vania-janet/multiturn-rag-retrieval-data huggingface dataset:
Constellation
The Western - traditional constellations are the forty - eight Greek classical patterns , as stated in both Aratus ' work Phenomena or Ptolemy 's Almagest -- though their existence probably predates these constellation names by several centuries . Newer constellations in the far southern sky were added much later during the 15th to mid-18th century , when European explorers began travelling to the southern hemisphere . Twelve important constellations are assigned to the zodiac , where the Sun , Moon , and planets all follow the ecliptic . The origins of the zodiac probably date back into prehistory , whose astrological divisions became prominent c. 400 BC within Babylonian or Chaldean astronomy .
Season
Illumination of Earth by Sun at the northern solstice . Illumination of Earth by Sun at the southern solstice . Diagram of the Earth 's seasons as seen from the north . Far right : southern solstice Diagram of the Earth 's seasons as seen from the south . Far left : northern solstice Play media Animation of Earth as seen daily from the Sun looking at UTC + 02 : 00 , showing the solstice and changing seasons . Two images showing the amount of reflected sunlight at southern and northern summer solstices respectively ( watts / m2 ) .
Mesopotamia
The Babylonian astronomers were very adept at mathematics and could predict eclipses and solstices . Scholars thought that everything had some purpose in astronomy . Most of these related to religion and omens . Mesopotamian astronomers worked out a 12 - month calendar based on the cycles of the moon . They divided the year into two seasons : summer and winter . The origins of astronomy as well as astrology date from this time .
Venus
The Venusian orbit is slightly inclined relative to Earth 's orbit ; thus , when the planet passes between Earth and the Sun , it usually does not cross the face of the Sun . Transits of Venus occur when the planet 's inferior conjunction coincides with its presence in the plane of Earth 's orbit . Transits of Venus occur in cycles of 7009766849680000000 ♠ 243 years with the current pattern of transits being pairs of transits separated by eight years , at intervals of about 7009332932680000000 ♠ 105.5 years or 7009383424840000000 ♠ 121.5 years -- a pattern first discovered in 1639 by the English astronomer Jeremiah Horrocks .
Season
The seasons result from the Earth 's axis of rotation being tilted with respect to its orbital plane by an angle of approximately 23.4 degrees . ( This tilt is also known as `` obliquity of the ecliptic '' . ) Four
Wonders of the Solar System
The first episode illustrates how the formation and behaviour of the Sun affects each planet in the Solar System . During this episode , Cox visits India to view and explain the workings of a total solar eclipse and the partial eclipses that occur on other planets . He travels to the Iguazu Falls to relate the causality between river levels , and sunspot fluctuations . An explanation of the Earth 's exposure to the power of the Sun occurs in Death Valley , California , USA , with an experiment inspired by John Herschel 's actinometer . He also travels to Norway to observe and explain the defensive role of the Earth 's magnetosphere against the sun 's solar wind and its role in forming the Aurora Borealis . He also relates the Voyager missions and their continuing exploration of the massive reach of the sun 's gravitational forces on objects in the farthest regions of the solar system . Finally , in the clear skies of the Atacama Desert , at the Paranal Observatory he is able to observe , with the naked eye , the myriad of stars on the Milky Way and relates the meaning of their diverse colours as mapped on the Hertzsprung -- Russell diagram .
Jupiter
Earth overtakes Jupiter every 398.9 days as it orbits the Sun , a duration called the synodic period . As it does so , Jupiter appears to undergo retrograde motion with respect to the background stars . That is , for a period Jupiter seems to move backward in the night sky , performing a looping motion .
Rotation
This rotation induces a centrifugal acceleration in the reference frame of the Earth which slightly counteracts the effect of gravity the closer one is to the equator . One effect is that an object weighs slightly less at the equator . Another is that the Earth is slightly deformed into an oblate spheroid .
Venus
Venus `` overtakes '' Earth every 584 days as it orbits the Sun . As it does so , it changes from the `` Evening Star '' , visible after sunset , to the `` Morning Star '' , visible before sunrise . Although Mercury , the other inferior planet , reaches a maximum elongation of only 28 ° and is often difficult to discern in twilight , Venus is hard to miss when it is at its brightest . Its greater maximum elongation means it is visible in dark skies long after sunset . As the brightest point - like object in the sky , Venus is a commonly misreported `` unidentified flying object '' .
Constellation
The Babylonians were the first to recognize that astronomical phenomena are periodic and apply mathematics to their predictions . The oldest Babylonian star catalogues of stars and constellations date back to the beginning in the Middle Bronze Age , most notably the Three Stars Each texts and the MUL. APIN , an expanded and revised version based on more accurate observation from around 1000 BC . However , the numerous Sumerian names in these catalogues suggest that they built on older , but otherwise unattested , Sumerian traditions of the Early Bronze Age .
Venus
In the second century , in his astronomical treatise Almagest , Ptolemy theorized that both Mercury and Venus are located between the Sun and the Earth . The 11th century Persian astronomer Avicenna claimed to have observed the transit of Venus , which later astronomers took as confirmation of Ptolemy 's theory . In the 12th century , the Andalusian astronomer Ibn Bajjah observed `` two planets as black spots on the face of the Sun '' , which were later identified as the transits of Venus and Mercury by the Maragha astronomer Qotb al - Din Shirazi in the 13th century . Galileo
Sun path
Everywhere around the world during the equinoxes ( March 20 / 21 and September 22 / 23 ) except for the poles , the sun rises due east and sets due west . In the Northern Hemisphere , the equinox sun peaks in the southern half ( about halfway up from the horizon at mid latitude ) of the sky , while in the Southern Hemisphere , that sun peaks in the northern half of the sky . When facing the equator , the sun appears to move from left to right in the Northern Hemisphere and from right to left in the Southern Hemisphere .
Astronomical spectroscopy
Spectroscopic binaries can be also detected due to their radial velocity ; as they orbit around each other one star may be moving towards the Earth whilst the other moves away , causing a Doppler shift in the composite spectrum . The orbital plane of the system determines the magnitude of the observed shift : if the observer is looking perpendicular to the orbital plane there will be no observed radial velocity . For example , if you look at a carousel from the side , you will see the animals moving toward and away from you , whereas if you look from directly above they will only be moving in the horizontal plane .
Equator
Seasons result from the yearly revolution of the Earth around the Sun and the tilt of the Earth 's axis relative to the plane of revolution . During the year the northern and southern hemispheres are inclined toward or away from the sun according to Earth 's position in its orbit . The hemisphere inclined toward the sun receives more sunlight and is in summer , while the other hemisphere receives less sun and is in winter ( see solstice ) .
Sun path
Day arcs at 0 ° latitude , equator . Day arcs at 20 ° latitude . Day arcs at 50 ° latitude . Day arcs at 70 ° latitude . Day arcs at 90 ° latitude , pole .
Sundial
A standard time zone covers roughly 15 ° of longitude , so any point within that zone which is not on the reference longitude ( generally a multiple of 15 ° ) will experience a difference from standard time equal to 4 minutes of time per degree . For illustration , sunsets and sunrises are at a much later `` official '' time at the western edge of a time - zone , compared to sunrise and sunset times at the eastern edge . If a sundial is located at , say , a longitude 5 ° west of the reference longitude , its time will read 20 minutes slow , since the sun appears to revolve around the Earth at 15 ° per hour . This is a constant correction throughout the year . For equiangular dials such as equatorial , spherical or Lambert dials , this correction can be made by rotating the dial surface by an angle equaling the difference in longitude , without changing the gnomon position or orientation . However , this method does not work for other dials , such as a horizontal dial ; the correction must be applied by the viewer .
Julian calendar
31 , 28 / 29 , 31 , 30 , 31 , 30 , 31 , 31 , 30 , 31 , 30 , 31
Meander
The higher ( lower ) velocities at the outside ( inside ) bend result in higher ( lower ) shear stresses and therefore results in erosion ( deposition ) . Thus meander bends erode at the outside bend , causing the river to becoming increasingly sinuous ( until cutoff events occur ) . Deposition at the inside bend occur such that for most natural meandering rivers , the river width remains nearly constant , even as the river evolves .
Hilda group
The observed peculiarities in the Hildas ' motion are based on data for a few hundred objects known to date and generate still more questions . Further observations are needed to expand on the list of Hildas . Such observations are most favorable when Earth is near conjunction with the mid-sides of the Hildas Triangle . These moments occur each 4 and 1 / 3 months . In these circumstances the brilliance of objects of similar size could run up to 2.5 magnitudes as compared to the apexes .
Death Star
In 1981 , following the Voyager spacecraft 's flight past Saturn , scientists noticed a resemblance between one of the planet 's moons , Mimas , and the Death Star . Additionally , a few astronomers sometimes use the term `` Death Star '' to describe Nemesis , a hypothetical star postulated in 1984 to be responsible for gravitationally forcing comets and asteroids from the Oort cloud toward Earth .
Sundial
In some sundials , the equation of time correction is provided as an informational plaque affixed to the sundial , for the observer to calculate . In more sophisticated sundials the equation can be incorporated automatically . For example , some equatorial bow sundials are supplied with a small wheel that sets the time of year ; this wheel in turn rotates the equatorial bow , offsetting its time measurement . In other cases , the hour lines may be curved , or the equatorial bow may be shaped like a vase , which exploits the changing altitude of the sun over the year to effect the proper offset in time .
Geologic time scale
Sequences of strata often become eroded , distorted , tilted , or even inverted after deposition Strata laid down at the same time in different areas could have entirely different appearances The strata of any given area represented only part of Earth 's long history
Constellation
Although stars in constellations appear near each other in the sky , they usually lie at a variety of distances away from the observer . Since stars also travel along their own orbits through the Milky Way , the constellation outlines change slowly over time . After tens to hundreds of thousands of years , their familiar outlines gradually become unrecognisable . Astronomers can predict the past or future constellation outlines by measuring their individual stars ' common proper motions or cpm by accurate astrometry and their radial velocities by astronomical spectroscopy .
Sagittarius (constellation)
The Lagoon Nebula ( M8 ) is an emission nebula that is located 5,000 light - years from Earth and measures 140 light - years by 60 light - years ( 1.5 ° ) . Though it appears grey in telescopes to the unaided eye , long - exposure photographs reveal its pink hue , common to emission nebulae . It is fairly bright , with an integrated magnitude of 3.0 . The Lagoon Nebula was discovered independently by John Flamsteed in 1680 , Guillaume Le Gentil in 1747 , and Charles Messier in 1764 . The central area of the Lagoon Nebula is also known as the Hourglass Nebula , so named for its distinctive shape . The Hourglass Nebula has its shape because of matter propelled by Herschel 36 . The Lagoon Nebula also features three dark nebulae catalogued in Barnard 's Catalog . The Lagoon Nebula was instrumental in the discovery of Bok globules , as Bart Bok studied prints of the nebula intensively in 1947 . Approximately 17,000 Bok globules were discovered in the nebula nine years later as a part of the Palomar Sky Survey ; studies later showed that Bok 's hypothesis that the globules held protostars was correct . The Omega Nebula is a fairly bright nebula ; it has an integrated magnitude of 6.0 and is 4890 light - years from Earth . It was discovered in 1746 by Philippe Loys de Chésaux ; observers since him have differed greatly in how they view the nebula , hence its myriad of names . Most often viewed as a checkmark , it was seen as a swan by George F. Chambers in 1889 , a loon by Roy Bishop , and as a curl of smoke by Camille Flammarion . The Trifid Nebula ( M20 , NGC 6514 ) is an emission nebula in Sagittarius that lies less than two degrees from the Lagoon Nebula . Discovered by French comet - hunter Charles Messier , it is located between 2,000 and 9,000 light - years from Earth and has a diameter of approximately 50 light - years . The outside of the Trifid Nebula is a bluish reflection nebula ; the interior is pink with two dark bands that divide it into three areas , sometimes called `` lobes '' .
Rotation
Most planets in our solar system , including Earth , spin in the same direction as they orbit the Sun . The exceptions are Venus and Uranus . Uranus rotates nearly on its side relative to its orbit . Current speculation is that Uranus started off with a typical prograde orientation and was knocked on its side by a large impact early in its history . Venus may be thought of as rotating slowly backwards ( or being `` upside down '' ) . The dwarf planet Pluto ( formerly considered a planet ) is anomalous in this and other ways .
Halley's Comet
Despite the vast size of its coma , Halley 's nucleus is relatively small : barely 15 kilometers long , 8 kilometers wide and perhaps 8 kilometers thick . Its shape vaguely resembles that of a peanut . Its mass is relatively low ( roughly 2.2 × 10 kg ) and its average density is about 0.6 g / cm , indicating that it is made of a large number of small pieces , held together very loosely , forming a structure known as a rubble pile . Ground - based observations of coma brightness suggested that Halley 's rotation period was about 7.4 days . Images taken by the various spacecraft , along with observations of the jets and shell , suggested a period of 52 hours . Given the irregular shape of the nucleus , Halley 's rotation is likely to be complex . Although only 25 % of Halley 's surface was imaged in detail during the flyby missions , the images revealed an extremely varied topography , with hills , mountains , ridges , depressions , and at least one crater .
Area of a circle
We can stretch a disk to form an ellipse . Because this stretch is a linear transformation of the plane , it has a distortion factor which will change the area but preserve ratios of areas . This observation can be used to compute the area of an arbitrary ellipse from the area of a unit circle .
Julian calendar
29 , 28 , 31 , 29 , 31 , 29 , 31 , 29 , 29 , 31 , 29 , 29 .
Sundial
where R is the radius of the Foster - Lambert dial and δ again indicates the Sun 's declination for that time of year .
Sun path
Sun path , sometimes also called day arc , refers to the daily and seasonal arc - like path that the Sun appears to follow across the sky as the Earth rotates and orbits the Sun . The Sun 's path affects the length of daytime experienced and amount of daylight received along a certain latitude during a given season .
Julian calendar
The Julian reform set the lengths of the months to their modern values . However , a 13th - century scholar , Sacrobosco , proposed a different explanation for the lengths of Julian months which is still widely repeated but is certainly wrong .
Conic section
Conic sections are important in astronomy : the orbits of two massive objects that interact according to Newton 's law of universal gravitation are conic sections if their common center of mass is considered to be at rest . If they are bound together , they will both trace out ellipses ; if they are moving apart , they will both follow parabolas or hyperbolas . See two - body problem .
Exoplanet
For gas giants , geometric albedo generally decreases with increasing metallicity or atmospheric temperature unless there are clouds to modify this effect . Increased cloud - column depth increases the albedo at optical wavelengths , but decreases it at some infrared wavelengths . Optical albedo increases with age , because older planets have higher cloud - column depths . Optical albedo decreases with increasing mass , because higher - mass giant planets have higher surface gravities , which produces lower cloud - column depths . Also , elliptical orbits can cause major fluctuations in atmospheric composition , which can have a significant effect .
Constellation
In 1930 , the boundaries between the 88 constellations were devised by Eugène Delporte along vertical and horizontal lines of right ascension and declination . However , the data he used originated back to epoch B1875. 0 , which was when Benjamin A. Gould first made his proposal to designate boundaries for the celestial sphere , a suggestion upon which Delporte would base his work . The consequence of this early date is that because of the precession of the equinoxes , the borders on a modern star map , such as epoch J2000 , are already somewhat skewed and no longer perfectly vertical or horizontal . This effect will increase over the years and centuries to come .
Julian calendar
30 , 29 , 30 , 29 , 30 , 29 , 30 , 29 , 30 , 29 , 30 , 29 .
Satellite
Circular orbit : An orbit that has an eccentricity of 0 and whose path traces a circle . Hohmann transfer orbit : An orbit that moves a spacecraft from one approximately circular orbit , usually the orbit of a planet , to another , using two engine impulses . The perihelion of the transfer orbit is at the same distance from the Sun as the radius of one planet 's orbit , and the aphelion is at the other . The two rocket burns change the spacecraft 's path from one circular orbit to the transfer orbit , and later to the other circular orbit . This maneuver was named after Walter Hohmann . Elliptic orbit : An orbit with an eccentricity greater than 0 and less than 1 whose orbit traces the path of an ellipse . Geosynchronous transfer orbit : An elliptic orbit where the perigee is at the altitude of a Low Earth orbit ( LEO ) and the apogee at the altitude of a geosynchronous orbit . Geostationary transfer orbit : An elliptic orbit where the perigee is at the altitude of a Low Earth orbit ( LEO ) and the apogee at the altitude of a geostationary orbit . Molniya orbit : A highly elliptic orbit with inclination of 63.4 ° and orbital period of half of a sidereal day ( roughly 12 hours ) . Such a satellite spends most of its time over two designated areas of the planet ( specifically Russia and the United States ) . Tundra orbit : A highly elliptic orbit with inclination of 63.4 ° and orbital period of one sidereal day ( roughly 24 hours ) . Such a satellite spends most of its time over a single designated area of the planet .
Halley's Comet
Some scholars have proposed that first - century Mesopotamian astronomers already had recognized Halley 's Comet as periodic . This theory notes a passage in the Bavli Talmud that refers to `` a star which appears once in seventy years that makes the captains of the ships err . ''
Constellation
The Great Rift , a series of dark patches in the Milky Way , is more visible and striking in the southern hemisphere than in the northern . It vividly stands out when conditions are otherwise so dark that the Milky Way 's central region casts shadows on the ground . Some cultures have discerned shapes in these patches and have given names to these `` dark cloud constellations '' . Members of the Inca civilization identified various dark areas or dark nebulae in the Milky Way as animals , and associated their appearance with the seasonal rains . Australian Aboriginal astronomy also describes dark cloud constellations , the most famous being the `` emu in the sky '' whose head is formed by the Coalsack , a dark nebula , instead of the stars .
Season
First light comes in late January because the sky has twilight , being a glow on the horizon , for increasing hours each day , for more than a month before the sun first appears with its disc above the horizon . From mid-November to mid-January , there is no twilight .
Speed of light
Previously , the inverse of c expressed in seconds per astronomical unit was measured by comparing the time for radio signals to reach different spacecraft in the Solar System , with their position calculated from the gravitational effects of the Sun and various planets . By combining many such measurements , a best fit value for the light time per unit distance could be obtained . For example , in 2009 , the best estimate , as approved by the International Astronomical Union ( IAU ) , was :
Observable universe
WMAP nine - year results combined with other measurements give the redshift of photon decoupling as z = 7003109164000000000 ♠ 1091. 64 ± 0.47 , which implies that the scale factor at the time of photon decoupling would be ​ ⁄ . So if the matter that originally emitted the oldest CMBR photons has a present distance of 46 billion light - years , then at the time of decoupling when the photons were originally emitted , the distance would have been only about 42 million light - years .
Observable universe
180 billion light - years This estimate combines the erroneous 156 - billion - light - year figure with evidence that the M33 Galaxy is actually fifteen percent farther away than previous estimates and that , therefore , the Hubble constant is fifteen percent smaller . The 180 - billion figure is obtained by adding 15 % to 156 billion light - years .
Observable universe
According to calculations , the current comoving distance -- proper distance , which takes into account that the universe has expanded since the light was emitted -- to particles from which the cosmic microwave background radiation ( CMBR ) was emitted , which represent the radius of the visible universe , is about 14.0 billion parsecs ( about 45.7 billion light - years ) , while the comoving distance to the edge of the observable universe is about 14.3 billion parsecs ( about 46.6 billion light - years ) , about 2 % larger . The radius of the observable universe is therefore estimated to be about 46.5 billion light - years and its diameter about 28.5 gigaparsecs ( 93 billion light - years , 8.8 × 10 kilometres or 5.5 × 10 miles ) . The total mass of ordinary matter in the universe can be calculated using the critical density and the diameter of the observable universe to be about 1.5 × 10 kg .