Timeline of the far future
While the future can never be predicted with absolute certainty, present understanding in various scientific fields allows for the prediction of some far-future events, if only in the broadest outline. These fields include astrophysics, which has revealed how planets and stars form and die. All projections of the future of the Earth, the Solar System, the universe must account for the second law of thermodynamics, which states that entropy, or a loss of the energy available to do work, must rise over time. Stars will exhaust their supply of hydrogen fuel and burn out. Close encounters between astronomical objects gravitationally fling planets from their star systems, star systems from galaxies. Physicists expect that matter itself will come under the influence of radioactive decay, as the most stable materials break apart into subatomic particles. Current data suggest that the universe has a flat geometry, thus will not collapse in on itself after a finite time, the infinite future allows for the occurrence of a number of massively improbable events, such as the formation of Boltzmann brains.
The timelines displayed here cover events from the beginning of the 11th millennium to the furthest reaches of future time. A number of alternative future events are listed to account for questions still unresolved, such as whether humans will become extinct, whether protons decay, whether the earth survives when the sun expands to become a red giant. To date five spacecraft are on trajectories which will take them out of the Solar System and into interstellar space. Barring an unlikely collision with some object, the craft should persist indefinitely. Rare astronomical events beginning in the 11th millennium AD will be: This assumes that these calendars continue in use, without further adjustments. For graphical, logarithmic timelines of these events see: Graphical timeline of the universe Graphical timeline of the Stelliferous Era Graphical timeline from Big Bang to Heat Death Adams, Fred C. "Long term astrophysical processes", in Bostrom, Nick. Global catastrophic risks, Oxford University Press, ISBN 978-0-19-857050-9.
Brownlee, Donald E. "Planetary habitability on astronomical time scales", in Schrijver, Carolus J..
The Hebrew or Jewish calendar is a lunisolar calendar used today predominantly for Jewish religious observances. It determines the dates for Jewish holidays and the appropriate public reading of Torah portions and daily Psalm readings, among many ceremonial uses. In Israel, it is used for religious purposes, provides a time frame for agriculture and is an official calendar for civil purposes, although the latter usage has been declining in favor of the Gregorian calendar; the present Hebrew calendar is the product including a Babylonian influence. Until the Tannaitic period, the calendar employed a new crescent moon, with an additional month added every two or three years to correct for the difference between twelve lunar months and the solar year; the year in which it was added was based on observation of natural agriculture-related events in ancient Israel. Through the Amoraic period and into the Geonic period, this system was displaced by the mathematical rules used today; the principles and rules were codified by Maimonides in the Mishneh Torah in the 12th century.
Maimonides' work replaced counting "years since the destruction of the Temple" with the modern creation-era Anno Mundi. The Hebrew lunar year is about eleven days shorter than the solar year and uses the 19-year Metonic cycle to bring it into line with the solar year, with the addition of an intercalary month every two or three years, for a total of seven times per 19 years. With this intercalation, the average Hebrew calendar year is longer by about 6 minutes and 40 seconds than the current mean tropical year, so that every 217 years the Hebrew calendar will fall a day behind the current mean tropical year; the era used. As with Anno Domini, the words or abbreviation for Anno Mundi for the era should properly precede the date rather than follow it. AM 5779 began at sunset on 9 September 2018 and will end at sunset on 29 September 2019; the Jewish day is of no fixed length. The Jewish day is modeled on the reference to "...there was evening and there was morning..." in the creation account in the first chapter of Genesis.
Based on the classic rabbinic interpretation of this text, a day in the rabbinic Hebrew calendar runs from sunset to the next sunset. Halachically, a day ends and a new one starts when three stars are visible in the sky; the time between true sunset and the time when the three stars are visible is known as'bein hashmashot', there are differences of opinion as to which day it falls into for some uses. This may be relevant, for example, in determining the date of birth of a child born during that gap. There is no clock in the Jewish scheme. Though the civil clock, including the one in use in Israel, incorporates local adoptions of various conventions such as time zones, standard times and daylight saving, these have no place in the Jewish scheme; the civil clock is used only as a reference point – in expressions such as: "Shabbat starts at...". The steady progression of sunset around the world and seasonal changes results in gradual civil time changes from one day to the next based on observable astronomical phenomena and not on man-made laws and conventions.
In Judaism, an hour is defined as 1/12 of the time from sunrise to sunset, so, during the winter, an hour can be much less than 60 minutes, during the summer, it can be much more than 60 minutes. This proportional hour is known as a sha'ah z'manit. A Jewish hour is divided into parts. A part is 1/18 minute; the ultimate ancestor of the helek was a small Babylonian time period called a barleycorn, itself equal to 1/72 of a Babylonian time degree. These measures are not used for everyday purposes. Instead of the international date line convention, there are varying opinions as to where the day changes. One opinion uses the antimeridian of Jerusalem. Other opinions exist as well; the weekdays proceed to Saturday, Shabbat. Since some calculations use division, a remainder of 0 signifies Saturday. While calculations of days and years are based on fixed hours equal to 1/24 of a day, the beginning of each halachic day is based on the local time of sunset; the end of the Shabbat and other Jewish holidays is based on nightfall which occurs some amount of time 42 to 72 minutes, after sunset.
According to Maimonides, nightfall occurs. By the 17th century, this had become three-second-magnitude stars; the modern definition is when the center of the sun is 7° below the geometric horizon, somewhat than civil twilight at 6°. The beginning of the daytime portion of each day is determined both by sunrise. Most halachic times are based on some combination of these four times and vary from day to day throughout the year and vary depending on location; the daytime hours are divided into Sha'oth Zemaniyoth or "Halachic hours" by taking the time between sunrise and sunset or between dawn and nightfall and dividing it into 12 equal hours. The nighttime hours are s
The future is the time after the present. Its arrival is considered inevitable due to the laws of physics. Due to the apparent nature of reality and the unavoidability of the future, everything that exists and will exist can be categorized as either permanent, meaning that it will exist forever, or temporary, meaning that it will end. In the Occidental view, which uses a linear conception of time, the future is the portion of the projected time line, anticipated to occur. In special relativity, the future is considered the future light cone. In the philosophy of time, presentism is the belief that only the present exists and the future and the past are unreal. Religions consider the future when they address issues such as karma, life after death, eschatologies that study what the end of time and the end of the world will be. Religious figures such as prophets and diviners have claimed to see into the future. Future studies, or futurology, is the science and practice of postulating possible futures.
Modern practitioners stress the importance of alternative and plural futures, rather than one monolithic future, the limitations of prediction and probability, versus the creation of possible and preferable futures. The concept of the future has been explored extensively in cultural production, including art movements and genres devoted to its elucidation, such as the 20th century movement futurism. In physics, time is a fourth dimension. Physicists argue that spacetime can be understood as a sort of stretchy fabric that bends due to forces such as gravity. In classical physics the future is just a half of the timeline, the same for all observers. In special relativity the flow of time is relative to the observer's frame of reference; the faster an observer is traveling away from a reference object, the slower that object seems to move through time. Hence, future is not an objective notion anymore. A more significant notion is the future light cone. While a person can move backwards or forwards in the three spatial dimensions, many physicists argue you are only able to move forward in time.
One of the outcomes of Special Relativity Theory is that a person can travel into the future by traveling at high speeds. While this effect is negligible under ordinary conditions, space travel at high speeds can change the flow of time considerably; as depicted in many science fiction stories and movies, a person traveling for a short time at near light speed will return to an Earth, many years in the future. Some physicists claim that by using a wormhole to connect two regions of spacetime a person could theoretically travel in time. Physicist Michio Kaku points out that to power this hypothetical time machine and "punch a hole into the fabric of space-time", it would require the energy of a star. Another theory is. In the philosophy of time, presentism is the belief that only the present exists, the future and past are unreal. Past and future "entities" are construed as logical fictions; the opposite of presentism is'eternalism', the belief that things in the past and things yet to come exist eternally.
Another view is sometimes called the'growing block' theory of time—which postulates that the past and present exist, but the future does not. Presentism is compatible with Galilean relativity, in which time is independent of space, but is incompatible with Lorentzian/Einsteinian relativity in conjunction with certain other philosophical theses that many find uncontroversial. Saint Augustine proposed that the present is a knife edge between the past and the future and could not contain any extended period of time. Contrary to Saint Augustine, some philosophers propose that conscious experience is extended in time. For instance, William James said that time is "...the short duration of which we are and incessantly sensible." Augustine proposed that God is outside of present for all times, in eternity. Other early philosophers who were presentists include the Buddhists. A leading scholar from the modern era on Buddhist philosophy is Stcherbatsky, who has written extensively on Buddhist presentism: Human behavior is known to encompass anticipation of the future.
Anticipatory behavior can be the result of a psychological outlook toward the future, for examples optimism and hope. Optimism is an outlook on life such. People would say, it is the philosophical opposite of pessimism. Optimists believe that people and events are inherently good, so that most situations work out in the end for the best. Hope is a belief in a positive outcome related to circumstances in one's life. Hope implies a certain amount of despair, wishing, suffering or perseverance — i.e. believing that a better or positive outcome is possible when there is some evidence to the contrary. "Hopefulness" is somewhat different from optimism in that hope is an emotional state, whereas optimism is a conclusion reached through a deliberate thought pattern that leads to a positive attitude. Pessimism as stated, it is the tendency to see, anticipate, or emphasize only bad or undesirable outcomes, results, or problems. The word originates in Latin from Pessimus meaning Malus meaning bad. Religions consider the future when they address issues such as karma, life after death, eschatologies that study what the end of time and the end of the world will be.
The Ancient Greek language includes the forms of Greek used in Ancient Greece and the ancient world from around the 9th century BCE to the 6th century CE. It is roughly divided into the Archaic period, Classical period, Hellenistic period, it is succeeded by medieval Greek. Koine is regarded as a separate historical stage of its own, although in its earliest form it resembled Attic Greek and in its latest form it approaches Medieval Greek. Prior to the Koine period, Greek of the classic and earlier periods included several regional dialects. Ancient Greek was the language of Homer and of fifth-century Athenian historians and philosophers, it has contributed many words to English vocabulary and has been a standard subject of study in educational institutions of the Western world since the Renaissance. This article contains information about the Epic and Classical periods of the language. Ancient Greek was a pluricentric language, divided into many dialects; the main dialect groups are Attic and Ionic, Aeolic and Doric, many of them with several subdivisions.
Some dialects are found in standardized literary forms used in literature, while others are attested only in inscriptions. There are several historical forms. Homeric Greek is a literary form of Archaic Greek used in the epic poems, the "Iliad" and "Odyssey", in poems by other authors. Homeric Greek had significant differences in grammar and pronunciation from Classical Attic and other Classical-era dialects; the origins, early form and development of the Hellenic language family are not well understood because of a lack of contemporaneous evidence. Several theories exist about what Hellenic dialect groups may have existed between the divergence of early Greek-like speech from the common Proto-Indo-European language and the Classical period, they differ in some of the detail. The only attested dialect from this period is Mycenaean Greek, but its relationship to the historical dialects and the historical circumstances of the times imply that the overall groups existed in some form. Scholars assume that major Ancient Greek period dialect groups developed not than 1120 BCE, at the time of the Dorian invasion—and that their first appearances as precise alphabetic writing began in the 8th century BCE.
The invasion would not be "Dorian" unless the invaders had some cultural relationship to the historical Dorians. The invasion is known to have displaced population to the Attic-Ionic regions, who regarded themselves as descendants of the population displaced by or contending with the Dorians; the Greeks of this period believed there were three major divisions of all Greek people—Dorians and Ionians, each with their own defining and distinctive dialects. Allowing for their oversight of Arcadian, an obscure mountain dialect, Cypriot, far from the center of Greek scholarship, this division of people and language is quite similar to the results of modern archaeological-linguistic investigation. One standard formulation for the dialects is: West vs. non-west Greek is the strongest marked and earliest division, with non-west in subsets of Ionic-Attic and Aeolic vs. Arcadocypriot, or Aeolic and Arcado-Cypriot vs. Ionic-Attic. Non-west is called East Greek. Arcadocypriot descended more from the Mycenaean Greek of the Bronze Age.
Boeotian had come under a strong Northwest Greek influence, can in some respects be considered a transitional dialect. Thessalian had come under Northwest Greek influence, though to a lesser degree. Pamphylian Greek, spoken in a small area on the southwestern coast of Anatolia and little preserved in inscriptions, may be either a fifth major dialect group, or it is Mycenaean Greek overlaid by Doric, with a non-Greek native influence. Most of the dialect sub-groups listed above had further subdivisions equivalent to a city-state and its surrounding territory, or to an island. Doric notably had several intermediate divisions as well, into Island Doric, Southern Peloponnesus Doric, Northern Peloponnesus Doric; the Lesbian dialect was Aeolic Greek. All the groups were represented by colonies beyond Greece proper as well, these colonies developed local characteristics under the influence of settlers or neighbors speaking different Greek dialects; the dialects outside the Ionic group are known from inscriptions, notable exceptions being: fragments of the works of the poet Sappho from the island of Lesbos, in Aeolian, the poems of the Boeotian poet Pindar and other lyric poets in Doric.
After the conquests of Alexander the Great in the late 4th century BCE, a new international dialect known as Koine or Common Greek developed based on Attic Greek, but with influence from other dialects. This dialect replaced most of the older dialects, although Doric dialect has survived in the Tsakonian language, spoken in the region of modern Sparta. Doric has passed down its aorist terminations into most verbs of Demotic Greek. By about the 6th century CE, the Koine had metamorphosized into Medieval Greek. Ancient Macedonian was an Indo-European language at least related to Greek, but its exact relationship is unclear because of insufficient data: a dialect of Greek; the Macedonian dialect (or l
A week is a time unit equal to seven days. It is the standard time period used for cycles of rest days in most parts of the world alongside—although not part of—the Gregorian calendar. In many languages, the days of the week are named after classical gods of a pantheon. In English, the names are Sunday, Tuesday, Thursday and Saturday. ISO 8601 includes the ISO week date system, a numbering system for weeks within a given year – each week begins on a Monday and is associated with the year that contains that week's Thursday. ISO 8601 assigns numbers to the days of the week; the term "week" is sometimes expanded to refer to other time units comprising a few days, such as the nundinal cycle of the ancient Roman calendar, the "work week", or "school week" referring only to the days spent on those activities. The English word week comes from the Old English wice from a Common Germanic *wikōn-, from a root *wik- "turn, change"; the Germanic word had a wider meaning prior to the adoption of the Roman calendar "succession series", as suggested by Gothic wikō translating taxis "order" in Luke 1:8.
The seven-day week is named in many languages by a word derived from "seven". The archaism sennight preserves the old Germanic practice of reckoning time by nights, as in the more common fortnight. Hebdomad and hebdomadal week both derive from the Greek hebdomás; the obsolete septimane is cognate with the Romance terms derived from Latin septimana. Slavic has a formation *tъdьnь, from *tъ "this" + *dьnь "day". Chinese has 星期, as it were "planetary time unit". A week is defined as an interval of seven days, so that technically, except at daylight saving time transitions or leap seconds, 1 week = 7 days = 168 hours = 10,080 minutes = 604,800 seconds. With respect to the Gregorian calendar: 1 Gregorian calendar year = 52 weeks + 1 day 1 week = 1600⁄6957 ≈ 22.9984% of an average Gregorian monthIn a Gregorian mean year, there are 365.2425 days, thus 52 71⁄400 or 52.1775 weeks. There are 20,871 weeks in 400 Gregorian years, so 11 April 1619 was a Thursday just as was 11 April 2019. Relative to the path of the Moon, a week is 23.659% of an average lunation or 94.637% of an average quarter lunation.
The system of dominical letters has been used to facilitate calculation of the day of week. The day of the week can be calculated given a date's Julian day number: Adding one to the remainder after dividing the Julian day number by seven yields that date's ISO 8601 day of the week; the days of the week were named for the classical planets. This naming system persisted alongside an "ecclesiastical" tradition of numbering the days, in ecclesiastical Latin beginning with dominica as the first day; the Greco-Roman gods associated with the classical planets were rendered in their interpretatio germanica at some point during the late Roman Empire, yielding the Germanic tradition of names based on indigenous deities. The ordering of the weekday names is not the classical order of the planets. Instead, the planetary hours systems resulted in succeeding days being named for planets that are three places apart in their traditional listing; this characteristic was discussed in Plutarch in a treatise written in c.
AD 100, reported to have addressed the question of Why are the days named after the planets reckoned in a different order from the actual order?. An ecclesiastical, non-astrological, system of numbering the days of the week was adopted in Late Antiquity; this model seems to have influenced the designation of Wednesday as "mid-week" in Old High German and Old Church Slavonic. Old Church Slavonic may have modeled the name of Monday, понєдѣльникъ, after the Latin feria secunda; the ecclesiastical system became prevalent in Eastern Christianity, but in the Latin West it remains extant only in modern Icelandic and Portuguese. A continuous seven-day cycle that runs throughout history paying no attention whatsoever to the phases of the moon was first practised in Judaism, dated to the 6th century BC at the latest. There are several hypotheses concerning the origin of the biblical seven-day cycle. Friedrich Delitzsch and others suggested that the seven-day week being a quarter of a lunation is the implicit astronomical origin of the seven-day week, indeed the Babylonian calendar used intercalary days to synchronize the last week of a month with the new moon.
According to this theory, the Jewish week was adopted from the Babylonians while removing the moon-dependency. However, Niels-Erik Andreasen, Jeffrey H. Tigay, others claimed that the Biblical Sabbath is mentioned as a day of rest in some of the earliest layers of the Pentateuch dated to the 9th century BC at the latest, centuries before Judea's Babylonian exile, they find the resemblance between the Biblical Sabbat
A day is the period of time during which the Earth completes one rotation around its axis. A solar day is the length of time which elapses between the Sun reaching its highest point in the sky two consecutive times. In 1960, the second was redefined in terms of the orbital motion of the Earth in year 1900, was designated the SI base unit of time; the unit of measurement "day", was symbolized d. In 1967, the second and so the day were redefined by atomic electron transition. A civil day is 86,400 seconds, plus or minus a possible leap second in Coordinated Universal Time, plus or minus an hour in those locations that change from or to daylight saving time. Day can be defined as each of the twenty-four-hour periods, reckoned from one midnight to the next, into which a week, month, or year is divided, corresponding to a rotation of the earth on its axis; however its use depends on its context, for example when people say'day and night','day' will have a different meaning. It will mean the interval of light between two successive nights.
However, in order to be clear when using'day' in that sense, "daytime" should be used to distinguish it from "day" referring to a 24-hour period. The word day may refer to a day of the week or to a calendar date, as in answer to the question, "On which day?" The life patterns of humans and many other species are related to Earth's solar day and the day-night cycle. Several definitions of this universal human concept are used according to context and convenience. Besides the day of 24 hours, the word day is used for several different spans of time based on the rotation of the Earth around its axis. An important one is the solar day, defined as the time it takes for the Sun to return to its culmination point; because celestial orbits are not circular, thus objects travel at different speeds at various positions in their orbit, a solar day is not the same length of time throughout the orbital year. Because the Earth orbits the Sun elliptically as the Earth spins on an inclined axis, this period can be up to 7.9 seconds more than 24 hours.
In recent decades, the average length of a solar day on Earth has been about 86 400.002 seconds and there are about 365.2422 solar days in one mean tropical year. Ancient custom has a new day start at either the setting of the Sun on the local horizon; the exact moment of, the interval between, two sunrises or sunsets depends on the geographical position, the time of year. A more constant day can be defined by the Sun passing through the local meridian, which happens at local noon or midnight; the exact moment is dependent on the geographical longitude, to a lesser extent on the time of the year. The length of such a day is nearly constant; this is the time as indicated by modern sundials. A further improvement defines a fictitious mean Sun that moves with constant speed along the celestial equator. A day, understood as the span of time it takes for the Earth to make one entire rotation with respect to the celestial background or a distant star, is called a stellar day; this period of rotation is about 4 minutes less than 24 hours and there are about 366.2422 stellar days in one mean tropical year.
Other planets and moons have solar days of different lengths from Earth's. A day, in the sense of daytime, distinguished from night time, is defined as the period during which sunlight directly reaches the ground, assuming that there are no local obstacles; the length of daytime averages more than half of the 24-hour day. Two effects make daytime on average longer than nights; the Sun has an apparent size of about 32 minutes of arc. Additionally, the atmosphere refracts sunlight in such a way that some of it reaches the ground when the Sun is below the horizon by about 34 minutes of arc. So the first light reaches the ground when the centre of the Sun is still below the horizon by about 50 minutes of arc. Thus, daytime is on average around 7 minutes longer than 12 hours; the term comes from the Old English dæg, with its cognates such as dagur in Icelandic, Tag in German, dag in Norwegian, Danish and Dutch. All of them from the Indo-European root dyau which explains the similarity with Latin dies though the word is known to come from the Germanic branch.
As of October 17, 2015, day is the 205th most common word in US English, the 210th most common in UK English. A day, symbol d, defined as 86 400 seconds, is not an SI unit, but is accepted for use with SI; the Second is the base unit of time in SI units. In 1967–68, during the 13th CGPM, the International Bureau of Weights and Measures redefined a second as … the duration of 9 192 631 770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the caesium 133 atom; this makes the SI-based day last 794 243 384 928 000 of those periods. Due to tidal effects, the
An hour is a unit of time conventionally reckoned as 1⁄24 of a day and scientifically reckoned as 3,599–3,601 seconds, depending on conditions. The hour was established in the ancient Near East as a variable measure of 1⁄12 of the night or daytime; such seasonal, temporal, or unequal hours varied by latitude. The hour was subsequently divided into each of 60 seconds. Equal or equinoctial hours were taken as 1⁄24 of the day. Since this unit was not constant due to long term variations in the Earth's rotation, the hour was separated from the Earth's rotation and defined in terms of the atomic or physical second. In the modern metric system, hours are an accepted unit of time defined as 3,600 atomic seconds. However, on rare occasions an hour may incorporate a positive or negative leap second, making it last 3,599 or 3,601 seconds, in order to keep it within 0.9 seconds of UT1, based on measurements of the mean solar day. The modern English word hour is a development of the Anglo-Norman houre and Middle English ure, first attested in the 13th century.
It displaced the Old English "tide" and "stound". The Anglo-Norman term was a borrowing of Old French ure, a variant of ore, which derived from Latin hōra and Greek hṓrā. Like Old English tīd and stund, hṓrā was a vaguer word for any span of time, including seasons and years, its Proto-Indo-European root has been reconstructed as *yeh₁-, making hour distantly cognate with year. The time of day is expressed in English in terms of hours. Whole hours on a 12-hour clock are expressed using the contracted phrase o'clock, from the older of clock. Hours on a 24-hour clock are expressed as "hundred" or "hundred hours". Fifteen and thirty minutes past the hour is expressed as "a quarter past" or "after" and "half past" from their fraction of the hour. Fifteen minutes before the hour may be expressed as "a quarter to", "of", "till", or "before" the hour; the ancient Egyptians began dividing the night into wnwt at some time before the compilation of the Dynasty V Pyramid Texts in the 24th century BC. By 2150 BC, diagrams of stars inside Egyptian coffin lids—variously known as "diagonal calendars" or "star clocks"—attest that there were 12 of these.
Clagett writes that it is "certain" this duodecimal division of the night followed the adoption of the Egyptian civil calendar placed c. 2800 BC on the basis of analyses of the Sothic cycle, but a lunar calendar long predated this and would have had twelve months in each of its years. The coffin diagrams show that the Egyptians took note of the heliacal risings of 36 stars or constellations, one for each of the ten-day "weeks" of their civil calendar; each night, the rising of eleven of these decans were noted, separating the night into twelve divisions whose middle terms would have lasted about 40 minutes each. The original decans used by the Egyptians would have fallen noticeably out of their proper places over a span of several centuries. By the time of Amenhotep III, the priests at Karnak were using water clocks to determine the hours; these were filled to the brim at sunset and the hour determined by comparing the water level against one of its twelve gauges, one for each month of the year.
During the New Kingdom, another system of decans was used, made up of 24 stars over the course of the year and 12 within any one night. The division of the day into 12 hours was accomplished by sundials marked with ten equal divisions; the morning and evening periods when the sundials failed to note time were observed as the first and last hours. The Egyptian hours were connected both with the priesthood of the gods and with their divine services. By the New Kingdom, each hour was conceived as a specific region of the sky or underworld through which Ra's solar barge travelled. Protective deities were used as the names of the hours; as the protectors and resurrectors of the sun, the goddesses of the night hours were considered to hold power over all lifespans and thus became part of Egyptian funerary rituals. Two fire-spitting cobras were said to guard the gates of each hour of the underworld, Wadjet and the rearing cobra were sometimes referenced as wnwt from their role protecting the dead through these gates.
The Egyptian for astronomer, used as a synonym for priest, was wnwty, "One of the Hours" or "Hour-Watcher". The earliest forms of wnwt include one or three stars, with the solar hours including the determinative hieroglyph for "sun". Ancient China divided its day into 100 "marks" running from midnight to midnight; the system is said to have been used since remote antiquity, credited to the legendary Yellow Emperor, but is first attested in Han-era water clocks and in the 2nd-century history of that dynasty. It was measured with sundials and water clocks. Into the Eastern Han, the Chinese measured their day schematically, adding the 20-ke difference between the solstices evenly throughout the year, one every nine days. During the night, time was more commonly