Here is a question about this article: The first railway line in Galicia was inaugurated 15 September 1873. It ran from O Carril, Vilagarcia de Arousa to Cornes, Conxo, Santiago de Compostela. A second line was inaugurated in 1875, connecting A Coruna and Lugo. In 1883, Galicia was first connected by rail to the rest of Spain, by way of O Barco de Valdeorras. Galicia today has roughly 1,100 kilometres (680 mi) of rail lines. Several 1,668 mm (5 ft 5 2132 in) Iberian gauge lines operated by Adif and Renfe Operadora connect all the important Galician cities. A 1,000 mm (3 ft 3 38 in) metre gauge line operated by FEVE connects Ferrol to Ribadeo and Oviedo. The only electrified line is the Ponferrada-Monforte de Lemos-Ourense-Vigo line. Several high-speed rail lines are under construction. Among these are the Olmedo-Zamora-Galicia high-speed rail line that opened partly in 2011, and the AVE Atlantic Axis route, which will connect all of the major Galician Atlantic coast cities A Coruna, Santiago de Compostela, Pontevedra and Vigo to Portugal. Another projected AVE line will connect Ourense to Pontevedra and Vigo.
What is the answer to this question: What is the name of its only electrified railway?
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So... Ponferrada-Monforte de Lemos-Ourense-Vigo

Here is a question about this article: The theory of special relativity finds a convenient formulation in Minkowski spacetime, a mathematical structure that combines three dimensions of space with a single dimension of time. In this formalism, distances in space can be measured by how long light takes to travel that distance, e.g., a light-year is a measure of distance, and a meter is now defined in terms of how far light travels in a certain amount of time. Two events in Minkowski spacetime are separated by an invariant interval, which can be either space-like, light-like, or time-like. Events that have a time-like separation cannot be simultaneous in any frame of reference, there must be a temporal component (and possibly a spatial one) to their separation. Events that have a space-like separation will be simultaneous in some frame of reference, and there is no frame of reference in which they do not have a spatial separation. Different observers may calculate different distances and different time intervals between two events, but the invariant interval between the events is independent of the observer (and his velocity).
What is the answer to this question: The invariant interval that separates two events in Minkowski spacetime can either be what?
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So... space-like, light-like, or time-like

Here is a question about this article: There are a number of aids available to pilots, though not all airports are equipped with them. A visual approach slope indicator (VASI) helps pilots fly the approach for landing. Some airports are equipped with a VHF omnidirectional range (VOR) to help pilots find the direction to the airport. VORs are often accompanied by a distance measuring equipment (DME) to determine the distance to the VOR. VORs are also located off airports, where they serve to provide airways for aircraft to navigate upon. In poor weather, pilots will use an instrument landing system (ILS) to find the runway and fly the correct approach, even if they cannot see the ground. The number of instrument approaches based on the use of the Global Positioning System (GPS) is rapidly increasing and may eventually be the primary means for instrument landings.
What is the answer to this question: What instruments do pilots use to find the runway and fly the correct approach, even if they cannot see the ground?
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So...
instrument landing system