what is time?

[swansont]

 

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.

 

 

And I will refer you to my earlier observation that the "nature of time" and "time measurement" are not the same thing, and from your statements, you seem to agree — all of your references are to measurement of time. The accepted and well-tested theories of physics say that time in any inertial frame proceeds at the same rate. To that there can really be no argument; it is a fact that this is part of relativity. There is nothing in the framework of relativity that requires change.

[Eise]

And I will refer you to my earlier observation that the "nature of time" and "time measurement" are not the same thing, and from your statements, you seem to agree — all of your references are to measurement of time.

 

But measurement of time always is comparing it to some standard of time! That means: compare it with something that changes.

 

The accepted and well-tested theories of physics say that time in any inertial frame proceeds at the same rate. To that there can really be no argument; it is a fact that this is part of relativity. There is nothing in the framework of relativity that requires change.

 

What do you want to say with 'well-tested'? I am not questioning RT. I am only questioning if time exists as an independent entity. And as said, Einstein uses clocks, and 'light explosions' (events) to build his SRT (at least in the beginning). You seem to think that every inertial frame drags his own time with it.

 

What I can say of an inertial frame is that if I would have a clock in it, and I am in another inertial frame that moves against the other, that the clock would seem to go slower than exactly the same clock in my inertial frame. Same with another clock, put in the same inertial frame as the first clock. That is the meaning of 'the same time everywhere in one inertial frame'. And don't forget, an inertial frame is an abstraction too...

 

Edit: it of course means that an other, identical clock in my own inertial frame changes just as fast as mine.

And again you are using the phrase 'time proceeding'. Things change in time, or said differently, processes occur in time. Proceeding can only be defined by using the concept of time. That's not far from asking what is the speed of time in my own inertial frame. (My answer: it is 1, a dimensionless constant... It turns out it is exactly the same as the volume of space, which is also the same dimensionless 1.)

Edited November 30, 2014 by Eise

[swansont]

But measurement of time always is comparing it to some standard of time! That means: compare it with something that changes.

 

Yes, measurement. But only measurement.

 

What do you want to say with 'well-tested'? I am not questioning RT. I am only questioning if time exists as an independent entity. And as said, Einstein uses clocks, and 'light explosions' (events) to build his SRT (at least in the beginning). You seem to think that every inertial frame drags his own time with it.

Frame dragging has a particular definition in general relativity that does not apply here, though the phrasing also brings to mind ether dragging which also does not apply, but for very different reasons.

 

Spacetime is continuous, and the Lorentz transforms apply to all inertial frames of reference. Within a frame, the Einstein clock synchronization protocol applies: all points in a frame have the same time.

 

What do you mean by an independent entity? I have not claimed anything other than time as an abstraction.

 

What I can say of an inertial frame is that if I would have a clock in it, and I am in another inertial frame that moves against the other, that the clock would seem to go slower than exactly the same clock in my inertial frame. Same with another clock, put in the same inertial frame as the first clock. That is the meaning of 'the same time everywhere in one inertial frame'. And don't forget, an inertial frame is an abstraction too...

 

Edit: it of course means that an other, identical clock in my own inertial frame changes just as fast as mine.

 

And again you are using the phrase 'time proceeding'. Things change in time, or said differently, processes occur in time. Proceeding can only be defined by using the concept of time. That's not far from asking what is the speed of time in my own inertial frame. (My answer: it is 1, a dimensionless constant... It turns out it is exactly the same as the volume of space, which is also the same dimensionless 1.)

 

But this just goes back to the same problem of e.g. gravity or electric fields, which tell us what force would be present of a charge was placed there. The fields are continuous function— they are always there, even if a charge is not.

 

Like time, these are abstractions. The part that is very confusing to me is to claim that an abstraction doesn't exist unless you are measuring some effect that can be measured. It's an abstraction — we can define it any way we want to! And we define it to exist everywhere, because that makes physics work.

[Eise]

Yes, measurement. But only measurement.

 

Yes. But my point is that the measurement is never more than comparing it with another change.

 

Frame dragging has a particular definition in general relativity that does not apply here, though the phrasing also brings to mind ether dragging which also does not apply, but for very different reasons.

 

Yep, I assume it was clear that I did not mean that.

 

What do you mean by an independent entity? I have not claimed anything other than time as an abstraction.

 

Yes. Therefore I think we nearly agree. I just wanted to stress that time is not an empirically given fact. Change is.

 

But this just goes back to the same problem of e.g. gravity or electric fields, which tell us what force would be present of a charge was placed there. The fields are continuous function— they are always there, even if a charge is not.

 

The difference is that I always find a cause of the electric field: a charge, or an electromagnetic wave. There are different modes of access to these phenomena. In the case of time I am standing 'for a wall of change'. Sorry for becoming poetic... But I never find a cause of change, except another change. In relativity, time does not cause processes to slow down: changes just are going slower. I notice this misunderstanding when trying to explain SR to absolute beginners. They think I will reveal some cause why 'time slows down'. They are disappointed when it turns out that the explanation is just a logical consequence of the relativity principle and the constancy of speed of light. They think I tricked them.

 

Like time, these are abstractions. The part that is very confusing to me is to claim that an abstraction doesn't exist unless you are measuring some effect that can be measured. It's an abstraction — we can define it any way we want to! And we define it to exist everywhere, because that makes physics work.

 

The abstraction 'time' does not exist in the same way as physical objects exist. And I would not exactly say that it makes physics work; it makes physics easy. (OK, comparatively easy...). But I know what you mean, and more or less agree.

Edited November 30, 2014 by Eise

[elfmotat]

The difference is that I always find a cause of the electric field: a charge, or an electromagnetic wave.

What in the world do field sources have to do with his point? If you insist on being pedantic, how about the Higgs field then? It's nonzero everywhere in space without sources.

[Eise]

Well, I am not pedantic enough to suggest that I understand the Higgs mechanism.

 

But only one thing: the Higgs particle is discovered, isn't it? That is independent access to the Higgs field, no? Do you expect we will find the 'chronon' one day, the elementary quantum of time?

[elfmotat]

Well, I am not pedantic enough to suggest that I understand the Higgs mechanism.

So is this a concession that your point is wrong?

 

But only one thing: the Higgs particle is discovered, isn't it? That is independent access to the Higgs field, no? Do you expect we will find the 'chronon' one day, the elementary quantum of time?

Swansont made a point: you can talk about fields having values at each point in space, even if no sources are around. Even if you get rid of the concept of sources altogether, nonzero vacuum solutions will typically be allowed for a given field. The point being that "fields" and "time" are useful abstractions we take to exist even when we aren't looking at them. (In fact, even if they are zero you could still argue that they are still "there.") For some unexplained reason you decided that the fact that some fields have sources is enough to do away with swansont's point. Rather than get bogged down by exactly why your objection makes no sense, I decided to cut through it by giving an example of a physical nonzero field without sources.

 

I quite clearly never said anything that would even hint at the chronon idea. Whether or not time is quantized is irrelevant to the point I was making, and I'm sure you know that as well as I.

[Eise]

So is this a concession that your point is wrong?

 

Not yet.

 

Swansont made a point: you can talk about fields having values at each point in space, even if no sources are around. Even if you get rid of the concept of sources altogether, nonzero vacuum solutions will typically be allowed for a given field. The point being that "fields" and "time" are useful abstractions we take to exist even when we aren't looking at them. (In fact, even if they are zero you could still argue that they are still "there.") For some unexplained reason you decided that the fact that some fields have sources is enough to do away with swansont's point. Rather than get bogged down by exactly why your objection makes no sense, I decided to cut through it by giving an example of a physical nonzero field without sources.

 

Now I am.

 

BUT: the point stays that there is some other access to e.g. the Higgs field. Was that not all the importance about finding the Higgs boson? Assuming that the Higgs particle would not have been found in any of the possible energy ranges, would that not have counted as falsification of the Higgs mechanism?

 

I quite clearly never said anything that would even hint at the chronon idea. Whether or not time is quantized is irrelevant to the point I was making, and I'm sure you know that as well as I.

 

No, no, I know. It was just a suggestion to make the difference between time and the Higgs field. There is no other access to time then through change. This rightly suggests that time is just an abstraction of that what really physically exists: change. And of course it is a very useful abstraction. We all use it daily, not just physicists.

[elfmotat]

I'm not really sure what you mean by "there is no access to time than through change." Because that sentence implies that these changes are happening over time. In other words, "there is no access to time than through change over time." That seems circular, and true by definition.

[Eise]

I'm not really sure what you mean by "there is no access to time than through change." Because that sentence implies that these changes are happening over time. In other words, "there is no access to time than through change over time." That seems circular, and true by definition.

 

I mean that apart from change we have no sources to know that time exists. I think that then we can strike time from our metaphysical vocabulary. What is the metaphysical difference between saying that 'time slows down near a black hole' and 'changes go slower near a black hole'? If you observe the surroundings of a black hole, what do you observe: slow time, or slow changes?

 

It has to do with the extreme generality of 'change'.

[swansont]

 

I mean that apart from change we have no sources to know that time exists. I think that then we can strike time from our metaphysical vocabulary. What is the metaphysical difference between saying that 'time slows down near a black hole' and 'changes go slower near a black hole'? If you observe the surroundings of a black hole, what do you observe: slow time, or slow changes?

 

It has to do with the extreme generality of 'change'.

 

 

Changes can be due to mechanical effects, but the slowing of time in relativity is not a mechanical effect.

[Eise]

Changes can be due to mechanical effects, but the slowing of time in relativity is not a mechanical effect.

 

I know:

In relativity, time does not cause processes to slow down: changes just are going slower. I notice this misunderstanding when trying to explain SR to absolute beginners. They think I will reveal some cause why 'time slows down'. They are disappointed when it turns out that the explanation is just a logical consequence of the relativity principle and the constancy of speed of light. They think I tricked them.

 

So what is the point?

[StringJunky]

 

I mean that apart from change we have no sources to know that time exists. .

Yes, we need something that changes regularly to measure time but it doesn't define time because it doesn't encompass all possible states like when a subject is doing nothing. Time is still passing for the subject even though it's apparently inactive, so you see, something changing is not sufficient. The real problem is trying to analyse and thus over-complicate something that is nothing more than a simple parameter.

[swansont]

 

So what is the point?

 

That the two are not equivalent.

And I would not exactly say that it makes physics work; it makes physics easy. (OK, comparatively easy...).

 

If time does not behave as described by relativity then you've lost Lorentz invariance. Physics as we know it literally does not work.

[elfmotat]

 

What is the metaphysical difference between saying that 'time slows down near a black hole' and 'changes go slower near a black hole'?

 

"Go slower" through what? You keep doing this - you're invoking the vocabulary of time in order to explain and define time. It's not helpful or enlightening. Essentially all you've done here is proclaim "change" as a synonym for "time."

 

 

If you observe the surroundings of a black hole, what do you observe: slow time, or slow changes?

 

Neither. For you time passes normally.

[Eise]

"Go slower" through what? You keep doing this - you're invoking the vocabulary of time in order to explain and define time. It's not helpful or enlightening. Essentially all you've done here is proclaim "change" as a synonym for "time."

Nearly, yes. The only problem is that time is not physical. Therefore there is no physical cause for the LT. The LT follow logically from the 2 postulates of the RT. No forces, no fields, potential, nothing.

 

 

 

If you observe the surroundings of a black hole, what do you observe: slow time, or slow changes?

Neither. For you time passes normally.

 

Your reading is in bad faith, you should know that. Of course I am observing the black hole from a big and safe distance. For me processes near the black hole are going slower.

That the two are not equivalent.

I know that, so ask me different: what is the relevance pro or contra my viewpoint?

 

If time does not behave asdescribed by relativity then you've lost Lorentz invariance. Physics as we know it literally does not work.

I think nothing of what I said changes anything in the LT. It only gives a different viewpoint on the concept of time: that it is a tool to describe processes.

 

Let's try it in another way. Classical physics believed that there was a kind of universal time and space. You only had to define the origin of your coordinate system, but lengths and durations were universal. RT did away with that. But instead of that, you define now that every inertial system has its own time and length. But again, isn't that an unnecessary metaphysical assumption? Why not stick to what we can observe: that lengths seem shorter, and durations longer. Why is it called length contraction, and not space contraction (OK, I know, it is only one dimension.) But shouldn't we say that we have 'duration dilatation' instead of 'time dilatation'? We see how clocks go slower, how all processes go slower. But we do not see time going slower.

 

I don't know if this parallel helps: if we change the clocks at the start of daylight saving time, what do we in fact do? Change the time? Or are we doing everything one hour earlier? Is the 'same time still flowing' as before?

 

But I agree that the point is not very important, but if somebody asks 'what is time?', then my answer would be still this: it is an abstraction of change. It is definitely not the other way round.

Edited December 1, 2014 by Eise

[elfmotat]

The only problem is that time is not physical.

 

Says who?

 

 

Therefore there is no physical cause for the LT. The LT follow logically from the 2 postulates of the RT. No forces, no fields, potential, nothing.

 

What are "LT" and "RT"? I don't see how any of what you said addresses any of what I said. All you've accomplished is a pedantic shift in vocabulary.

but if somebody asks 'what is time?', then my answer would be still this: it is an abstraction of change.

 

You're doing it again. How can there be change with no time? Your reasoning and your definitions are circular. Worse, they're conceptually meaningless.

[Strange]

From a single muon itself you will never be able to conclude that time has passed.

 

That is almost the point. Change is only a way we use to measure or quantify time; it is not time nor the cause of time. You can't tell that time passes, because there is no change. And yet, time passes for that muon and, after some time, it decays. If time is "an abstraction of change", then how is it possible for there to be a delay (Where there is no change) before the muon decays.

 

 

I was saying that people seem to care, as elfmotat says, about how many angels can dance on the head of a pin.

 

Or perhaps people care about "someone being wrong on the Internet" more than they care about angels.

"What do you want me to do? LEAVE? Then they'll keep being wrong."

[swansont]

 

I know that, so ask me different: what is the relevance pro or contra my viewpoint?

 

 

 

One is logical: All change requires time, but not the converse. Universal affirmatives can only be partially converted — only in some instances of time passing will you observe change.

You seem to be insisting that time only passes only if we observe change. And insisting is the entirety of the argument.

[Eise]

Says who?

 

I do. And gave an argument: there is no force, no field, no potential, nothing physical, i.e. no physical cause (no 'mechanism', as Swansont formulated it) for the Lorentz transformations.

 

What are "LT" and "RT"?

 

Lorentz Transformation and Relativity Theory.

 

I don't see how any of what you said addresses any of what I said. All you've accomplished is a pedantic shift in vocabulary.

 

I think that I know what you mean. You say it is impossible to define change without using the concept of time. That maybe true. But since when can we conclude from a concept at the real existence independent of the concept? For something to exist physically, in my opinion, means that it causes something else. Time doesn't cause anything. You seem to postulate a kind of 'sea of time' in which everything exists. But on the other side everything has its own time, depending on the observer seeing it.

 

You're doing it again. How can there be change with no time? Your reasoning and your definitions are circular. Worse, they're conceptually meaningless.

 

Well, if you think that events occurring in time have the same physical status as time, be my guest.

 

That is almost the point. Change is only a way we use to measure or quantify time; it is not time nor the cause of time. You can't tell that time passes, because there is no change. And yet, time passes for that muon and, after some time, it decays. If time is "an abstraction of change", then how is it possible for there to be a delay (Where there is no change) before the muon decays.

 

Yes, I can tell that time passes: here, have my clock. Look at it, and see where the pointer is when the muon decays.

 

Or perhaps people care about "someone being wrong on the Internet" more than they care about angels.

 

"What do you want me to do? LEAVE? Then they'll keep being wrong."

I'll give you my mirror too.

One is logical: All change requires time, but not the converse. Universal affirmatives can only be partially converted — only in some instances of time passing will you observe change.

 

All change requires time, yes, as a concept, as an abstraction. You did call time an abstraction. Of what?

 

You seem to be insisting that time only passes only if we observe change. And insisting is the entirety of the argument.

 

That puts me in a paradox...

[swansont]

Time doesn't cause anything.

 

Neither does length, but that doesn't seem to bother anyone anywhere close to level that time does.

[elfmotat]

I do. And gave an argument: there is no force, no field, no potential, nothing physical, i.e. no physical cause (no 'mechanism', as Swansont formulated it) for the Lorentz transformations.

 

First of all, how do you know that's true? Lorentz symmetry may very well be an emergent symmetry that appears at large scales. It might be a fundamental symmetry, it might not, but you don't get to just make up an answer before we are able to do the tests. As of now it appears to be fundamental, but that might very well change.

 

Second: even if Lorentz symmetry is fundamental, how does that show that "time is not physical"? I don't see the connection. And how are you defining physical? The usual definitions include something to the effect of "a measurable quantity." Time is a measurable quantity, so I would certainly define it as "physical."

 

I think that I know what you mean. You say it is impossible to define change without using the concept of time.

 

I don't say it's impossible, just that I don't know how to do it.** And apparently you don't either, because you keep giving circular definitions.

 

**(Except, perhaps, by adding more time dimensions. But that certainly doesn't solve any problems in terms of defining what time is.)

 

But since when can we conclude from a concept at the real existence independent of the concept?

 

That seems like a vague philosophical question rather than a physical one.

 

For something to exist physically, in my opinion, means that it causes something else.

 

Well, that's just an unorthodox definition of the word "physical." It's generally a good idea to keep words' commonly understood definitions, otherwise you're going to be constantly redefining them and confusing your audience.

 

Time doesn't cause anything.

 

Obviously. Causality is defined by a relationship in time. That would be circular.

 

You seem to postulate a kind of 'sea of time' in which everything exists. But on the other side everything has its own time, depending on the observer seeing it.

 

I'm not postulating anything. The only thing I've said in terms of time's definition is: "time is what's measured by clocks."

 

Well, if you think that events occurring in time have the same physical status as time, be my guest.

 

You're making up some kind of weird hierarchy where some things are "more" physical than others. By any useful definition a thing has got to be either physical or not physical.

Edited December 1, 2014 by elfmotat

[Eise]

Neither does length, but that doesn't seem to bother anyone anywhere close to level that time does.

 

Hmmm. That is a good point.

 

But we must be careful: length is the comparison with other objects. So there is a parallel with time, which is a comparison with one change with another, standardised change.

 

So, no. Length in itself is not a physical object. It also causes nothing. It are objects with certain lengths that causes something.

 

The reason that time bothers so more seems to me is the fact that where we can freely move in 3 dimensions, time seems to have one single direction.

[Strange]

Yes, I can tell that time passes: here, have my clock. Look at it, and see where the pointer is when the muon decays.

 

So muons know when to decay by looking at your clock. Got it.

The reason that time bothers so more seems to me is the fact that where we can freely move in 3 dimensions, time seems to have one single direction.

 

I don't really know why that bothers you so much that you have to invent other differences between time (as a temporal distance) and length (as a spatial distance).

Edited December 1, 2014 by Strange

[elfmotat]

The reason that time bothers so more seems to me is the fact that where we can freely move in 3 dimensions, time seems to have one single direction.

 

However there are physical scenarios where exactly the opposite is true. Past the event horizon of a black hole, the radial coordinate becomes timelike and the time component becomes spacelike. In other words, you can't stop getting closer to r=0 anymore than you can stop aging. Weird stuff happens with time too: you can quite literally see (as long as you're looking away from the singularity) events from both the past and the future. For example, if I jumped into a black hole, fell a distance of ~1 light-minute, then you jumped in after me, I would be able to see you from both one minute in the past and one minute in the future.