"Time" looks like not to exist without space. In fact, it is space-time that exists? In this case time dilation may be correlated to space changes too.

Interesting question Parviz

Time is a non observable, hence hard to define precisely (all attempts at defining time end up being circular or partly circular definitions, which is the fundamental reason why it's a non observable).

Any definition would also depend upon the reference frame under consideration, for instance, Time in a 5-dimensional Universe would be very different from time in a 3D universe, etc.

Further, beyond what you quote here, there is the apparent weirdness of time: delayed choice experiments, for instance - where it seems that the weirdness does not arise from time itself but from something deeper, which comes out or expresses itself in odd timelike phenomena.

So I would think that the short answer to your question is : no. To define time you must sort out a whole host of other things first - such as , the granularity of spacetime, dimensionality, etc.

PS - answering your further comment - Time may actually exist without space at least under certain theories. In Loop Quantum Gravity, for instance - Martin Bojowald has convincingly shown that the prior existence of Time would be a necessary condition for a Big Bang to be able to happen.

Dear H Chris

Thank you for your comments.

1) Time may be dicrete however as short as time difference measured by Cs-atomic clock, Time resembles to be continuous. Natural events as short as 1 ps -100 fts, may be measured by the accurate clocks based on mode-locked laser pulses with 10 fts duration.Time is still continous.

2) In synchrotron accelerators, elecron speed may approach to c where it experiences significant time dilation. However no sensible physical change happens for electrons.

Your advice is appreciated.

Your question about time is fundamental, and unsolved. Personally I understand time like Aristotle. A friend of mine pointed me to his thoughts. There is movement and things spatially move or get moved. But there is no time what goes on! Time and space are constructions made of people and used by people. It helps to calculate and give orientation. But I think it is only a construction, not more. We better don't put time in the first place and movement in the second. If we do it leads us to all kind of thoughts what else this (invented) time-construction would be. We need to keep in mind that all there is, is movement. Why I think so? Well, take a seat, settle down, take a few moments and look around. What is there to notice a difference between moments?

Having this done it is obvious why we introduced the construction of time. And it is obvious why this construction of time works great for calculations and why Newton and Einstein and so on take this as common ground for their knowledge. And it is right to do so. We better just don't confuse the reality of movement and constructed time so we don't lose the red line.

Time is flowing even one stays still and immobile and his biological clock runs to get older. Time is flowing because the solar system clock exhibits the rotation of successive days and nights and the sun consumes its hydrogen fuel. On the other hand , time dilation occurs in fast velocities close to light velocities according to special relativity theory and time dilation may take place around space-time curvature due to GTR.

Here, I have summarized my comments posted in another Q&A ( " Is time flow an illusion?" ) :

Time flow is right because we feel time individually and we are getting old and no return to our young period is possible. We undergo time all over our life. It is an unidirectional arrow to forward direction : Future. A natural clock in solar system indicates the elapse of time based on the translation and rotation of earth and moon around sun.

Can you reverse the rotation from CCV to clockwise ? why is it counterclockwise?

Time exists even there is no motion, and we get old due to our biological clock even we stand stationary.

On the other hand, Galilean and Lorentzian transformations are correlated to absolute Newton and relative Einstein concepts of "Time". Each one may be correct at certain conditions.

Furthermore, in atomic and molecular levels, the uncertainty principle may be helpful to assess the time scale.

Uncertainty in a typical atomic transition:

Delta E * Delta T ~ h/2 pi

Delta W * state lifetime ~ 1

lifetime ~ 1/A , A is the Einstein coefficient for spontaneous emission.

Uncertainty supports to estimate a sensible time parameter.

Exactly, it is written for populated levels and not for a single atom:

dN / dt = -AN, where N is the instantaneous population of the state.

I intended to show the significance of time in quantum theory of emission, where the energy spread of an exited level is related to the inverse of level lifetime. In fact, for a broadened level of atom, the lifetime decreases, namely the populated level is deactivated faster than a narrow state. Since A=Delta W and the spontaneous emission rate correlates inversely to lifetime. Alternatively, a forbidden level is characterized with a very narrow exited state or very small A.

The uncertainty principle may be helpful to estimate the characteristic time in the optical resonators:

Delta E * Delta T ~ h/2 pi

Delta W ( mode) * photon lifetime ~ 1

Hint: axial modes are generated in the cavity.

Photon lifetime in cavity =Tp = (c/2nd)/1-R1R2 and R1,R2 are reflectance coefficients.

The frequency spread of the axial mode generated in the resonator is correlated to the inverse of the photon lifetime. Longer Tp shows narrower band of the modes and represents a selective sharper frequency width.

Again,

Uncertainty supports to estimate another sensible time parameter: Photon Lifetime in the resonator.

I conclude that universe is a dynamic complex system. It contains subatomic sizes in distinct fm/pm/nm scales, up to the solar light measure for far distances, all deal with " motions" in different scales. Motion in subatomic scale is known as atomic transitions and correlated photons.

On the other hand, an excited atom may function as a precise clock due to its reproducible level lifetime. Time resembles to be continuous as short as femtosecond intervals where our most accurate clocks can measure.No time quanta was detected in universe. The Einstein A coefficient explains the lifetime of atomic states as a reproducible time scale for the "atomic clock" : the most prcise and reliable instrument for time measurement available. The uncertainty principle in the optical resonator gives us another time scale for temporal measurement based on Fabry- Prot cavities. The femtosecond pulses generated in the mode locked Ti: Sa lasers may be the shortest sensible time scale that is reproducible, to my knowledge.

- Time is a measure of sequence to discriminate events without that all events occur simultaneously in space time.

- It is believed that a great number of events take place at any moment and this picture never happen again(physically) and therefore it is irreversible.

- The physical events including electronic excitations, vibrational and rotational modes of molecules are quantized while translational motion of particles in space-time exhibits a continuity that can be determined by time of flight measurements (TOF). Hence time is not discrete and resembles to be an unidirectional flow.

-The evidence of a physical fact is accredited by the measurements, To my knowledge, the shortest time duration is generated by femtosecond lasers and it is the minimum sensible time duration that can be measured presently.

-

1-Time is sensible using our biological clock =>a meaurable quantity.

2- Time is measured as accurate as 6 femtosecond using optics=>a real value.

3- Time is a physical dimension=> an indication of sequence of events.

4- If there is no time sequence, then all events in past, present and future happen simultaneously.

In time of flight (TOF) experiments using a fs laser and mass spectrometer, laser pulse causes coulomb explosion of the target molecules such that molecule disintegrates into several charged fragments. Then a short time interval is measured to determine the arrival of each fragment at a MCP to correlate the m/q ratio with TOF. MCP stands for multi channel plate at which a uniform electric field is applied to accelerate the fragments. For instance, the measurable fragments of CO2 are sorted after coulomb explosion in the following order: C+, O+, CO+, O2+ , C2+ and CO2++ and CO2+. This accredits the application of TOF in material identification.

Range finder is another example to attribute the TOF ( of a laser shot) with the round -trip distance covered by those photons . It indicates the use of TOF in distance assessment.

These instruments attests the measurable short intervals can reveal other physical properties.

About the existence of time; cit of A World Without Time: The Forgotten Legacy of Gödel and Einstein, by Palle Yourgrau, year 2006

"... By 1949, Godel had produced a remarkable proof: In any universe described by the Theory of Relativity, time cannot exist. Einstein endorsed this result-reluctantly, since it decisively overthrew the classical world-view to which he was committed. But he could find no way to refute it, and in the half-century since then, neither has anyone else. Even more remarkable than this stunning discovery, however, was what happened afterward: nothing. Cosmologists and philosophers alike have proceeded with their work as if Godel's proof never existed-one of the greatest scandals of modern intellectual history. A World without Time is a sweeping, ambitious book, and yet poignant and intimate. ..."

Time exists and TOR is imperfect.

If there is no time then no sequence and you are eternal.

I agree the likelihood of another universe without time, however this univiverse certainly deals with time.

Dear Parviz.

If my work is correct and I now have a great degree of certainty that this. Because all converted physical to only 4 numeric values ​​and derivatives space. Well to answer this question with a great degree of certainty.

Actually all my work began to understand what was the time!

To start we have to divide time into two concepts:

One is that human time and only have local significance.

And emerges from quantum memory is in the brain. People store a table of memory every 125ms, so hesitate television because if the brain was not quantum would not be possible to elude him with 15 frames per second that you are starting to realize as an image of continuity.

In this view the past and made the correlation memories in our brain and the future created by the projection of this information at an event to occur. If you are observing the loss of memory brings the total lack of time as the alzheimer.

And another time has come the time arrow, which originates in the constant-acceleration of the universe. What is understood as a constant-entropy increase of the universe.

Within this time the anti-matter and a negative time, according to the interpretation of Paul Dirac.

Concept that the current physics does not understand the meaning.

And that within the work I've done shows that it is the sense that moves the universe. In this study the universe and made of a stacking Branes. and on each side of this brane universe moves in contrary directions and rotates on the edge of mobius. Ie we have a universe of anti-matter at a distance of approximately 1x10-16 meters of each other, separated by branes.

These branes are built of strings.

And as a final concept time is the transfer of information between two points in space. since everything we think is true, is nothing more than a mental model created in the human brain. And that is inserted into a large quantum computer. What is the difference between a dream and reality? this goes to show that reality is not all its cracked up to be!

Do you mean that higher string dimensions can squeeze to four dimensions coming to reality where the current Physics laws hold. Then space and time are properties arise from the strings. Interesting but should be proved?!

Dear Parviz .

Einstein was a theoretical , and always tried to prove his theories are the mathematical point of view. up with some results when electrons were conflicting with relativity , early in his theory . He was credited with .

I also believe in what I do , then I have much She has worked in practical projects . Mainly in the area of electronics , telecommunications and computing . From the mathematical point of view I have no doubt that this is entirely correct . On the dimensions of what I call zero-dimensional due to the fact that the velocity of propagation of longitudinal waves of the universe and very large . Become all one universe. and where it is clearly observed in this and quantum entanglement of particles . The model indicates for example that if you can not measure gravitons with current technology , although they exist . because their speed and the same quantum entanglement . maybe if you think of a puddle test using gravity and quantum entangled particles . but as the orders of magnitudes of the forces are very different it would be very difficult to have sensitivity and dynamic range for such experience . By this I have dedicated myself to the gravity control that connected with other concepts found in the universe . You must agree that it is very complex, in a few lines describing a theory that has the pretense of explaining all the processes of the universe . For now I have sought people to discuss the overall vision and I am very pleased to have someone with his level of knowledge open to new visions of physics !

No time travel is physically real because:

1- Flow of time.

2- Time arrow is unidirectional.

3- Spacetime: changing the time direction will affect the space too.

4- No time traveller from the future or from the past was reported.

5- At least, our universe is based on causality principle and no violation was reported since the big bang.

6- Any conjecture is possible in other universes or multiple dimensions, not in our universe.

However, time is relative and time dilation is a physical fact, along its unidirectional arrow.

Dear Parviz .

Time travel can not break causality .

But can reverse the paradox of Einstein twins .

In order to travel to distant points in space and feasible from the standpoint of human longevity .

It is possible to take a trip away at high speed and back much younger than the brother who stayed on earth . and this evidence with atomic clocks are incontestable . but it is also possible to make the same trip and come back with the brother of the same age ie this point we are talking about a long-distance trip in a tiny earthly time . which in practice serie understood as a machine capable of returning to the past . but no broken causality and therefore not possible to arrive before leaving ! Bake ta time and real mirror but she and in a parallel universe and precisely this inversion that creates a sense of antimatter . what Paul Dirac had already noticed in their relativistic matrix calculations that predicted the existence of antimatter . ie antimatter , and the same subject , with an arrow of time , the inverse of this universe .

Dear Jorge

Time is difficult to understand and the gravity is much more difficult to find out its mysteries !!

Dear Jorge

I respect your comment, however If someone travels back to the past and then kills his father , then causality is violated and he never exists, This is a paradox benefits no time travel is feasible. Being or not being, this is a dilema where the casuality fails.

I do not know the physical laws in another universe but I may know some fundamental rules in our universe where there is no absolute quantity and all parameters are relative. Atomic time scale is innate and we do not have any access to change it because the lifetime of a certain atomic state always invariant and repeatable, therefore it is a fact. I mean time duration is a fact which arises from enegy width. On the other hand, time and energy are correlated together. We can measure the energy flow, consequently the time flow may exist.

 Parviz:

With all due respect, you're simply repeating garbage about time travel from stories which have no scientific relevance or value. Most physicists do this, but still, it has no place in a discussion about time travel beyond yapping about all the erroneous material that's already out there...

There is time dilation and it is not absolute. Time difference varies with velocity and energy, therefore it is not really an independent variable particularly in relativistic velocities. Time may slow down or accelerate due to the relative location of the observer close to strong gravity field of sun or near black hole or in the interaction of the relativistic objects.

There is time dilation and it is not absolute. Time difference varies with velocity and energy, therefore it is not really an independent variable particularly in relativistic velocities. Time may slow down or accelerate due to the relative location of the observer close to strong gravity field of sun or near black hole or in the interaction of the relativistic objects.

Parviz:

That's all essentially accurate. However, what's really happening is that the effects of our moving through time are altered by strong gravity fields or relativistic velocities. That's why we can have those effects without there being a flow of time. That's my original opinion based on my published research...

Time is correlated to the  sequence and  the causal effect. Without Time, the causal effect disappears and there is no sequence for the occurrence of events, then all events simultaneously take place.

Actually, the causal effects are correlated to (or in) time. WIthout time, nothing would happen as all as time is a dimension and dimensions allow for various degrees of freedom. I the case of time, time allows for events to happen.

Hello Parviz,

My work involves developing methodology for discipline-spanning transdisciplinary understanding that enhances communication between the disciplines. To develop the methodology it is necessary to examine and compare the real-world subject matters of the various disciplines.

While using transdisciplinary methods to develop an understanding of the intrinsic nature of space, I unexpectedly came upon the basis of time in the universe.

In the universe, the form of change that is the continuing-existence of space plays all the roles that can be realistically attributed to time.

(This is the continuing-existence of space as measured by a clock, not the extension of three-dimensional space as measured by a ruler.)

Understanding how spatial-continuing-existence plays the roles of time provides the answers to the questions: What is time?, Why does time occur?, and Why does time have the specific qualities that it has?

There is a paper on ResearchGate.net and Academia.edu. titled, The Identification of the Intrinsic Nature of Time, that provides the understanding of how spatial-continuing-existence plays the roles of time.

I hope that understanding the intrinsic nature of time will be useful to you.

Regards,

Vincent Vesterby

Vesterby, Vincent. 2014. The Identification of the Intrinsic Nature of Time.

https://www.researchgate.net/publication/299437469_The_Identification_of_the_Intrinsic_Nature_of_Time

Vesterby, Vincent. 2014. The Identification of the Intrinsic Nature of Time.

https://www.academia.edu/21710898/The_Identification_of_the_Intrinsic_Nature_of_Time

Research The Identification of the Intrinsic Nature of Time