Thread: What is time?

Hello Friends:

I just got done reading (and trying to understand) an article in the April 2012 issue of Scientific American entitled Quantum Gravity in Flatland. On page 44 the author Steven Carlip says:

Time is fundamental to our observed reality. almost every theory of physics is ultimately a description of the way some piece of the universe changes in time. So we physicists had better know what "time" means, and the embarrassing truth is we do not.

Carlip doesn't leave us clueless, though, and on page 46 he tells us that Einstein said that time is what is measured by a clock.

My own intuitive and perhaps unscientific understanding of time is that it is simply change in a particular place or that times (plural) is the phenomenon of change in the universe as a whole. If we assume that Einstein's Special Theory of Relativity is correct, then there is no absolute time, and time in one place might be different (slower or faster) than in another place. So a clock will run faster on earth than on a probe speeding away from it. As a result, I think that it may be improper to speak of time in the singular sense unless we are referring to the time in a specific location. There is no single clock that can accurately measure the time in the entire cosmos, and in this sense we should speak of times (plural) rather than time. If we could stop all change in the entire universe, then there would be no times and hence no time in any location.

Anyway, how wrong am I?

Jagella

Certainly if nothing ever changed, then your watch wouldn't change, so at least you'd be meeting Einstein's definition of time standing still.

Some would argue that there is no time and only cause and effect.

Time is that which stops everything from happening at once.

Originally Posted by kojax

Certainly if nothing ever changed, then your watch wouldn't change, so at least you'd be meeting Einstein's definition of time standing still.

True, but another way to look at time is that if there is no change then time could be measured as zero. Time then might still exist at least potentially. It might be analogous to speed. An object standing still has zero speed, but speed still exists.

Jagella

Originally Posted by jetstove

Some would argue that there is no time and only cause and effect.

Can you elaborate? I think of cause and effect occurring in time. If there is no time, then there can be no causality. It's one of the reasons why the universe could not have been caused. If there was no universe, then there was no time and no cause for it.

Jagella

Originally Posted by SpeedFreek

Time is that which stops everything from happening at once.

What do you mean by "everything," and why can't everything happen at once?

Jagella

I'm not a physicist nor a philosopher, but I believe we shouldn't take a philosophical approach to this, which will only lead to argument and unscientific regression.

We have to look at it objectively, so that way we can understand it scientifically instead of doing what philosophers have been doing throughout the ages ... calling time whatever they wish as long as it makes relative sense just because.

For example, from a geometric point of view, time seems to behave linearly. The current "time" can be described on a number line with a forward/positive (future), concurrent/neutral (present), and backward/negative (past) partition. It's like location in a temporal respect. Just as you would describe location in one-dimensional space.

I often think that sciencetists takes the concept of time to hysterical heights, and make elaborate nonsens. Time is indeed a very strange concept as it is kinda 3D with relative values, but I don't think it's no different than the ocean waves would distort old fashion pendulum-ship clocks.

Time is just a way of messure things, which one must carefully take account for observer and movement, nothing more to it than that.

Originally Posted by HexHammer

I often think that sciencetists takes the concept of time to hysterical heights, and make elaborate nonsens. Time is indeed a very strange concept as it is kinda 3D with relative values, but I don't think it's no different than the ocean waves would distort old fashion pendulum-ship clocks.

Time is just a way of messure things, which one must carefully take account for observer and movement, nothing more to it than that.

Measurement is dependent upon the system which it uses. If my ruler is 12 inches long, it is described within space. You could think of space as a measurement in the way we utilize it, but what is space itself? The same goes with time. We can measure the world with it, but what is time itself?

Originally Posted by Jagella

Originally Posted by SpeedFreek

Time is that which stops everything from happening at once.

What do you mean by "everything," and why can't everything happen at once?

Jagella

Everything = all events in the universe.

I didn't say that everything cannot happen at once, I said it was time that stops everything from happening at once.

Originally Posted by brody

...from a geometric point of view, time seems to behave linearly. The current "time" can be described on a number line with a forward/positive (future), concurrent/neutral (present), and backward/negative (past) partition. It's like location in a temporal respect. Just as you would describe location in one-dimensional space.

Yes, time seems to progress in a straight line like an arrow. It has direction moving from the past, to the present, and on to the future. As far as I know we cannot move back to the past which demonstrates that time is one-directional. Some cultures believe time is circular which means that we always go back to the past and that it recurs forever.

Looking at different viewpoints can be helpful.

Jagella

Originally Posted by Jagella

Originally Posted by kojax

Certainly if nothing ever changed, then your watch wouldn't change, so at least you'd be meeting Einstein's definition of time standing still.

True, but another way to look at time is that if there is no change then time could be measured as zero. Time then might still exist at least potentially. It might be analogous to speed. An object standing still has zero speed, but speed still exists.

Jagella

Whoever takes the measurement would have to have an advancing clock then. All measurements have to be taken against something. If the measurer's clock is not advancing as well, then the lack of movement everywhere else would be unperceiveable to them.

Originally Posted by HexHammer

Time is just a way of messure things, which one must carefully take account for observer and movement, nothing more to it than that.

So is distance, including the part about observers and movement.

Originally Posted by kojax

So is distance, including the part about observers and movement.

Explain please, how is "distance", "relative" ?

Originally Posted by HexHammer

Originally Posted by kojax

So is distance, including the part about observers and movement.

Explain please, how is "distance", "relative" ?

Because it depends on the relative state of motion of the observer. For example, if you were wanting to walk from the earth to the moon, the distance would appear to be (roughly) about 1 light second or thereabouts. However, if you are moving towards the moon at close to the speed of light, the distance would appear to you to be much shorter, because of length contraction effects. That is why distance measurements are relative, just like time measurements are.

Originally Posted by brody

Originally Posted by HexHammer

I often think that sciencetists takes the concept of time to hysterical heights, and make elaborate nonsens. Time is indeed a very strange concept as it is kinda 3D with relative values, but I don't think it's no different than the ocean waves would distort old fashion pendulum-ship clocks.

Time is just a way of messure things, which one must carefully take account for observer and movement, nothing more to it than that.

Measurement is dependent upon the system which it uses. If my ruler is 12 inches long, it is described within space. You could think of space as a measurement in the way we utilize it, but what is space itself? The same goes with time. We can measure the world with it, but what is time itself?

I'm not sure what you are saying is scientific at all, maybe it's just me, but..

Originally Posted by Markus Hanke

Originally Posted by HexHammer

Originally Posted by kojax

So is distance, including the part about observers and movement.

Explain please, how is "distance", "relative" ?

Because it depends on the relative state of motion of the observer. For example, if you were wanting to walk from the earth to the moon, the distance would appear to be (roughly) about 1 light second or thereabouts. However, if you are moving towards the moon at close to the speed of light, the distance would appear to you to be much shorter, because of length contraction effects. That is why distance measurements are relative, just like time measurements are.

Very well, it's a new concept to me, which I've never heard about.

Originally Posted by HexHammer

Very well, it's a new concept to me, which I've never heard about.

The effect is called "length contraction", and is intimately related to "time dilation". If you search for these on Wikipedia you will get some good general information.

Originally Posted by Markus Hanke

Originally Posted by HexHammer

Very well, it's a new concept to me, which I've never heard about.

The effect is called "length contraction", and is intimately related to "time dilation". If you search for these on Wikipedia you will get some good general information.

Thanks for heads up.

This "length contraction" gets me to think of Quantum Entanglement, that a new concept different from digital and analogue is the 3rd "rope" to transmit information, where "pulling" the "rope" should affect the other end immediately.

Originally Posted by HexHammer

that a new concept different from digital and analogue is the 3rd "rope" to transmit information, where "pulling" the "rope" should affect the other end immediately.

Actually, no transmitting of information takes place in such a quantum entanglement scenario. What happens is that two ( or more ) particles have interacted some time in the past, creating a state of entanglement. If we then perform a measurement on just one of these particles, we automatically know what the state of the other particle is, no matter how far away it may be. This is because both particles have been in their complementing states all along since their first interaction, it's just that we didn't know what those states are until we perform a measurement on one of them. Because their states are correlated to each other, just one measurement tells us what both states must be. It is really just a result of quantum mechanical statistics, and no exchange of information over distance is required. If you so wish you could say that during their first interaction both particles became part of just one system.

Originally Posted by Markus Hanke

Actually, no transmitting of information takes place in such a quantum entanglement scenario. What happens is that two ( or more ) particles have interacted some time in the past, creating a state of entanglement. If we then perform a measurement on just one of these particles, we automatically know what the state of the other particle is, no matter how far away it may be. This is because both particles have been in their complementing states all along since their first interaction, it's just that we didn't know what those states are until we perform a measurement on one of them. Because their states are correlated to each other, just one measurement tells us what both states must be. It is really just a result of quantum mechanical statistics, and no exchange of information over distance is required. If you so wish you could say that during their first interaction both particles became part of just one system.

I'm not sure I can agree with how you display it.

"As with Einstein, Schrödinger was dissatisfied with the concept of entanglement, because it seemed to violate the speed limit on the transmission of information" Quantum entanglement - Wikipedia, the free encyclopedia

Originally Posted by HexHammer

I'm not sure I can agree with how you display it.

"As with Einstein, Schrödinger was dissatisfied with the concept of entanglement, because it seemed to violate the speed limit on the transmission of information" Quantum entanglement - Wikipedia, the free encyclopedia

I appreciate your doubts on this matter, and many a scientist will share them. The truth of the matter is that the explanation of how exactly quantum entanglement works depends on the interpretation of the basic tenants of the quantum mechanics, specifically non-locality and hidden variables. There are several such interpretations, and we don't really know which one, if any, is the correct one.
My point is simply that because, as you have rightly pointed out, the instantaneous exchange of information over large distances violates basic premises of physics, I find it highly unlikely that such an exchange actually takes place. I believe that entanglement can be explained purely by statistical correlations between the various parts of the entangled system; remember, we perform a measurement only after entanglement takes place, which means we have no knowledge of the system between the time of entanglement and the time of measurement, except in terms of superpositions of probability amplitudes. In my opinion the complementing states of the system do not come about as a consequence of instantaneous information exchange, but simply because this is the state we find it in when we measure it ! The state was present all along as one possible "path" the system could have taken, it is not created at the time of measurement, therefore no information needs to be exchanged. The correlations between the parts of the system have been there already since the time of first entanglement.
Not sure if I am making any sense...?

I might be completely wrong here, but this is my way of understanding quantum entanglement.

@Markus Hanke

But that sounds more like philosophy to me, when you contradict simple facts. This is a science forum after all.

Originally Posted by Markus Hanke

Originally Posted by HexHammer

I'm not sure I can agree with how you display it. "As with Einstein, Schrödinger was dissatisfied with the concept of entanglement, because it seemed to violate the speed limit on the transmission of information" Quantum entanglement - Wikipedia, the free encyclopedia

I appreciate your doubts on this matter, and many a scientist will share them. The truth of the matter is that the explanation of how exactly quantum entanglement works depends on the interpretation of the basic tenants of the quantum mechanics, specifically non-locality and hidden variables. There are several such interpretations, and we don't really know which one, if any, is the correct one.My point is simply that because, as you have rightly pointed out, the instantaneous exchange of information over large distances violates basic premises of physics, I find it highly unlikely that such an exchange actually takes place. I believe that entanglement can be explained purely by statistical correlations between the various parts of the entangled system; remember, we perform a measurement only after entanglement takes place, which means we have no knowledge of the system between the time of entanglement and the time of measurement, except in terms of superpositions of probability amplitudes. In my opinion the complementing states of the system do not come about as a consequence of instantaneous information exchange, but simply because this is the state we find it in when we measure it ! The state was present all along as one possible "path" the system could have taken, it is not created at the time of measurement, therefore no information needs to be exchanged. The correlations between the parts of the system have been there already since the time of first entanglement.Not sure if I am making any sense...?I might be completely wrong here, but this is my way of understanding quantum entanglement.

I think you put it very clearly but when you say that no information is interchanged then how does the particle that has not been measured collapses when the other one has been measured? Surely it must have been some interaction between them?

Originally Posted by HexHammer

Originally Posted by brody

Originally Posted by HexHammer

I often think that sciencetists takes the concept of time to hysterical heights, and make elaborate nonsens. Time is indeed a very strange concept as it is kinda 3D with relative values, but I don't think it's no different than the ocean waves would distort old fashion pendulum-ship clocks.

Time is just a way of messure things, which one must carefully take account for observer and movement, nothing more to it than that.

Measurement is dependent upon the system which it uses. If my ruler is 12 inches long, it is described within space. You could think of space as a measurement in the way we utilize it, but what is space itself? The same goes with time. We can measure the world with it, but what is time itself?

I'm not sure what you are saying is scientific at all, maybe it's just me, but..

Are you trying to say something? Anyway, "Time measures things" does not explain what time itself is. That's what I'm trying to say. Yes, time can measure events, e.g. the conference was 2 hours long. That is a useful property, but not a definition.

Originally Posted by Veck

I think you put it very clearly but when you say that no information is interchanged then how does the particle that has not been measured collapses when the other one has been measured? Surely it must have been some interaction between them?

The interaction took place at the time of entanglement, not at the time of measurement. When entanglement takes place the particles cease to be separate entities, and become just one system. The measurement collapses one wave function which describes both particles. This wave function is backwards correlated ( in a statistical sense ) to the time of first entanglement, so no interaction between far away particles is required during measurement.

Originally Posted by HexHammer

@Markus Hanke

But that sounds more like philosophy to me, when you contradict simple facts. This is a science forum after all.

Which facts are you referring to ? I have given an interpretation of quantum entanglement is terms of statistical correlations and probability amplitudes. I don't need any action over distance, or hidden variables, to explain this phenomenon. How is this not scientific ?

Originally Posted by HexHammer

I'm not sure I can agree with how you display it.

"As with Einstein, Schrödinger was dissatisfied with the concept of entanglement, because it seemed to violate the speed limit on the transmission of information" Quantum entanglement - Wikipedia, the free encyclopedia

I think you have put the emphasis in the wrong place in that quote: "As with Einstein, Schrödinger was dissatisfied with the concept of entanglement, because it seemed to violate the speed limit on the transmission of information"

Note that they are talking about people's perceptions and that it is in the past tense; i.e. when the phenomenon was not as well understood as it is now.

Because this is my first reply on this forum, I will inform the reader that relative to physics I am self educated extending over 68 years. My endeavour has always been an attempt to understand the fundamental realities, and has culminated in a 168 page book.

In answer to Jagella I will provide the following concepts. With regards to the fundamental dynamic nature of TIME, then it is my belief that at that physical level, the ability to move constitutes the basic reality which allows the human invented concept Time when an oscillating motion is established. As to the fundamental nature of what is supporting such motion requires an explanation of the original creation. Therefore TIME exists in the universe because we insist on making measurements, and for a reasonably accurate (not a guess) assessment, always by the use of regulated quantities of motion. Excluding intelligent life, then relative to the universe there is no such phenomenon as Time; only constant change, the duration of which can be as short as one quantum of extremely short wavelength of oscillating motion.

When we attempt to define the fundamental nature of TIME, we become confused because we think in the values to which we are accustomed. We are referring to concepts of past memories and anticipating the continuance of a future. Our here and now is provided by constant conceptual sensory snapshots of our local reality. Relative to humans, the here and now instant of our life, instant by instant becomes the past by constantly being replaced be a procession of constantly arriving future instants.The way I view the reality of one instant of time relative to human existence, relates to one oscillation of an electron. The above is the base on which the content regarding the fundamental dynamic nature of matter is explained in the referred to book.

Originally Posted by Strange

I think you have put the emphasis in the wrong place in that quote: "As with Einstein, Schrödinger was dissatisfied with the concept of entanglement, because it seemed to violate the speed limit on the transmission of information"

I cannot convince myself this a material difference, but whatever

Note that they are talking about people's perceptions .

Again, it not clear what you mean. Maybe this will help (unlikely!).

In the mid 1930's, Einstein wrote a paper with Boris Podolsky and Nathan Rosen, famously known as the EPR paradox.

In it, they insisted there is such a thing as "objective reality" which they define as follows: If without any disturbance (i.e not measuring) of a system we can predict with probability = 1 the value of a physical quantity, then there exists an element of "physical reality" that corresponds to this physical quantity.

To which Bohr's response was: any system consists of physical objects together with all possible means of measuring the corresponding quantity.

Note this is reminiscent of the "tree falling in a forest" debate in philosophy.

Any, here is the EPR argument:

Consider 2 particles with momentum and position variables and to be in a state with quite definite momentum , say and definite relative separation . This is possible since that is they commute.

Now allow our 2 particles to interact, and at some later time measure for partcle 1. Then one immediately knows without measuring ("disturbing") particle 2 what is . Therefore (by their definition of "objective reality") is objectively real.

Do the same for , and find the same - is also objectively real

But then as momentum and position operators respectively, quantum theory asserts that , so a contradiction is claimed - if and are objectively real, then why are not their commutator?

As always with contradictions, it is useful to look to the starting assumption.

Bohr 1, Einstein 0

I find a rather sad irony in all this. But it is late - ask me why I think so on another day

Originally Posted by Guitarist

Originally Posted by Strange

I think you have put the emphasis in the wrong place in that quote: "As with Einstein, Schrödinger was dissatisfied with the concept of entanglement, because it seemed to violate the speed limit on the transmission of information"

I cannot convince myself this a material difference, but whatever

It was just that HexHammer appeared to trying to use that quote to show that faster than light transmission of information is possible. But the important point is that, naively, it might look as if it involves faster than light communication; but it doesn't. (As I think your description shows; it is just about the correlations of measurements).

Jagella,

......If we could stop all change in the entire universe, then there would be no times and hence no time in any location.
Anyway, how wrong am I?

I think Einstein's simple statement that "time is something clocks measure," is simple yet profound. Einstein also said "When forced to summarize the general theory of relativity in one sentence: "Time and space and gravitation have no separate existence from matter."

This indicates that according to his theory(s), time is matter dependent.

I think that you have explained time correctly by your quote above.

Time can be simply defined by "change" and "motion" of matter. Without change time accordingly could not exist. Time could be defined as: An interval of change. Such changes might be quantitatively measured by a standard measuring device such as a clock, hour glass, sun dial, water clock, etc. It is a human concept that does not exist below human-like intelligence. Einstein also explained how time differs depending upon the relative motion of time frames, as well as a time frame's proximately to a center of gravity and its gravity's strength. A point within time, on the other hand, is a still photo of reality that does not involve time.

As you have indicated, there is no preferred reference frame for time, but we seemingly could someday have such a system as Earth mean-time (using Greenwich Meantime, for example), Milky Way meantime (taken from some "typical location" within the Milky Way), etc.

Time might be considered one of the simplest possible human concepts similar to the concept of the Cartesian dimensions of length, width, and depth. On the other hand many Quantum Physicists consider time to be a very complicated concept mathematically. It is thought by them to be such a complicated concept that an acceptable theory of it is not presently foreseeable because of contradictions between various factions of present day theory. This is explained in an entire book by Sean Carol "From Eternity to Here" the Quest for the ultimate theory of time.

Originally Posted by brody

Measurement is dependent upon the system which it uses. If my ruler is 12 inches long, it is described within space. You could think of space as a measurement in the way we utilize it, but what is space itself? The same goes with time. We can measure the world with it, but what is time itself?

I'm talking about nonsens such as "when big bang occured time began" which imo is nonsens.

Time is the measurement of mass moving from point A to B.

What if nothing is moving? Time still passes...

Originally Posted by andythomasthekey

Time is the measurement of mass moving from point A to B.

So photons don't count?

Hi all:
First of all, my apologizes if my English is not as correct as I'd like it to be.

As it is understood, or better said, agreed now, time is the way the "flow" of the Universe is interpreted by our brains.
From an objective point of view, it could be defined as the flow of the Universe. This "flow" could, at the same time, be explained as the change-evolution of everything. Hence, time exists, regardless there could be an observer or not.
It can be related to the "free energy" state of the Universe.
The subjective point of view, is related to the way, we have designed methods for measuring this flow and those changes by designing arbitrary frames.
Just at the moment a frame is linked to the observer, and space and time are linked to that frame, Relativistic effects take place.
Lets have a deep look to the way we try to measure time. Regardless a clock or a cesium atom could be taken as the suitable reference unit, all its being done, is only comparing a motion with another. "The car moves, for example, 10 times faster than the seconds hand of the clock". Time is not properly being measured, relations space-time, are compared, concluding that, time is not being measured, but only speeds.
Objectively speaking there is no separation between space and time, both things are different points of view of the same thing.
Lets imagine a rectangular metal plate that is being stretched from two opposite sides. At the sime time, the other sides, move as well. We could relate the way two sides go further from each other, with the way the other two are approaching. Thats what we do when measuring time and space. The fact is that there is a primary cause for the plate's distortion, and that the whole plate is distorted in such a way, that width and length are linked. There is no way for sepparating both dimenssions, the sepparation we did, and the relation found, is nothing else than an effect of the plate properties.
The same happens with time itself, and the way we measure it.

Best regards and thanks for reading me.

do photons move so fast/or slow so that we cannot detect them moving?

Originally Posted by andythomasthekey

do photons move so fast/or slow so that we cannot detect them moving?

We can measure the speed of light, which means detecting photons moving.

Originally Posted by Strange

I think you have put the emphasis in the wrong place in that quote: "As with Einstein, Schrödinger was dissatisfied with the concept of entanglement, because it seemed to violate the speed limit on the transmission of information"

Note that they are talking about people's perceptions and that it is in the past tense; i.e. when the phenomenon was not as well understood as it is now.

This is a valid statement. But as De Broglie pointed out quantum entanglement and the double slit experiment are very simple to understand in the presence of an aether. The problem with entanglement interpretation accordingly is simply based upon the Copenhagen interpretation in quantum mechanics which asserts that particles and photons have no particular state until they are observed. Many opposed this interpretation as exemplified by Schrodinger's cat.

As De Broglie explained, when two particles or photons are together in close proximity in the presence of physical waves (in an aether), they will take on complimentary states, such as opposite spin or the same polarization concerning photons. Send them off in opposite directions and of course like a gyro they will maintain this "complimentary" state unless they are interfered with. So in this interpretation quantum entanglement is a very simple process that is totally unrelated to communication. I would expect there will be a limit to the distance that this "entanglement" could remain since at least one particle of the two will eventually be interfered with in its course of travel, and accordingly the other will not change its state.

We have been proposing a particulate aether for the last 30 years or longer with such theoretical particles as gravitons, dark matter, Higg's particles, and many others. Whether any of these particles or others could relate to a luminiferous aether (a carrier of EM radiation) is another question.

As I mentioned in my last posting, I consider time to be one of the simplest concepts to understand. From this perspective there is not one thing in all of reality that could not be simply understood if it were properly explained . In this view, all of reality is complicated only in the possible quantity of its mechanics, such as a living organism, but not in its finest detail.

Clocks can not shows us the time. It show us just a time which we create. I think the real time , which we or I do not understand, exactly can not be measured by any invention yet. Time depends on anything or any different person. Time is not just a measuring the transportation between two points or something like that. Also time vary with places where you stay. Time is not just 't'. The time is the future or the past or now. May be it is the interaction of the atomic particles may be not.

May be like Einstein say time is what is measured by a clock.

Originally Posted by PhysicsEngineer

Clocks can not shows us the time.

Correct.
But not the way you seem to mean it:

It show us just a time which we create.

No, a clock doesn't show "time we created", it merely measures the passage of time. The way a ruler measures distance.

I think the real time , which we or I do not understand, exactly can not be measured by any invention yet.

What is "real time"?
I'd suggest we don't understand it and can't measure it because "real time" is an unexplained concept of your own devising.

Time depends on anything or any different person.

No.

Time is not just a measuring the transportation between two points or something like that.

No more than a "real metre" is the "actual" distance between two points.

Also time vary with places where you stay. Time is not just 't'. The time is the future or the past or now. May be it is the interaction of the atomic particles may be not.

What?

May be like Einstein say time is what is measured by a clock.

In other words: exactly what the rest of your post has said it's not...

Dear Dywyddyr
Ruler is not like clock. A one meter is 100 cm and one day is 24 hours due to around of earth sth like(what is 100cm). Now you said we dont create a time. Absolutely , it is not possible to create sth but I mean time which you see on the clock we create as a I said 24 hours is a one day. Likely we could say 2 day or half day is 24 hours. That is why I said we create. The point I try to say that If you or anyone wants to understand time, it is not good idea to think time is what measures clock.

I am really curios you said no about ' time depends on anyone or anytihng' . Please prove it...

Originally Posted by PhysicsEngineer

Ruler is not like clock. A one meter is 100 cm and one day is 24 hours due to around of earth sth like(what is 100cm).

In other words: they measure intervals. One temporal, the other spacial.
Or, to put it another way: a clock is like a ruler.

Absolutely , it is not possible to create sth but I mean time which you see on the clock we create as a I said 24 hours is a one day. Likely we could say 2 day or half day is 24 hours.

Like the way we say "We'll call this distance one metre"?

The point I try to say that If you or anyone wants to understand time, it is not good idea to think time is what measures clock.

Right. And if we really want to understand distance it's no good looking a ruler.

I am really curios you said no about ' time depends on anyone or anytihng' . Please prove it...

Er, YOU are the one that made the claim - Time depends on anything or any different person - it's up to you to support your point.
Time does NOT depend on a person. Or "anything". Any more than distance depends on a person or "anything".
Time is a dimension.

first, what the time actually is, it's a kind of unit (what i call it) with which we can easily place various events (or anything else like that) of past present and future which can help us a lot regarding various things(you know those...)

Now, time is created by us, (at least in our world) so yes it cannot be same everywhere but i don't think time can run slower or faster in different regions (unless the circumstances are different or relativistic mechanics has been applied).

The running slower or faster of time depends upon the natural circumstances like on our planet it depends on the revolution of the earth around sun, if earth's speed would be more the time would be less per day, so on other planets time would be different but actually we all will be aging the same.

Originally Posted by shailendra.devil

first, what the time actually is, it's a kind of unit (what i call it)

No it isn't.
Refer to your other post.
This one.
And then take your own advice.
And what's the first answer?
Oh, it's Wiki. And that says "Time is a dimension".
A dimension is not a unit.

Now, time is created by us

No it isn't.

so yes it cannot be same everywhere but i don't think time can run slower or faster in different regions (unless the circumstances are different or relativistic mechanics has been applied).

So what, exactly, do you mean by it cannot be the same everywhere?

The running slower or faster of time depends upon the natural circumstances like on our planet it depends on the revolution of the earth around sun, if earth's speed would be more the time would be less per day

No it doesn't.

so on other planets time would be different but actually we all will be aging the same.

If time is different how will we age at the same rate?

Originally Posted by Dywyddyr

Originally Posted by shailendra.devil

first, what the time actually is, it's a kind of unit (what i call it)

No it isn't.
Refer to your other post.
This one.
And then take your own advice.
And what's the first answer?
Oh, it's Wiki. And that says "Time is a dimension".
A dimension is not a unit.

Now, time is created by us

No it isn't.

so yes it cannot be same everywhere but i don't think time can run slower or faster in different regions (unless the circumstances are different or relativistic mechanics has been applied).

So what, exactly, do you mean by it cannot be the same everywhere?

The running slower or faster of time depends upon the natural circumstances like on our planet it depends on the revolution of the earth around sun, if earth's speed would be more the time would be less per day

No it doesn't.

so on other planets time would be different but actually we all will be aging the same.

If time is different how will we age at the same rate?

oh i am very sorry for that blunder i wanted to say quantity.

Now the argument:-

1.Yes Humans did created the so called concept of time, or what do you think it just came of of nowhere?

2.Time can be same or different it depends upon our own view, otherwise yes with respect to ...let's choose outer space here, we all will have the same time.

3.I agree, Not with respect to "space" but in case we didn't had a universal dimension then the time would be different and would flow differently for people on different planets.

4.Again we will have to take "universal dimension" concept.

I think i was unable to express myself.

Originally Posted by shailendra.devil

oh i am very sorry for that blunder i wanted to say quantity.

It's not a quantity either.

Now the argument:-
1.Yes Humans did created the so called concept of time, or what do you think it just came of of nowhere?

What you actually wrote was - "time is created by us". This is false.
Time existed before we were here. What WE did was assign a name to it.

2.Time can be same or different it depends upon our own view

What?

otherwise yes with respect to ...let's choose outer space here, we all will have the same time.

You've just contradicted yourself. Again.
Unless you're talking about our perception of time (it goes slowly when we're bored etc). But that is merely a perception, not a reality.

3.I agree, Not with respect to "space" but in case we didn't had a universal dimension then the time would be different and would flow differently for people on different planets.

What?
Time does NOT flow differently for people on other planets.
What does happen, however is that certain arbitrary units will have a different "size" attached to an equally arbitrary name.
Simply because someone on Earth calls one orbit around our Sun a "year" does not affect the actual rate of "flow" of time because a different planet takes more, or less, time to complete its own orbit.

4.Again we will have to take "universal dimension" concept.

What?

Originally Posted by Dywyddyr

Originally Posted by shailendra.devil

oh i am very sorry for that blunder i wanted to say quantity.

It's not a quantity either.

Now the argument:-
1.Yes Humans did created the so called concept of time, or what do you think it just came of of nowhere?

What you actually wrote was - "time is created by us". This is false.
Time existed before we were here. What WE did was assign a name to it.

2.Time can be same or different it depends upon our own view

What?

otherwise yes with respect to ...let's choose outer space here, we all will have the same time.

You've just contradicted yourself. Again.
Unless you're talking about our perception of time (it goes slowly when we're bored etc). But that is merely a perception, not a reality.

3.I agree, Not with respect to "space" but in case we didn't had a universal dimension then the time would be different and would flow differently for people on different planets.

What?
Time does NOT flow differently for people on other planets.
What does happen, however is that certain arbitrary units will have a different "size" attached to an equally arbitrary name.
Simply because someone on Earth calls one orbit around our Sun a "year" does not affect the actual rate of "flow" of time because a different planet takes more, or less, time to complete its own orbit.

4.Again we will have to take "universal dimension" concept.

What?

Sorry i was confused, now i understand the things, thanks sir.

Originally Posted by Dywyddyr

What?
Time does NOT flow differently for people on other planets.
What does happen, however is that certain arbitrary units will have a different "size" attached to an equally arbitrary name.
Simply because someone on Earth calls one orbit around our Sun a "year" does not affect the actual rate of "flow" of time because a different planet takes more, or less, time to complete its own orbit.

Nitpick:
Time will flow at the same rate, however, the perception of that rate will vary slightly by planet, assuming close to Earth sized rocky planets and life on other things, like on gas giants, on stars, within nebula or other "extreme conditions" will see a much greater variance in their perception of the rate of time relative to ours.

Time, yet not a very clear idea in physics.
If Time exist physically : Possibly general view is that it does not exist
It is a medium of measurement
Space-time is different concept and is not completley replaced with word "time" which we daily use
Space-time is accepted by physics community but yet it is limited explained

Originally Posted by RAJ_K

If Time exist physically : Possibly general view is that it does not exist

That might be your personal opinion, but it is certainly not the general consensus.

It is a medium of measurement

No, it is a geometric aspect of space-time, and hence quite real. To be exact it is simply the arc length of a world line connecting two events. It is well defined, and physically measurable.

Space-time is different concept and is not completley replaced with word "time" which we daily use

Of course it is different. Time is not the same as space-time, but it is an aspect of the latter.

Space-time is accepted by physics community but yet it is limited explained

In what way is not properly explained, exactly ?

Change in Time Rate is common thing and not surprising
It is "change" by which we feel passing of time . Gravity and many other factors possibly make effect on the rate of "Change"


If I walk on a road, I would walk 1km in a certain time
If I walk on wet sand, no doubt I would take long time as wet sand force on my feet.

Originally Posted by RAJ_K

If I walk on a road, I would walk 1km in a certain time
If I walk on wet sand, no doubt I would take long time as wet sand force on my feet.

Which is nothing whatsoever to do with time as time.

This is just an example to show how forces effect "rate of change" and does not related to time
That is why time will flow fast at a distance from heavy body than near a heavy planet

Originally Posted by RAJ_K

It is a medium of measurement

So is length. Does that mean that "space" does not exist as well?

(Why do we suddenly seem to have half a dozen stupid threads discussing time?)

Originally Posted by Strange

Originally Posted by RAJ_K

It is a medium of measurement

So is length. Does that mean that "space" does not exist as well?

(Why do we suddenly seem to have half a dozen stupid threads discussing time?)

Because it is a pass-time.

Seriously though, you are talking of the same thing.

Time is a Delta, and space also. Maybe RAJ express that poorly, but time exist because you measure it.
Being Markus arc of world line, or number of sun burn after a mile walk.

Let's agree to agree for once (upon a time)

Markus Hanke, April 16th, 2013, 05:40 AM

Quote Originally Posted by RAJ_K View Post

If Time exist physically : Possibly general view is that it does not exist

That might be your personal opinion, but it is certainly not the general consensus.

It is a medium of measurement

No, it is a geometric aspect of space-time, and hence quite real. To be exact it is simply the arc length of a world line connecting two events. It is well defined, and physically measurable.

Space-time is accepted by physics community but yet it is limited explained

In what way is not properly explained, exactly ?

I am a little confused by your statement that time is well defined and physically measurable. It begs the question to make a measurement of say 2 hours of space, or if you consider time as being a causal agent.

I thought that 3d space is physically measurable because it has dimensions, but time is the duration required to measure movement and distance in space. This would mean that time is a result of measurement, not an inherent condition. Neither can exist independently, because time is always created during instantiation of reality.

I see this as somewhat similar to the particle duality, where the probability wave collapses and the particle instantiates as a result of (during) measurement. Spacetime duality also requires a measurement for time to come into existence as a result of (during) measurement.

Originally Posted by Write4U

I thought that 3d space is physically measurable because it has dimensions, but time is the duration required to measure movement and distance in space.

The three spatial dimensions can be measured with a ruler, the fourth temporal dimension can be measured with a clock.

Strange,
The three spatial dimensions can be measured with a ruler, the fourth temporal dimension can be measured with a clock.

That still does not satisfy me. Perhaps the measurement can be made with a clock, but time still depends on the use of your ruler measuring the distance. You cannot measure distance with time at all unless you have a ruler.

Originally Posted by Write4U

That still does not satisfy me. Perhaps the measurement can be made with a clock, but time still depends on the use of your ruler measuring the distance.

Huh? I look at my watch. I use an atomic clock. I build an RC oscillator. Where does a ruler come into it?

You cannot measure distance with time at all unless you have a ruler.

RADAR: RAdio Detection And Ranging; it works by measuring time.
Lunar Laser Ranging experiment; it works by measuring time.

Originally Posted by Write4U

That still does not satisfy me. Perhaps the measurement can be made with a clock, but time still depends on the use of your ruler measuring the distance. You cannot measure distance with time at all unless you have a ruler.

I'm sorry, but I've been sat at my computer looking at this claim for 35 minutes 15 centimetres (and, possibly, an additional 8 kilogrammes 3 volts) and I still can't make head nor tail of it.

Originally Posted by Write4U

Strange,
The three spatial dimensions can be measured with a ruler, the fourth temporal dimension can be measured with a clock.

That still does not satisfy me. Perhaps the measurement can be made with a clock, but time still depends on the use of your ruler measuring the distance. You cannot measure distance with time at all unless you have a ruler.

You are right to be unsatisfied.

You need space-time to measure time, and you need space-time to measure space. That is because we live in 4D.

Strangely, some people using atomic watch forget that those clock need to occupy space so we could measure the difference between spacially located "event": a decay

A likewise people measuring space cannot do that without having a watch to synchronize two different measure, or stop bothering and directly use light speed and wait a little for it to bounce back.

Time is the forth dimension of space-time.

Thread closed

Originally Posted by Boing3000

[Strangely, some people using atomic watch forget that those clock need to occupy space so we could measure the difference between spacially located "event": a decay

Well, clearly, an atomic clock takes up space. But it doesn't measure decay. Nor does it measure the difference between spatially located events. But apart from that ...

Strange,
RADAR: RAdio Detection And Ranging; it works by measuring time.
Lunar Laser Ranging experiment; it works by measuring time.

Yes, as measured by the speed of light (c), which is a spatial measurement.

Originally Posted by Strange

But it doesn't measure decay.

Gosh, that explain why my wrist had turned green.

Originally Posted by Strange

Nor does it measure the difference between spatially located events.

Just checking. A photon emitted by a electron, by changing energy level (not decaying, but close enough for me) is measured how exactly ?
I though it was received at another spacial coordinate, or event.

Originally Posted by Boing3000

Just checking. A photon emitted by a electron, by changing energy level (not decaying, but close enough for me) is measured how exactly ?
I though it was received at another spacial coordinate, or event.

But that is not what provides the measurement of time. It is the frequency of that radiation.

Originally Posted by Strange

But that is not what provides the measurement of time. It is the frequency of that radiation.

OK, but does it not mean the energy of one photon ? How is it measured ?
Surely not measuring frequency using another clock...

Originally Posted by Strange

Originally Posted by RAJ_K

It is a medium of measurement

So is length. Does that mean that "space" does not exist as well?

(Why do we suddenly seem to have half a dozen stupid threads discussing time?)

Space may be existed physically or may not be
Are you sure space exists physically ?

Originally Posted by Strange

Originally Posted by Boing3000

Just checking. A photon emitted by a electron, by changing energy level (not decaying, but close enough for me) is measured how exactly ?
I though it was received at another spacial coordinate, or event.

But that is not what provides the measurement of time. It is the frequency of that radiation.

You are using word "time" Why are not you using word "spacetime"?
Are both same or different ?

[QUOTE=Boing3000;413766]

Originally Posted by Strange

OK, but does it not mean the energy of one photon ? How is it measured ?

It's counted.
You know: 1, 2, 3, 4...

Originally Posted by RAJ_K

You are using word "time" Why are not you using word "spacetime"?

Because we're discussing time, not spacetime.

Are both same or different ?

Hey! I wonder if that's why there's two different terms?

Originally Posted by RAJ_K

Space may be existed physically or may not be
Are you sure space exists physically ?

You are not here are you. You are there.

Wrong!
I'M here. It's you that is THERE. He's somewhere else altogether.

Originally Posted by Dywyddyr

Originally Posted by Boing3000

OK, but does it not mean the energy of one photon ? How is it measured ?

It's counted.
You know: 1, 2, 3, 4...

lol. Your are also able to count frequency, using your fingers I suppose.

My, my, but we have a really really genius Duck...

Originally Posted by Boing3000

Originally Posted by Strange

But that is not what provides the measurement of time. It is the frequency of that radiation.

OK, but does it not mean the energy of one photon ? How is it measured ?
Surely not measuring frequency using another clock...

I have never looked into the details. Basically, I believe it uses some sort of mechanism to synchronise an electronic oscillator with the frequency of the atomic clock - then the output of that can be counted!

Originally Posted by RAJ_K

Space may be existed physically or may not be
Are you sure space exists physically ?

Are you Indian ? There seems to be a language gap here. Maybe there is many word in you language that relate to the English word "physics".

Your are gonna be bullied out of the site because some smart people here (and even not smart one) do think there is a only one possibility to grasp a word.

Anyway, to respond: space-time IS composed of space and time, and on thescienceforum IS a synonym to physics, physical, measurable, testable. For sure, or within the boundaries of uncertainty principle.

For other meaning about physical and sure'ness, there is a philosophy sub forum, which is also quite fun

Originally Posted by Strange

Basically, I believe it uses some sort of mechanism to synchronise an electronic oscillator with the frequency of the atomic clock - then the output of that can be counted!

Of course it can be counted, and any way of counting thing is to observe a difference in space (like something was not there, and now is) <-- note that I had to use the past tense (a time thing))

Everybody is saying the same thing here, all there is space and time(*), and is local to the observer, which experience it by differences two related event.


(*) Excluding all various had hoc constant measured anyway through space time event. Here it is, I have GUT again.

Strange, April 6th, 2013, 09:01 AM,

Quote Originally Posted by Boing3000 View Post

Just checking. A photon emitted by a electron, by changing energy level (not decaying, but close enough for me) is measured how exactly ?
I though it was received at another spatial coordinate, or event.

But that is not what provides the measurement of time. It is the frequency of that radiation.

But, but, you cannot measure time with frequency. IMO, frequency is a unit of time by which something can be measured. But how do you measure time itself. In principle it is infinite because time is always created along with reality itself.
In an atomic clock it is the frequency of change of the atom which allows for accurate time measurement, but it's function, counting, is no different then a regular wind-up clock.

But "in time" where do you begin and where do you end and how do you know how far you've come except to measure the starting coordinate and number of wavelengths to the endpoint, all physical dimensions?

Time has no way to measure itself. IMO, time is a universal potential, a latent excellence which becomes a measurable dimension with physical change, it is a non-causal result, a by-product of causal change in reality.
But I admit it is my intuitive take on time.

Originally Posted by Write4U

Strange, April 6th, 2013, 09:01 AM,

Quote Originally Posted by Boing3000 View Post

Just checking. A photon emitted by a electron, by changing energy level (not decaying, but close enough for me) is measured how exactly ?
I though it was received at another spatial coordinate, or event.

But that is not what provides the measurement of time. It is the frequency of that radiation.

But, but, you cannot measure time with frequency. IMO, frequency is a unit of time by which something can be measured. But how do you measure time itself. In principle it is infinite because time is always created along with reality itself.
In an atomic clock it is the frequency of change of the atom which allows for accurate time measurement, but it's function, counting, is no different then a regular wind-up clock.

But "in time" where do you begin and where do you end and how do you know how far you've come except to measure the starting coordinate and number of wavelengths to the endpoint, all physical dimensions?

Time has no way to measure itself. IMO, time is a universal potential, a latent excellence which becomes a measurable dimension with physical change, it is a non-causal result, a by-product of causal change in reality.
But I admit it is my intuitive take on time.

We know what is spacetime
and how heavy bodies change its geometry
Is presence of spacetime depends upon matter ?
Without matter it cannot exist?
If without matter it can exist and it exist physically, is it not matter/energy in itself?

Originally Posted by Write4U

But, but, you cannot measure time with frequency. IMO, frequency is a unit of time by which something can be measured. But how do you measure time itself.

Riiight.

You cannot measure space with a ruler. IMO, a ruler is a unit of distance by which something can be measured. But how do you measure space itself.

Originally Posted by Strange

Originally Posted by Write4U

But, but, you cannot measure time with frequency. IMO, frequency is a unit of time by which something can be measured. But how do you measure time itself.

Riiight.

You cannot measure space with a ruler. IMO, a ruler is a unit of distance by which something can be measured. But how do you measure space itself.

Nice try.
What could be the difference between a frequency and a ruler... maybe one is an per-time mathematical useless quantity/number (to make a measurement), and the other is a complete space-time physical entity, usable for measurement, but about which everybody using math a GR will disagree about its quantifiable length.

I am wondering how it is possible to disagree that you cannot measure time using time, nor measure meter using meters.

Here the frequency would be (I suppose) tested by diffraction which would give a spacial deviation between two photon.
If there is another way to guess the frequency of a photon without using any spacial apparatus, I'll would learn something new.

You guys are still trying to separate time and space. So once again : time and space do not exist, there is only space-time. In space-time you measure the distance between two events via the arc length of the geodesic connecting the two :



The physical unit for this is actually the meter, which is why the time coordinate in relativity is denoted "ct" and not just "t", as otherwise the dimensions of the integral above would be physically meaningless. You relate these results to clock readings ( proper time readings ) by multiplying/dividing by c.
Measuring "just time" is possible only for events which are not spatially separated, in which case the spatial differentials under the above integral all vanish, but the ct element does not.

You all need to get away from the notion of trying to measure or define "time", because that is a meaningless concept. There is only space-time, which is modelled as a smooth differentiable pseudo-Riemannian manifold, so you can easily define distances on it via the arc length of geodesics, as above. This takes a bit of a paradigm shift, and a healthy amount of getting used to, but once the shift has been performed all ambiguities vanish. Most of the confusion in discussing time stems from erronously trying to separate it from space; trying to perform such a separation is like trying to separate the horizontal threads from the vertical ones in a quilt. It makes no sense. Both time and space are just aspects of the same manifold.

Originally Posted by Markus Hanke

You relate these results to clock readings ( proper time readings ) by multiplying/dividing by c.

Before someone jump here to signal that you cannot divide by c, but you need some countable numbers, here is how you count them.

There are probably a bunch of aliens with the same sense of practicality then us, and vaguely bipedal. They think c=149896229
Question: how do their arm span relate to ours...

Originally Posted by Boing3000

Originally Posted by Markus Hanke

You relate these results to clock readings ( proper time readings ) by multiplying/dividing by c.

Before someone jump here to signal that you cannot divide by c, but you need some countable numbers, here is how you count them.

There are probably a bunch of aliens with the same sense of practicality then us, and vaguely bipedal. They think c=149896229
Question: how do their arm span relate to ours...

idk, but their metre must be twice as long.

Originally Posted by curious mind

Originally Posted by Boing3000

Originally Posted by Markus Hanke

You relate these results to clock readings ( proper time readings ) by multiplying/dividing by c.

Before someone jump here to signal that you cannot divide by c, but you need some countable numbers, here is how you count them.

There are probably a bunch of aliens with the same sense of practicality then us, and vaguely bipedal. They think c=149896229
Question: how do their arm span relate to ours...

idk, but their metre must be twice as long.

Yes, approximately, and so, unless they measure distance with their foot (like some does here), they must be pretty scary fellows

*** deleted ***

Originally Posted by Markus Hanke

You guys are still trying to separate time and space. So once again : time and space do not exist, there is only space-time. In space-time you measure the distance between two events via the arc length of the geodesic connecting the two :



The physical unit for this is actually the meter, which is why the time coordinate in relativity is denoted "ct" and not just "t", as otherwise the dimensions of the integral above would be physically meaningless. You relate these results to clock readings ( proper time readings ) by multiplying/dividing by c.
Measuring "just time" is possible only for events which are not spatially separated, in which case the spatial differentials under the above integral all vanish, but the ct element does not.
.

It seems more accurate , space and time may not exist,

Is spacetime exist physically ?
If yes
Can space time exist if there is no matter
If No

It means, Its just a property of matter and not a space itself

i thought you can have voids?

"space", "time" and "spacetime" are differents words and denote them with different meaning

What is clear answer ?

Does space time exist physically ?

a) Yes b)No c) not sure i.e. may be or may not be


Does physically existence of "spacetime" depends on matter i.e. if there is no matter space time yet can exist

a) yes b)no c)not sure


We know well presence of matter change geopmetry of spacetime and it is proved

Is there a difference between "exist" and "physically exist"? (Just trying to understand what you mean...)

Originally Posted by Strange

Is there a difference between "exist" and "physically exist"? (Just trying to understand what you mean...)

Possibly every thing that can be observed, have mass/energy or other known or unknown particles, is physically existed thing from photon to planet to universes
All these things have properties and behavior
Law of Physics apply on all these physically existed things

But possibly yet "space" and "time" not space time is to be believed not physically existed

Time, like place is a coordiante in 4 dimensional space. With the specific propery that observations can only follow eachother up with a positive time difference.
To what exists and physically exist, we can dwell on that a long time. What exists, is what we can observe, but some things we don't or will not observe, yet are still able to influence. Do they exist? yes, but they can't be observed. Nature cannot be observed by us, since we cannot entangle with nature, the way nature does. And hence we as humans can never really see all that is possible.

time is nothing but comparing one periodic phenomenon with another

Why are phenomena periodic?

Why does a caesium atom always change between hyperfine levels of its ground state 9,192,631,770 times whilst a photon travels a distance of 299,792,458 metres?

What links these two things?

Originally Posted by parag29081973

time is nothing but comparing one periodic phenomenon with another

I get what (I think) you mean, but: the two events/ phenomena need not be periodic.

i love this!!!! time again. time dont exists . energy and space yes. time is like a formula that shows that the lower the energy the soon it ends. and the higher the energy the more it lasts. (not that energy loses but get me right...) so basicly time is in the same direction with the energy and in wrong direction with space. so time=energy/space i think.

Originally Posted by sokohila

i love this!!!!

Possibly.
But you CLEARLY don't understand the process at work here.

time dont exists

If all you have is your unsupported claim then you have, once again, failed completely to establish your point. Or your credibility.

so time=energy/space i think.

Nonsense.

nothing makes sense to you . anyway its your brain

Your posts don't.
Unsupported assertions are not evidence.
They're not worth consideration.
Either support your claim, with evidence and logic or shut up.