sentence-transformers/squad huggingface dataset:
Passage: In 2007, it was discovered that the upper troposphere of Neptune's south pole was about 10 K warmer than the rest of its atmosphere, which averages approximately 73 K (−200 °C). The temperature differential is enough to let methane, which elsewhere is frozen in the troposphere, escape into the stratosphere near the pole. The relative "hot spot" is due to Neptune's axial tilt, which has exposed the south pole to the Sun for the last quarter of Neptune's year, or roughly 40 Earth years. As Neptune slowly moves towards the opposite side of the Sun, the south pole will be darkened and the north pole illuminated, causing the methane release to shift to the north pole.

Question: How much warmer is Neptune's south pole to the rest of it's atmosphere?

Question: Where does methane in the south pole escape to on Neptune?

Question: What is the average temperature of Neptune's south pole?

Question: How many earth years is Neptune's south pole exposed to the sun?

Question: To which pole will Neptune's methane shift to as it moves to the opposite side of the sun?
Passage: The Scooter is another storm, a white cloud group farther south than the Great Dark Spot. This nickname first arose during the months leading up to the Voyager 2 encounter in 1989, when they were observed moving at speeds faster than the Great Dark Spot (and images acquired later would subsequently reveal the presence of clouds moving even faster than those that had initially been detected by Voyager 2). The Small Dark Spot is a southern cyclonic storm, the second-most-intense storm observed during the 1989 encounter. It was initially completely dark, but as Voyager 2 approached the planet, a bright core developed and can be seen in most of the highest-resolution images.

Question: What white cloud group on Neptune is farther south than the dark great spot?

Question: When was The Scooter on Neptune observed?

Question: What type of storm is The Scooter on Neptune?

Question: What detected the storms on Neptune?

Question: What is the second most intense storm on Neptune?
Passage: Neptune's dark spots are thought to occur in the troposphere at lower altitudes than the brighter cloud features, so they appear as holes in the upper cloud decks. As they are stable features that can persist for several months, they are thought to be vortex structures. Often associated with dark spots are brighter, persistent methane clouds that form around the tropopause layer. The persistence of companion clouds shows that some former dark spots may continue to exist as cyclones even though they are no longer visible as a dark feature. Dark spots may dissipate when they migrate too close to the equator or possibly through some other unknown mechanism.

Question: Where are Neptune's dark spots thought to occur?

Question: What do Neptune's dark spots appear as in the cloud decks?

Question: Since Neptune's dark spots persist for several months, what are they thought to be?

Question: What on Neptune are associated with dark spots that are brighter?

Question: When Neptune's dark spots migrate too close to the equator, what do they do?
Passage: Neptune's more varied weather when compared to Uranus is due in part to its higher internal heating. Although Neptune lies over 50% further from the Sun than Uranus, and receives only 40% its amount of sunlight, the two planets' surface temperatures are roughly equal. The upper regions of Neptune's troposphere reach a low temperature of 51.8 K (−221.3 °C). At a depth where the atmospheric pressure equals 1 bar (100 kPa), the temperature is 72.00 K (−201.15 °C). Deeper inside the layers of gas, the temperature rises steadily. As with Uranus, the source of this heating is unknown, but the discrepancy is larger: Uranus only radiates 1.1 times as much energy as it receives from the Sun; whereas Neptune radiates about 2.61 times as much energy as it receives from the Sun. Neptune is the farthest planet from the Sun, yet its internal energy is sufficient to drive the fastest planetary winds seen in the Solar System. Depending on the thermal properties of its interior, the heat left over from Neptune's formation may be sufficient to explain its current heat flow, though it is more difficult to simultaneously explain Uranus's lack of internal heat while preserving the apparent similarity between the two planets.

Question: Why might Neptune have more varied weather than Uranus?

Question: How much farther is Neptune from the Sun than Uranus?

Question: How much percentage of the sun does Neptune get compared to Uranus?

Question: How much more energy does Neptune radiate than it receives?

Question: The current heat flow on Neptune might be explained by what?
Passage: On 11 July 2011, Neptune completed its first full barycentric orbit since its discovery in 1846, although it did not appear at its exact discovery position in the sky, because Earth was in a different location in its 365.26-day orbit. Because of the motion of the Sun in relation to the barycentre of the Solar System, on 11 July Neptune was also not at its exact discovery position in relation to the Sun; if the more common heliocentric coordinate system is used, the discovery longitude was reached on 12 July 2011.

Question: When did Neptune complete it's first barycentric orbit since it's discovery?

Question: What is the Earth's orbit?

Question: Why didn't Neptune appear to be in it's exact discover position?

Question: Using the heliocentric coordinate system, when did Neptune reach the discovery longitude?
Passage: Neptune's orbit has a profound impact on the region directly beyond it, known as the Kuiper belt. The Kuiper belt is a ring of small icy worlds, similar to the asteroid belt but far larger, extending from Neptune's orbit at 30 AU out to about 55 AU from the Sun. Much in the same way that Jupiter's gravity dominates the asteroid belt, shaping its structure, so Neptune's gravity dominates the Kuiper belt. Over the age of the Solar System, certain regions of the Kuiper belt became destabilised by Neptune's gravity, creating gaps in the Kuiper belt's structure. The region between 40 and 42 AU is an example.

Question: What is the region behind Neptune called?

Question: What does the Kuiper belt consist of?

Question: Where is the Kuiper belt relative to Neptune?

Question: What dominates the Kuiper belt?

Question: What did Neptune's gravity do to Kuiper belt?
Passage: There do exist orbits within these empty regions where objects can survive for the age of the Solar System. These resonances occur when Neptune's orbital period is a precise fraction of that of the object, such as 1:2, or 3:4. If, say, an object orbits the Sun once for every two Neptune orbits, it will only complete half an orbit by the time Neptune returns to its original position. The most heavily populated resonance in the Kuiper belt, with over 200 known objects, is the 2:3 resonance. Objects in this resonance complete 2 orbits for every 3 of Neptune, and are known as plutinos because the largest of the known Kuiper belt objects, Pluto, is among them. Although Pluto crosses Neptune's orbit regularly, the 2:3 resonance ensures they can never collide. The 3:4, 3:5, 4:7 and 2:5 resonances are less populated.

Question: What is the fraction of the most heavily populated resonance in the Kuiper belt?

Question: What is the best known, and largest, object in the Kuiper belt?

Question: How many known objects is in the most populated resonance of the Kuiper belt?

Question: What is the resonance of Pluto in the Kuiper belt?

Question: Which resonances are less populated in the Kuiper belt?
Passage: Neptune has a number of known trojan objects occupying both the Sun–Neptune L4 and L5 Lagrangian points—gravitationally stable regions leading and trailing Neptune in its orbit, respectively. Neptune trojans can be viewed as being in a 1:1 resonance with Neptune. Some Neptune trojans are remarkably stable in their orbits, and are likely to have formed alongside Neptune rather than being captured. The first and so far only object identified as associated with Neptune's trailing L5 Lagrangian point is 2008 LC18. Neptune also has a temporary quasi-satellite, (309239) 2007 RW10. The object has been a quasi-satellite of Neptune for about 12,500 years and it will remain in that dynamical state for another 12,500 years.

Question: What is the resonance of Neptune trojans?

Question: Where did most Neptune trojans form?

Question: What is the only object identified with Neptune's trailing L5 Lagrangian point?

Question: What is Neptune's temporary quasi-satellite named?

Question: How long has Neptune's quasi-satellite been with Neptune?
Passage: The formation of the ice giants, Neptune and Uranus, has proven difficult to model precisely. Current models suggest that the matter density in the outer regions of the Solar System was too low to account for the formation of such large bodies from the traditionally accepted method of core accretion, and various hypotheses have been advanced to explain their formation. One is that the ice giants were not formed by core accretion but from instabilities within the original protoplanetary disc and later had their atmospheres blasted away by radiation from a nearby massive OB star.

Question: What could have blasted Neptune and Uranus's atmosphere with radiation, aiding in creation?

Question: What is too low to account for the formation of Neptune?

Question: If Neptune was formed from instabilities within the original protoplanetary disc, what was it not formed by?
Passage: An alternative concept is that they formed closer to the Sun, where the matter density was higher, and then subsequently migrated to their current orbits after the removal of the gaseous protoplanetary disc. This hypothesis of migration after formation is favoured, due to its ability to better explain the occupancy of the populations of small objects observed in the trans-Neptunian region. The current most widely accepted explanation of the details of this hypothesis is known as the Nice model, which explores the effect of a migrating Neptune and the other giant planets on the structure of the Kuiper belt.

Question: If Neptune formed closer to the sun, what is the matter density?

Question: If Neptune formed closer to the sun, what caused it to migrate to it's current orbit?

Question: What is the most widely accepted explanation of Neptune's formation called?

Question: What does The Nice model consider effected the migration of Neptune?
Passage: Neptune has 14 known moons. Triton is the largest Neptunian moon, comprising more than 99.5% of the mass in orbit around Neptune,[e] and it is the only one massive enough to be spheroidal. Triton was discovered by William Lassell just 17 days after the discovery of Neptune itself. Unlike all other large planetary moons in the Solar System, Triton has a retrograde orbit, indicating that it was captured rather than forming in place; it was probably once a dwarf planet in the Kuiper belt. It is close enough to Neptune to be locked into a synchronous rotation, and it is slowly spiralling inward because of tidal acceleration. It will eventually be torn apart, in about 3.6 billion years, when it reaches the Roche limit. In 1989, Triton was the coldest object that had yet been measured in the Solar System, with estimated temperatures of 38 K (−235 °C).

Question: How many moons does Neptune have?

Question: What is Neptune's largest moon?

Question: Who discovered Triton?

Question: What orbit does Triton have around Neptune?

Question: What does Triton's orbit suggest about it's relation to Neptune?
Passage: From July to September 1989, Voyager 2 discovered six moons of Neptune. Of these, the irregularly shaped Proteus is notable for being as large as a body of its density can be without being pulled into a spherical shape by its own gravity. Although the second-most-massive Neptunian moon, it is only 0.25% the mass of Triton. Neptune's innermost four moons—Naiad, Thalassa, Despina and Galatea—orbit close enough to be within Neptune's rings. The next-farthest out, Larissa, was originally discovered in 1981 when it had occulted a star. This occultation had been attributed to ring arcs, but when Voyager 2 observed Neptune in 1989, Larissa was found to have caused it. Five new irregular moons discovered between 2002 and 2003 were announced in 2004. A new moon and the smallest yet, S/2004 N 1, was found in 2013. Because Neptune was the Roman god of the sea, Neptune's moons have been named after lesser sea gods.

Question: What discovered six moons of Neptune in 1989?

Question: What is the second most massive Neptunian moon?

Question: What is notable about the moon Proteus?

Question: Which are Neptune's four innermost moons?

Question: When was Neptune's moon Larissa discovered?
Passage: Because of the distance of Neptune from Earth, its angular diameter only ranges from 2.2 to 2.4 arcseconds, the smallest of the Solar System planets. Its small apparent size makes it challenging to study it visually. Most telescopic data was fairly limited until the advent of Hubble Space Telescope (HST) and large ground-based telescopes with adaptive optics (AO). The first scientifically useful observation of Neptune from ground-based telescopes using adaptive optics, was commenced in 1997 from Hawaii. Neptune is currently entering its spring and summer season and has been shown to be heating up, with increased atmospheric activity and brightness as a consequence. Combined with technological advancements, ground-based telescopes with adaptive optics are recording increasingly more detailed images of this Outer Planet. Both the HST and AO telescopes on Earth has made many new discoveries within the Solar System since the mid-1990s, with a large increase in the number of known satellites and moons around the Outer Planets for example. In 2004 and 2005, five new small satellites of Neptune with diameters between 38 and 61 kilometres were discovered.

Question: What is Neptune's angular diameter range?

Question: The advent of what telescope made it easier to study Neptune?

Question: When was the first useful observation of Neptune from the ground?

Question: What seasons are Neptune currently entering?

Question: What was discovered around Neptune in 2004 and 2005?
Passage: Voyager 2 is the only spacecraft that has visited Neptune. The spacecraft's closest approach to the planet occurred on 25 August 1989. Because this was the last major planet the spacecraft could visit, it was decided to make a close flyby of the moon Triton, regardless of the consequences to the trajectory, similarly to what was done for Voyager 1's encounter with Saturn and its moon Titan. The images relayed back to Earth from Voyager 2 became the basis of a 1989 PBS all-night program, Neptune All Night.

Question: What is the only spacecraft to visit Neptune?

Question: When did a spacecraft get closest to Neptune?

Question: What near Neptune did a spacecraft visit dangerously close?

Question: What program aired on PBS about Neptune?
Passage: After the Voyager 2 flyby mission, the next step in scientific exploration of the Neptunian system, is considered to be a Flagship orbital mission. Such a hypothetical mission is envisioned to be possible at in the late 2020s or early 2030s. However, there have been a couple of discussions to launch Neptune missions sooner. In 2003, there was a proposal in NASA's "Vision Missions Studies" for a "Neptune Orbiter with Probes" mission that does Cassini-level science. Another, more recent proposal was for Argo, a flyby spacecraft to be launched in 2019, that would visit Jupiter, Saturn, Neptune, and a Kuiper belt object. The focus would be on Neptune and its largest moon Triton to be investigated around 2029. The proposed New Horizons 2 mission (which was later scrapped) might also have done a close flyby of the Neptunian system.

Question: When is the next hypothetical mission to Neptune?

Question: What about Neptune did NASA propose in 2003 in their "Vision Missions Studies"?

Question: When will Argo be launched?

Question: What will Argo visit?

Question: When can we expect Argo to visit Triton?
Passage: A railway electrification system supplies electric power to railway trains and trams without an on-board prime mover or local fuel supply. Electrification has many advantages but requires significant capital expenditure. Selection of an electrification system is based on economics of energy supply, maintenance, and capital cost compared to the revenue obtained for freight and passenger traffic. Different systems are used for urban and intercity areas; some electric locomotives can switch to different supply voltages to allow flexibility in operation.

Question: What is of the factors the capital cost of electrification system depends on?

Question: How do some locomotives function in order to be more flexible in operation?

Question: What are two types of revenue obtained through railway transportation?

Question: What is the main disadvantage of railway electrification?
Passage: Electric railways use electric locomotives to haul passengers or freight in separate cars or electric multiple units, passenger cars with their own motors. Electricity is typically generated in large and relatively efficient generating stations, transmitted to the railway network and distributed to the trains. Some electric railways have their own dedicated generating stations and transmission lines but most purchase power from an electric utility. The railway usually provides its own distribution lines, switches and transformers.

Question: What is used to haul passengers cars?

Question: How is electricity being generated for electric locomotives?

Question: What entity provides distribution lines, switches and transformers?
Passage: In comparison to the principal alternative, the diesel engine, electric railways offer substantially better energy efficiency, lower emissions and lower operating costs. Electric locomotives are usually quieter, more powerful, and more responsive and reliable than diesels. They have no local emissions, an important advantage in tunnels and urban areas. Some electric traction systems provide regenerative braking that turns the train's kinetic energy back into electricity and returns it to the supply system to be used by other trains or the general utility grid. While diesel locomotives burn petroleum, electricity is generated from diverse sources including many that do not produce carbon dioxide such as nuclear power and renewable forms including hydroelectric, geothermal, wind and solar.

Question: What is the principal alternative to electric railways?

Question: What locomotives are usually more reliable?

Question: What do some electric traction systems provide?

Question: What type of fuel do diesel locomotives use?

Question: What is one of the sources electricity is being generated from?
Passage: Disadvantages of electric traction include high capital costs that may be uneconomic on lightly trafficked routes; a relative lack of flexibility since electric trains need electrified tracks or onboard supercapacitors and charging infrastructure at stations; and a vulnerability to power interruptions. Different regions may use different supply voltages and frequencies, complicating through service. The limited clearances available under catenaries may preclude efficient double-stack container service. The lethal voltages on contact wires and third rails are a safety hazard to track workers, passengers and trespassers. Overhead wires are safer than third rails, but they are often considered unsightly.

Question: What is a safety hazard to track workers?

Question: What issue can complicate electric railway service?

Question: What is a safer alternative to third rails?

Question: Why overhead wires are not being widely used?
Passage: Railways must operate at variable speeds. Until the mid 1980s this was only practical with the brush-type DC motor, although such DC can be supplied from an AC catenary via on-board electric power conversion. Since such conversion was not well developed in the late 19th century and early 20th century, most early electrified railways used DC and many still do, particularly rapid transit (subways) and trams. Speed was controlled by connecting the traction motors in various series-parallel combinations, by varying the traction motors' fields, and by inserting and removing starting resistances to limit motor current.

Question: What is speed limit for railways?

Question: Why is DC motor being used more than AC type?

Question: What are two types of railway transportation still use DC motor?
Passage: Motors have very little room for electrical insulation so they generally have low voltage ratings. Because transformers (prior to the development of power electronics) cannot step down DC voltages, trains were supplied with a relatively low DC voltage that the motors can use directly. The most common DC voltages are listed in the previous section. Third (and fourth) rail systems almost always use voltages below 1 kV for safety reasons while overhead wires usually use higher voltages for efficiency. ("Low" voltage is relative; even 600 V can be instantly lethal when touched.)

Question: Why do motors have little space for insulation?

Question: Why 1kV voltage is almost always used by rail systems?

Question: What is most common volatage range used by railway system?

Question: Which system uses higher voltages?

Question: Is "low" voltage used by trains safe for people?
Passage: There has, however, been interest among railroad operators in returning to DC use at higher voltages than previously used. At the same voltage, DC often has less loss than AC, and for this reason high-voltage direct current is already used on some bulk power transmission lines. DC avoids the electromagnetic radiation inherent with AC, and on a railway this also reduces interference with signalling and communications and mitigates hypothetical EMF risks. DC also avoids the power factor problems of AC. Of particular interest to railroading is that DC can supply constant power with a single ungrounded wire. Constant power with AC requires three-phase transmission with at least two ungrounded wires. Another important consideration is that mains-frequency 3-phase AC must be carefully planned to avoid unbalanced phase loads. Parts of the system are supplied from different phases on the assumption that the total loads of the 3 phases will even out. At the phase break points between regions supplied from different phases, long insulated supply breaks are required to avoid them being shorted by rolling stock using more than one pantograph at a time. A few railroads have tried 3-phase but its substantial complexity has made single-phase standard practice despite the interruption in power flow that occurs twice every cycle. An experimental 6 kV DC railway was built in the Soviet Union.

Question: What type of electric power garantees lesser loss?

Question: Which type of supply for electric motors creates electromagnetic radiation?

Question: Which type of power does require three-phase transmission?

Question: What can electromagnetic radiation interfere with?

Question: Where was an experimental 6kV DC railway built?
Passage: 1,500 V DC is used in the Netherlands, Japan, Republic Of Indonesia, Hong Kong (parts), Republic of Ireland, Australia (parts), India (around the Mumbai area alone, has been converted to 25 kV AC like the rest of India), France (also using 25 kV 50 Hz AC), New Zealand (Wellington) and the United States (Chicago area on the Metra Electric district and the South Shore Line interurban line). In Slovakia, there are two narrow-gauge lines in the High Tatras (one a cog railway). In Portugal, it is used in the Cascais Line and in Denmark on the suburban S-train system.

Question: What is most common voltage for DC supply?

Question: How many narrow-gauge lines in Slovakia?

Question: What railway line is DC being used in Portugal?

Question: Where in India line has been converted to AC?