What is time?

by Marianne Freiberger

In the latest poll of our Science fiction, science fact project you told us that you wanted to know what time is. Here is an answer, based on an interview with Paul Davies, a theoretical physicist and cosmologist at Arizona State University and Director of BEYOND: Centre for Fundamental Concepts in Science. Click here to see other articles on time and here to listen to our interview with Davies as a podcast.


What is time?

Everyone knows what time is. We can practically feel it ticking away, marching on in the same direction with horrifying regularity. Time has enslaved the Western world and become our most precious commodity. Turn it over to the physicists however, and it begins to morph, twist and even crumble away. So what is time exactly?

To many people throughout history time would have been synonymous with the rhythms of nature; the passing of the seasons and the cycles of the celestial bodies. If this idea seems naive today, it's not only because modern clocks are infinitely more accurate time keepers than the celestial bodies ever were. It's also because we've come to think of time as something universal, something that would keep marching on even if all clocks, celestial or man-made, were to stop. The notion of an absolute time, one that's measurable and the same for all observers, was expressed most succinctly by Newton: "absolute, true and mathematical time, of itself, and from its own nature, flows equably without relation to anything external."

Einstein's time

Newton's absolute time may feel like an accurate description of the beast that rules our daily lives, but in science the notion was shattered in 1905 by Einstein's special theory of relativity. "Einstein showed that there isn't a universal time," explains Davies. "Your time and my time get out of step with each other if we move differently." In other words, the duration of time between two events can vary depending on how fast you are moving in the period between the events.

a diagram of the mirrors

Imagine two observers, one on a train and one stationary. The traveller sends a pulse of light from a torch vertically up. The traveller's view is shown on the left: the pulse travels vertically up. The stationary observer's view is shown on the right: the position of the torch and train ceiling at the start and end of the pulse's journey are shown in black and blue respectively. The pulse travels diagonally.

At the root of this strange time warping effect lies Einstein's postulate that the speed of light should be the same for all observers, no matter how fast they are moving. Imagine two observers, one travelling on a train and the other stationary by the side of the tracks. As the two pass each other the traveller emits a pulse of light from a torch shining vertically up. The two observers will disagree on the distance the pulse has travelled when it hits the ceiling of the train, because the stationary observer perceives not just the vertical motion of the pulse, but also the horizontal motion of the train.

Since both observers measure the same speed of light, and since speed is distance per time, this implies that they must also disagree on the time it took the pulse to travel that distance. Time is relative to the observer, or as the physicist Kip Thorne prefers to put it, time is "personal". (For a more detailed description, read the Plus article What's so special about special relativity?.)

We don't notice this time dilation in daily life, but it's not so small as to be unmeasurable. "If I fly from Phoenix to London and back again, and then compare my clock with that left in the office, they will be out of step with each other by a few billionths of a second," says Davies. That's a tiny amount for humans, but it's well within the measuring capability of modern clocks.

In fact, time dilation has a real impact on the global positioning system (GPS), which many of us have come to rely on for navigating around the world. "The system works with orbiting satellites that are moving very fast," explains Davies. "If you didn't factor in this time distorting effect of motion, then your GPS would very quickly begin to accumulate errors so that in an hour or two you'd be lost. So this is a real effect, not just some sort of mad mathematician's nightmare."


An artist's impression of the Sun warping spacetime and the Cassini space probe testing relativity by measuring how signals are delayed by the warping. Image courtesy NASA.

But motion isn't the only thing that can distort time. In his general theory of relativity, published in 1916, Einstein showed that gravity too can slow time. Rather than thinking of gravity as an invisible force that wafts across the ether, Einstein thought of it as the effect of massive bodies distorting the very fabric of space. A famous analogy is that of a bowling ball sitting on a trampoline, which creates a dip that a nearby marble will roll into. According to general relativity, massive objects like stars and planets warp space in a similar way, and thus "attract" other bodies that pass nearby. However, Einstein realised that time and space are inextricably linked in what he called spacetime, so the warping effect of gravity does not just effect space, but also time.

"Gravity slows time, so that it runs a little bit slower in the basement of your house than it does on the roof," says Davies. "It's a tiny effect, but it can be measured, even on distances that are that small. But if you want a seriously big time warp from gravity, you have to go where there's a very big gravitational field. If you had a clock on the surface of a neutron star, for example, it would tick at about 70% of the rate of a clock on Earth. The ultimate time warp is at the surface of a black hole, where in a sense time stands still relative to our time. If you went there, you wouldn't notice anything peculiar about time, but if you compared clocks between the two locations, they'd be enormously out of step."

Einstein drew an interesting conclusion from his results about the nature of time. In a letter to the family of a recently deceased friend, Michele Besso, Einstein wrote, "... for us physicists believe the separation between past, present, and future is only an illusion, although a convincing one." Since time is relative to the observer, it is impossible to divide it up into past, present and future in a way that is universally meaningful. In some sense, past, present and future are all there at once.

"This notion is sometimes called block time, but I like to call it the timescape because it's a bit like a landscape," says Davies. "If you look at a map, the whole of the landscape is there before you, all at once. If you add time as the fourth dimension on this map, then all of time is there at once too. The fact that nothing in physics singles out a particular 'now' is a mystery."

Incidentally, there is nothing in Einstein's theory that prohibits time travel, be it into the future or into the past. But this is a can of worms we won't open here, as you can read about it in Kip Thorne's Plus article Is time travel allowed? (or read Davies' book How to build a time machine).

The arrow of time

Thinking of past and future brings us to another problem that has foxed scientists and philosophers: why time should have a direction at all. In every day life it's pretty apparent that it does. If you look at a movie that's being played backwards, you know it immediately because most things have a distinct time direction attached to them: an arrow of time. For example, eggs can easily turn into omlettes but not the other way around, and milk and coffee mix in your cup but never separate out again.

Listen to the interview with Davies in our podcast!

The most dramatic example is the history of the entire Universe, which, as scientists believe, started with the Big Bang around thirteen billion years ago and has been continually expanding ever since. When we look at that history, which includes our own, it's pretty clear which way the arrow of time is pointing.

"But the mystery is that the laws of physics show no preference for forward time or backward time," says Davies. For example, if you can make an object move one way by applying a force, then, as Newton's second law of motion tells you, you can make it retrace its path by applying the same force in the opposite direction. So when you watch a movie of this process you wouldn't be able to tell if it's being played forwards or backwards, as both are equally possible.

"So the problem is how to account for the asymmetry of time in daily life when the laws that govern all the atoms that make up everything around us are symmetric in time," says Davies. Much has been made of this problem, which affects Einstein's physics just as it did Newton's classical description of the world.

Hand of cards

Order or disorder?

But the answer isn't all that difficult to find. Most processes we feel are irreversible in time are those that (for whatever reason) start out in some very special, highly ordered state — Davies uses a pack of cards as an example. When you first open up a new pack the cards will be ordered according to suit and numerical value. When you shuffle them for a while they will become disordered, so it seems that, as time passes, things will always move from order to disorder. "We might think that this is very strange because there is nothing in the act of shuffling that chooses a direction in time, yet we see a distinct arrow," says Davies.

However, there is nothing in the laws of physics that prevents the act of shuffling from producing a perfectly ordered set of cards. It's just that the ordered state is only one of a total of around 8 × 1067 possible states, so the chance that we come across it while shuffling the cards is vanishingly small. So small that it would never happen even within several lifetimes of shuffling.

So the apparent asymmetry of time is really just an asymmetry of chance. Systems of many components — like a cup full of milk and coffee particles or a bowl full of egg particles — evolve from order to disorder not because the reverse is impossible, but because it's highly unlikely. This, in a nutshell, is the second law of thermodynamics, which states that the entropy (a measure of the disorder) in a closed physical system never decreases. It's a statistical principle, rather than a fundamental law describing the behaviour of individual atoms. The apparent arrow of time emerges as a property of the macroscopic system, but it's not there in the laws that govern the individual particle interactions. As the physicist John Wheeler put it, "If you ask an atom about the arrow of time, it will laugh in your face."

This also applies to the whole Universe. "The Universe started out very smooth and expanding uniformly," says Davies. From a gravitational view point the Big Bang was a low entropy state and the Universe has been increasing its entropy ever since, hence the arrow of time. The question now is why the Universe started in the way it did. "Why our Universe went bang in such an ordered state is still a mystery," says Davies. "There is no agreed answer to that, partly because there is no agreed model of cosmology. We all think the Universe began with a Big Bang and we know it's expanding. What we don't know is if the Big Bang is the ultimate origin of time or whether there was a time before that." (Read the Plus article What happened before the Big Bang? for more on this subject.)

Time disappears

What would you like to know next?

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One thing we have neglected to say so far is that Einstein's theory, which describes the macroscopic world so admirably well, doesn't work for the microscopic world. To describe the world at atomic and subatomic scales, we need to turn to quantum mechanics, a theory that's fundamentally different from Einstein's. Reconciling the two, creating a theory of quantum gravity, is the holy grail of modern physics.

When Schrödinger and Heisenberg formulated quantum mechanics in the 1920s, they ignored Einstein's work and treated time in Newton's spirit, as an absolute that is ticking away in the background. This already gives us a clue as to why the two theories might be so hard to reconcile. The status of time in quantum mechanics has also created profound problems within the theory itself and has lead to "decades of muddle and subtlety," as Davies puts it.

We won't go into this muddle here, but we'll note the conundrum that unfolds when you try to apply quantum mechanics to the Universe as a whole (a rather controversial approach not all physicists agree with). "If you try to write down a quantum mechanical description of the whole Universe, you find that the time parameter actually drops out [of the equations], it's not there at all," says Davies. Time is replaced by correlations. "For example, you might have a correlation between the size of the Universe and the value of some [physical] field. We would describe this by saying 'as the Universe evolves over time and gets bigger, so this field changes in value'. We use that language, but actually all you're talking about is a correlation [between physical quantities] and time can be removed completely."

Some people have interpreted this to say that time doesn't exist at all, but Davies disagrees. "I think time exists just as telephones do. It's a real thing and we can measure it. But it does suggest that the way it enters into our description of the world is different from other quantities we're used to."

One possibility is that time, and also space, are emergent properties of the Universe, which are not part of the bottom level of reality. "It may be that for the extreme conditions at the Big Bang a description in terms of other variables is more appropriate. When we see the world with a well-defined space and time [or spacetime as Einstein put it] this may just be some particular state of the Universe that has emerged out of the Big Bang." Davies uses a block of rubber as an example: it's got its very own physical properties, its elasticity for example, but these properties aren't there at the atomic level. They are a result of the atoms and the laws that govern them combining in one particular way. Similarly, the Universe, as it cooled down from the Big Bang, may have just happened to give rise to spacetime. Perhaps, if it had cooled down in another way, spacetime wouldn't have come up.

rubber ducks

Rubber ducks have emergent properties.

But if space and time aren't fundamental, what are the fundamental properties of the Universe? There is no theory that people agree on. "We can invent words to describe them and people have, but these things are not anything we are going to encounter in daily life. So we're just resorting to [mathematical descriptions]. But even if one day we manage to explain time and space in terms of something else, that only pushes the question to another level, because you then have to explain [the something else]."

So it seems that we're no closer to understanding what time is than Newton was — perhaps we understand it even less. But then, perhaps the job of the scientist isn't to fully explain the Universe, but merely to describe it. "You postulate a theory, usually in the form of mathematical equations, and then you test it against reality," says Davies. "If it does work, you don't argue where those equations come from. It's just your best attempt to describe the world."

Whether it's fundamental, emergent, or just a set of correlations in disguise, the fact is that something we call time manifests itself undeniably and we all know about it. As a friend of mine put it, "If you want to know what time is, just look at my face."

About this article

Paul Davies

Paul Davies

Paul Davies is a theoretical physicist and cosmologist at Arizona State University and Director of BEYOND: Centre for Fundamental Concepts in Science. He has worked in a number of different fields, including cancer research and astrobiology (Plus has interviewed him on astrobiology in the past) and has written a large number of popular science books, including About time: Einstein's unfinished revolution and How to build a time machine.

Marianne Freiberger, co-editor of Plus, interviewed Davies in July 2011.


TIME DOESN’T EXIST? - John Longman

- I have a few thought about your reflexions about Time:
What if ‘time’ does not exist:
What we call speed or velocity is not the rate of change of distance with respect to time, but simply the change of position with respect to Space.
Objects do not move over time (because time does not exist). Objects simply move in Space. This started with the big bang.
What we perceive as time is a product of our minds which have the capacity to :
-retain mental images of positions of objects that we have observed.
-extrapolate the positions of objects if they continue on their existing paths
The concept of 'time' is thus purely an abstract idea that we humans have introduced to explain the fact that we observe positions of objects changing.
The fact that objects move and interact with each other is surely sufficient to explain all the phenomenon we observe in the universe without need for the concept of time.
At the Big Bang, objects and energy start moving in Space, and that movement resulted in all states of the universe that have been observed. There is no need for ‘time’ to explain this, just the laws of nature together with motion through space.
This would mean that time travel does not exist (because time does not exist).
However, we could re-visit any former state of the universe simply by putting all the objects in the universe (down to the molecules, and sub-atomic particles in our brains) back in the positions they held in space (with the same momentum, energy etc.. that they had when they were in those positions).
And, to create any ‘future’ state of the universe we simply need to move all objects in it to the place that we extrapolate them to be in at a later state of their motion through space.
The only barrier to this kind of ‘time travel’ is that in practice it would be difficult to move all that stuff (everything in the universe) to its previous or expected position.
Thus, time does not exist – If I want to go back to a 'time' when my Mother was alive, for example, all I need to do is move particles to the correct positions in space corresponding to that state of the universe.
If I simply did that, she and I would inevitably be having the same thoughts, and memories as we had the first time. And we would effectively have travelled back in what we call ‘time’ but which is, in fact, just a previous position of objects and energy in space.
Maybe it would simplify the equations of cosmology and quantum mechanics if we re-visited them from the perspective described above.
- I would be very interested to know what you think about the ideas I have expressed above.

What is time

Time is the matrix of information permeating space. There are many subjective interpretations that describe different and similar aspects of the phenomenon that lies at the basis of reality. This is my opinion.

What is Time?

A query which puzzles me:
(1) In Einstein's Clock shown moving through Space, the light is shown travelling vertically between the moving mirrors. Since the light travels through Space independently of the Clock and will receive no impetus from the movement of its source, from whence does it get the same magnitude and direction of movement relative to external Space as the mirrors? Therefore why does it not appear to move rearwards over a longer path relative to the mirrors rather than being carried forwards relative to the stationary observer?

The unstated premise of the

The unstated premise of the thought experiment is that the light ray's movement IS dependent on the movement of its source. If it was independent of the speed of the source, then the observer on the train would detect a shift in the contact point relative to the emission point. This is not observed when the source is moving at constant speed. But it is observed when the source is accelerating.

What is time?

There is intuitive time and there is physical time. Intuitive time is our own sense of time, which results from the rhythmic activity of our brains and body. I doubt it's a coincidence that one heartbeat of the average person is about a second long. It may even be that the duration of a second was based on the heart rate of some important individual (king, emperor, revered philosopher, etc). Virtually every animal, especially predators, must have an intuitive sense of time because a lung needs to be timed, a pursuit trajectory has to be timed in order to meet the prey in its trajectory. Our intuitive sense of time is also dependent upon memory. The charging predator has to remember what it felt and saw a split second prior to now in order make a correction in its trajectory. We are most aware of time when we remember past events. Because of this, we are seduced into thinking that time has an objective reality. It does not.

What we would call physical time is the time we think we are measuring with our clocks. But all we are really doing is substituting a more consistent device for our heart, our firing neurons, our memory, the movement of the sun's shadow on a sundial, the cycles of the moon, etc. All we are doing with clocks is establishing what we believe is a cyclical device that is highly consistent--a standard. And then we measure all other movements of matter and energy in space as a ratio of the object's distance traveled to the "distance" traveled by the clock, i.e., velocity. I say "distance" because many clocks we have developed have no moving parts.

But how did we establish a system for determining, to a high probability, that a particular device or process is highly consistent? There are at least two ways: By converting its cyclical output into a linear form that can be measured with a "yardstick"--a measuring device that is consistent and objective. A cyclical output can be fed into an electronic oscilloscope which would display it as a sign wave. Observation and measurement of many cycle lengths can establish its consistency. Another way is to make a large number of physically identical devices which, when operated, would be initially synchronized, then observed over many cycles and note taken of how much a-synchronicity develops among them. None of these processes are dependent upon a preconceived standard of time. In fact, what we have developed are highly consistent standards of movement to which all other movement are compared.


The word I intended was lunge, not lung, obviously. Also, it's supposed to be "sine wave" not "sign wave".

Addendum to my post:

One might ask, why cyclical movement rather than linear movement? There were at least three types of linear measure used in the past: A burning rope with spaced knots, a burning candle and dripping water. These have obvious drawbacks. On the other hand, a cyclical standard does not need to be consumed, and the beginning and end of a cycle remains within close proximity to the observer.

To expand on my statement that some clocks don't have moving parts: Mechanical parts, yes. But even electronic clocks function by means of the movement of energy and matter. Electrons move through circuits, Logic gate resistance changes when an electrical potential is present or removed, which is movement in the atomic structure, even though slight.

interval between two events.

I don't know what prevents us from concluding that time is the interval between events or it is the sequential order of events. That is, in an isolated system or frame of reference if no events are occurring, time must come to a standstill !


that is just like saying if a tree falls in the jungle and no one around does it make a sound. so assuming we are all alive, and continue to be for the duration time is being considered, no events need to occur except our being alive but cant you see thats the very essence of it. time exists and the tree makes a big racket and we all may give the impression of being dead but are actually alive.

Time is a tool.

Interesting how many comments there are on this topic!
I will reiterate and try to simplify other posts;
Like distance-measuring tools which use standardized lengths to describe distance, time is standardized motion (Falling grains of sand, number of blinks, atomic oscillations, planetary rotations, etc.) that is used to describe motion.
All the elements of "spacetime" are required to describe motion; x,y,z,and t, which leads me to believe that motion is the basic nature of the uni(?)verse.
I believe Einstein was simply showing that time could not be used as a constant due to differing perceptions of time based on the relative orientation of observers. He suggested the speed of light as a constant and things got screwy when it was found that gravity deflects photons... Hard to find a good vantage point to observe from when your planet is spinning while orbiting a star that is orbiting a black hole that is streaking through the universe...

Time is ...

Time is simply the perception of change in a particular direction... Without consciousness there is no time!

Time as Free will?

What if time is simply a byproduct of consciousness? If the universe is infinite, containing all possibilities, at once, then all consciousness is consciousness of the universe, itself, and the only way consciousness could exist would be for the universe to narrow its "view" of itself to the degree that it cannot perceive itself, as a whole and create an illusion of "me/not me" that would represent the absence of itself and create the contrast necessary for recognition and self-awareness. What if "time" is simply the byproduct of the illusion that "things" exist, separate from other things (and the whole) as its attention moves from one narrow perspective, to another - so that the perception of time is merely a consequence of the illusion that creates the contrast that allows recognition and, thereby, consciousness?

It would also stand to reason, under these conditions, that every individual possibility - be it a thought, a particle or a galaxy - would contain the exact same capacity to allow the universe to perceive itself from that perspective. It would be able to perceive from the perspectives of all possibilities and choose any of an infinite number of possible "objects of attention" from any perspective within each of an infinite number of possible "ranges". Some of which may require a perception of something like "time" and some of which may not.

Crikeys! I swear - that really does make sense, in my head! LOL!

Time as Free will

Here is a similar related 'what if'. Since the universe is experienced by consciousness (spirit), it is reasonable that spirit is not of the spacetime energy-matter category. Spacetime energy-matter is like a wind-up toy that is running down (and is pure effect of the big bang). Spirit is the of the opposite category in that it animates and creates highly organized life forms, thoughts, dreams, etc. Spirit is of a create category. If we take spirit to the extreme pure definition (and not as spirit is found in the hybrid spirit-matter form of a human being) then spirit is an infinite creation source whose gentlest touch brings anything into existence. We can imagine that, in pure form, the spirit's creation is without time, and that time is just a peculiarity of this universe. In that pure state, spirit would not experience or have anything in the sense that we have things in a universe with spacetime. In order to 'have' something, spirit would need to differentiate some part of it's creation as 'over there'. And to keep it 'over there', a continuous running series of changes (new but similar differentiations) are needed to get a persistence of 'over there'. If the creation is not sufficiently changing, then it too easily is just an integral part of spirit, timeless and not persisting as per the things of this universe. There is no time for an infinite spirit, but by purposely differentiating some space in a complex pattern of similar states, and associating those states in a sequence of one state coming after another, time is created. Each space that was differentiated is slightly different, in size, distortions, etc. Perhaps vibrations within vibrations such as in elementary particles. Even though each space was created without time (and for ease of thinking, lets just say they are all created at the same 'moment') the spaces are all considered to have a sequence of one 'after' another, and thus they can be 'had' because they persist in 'time'. Time is an artificial association of states of space (experiences) into a progressive sequence that helps to keep space differentiated and persisting.

Time as displacement

Ultimately, it seems to me, a fundamental aspect of the universe is real if, in principle at least, it can be measured either by comparing two quantities of it or observing its impact on a recording device. Time has always been measured indirectly through movement, be it of heavenly bodies, sand, melting wax, pendula, cogs, electric current or atomic oscillations. But no one to my knowledge has ever compared one second to another, or recorded the effect of varying quantities on a device, as we are limited to a presumption that movement over the same distance takes the same amount of time. Therefore, we can not even show that this artifice of time runs at one second per second. Notwithstanding 'highly accurate' atomic clocks changing state billions of times a second we are unable to demonstrate that one lot of oscillations took as long as the previous without first assuming the very quantity we are trying to measure. Distance, or rather displacement (an earlier post says change), is the actual observable effect with no tangible evidence to relegate it to mere proxy status for time. Is this a defeat not conceded in the move to redefine time as a distance travelled by light? In what sense then is time a dimension commensurate with space?


Time is simply a product of the motion of a mass or energy through space. "Time" isn't anything, it's just a phenomenon we use to measure durations, standardized using radiometric decay. As well, time is relative based on the local conditions of your location in the universe. Photons (processes) occur at differing rates based on gravity, so your speed may not be my speed...:)


Well comparing one second to another is like comparing one meter to another- they better all be the same by definition, otherwise measurement becomes meaningless. Varying quantities of time on a device does have impact- particles move, photons are exchanged, etc. At a small enough level, this all happens quite randomly- we would observe a number of very different states if we were able to examine this device very closely at several different "times". The point is that a second -just like a meter- is NOT absolute: one second of my time will not always be the same as one second of your time, and neither will the distance we measure between any two points we agree on.

Without going into existential philosophy on the nature of reality (that will muddle the content of this post), time as a dimension makes perfect sense. Take the state of our entire universe as it is right now- that is one instant of time dt (there are also, I think, theories that time is quantized- let's pretend it's not for now). One dt later, a number of things will have changed. As we move along this mathematically linear axis, we obtain some 4-dimensional function. Or, if it's easier, one can reduce our 3 spatial dimensions to 2- then, picturing whatever 3-d shape is most convenient, we can stack up "slices" of this 2-dimensional universe to obtain a 3-dimensional shape.
Just as displacement in space is a noticeable effect, I think displacement in time is, arguably, also noticeable. Going back to the graphical model, I can notice my displacement through time by remembering an older time, perhaps when I was in the same place. "x" number of minutes ago, I was sitting here and this white box on my screen was blank. Now, "x" minutes later, it is full of characters. Along the way, if we imagine increasing values of "t" as we go along, we would see me typing this message. The main difference is that time is not physically perceivable- I cannot simply look at something and say that it is a number of seconds long. And also, we can thus far only move in one direction through time.

Time as displacement

Thanks for the response to my post. May I attempt to clear up some confusion I may have caused by referring to seconds?
We do not have to consider man-made units or different reference frames, I can directly compare any length with any other length relatively easily (in principle at least) but how do I compare one stretch of time with another except indirectly by referring to relative changes in position? Moreover, I do not have to assume spatial relativity, it presents itself to at least two of my senses, but I have to assume there is a temporal dimension and grant it size by measuring something else. Nor should we allow intuition, common sense, and it feels right to guide us in matters of basic reality as they have all proved untrustworthy further back along the chain of existence.

Positing that time is responsible for motion, besides begging the question, rather puts the cart before the horse - we use motion or displacement (in our clocks) to determine time taken not vice versa. Also smacks of conjuring up supernatural forces to explain effects. You say while seated that time passes because stuff happens. But you see different stuff because you are in a different place, by thousands of miles if not more, no matter how tightly glued you are to the chair - the only measurement you can make relating to time is that of the distance you have moved.

As for stating that we move in only one direction through time this is as meaningful to me as someone affirming the presence of the Holy Trinity - there is no witness to either of these scenarios so where did the numbers come from? Perhaps there are three directions in time and only a Holy Unity! Or, more likely, a zero for both.


Time is experience

I think of time as being experience, so if you're not experiencing, time is absent.


Time is a matter of scale. The laws and relationship between The micro and the macro that gives definition to quantum gravity is scale. The laws of physics are dependant on
scale. Time varies depending on the scale of the perspective.
The Old Man



what time really is

Paradoxically, time is as real as our very lives yet it is an illusion dat doesn't even exist without us.Time is therefore a stubornly persistent illusion perceived only in our conscious mind. The fact that you can't measure the present moment because it has no duration further attests to the fact that time is just an illusion.

What is Time?

In a couple of short essays available online at http://www.spacetime.nu I argue that time is actually a discontinuous manifestation of elastic oscillations of the fabric of the universe.
The Big Bang would presumably be the event that induced the oscillations.
This also reconciles Newtons absolute time with the relativity of Einstein as well as with simultaneity, which at the end of the day leads up to a possible explanation of timedilation.

What is Time

Children may understand time better than adults. Raised in a world with DVDs and videos a child is keenly aware of fast forwarding slowing and reversing a video. When time slows motion slows and faster motion is seen with faster time. Time at least superficially seems to be linked to motion. However a simple thought experiment can provide further insight. Imagine a satellite orbiting a larger mass. Imagine time slowing down for this system. We expect to see that the orbital motion will be slower. However for that to happen the force keeping the two objects together in orbit will also have to get weaker. Similiarly if we imagine a faster time we will expect a faster motion and the attractive force between the two masses will have to be stronger. So time involves both motion and forces. For further info on this line of thinking visit timephysics.com

Previous post - re Time as an Illusion - small amendment

I meant "..our own mortality" not IMmortality!! Woops

Kind regards
Simon Morley

(also, couldn't figure out how not to post anonymously, so sorry again!)

Time is 1. an abstract, 2. a collective term and 3. an illusion

The chasing for shadows that gets called the understanding of time is looking too hard, in the wrong place. It's a semantics issue (not physics, not math, and not cosmology)

1. An Abstract. Time is change. Change is caused by energy differential. It is independent of time. Change happens anyway. Time doesn't cause change! Time measures and calibrates change - so "time" is a derived abstract (i.e a measurement and calibration system)

2. A collective term. Every particle in the universe has its own change history/future. Its own, independent and unique change stream. Time can't be a "frame by frame" universal (using the movie picture analogy) as all quantum particles operate independently. Time is NOT an absolute, nor universal. BUT we use the word time as the collective term for all the change streams. Every quantum particle changes in its own stream. This might be in a "frame by frame" manner- but the universe of frames are not linked, not synchronised. There is no universal single frame of time. Time is the aggregation of all change, all change stream or all frames (depending on your preferred analogy). Time is a collective term for all change.
3. An Illusion. The earth rotation governs our lives. And our bodies change continually as we age. These two ubiquitous, constant change streams (day and night, and our own immortality) have caused the notion of time being a "thing" (a flow, a stream, a dimension or whatever) to be deeply engrained in our phsyche. Its an illusion!

No change means no time. Its as simple as that!
For a fuller explanation, please see www.thisistime.co.uk

A Brief History of Timelessness.

Very interesting articles,

I have thought a great deal about this subject, and it seems to me that rather than ask 'does time exist' or 'what is time' (which are loaded questions) - we should perhaps first ask ...
'what do we basically observe?' - and then see if the need or existence of an extra, and apparently mysterious thing e.g. time arises.

in my experience we basically observe matter and motion - and if wee look at this in great detail we can see that just matter existing moving changing and interacting 'now' so to speak can account for all that we observe and attribute to 'time'.

if you look at Einstein's 'relativity' you can see that he 'assumes' that (extra to matter and motion) time exists in at least some way, but without proving this. He then goes on to word his revelations in terms of 'time' ( time being dilated etc).

whereas i think it can be shown that everything he says can be seen as correct, but also just happening 'now' (with no existence of 'time' suggested or implied). -

Anyone can just casually say something like this, and such comments are ten a penny unless carefully backed up, so I wrote a book draft, set up a page, and made a few videos about it.

see 'A Brief History of Timelessness'

(one of the videos - http://www.youtube.com/watch?v=DpT9l7ZPmtw)

Matt Welcome, London


It is my admittedly simplistic understanding that the need or existence of time (in addition to matter and motion) has already been acknowledged. It is used in many equations. It is how we calculate speed, velocity, acceleration, and on and on. How can we explain what we observe in motion that is attributed to speed without the concept of time?

Thanks for this post. Time

Thanks for this post. Time as an emergent phenomenon...now I have something to think about...for the next several years! Well, at least I have plenty of time...