Is Time Real? Proving Its Existence

[bobc2]

We have the notion of time because we can mentaly order events by their appearance.

Probably the only thing that creates the notion of time is causality, therefore a theory that doesn't involve time might be also non-causal. Anyway, if time didn't existed wouldn't all just happen at once?

With the block universe it does all happen at once. That's why Barbour sees no need for time.

 

[mathal]

We have the notion of time because we can mentaly order events by their appearance.

Probably the only thing that creates the notion of time is causality, therefore a theory that doesn't involve time might be also non-causal. Anyway, if time didn't existed wouldn't all just happen at once?

The concept of a block universe puts time into a purely dimensional form. From the 'beginning' of 'time' on the universe is one object. We are part of the object. We go through our space time path seeing ourselves as the mover and shaker of our life but equally we are just the moved and shaken. No matter what you do, it is what you are doing and equally what you were always going to do. (If this is a block universe)
The delayed choice experiments of John Wheeler demonstrate that causality is not as neat and tidy as we always thought it was. Actions in the 'future' can 'alter' actions in the 'past' (WRT photons in the experiments). From a block universe perspective (an overview if you like) the potential paths of photons involves each entire path including where everything 'will' be 'when' the photon gets there (if it follows this particular path). It is where things 'will' be that governs the photon's probabilistic weight for each path.
mathal

 

[atomthick]

With the block universe it does all happen at once. That's why Barbour sees no need for time.

I understand but unfortunately this is not important to us, it would be important to a 4 dimensional being. We are 3 dimensional beings an therefore all is not just happening at once otherwise I would have responded at the same time you have posted your answer :)

 

[Naty1]

Was it Richard Feynman who said

"Time is what keeps everything from happening at once"..

??

 

[nitsuj]

The concept of a block universe puts time into a purely dimensional form. From the 'beginning' of 'time' on the universe is one object. We are part of the object. We go through our space time path seeing ourselves as the mover and shaker of our life but equally we are just the moved and shaken. No matter what you do, it is what you are doing and equally what you were always going to do. (If this is a block universe)
The delayed choice experiments of John Wheeler demonstrate that causality is not as neat and tidy as we always thought it was. Actions in the 'future' can 'alter' actions in the 'past' (WRT photons in the experiments). From a block universe perspective (an overview if you like) the potential paths of photons involves each entire path including where everything 'will' be 'when' the photon gets there (if it follows this particular path). It is where things 'will' be that governs the photon's probabilistic weight for each path.
mathal

Good comment,
however I disagree that a block universe and freewill of biology are mutualy exclusive. I like the perspective that knits time into distance.

electro-magnetic energy hardly seems to share the constraints of matter.

 

[bobc2]

I understand but unfortunately this is not important to us, it would be important to a 4 dimensional being. We are 3 dimensional beings an therefore all is not just happening at once otherwise I would have responded at the same time you have posted your answer :)

It is not clear that we are strictly 3D beings. In the block universe model our structure is 4D. The 3D experience could be related to some aspect of consciousness that includes an apparent advancing along the world line at light speed. You can compute the expected length of the world line by multiplying the life expectancy by the speed of light.

Many physicists are interested in developing an objective world view--not constrained by subjective aspects of experience.

 

[mathal]

Good comment,
however I disagree that a block universe and freewill of biology are mutualy exclusive. I like the perspective that knits time into distance.

electro-magnetic energy hardly seems to share the constraints of matter.

My opinion is that we have free will, in that we can never have the block universe overview of how things will turn out.
As with all information of a quantum nature we can never get a 3-d full color picture of what is happening. We can only elicit one bit of information from each photon and then put this together with other bits from other photons that are proscribed to the particular scenario of an experiment to get a range of results that tell us something about this very restricted set of circumstances.
IOW, as I said in my first post, the block universe may be an accurate picture of the universe but it is a picture we can never fully see.

"Keep on keepin' on" -Richard Farina I think. a good song


mathal

 

[bobc2]

My opinion is that we have free will, in that we can never have the block universe overview of how things will turn out.

You seem to be implying that free will just depends on whether you know the future rather than whether the future is already fixed.

As with all information of a quantum nature we can never get a 3-d full color picture of what is happening. We can only elicit one bit of information from each photon and then put this together with other bits from other photons that are proscribed to the particular scenario of an experiment to get a range of results that tell us something about this very restricted set of circumstances.

Most of our observations involve millions or billions of photons and other particles interacting in a more global fashion presenting classical phenomena leading to models that predict results in most everyday situations. Heisenberg's uncertainty principle, Schroedinger's probability waves, E = hf, and other quantum physics concepts refine the models for the microscopic domain. All of these models seem to be consistent with a block universe model, although most block universe literature do not specifically address QM or Quantum Field Theory issues.

IOW, as I said in my first post, the block universe may be an accurate picture of the universe but it is a picture we can never fully see.

In the block universe model we observe a continuous sequence of 3-D cross-sections of the 4-D universe. Observers having different velocities relative to each other experience different 3-D cross-section views of the same 4-D universe. If a long rope was snaked along a path extending 20 miles, you could walk along it for 20 miles and then feel like you have observed the rope sufficiently to provide an accurate description to anyone interested. Perhaps you could do something similar for a bundle of filaments that extend along a world line for 10^13 miles or so (you have the advantage of moving along the bundle--headed in the 4th dimension--at the speed of light).

The special relativity result in which different observers experience a time sequence of different cross-sections of the 4-D universe of course motivates the block universe model. No one seems to have presented an alternative that provides a logical explanation for this special relativity result.

You can introduce multiple universes (or parallel universes, etc.), but that seems to make the model quite a bit more complicated, introducing a host of mind boggling issues, and it is not obvious that you've really ridden yourself of block universe. And such models are often very contrived.

By the way, I personally don't like the block universe model for subjective reasons, but see the implications of multiple 3-D cross-sections as one of the great mysteries of physics (on a par with the double slit experiment).

 

[GrayGhost]

Like DaleSpam I found Julian Barbour's "The End of Time" to be a letdown ...

One of his major concepts, referred to as "Platonia", draws on the extension of the familiar configuration space of physics to four dimensions. Not a bad idea to think about, but again, I don't see how that fundamentally eliminates time. Richard Feynman's work with 4-D QM of course preceded this idea.

I would be very surprised of J Barbour was attempting to eliminate time w/o replacing it with something more fundamental, something which would have no impact on our perception of time but rather only its meaning.

J Barbour must replace time with the transitioning thru his landscape of Platonia. So I agree with you, that our notion of time must remain no matter how he attempts to define its mechanism. He may eliminate time as we define it, but it must be replaced with something that serves the same purpose. My assumption is that he believes a redefinition of TIME is required to unify the all of physics. I've read up on Julian before, but I haven't read his book. Sounds like you would not recommend it. He's a rather reputable physicist from what I've heard, yes?

GrayGhost

 

[Phrak]

A lot of people here are having problems with a derivate of the word "is". Bill Clinton went to great lengths to explain what is is. So why is it that is, is so difficult? ...Or, ahem, why exists it that exists, exists so difficult? Ahem.

 

[bobc2]

I would be very surprised of J Barbour was attempting to eliminate time w/o replacing it with something more fundamental, something which would have no impact on our perception of time but rather only its meaning.

J Barbour must replace time with the transitioning thru his landscape of Platonia. So I agree with you, that our notion of time must remain no matter how he attempts to define its mechanism. He may eliminate time as we define it, but it must be replaced with something that serves the same purpose. My assumption is that he believes a redefinition of TIME is required to unify the all of physics. I've read up on Julian before, but I haven't read his book. Sounds like you would not recommend it. He's a rather reputable physicist from what I've heard, yes?

GrayGhost

You make a really good point, GrayGhost. I think you may have it right on the money here. Excellent analysis -- particularly for a guy who hasn't had the chance to read the book. I first started reading it a little at a time sitting in a chair at Border's before buying the book.

Julian Barbour is of course a first rate physicist (as his buddy Lee Smolin). I certainly have a lot of respect for him. Although I was let down, much of the book was very interesting and I would recommend it. I guess I had so much expectation, thinking that finally we have a book that will clarify all essential aspects of time--and I agree with DaleSpam that it falls short of those expectations.

But, I'd love to sit down and talk about time with him and Paul Davies for a few hours.

 

[Dale]

He may eliminate time as we define it, but it must be replaced with something that serves the same purpose.

This is correct also for his technical papers which I have read. It is a "rose by any other name" approach, IMO. He makes great efforts to verbally emphasize the difference of his concept, but then he sticks it in the same places in all of the equations which eliminates the differences mathematically.

 

[mathal]

You seem to be implying that free will just depends on whether you know the future rather than whether the future is already fixed.



Most of our observations involve millions or billions of photons and other particles interacting in a more global fashion presenting classical phenomena leading to models that predict results in most everyday situations. Heisenberg's uncertainty principle, Schroedinger's probability waves, E = hf, and other quantum physics concepts refine the models for the microscopic domain. All of these models seem to be consistent with a block universe model, although most block universe literature do not specifically address QM or Quantum Field Theory issues.



In the block universe model we observe a continuous sequence of 3-D cross-sections of the 4-D universe. Observers having different velocities relative to each other experience different 3-D cross-section views of the same 4-D universe. If a long rope was snaked along a path extending 20 miles, you could walk along it for 20 miles and then feel like you have observed the rope sufficiently to provide an accurate description to anyone interested. Perhaps you could do something similar for a bundle of filaments that extend along a world line for 10^13 miles or so (you have the advantage of moving along the bundle--headed in the 4th dimension--at the speed of light).

The special relativity result in which different observers experience a time sequence of different cross-sections of the 4-D universe of course motivates the block universe model. No one seems to have presented an alternative that provides a logical explanation for this special relativity result.

You can introduce multiple universes (or parallel universes, etc.), but that seems to make the model quite a bit more complicated, introducing a host of mind boggling issues, and it is not obvious that you've really ridden yourself of block universe. And such models are often very contrived.

By the way, I personally don't like the block universe model for subjective reasons, but see the implications of multiple 3-D cross-sections as one of the great mysteries of physics (on a par with the double slit experiment).

I interpret 'know the future' and 'future is already fixed' as the same concept. If you 'know' the future that future would necessarily be fixed unless you feel that 'knowing' the future allows you to change it to a different 'future'.

Adding to what nitsuj said in his previous post it seems unlikely a delayed choice experiment involving electrons (or any other massive particle) could be performed measurably altering the future paths of the electrons as was done with photons in the original experiments.

mathal

 

[bobc2]

This is correct also for his technical papers which I have read. It is a "rose by any other name" approach, IMO.

Good way to put it.

He makes great efforts to verbally emphasize the difference of his concept, but then he sticks it in the same places in all of the equations which eliminates the differences mathematically.

DaleSpam, I haven't seen his technical papers. Do you have any references? Thanks.

 

[bobc2]

I interpret 'know the future' and 'future is already fixed' as the same concept. If you 'know' the future that future would necessarily be fixed unless you feel that 'knowing' the future allows you to change it to a different 'future'.

What if no one is there to know the future (say, for the first 3 to 4 billion years after the big bang)? The block universe model would of course have it all fixed without anyone to know it. God knew it, so maybe that satisfies your concept (sorry, I always try to leave theology out of my posts).

Adding to what nitsuj said in his previous post it seems unlikely a delayed choice experiment involving electrons (or any other massive particle) could be performed measurably altering the future paths of the electrons as was done with photons in the original experiments.

mathal

My memory is not always trustworthy, but I think the experiment has been performed with massive particles.

 

[nitsuj]

Adding to what nitsuj said in his previous post it seems unlikely a delayed choice experiment involving electrons (or any other massive particle) could be performed measurably altering the future paths of the electrons as was done with photons in the original experiments.

mathal

This area of physics starts to go beyond the general knowledge I have. But, electrons do share characteristics of pure EM. (Are electrons considered matter?)

A double slit experiment could be done with electrons, however as you pointed out they are relatively heavy (momentous? lol) compared to photons. I think it is mass/momentum that reduces the effect of the uncertainty principle, which I am guessing is the phenomenon the "Delayed Choice Experiment" exposes.

Your use of the word "measurably" hints to me you know this.

 

[GrayGhost]

This is correct also for his (Julian Barbour's) technical papers which I have read. It is a "rose by any other name" approach, IMO. He makes great efforts to verbally emphasize the difference of his concept, but then he sticks it in the same places in all of the equations which eliminates the differences mathematically.

String theory seems a similar approach. Define an underlying mechanism that cannot be proven, one which upholds currently accepted physics, model it mathematically, and then hope it eventually makes a successful prediction that current physics does not. I eagerly await :)

GrayGhost

 

[GrayGhost]

But, I'd love to sit down and talk about time with him (J Barbour) and Paul Davies for a few hours.

Indeed, me too. Then we could chat relativity for awhile :)

GrayGhost

 

[Selraybob]

That's a good angle ZapperZ. Perhaps the same as saying "Time exists no more or less then a rising sun or ticking clock.

The difference is, we started with the rising sun and the moons and seasons and then someone along the way came up and decided there was this thing called Time. We seem to be missing the paradigm shift. Change happened, then we found Time. Then we found some good counters that repeated pretty well and didn't change that much compared to other counters, and we called those counters 'timepieces.' But they're just counters.

I don't know why this topic keeps popping up like a zit.

Because there are too many people out there with answers that don't make a lot of sense and lots of people want the answers to make sense.

Think of an exposed cliff with all its geological layers on top of each other. No periodic process necessary to explain it, just one way direction of gravity demonstrating the existence of time.

Exposed cliffs are cool, and we got some in Missouri with all sorts of layers along the river. But that's just about things changing. One thing happens and then another and then an ice age comes along or two and animals die and turn to oil. That's not Time. That's stuff changing.

Any concept of 'Time' that people have comes from comparing something that's changing, usually something regular, to something else. Like -- I had a big belly and then the sun came and set 120 times and I dieted and I have a small belly. Usually we just say something like, Four months ago I was a tub of goo (which I'm not anymore). But it's all about comparing changes.

 

[ZealScience]

What is meant by your time?

What my understanding time is just a measurement used to study properties of our universe.

It is closely related to measurement of space. What is the purpose of inquiring the existence of certain measurement?

 

[nitsuj]

The difference is, we started with the rising sun and the moons and seasons and then someone along the way came up and decided there was this thing called Time. We seem to be missing the paradigm shift. Change happened, then we found Time. Then we found some good counters that repeated pretty well and didn't change that much compared to other counters, and we called those counters 'timepieces.' But they're just counters.



Because there are too many people out there with answers that don't make a lot of sense and lots of people want the answers to make sense.



Exposed cliffs are cool, and we got some in Missouri with all sorts of layers along the river. But that's just about things changing. One thing happens and then another and then an ice age comes along or two and animals die and turn to oil. That's not Time. That's stuff changing.

Any concept of 'Time' that people have comes from comparing something that's changing, usually something regular, to something else. Like -- I had a big belly and then the sun came and set 120 times and I dieted and I have a small belly. Usually we just say something like, Four months ago I was a tub of goo (which I'm not anymore). But it's all about comparing changes.

I think I get what your saying.

I feel that conscious perception of time is derived from comparison. The variance of change noted from comparison is derived as "time". That's a bold statement on the surface but is just semantics.

 

[mathal]

This area of physics starts to go beyond the general knowledge I have. But, electrons do share characteristics of pure EM. (Are electrons considered matter?)

A double slit experiment could be done with electrons, however as you pointed out they are relatively heavy (momentous? lol) compared to photons. I think it is mass/momentum that reduces the effect of the uncertainty principle, which I am guessing is the phenomenon the "Delayed Choice Experiment" exposes.

Your use of the word "measurably" hints to me you know this.

Yes. But I wouldn't say 'reduces'. Massless particles have an entirely different relationship with time than electrons and other mass-like particles. The photon is necessarily more
block universe-like in it's 'appearance' than an electron.
The path of an electron is 'restricted' by it's mass to a range of values that fall off exponentially at the extreme edges of it's potential to be there then. This seemingly haphazard quality at any point in time in the electron's path is analagous to the entire
'history' of any particular photon from it's inception to it's reception. By 'history' I am including all possible 'histories' the photon could have taken.

mathal

 

[mathal]

My memory is not always trustworthy, but I think the experiment has been performed with massive particles.

My memory too is failing, but I have no recollection of delayed choice experiments involving mass particles.

mathal

 

[Goolds]

We have the notion of time because we can mentaly order events by their appearance.

Probably the only thing that creates the notion of time is causality, therefore a theory that doesn't involve time might be also non-causal. Anyway, if time didn't existed wouldn't all just happen at once?

We have a basic concept of time (a passage between two events). I believe it is a result of human perception. The best way to describe a system and it's changing values is to compare the starting state to the end state. Hence, we percieve this change as time.
In response to your second point: I have already explained my opinion on the creation of the notion of time. I would say, therefore, that a theory which excludes time would be inherently flawed. If time didnt 'exist' then nothing would happen, beacuse there would be no chage in the state of the universe.

 

[ZapperZ]

Because there are too many people out there with answers that don't make a lot of sense and lots of people want the answers to make sense.

That's a very weak excuse. "making sense" has never been a criteria to ensure that something is valid. A lot of things do not makes sense AT FIRST, and then makes sense later after you learn a bit more! So just because something doesn't make sense doesn't make it any less valid.

Phenomena that have been characterized by broken time reversal symmetry are strong evidence for an inherent and intrinsic properties of time. Saying that it is nothing more than a "counter" implies that you can't tell the difference between a quality and the SCALE used to quantify that quality. One could argue the same thing with space, charge, mass, etc. So why pick on "time"? "Space" is also a CHANGE in something, which is displacement.

Zz.

 

[Dale]

Good way to put it.

DaleSpam, I haven't seen his technical papers. Do you have any references? .

Sorry about the delay. Here is his main site for his technical papers:
http://www.platonia.com/papers.html

I have not read all of them, only "Machs principle and the structure of dynamical theories", "Leibnizean time, Machian dynamics, and quantum gravity", and his fqxi essay. I didn't find any of them convincing, and he actually soured me on Machs principle too.

 

[Dale]

But that's just about things changing. One thing happens and then another and then an ice age comes along or two and animals die and turn to oil. That's not Time. That's stuff changing.

And how could stuff change without time?

Mathematically change is given by a derivative, e.g. df/dt where f is the thing changing and t is the thing with respect to which it changes. So conceptually the changes you refer to all presuppose time.

 

[Selraybob]

That's a bold statement on the surface but is just semantics.

I looked up 'semantics' just to make sure I knew what you were saying. And what I'm figuring is that all of this discussion on the topic is semantics. Every idea is about the definition and meaning of the word Time and how it fits with all of the science. So I don't understand what you were getting at.

That's a very weak excuse.

I know you're a lot smarter than me and way more educated, so that clearly means something. But I was only talking about your question about why this topic keeps coming up. No one should need an excuse to bring something up on physicsforums. Of maybe I'm wrong on that. I don't know. But dang, if scientists didn't question what everyone thinks is the absolute right way, we'd probably be still drilling holes in people's heads to get the demons out.

A lot of things do not makes sense AT FIRST, and then makes sense later after you learn a bit more!

Don't worry, Zapper, I'm still reading. And I'm going to do some reading on broken time-reversal symmetry, to see if that isn't just about something changing back when something else is changing forward. But I don't know yet, so I'll look.

Phenomena that have been characterized by broken time reversal symmetry are strong evidence for an inherent and intrinsic properties of time.

Like I said, I'll do some reading.

Saying that it is nothing more than a "counter" implies that you can't tell the difference between a quality and the SCALE used to quantify that quality.

I'm not picking on Time, but I think I'm saying that Time isn't a quality. And if you do want to start counting some change that happens over and over, the scale's going to be different. And it can be different depending on what you're counting. But what I'm figuring is that you're set that Time is some quality. So I think we're stuck disagreeing.

One could argue the same thing with space, charge, mass, etc. So why pick on "time"? "Space" is also a CHANGE in something, which is displacement.

Zz.

I looked up Displacement, and from first reading, that seems to be a count of space. Space isn't the change in displacement.

But then, you're smarter than me, like I said, and more educated I'm sure, so I'll keep reading and disagreeing until someone comes up with something that doesn't just come back to Time being all about the count of changes.

 

[GrayGhost]

And how could stuff change without time?

Well, that's what Julian Barbour (and others) are spending much of their life trying to explain. So far, no bananas :)

The goal (of some) is to define a 4d (or more) continuum already laid out start to end, then develop a description for the sequencing within it that gives rise to our notion of time in the way we experience it. Basically, to find an alternative way to describe change which does not require time, but gives rise to our existing concept of it. A tall order. I think it's a worthy quest, given it is not expected to change physics, but rather hopefully extend physics.

GrayGhost

 

[Dale]

Well, that's what Julian Barbour (and others) are spending much of their life trying to explain. So far, no bananas :)

The goal (of some) is to define a 4d (or more) continuum already laid out start to end, then develop a description for the sequencing within it that gives rise to our notion of time in the way we experience it. Basically, to find an alternative way to describe change which does not require time, but gives rise to our existing concept of it. A tall order. I think it's a worthy quest, given it is not expected to change physics, but rather hopefully extend physics.

I think that the problem for Barbour et al. is that physics is written in terms of differential equations wrt time. While you can cast it in terms of a 4d continuum, as long as you are differentiating there is something you are differentiating wrt. That something includes time. I think that they will need to eliminate differential equations from physics in order to accomplish their goal. A very tall order, as you say.

 

[stevenb]

Does time really Exist?

I'll tell you later.

 

[atomthick]

I think that the problem for Barbour et al. is that physics is written in terms of differential equations wrt time. While you can cast it in terms of a 4d continuum, as long as you are differentiating there is something you are differentiating wrt. That something includes time. I think that they will need to eliminate differential equations from physics in order to accomplish their goal. A very tall order, as you say.

Probably this will never be done. Differential laws (equations) bring much more value than the removal of time. Unlike integral laws (equations), differential laws give us the possibility to compute the next state of a system given it's previous states, which what is ultimate desire in physics.

 

[GrayGhost]

I think that the problem for Barbour et al. is that physics is written in terms of differential equations wrt time. While you can cast it in terms of a 4d continuum, as long as you are differentiating there is something you are differentiating wrt. That something includes time. I think that they will need to eliminate differential equations from physics in order to accomplish their goal. A very tall order, as you say.

Well, when you put it that way, it does seem unlikely. I suppose I should break down and look thru that book of his.

Even when attempting to cast differential equations in terms of a 4d continuum, there is still this "other thing" we know to be time. It's a natural contiguous progression of everything. We all assume it has a rate, and that it is steady. Minkowski's model suggests that the rate of proper time equates to the rate of light. Let's say hypothetically, that the rate of proper time was to change all of a sudden. OK, so imagine a Minkowski worldline diagram ... the stationary observer's horizontal line-of-simultaneity (LOS) advancing vertically, with other slanted worldlines here and there. No matter how much faster (or slower) we advance this LOS, nothing changes geometrically. And so how could we ever discern a change in time's rate, even if it did? This is analogous to saying ... how could we ever discern a change in light's speed? ... which reminds me of your other post where you addressed this mathematically. One reason many ask ... is time what we assume it to be?

I'm also wondering ... as one steps thru J Barbour's 4-scape of Platonia, how does he prevent a steppage into the past? That is, how does his Platonia prevent a reversal along a worldline?

GrayGhost

 

[nitsuj]

I looked up 'semantics' just to make sure I knew what you were saying. And what I'm figuring is that all of this discussion on the topic is semantics. Every idea is about the definition and meaning of the word Time and how it fits with all of the science. So I don't understand what you were getting at.

Without a doubt there is a concise/strict definition for time in physics, and I doubt that it is what I had said. However, what I said is true, and is from the context of perception of time, not physics.

That was what I was "getting at" using the word semantics.

 

[tennismike22]

Existence implies taking up space in our universe. Then simply put...NO.