vania-janet/multiturn-rag-retrieval-data huggingface dataset:
Exoplanet
Tidally locked planets in a 1 : 1 spin -- orbit resonance would have their star always shining directly overhead on one spot which would be hot with the opposite hemisphere receiving no light and being freezing cold . Such a planet could resemble an eyeball with the hotspot being the pupil . Planets with an eccentric orbit could be locked in other resonances . 3 : 2 and 5 : 2 resonances would result in a double - eyeball pattern with hotspots in both eastern and western hemispheres . Planets with both an eccentric orbit and a tilted axis of rotation would have more complicated insolation patterns . See
Moon landing
On Ranger 3 , failure of the Atlas guidance system and a software error aboard the Agena upper stage combined to put the spacecraft on a course that would miss the Moon . Attempts to salvage lunar photography during a flyby of the Moon were thwarted by in - flight failure of the onboard flight computer . This was probably because of prior heat sterilization of the spacecraft by keeping it above the boiling point of water for 24 hours on the ground , to protect the Moon from being contaminated by Earth organisms . Heat sterilization was also blamed for subsequent in - flight failures of the spacecraft computer on Ranger 4 and the power subsystem on Ranger 5 . Only Ranger 4 reached the Moon in an uncontrolled crash impact on the far side of the Moon .
Lunar phase
Non-western cultures may use a different number of Moon phases , for example traditional Hawaiian culture has a total of 30 different Moon phases ( one per day ) .
Crater Lake
Lava eruptions later created a central platform , Wizard Island , Merriam Cone , and other , smaller volcanic features , including a rhyodacite dome that was eventually created atop the central platform . Sediments and landslide debris also covered the caldera floor .
Lunar eclipse
Unlike a solar eclipse , which can be viewed only from a certain relatively small area of the world , a lunar eclipse may be viewed from anywhere on the night side of the Earth . A lunar eclipse lasts for a few hours , whereas a total solar eclipse lasts for only a few minutes at any given place , due to the smaller size of the Moon 's shadow . Also unlike solar eclipses , lunar eclipses are safe to view without any eye protection or special precautions , as they are dimmer than the full moon .
Moon landing
Clickable map of the locations of all successful soft landings on the Moon to date ( top ) . Luna programme ( USSR ) Chang'e 3 ( China ) Surveyor program ( USA ) Apollo program ( USA ) Dates are landing dates in Coordinated Universal Time . Except for the Apollo program , all soft landings were unmanned . Luna 2 was the first man - made object to reach the surface of the Moon ( bottom - left ) . Still frame from a video transmission , taken moments before Neil Armstrong became the first human to step onto the surface of the Moon , at 02 : 56 UTC on 21 July 1969 . An estimated 500 million people worldwide watched this event , the largest television audience for a live broadcast at that time .
Sundial
A dial is said to be equiangular if its hour - lines are straight and spaced equally . Most equiangular sundials have a fixed gnomon style aligned with the Earth 's rotational axis , as well as a shadow - receiving surface that is symmetrical about that axis ; examples include the equatorial dial , the equatorial bow , the armillary sphere , the cylindrical dial and the conical dial . However , other designs are equiangular , such as the Lambert dial , a version of the analemmatic dial with a moveable style .
Sundial
This model of the Sun 's motion helps to understand sundials . If the shadow - casting gnomon is aligned with the celestial poles , its shadow will revolve at a constant rate , and this rotation will not change with the seasons . This is the most common design . In such cases , the same hour lines may be used throughout the year . The hour - lines will be spaced uniformly if the surface receiving the shadow is either perpendicular ( as in the equatorial sundial ) or circular about the gnomon ( as in the armillary sphere ) .
Moon landing
Scientists believe the six American flags planted by astronauts have been bleached white because of more than 40 years of exposure to solar radiation . Using LROC images , five of the six American flags are still standing and casting shadows at all of the sites , except Apollo 11 . Astronaut Buzz Aldrin reported that the flag was blown over by the exhaust from the ascent engine during liftoff of Apollo 11 .
Lunar eclipse
In some Chinese cultures , people would ring bells to prevent a dragon or other wild animals from biting the moon . In the nineteenth century , during a lunar eclipse , the Chinese navy fired its artillery because of this belief . During the Zhou Dynasty in the Book of Songs , the sight of a red moon engulfed in darkness was believed to foreshadow famine or disease .
Sundial
In the common vertical dial , the shadow - receiving plane is aligned vertically ; as usual , the gnomon 's style is aligned with the Earth 's axis of rotation . As in the horizontal dial , the line of shadow does not move uniformly on the face ; the sundial is not equiangular . If the face of the vertical dial points directly south , the angle of the hour - lines is instead described by the formula
Lunar distance (astronomy)
On May 23 , 2007 digital photographs of the Moon during a near - occultation of Regulus were taken from two locations , in Greece and England . By measuring the parallax between the moon and the chosen background star , the lunar distance was calculated .
Magnetosphere of Jupiter
Bright arcs and spots sporadically appear within the main ovals . These transient phenomena are thought to be related to interaction with the solar wind . The magnetic field lines in this region are believed to be open or to map onto the magnetotail . The secondary ovals observed inside the main oval may be related to the boundary between open and closed magnetic field lines or to the polar cusps . The polar auroral emissions are similar to those observed around Earth 's poles : both appear when electrons are accelerated towards the planet by potential drops , during reconnection of solar magnetic field with that of the planet . The regions within both main ovals emit most of auroral X-rays . The spectrum of the auroral X-ray radiation consists of spectral lines of highly ionized oxygen and sulfur , which probably appear when energetic ( hundreds of kiloelectronvolts ) S and O ions precipitate into the polar atmosphere of Jupiter . The source of this precipitation remains unknown .
Gerardus Mercator
Around this time Mercator also received and executed a very special order for the Emperor : a pair of small globes , the inner ( `` fist - size '' ) Earth was made of wood and the outer celestial sphere was made of blown crystal glass engraved with diamond and inlaid with gold . He presented them to the Emperor in Brussels who awarded him the title Imperatoris domesticus ( a member of the Imperial household ) . The globes are lost but Mercator describes them in a letter to Philip Melanchthon in which he declares that the globes were rotated on the top of an astronomical clock made for Charles V by Juanelo Turriano ( Janellus ) . The clock was provided with eight dials which showed the positions of the moon , stars and planets . The illustration shows a similar clock made by the German craftsman Baldewein at roughly the same time . Mercator
Lunar distance (astronomy)
A more ambitious project called the `` Aristarchus Campaign '' was conducted during the lunar eclipse of 15 April 2014 . During this event , participants were invited to record a series of 5 digital photographs from moonrise through culmination - the point of greatest altitude . The method took advantage of the fact that the Moon is actually closest to an observer when it is at its highest point in the sky , compared to when it is on the horizon . Although it appears that the Moon is biggest when it is near the horizon , the opposite is true . This phenomenon is known as the moon illusion . The reason for the change in distance results from the fact that the distance from the center of the Moon to the center of Earth is nearly constant throughout the night , but an observer on the surface of Earth is actually 1 Earth radius from the center of Earth . This offset brings them closest to the Moon when it is overhead .
Jupiter
Six years later , the Voyager missions vastly improved the understanding of the Galilean moons and discovered Jupiter 's rings . They also confirmed that the Great Red Spot was anticyclonic . Comparison of images showed that the Red Spot had changed hue since the Pioneer missions , turning from orange to dark brown . A torus of ionized atoms was discovered along Io 's orbital path , and volcanoes were found on the moon 's surface , some in the process of erupting . As the spacecraft passed behind the planet , it observed flashes of lightning in the night side atmosphere .
Lunar eclipse
When Christopher Columbus came to the New World -- specifically , the north coast of Jamaica -- he was able to use European scientific understanding to correctly predict a lunar eclipse . The event is known as the March 1504 lunar eclipse and occurred when Columbus , after he wanted to be seen as god - like , stated that he would make the moon disappear during the night of February 29 , 1504 . The reason Columbus wanted to prove he could make the moon disappear is because he and his crew were eating a great deal of the inhabitants ' food , and the inhabitants refused to feed them anymore . Columbus was right in his prediction , for he used astronomical tables and local clocks in order to predict when the lunar eclipse would happen and was able to convince the inhabitants that he had the power to make the moon disappear and then reappear . After the inhabitants believed that Columbus was truly able to make the moon disappear , they begged him to return the moon to its previous form , and after roughly an allotted amount of time ( the amount of time Columbus discerned to be how long the eclipse would last ) , Columbus agreed to return the moon , and the moon began to reappear . The next day , the inhabitants gave Columbus and his crew the food they desired .
Lunar eclipse
The ancient Mesopotamians believed that a lunar eclipse was when the moon was being attacked by seven demons . This attack was more than just one on the moon , however , for the Mesopotamians linked what happened in the sky with what happened on the land , and because the king of Mesopotamia represented the land , the seven demons were thought to be also attacking the king . In order to prevent this attack on the king , the Mesopotamians made someone pretend to be the king so they would be attacked instead of the true king . After the lunar eclipse was over , the substitute king was made to disappear ( possibly by poisoning ) .
Kuiper belt
During its period of migration , Neptune is thought to have captured a large KBO , Triton , which is the only large moon in the Solar System with a retrograde orbit ( it orbits opposite to Neptune 's rotation ) . This suggests that , unlike the large moons of Jupiter , Saturn and Uranus , which are thought to have coalesced from rotating discs of material around their young parent planets , Triton was a fully formed body that was captured from surrounding space . Gravitational capture of an object is not easy : it requires some mechanism to slow down the object enough to be caught by the larger object 's gravity . A possible explanation is that Triton was part of a binary when it encountered Neptune . ( Many KBOs are members of binaries . See below . ) Ejection of the other member of the binary by Neptune could then explain Triton 's capture . Triton is only 14 % larger than Pluto , and spectral analysis of both worlds shows that their surfaces are largely composed of similar materials , such as methane and carbon monoxide . All this points to the conclusion that Triton was once a KBO that was captured by Neptune during its outward migration .
Lunar distance (astronomy)
The instantaneous lunar distance is constantly changing . In fact the true distance between the Moon and Earth can change by as much as 7001750000000000000 ♠ 75 m / s , or more than 1,000 kilometers in just 6 hours , due to its non-circular orbit . There are other effects that also influence the lunar distance . Some factors are described in this section .
Venus
Venus may have formed from the solar nebula with a different rotation period and obliquity , reaching its current state because of chaotic spin changes caused by planetary perturbations and tidal effects on its dense atmosphere , a change that would have occurred over the course of billions of years . The rotation period of Venus may represent an equilibrium state between tidal locking to the Sun 's gravitation , which tends to slow rotation , and an atmospheric tide created by solar heating of the thick Venusian atmosphere . The 584 - day average interval between successive close approaches to Earth is almost exactly equal to 5 Venusian solar days , but the hypothesis of a spin -- orbit resonance with Earth has been discounted .
Reuleaux triangle
A Reuleaux triangle ( ʁœlo ) is a shape formed from the intersection of three circular disks , each having its center on the boundary of the other two . Its boundary is a curve of constant width , the simplest and best known such curve other than the circle itself . Constant width means that the separation of every two parallel supporting lines is the same , independent of their orientation . Because all its diameters are the same , the Reuleaux triangle is one answer to the question `` Other than a circle , what shape can a manhole cover be made so that it can not fall down through the hole ? ''
Sundial
In polar dials , the shadow - receiving plane is aligned parallel to the gnomon - style . Thus , the shadow slides sideways over the surface , moving perpendicularly to itself as the sun rotates about the style . As with the gnomon , the hour - lines are all aligned with the Earth 's rotational axis . When the sun 's rays are nearly parallel to the plane , the shadow moves very quickly and the hour lines are spaced far apart . The direct East - and West - facing dials are examples of a polar dial . However , the face of a polar dial need not be vertical ; it need only be parallel to the gnomon . Thus , a plane inclined at the angle of latitude ( relative to horizontal ) under the similarly inclined gnomon will be a polar dial . The perpendicular spacing X of the hour - lines in the plane is described by the formula
Reuleaux triangle
The existence of Reuleaux polygons shows that diameter measurements alone can not verify that an object has a circular cross-section . Overlooking this fact may have played a role in the Space Shuttle Challenger disaster , as the roundness of sections of the rocket in that launch was tested only by measuring different diameters , and off - round shapes may cause unusually high stresses that could have been one of the factors causing the disaster .
Hilda group
Hildas ' surface colors often correspond to the low - albedo D - type and P - type ; however , a small portion are C - type . D - type and P - type asteroids have surface colors , and thus also surface mineralogies , similar to those of cometary nuclei . This implies that they share a common origin .
Moon landing
Many missions were failures at launch . In addition , several unmanned landing missions achieved the Lunar surface but were unsuccessful , including : Luna 15 , Luna 18 , and Luna 23 all crashed on landing ; and the U.S. Surveyor 4 lost all radio contact only moments before its landing .
Meander
The oxbow lake , which is the most common type of fluvial lake , is a crescent - shaped lake that derives its name from its distinctive curved shape . Oxbow lakes are also known as cutoff lakes . Such lakes form regularly in undisturbed floodplains as a result of the normal process of fluvial meandering . Either a river or stream forms a sinuous channel as the outer side of its bends are eroded away and sediments accumulate on the inner side , which forms a meandering horseshoe - shaped bend . Eventually as the result of its meandering , the fluvial channel cuts through the narrow neck of the meander and forms a cutoff meander . The final break - through of the neck , which is called a neck cutoff , often occurs during a major flood because that is when the watercourse is out of its banks and can flow directly across the neck and erode it with the full force of the flood .
Diamond
Diamonds occur most often as euhedral or rounded octahedra and twinned octahedra known as macles . As diamond 's crystal structure has a cubic arrangement of the atoms , they have many facets that belong to a cube , octahedron , rhombicosidodecahedron , tetrakis hexahedron or disdyakis dodecahedron . The crystals can have rounded off and unexpressive edges and can be elongated . Diamonds ( especially those with rounded crystal faces ) are commonly found coated in nyf , an opaque gum - like skin .
Flag of Portugal
The armillary sphere has a diameter equal to ⁄ width and is equidistant from the upper and lower edges of the flag . The sphere , drawn in perspective , possesses six edge - embossed arcs , four of which are great circles and two are small circles . The great circles represent the ecliptic ( wider oblique arc ) , the equator , and two meridians . These last three are positioned so that the intersections between each two arcs make a right angle ; one meridian lies on the flag 's plane while the other is perpendicular to it . The small circles consist of two parallels ( the tropics ) , each tangent to one of the ecliptic - meridian intersections .
Magnetosphere of Jupiter
Jupiter 's internal magnetic field prevents the solar wind , a stream of ionized particles emitted by the Sun , from interacting directly with its atmosphere , and instead diverts it away from the planet , effectively creating a cavity in the solar wind flow , called a magnetosphere , composed of a plasma different from that of the solar wind . The Jovian ( i.e. pertaining to Jupiter ) magnetosphere is so large that the Sun and its visible corona would fit inside it with room to spare . If one could see it from Earth , it would appear five times larger than the full moon in the sky despite being nearly 1700 times farther away .
Plate tectonics
In 1973 , George W. Moore of the USGS and R.C. Bostrom presented evidence for a general westward drift of the Earth 's lithosphere with respect to the mantle . He concluded that tidal forces ( the tidal lag or `` friction '' ) caused by the Earth 's rotation and the forces acting upon it by the Moon are a driving force for plate tectonics . As the Earth spins eastward beneath the moon , the moon 's gravity ever so slightly pulls the Earth 's surface layer back westward , just as proposed by Alfred Wegener ( see above ) . In a more recent 2006 study , scientists reviewed and advocated these earlier proposed ideas . It has also been suggested recently in Lovett ( 2006 ) that this observation may also explain why Venus and Mars have no plate tectonics , as Venus has no moon and Mars ' moons are too small to have significant tidal effects on the planet . In a recent paper , it was suggested that , on the other hand , it can easily be observed that many plates are moving north and eastward , and that the dominantly westward motion of the Pacific Ocean basins derives simply from the eastward bias of the Pacific spreading center ( which is not a predicted manifestation of such lunar forces ) . In the same paper the authors admit , however , that relative to the lower mantle , there is a slight westward component in the motions of all the plates . They demonstrated though that the westward drift , seen only for the past 30 Ma , is attributed to the increased dominance of the steadily growing and accelerating Pacific plate . The debate is still open .
Area of a circle
for all R > 0 ( \ displaystyle R > 0 ) . Intuitively , this is because the sphere tends to curve back on itself , yielding circles of smaller area than those in the plane , whilst the hyperbolic plane , when immersed into space , develops fringes that produce additional area . It is more generally true that the area of the circle of a fixed radius R is a strictly decreasing function of the curvature .
Artemis
Artemis was sometimes represented in Classical art with the crown of the crescent moon , such as also found on Luna and others .
Sundial
In other cases , the hour - lines are not spaced evenly , even though the shadow rotates uniformly . If the gnomon is not aligned with the celestial poles , even its shadow will not rotate uniformly , and the hour lines must be corrected accordingly . The rays of light that graze the tip of a gnomon , or which pass through a small hole , or reflect from a small mirror , trace out a cone aligned with the celestial poles . The corresponding light - spot or shadow - tip , if it falls onto a flat surface , will trace out a conic section , such as a hyperbola , ellipse or ( at the North or South Poles ) a circle .
Moon landing
After the unsuccessful attempt by the Luna 1 to land on the moon in 1959 , the Soviet Union performed the first hard ( unpowered ) moon landing later that same year with the Luna 2 spacecraft , a feat the U.S. duplicated in 1962 with Ranger 4 . Since then , twelve Soviet and U.S. spacecraft have used braking rockets to make soft landings and perform scientific operations on the lunar surface , between 1966 and 1976 . In 1966 the USSR accomplished the first soft landings and took the first pictures from the lunar surface during the Luna 9 and Luna 13 missions . The U.S. followed with five unmanned Surveyor soft landings .
Kuiper belt
The largest KBOs , such as Pluto and Quaoar , have surfaces rich in volatile compounds such as methane , nitrogen and carbon monoxide ; the presence of these molecules is likely due to their moderate vapor pressure in the 30 -- 50 K temperature range of the Kuiper belt . This allows them to occasionally boil off their surfaces and then fall again as snow , whereas compounds with higher boiling points would remain solid . The relative abundances of these three compounds in the largest KBOs is directly related to their surface gravity and ambient temperature , which determines which they can retain . Water ice has been detected in several KBOs , including members of the Haumea family such as 1996 TO , mid-sized objects such as 38628 Huya and 20000 Varuna , and also on some small objects . The presence of crystalline ice on large and mid-sized objects , including 50000 Quaoar where ammonia hydrate has also been detected , may indicate past tectonic activity aided by melting point lowering due to the presence of ammonia .
Moon landing
The first attempts to perform a Moon landing took place in 1962 during the Rangers 3 , 4 and 5 missions flown by the United States . All three Block II missions basic vehicles were 3.1 m high and consisted of a lunar capsule covered with a balsa wood impact - limiter , 650 mm in diameter , a mono - propellant mid-course motor , a retrorocket with a thrust of 5,050 pounds - force ( 22.5 kN ) , and a gold - and chrome - plated hexagonal base 1.5 m in diameter . This lander ( code - named Tonto ) was designed to provide impact cushioning using an exterior blanket of crushable balsa wood and an interior filled with incompressible liquid freon . A 42 kg ( 56 pounds ) 30 - centimetre - diameter ( 0.98 ft ) metal payload sphere floated and was free to rotate in a liquid freon reservoir contained in the landing sphere .
Lunar distance (astronomy)
Lunar distance is commonly used to express the distance to near - Earth object encounters . Lunar distance is also an important astronomical datum ; the precision of this measurement to a few parts in a trillion has useful implications for testing gravitational theories such as general relativity , and for refining other astronomical values such as Earth mass , Earth radius , and Earth 's rotation . The measurement is also useful in characterizing the lunar radius , the mass of the Sun and the distance to the Sun .