sentence-transformers/squad huggingface dataset:
Passage: The most accurate timekeeping devices are atomic clocks, which are accurate to seconds in many millions of years, and are used to calibrate other clocks and timekeeping instruments. Atomic clocks use the frequency of electronic transitions in certain atoms to measure the second. One of the most common atoms used is caesium, most modern atomic clocks probe caesium with microwaves to determine the frequency of these electron vibrations. Since 1967, the International System of Measurements bases its unit of time, the second, on the properties of caesium atoms. SI defines the second as 9,192,631,770 cycles of the radiation that corresponds to the transition between two electron spin energy levels of the ground state of the 133Cs atom.

Question: Which timekeeping devices are the most accurate?

Question: What method do atomic clocks use to measure seconds?

Question: Which system bases its unit of time on the properties of caesium?

Question: How long has the International System of Measurements based the second on caesium?
Passage: Greenwich Mean Time (GMT) is an older standard, adopted starting with British railways in 1847. Using telescopes instead of atomic clocks, GMT was calibrated to the mean solar time at the Royal Observatory, Greenwich in the UK. Universal Time (UT) is the modern term for the international telescope-based system, adopted to replace "Greenwich Mean Time" in 1928 by the International Astronomical Union. Observations at the Greenwich Observatory itself ceased in 1954, though the location is still used as the basis for the coordinate system. Because the rotational period of Earth is not perfectly constant, the duration of a second would vary if calibrated to a telescope-based standard like GMT or UT—in which a second was defined as a fraction of a day or year. The terms "GMT" and "Greenwich Mean Time" are sometimes used informally to refer to UT or UTC.

Question: Which standard of time started with British Railways?

Question: When was GMT adopted by British Railways?

Question: GMT used what instead of atomic clocks?

Question: When did observations at the Greenwich Observatory cease?

Question: The terms GMT and Greenwich Mean Time are also used informally to refer to what?
Passage: Two distinct viewpoints on time divide many prominent philosophers. One view is that time is part of the fundamental structure of the universe, a dimension in which events occur in sequence. Sir Isaac Newton subscribed to this realist view, and hence it is sometimes referred to as Newtonian time. An opposing view is that time does not refer to any kind of actually existing dimension that events and objects "move through", nor to any entity that "flows", but that it is instead an intellectual concept (together with space and number) that enables humans to sequence and compare events. This second view, in the tradition of Gottfried Leibniz and Immanuel Kant, holds that space and time "do not exist in and of themselves, but ... are the product of the way we represent things", because we can know objects only as they appear to us.

Question: How many main viewpoints divide many philosophers?

Question: The realist view states that time is part of the fundamental structure of what?

Question: The realist view is sometimes referred to as what?

Question: The opposing view states that time is an intellectual concept that allows people to what?
Passage: The Vedas, the earliest texts on Indian philosophy and Hindu philosophy dating back to the late 2nd millennium BC, describe ancient Hindu cosmology, in which the universe goes through repeated cycles of creation, destruction and rebirth, with each cycle lasting 4,320 million years. Ancient Greek philosophers, including Parmenides and Heraclitus, wrote essays on the nature of time. Plato, in the Timaeus, identified time with the period of motion of the heavenly bodies. Aristotle, in Book IV of his Physica defined time as 'number of movement in respect of the before and after'.

Question: What are the earliest texts of Indian/Hindu philosophy?

Question: How long ago are the earliest texts of Indian/Hindu philosophy dated?

Question: How long does each cycle of birth and destruction of the universe last according to Ancient Hindu texts?

Question: Which ancient Greek philosophers wrote essays on the concept of time?

Question: Aristotle defined time as "number of movement in respect of the before and after" in which book?
Passage: In Book 11 of his Confessions, St. Augustine of Hippo ruminates on the nature of time, asking, "What then is time? If no one asks me, I know: if I wish to explain it to one that asketh, I know not." He begins to define time by what it is not rather than what it is, an approach similar to that taken in other negative definitions. However, Augustine ends up calling time a “distention” of the mind (Confessions 11.26) by which we simultaneously grasp the past in memory, the present by attention, and the future by expectation.

Question: Who commented on the nature of time in Book 11 of his confessions?

Question: By what does St. Augustine of Hippo begin to define time?

Question: What does Augustine call time in Confessions 11.26?
Passage: Immanuel Kant, in the Critique of Pure Reason, described time as an a priori intuition that allows us (together with the other a priori intuition, space) to comprehend sense experience. With Kant, neither space nor time are conceived as substances, but rather both are elements of a systematic mental framework that necessarily structures the experiences of any rational agent, or observing subject. Kant thought of time as a fundamental part of an abstract conceptual framework, together with space and number, within which we sequence events, quantify their duration, and compare the motions of objects. In this view, time does not refer to any kind of entity that "flows," that objects "move through," or that is a "container" for events. Spatial measurements are used to quantify the extent of and distances between objects, and temporal measurements are used to quantify the durations of and between events. Time was designated by Kant as the purest possible schema of a pure concept or category.

Question: In what did Immanuel Kant describe time as a priori intuition that allows humankind to understand sense experience?

Question: What did Kant portray space and time to be?

Question: Kant thought of time as a fundamental part of what?

Question: What type of measurements are used to quantify the duration of events?

Question: What type of measurements are used to quantify the distances between objects?
Passage: According to Martin Heidegger we do not exist inside time, we are time. Hence, the relationship to the past is a present awareness of having been, which allows the past to exist in the present. The relationship to the future is the state of anticipating a potential possibility, task, or engagement. It is related to the human propensity for caring and being concerned, which causes "being ahead of oneself" when thinking of a pending occurrence. Therefore, this concern for a potential occurrence also allows the future to exist in the present. The present becomes an experience, which is qualitative instead of quantitative. Heidegger seems to think this is the way that a linear relationship with time, or temporal existence, is broken or transcended. We are not stuck in sequential time. We are able to remember the past and project into the future—we have a kind of random access to our representation of temporal existence; we can, in our thoughts, step out of (ecstasis) sequential time.

Question: Who suggested that humankind does not exist inside time, but is time?

Question: The relationship to the future is the state of anticipating what?

Question: What is considered a qualitative experience rather than a quantitative one?

Question: According to Heidegger, what can we do, in our thoughts?
Passage: 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).

Question: Minkowski spacetime combines the three dimensions of space with what?

Question: In Minkowski spacetime, how can distances in space be measured?

Question: What are two events in Minkowski spacetime separated by?

Question: The invariant interval between events is independent of what?

Question: The invariant interval that separates two events in Minkowski spacetime can either be what?
Passage: In non-relativistic classical mechanics, Newton's concept of "relative, apparent, and common time" can be used in the formulation of a prescription for the synchronization of clocks. Events seen by two different observers in motion relative to each other produce a mathematical concept of time that works sufficiently well for describing the everyday phenomena of most people's experience. In the late nineteenth century, physicists encountered problems with the classical understanding of time, in connection with the behavior of electricity and magnetism. Einstein resolved these problems by invoking a method of synchronizing clocks using the constant, finite speed of light as the maximum signal velocity. This led directly to the result that observers in motion relative to one another measure different elapsed times for the same event.

Question: What Newtonian concept can be used in the formulation of an idea for the synchronization of clocks?

Question: In which century did physicists encounter problems with the understanding of time?

Question: The behavior of which two phenomena caused physicists to encounter problems with their understanding of time in the late 19th century?

Question: Which famous scientist resolved these issues?
Passage: Time has historically been closely related with space, the two together merging into spacetime in Einstein's special relativity and general relativity. According to these theories, the concept of time depends on the spatial reference frame of the observer, and the human perception as well as the measurement by instruments such as clocks are different for observers in relative motion. For example, if a spaceship carrying a clock flies through space at (very nearly) the speed of light, its crew does not notice a change in the speed of time on board their vessel because everything traveling at the same speed slows down at the same rate (including the clock, the crew's thought processes, and the functions of their bodies). However, to a stationary observer watching the spaceship fly by, the spaceship appears flattened in the direction it is traveling and the clock on board the spaceship appears to move very slowly.

Question: Historically, time has been closely related with what?

Question: In which of Einstein's two theories do time and space merge into spacetime?

Question: According to Einsteins two relativity theories, the concept of time depends on what?

Question: A crew in a spaceship travelling nearly the speed of light will not notice the change in what?

Question: How will the above mentioned spaceship appear to a stationary observer?
Passage: On the other hand, the crew on board the spaceship also perceives the observer as slowed down and flattened along the spaceship's direction of travel, because both are moving at very nearly the speed of light relative to each other. Because the outside universe appears flattened to the spaceship, the crew perceives themselves as quickly traveling between regions of space that (to the stationary observer) are many light years apart. This is reconciled by the fact that the crew's perception of time is different from the stationary observer's; what seems like seconds to the crew might be hundreds of years to the stationary observer. In either case, however, causality remains unchanged: the past is the set of events that can send light signals to an entity and the future is the set of events to which an entity can send light signals.

Question: How does the crew on board the spaceship perceive the stationary observer?

Question: The crew's perception of what is different from a stationary observer?

Question: What the crew perceives as seconds might be seen as how long to a stationary observer?

Question: What remains unchanged in both the cases of the spaceship crew and of the stationary observer?
Passage: Einstein showed in his thought experiments that people travelling at different speeds, while agreeing on cause and effect, measure different time separations between events, and can even observe different chronological orderings between non-causally related events. Though these effects are typically minute in the human experience, the effect becomes much more pronounced for objects moving at speeds approaching the speed of light. Many subatomic particles exist for only a fixed fraction of a second in a lab relatively at rest, but some that travel close to the speed of light can be measured to travel farther and survive much longer than expected (a muon is one example). According to the special theory of relativity, in the high-speed particle's frame of reference, it exists, on the average, for a standard amount of time known as its mean lifetime, and the distance it travels in that time is zero, because its velocity is zero. Relative to a frame of reference at rest, time seems to "slow down" for the particle. Relative to the high-speed particle, distances seem to shorten. Einstein showed how both temporal and spatial dimensions can be altered (or "warped") by high-speed motion.

Question: Who showed, in his thought experiments, that people travelling at different speeds measured time differently?

Question: In what case do these effects become much more noticeable?

Question: How long do most subatomic particles exist for in a lab?

Question: Einstein showed how what could be altered by high speed motion?
Passage: Time appears to have a direction—the past lies behind, fixed and immutable, while the future lies ahead and is not necessarily fixed. Yet for the most part the laws of physics do not specify an arrow of time, and allow any process to proceed both forward and in reverse. This is generally a consequence of time being modeled by a parameter in the system being analyzed, where there is no "proper time": the direction of the arrow of time is sometimes arbitrary. Examples of this include the Second law of thermodynamics, which states that entropy must increase over time (see Entropy); the cosmological arrow of time, which points away from the Big Bang, CPT symmetry, and the radiative arrow of time, caused by light only traveling forwards in time (see light cone). In particle physics, the violation of CP symmetry implies that there should be a small counterbalancing time asymmetry to preserve CPT symmetry as stated above. The standard description of measurement in quantum mechanics is also time asymmetric (see Measurement in quantum mechanics).

Question: What laws do not specify an arrow of time?

Question: The standard description of measurement in quantum mechanics is what?

Question: The direction of the arrow of time is sometimes what?

Question: Which law states that entropy must increase over time?

Question: The violation of what implies that there should be a small counterbalancing time asymmetry?
Passage: Stephen Hawking in particular has addressed a connection between time and the Big Bang. In A Brief History of Time and elsewhere, Hawking says that even if time did not begin with the Big Bang and there were another time frame before the Big Bang, no information from events then would be accessible to us, and nothing that happened then would have any effect upon the present time-frame. Upon occasion, Hawking has stated that time actually began with the Big Bang, and that questions about what happened before the Big Bang are meaningless. This less-nuanced, but commonly repeated formulation has received criticisms from philosophers such as Aristotelian philosopher Mortimer J. Adler.

Question: In which publication does Hawking say that any events that existed before the Big Bang would not be accessible to us?

Question: Stephen Hawking makes a connection between time and what?

Question: What does Hawking suggest started with the big bang?

Question: Hawking also states that questions about what happened before the Big Bang are what?

Question: Which philosopher has criticized Hawking's formulation?
Passage: While the Big Bang model is well established in cosmology, it is likely to be refined in the future. Little is known about the earliest moments of the universe's history. The Penrose–Hawking singularity theorems require the existence of a singularity at the beginning of cosmic time. However, these theorems assume that general relativity is correct, but general relativity must break down before the universe reaches the Planck temperature, and a correct treatment of quantum gravity may avoid the singularity.

Question: The Big Bang model is solidly established in what?

Question: How much is known about the early states of the universe?

Question: Which theorems require the existence of a singularity at the beginning of time?

Question: These theorems have to assume what theory is correct?

Question: These theorems state that general relatively must break down before what?
Passage: Time travel is the concept of moving backwards or forwards to different points in time, in a manner analogous to moving through space, and different from the normal "flow" of time to an earthbound observer. In this view, all points in time (including future times) "persist" in some way. Time travel has been a plot device in fiction since the 19th century. Traveling backwards in time has never been verified, presents many theoretic problems, and may be an impossibility. Any technological device, whether fictional or hypothetical, that is used to achieve time travel is known as a time machine.

Question: How long has time travel been a topic in science fiction?

Question: Traveling which direction in time has never been verified and presents many problems?

Question: A time machine is known as any technological devise that is used for what purpose?
Passage: Another solution to the problem of causality-based temporal paradoxes is that such paradoxes cannot arise simply because they have not arisen. As illustrated in numerous works of fiction, free will either ceases to exist in the past or the outcomes of such decisions are predetermined. As such, it would not be possible to enact the grandfather paradox because it is a historical fact that your grandfather was not killed before his child (your parent) was conceived. This view doesn't simply hold that history is an unchangeable constant, but that any change made by a hypothetical future time traveler would already have happened in his or her past, resulting in the reality that the traveler moves from. More elaboration on this view can be found in the Novikov self-consistency principle.

Question: What is another solution to the problem of temporal paradoxes?

Question: In several works of fiction, what ceases to exist in the past which causes paradoxes not to arise?

Question: What paradox cannot be enacted because it is a fact that your grandfather was not killed before your parent was conceived?

Question: What principle elaborates more on the view described?
Passage: Psychoactive drugs can impair the judgment of time. Stimulants can lead both humans and rats to overestimate time intervals, while depressants can have the opposite effect. The level of activity in the brain of neurotransmitters such as dopamine and norepinephrine may be the reason for this. Such chemicals will either excite or inhibit the firing of neurons in the brain, with a greater firing rate allowing the brain to register the occurrence of more events within a given interval (speed up time) and a decreased firing rate reducing the brain's capacity to distinguish events occurring within a given interval (slow down time).

Question: What type of drugs can impair the judgement of time?

Question: Stimulants lead humans to overestimate what?

Question: What causes humans to underestimate time intervals?

Question: The level of what is the reason stimulants and depressants change human perceptions of time?

Question: Such chemicals do what to the firing of the brain's neurons?
Passage: The use of time is an important issue in understanding human behavior, education, and travel behavior. Time-use research is a developing field of study. The question concerns how time is allocated across a number of activities (such as time spent at home, at work, shopping, etc.). Time use changes with technology, as the television or the Internet created new opportunities to use time in different ways. However, some aspects of time use are relatively stable over long periods of time, such as the amount of time spent traveling to work, which despite major changes in transport, has been observed to be about 20–30 minutes one-way for a large number of cities over a long period.

Question: The use of time is important in understanding what?

Question: What is a developing field of time related study?

Question: Time use is always changing with advances in what?

Question: Travelling to work has been observed to be about how long for a large number of cities over a long period?
Passage: A sequence of events, or series of events, is a sequence of items, facts, events, actions, changes, or procedural steps, arranged in time order (chronological order), often with causality relationships among the items. Because of causality, cause precedes effect, or cause and effect may appear together in a single item, but effect never precedes cause. A sequence of events can be presented in text, tables, charts, or timelines. The description of the items or events may include a timestamp. A sequence of events that includes the time along with place or location information to describe a sequential path may be referred to as a world line.

Question: What may the description of events include?

Question: What never precedes cause because of causality?

Question: A sequence of events used to describe a sequential path can be referred to as what?

Question: In what ways can a sequence of events be presented?

Question: What is another way of phrasing "time order"?