QUESTION = What exactly is time?

GENERATION = From my astronomy professor: Time is a dimension of spacetime. It allows for things to happen at different speeds and distances from each other. For example, you have a man on a planet floating around the sun. He sees the Earth spin around itself once every 28 days. From his perspective, the Earth is stationary (unless he is rotating around it in the same direction). But let's say he's at the top of a mountain, and he's looking down at the Earth. He sees the Earth spinning at some speed (around its axis, not constant). From his perspective, the Earth is moving at some speed (Earth's angular speed relative to the mountain) but from his perspective, the Earth is stationary (not constant). If you have some space in between the Earth and the mountain, and you need to move to get from one spot to another, then you have to use up some amount of time. You'll notice that this isn't going to take very long, because there is always some motion between the two locations, and in fact, the Earth is accelerating. 

RETRIEVAL #0 = Time (disambiguation)---2009 release BULLET::::- "Time" (EP), a 2014 EP by Beast BULLET::::- "Time" (The Revelator), a 2001 album by Gillian Welch BULLET::::- "Time I", a 2012 album by Wintersun BULLET::::- "T.I.M.E." (The Inner Mind's Eye), a 1993 album by the hip hop group Leaders of the New School BULLET::::- "The Time" (Bros album), a 1989 release BULLET::::- "The Time" (The Time album), a 1981 release BULLET::::- "The Time" (Xu Weizhou album), a 2017 release BULLET::::- "The Time", an EP by rock band Orange Goblin Section::::Music.:Bands. BULLET::::- Time (Yugoslav band), a rock band of the 1970s BULLET::::- The Time (band), a pop group Section::::Music.:Musicals. BULLET::::- "Time" (musical), by Dave Clark, David Soames, Jeff Daniels and David Pomeranz Section::::Music.:Songs. BULLET::::- "Time" (The Alan Parsons Project song), 1980 BULLET:: 

RETRIEVAL #1 = Time (disambiguation)---Time (disambiguation) Time is a common term for the experience of duration and a fundamental quantity of measuring systems. Time may also refer to: Section::::Other matters of temporal measurement. BULLET::::- Time in physics, defined by its measurement: time is what a clock reads BULLET::::- Metre (music), the grouping of basic temporal units, called beats, into regular measures BULLET::::- Time signature, notational convention for the metre Section::::Businesses. BULLET::::- Time (bicycle company), a French bicycle manufacturer BULLET::::- Time Inc., a New York-based publishing company BULLET::::- Time UK, United Kingdom computer retailer Granville Technology Group Section::::Computing. BULLET::::- System time, a computer's reckoning of real-world time BULLET::::- Time (metadata), a representation term BULLET::::- time (Unix), a shell command on Unix and Unix-like operating systems BULLET::::- TIME (command), a shell command on DOS, OS/2 and Microsoft Windows operating systems BULLET::::- Time Protocol, an Internet protocol Section:: 

RETRIEVAL #2 = It's Time---2001 song by Lindell Cooley Section::::See also. BULLET::::- Verb tense usage after the expression "it's (high) time" BULLET::::- "It's the Time", a 2007 album by Ron Carter 

RETRIEVAL #3 = Time---Different systems of measuring time BULLET::::- Time in the "Internet Encyclopedia of Philosophy", by Bradley Dowden. BULLET::::- Time at Open Directory 

RETRIEVAL #4 = Time in physics---parameter. The modern conception of time is based on Einstein's theory of relativity, in which rates of time run differently depending on relative motion, and space and time are merged into spacetime, where we live on a world line rather than a timeline. In this view time is a coordinate. According to the prevailing cosmological model of the Big Bang theory time itself began as part of the entire Universe about 13.8 billion years ago. Section::::Conceptions of time.:Regularities in nature. In order to measure time, one can record the number of occurrences (events) of some periodic phenomenon. The regular recurrences of the seasons, the motions of the sun, moon and stars were noted and tabulated for millennia, before the laws of physics were formulated. The sun was the arbiter of the flow of time, but time was known only to the hour for millennia, hence, the use of the gnomon was known across most of the world, especially Eurasia, and at least as far southward as the jungles of Southeast Asia. In particular, the astronomical observatories maintained for religious purposes became accurate enough to ascertain the regular motions of the stars, and even some of the planets. At first, timekeeping was done by hand by priests, and then for commerce, with watchmen to note time as part of their duties. The tabulation of the 

RETRIEVAL #5 = Time in physics---Time in physics Time in physics is defined by its measurement: time is what a clock reads. In classical, non-relativistic physics it is a scalar quantity and, like length, mass, and charge, is usually described as a fundamental quantity. Time can be combined mathematically with other physical quantities to derive other concepts such as motion, kinetic energy and time-dependent fields. "" is a complex of technological and scientific issues, and part of the foundation of "recordkeeping". Section::::Markers of time. Before there were clocks, time was measured by those physical processes which were understandable to each epoch of civilization: BULLET::::- the first appearance (see: heliacal rising) of Sirius to mark the flooding of the Nile each year BULLET::::- the periodic succession of night and day, seemingly eternally BULLET::::- the position on the horizon of the first appearance of the sun at dawn BULLET::::- the position of the sun in the sky BULLET::::- the marking of the moment of noontime during the day BULLET::::- the length of the shadow cast by a gnomon Eventually, it became possible to characterize the passage of time with instrumentation, using operational definitions. Simultaneously, our conception of time has evolved, as shown below. Section::: 

RETRIEVAL #6 = Time (disambiguation)---series BULLET::::- "Vremya", a Russian TV series whose name translates into English as "Time" Section::::Media. BULLET::::- "Time" (magazine), an American weekly news magazine BULLET::::- "Time" ("xkcd"), an episode of the webcomic strip BULLET::::- "" (1999), a science fiction novel by Stephen Baxter Section::::Music. Section::::Music.:Albums. BULLET::::- "Time" (Arashi album), a 2007 release BULLET::::- "Time" (Atlantic Starr album), a 1994 release BULLET::::- "Time" (Bunny Rugs album), a 2012 release BULLET::::- "Time" (Dave Clark album), a 1986 release BULLET::::- "Time" (Demis Roussos album), a 1988 release BULLET::::- "Time" (Electric Light Orchestra album), a 1981 release BULLET::::- "Time" (Fleetwood Mac album), a 1995 release BULLET::::- "Time" (Jakob Bro album), a 2011 release BULLET::::- "Time" (Klinik album), a 1991 release BULLET::::- "Time" (Leo Ieiri album), a 2018