what is time?

[Eise]

Time measurement is connected with change. If something does not change, I don't agree that no time has passed for it. Only that we can't use that to quantify how much time has passed.

 

Seems you want it the hard way too...

 

Suppose we have a closed system in which there is no change.

 

Does time pass in the system? How can we know without entering the system, i.e. introducing time ourselves? And which was supposed to be a closed system?

 

So if you say that time passes when there is no change, you say something that is impossible to know, as a matter of principle. Time does not exist independent of change. Just in the same way that space does not exist without lengths or distances. Both space and time are abstract principles without physical meaning. Distances and changes have physical meaning: they can be observed.

[StringJunky]

Change shows that time has passed but it is not time itself; time passes in the absence of change. We need a clock to measure it - which is something that changes - but it is not a necessary condition that the thing under observation also needs to change for time to be occurring. Time is happening everywhere where there is space because time - as per Relativity - is inextricably bound with it.

[swansont]

 

Seems you want it the hard way too...

 

Suppose we have a closed system in which there is no change.

 

Does time pass in the system? How can we know without entering the system, i.e. introducing time ourselves? And which was supposed to be a closed system?

 

So if you say that time passes when there is no change, you say something that is impossible to know, as a matter of principle. Time does not exist independent of change. Just in the same way that space does not exist without lengths or distances. Both space and time are abstract principles without physical meaning. Distances and changes have physical meaning: they can be observed.

 

Physics disagrees with you. Time in any inertial frame is the same at all points, regardless of whether you can isolate part of it. If you violate this, you violate relativity, and physics breaks. Good luck coming up with a consistent theory of relativity (and all the physics that depends on it) that violates Lorentz invariance.

[Eise]

Change shows that time has passed but it is not time itself; time passes in the absence of change.

 

There is no way of knowing that.

 

We need a clock to measure it - which is something that changes - but it is not a necessary condition that the thing under observation also needs to change for time to be occurring.

 

'Time occurring': don't you see the difficulty in this phrase? Something occurring means that something is changing. Is time occurring then? (Does time have speed? )

 

Time is happening everywhere where there is space because time - as per Relativity - is inextricably bound with it.

 

I already gave the example of the 'relativistic twin experiment'. How do I know that less time has passed for the traveling brother? Because there was less change. Is there a way to know that less time passed without noticing the amount of change? So is there a way to know if exists independent of change?

[swansont]

So is there a way to know if exists independent of change?

 

If time didn't proceed everywhere in space according to the laws of physics, then we would see the effects of that. Is your idea even testable?

[Eise]

Physics disagrees with you. Time in any inertial frame is the same at all points, regardless of whether you can isolate part of it. If you violate this, you violate relativity, and physics breaks. Good luck coming up with a consistent theory of relativity (and all the physics that depends on it) that violates Lorentz invariance.

 

Physics says nothing about it. Everytime when we do the experiments, we have to look at change, be it a clock or a twin that is much younger than his brother. You cannot say that 'Time in any inertial frame is the same at all points' without giving it an operational definition, with clocks and distances. In 'On the Electrodynamics of Moving Bodies' Einstein is explicitly using clocks and rods. I think it was because he saw that the concepts of time and space taken on its own are empty, and you have to use operational definitions. Saying that time is slower in another inertial system is in fact saying that changes there are slower.

If time didn't proceed everywhere in space according to the laws of physics, then we would see the effects of that. Is your idea even testable?

 

You make the same mistake as StringJunky: time doesn't proceed. Changes proceed. So changes are occurring in the way that the laws of physics describe. Can you describe me how you can test that time exists without change? Is that idea testable?

Edited November 29, 2014 by Eise

[swansont]

Physics says nothing about it.

Um, whut?

 

Everytime when we do the experiments, we have to look at change, be it a clock or a twin that is much younger than his brother. You cannot say that 'Time in any inertial frame is the same at all points' without giving it an operational definition, with clocks and distances. In 'On the Electrodynamics of Moving Bodies' Einstein is explicitly using clocks and rods. I think it was because he saw that the concepts of time and space taken on its own are empty, and you have to use operational definitions.

Yes, he uses the definition that time is what you read on a clock. That doesn't say what time is, but defines the measurement of it.

 

Saying that time is slower in another inertial system is in fact saying that changes there are slower.

 

Yes, but you are insisting that the converse is true, so this means nothing. I can slow a chemical reaction down by lowering the ambient temperature. Have I slowed time down? My clock says no.

 

You make the same mistake as StringJunky: time doesn't proceed. Changes proceed. So changes are occurring in the way that the laws of physics describe. Can you describe me how you can test that time exists without change? Is that idea testable?

 

I can test the consistency of relativity, and see that length contraction and time dilation must be occurring with particles (muons) that don't decay, i.e. they have not undergone a change, which confirms the validity of relativity.

[Rilx]

My definition is that time is the fourth spatial dimension. It is orthogonal to the other three, because it separates objects which occupy the same location.

 

The definition doesn't imply linear time (actually the same case as with the other three) but it exists in defining linear measures of time. When the shadow of sundial's style again occupy the same location, one day has passed. Or a pendulum again returns to the same position, or periods of any kind of harmonic oscillators can and are used for measures of time. The periodical change which begins and ends the same location (or the same relative position in the system) is always in the background.

[Eise]

Yes, he uses the definition that time is what you read on a clock. That doesn't say what time is, but defines the measurement of it.

 

Right. It doesn't even say that time is. Time is just a useful abstraction for change. Compare this with e.g temperature: we can analyze temperature in terms of kinetic energy. But there is no independent way of observing time than observing change.

 

Yes, but you are insisting that the converse is true, so this means nothing. I can slow a chemical reaction down by lowering the ambient temperature. Have I slowed time down? My clock says no.

 

No, because the systems are not identical anymore. Remember that that was the point where I started? With identical systems, that started with the same initial conditions. When after a while they did not develop the same, then they were not identical (lower ambient temperature) or I can conclude that both reactions did not start at the same time. Your clock will say yes...

 

I can test the consistency of relativity, and see that length contraction and time dilation must be occurring with particles (muons) that don't decay, i.e. they have not undergone a change, which confirms the validity of relativity.

 

No! The muons decay, i.e. change, slower, that is what I observe. And so I say time has slowed down, but there is no time apart from the change. See my example of the decaying radium yesterday.

Edited November 29, 2014 by Eise

[swansont]

Right. It doesn't even say that time is. Time is just a useful abstraction for change. Compare this with e.g temperature: we can analyze temperature in terms of kinetic energy. But there is no independent way of observing time than observing change.

Which is not the same as saying time doesn't exist if there is no change.

 

No! The muons decay, i.e. change, slower, that is what I observe. And so I say time has slowed down, but there is no time apart from the change. See my example of the decaying radium yesterday.

A muon that has not decayed has not changed at all. Does time pass only in little bits of space as muons pass by?

[MigL]

I'm gonna have to say you've got it back-assward, Eise.

We measure change using time.

It is very convenient that the inverse also happens to work out and we can use change to measure time also.

 

As SringJunky has stated, time proceeds ( rather the local 'now' proceeds ), and that allows us to gauge the amount of change.

But at any instant in time, there is no change. A foliation of the manifold which is space-time, has no movement in the three spatial dimensions. This is, of course classical GR, where every event ( x,y,z,t co-ordinate ) is 'fixed'.

 

AS for QM, bearing in mind that I'm not sure about this, is it accepted that electron orbital jumps are instantaneous ? Even granting that a lot of orbitals overlap, so this isn't necessarily a violation of locality, would this not allow for change without the passage of time ?

[davidivad]

the electron's wave function is spread out.

it can therefore become local at the most possible spot.

once the wave collapses, it is considered local or "real"

[Eise]

But there is no independent way of observing time than observing change.

 

Which is not the same as saying time doesn't exist if there is no change.

 

But it is also not the same as saying time exists. Everytime you would like to prove that time exists you must refer to change. 'Time' is just a superfluous metaphysical category.

 

A muon that has not decayed has not changed at all. Does time pass only in little bits of space as muons pass by?

 

Oh, come on Swansont, you can do better. I gave the example with the radioactive substance already. Halftime of the moving muons is longer. That means they change slower than the muons that are more or less stationary in my laboratory.

We measure change using time.

 

And what is 'using time' else than comparing it to a 'standard-changer' (aka a clock). Everytime one makes the concept of time operational, you must refer to some other process.

 

AS for QM, bearing in mind that I'm not sure about this, is it accepted that electron orbital jumps are instantaneous ? Even granting that a lot of orbitals overlap, so this isn't necessarily a violation of locality, would this not allow for change without the passage of time ?

 

No idea. But how do you think you can answer the question without referring to something that changes?

Edited November 30, 2014 by Eise

[elfmotat]

Time is what's measured by clocks. Why does anyone bother with these useless semantic descriptions, like "time is an illusion," or "time is just change"? Why not ask how many angels can dance on the head of a pin while we're at it?

[StringJunky]

Time is what's measured by clocks. Why does anyone bother with these useless semantic descriptions, like "time is an illusion," or "time is just change"? Why not ask how many angels can dance on the head of a pin while we're at it?

I've half a mind to start a thread on the ontology of length.

[Eise]

Time is what's measured by clocks.

 

So it seems that yo have an answer to the question: for you there is at least one angel is dancing on the pin of the head.

 

Why does anyone bother with these useless semantic descriptions, like "time is an illusion," or "time is just change"?

 

I don't bother. But somebody asked and I gave my answer. And as you see this provoked some strong reactions. Isn't that funny?

 

And just for the record: I do not belong to the 'new age' category of people who say that time is an illusion. Even if I would say something like that, but would immediately followup with "but change isn't", I would be spit out as a shallow materialist. (which I am not. I am a deep materialist... )

 

And, btw, there was some famous physicist, who sent the widow of his beloved friend Besso, as comfort, that time is an illusion.

I've half a mind to start a thread on the ontology of length.

 

No, no, that is not fair. It should be about space then. Length can be easily defined by comparing it with standard lengths, as duration can be defined by comparing it with standard durations, like clocks.

[Strange]

Oh, come on Swansont, you can do better. I gave the example with the radioactive substance already. Halftime of the moving muons is longer. That means they change slower than the muons that are more or less stationary in my laboratory.

 

I think you miss the point. A muon doesn't change faster or slower because, until the moment it decays, nothing changes. The amount of time it spends not changing (before it decays) varies depending on velocity.

 

The usual response to this is to beg the question and insist that there must be some unseen mechanism causing change. But that is just inventing something non-existent to support an opinion.

[Eise]

 

I think you miss the point. A muon doesn't change faster or slower because, until the moment it decays, nothing changes. The amount of time it spends not changing (before it decays) varies depending on velocity.

 

The usual response to this is to beg the question and insist that there must be some unseen mechanism causing change. But that is just inventing something non-existent to support an opinion.

 

I don't think I missed it. I already said before that time in QM is as difficult to understand as is location. I also implied some postings before that taking a single radioactive nucleus is not a good device for e.g. confirming the twin paradox. You should take at least a huge amount of them.

 

The change is in the number of muons, that decreases slower when flying close to the speed of light. More I have never said or implied. Maybe I was not so precise, but I thought that wasn't needed here. Maybe I am wrong?

[Strange]

I don't know what radioactive nuclei or the twin paradox have to do with it.

 

Maybe I am wrong?

 

It certainly seems that way.

 

 

The change is in the number of muons

 

Clearly, you totally miss the point.

 

Take a single muon. It does nothing; nothing changes. After some time has passed (despite nothing changing) it decays. So in what sense does time only exist when something changes.

 

 

Isn't that funny?

 

I hate that sort of smug comment. ("My opinion must be right because look how it angers the poor fools".)

[davidivad]

1

if anyone could tell me whether or not this disagrees with any regulations it would be much appreciated.

could it therefore be considered that everything has its own time?

i say this because i am considering that cooling down the atoms removes all noise in the system so that the natural frequency can be utilized.

i know this is a jump, but does that idea conform to the way time is handled with any current method?

 

one could imagine that if everything had its own clock based on its natural frequency then it would only be constrained by the speed of light.

in other words each has its own time and can be affected by speed of light transmissions of force carriers.

remember, this is just an idea.

 

edit:

under such conditions, waves themselves are constrained by the light constant and time is dependant on the object itself while interacting with its medium.

gravitational information might be passed through thier own force carier..

i am only speculating here.

 

this is not my concept of time neccessarily but is something worth testing.

strange?

how about it?

Edited November 30, 2014 by davidivad

[Eise]

I don't know what radioactive nuclei or the twin paradox have to do with it.

 

Would you mind to read the thread from the point on where I chimed in? Otherwise I have to repeat everything.

 

Take a single muon. It does nothing; nothing changes. After some time has passed (despite nothing changing) it decays. So in what sense does time only exist when something changes.

 

From a single muon itself you will never be able to conclude that time has passed. Only when compared to a standard-changer device. Just for the ease, say a muon has a halftime of 1 μs. I give a muon to you, and after 1ns it decays. Can you now tell that the muon must have lived already a while, because it decayed so fast? Say I repeat this a thousand times. I give you a muon and you measure the decay times. Do you think you can conclude that all my muons are 'older' because you find a shorter halftime?

 

I hate that sort of smug comment. ("My opinion must be right because look how it angers the poor fools".)

 

Sorry, but that is not what I meant. I don't think I am right because of the many reactions. I was saying that people seem to care, as elfmotat says, about how many angels can dance on the head of a pin. Read better, in context.

[davidivad]

http://www.wired.com/2014/04/quantum-theory-flow-time/

 

here is an article that states quantum theory's latest concerning the flow of time.

according to the article, it is due to quantum entanglement.

 

“Finally, we can understand why a cup of coffee equilibrates in a room,” said Tony Short, a quantum physicist at Bristol. “Entanglement builds up between the state of the coffee cup and the state of the room.”

 

Twenty-six years after Lloyd’s big idea about time’s arrow fell flat, he is pleased to be witnessing its rise and has been applying the ideas in recent work on the black hole information paradox. “I think now the consensus would be that there is physics in this,” he said.

Not to mention a bit of philosophy.

 

yea, thats what i'm saying...

dinner is served.

Edited November 30, 2014 by davidivad

[swansont]

But it is also not the same as saying time exists. Everytime you would like to prove that time exists you must refer to change. 'Time' is just a superfluous metaphysical category.

 

 

And every time you want to prove gravity exists you must have something at the place you want to test it. Does that mean gravity only exists during the measurement? That's not what the theory says, and the theory has been well-tested. What's the theory, where time turns on and off, depending on if change happens? You still haven't answered that.

[davidivad]

let me see here.

we are refuting the concept of time via relativity in a quantum theory thread when we have a reasonable answer.

im all ears for somwething better.

[Eise]

 

And every time you want to prove gravity exists you must have something at the place you want to test it. Does that mean gravity only exists during the measurement? That's not what the theory says, and the theory has been well-tested. What's the theory, where time turns on and off, depending on if change happens? You still haven't answered that.

 

Aha, maybe I see the misunderstanding. I am not saying that time is turned on and off depending on if there is change or not. I am saying (nearly your words!) that time is an abstraction of change. As it is with abstractions, they have no self-existence. They are certain aspects that have certain objects in common. Now change is everywhere in the universe. It is simply one of the broadest aspects that everything has in common. And even if I am observing a system that does not change during my observation, my observation in itself is a process (maybe accompanied with my standardised change-device to see how much it changed during my observing the not changing system).

 

As for gravity: it is always connected with mass (or energy if you want). So my tests for gravity will not always be positive. But everywhere I want to measure a duration, there is change: I need a clock of some kind.

 

Some people say that the time is the necessary condition for change: without time, change would be impossible. But this is of course an untestable theory. I cannot turn time off, and look if there is still change. Time is not the cause of change. Time is only given to us through change. Time is not accessible for us, except through change. So why should I say that this abstraction of time exists? Why is change not enough? As an empirical science, physics cannot tell us if time exists. Physics can only tell us if something exists if it causes something. But as said, time does not cause change. Changes are caused by other changes. And physics describes how changes happen, depending on the kind of objects involved and the initial conditions.