what is time?

Time-sequential arrangement of all events, or the interval between two events in such a sequence. The concept of time may be discussed on several different levels: physical, psychological, philosophical and scientific, and biological.

Physical Time and Its Measurement

The accurate measurement of time by establishing accurate time standards poses difficult technological problems. In prehistory, humans recognized the alternation of day and night, the phases of the moon, and the succession of the seasons; from these cycles, they developed the day, month, and year as the corresponding units of time. With the development of primitive clocks and systematic astronomical observations, the day was divided into hours, minutes, and seconds.

Any measurement of time is ultimately based on counting the cycles of some regularly recurring phenomenon and accurately measuring fractions of that cycle. The earth rotates on its axis at a very nearly constant rate, and the angular positions of celestial bodies can be determined with great precision. Therefore, astronomical observations provide an almost ideal method of measuring time. The true period of rotation of the earth, that with respect to the fixed stars, defines the sidereal day, which is the basis of sidereal time. All sidereal days are equal. The period of rotation of the earth with respect to the sun (i.e., the interval between successive high noons) is the solar day, which is the basis for solar time. Because of the earth's motion in its orbit around the sun, the sun appears to move eastward against the fixed stars, and the earth must make slightly more than one complete rotation to bring the sun back to the observer's meridian. (The meridian is the great circle on the celestial sphere running through the north celestial pole and the observer's zenith; the passage of the sun across the meridian marks high noon.) But the earth's orbital motion is not uniform, and the plane of the orbit is inclined to the celestial equator by 231/2°. Hence the eastward motion of the sun against the stars is not uniform and the length of the true solar day varies seasonally, but on the average is four minutes longer than the sidereal day. True solar time, as measured by a sundial, does not move at a constant rate. Therefore the mean solar day, with a length equal to the annual average of the actual solar day, was introduced as the basis of mean solar time.

Mean solar time does move at a constant rate and is the basis for the civil time kept by clocks. Actually, the earth's rotation is being slightly braked by tidal and other effects so that even mean solar time is not strictly uniform. The law of gravitation allows prediction of the moon's position in its orbit at a given time; inversely, the exact position of the moon provides a kind of clock that is not running down. Time calculated from the moon's position is called ephemeris time and moves at a truly uniform rate. The accumulated difference between mean solar and ephemeris time since 1900 amounts to more than half a minute. However, the ultimate standard for time is provided by the natural frequencies of vibration of atoms and molecules. Atomic clocks, based on masers and lasers, lose only about three milliseconds over a thousand years. See standard time; universal time.

Psychology of Time-

As a practical matter, clocks and calendars regulate everyday life. Yet at the most primitive level, human awareness of time is simply the ability to distinguish which of any two events is earlier and which later, combined with a consciousness of an instantaneous present that is continually being transformed into a remembered past as it is replaced with an anticipated future. From these common human experiences evolved the view that time has an independent existence apart from physical reality.

Philosophy and Science of Time-

The belief in time as an absolute has a long tradition in philosophy and science. It still underlies the common sense notion of time. Isaac Newton, in formulating the basic concepts of classical physics, compared absolute time to a stream flowing at a uniform rate of its own accord. In everyday life, we likewise regard each instant of time as somehow possessing a unique existence apart from any particular observer or system of timekeeping. Inherent in the concept of absolute time is the assumption that the simultaneity of two given events is also absolute. In other words, if two events are simultaneous for one observer, they are simultaneous for all observers.

Relativistic Time-

Developments of modern physics have forced a modification of the concept of simultaneity. As Albert Einstein demonstrated in his theory of relativity, when two observers are in relative motion, they will necessarily arrange events in a somewhat different time sequence. As a result, events that are simultaneous in one observer's time sequence will not be simultaneous in some other observer's sequence. In the theory of relativity, the intuitive notion of time as an independent entity is replaced by the concept that space and time are intertwined and inseparable aspects of a four-dimensional universe, which is given the name space-time.

One of the most curious aspects of the relativistic theory is that all events appear to take place at a slower rate in a moving system when judged by a viewer in a stationary system. For example, a moving clock will appear to run slower than a stationary clock of identical construction. This effect, known as time dilation, depends on the relative velocities of the two clocks and is significant only for speeds comparable to the speed of light. Time dilation has been confirmed by observing the decay of rapidly moving subatomic particles that spontaneously decay into other particles. Stated naively, particles in motion decay more slowly than stationary particles.

Time Reversal Invariance-

In addition to relative time, another aspect of time relevant to physics is how one can distinguish the forward direction in time. This problem is apart from one's purely subjective awareness of time moving from past into future. According to classical physics, if all particles in a simple system are instantaneously reversed in their velocities, the system will proceed to retrace its entire past history. This property of the laws of classical physics is called time reversal invariance (see symmetry); it means that when all microscopic motions of individual particles are precisely defined, there is no fundamental distinction between forward and backward in time. If the motions of very large collections of particles are treated statistically as in thermodynamics, then the forward direction of time is distinguished by the increase of entropy, or disorder, in the system. However, recent discoveries in particle physics have shown that time reversal invariance is not valid even on the microscopic scale for certain phenomena governed by the weak force of nuclear physics.

Biological Time-

In the life sciences, evidence has been found that many living organisms incorporate biological clocks that govern the rhythms of their behavior (see rhythm, biological). Animals and even plants often exhibit a circadian (approximately daily) cycle in, for instance, temperature and metabolic rate that may have a genetic basis. Efforts to localize time sense in specialized areas within the brain have been largely unsuccessful. In humans, the time sense may be connected to certain electrical rhythms in the brain, the most prominent of which is known as the alpha rhythm at about ten cycles per second..

Time is an illusion par excellence, so perfectly and craftily constructed that we all tend to take it, at some time in our lives, as a reality. All time is actually simultaneous, all time is NOW. But our minds have not developed in such manner that we can perceive this as so. If all time is in fact now, that is tantamount to saying there is no time or time is an illusion. There have been some mystics and other spiritual beings who have broken through the illusion. Still, we do not really comprehend their accounts.

Of some interest here perhaps is the view of the ancient Greek philosopher Heraclitus on the relation of the random chance inherent in the universe and time. He said, "Time is a child moving counters in a game; the kingly power is a child's." Wouldn't that be the ultimate irony, if that were true?

What is time?

Often the immediate concept that comes to mind is a clock, watch or a calendar, but what really is time?

This is perhaps a very confused subject and you often hear: “I have no time.”, “Time is money.”, “I need to be on time” and so on.

And for example the Einstein theory of relativity makes the subject for ordinary people just even more confused.

Let us assume time would stop, what would happen?

I tell you what would happen. Nothing would move. As “The illusion called time is composed of altering of the particles position in space” and “Alteration is the basic manifestation of time”. (L. Ron Hubbard, 1951)

Everything moves, all the time. Time is measered from instruments which from beginning comes from natural movements such as the sun and the planet as well as the moon.

Let us assume that suddenly something happens and the planet would circulate slower around its own axel. Let us say it would take 30 hours instead of 24.

Now to the key question, would you have more time?

Perhaps in the beginning that is what would be experienced. But I am pretty sure that after a month or two people still claim to not have enough time.

Imagine when you where a child and there was a lot of commotion and a lot of action. Life was fun and time appeared to be over before you even noticed it - mother coming and telling it was over. And it was always as it was most fun. This even though the child was gone for the whole afternoon.

Then imagine when you another day had to go and visit the old grandmother. It was boring and the time went very slow, very very slow.

Once when I was a kid and I had to tell my little brother - who had no concept of words such as hours, minutes and so on - that mam comes back in one hour. I told him: “Mother comes back after one ‘Donald Duck’” as Donald Duck cartoon last for one hour and he saw this each week, thus I assumed he would understand. But now to my point, the next hour of waiting for mam was probably experienced 10 times longer then the hour of cartoon. Does time then not have something to do with the person?

I know a person saying that she has no time to write a letter to me during the last months and I know a person (myself) who is working 80 hours a week but still makes it to write a novel.

What is the difference?

You create time by being effective. When you see something to be done, do it immedietly and work fast. Only then can you really say that you have more time. A person saying “I don’t have time to do X” is just saying the X is not considered a priority for this particular person - otherwise the person would organize himself in a way to get X done. My father told me a good counter-statement to somebody stating that they don’t have time: “Do you watch TV?” if the question is “yes”, then ok the person has time to do even more things.

Let us speculate as to what time really is.

Could you have time without a viewpoint? Certainly not. It has to be “viewed” and then an idea about it’s passing has to be created or “considered”.

Thus the viewpoint is the key ingradient and not so much “it” itself.

So we found the answer easy; time is what you consider it to be. “A consideration” as Mr. Hubbard writes, and that is all.

There is no such thing. Or to put it another way - it an illusion that you have constructed in your mind.

FACT: No one have ever been to another time. Most scientists are of the opinion that nobody ever will. Even the most obscure of supposed methods for time travel tend to just suggest a more complex defintion of 'now' rather than any kind of real movement along a supposed time-dimensional axis.

So given that there is no distinction between the past (or future) and someplace that is completely imaginary, is it not more reasonable to assume that the past and future - just like all the other completely mental constructs - are imaginary too?

Two views on the space and time.

1.

There are an independent space and independent time:

We notice it on our planet - Earth.

It is a fhree - dimensional space.

This time is local.

2.

There is simultaneous union of space and time:

It is negative four-dimensional (Minkowski) space.

This time [s Absolute.

Herman Minkowski :

“ Henceforth, space by itself, and time by itself,

are doomed to fade away into mere shadows,

and only a kind of union of the two

will preserve an independent reality.”

===============================

http://www.socratus.com/

what are you asking? Time is only the concept of man and it only make sense when used by men.

all the rest of the so call answers have no relevance with time.

(Time and Space) space is there, but time is the invention of man to explain the unknown.

Two distinct views exist on the meaning of time. One view is that time is part of the fundamental structure of the universe, a dimension in which events occur in sequence. This is the realist view, to which Isaac Newton [1] subscribed, in which time itself is something that can be measured.

A contrasting view is that time is part of the fundamental intellectual structure (together with space and number) within which we sequence events, quantify the duration of events and the intervals between them, 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. This view is in the tradition of Gottfried Leibniz[2] and Immanuel Kant,[3][4] in which time, rather than being an objective thing to be measured, is part of the mental measuring system.

The Oxford English Dictionary defines time as "the indefinite continued progress of existence and events in the past, present, and future, regarded as a whole." [5] The American Heritage Dictionary defines time as "a nonspatial linear continuum in which events occur in an apparently irreversible succession." Encarta, Microsoft's Digital Multimedia Encyclopedia, gives the definition of time as a "System of distinguishing events: a dimension that enables two identical events occurring at the same point in space to be distinguished, measured by the interval between the events."

Many fields avoid the problem of defining time itself by using operational definitions that specify the units of measurement that quantify time. Regularly recurring events and objects with apparent periodic motion have long served as standards for units of time. Examples are the apparent motion of the sun across the sky, the phases of the moon, and the swing of a pendulum.

Time has historically been closely related with space, the two together comprising 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(s), and the human perception as well as the measurement by instruments such as clocks are different for observers in relative motion. Even the temporal order of events can change, but the past and future are defined by the backward and forward light cones, which never change. The past is the set of events that can send light signals to the observer, the future the events to which she can send light signals. All else is the present and within that set of events the very time-order differs for different observers.

Time has long been a major subject of science, philosophy and art. The measurement of time has also occupied scientists and technologists, and was a prime motivation in astronomy. Time is also a matter of significant social importance, having economic value ("time is money") as well as personal value, due to an awareness of the limited time in each day and in our lives. This article looks at some of the main philosophical and scientific issues relating to time.

see link for more:

Time is a unit which fills different colors in the life.

It may be good or bad. It is very much precious.

Life is Short.

Enjoy the TIME.

Part of the answer is that time is a great illusion. Einstein's answer is part of the equation E=mc2 and the Theory of Relativity. It is an attempt to explain the construct of the time/space continuum. Time is not a constant thing anywhere in our universe. There are six time zones on the North American continent, each one hour wide and essentially inefficient devices attempting to measure the passage of time on our planet. Actual time (relative to sun travel) varies greatly across the width of any given time zone. This gives us a clue as to the difficulty of understanding universal/cosmic time. Light from one of our nearest stars takes more than four years to reach us...so it would takes us four years or more to realize it if it no longer existed or exploded. Distance of that magnitude is not only distance - it is also time. Hence the term light-year which measures both time and distance relative to a given point of origin or destination. The galaxy and the universe are vast in both distance and time.

Time exists for us as a linear experience relative to the mass and speed of revolution of our planet and rate of travel around and distance from our star, the sun. This time construct is unique to us and this planet...and does not exist in precisely the same way even on our moon or any other planet in our solar system. It changes even more drastically as we leave our solar system and experience the masses and speeds of other stars and planets of the galaxy. This is one of the huge barriers to galactic space travel anywhere out of our system. Time is essentially a physical illusion created by the mass and speed relationships in our solar system and physical universe. It would change completely if we moved to Mars, for example (or the Moon).

22,000 days is the average human lifespan here...but we have no idea what might happen to that timespan if it was lived somewhere else relative to mass, speed, and constant (which is the speed of light). Time is essentially a trick of our physical environment that we have evolved to depend on and travel within for a certain distance: our lifespan. It is peculiar to our location and the size of our planet - and to lesser degrees upon the makeup of our solar system as well. It is a unique construct existing only here in this one speck out of the huge universe.

Remember, clocks and hours are very recent devices based on movement and distance. Days and years are distances of travel as well. Just something to think about.

Time is distance relative to gravity (mass). It constructs itself according to these physical parameters and we have evolved to live within them and adapt to them.

Time is a state of mind.

Time is the phenomenon that prevents everything happening all at the same moment