When thinking of cycles and myths, one cannot pass the idea of Kronos or Kali. That brought me to form some questions about the nature of time.

Three definitions for time:

  1. Time is a measure of the change. Change is a result of the forces.

  2. Time can be understood as a consciousness of history—present and future—which emerge from capable of memorizing.

  3. Time is relative, as per Einstein.

Time as a relative, yet real, "thing" is confusing (at least, I'm probably not only one in the world who thinks so!). Everything in the universe seems to be in motion. Atoms, cells, and even inner human organs are in constant change; the earth rotates and orbits around the sun. The sun orbits and rotates within the galaxy; the galaxy rotates and orbits or expands or moves in space. Maybe a huge unisystem (contra ecosystem) of galaxies is still moving as a group. Now, because there is so much movement and forces, why can one say that time slows in moving objects or that it is something real, something more than change and movement and concept of human mind?

It has been said that time is relative to gravity. If so, what is the exact particle that one would measure and compare to gravity? Say our head is 72 inches above the ground. Time passes more slowly around our head than by our toes. Does this mean that aging is different for different parts of the body, or merely that the atoms gets older, or that the earth's rotation compared to the sun's is different for the head and toes, and so forth, up to a higher scale?

The primitive natural way to understand time is to see the change of days and years. Think of time traveller who takes a trip in speed of light years and comes back and sees everything is 5 years older than what his clock says. Of course, time travel itself brings up plenty of paradoxes in a physical sense, but what I'm thinking is did the traveller's aging process slow down, or did the planets' and sun's, or even the whole galaxy change its speed relative to the traveller and people on earth? Or was it only the atomic clock that slowed down?

I'm not sure if I'm able to to describe the problem I'm facing when trying to understand what is really meant with special relativity theory. I guess it is really something that occurs on an atomic or quantum level, and only at huge speeds, which brings me to question—is there any real world usage for the theory?

Related reading:

Additional thoughts:

The starting point of orbit in the case of the earth is relative to four cardinal points of seasons. As well, day and night act as starting points in a shorter time scale. But when it comes to evolutions of the solar system, one cannot really describe the point at which we find some relative point either in the whole planetary system or outside of it. But in all cases, it is just a matter definition and a commonly accepted cardinal point that one tries to discover from ever-changing parts of the system.

What I also tried to ask was, is time bending on sub- and/or sur-systems in relative theory? That's fundamental, I think, because there are vehicles in vehicles in vehicles moving at different speeds in space.

Update in 2016

I'd still say that this is a fundamental question in many ways. Coincidently in 2012, when I formed this question, American theoretical physicist, Lee Smolin wrote a book Time reborn that deals with the topic. From his later essay (2013) we can read:

I argue here that the key issue responsible for divergent versions of naturalism and divergent approaches to cosmology is the conception of time. One version, which I call temporal naturalism, holds that time, in the sense of the succession of present moments, is real, and that laws of nature evolve in that time.

But on the other hand in the forementioned book, chapter 3, he follows Leibniz and states:

there can be no absolute time... time must be a consequence of change... without alteration there can be no time

Which draws back to the question if time is just an epithet for change and motion thus using either term is just a matter of taste.

Altogether Smolin's angle to the time seems to be more raised toward Platonism, Newtonism and Einsteinism, where Reality was regarded as a timeless and an untouchable dimension. But does he describe the nature of the time itself, one should read his books and essay and make careful notes to see.

  • 3
    Can you make the question more clear, asking about relativity theory is not what this forum is meant for
    – apoorv020
    Commented Apr 18, 2012 at 6:51
  • 2
    The philosophical literature on time is enormous, and includes works as disparate as Kant's Critique of Pure Reason and Heidegger's Being and Time. You're going to have to narrow your question down quite a bit for it to be useful here, and remove the sections that relate to physics, as those are best answered elsewhere. Commented Apr 18, 2012 at 11:30
  • 1
    2 points: 1 - I think you meant to say that time passes more quickly for our head than toes (time slows down as you approach a black hole because of the distortion caused by gravity). 2 - Question: "Is there any real world usage for this theory?" Answer: GPS Note: I haven't made this an answer because I doubt it's complete enough.
    – commando
    Commented Apr 18, 2012 at 12:35
  • 1
    @PHPGAE The theory is that time literally slows down - it's not that atoms happen to vibrate more slowly, but that every process, the very passing of time itself (truly mind-boggling and abstract) has slowed down.
    – commando
    Commented Apr 18, 2012 at 16:09
  • 1
    @Jon: In my view, philosophy can leave to the sciences those matters which the scientific method can handle; there's plenty leftover to keep us busy. Commented Apr 23, 2012 at 19:30

12 Answers 12


I think one source of confusion with the concept of time is that it actually names two very different but related concepts:

  1. The qualitative concept of time as an experience.
  2. The objective physical phenomenon underlying that experience.

To make clear what I mean, let's look at a different concept where this separation is generally understood and where we have the words to clearly distinguish: Colour.

There's the qualitative aspect of colour: We perceive red, green, blue, yellow, etc. It is generally understood that those colours exist ultimately only in our brain.

And there's the physical concept of light as electromagnetic wave, which we can split into frequencies, and if light with a certain spectrum reaches our eyes, it will cause some colour to be perceived (which colour it is may depend on other things, like the light which reaches other parts of our eyes, genetic conditions affecting the receptors in the eyes, and more).

It is understood that "a red object" is an object which emits or reflects light with a spectrum which, if it reaches our eyes, causes us under normal circumstances to perceive the color red.

Now back to time. When people speak about time, they often do not make that separation. The time we perceive is not the same as the time described as part of spacetime by General Relativity. But both are also not unrelated. The situation is basically the same as with colours/spectra.

As additional complication, even the physical concept of time isn't really completely understood. The concept of time as it is used in General relativity and the concept of time as it is used in Quantum Mechanics are quite different, and this difference is one of the problems when trying to combine GR and QM. In particular, in GR, space and time coordinates are of the very same type (they can even be mixed in transformations), while in QM they are something completely different (especially, in QM time is not an observable, but a mere parameter, but location is an observable).

This distinction sets apart your point 2 from your points 1 and 3. So if point 2 looks quite different, that's because it is. It speaks about a different phenomenon, just like "colour" is about a different phenomenon than "light spectrum". Both are related, but not the same.

Now about your point 3, the relaivity of time. This actually concerns two different, but related aspects of relativity. One aspect is in analogy to perspective: Just as lengths of things which are at an angle to you look perspectively shortened, lengths and times of things which are moving also are "perpectively" modified. Note that even in space, perspective shortening is physical: If you tilt your ladder, it fits through a door, despite it being longer than the door is high.

This leads directly to the second effect, namely the way-dependence of elapsed time. This again has an analogue in space: It's the way-dependence of the covered distance. If you go the direct way, which is the way where you make no curves, your covered distance is shorter than when you make a detour. So you arrive at the same place after travelling a different distance. The twin paradox is basically the same, except that detours shorten the time (that's related to the peculiarities of the spacetime metric, which BTW are also responsible for the fact that you cannot simply turn around in time and go back into the past). Here the "places" are the events, and the direct way is the unaccelerated way, while the curves in the non-direct way correspond to acceleration.

So basically the problem people have with underatanding relativity is that they consider time as something which elapses uniformly in the whole universe, while in reality, time is the "temporal distance" we traveled in spacetime. That distance depends on the way we use through spacetime. This "temporal distance in spacetime" is also the aspect of spacetime which underlies our perception of time (just like the spectrum of the electromagnetic wave is the aspect of the electromagnetic field which underlies our perception of colour).

Now about your point 1. To that point, I simply disagree. Time is not a measure of change, for two reasons:

  1. Change happens in time. Something changing twice as fast doesn't mean that time goes twice as fast. Indeed, there can be two processes occurring at different speeds in the very same time.

  2. Change is not always change in time. For example, the temperature changes with the place as well as with the time. At different places things are different, just like at different times, things are different. If change were what makes time, then there would be no difference between location and time. But there is difference (even in GR, where the space and time dimensions have a different sign in the metric tensor, and lines describing the movement of objects always have to be timelike). The most obvious difference is that you can freely move in space, but not in time.

About the relation of time with gravitation: According to General Relativity, the spacetime (not just space) is curved. This means that the "straight" ways are apparently curved, too. Again you can make a space analogy: If you start in east direction somewhere north of the equator, but then don't care about the compass, but just walk straight on (let's also ignore that you'll sooner or later will have to walk over the ocean ;-)), you'll follow a great circle, and at some time find you're crossing the equator. Then you'll continue to get more south until you reach a most south "turning point" and start going north again. You'll then cross the equator again, and so on. If you didn't know anything about spherical geometry, you would say it looks as if the equator was somehow attracting you, so you're oscillating around it. (Look at the trajectory of satellites drawn over a map to see such oscillations; although there's the additional complication that the earth rotates under the satellites.)

Now the relation to time is that, as it turns out, the spacetime distance of ways passing closer to a massive body is shorter, that is, you need less time between two events if you are closer to the massive body, so it looks as if the time close to the body went more slowly.

So let me summarize:

  • Your first point is, IMHO, simply wrong.
  • Your second point is about the perceived time (think: colour)
  • Your third point is about the physical time (think: spectrum)
  • Your problem about the third point is due to a concept about physical time that just doesn't fit with relativity.
  • The relation of time to gravitation is that according to GR gravitation is the curvature of spacetime, and when passing near gravitational bodies, the "spacetime distance" between events is shorter.

And about real uses of the theory of special relativity: It is used all the time. For example, without taking into account both special relativistic and general relativistic effects, GPS could not function. Also, without taking into account special relativistic effects, the accelerators would not work (not only those used by particle physicists, but also e.g. those used in hospitals to generate radiation for cancer therapy).

  • There is a lot of critics, that challenges GPS tech being prove of SRT. Huge amount of related discussion is going on here: stormfront.org/forum/t928728
    – MarkokraM
    Commented Jun 3, 2013 at 6:41
  • 2
    @PHPGAE That's a neo-Nazi white supremacist hate site known for its conspiracy theories about Jews, and a silly place to go looking for scientific opinions if you ask me.
    – David H
    Commented Aug 1, 2013 at 11:45

The simplest definition of time is it is a sequence of events with respect to an observer.

We humans experience three states—namely, waking, dream and deep sleep (sound sleep where nothing is felt or perceived.)

  1. The time we now experience is present only in the waking state as it is common to all of us. It is not felt during dream and deep sleep states. So, it is not permanent with respect to our experience.

  2. In dreams, we create our own world with characters, images etc. from the impressions gathered in the subconscious mind. After waking up, we observe that relatively large time spans(with respect to our waking life) have flitted past our minds in one night! Even the dream time is not permanent to our experience as upon waking or in deep sleep, it is absent.

  3. Coming to deep sleep, there is nothing that is perceived or felt. We are not even conscious of our body, let alone time. This, I must say, is the most curious of experiences we have as we exist but yet not exist as it is a void. This is yet different from dream and waking states.

A reference from the Vedanta text Tripura Rahasya is as follows:

Time and space are the factors of division in the world; of these, space refers to the location of objects and time to the sequence of events. Time and space are themselves projected from consciousness. How then would they divide or destroy their own basis and still continue to be what they are?

Can you show the time or place not permeated by consciousness? Is it not within your consciousness when you speak of it? The fact of the existence of things is only illumination of them, and nothing more. Such illumination pertains to consciousness alone. That alone counts which is self-shining. Objects are not so, for their existence depends upon perception of them by conscious beings. But consciousness is self-effulgent — not so the objects, which depend on conscious beings for being known.

Judging from the above points, we can conclude time is only a concept we are subject to vis-a-vis the mode of experience. It's a difficult pill to digest that it is only a concept, but, the sages from India have, with reason and proof said this.

Also, having seen the word "consciousness" in a previous answer, and the difficulty of the author in explaining it, let me make a humble attempt to explain what it is.

Consciousness is the source—the cognitive factor—in us by which we become aware of everything. Everything we perceive is through consciousness without which experience is impossible. For example, we feel through our body when alive. But this same body, though present after death, is not able to feel anything. The same goes for our minds also.

I won't delve into consciousness more as it is not the question.

  • I'd like to raise another thread about consciousness if its not asked in the forum already. But in this answer time is explained from plain individual single observer point of view. But we need to consider empiric multiple observer study, which says that whether you are awake, sleep or deep sleep state, world around you will continue to exists and clock will tick. So its not totally right that time disappears when you sleep, if it still exists for billions of people and even for your body that still breaths in certain rhythm.
    – MarkokraM
    Commented May 4, 2012 at 3:30
  • @PHPGAE - Your objection is valid, no doubt. But, let me state the definition of time once more - It is a sequence of events with respect to an observer. If we, when in a dream or deep sleep are not aware of it, then it makes no difference whether the time is present or not. As i cited in the reference, for time or any object to be felt(time is not an object, I clarify), it is through us that time is expressed. Any further clarification would require you to investigate who you are, in terms of definition as in Who is PHPGAE? Answer it with proper thought and time will be known to you. :) Commented May 5, 2012 at 9:33
  • Abhishek Iyer - That's interesting indeed. Dreams actually happen in sequence, at least the part we recall at the morning. It's even more evident in conscious dream like lucids. Don't you think it hints, that time factor is present on dreams as well? Its true sequences of dream events can differ a lot compared to real world events, but still they have their order. And one can look back in history on dream and try to jump there. But true, its respect to observer and relative to what is observed.
    – MarkokraM
    Commented May 5, 2012 at 17:20
  • Time is experienced in deep sleep, people are generally good at knowing how long they have slept. See eg sciencefocus.com/the-human-body/… Total body anaesthesis, typically results in a sense of no time having passed. Circadian rythm has been shown to emerge at the cellular level ncbi.nlm.nih.gov/pmc/articles/PMC5057284/s.
    – CriglCragl
    Commented Aug 25, 2021 at 12:42

In the Sanskrit language time is called Kāla.

The same word Kāla is also means the death.

So in the Sanskrit language time a is synonym of death.

In the context of the spiritual world, time is related to an age:

  1. There is a concept of an age: the amount time spent in life exists.
  2. The concept of an age exists only because death exists. There will be no concept of an age (death) if one who is born goes on living continuously without death.

In the context of the physical world, time is related to motion:

  1. Consider an object in motion.
  2. The object will be in motion till the effect of the applied force stops (due to other forces).
  3. The object wasn't in motion for all the time and will not be in motion for all the time.
  4. This means that the concept of time is there only because motion of the object was started (born) and motion of the object is going stop (die).

It has been said that time is relative to gravity.

It is related to gravity.

  1. As a concept, time is there because motion of the objects starts and stops.

  2. Motion happens and ends because the forces applied on the objects starts and stops. So ultimately, it is not the motion but the force applied on the body that is created and destroyed. If force is there then motion will be there. If motion is there than the change (the transformation) is there.

  3. Now gravity is force exerted by an object with a mass to another object with a mass. And gravity causes → the force, the force causes → the motion, and the motion → causes time.

So we can also conclude that an object (with mass) causes gravity (the force) causes motion (the movement in space) causes time.

The time can be defined as a measure (or measurement "device/thing/object") of the changes or a measure of the transformations of the mass or a measure of an effect caused by the mass which starts from a creation (birth) and approaches towards destruction (death).

But the creation nor destruction of the force/mass/mass/energy/motion is observed (or not possible one can say), so only transformation is possible from one form to another form.

So the transformation goes on and on, creating a circle of creation and destruction.

If the transformation is forever than time is forever.

If the transformation is a physical factor than time is.

Time appears only when the transformation appears.

  • 1
    Just a note on the Sanskrit at the beginning of your answer:‌ ‌while kāla does indeed mean "time", and while one of its meanings does include ‌"death", it is not right to say that in Sanskrit "time"‌ and "death" are synonyms. There are many words that can be used to denote "death"; the word "time"‌ just happens to be (a poetic) one of them:‌ in the sense of "your time is up", or "all things wither with time" / "all things are destroyed by Time". See the entry starting at the bottom left (leftmost column)‌ here: i.sstatic.net/U02qw.jpg for the shades of meaning of "kāla".
    – user3350
    Commented Mar 17, 2013 at 10:20

According to Hawking's A Brief History of Time, time is a physical factor in the way that entropy grows with time, i.e., if you observe a closed physical system in two different states, the one with the higher entropy must be "later" than the one with lower entropy.

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    So they why do you need 'time' as a quantity separate from entropy? Time is just a concept to capture the fact that we can only experience things that involve a net increase in entropy.
    – user9166
    Commented Sep 23, 2014 at 14:57

It seems likely, given the apparent reversibility of most physical laws, that time does not flow in one direction, but that humans can only perceive it as flowing forward because human memory relies upon increasing entropy as a means of encoding.

So the answer becomes 'both'. Since we mark time as increasing entropy, the increase of entropy becomes a physical process in time as we remember it, and we might as well incorporate all of our experience into our theory of the universe.

But in a more absolute sense, time is then an aspect of human existence and our experience of similar phenomena around us. For me, this perspective makes sense out of the fact that real-time physical processes seem to employ much more processing power than should be available to them.

If they would proceed in a way that ultimately contradicts what human reality permits, time would not continue forward for us very far from that moment, and in the end, we would remember the flow that we are allowed to be part of. All failures and retries edit themselves out of the record of history, so it seems as though nature is almost always 'right'.

The Second Law of Thermodynamics (considered as an aspect of humanity and not of physics) creates the effect of the Limited Anthropic Principle on a very detailed level.


I’ve been thinking a lot about time recently since re-watching the hit TV series Cosmos. Neil DeGrasse Tyson did a wonderful job hosting the serious originally made possible by Carl Sagan. Second thought; perhaps it was an episode of Star Talk I was watching. I can’t remember. Regardless, Dr. Tyson mentions that Albert Einstein could never wrap his head around time and its properties as they relate to Physics. While Einstein was brilliant, and I mean a f***ing genius, he wasn’t quite as “outside the box” in his flow of logic as others such as Michael Faraday. Not to say that one was more genius than the other, simply that different experiences in life shape different minds in different ways. Thus, allowing the right mind in the right place at the right time to see something no one else could have possibly discovered. In retrospect these discoveries seem to stem from an “outside the box” flow of logic or, perhaps, some godlike sense of notion. Whatever the reason, time is the one thing that escaped Einstein in his quest to understand all properties of our physical world. The sentence you just read is what prompted me to consider the following possibility.

It dawned on me while I was laying on the couch and drifting off in thought. My eyes were open yet unfixed on any given object. Above me, the ceiling fan faithfully rotated its blades and performed its duties. I wasn’t thinking about time at all but the words spoken by Dr. Tyson had remained lodged in my mind for some unknown reason. That is when it hit me. I remained staring up from my position on the couch but now transfixed on the rotation of the ceiling fan. My mind raced through thoughts of everything that rotates in the physical realm; all the way down to the almighty electron. Then I said the words to myself, “causality is a myth and time does not exist.”

Let’s take a quick look at what Einstein thought regarding time and motion. In Special Relativity and Quantum Field Theory the notions of space, time and causality become tangled together, with temporal orders of causations becoming dependent on who is observing them. In Albert Einstein's original pedagogical treatment, it is based on two postulates: 1) The laws of physics are identical in all inertial systems (non-accelerating frames of reference). 2) The speed of light in a vacuum is the same for all observers, regardless of the motion of the light source. Special Relativity was originally proposed in 1905 by Albert Einstein in the paper "On the Electrodynamics of Moving Bodies." Special relativity corrects the mechanics of previous endeavors to handle situations involving motions nearing the speed of light. As of today, special relativity is the most accurate model of motion at any speed.

There are a couple of things worth noting here in regards to Special Relativity. The first being the idea that space, time, and causality become tangled together. The second being the notion that temporal orders of causations are dependent on who is observing them. There are other concepts in Special Relativity that are worth mentioning in this discussion. One being that time and space cannot be defined separately from each other. Rather space and time are interwoven into a single continuum known as spacetime. Events that occur at the same time for one observer can occur at different times for another.

The point I’m trying to make here is rather simple. Time is not a component of our natural physical world. Rather, it is simply how our minds process motion. Albert Einstein focused so much on trying to make the equations work that the (potentially) obvious answer escaped him. The reason that space, time, and causality seem to be interwoven is because our minds process motion in a homogeneous continuum. Everything we observe is linear, thus we naturally are inclined to believe the physical world operates in the same manner. But what if it doesn’t? What if the concept of time is relative not because of gravity and other forces, but simply because it only exists in our midbrain. We know quite a bit about Time Perception in human beings. We even understand now that disorders such as Parkinson’s and ADHD affect an individual’s ability to perceive time. One interesting side note, individuals with ADHD consistently possess a higher IQ than the average human being. Perhaps their sub-conscience has already figured out that time is irrelevant.

Imagine yourself surrounded by space; no light, no sound, and no motion. When you open your eyes all you see is the blackness of empty space devoid of all light. When you listen, it is so quiet that you can hear your own heart beating and the blood flowing through your brain. You cannot move and there is only nothingness. No family, no job, no Earth.. nothing. You exist but that is all. In this situation, would you have a need for time?

As a species we learned early on in Mesopotamia the advantages of forming a civilization and living under a uniformed code of work and discipline. For the first time in history we came together in the interest of agriculture and survival. Humans have not changed much since then and we still strive to be in sync as a species because it is advantageous for us to do so. Clocks help us organize our day and more efficiently use the daylight hours. As such, the concept of time is useful to us. In a more primitive retrospect, time perception serves as an invaluable survival instinct as it allows us to gauge the attack of a wild animal or dodge an incoming object. I believe this is why time perception is so deeply rooted into a human’s core function and, thus, why we are inclined to see the physical world as being linear and homogeneous. In addition to these things, human beings have always had a need to find meaning in life; to find a "theory of everything" to tie it all together. Maybe we have that need because our sub-conscience knows that the natural world is 180 degrees opposite to the way we perceive it.

What if I am right? What if time is only in our heads and that is why the very idea of it caused Einstein such a fit in his equations? For starters, causality and the concept of spacetime has to be thrown right out the window. Causality states, quite simply, that one process (the cause) is understood to be partly responsible for the second (the effect), and the second is dependent on the first. If time is simply the human mind’s comprehension of motion and the physical world is not tied together by it, then one can make certain assumptions. If a marble (Event A) is rolled down an incline towards a line of dominoes, it should strike the dominoes causing a chain reaction (Event B). In our minds we perceive the direction of the marble in our linear scope of motion and see no other outcome. In fact, however, there is an endless number of possible outcomes. There is an entire branch of mathematics that focuses on this concept. Made popular by Hollywood in the film Jurassic Park, Chaos Theory is an actual concept in higher mathematics. This theory defines chaos as: when the present determines the future, but the approximate present does not approximately determine the future. You can keep going into other similar concepts in various fields, but the point I’m trying to make is that there is never an absolute guarantee of Event A causing Event B. Instead, think of every event that takes place in our physical world as being unique unto itself and independent. It is true that Event A may set certain conditions that make Event B possible, but that is the end of their relation to one another. The laws regarding the Conservation of Energy keep the mass of the marble rolling down the incline, but it is still very susceptible to other unforeseen forces acting upon it. Causality is a myth and time does not exist.

You can go further into time perception and human brain, as well, since there has been a ton of research into the subject. The following are some excerpts from a WikiPedia page on Time Perception.....

Although the perception of time is not associated with a specific sensory system, psychologists and neuroscientists suggest that humans do have a system, or several complementary systems, governing the perception of time. Time perception is handled by a highly distributed system involving the cerebral cortex, cerebellum and basal ganglia. One particular component, the suprachiasmatic nucleus, is responsible for the circadian (or daily) rhythm, while other cell clusters appear to be capable of shorter-range (ultradian) timekeeping. There is some evidence that very short (millisecond) durations are processed by dedicated neurons in early sensory parts of the brain.

Professor Warren Meck devised a physiological model for measuring the passage of time. He found the representation of time to be generated by the oscillatory activity of cells in the upper cortex. The frequency of these cells' activity is detected by cells in the dorsal striatum at the base of the forebrain. His model separated explicit timing and implicit timing. Explicit timing is used in estimating the duration of a stimulus. Implicit timing is used to gauge the amount of time separating one from an impending event that is expected to occur in the near future. These two estimations of time do not involve the same neuroanatomical areas. For example, implicit timing often occurs to achieve a motor task, involving the cerebellum, left parietal cortex, and left premotor cortex. Explicit timing often involves the supplementary motor area and the right prefrontal cortex.

Two visual stimuli, inside someone's field of view, can be successfully regarded as simultaneous down to five milliseconds.

In the popular essay "Brain Time", by David Eagleman, he explains that different types of sensory information (auditory, tactile, visual, etc.) are processed at different speeds by different neural architectures. The brain must learn how to overcome these speed disparities if it is to create a temporally unified representation of the external world: "if the visual brain wants to get events correct timewise, it may have only one choice: wait for the slowest information to arrive. To accomplish this, it must wait about a tenth of a second.

In the early days of television broadcasting, engineers worried about the problem of keeping audio and video signals synchronized. Then they accidentally discovered that they had around a hundred milliseconds of slop: If the signals arrived within this window, viewers' brains would automatically resynchronize the signals". He goes on to say that "This brief waiting period allows the visual system to discount the various delays imposed by the early stages; however, it has the disadvantage of pushing perception into the past. There is a distinct survival advantage to operating as close to the present as possible; an animal does not want to live too far in the past. Therefore, the tenth-of- a-second window may be the smallest delay that allows higher areas of the brain to account for the delays created in the first stages of the system while still operating near the border of the present. This window of delay means that awareness is postdictive, incorporating data from a window of time after an event and delivering a retrospective interpretation of what happened."

A temporal illusion is a distortion in the perception of time, which occurs when the time interval between two or more events is very narrow (typically less than a second). In such cases, a person may momentarily perceive time as slowing down, stopping, speeding up, or running backwards. Additionally, a person may misperceive the temporal order of these events.

Depression may increase one's ability to perceive time accurately. One study assessed this concept by asking subjects to estimate the amount of time that passed during intervals ranging from 3 seconds to 65 seconds. Results indicated that depressed subjects more accurately estimated the amount of time that had passed than non-depressed patients; non-depressed subjects overestimated the passing of time. This difference was hypothesized to be because depressed subjects focused less on external factors that may skew their judgement of time. The authors termed this hypothesized phenomenon "depressive realism."

Stimulants produce overestimates of time duration, whereas depressants and anesthetics produce underestimates of time duration. Psychoactive drugs can alter the judgement of time. These include traditional psychedelics such as LSD, psilocybin, and mescaline as well as the dissociative class of psychedelics such as PCP, ketamine and dextromethorphan. At higher doses time may appear to slow down, speed up or seem out of sequence.

In a 2007 study, psilocybin was found to significantly impair the ability to reproduce interval durations longer than 2.5 seconds, significantly impair synchronizing motor actions (taps on a computer keyboard) to regularly occurring tones, and impair the ability to keep tempo when asked to tap on a key at a self-paced but consistent interval. In 1955, British MP Christopher Mayhew took mescaline hydrochloride in an experiment under the guidance of his friend, Dr Humphry Osmond. On the BBC documentary, The Beyond Within, he described that half a dozen times during the experiment, he had "a period of time that didn't end for [him]".

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. Dopamine has a particularly strong connection with one's perception of time. Drugs that activate dopamine receptors speed up one's perception of time, while dopamine antagonists cause one to feel that time is passing slowly.

Numerous experimental findings suggest that temporal order judgments of actions preceding effects can be reversed under special circumstances. Experiments have shown that sensory simultaneity judgments can be manipulated by repeated exposure to non-simultaneous stimuli.

In an experiment conducted by David Eagleman, a temporal order judgment reversal was induced in subjects by exposing them to delayed motor consequences. In the experiment, subjects played various forms of video games. Unknown to the subjects, the experimenters introduced a fixed delay between the mouse movements and the subsequent sensory feedback. For example, a subject may not see a movement register on the screen until 150 milliseconds after the mouse had moved. Participants playing the game quickly adapted to the delay and felt as though there was less delay between their mouse movement and the sensory feedback. Shortly after the experimenters removed the delay, the subjects commonly felt as though the effect on the screen happened just before they commanded it. This work addresses how the perceived timing of effects is modulated by expectations, and the extent to which such predictions are quickly modifiable.

In an experiment conducted by Haggard and colleagues in 2002, participants pressed a button that triggered a flash of light - at a distance - after a slight delay of 100 milliseconds. By repeatedly engaging in this act, participants had adapted to the delay (i.e., they experienced a gradual shortening in the perceived time interval between pressing the button and seeing the flash of light). The experimenters then showed the flash of light instantly after the button was pressed. In response, subjects often thought that the flash (the effect) had occurred before the button was pressed (the cause). Additionally, when the experimenters slightly reduced the delay, and shortened the spatial distance between the button and the flash of light, participants had often claimed again to have experienced the effect before the cause.

Several experiments also suggest that temporal order judgement of a pair of tactile stimuli, delivered in rapid succession, one to each hand, is noticeably impaired (i.e., misreported) by crossing the hands over the midline. However, congenitally blind subjects showed no trace of temporal order judgement reversal after crossing the arms. These results suggest that tactile signals taken in by the congenitally blind are ordered in time without being referred to a visuo-spatial representation. Unlike the congenitally blind subjects, the temporal order judgements of the late-onset blind subjects were impaired when crossing the arms to a similar extent as non-blind subjects. These results suggest that the associations between tactile signals and visuo-spatial representation is maintained once it is accomplished during infancy. Some research studies have also found that the subjects showed reduced deficit in tactile temporal order judgements when the arms were crossed behind their back than when they were crossed in front.

Parkinson's disease, schizophrenia, and attention deficit hyperactivity disorder (ADHD) have been linked to abnormalities in dopamine levels in the brain as well as to noticeable impairments in time perception. Neuropharmacological research indicates that the internal clock, used to time durations in the seconds-to-minutes range, is linked to dopamine function in the basal ganglia. Studies in which children with ADHD are given time estimation tasks shows that time passes very slowly for them. Children with Tourette’s Syndrome, for example, who need to use the pre-frontal cortex just behind the forehead to help them control their tics, are better at estimating intervals of time just over a second than other children.

Parkinson's disease, a degenerative condition causing tremor and motor impairment, is caused by a loss of dopamine-secreting neurons in an area of the midbrain called the substantia nigra. Its metabolic precursor L-DOPA can be manufactured, and in its pure form marketed as Levodopa is the most widely used treatment for the condition. In his book "Awakenings", Oliver Sacks discusses how patients with Parkinson's disease experience deficits in their awareness of time and tempo. For example, Mr E, when asked to clap his hands steadily and regularly did so for the first few claps before clapping faster and irregularly; culminating in an apparent freezing of motion. When he finished, Mr E asked if his observers were glad he did it correctly to which they replied "no". Mr E was offended by this because to him, his claps were regular and steady. When given L-DOPA, these deficits are lessened or subside entirely depending on the dose. This case not only shows that Parkinson's disease is related to time perception deficits but it also demonstrates how dopamine is involved.

Restless legs syndrome and attention deficit hyperactivity disorder (ADHD) are associated with decreased dopamine activity. Dopaminergic stimulants can be addictive in high doses, but some are used at lower doses to treat ADHD. Specifically, dopaminergic systems are involved in working memory and inhibitory processes, both of which are believed central to ADHD pathology. Children with ADHD have also been found to be significantly impaired on time discrimination tasks (telling the difference between two stimuli of different temporal lengths) and respond earlier on time reproduction tasks (duplicating the duration of a presented stimulus) than controls.

There is evidence that schizophrenia involves altered levels of dopamine activity, and most antipsychotic drugs used to treat this are dopamine antagonists which reduce dopamine activity. Along with other perceptual abnormalities, it has been noted by psychologists that schizophrenia patients have an altered sense of time. This was first described in psychology by Minkowski in 1927. Many schizophrenic patients stop perceiving time as a flow of causally linked events. It has been suggested that there is usually a delay in time perception in schizophrenic patients compared to normal subjects. These defects in time perception may play a part in the hallucinations and delusions experienced by schizophrenic patients per some studies. Some researchers suggest that "abnormal timing judgment leads to a deficit in action attribution and action perception."

  • I just happened to see the last episode of the Cosmos yesterday. Very nice takes on the some fascinating subjects. Spacetime wasn't really questioned there. Julian Barbour, however doesn't see it nucleus of the problem, one should rather concentrate to find out, how we define and make clocks to work. Anyway, thanks for putting some brain and neurological perspective to the topic, I've been waiting for it quite a long time.
    – MarkokraM
    Commented Nov 11, 2016 at 14:31
  • 1
    This is way too long to be appropriate for the SE format. Please edit it down.
    – virmaior
    Commented Nov 13, 2016 at 9:18
  • If you think that Einstein was not a great "out of the box" thinker, try to understand things like that there can not be two events at the same time in different places. That alone is so far out of the box that you will not even see the box. Commented Mar 16, 2018 at 14:35

To understand Time is a physical entity OR Mathematical dimension

We need to understand the Dimension first:

Dimension: It can be defined as the measure of a particular property of an entity.

Basic dimensions: Mass, Length, Time, Temperature etc.

We can clearly make a distinction for spatial dimension; Length is just a mathematical dimension but certainly not a physical entity. Basic dimension and mathematical entities cannot be regarded as not physical entities, for example, length of a line is not a physical entity itself and length of a box where box is a physical entity.

Time: It is a mathematical dimension to measure the change of state (any motion) of Existence (includes universe/multiverse).

Space: It is a mathematical dimension to measure the spatial expanse of Existence (includes emptiness and non-emptiness).

If Time and Space will be considered just as mathematical dimensions to measure Existence then the application of these dimensions will need a physical entity to be applied upon. In this case, Existence and part of the existence is the only physical entity.

Existence: It includes universe/multiverse, it can be defined as a self existing multi-dimensional entity, infinite in nature, it consists of all other entities that ever existed or existing now or will exist; such as matter, antimatter, waves, energy, force fields, spatial expanse (includes emptiness and non-emptiness) etc.

Non-Existence: It can be defined as an entity that never existed, nor existing now and will never exist.

It can be a little confusing that “Non-Existence” word exists. As mentioned earlier these words are just a symbol to represent non-existing but not the actual entity.

Now there is a term physical Spacetime based on Einstein's theory of relativity

In mathematical physics, Minkowski spacetime is a combination of three-dimensional Euclidean space and time into a four-dimensional manifold where the spacetime interval between any two events is independent of the inertial frame of reference in which they are recorded. Although initially developed by mathematician Hermann Minkowski for Maxwell's equations of electromagnetism, the mathematical structure of Minkowski spacetime was shown to be an immediate consequence of the postulates of special relativity.

Minkowski space is closely associated with Einstein's theory of special relativity and is the most common mathematical structure on which special relativity is formulated.

Source: https://en.wikipedia.org/wiki/Minkowski_space


Time is the sequence of existence, whatever it is you want to call it, of the creation.

In order to discuss I redraw the framing definitions in consideration those provided were properties.

  1. Time is a measure of duration where we observe change. Change is the reduction of possibility.
  2. Time is a specific point in the extent of the duration of existence that we can identify. History is a record of what has happened at some time and place in history with whatever partial or impartial details are with the record.
  3. Time has a property of scale that we note as being the relativity of time.

Time is the sequential annotation of the reduction of possibility. In the beginning of time all possibility can exist. There is yet nothing to reduce possibility other than the formation of the beginning of creation. Every possibility leads forward in time to its moment of vote or veto thereafter possibility is reduced and the actions surrounding either reform or sand the possibility nonetheless thereafter being that decided possibility is reduced.

There is not introduced new possibility. The possibility for some thing to be or not be was existant at the beginning of the existance where the possibility exists until it is later decided. This process where we observe the sequence of the reduction of possibility is time and the passing of time we mark with regularity.

In history all events are fixed. All that has already happened is certain. The events are so certain they are concrete and marble and they do not erode since possibilty there has been permanently and without withdrawal affected. The future is yet to be the result of what possibility remains to that moment, be it choice, where it must be vote or veto thereafter.

To observe all that is possibility that we do not, picture the cardboard tube for the representation of time, in that at the beginning the thick trunk of a tree and the branches that spread out to represent all of possibility that we do not have since they do not continue. Time is like a column of Iron growing out of a tree.

Eventually, to anser all of why is to close time for it is so much we cannot know everything but there it is. - KING JAMES HRMH 25/08/2021 2:30pm



Time as a concept is a relationship between things "relation of change of the state of a thing from state1 for example toward a state2 such as state1 do not have every property of state2", it doesn't exist on itself like other physical things "Rocks" "Birds" etc. But its existence is ontologically depending on things that make that relation and it exists by the existence of those things. Sorry for my poor English i hope that the answer is understandable.


Time itself manifests itself as being an irresistible flow of a fluid like (non existent: but helps in imagination) substance, that is dynamic (relativity and time dilation). It comes into being and assumes it's identity of being an inevitable flow towards tomorrow and escape from the past only because we live inside Spacetime, already written out in it's full-at least that is what Eternalism says in physics, with the view of a block universe.

It says that all 4D spacetime is like a CD-information already recorded, but since we are inside the spacetime block, (the 4D thing) we perceive it as constantly unfolding itself according to the consequences of our actions, while the reality might be extremely different, with by necessity, free will infringed (so that in a particular universe, only a set of events seem to unfold which have already been recorded on the CD).

Maybe our free will is infringed wholly or to an extent, and may be, as a compensation from the un-intelligent (non conscious like us humans) universe, there are out there infinite block universes that have data in them that would unfold as a result of the infinite combinations of human action.

Now, for presentism, which IMO, says that the present is constantly evolving into the future as we would know it moments later, and it ceases to have a separate existence of it's own out there (+can only be accessed by beings far enough where the light of our present hasn't yet reached).

The future arises from expectations and evolving present-the table you see in the present will be the same one 10 second later, just that if you shift it, then nowhere in the universe would the table still be having separate physical existence forever at the original location-even the alien will eventually see the future of the table- and also from changing present situations. The past exists in memories, accessible to aliens only for seeing, not for changing it.

Now, for the ***definitions *** of time, we have no concrete. A few:

  1. Difference between then and now

  2. That thing (although we can't even define a thing) which inevitably takes you to tomorrow (it doesn't stop-but is dynamic according to relativity)

  3. That thing (again) which makes you perceive bodily functions such as excretory etc.

But note: The measure of time without being conscious or alive in the sense as much as you are now has no meaning: it cannot measure time or the rate at which it flows: it can't even know of it's own existence!


I read "How to add 90 billionths of a second to your life....." and read in that article that times runs faster when a clock is raised a bit higher, 12 inches. But that does not mean that time runs faster but that the clock runs faster. Maybe something was wrong in 'the measurement of time'. Some psychiatrists are claiming that time is a complex concept. In physics time is related tot the geometrical position which is different from what we experience daily. That time is ordered as real numbers are and that it can be used in calculations as if it is a length makes it, to my opinion, strange. That it can't be a measure for change is already written, turning around a center does not alter the position after a full turn but time has gone.

  • 1
    This answer doesn't look to be philosophically informed at all...
    – virmaior
    Commented Nov 8, 2015 at 0:40

Time is a physical factor and the term used to capture this concept is the word 'TIME'. You attempt to give 3 different definitions that appear to need reconcilation. I would submit these are not equal definitions of the 'concept' time which has an experiential factor.

Time, is a term that captures the concept of change, and can include a measure for reference.

Time as a 'consciousness' is - sorry to say - mumbo jumbo. This is mixing concepts in an imprecise way to capture some separate 'emotional state'. History is not relevant to the concept of time. History is by-product of the 'passage' of time.

Edit: To expand my use of 'mumbo jumbo' I will say that 'time' is a term with a more precise or concrete definition and usage. Humans mix metaphors like 'I felt time slow down...' but here the concept of time is trying to share a feeling. Time is the anchor to hang the feeling on. Like 'cold as ice.' Consciousness is the more subjective term which includes less concrete usage and clarity. Consciousness can be used to describe the act of awakening my mind and body, or my mind only like Descartes great leap of reason driven by consciousness. Only then consciousness is used loosely in medical terminology or when describing the interaction with an animal that 'feels' human like or touching. One might say the animal felt conscious. Then you have collective conscious, higher conscious, stream-of-conscious that all use conscious in a slightly different way. So 'mumbo-jumbo', used here, is what I would call the new age practice of using more precise terms to lend legitimacy to less precise terms and ideas. [ I read a lot of philosphy so this is not my idea... but I cannot site reference ]

Time is relative - is saying that time exists and that it is experienced differently.

Two of your definitions capture and refine the definition of time and answer the question in the affirmative that Time is both a concept and physical.

  • 5
    You can't just call something "mumbo jumbo" and leave it at that. If you're going to dismiss a theory, you need to provide some reasoned argument that explains your objection. In particular, your answer is missing the part that explains why this is "mumbo jumbo", why "history is not relevant to the concept of time", why "history is [the] by-product of the 'passage' of time". Please consider improving this answer by editing it to include some citations. Commented May 2, 2012 at 8:18
  • Do you say, that the feel of time going fast when you are in a flow, slow or extra slow on accidents for example, choppy and so forth is not a true perception for all people that claim so? Do you say, that there is no use for historical knowledge, how people understood time in past? I think one cannot just throw away the psychological side of the time definition. May it relate to human biology like memory, senses, consciousness or anything. Its not anything special, that same term is used widely on different domains. One just needs to specify and understand the context to avoid impreciseness.
    – MarkokraM
    Commented May 2, 2012 at 9:21
  • PHPGAE: For precision I do not equate historical knowledge directly with understanding or sensing time. To say 'cave men had no sense of time' is mixing imprecise ideas. Modern understanding of historical events take place within a period time, but here again time is an anchor. Time is the spaces on a ruler that box and shape understanding. But this is not the definition of time. Time produces no more feelings than the number '3'.
    – E Toohery
    Commented May 3, 2012 at 3:26
  • I think admins rewrite of my initial 2nd definition of time caused some misunderstandings. What I meant with history was past as opposed to present and future. Subject is dealt deeply on book "Time and Memory: Issues in Philosophy and Psychology":
    – MarkokraM
    Commented May 3, 2012 at 18:56
  • 1
    I also happened to read a definition for four noble arts & sciences called Quadrivium, that can be represented by a relation to time: 1. mathematics (art of pure numbers) 2. geometry (art of numbers in space) 3. music (art of numbers in time) and 4. cosmology (art of numbers in time and space) Now who says, that time cannot be handled as a philosophical or psychological subject in addition to physical one? I could almost say that time is the least physical subject when compared these three aspects.
    – MarkokraM
    Commented May 3, 2012 at 19:04

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