find: the time-average of the specific potential energy is equal to −2ε the time-average of r−1 is a−1 the time-average of the specific kinetic energy is equal to ε It can be helpful to know the energy in terms of the semi major axis.
The total energy of the orbit is given by E = − G M m 2 a. Since gravity is a central force, the angular momentum is constant: L ˙ = r × F = r × F r ^ = 0 At the closest and furthest approaches, the angular momentum is perpendicular to the distance from the mass orbited, therefore: L = r p = r m v; the total energy of the orbit is given by E =. We may obtain E = 1 2 L 2 m r 2 − G M m r; this is true for r being the closest / furthest distance so we get two simultaneous equations which we solve for E: E = − G M m r 1 + r 2 Since r 1 = a + a ϵ and r 2 = a − a ϵ, where epsilon is the eccentricity of the orbit, we have the stated result. The flight path angle is the angle between the orbiting body's velocity vector and the local horizontal. Under standard assumptions of the conservation of a