Moon Festival Adalah

Physical characteristics

The Moon is a very slightly scalene ellipsoid due to tidal stretching, with its long axis displaced 30° from facing the Earth, due to gravitational anomalies from impact basins. Its shape is more elongated than current tidal forces can account for. This 'fossil bulge' indicates that the Moon solidified when it orbited at half its current distance to the Earth, and that it is now too cold for its shape to restore hydrostatic equilibrium at its current orbital distance.[66]

The Moon is by size and mass the fifth largest natural satellite of the Solar System, categorizable as one of its planetary-mass moons, making it a satellite planet under the geophysical definitions of the term.[17] It is smaller than Mercury and considerably larger than the largest dwarf planet of the Solar System, Pluto. While the minor-planet moon Charon of the Pluto-Charon system is larger relative to Pluto,[f][67] the Moon is the largest natural satellite of the Solar System relative to their primary planets.[g]

The Moon's diameter is about 3,500 km, more than a quarter of Earth's, with the face of the Moon comparable to the width of either Mainland Australia,[68] Europe or the Contiguous United States (which excludes Alaska, etc.).[69] The whole surface area of the Moon is about 38 million square kilometers, comparable to North and South America combined,[70] the combined American landmass having an area (excluding all islands) of 37.7 million square kilometers.[71]

The Moon's mass is 1/81 of Earth's,[72] being the second densest among the planetary moons, and having the second highest surface gravity, after Io, at 0.1654 g and an escape velocity of 2.38 km/s (8600 km/h; 5300 mph).

The Moon is a differentiated body that was initially in hydrostatic equilibrium but has since departed from this condition.[73] It has a geochemically distinct crust, mantle, and core. The Moon has a solid iron-rich inner core with a radius possibly as small as 240 kilometres (150 mi) and a fluid outer core primarily made of liquid iron with a radius of roughly 300 kilometres (190 mi). Around the core is a partially molten boundary layer with a radius of about 500 kilometres (310 mi).[74][75] This structure is thought to have developed through the fractional crystallization of a global magma ocean shortly after the Moon's formation 4.5 billion years ago.[76]

Crystallization of this magma ocean would have created a mafic mantle from the precipitation and sinking of the minerals olivine, clinopyroxene, and orthopyroxene; after about three-quarters of the magma ocean had crystallized, lower-density plagioclase minerals could form and float into a crust atop.[77] The final liquids to crystallize would have been initially sandwiched between the crust and mantle, with a high abundance of incompatible and heat-producing elements.[1] Consistent with this perspective, geochemical mapping made from orbit suggests a crust of mostly anorthosite.[16] The Moon rock samples of the flood lavas that erupted onto the surface from partial melting in the mantle confirm the mafic mantle composition, which is more iron-rich than that of Earth.[1] The crust is on average about 50 kilometres (31 mi) thick.[1]

The Moon is the second-densest satellite in the Solar System, after Io.[78] However, the inner core of the Moon is small, with a radius of about 350 kilometres (220 mi) or less,[1] around 20% of the radius of the Moon. Its composition is not well understood, but is probably metallic iron alloyed with a small amount of sulfur and nickel; analyzes of the Moon's time-variable rotation suggest that it is at least partly molten.[79] The pressure at the lunar core is estimated to be 5 GPa (49,000 atm).[80]

On average the Moon's surface gravity is 1.62 m/s2[4] (0.1654 g; 5.318 ft/s2), about half of the surface gravity of Mars and about a sixth of Earth's.

The Moon's gravitational field is not uniform. The details of the gravitational field have been measured through tracking the Doppler shift of radio signals emitted by orbiting spacecraft. The main lunar gravity features are mascons, large positive gravitational anomalies associated with some of the giant impact basins, partly caused by the dense mare basaltic lava flows that fill those basins.[83][84] The anomalies greatly influence the orbit of spacecraft about the Moon. There are some puzzles: lava flows by themselves cannot explain all of the gravitational signature, and some mascons exist that are not linked to mare volcanism.[85]

The Moon has an external magnetic field of less than 0.2 nanoteslas,[86] or less than one hundred thousandth that of Earth. The Moon does not have a global dipolar magnetic field and only has crustal magnetization likely acquired early in its history when a dynamo was still operating.[87][88] Early in its history, 4 billion years ago, its magnetic field strength was likely close to that of Earth today.[86] This early dynamo field apparently expired by about one billion years ago, after the lunar core had crystallized.[86] Theoretically, some of the remnant magnetization may originate from transient magnetic fields generated during large impacts through the expansion of plasma clouds. These clouds are generated during large impacts in an ambient magnetic field. This is supported by the location of the largest crustal magnetizations situated near the antipodes of the giant impact basins.[89]

The Moon has an atmosphere so tenuous as to be nearly vacuum, with a total mass of less than 10 tonnes (9.8 long tons; 11 short tons).[94] The surface pressure of this small mass is around 3 × 10−15 atm (0.3 nPa); it varies with the lunar day. Its sources include outgassing and sputtering, a product of the bombardment of lunar soil by solar wind ions.[16][95] Elements that have been detected include sodium and potassium, produced by sputtering (also found in the atmospheres of Mercury and Io); helium-4 and neon[96] from the solar wind; and argon-40, radon-222, and polonium-210, outgassed after their creation by radioactive decay within the crust and mantle.[97][98] The absence of such neutral species (atoms or molecules) as oxygen, nitrogen, carbon, hydrogen and magnesium, which are present in the regolith, is not understood.[97] Water vapor has been detected by Chandrayaan-1 and found to vary with latitude, with a maximum at ~60–70 degrees; it is possibly generated from the sublimation of water ice in the regolith.[99] These gases either return into the regolith because of the Moon's gravity or are lost to space, either through solar radiation pressure or, if they are ionized, by being swept away by the solar wind's magnetic field.[97]

Studies of Moon magma samples retrieved by the Apollo missions demonstrate that the Moon had once possessed a relatively thick atmosphere for a period of 70 million years between 3 and 4 billion years ago. This atmosphere, sourced from gases ejected from lunar volcanic eruptions, was twice the thickness of that of present-day Mars. The ancient lunar atmosphere was eventually stripped away by solar winds and dissipated into space.[62]

A permanent Moon dust cloud exists around the Moon, generated by small particles from comets. Estimates are 5 tons of comet particles strike the Moon's surface every 24 hours, resulting in the ejection of dust particles. The dust stays above the Moon approximately 10 minutes, taking 5 minutes to rise, and 5 minutes to fall. On average, 120 kilograms of dust are present above the Moon, rising up to 100 kilometers above the surface. Dust counts made by LADEE's Lunar Dust EXperiment (LDEX) found particle counts peaked during the Geminid, Quadrantid, Northern Taurid, and Omicron Centaurid meteor showers, when the Earth, and Moon pass through comet debris. The lunar dust cloud is asymmetric, being more dense near the boundary between the Moon's dayside and nightside.[100][101]

Ionizing radiation from cosmic rays, the Sun and the resulting neutron radiation[103] produce radiation levels on average of 1.369 millisieverts per day during lunar daytime,[14] which is about 2.6 times more than on the International Space Station with 0.53 millisieverts per day at about 400 km above Earth in orbit, 5–10 times more than during a trans-Atlantic flight, 200 times more than on Earth's surface.[104] For further comparison radiation on a flight to Mars is about 1.84 millisieverts per day and on Mars on average 0.64 millisieverts per day, with some locations on Mars possibly having levels as low as 0.342 millisieverts per day.[105][106]

The Moon's axial tilt with respect to the ecliptic is only 1.5427°,[8][107] much less than the 23.44° of Earth. Because of this small tilt, the Moon's solar illumination varies much less with season than on Earth and it allows for the existence of some peaks of eternal light at the Moon's north pole, at the rim of the crater Peary.

The surface is exposed to drastic temperature differences ranging from 120 °C to −171 °C depending on the solar irradiance. Because of the lack of atmosphere, temperatures of different areas vary particularly upon whether they are in sunlight or shadow,[108] making topographical details play a decisive role on local surface temperatures.[109] Parts of many craters, particularly the bottoms of many polar craters,[110] are permanently shadowed, these "craters of eternal darkness" have extremely low temperatures. The Lunar Reconnaissance Orbiter measured the lowest summer temperatures in craters at the southern pole at 35 K (−238 °C; −397 °F)[111] and just 26 K (−247 °C; −413 °F) close to the winter solstice in the north polar crater Hermite. This is the coldest temperature in the Solar System ever measured by a spacecraft, colder even than the surface of Pluto.[109]

Blanketed on top of the Moon's crust is a highly comminuted (broken into ever smaller particles) and impact gardened mostly gray surface layer called regolith, formed by impact processes. The finer regolith, the lunar soil of silicon dioxide glass, has a texture resembling snow and a scent resembling spent gunpowder.[112] The regolith of older surfaces is generally thicker than for younger surfaces: it varies in thickness from 10–15 m (33–49 ft) in the highlands and 4–5 m (13–16 ft) in the maria.[113] Beneath the finely comminuted regolith layer is the megaregolith, a layer of highly fractured bedrock many kilometers thick.[114]

These extreme conditions are considered to make it unlikely for spacecraft to harbor bacterial spores at the Moon for longer than just one lunar orbit.[115]

The topography of the Moon has been measured with laser altimetry and stereo image analysis.[116] Its most extensive topographic feature is the giant far-side South Pole–Aitken basin, some 2,240 km (1,390 mi) in diameter, the largest crater on the Moon and the second-largest confirmed impact crater in the Solar System.[117][118] At 13 km (8.1 mi) deep, its floor is the lowest point on the surface of the Moon.[117][119] The highest elevations of the Moon's surface are located directly to the northeast, which might have been thickened by the oblique formation impact of the South Pole–Aitken basin.[120] Other large impact basins such as Imbrium, Serenitatis, Crisium, Smythii, and Orientale possess regionally low elevations and elevated rims.[117] The far side of the lunar surface is on average about 1.9 km (1.2 mi) higher than that of the near side.[1]

The discovery of fault scarp cliffs suggest that the Moon has shrunk by about 90 metres (300 ft) within the past billion years.[121] Similar shrinkage features exist on Mercury. Mare Frigoris, a basin near the north pole long assumed to be geologically dead, has cracked and shifted. Since the Moon does not have tectonic plates, its tectonic activity is slow and cracks develop as it loses heat.[122]

Scientists have confirmed the presence of a cave on the Moon near the Sea of Tranquillity, not far from the 1969 Apollo 11 landing site. The cave, identified as an entry point to a collapsed lava tube, is roughly 45 meters wide and up to 80 m long. This discovery marks the first confirmed entry point to a lunar cave. The analysis was based on photos taken in 2010 by NASA's Lunar Reconnaissance Orbiter. The cave's stable temperature of around 17 °C could provide a hospitable environment for future astronauts, protecting them from extreme temperatures, solar radiation, and micrometeorites. However, challenges include accessibility and risks of avalanches and cave-ins. This discovery offers potential for future lunar bases or emergency shelters.[123]

The main features visible from Earth by the naked eye are dark and relatively featureless lunar plains called maria (singular mare; Latin for "seas", as they were once believed to be filled with water)[124] are vast solidified pools of ancient basaltic lava. Although similar to terrestrial basalts, lunar basalts have more iron and no minerals altered by water.[125] The majority of these lava deposits erupted or flowed into the depressions associated with impact basins, though the Moon's largest expanse of basalt flooding, Oceanus Procellarum, does not correspond to an obvious impact basin. Different episodes of lava flows in maria can often be recognized by variations in surface albedo and distinct flow margins.[126]

As the maria formed, cooling and contraction of the basaltic lava created wrinkle ridges in some areas. These low, sinuous ridges can extend for hundreds of kilometers and often outline buried structures within the mare. Another result of maria formation is the creation of concentric depressions along the edges, known as arcuate rilles. These features occur as the mare basalts sink inward under their own weight, causing the edges to fracture and separate.

In addition to the visible maria, the Moon has mare deposits covered by ejecta from impacts. Called cryptomares, these hidden mares are likely older than the exposed ones.[127] Conversely, mare lava has obscured many impact melt sheets and pools. Impact melts are formed when intense shock pressures from collisions vaporize and melt zones around the impact site. Where still exposed, impact melt can be distinguished from mare lava by its distribution, albedo, and texture.[128]

Sinuous rilles, found in and around maria, are likely extinct lava channels or collapsed lava tubes. They typically originate from volcanic vents, meandering and sometimes branching as they progress. The largest examples, such as Schroter's Valley and Rima Hadley, are significantly longer, wider, and deeper than terrestrial lava channels, sometimes featuring bends and sharp turns that again, are uncommon on Earth.

Mare volcanism has altered impact craters in various ways, including filling them to varying degrees, and raising and fracturing their floors from uplift of mare material beneath their interiors. Examples of such craters include Taruntius and Gassendi. Some craters, such as Hyginus, are of wholly volcanic origin, forming as calderas or collapse pits. Such craters are relatively rare, and tend to be smaller (typically a few kilometers wide), shallower, and more irregularly shaped than impact craters. They also lack the upturned rims characteristic of impact craters.

Several geologic provinces containing shield volcanoes and volcanic domes are found within the near side maria.[129] There are also some regions of pyroclastic deposits, scoria cones and non-basaltic domes made of particularly high viscosity lava.

Almost all maria are on the near side of the Moon, and cover 31% of the surface of the near side[72] compared with 2% of the far side.[130] This is likely due to a concentration of heat-producing elements under the crust on the near side, which would have caused the underlying mantle to heat up, partially melt, rise to the surface and erupt.[77][131][132] Most of the Moon's mare basalts erupted during the Imbrian period, 3.3–3.7 billion years ago, though some being as young as 1.2 billion years[63] and as old as 4.2 billion years.[64]

In 2006, a study of Ina, a tiny depression in Lacus Felicitatis, found jagged, relatively dust-free features that, because of the lack of erosion by infalling debris, appeared to be only 2 million years old.[133] Moonquakes and releases of gas indicate continued lunar activity.[133] Evidence of recent lunar volcanism has been identified at 70 irregular mare patches, some less than 50 million years old. This raises the possibility of a much warmer lunar mantle than previously believed, at least on the near side where the deep crust is substantially warmer because of the greater concentration of radioactive elements.[134][135][136][137] Evidence has been found for 2–10 million years old basaltic volcanism within the crater Lowell,[138][139] inside the Orientale basin. Some combination of an initially hotter mantle and local enrichment of heat-producing elements in the mantle could be responsible for prolonged activities on the far side in the Orientale basin.[140][141]

The lighter-colored regions of the Moon are called terrae, or more commonly highlands, because they are higher than most maria. They have been radiometrically dated to having formed 4.4 billion years ago, and may represent plagioclase cumulates of the lunar magma ocean.[63][64] In contrast to Earth, no major lunar mountains are believed to have formed as a result of tectonic events.[142]

The concentration of maria on the near side likely reflects the substantially thicker crust of the highlands of the Far Side, which may have formed in a slow-velocity impact of a second moon of Earth a few tens of millions of years after the Moon's formation.[143][144] Alternatively, it may be a consequence of asymmetrical tidal heating when the Moon was much closer to the Earth.[145]

A major geologic process that has affected the Moon's surface is impact cratering,[146] with craters formed when asteroids and comets collide with the lunar surface. There are estimated to be roughly 300,000 craters wider than 1 km (0.6 mi) on the Moon's near side.[147] Lunar craters exhibit a variety of forms, depending on their size. In order of increasing diameter, the basic types are simple craters with smooth bowl shaped interiors and upturned rims, complex craters with flat floors, terraced walls and central peaks, peak ring basins, and multi-ring basins with two or more concentric rings of peaks.[148] The vast majority of impact craters are circular, but some, like Cantor and Janssen, have more polygonal outlines, possibly guided by underlying faults and joints. Others, such as the Messier pair, Schiller, and Daniell, are elongated. Such elongation can result from highly oblique impacts, binary asteroid impacts, fragmentation of impactors before surface strike, or closely spaced secondary impacts.[149]

The lunar geologic timescale is based on the most prominent impact events, such as multi-ring formations like Nectaris, Imbrium, and Orientale that are between hundreds and thousands of kilometers in diameter and associated with a broad apron of ejecta deposits that form a regional stratigraphic horizon.[150] The lack of an atmosphere, weather, and recent geological processes mean that many of these craters are well-preserved. Although only a few multi-ring basins have been definitively dated, they are useful for assigning relative ages. Because impact craters accumulate at a nearly constant rate, counting the number of craters per unit area can be used to estimate the age of the surface.[150] However care needs to be exercised with the crater counting technique due to the potential presence of secondary craters. Ejecta from impacts can create secondary craters that often appear in clusters or chains, but can also occur as isolated formations at a considerable distance from the impact. These can resemble primary craters, and may even dominate small crater populations, so their unidentified presence can distort age estimates.[151]

The radiometric ages of impact-melted rocks collected during the Apollo missions cluster between 3.8 and 4.1 billion years old: this has been used to propose a Late Heavy Bombardment period of increased impacts.[152]

High-resolution images from the Lunar Reconnaissance Orbiter in the 2010s show a contemporary crater-production rate significantly higher than was previously estimated. A secondary cratering process caused by distal ejecta is thought to churn the top two centimeters of regolith on a timescale of 81,000 years.[153][154] This rate is 100 times faster than the rate computed from models based solely on direct micrometeorite impacts.[155]

Lunar swirls are enigmatic features found across the Moon's surface. They are characterized by a high albedo, appear optically immature (i.e. the optical characteristics of a relatively young regolith), and often have a sinuous shape. Their shape is often accentuated by low albedo regions that wind between the bright swirls. They are located in places with enhanced surface magnetic fields and many are located at the antipodal point of major impacts. Well known swirls include the Reiner Gamma feature and Mare Ingenii. They are hypothesized to be areas that have been partially shielded from the solar wind, resulting in slower space weathering.[156]

Liquid water cannot persist on the lunar surface. When exposed to solar radiation, water quickly decomposes through a process known as photodissociation and is lost to space. However, since the 1960s, scientists have hypothesized that water ice may be deposited by impacting comets or possibly produced by the reaction of oxygen-rich lunar rocks, and hydrogen from solar wind, leaving traces of water which could possibly persist in cold, permanently shadowed craters at either pole on the Moon.[157][158] Computer simulations suggest that up to 14,000 km2 (5,400 sq mi) of the surface may be in permanent shadow.[110] The presence of usable quantities of water on the Moon is an important factor in rendering lunar habitation as a cost-effective plan; the alternative of transporting water from Earth would be prohibitively expensive.[159]

In years since, signatures of water have been found to exist on the lunar surface.[160] In 1994, the bistatic radar experiment located on the Clementine spacecraft, indicated the existence of small, frozen pockets of water close to the surface. However, later radar observations by Arecibo, suggest these findings may rather be rocks ejected from young impact craters.[161] In 1998, the neutron spectrometer on the Lunar Prospector spacecraft showed that high concentrations of hydrogen are present in the first meter of depth in the regolith near the polar regions.[162] Volcanic lava beads, brought back to Earth aboard Apollo 15, showed small amounts of water in their interior.[163]

The 2008 Chandrayaan-1 spacecraft has since confirmed the existence of surface water ice, using the on-board Moon Mineralogy Mapper. The spectrometer observed absorption lines common to hydroxyl, in reflected sunlight, providing evidence of large quantities of water ice, on the lunar surface. The spacecraft showed that concentrations may possibly be as high as 1,000 ppm.[164] Using the mapper's reflectance spectra, indirect lighting of areas in shadow confirmed water ice within 20° latitude of both poles in 2018.[165] In 2009, LCROSS sent a 2,300 kg (5,100 lb) impactor into a permanently shadowed polar crater, and detected at least 100 kg (220 lb) of water in a plume of ejected material.[166][167] Another examination of the LCROSS data showed the amount of detected water to be closer to 155 ± 12 kg (342 ± 26 lb).[168]

In May 2011, 615–1410 ppm water in melt inclusions in lunar sample 74220 was reported,[169] the famous high-titanium "orange glass soil" of volcanic origin collected during the Apollo 17 mission in 1972. The inclusions were formed during explosive eruptions on the Moon approximately 3.7 billion years ago. This concentration is comparable with that of magma in Earth's upper mantle. Although of considerable selenological interest, this insight does not mean that water is easily available since the sample originated many kilometers below the surface, and the inclusions are so difficult to access that it took 39 years to find them with a state-of-the-art ion microprobe instrument.

Analysis of the findings of the Moon Mineralogy Mapper (M3) revealed in August 2018 for the first time "definitive evidence" for water-ice on the lunar surface.[170][171] The data revealed the distinct reflective signatures of water-ice, as opposed to dust and other reflective substances.[172] The ice deposits were found on the North and South poles, although it is more abundant in the South, where water is trapped in permanently shadowed craters and crevices, allowing it to persist as ice on the surface since they are shielded from the sun.[170][172]

In October 2020, astronomers reported detecting molecular water on the sunlit surface of the Moon by several independent spacecraft, including the Stratospheric Observatory for Infrared Astronomy (SOFIA).[173][174][175][176]

The Earth and the Moon form the Earth-Moon satellite system with a shared center of mass, or barycenter. This barycenter is 1,700 km (1,100 mi) (about a quarter of Earth's radius) beneath the Earth's surface.

The Moon's orbit is slightly elliptical, with an orbital eccentricity of 0.055.[1] The semi-major axis of the geocentric lunar orbit, called the lunar distance, is approximately 400,000 km (250,000 miles or 1.28 light-seconds), comparable to going around Earth 9.5 times.[177]

The Moon makes a complete orbit around Earth with respect to the fixed stars, its sidereal period, about once every 27.3 days.[h] However, because the Earth-Moon system moves at the same time in its orbit around the Sun, it takes slightly longer, 29.5 days,[i][72] to return at the same lunar phase, completing a full cycle, as seen from Earth. This synodic period or synodic month is commonly known as the lunar month and is equal to the length of the solar day on the Moon.[178]

Due to tidal locking, the Moon has a 1:1 spin–orbit resonance. This rotation–orbit ratio makes the Moon's orbital periods around Earth equal to its corresponding rotation periods. This is the reason for only one side of the Moon, its so-called near side, being visible from Earth. That said, while the movement of the Moon is in resonance, it still is not without nuances such as libration, resulting in slightly changing perspectives, making over time and location on Earth about 59% of the Moon's surface visible from Earth.[179]

Unlike most satellites of other planets, the Moon's orbital plane is closer to the ecliptic plane than to the planet's equatorial plane. The Moon's orbit is subtly perturbed by the Sun and Earth in many small, complex and interacting ways. For example, the plane of the Moon's orbit gradually rotates once every 18.61 years,[180] which affects other aspects of lunar motion. These follow-on effects are mathematically described by Cassini's laws.[181]

The gravitational attraction that Earth and the Moon (as well as the Sun) exert on each other manifests in a slightly greater attraction on the sides closest to each other, resulting in tidal forces. Ocean tides are the most widely experienced result of this, but tidal forces also considerably affect other mechanics of Earth, as well as the Moon and their system.

The lunar solid crust experiences tides of around 10 cm (4 in) amplitude over 27 days, with three components: a fixed one due to Earth, because they are in synchronous rotation, a variable tide due to orbital eccentricity and inclination, and a small varying component from the Sun.[182] The Earth-induced variable component arises from changing distance and libration, a result of the Moon's orbital eccentricity and inclination (if the Moon's orbit were perfectly circular and un-inclined, there would only be solar tides).[182] According to recent research, scientists suggest that the Moon's influence on the Earth may contribute to maintaining Earth's magnetic field.[183]

The cumulative effects of stress built up by these tidal forces produces moonquakes. Moonquakes are much less common and weaker than are earthquakes, although moonquakes can last for up to an hour – significantly longer than terrestrial quakes – because of scattering of the seismic vibrations in the dry fragmented upper crust. The existence of moonquakes was an unexpected discovery from seismometers placed on the Moon by Apollo astronauts from 1969 through 1972.[184]

The most commonly known effect of tidal forces are elevated sea levels called ocean tides.[185] While the Moon exerts most of the tidal forces, the Sun also exerts tidal forces and therefore contributes to the tides as much as 40% of the Moon's tidal force; producing in interplay the spring and neap tides.[185]

The tides are two bulges in the Earth's oceans, one on the side facing the Moon and the other on the side opposite. As the Earth rotates on its axis, one of the ocean bulges (high tide) is held in place "under" the Moon, while another such tide is opposite. The tide under the Moon is explained by the Moon's gravity being stronger on the water close to it. The tide on the opposite side can be explained either by the centrifugal force as the Earth orbits the barycenter or by the water's inertia as the Moon's gravity is stronger on the solid Earth close to it and it is pull away from the farther water.[186]

Thus, there are two high tides, and two low tides in about 24 hours.[185] Since the Moon is orbiting the Earth in the same direction of the Earth's rotation, the high tides occur about every 12 hours and 25 minutes; the 25 minutes is due to the Moon's time to orbit the Earth.

If the Earth were a water world (one with no continents) it would produce a tide of only one meter, and that tide would be very predictable, but the ocean tides are greatly modified by other effects:

As a result, the timing of the tides at most points on the Earth is a product of observations that are explained, incidentally, by theory.

Delays in the tidal peaks of both ocean and solid-body tides cause torque in opposition to the Earth's rotation. This "drains" angular momentum and rotational kinetic energy from Earth's rotation, slowing the Earth's rotation.[185][182] That angular momentum, lost from the Earth, is transferred to the Moon in a process known as tidal acceleration, which lifts the Moon into a higher orbit while lowering orbital speed around the Earth.

Thus the distance between Earth and Moon is increasing, and the Earth's rotation is slowing in reaction.[182] Measurements from laser reflectors left during the Apollo missions (lunar ranging experiments) have found that the Moon's distance increases by 38 mm (1.5 in) per year (roughly the rate at which human fingernails grow).[188][189][190] Atomic clocks show that Earth's day lengthens by about 17 microseconds every year,[191][192][193] slowly increasing the rate at which UTC is adjusted by leap seconds.

This tidal drag makes the rotation of the Earth and the orbital period of the Moon very slowly match. This matching first results in tidally locking the lighter body of the orbital system, as is already the case with the Moon. Theoretically, in 50 billion years,[194] the Earth's rotation will have slowed to the point of matching the Moon's orbital period, causing the Earth to always present the same side to the Moon. However, the Sun will become a red giant, most likely engulfing the Earth-Moon system long before then.[195][196]

If the Earth-Moon system isn't engulfed by the enlarged Sun, the drag from the solar atmosphere can cause the orbit of the Moon to decay. Once the orbit of the Moon closes to a distance of 18,470 km (11,480 mi), it will cross Earth's Roche limit, meaning that tidal interaction with Earth would break apart the Moon, turning it into a ring system. Most of the orbiting rings will begin to decay, and the debris will impact Earth. Hence, even if the Sun does not swallow up Earth, the planet may be left moonless.[197]

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Tema Jendela Gambar. Gambar tema oleh

ĐỒ CHƠI TRẺ DƯỚI 3 TUỔI

CÁC ĐÒ CHƠI KHÁC CHO BÉ GÁI

CÁC ĐỒ CHƠI KHÁC CHO BÉ TRAI

-- Perayaan Holi menjadi citra yang paling melekat dengan India di iklan-iklan, film, serta video musik. Masyarakat yang datang dari seluruh penjuru negeri bernyanyi, menari, dan menebarkan serbuk dan air berwarna pada kawan dan keluarga mereka.

Merek-merek terkenal seperti Sony dan Canon juga menggunakan festival ini untuk mengampanyekan produk mereka. Baru-baru ini British Airways juga ikut terlibat dengan awak pesawat merayakan festival itu di beberapa kota di India.

Bahkan Chris Martin dari grup musik Coldplay menggunakan tradisi Holi tersebut dalam video musik

, meski dalam prosesnya ia membuat kesal beberapa pihak.

SCROLL TO CONTINUE WITH CONTENT

Namun sebelum Anda turut terlibat dalam keriaan ini, Anda sebaiknya menjawab beberapa pertanyaan ini: Apa itu Holi? Dan mengapa orang India merayakannya?

Di beberapa tempat di India, festival Holi bisa berlangsung hingga satu pekan. (REUTERS/Rupak De Chowdhuri)

Holi adalah festival di agama Hindu yang menandakan dimulainya musim semi.

Dirayakan di seluruh India, festival ini telah berlangsung ratusan tahun dengan jejak pertama ditemukan pada puisi yang diciptakan di abad keempat.

Bahkan festival ini dicantumkan dalam naskah drama Sanskerta di abad ke-7 berjudul "Ratnavali", yang ditulis oleh kaisar India, Harsha.

"Saksikan keindahan festival cinta yang memantik rasa ingin tahu ketika para penduduk kota berdansa tersentuh percikan air berwarna coklat. Segalanya berwarna kuning kemerah-merahan dan menjadi tertutup oleh serbuk wangi yang ditiupkan ke seluruh penjuru," demikian ujar Harsha.

Meski pada mulanya adalah festival di agama Hindu, Holi dirayakan oleh seluruh penduduk India dan juga jadi perekat kebersamaan. Anak-anak bisa bermain air dengan orangtua, perempuan menebarkan serbuk warna pada pria, dan untuk sesaat sistem kasta dan sekat-sekat masyarakat jadi terlupakan.

Malamnya, penduduk India menghabiskan waktu bersama kawan dan keluarga.

Festival ini juga menjadi libur nasional yang biasanya bertepatan dengan hari terakhir purnama dalam kalender Hindu, yang sering kali jatuh pada Maret.

Pada tahun ini, libur nasional dirayakan pada Jumat, 2 Maret.

Festivalnya sendiri berlangsung sehari sebelumnya di Bengal Barat dan Odisha, sementara di daerah Uttar Pradesh bisa berjalan selama sepekan.

Ketika festival Holi berlangsung, penduduk India saling melemparkan serbuk dan air berwarna pada orang-orang terkasih. (Ahmad Masood)

Akar dari festival ini terletak pada legenda di agama Hindu yaitu Holika, setan perempuan yang juga saudari dari raja Hiranyakashayap.

Hiranyakashayap meyakini bahwa dia adalah penguasa dunia dan juga lebih tinggi dari dewa-dewa lain. Namun putranya, Prahlad, lebih memilih untuk mengikuti dewa Wishnu, pelindung alam semesta. Keputusan Prahlad mengkhianati ayahnya membuat Hiranyakashayap bersama Holika merencanakan pembunuhan Prahlad.

Rencana itu semula tampak tanpa celah; Holika akan membawa Prahlad dalam pangkuannya dan kemudian membawanya ke perapian. Holika sendiri tidak akan terluka karena ia membawa kain yang akan melindunginya dari jilat api.

Namun rencana itu gagal. Prahlad diselamatkan Wishnu dan Holika tewas karena kekebalannya pada api hanya berlaku jika dia sendirian.

Wishnu kemudian membunuh Hiranyakashayap dan Prahlad pun mengambil alih tampuk mahkota.

Pesan dari kisah ini adalah kebaikan selalu mengalahkan kejahatan.

Tradisi melemparkan serbuk berwarna diyakini bermula dari kisah cinta antara dewa Khrisna dan Radha.  (REUTERS/Adnan Abidi)

Di era modern, kremasi Holika direka ulang dengan menyalakan api unggul satu malam sebelum Holi digelar. Hari itu dikenal dengan nama Holika Dahan. Beberapa penganut agama Hindu kemudian mengumpulkan abu dan memaparkannya pada tubuh sebagai tanda penyucian.

Kemudian esok harinya berlangsung Rangwali Holi ketika sepanjang hari orang-orang melemparkan serbuk warna pada satu sama lain.

Tradisi melemparkan serbuk dan air berwarna ini diyakini bermula dari kisah cinta antara Krishna dan Radha.

Krishna, dewa pada agama Hindu yang digambarkan memiliki kulit berwarna biru gelap, diyakini pernah mengeluhkan kulit Radha yang berwarna terang pada ibunya.

Untuk meredakan kesedihan anaknya, ibu Krishna menyarankan ia mewarani kulit Radha dengan cat. Inilah awal mulanya kebiasaan memaparkan kulit orang-orang tercinta dengan serbuk warna di perayaan Holi.

Faisal Oddang writes fiction, poetry, and essays. Some of his books include Puya ke Puya, Manurung, Tiba Sebelum Berangkat, Sawerigading Datang dari Laut, and Raymond Carver Terkubur Mi Instan di Iowa. In addition to writing, Faisal also teaches at the Indonesian Literature Department of Universitas Hasanuddin and is actively involved with Kabisat Publishing. He was a curator for the 2022 & 2023 Makassar International Writers Festival and the Emerging Writers program of the 2024 Ubud Writers and Readers Festival. The awards and fellowships he has received include Kompas Best Short Story Writer in 2014 & 2018, 4th Winner of the Jakarta Arts Council Novel Competition in 2014, ASEAN Young Writers Award 2014 from the Thai Government, Tempo Art Figure in 2015, Robert Bosch Stiftung Literarisches Colloquium Berlin in 2018, and International Writing Program USA in 2018. He was also a finalist of Kusala Sastra Khatulistiwa 2018, a nominee for the Badan Bahasa Literary Award 2020, and the winner of the Sastrawan Muda Mastera award in 2023. As a writer, Faisal has been invited to various literary festivals and seminars, including the Iowa Book Festival 2018, London Book Fair 2019, Agor Drysau Festival 2019, Indonesian Cultural House Literary Meeting 2019, Ubud Writers and Readers Festival 2014, 2019, & 2023, Salihara International Literary Biennale 2015, Makassar International Writers Festival 2012-2023, Banggai Literary Festival 2018, Borobudur Writers and Cultural Festival 2018, and Rainy Day Literary Festival 2018.

Faisal Oddang menulis fiksi, puisi, dan esai. Beberapa bukunya antara lain Puya ke Puya, Manurung, Tiba Sebelum Berangkat, Sawerigading Datang dari Laut, dan Raymond Carver Terkubur Mi Instan di Iowa. Selain menulis, Faisal juga mengajar di Departemen Sastra Indonesia Universitas Hasanuddin, serta bergiat di Penerbit Kabisat. Ia merupakan kurator Makassar International Writers Festival 2022 & 2023, serta kurator Emerging Writers Ubud Writers and Readers Festival 2024. Penghargaan dan fellowship yang pernah ia terima mencakup Penulis Cerpen Terbaik Kompas 2014 & 2018, Pemenang IV Sayembara Novel Dewan Kesenian Jakarta 2014, Asean Young Writers Award 2014 dari Pemerintah Thailand, Tokoh Seni Tempo 2015, Robert Bosch Stiftung Literarisches Colloquium Berlin 2018, International Writing Program USA 2018, Finalis Kusala Sastra Khatulistiwa 2018, Nomine Penghargaan Sastra Badan Bahasa 2020, dan Sastrawan Muda Majelis Sastra Asia Tenggara 2023. Sebagai penulis, Faisal telah diundang di berbagai festival dan seminar sastra, antara lain Iowa Book Festival 2018, London Book Fair 2019, Agor Drysau Festival 2019, Temu Sastra Rumah Budaya Indonesia 2019, Ubud Writers and Readers Festival 2014, 2019, & 2023, Salihara International Literary Biennalle 2015, Makassar International Writers Festival 2012-2023, Festival Sastra Banggai 2018, Borobudur Writers and Cultural Festival 2018, dan Rainy Day Literary Festival 2018.

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Mid-Autumn Festival Stories

There are many legends about Mid-Autumn Festival. The most popular stories are about Chang'e and the Jade Rabbit.

Want to share the Mid-Autumn Festival story with your family? The 3-minute video below will show you all about it.

The origin of the Mid-Autumn Festival is associated with the popular legend of Chang'e (嫦娥), the goddess of the moon, and Hou Yi, the husband of Chang'e. He was rewarded with an elixir of immortality by the Queen Mother when he shot down nine of the ten suns and saved people from their smoldering heat. In Chinese folklore, he did not drink it straight away because he did not want to gain immortality without his wife. So, he asked Chang'e to keep it safe for him.

Unexpectedly one mid-autumn day, while Houyi was out hunting, an evil person tried to force Chang'e to hand over the elixir. Chang'e swallowed the elixir however and flew higher and higher. She then chose the moon as her immortal abode, to be close to her beloved husband and look down on him on Earth. Hou Yi was very sad and made sacrifices to Chang'e with incense, cakes, and fruits.

Legend has it that there is a rabbit companion with Chang'e on the moon, white as jade, so it is called 'jade rabbit'. As time passed, the jade rabbit became synonymous with the moon in Chinese culture.

The custom of worshiping the moon on Mid-Autumn day has been passed down from generation to generation.

Mid-Autumn Festival Greetings: Happy Mid-Autumn Festival!...

Mid-Autumn Festival is a time of good will. Many Chinese people send Mid-Autumn Festival cards or short messages during the festival to express their best wishes to family and friends.

The most popular greeting is "Happy Mid-Autumn Festival", in Chinese 中秋节快乐 — 'Zhongqiu Jie kuaile!'.

Other popular sayings are usually related to the moon or reunion. For example:

'Wishing us a long life to share the graceful moonlight, though hundreds of miles apart.' 但愿人长久，千里共婵娟 Dàn yuàn rén chángjiǔ, qiānlǐ gòng chánjuān

'Happy Mid-Autumn Festival! May the round moon bring you a happy family and a successful future.' 祝福中秋佳节快乐，月圆人圆事事圆满. Zhùfú Zhōngqiū jiā jié kuàilè, yuè yuán rén yuán shìshì yuánmǎn.

Check out more on Popular Chinese Mid-Autumn Festival Greetings/Wishes.

Natural satellite orbiting Earth

The Moon is Earth's only natural satellite. It orbits at an average distance of 384,400 km (238,900 mi), about 30 times the diameter of Earth. Tidal forces between Earth and the Moon have synchronized the Moon's orbital period (lunar month) with its rotation period (lunar day) at 29.5 Earth days, causing the same side of the Moon to always face Earth. The Moon's gravitational pull—and, to a lesser extent, the Sun's—are the main drivers of Earth's tides.

In geophysical terms, the Moon is a planetary-mass object or satellite planet. Its mass is 1.2% that of the Earth, and its diameter is 3,474 km (2,159 mi), roughly one-quarter of Earth's (about as wide as the United States from coast to coast). Within the Solar System, it is the largest and most massive satellite in relation to its parent planet, the fifth largest and most massive moon overall, and larger and more massive than all known dwarf planets.[17] Its surface gravity is about one sixth of Earth's, about half of that of Mars, and the second highest among all Solar System moons, after Jupiter's moon Io. The body of the Moon is differentiated and terrestrial, with no significant hydrosphere, atmosphere, or magnetic field. It formed 4.51 billion years ago, not long after Earth's formation, out of the debris from a giant impact between Earth and a hypothesized Mars-sized body called Theia.

The lunar surface is covered in lunar dust and marked by mountains, impact craters, their ejecta, ray-like streaks, rilles and, mostly on the near side of the Moon, by dark maria ("seas"), which are plains of cooled lava. These maria were formed when molten lava flowed into ancient impact basins. The Moon is, except when passing through Earth's shadow during a lunar eclipse, always illuminated by the Sun, but from Earth the visible illumination shifts during its orbit, producing the lunar phases.[18] The Moon is the brightest celestial object in Earth's night sky. This is mainly due to its large angular diameter, while the reflectance of the lunar surface is comparable to that of asphalt. The apparent size is nearly the same as that of the Sun, allowing it to cover the Sun completely during a total solar eclipse. From Earth about 59% of the lunar surface is visible over time due to cyclical shifts in perspective (libration), making parts of the far side of the Moon visible.

The Moon has been an important source of inspiration and knowledge for humans, having been crucial to cosmography, mythology, religion, art, time keeping, natural science, and spaceflight. The first human-made objects to fly to an extraterrestrial body were sent to the Moon, starting in 1959 with the flyby of the Soviet Union's Luna 1 and the intentional impact of Luna 2. In 1966, the first soft landing (by Luna 9) and orbital insertion (by Luna 10) followed. On July 20, 1969, humans for the first time stepped on an extraterrestrial body, landing on the Moon at Mare Tranquillitatis with the lander Eagle of the United States' Apollo 11 mission. Five more crews were sent between then and 1972, each with two men landing on the surface. The longest stay was 75 hours by the Apollo 17 crew. Since then, exploration of the Moon has continued robotically, and crewed missions are being planned to return beginning in the late 2020s.

The usual English proper name for Earth's natural satellite is simply Moon, with a capital M.[19][20] The noun moon is derived from Old English mōna, which (like all its Germanic cognates) stems from Proto-Germanic *mēnōn,[21] which in turn comes from Proto-Indo-European *mēnsis 'month'[22] (from earlier *mēnōt, genitive *mēneses) which may be related to the verb 'measure' (of time).[23]

Occasionally, the name Luna is used in scientific writing[24] and especially in science fiction to distinguish the Earth's moon from others, while in poetry "Luna" has been used to denote personification of the Moon.[25] Cynthia is another poetic name, though rare, for the Moon personified as a goddess,[26] while Selene (literally 'Moon') is the Greek goddess of the Moon.

The English adjective pertaining to the Moon is lunar, derived from the Latin word for the Moon, lūna. Selenian [27] is an adjective used to describe the Moon as a world, rather than as a celestial object,[28] but its use is rare. It is derived from σελήνη selēnē, the Greek word for the Moon, and its cognate selenic was originally a rare synonym[29] but now nearly always refers to the chemical element selenium.[30] The element name selenium and the prefix seleno- (as in selenography, the study of the physical features of the Moon) come from this Greek word.[31][32]

Artemis, the Greek goddess of the wilderness and the hunt, came to also be identified as the goddess of the Moon (Selene) and was sometimes called Cynthia, after her birthplace on Mount Cynthus.[33] Her Roman equivalent is Diana. The names Luna, Cynthia, and Selene are reflected in technical terms for lunar orbits such as apolune, pericynthion and selenocentric.

The astronomical symbol for the Moon is a crescent\decrescent, \, for example in M☾ 'lunar mass' (also ML).

Mid-Autumn Festival, Zhongqiu Jie (中秋节) in Chinese, is also called the Mooncake Festival or the Moon Festival.

As the second most important festival in China after Chinese New Year, Mid-Autumn is an official public holiday. In 2025, the festival falls on October 6th. People living in Mainland China will enjoy 1-day public holiday.

In China, Mid-Autumn Festival is a reunion time for families, a little like Thanksgiving. Chinese people celebrate it by gathering for dinners, worshiping the moon, lighting paper lanterns, eating moon cakes, etc.

It is also celebrated by many other countries, such as America (mainly in the Asian American community), Singapore, and Malaysia. The date is the same as in China, but there is no public holiday.

The Mid-Autumn Festival in America

The Mid-Autumn Festival is widely celebrated in the Asian American community. Asian Americans United (AAU) organizes a parade in Philadelphia around the Mid-Autumn Festival every year, including many activities, such as lion and dragon dancing, lantern decorations, Chinese operas, kung fu demonstrations, a mooncake-eating contest, and arts activities. This carnival attracts thousands of people who gather on the streets to participate in the activities.

In New York City, the Museum of Chinese in America holds mooncake-making sessions and drop-in arts and crafts to celebrate for an afternoon every year. In 2023, it will be free for everyone on September 30th. There will also be a full-moon-themed party with dance music and concerts on Saturday, September 23rd in Brooklyn.

Worshiping the Moon

According to the legend of Mid-Autumn Festival, a fairy maiden named Chang'e lives on the moon with a cute rabbit. On the night of the Mid-Autumn Festival, people set a table under the moon with mooncakes, snacks, fruits, and a pair of candles lit on it. Some believe that by worshiping the moon, Chang'e (the moon goddess) may fulfill their wishes.

Mooncake Festival in Singapore

People can enjoy the traditional Chinese lanterns on show in Chinatown, wander around Gardens by the Bay to enjoy its exhibition of Chinese lanterns, or watch a staged performance of the traditional story of Chang'e at the Singapore Botanic Gardens. See more information about Mooncake Festival in Singapore.

Is Mid-Autumn Festival a Public Holiday?

Mid-Autumn Festival is held on the 15th day of the 8th month of the Chinese calendar, which is in September or early October on the Gregorian calendar.

In the Chinese mainland, people usually have a three-day public holiday for Mid-Autumn Festival.

In Hong Kong and Macau, the day after the Mid-Autumn Festival is a public holiday rather than the festival date itself (unless that date falls on a Sunday, then Monday is also a holiday), because many celebration events are held at night.

In Singapore and Malaysia, the Mooncake Festival is not a public holiday officially. If you want to know more details about the date of Mid-Autumn Festival, click Mid-Autumn Festival 2025

How People Celebrate Mid-Autumn Festival

As the second most important festival in China, Mid-Autumn Festival (Zhongqiu Jie) is celebrated in many traditional ways. Here are some of the most popular traditional celebrations.