Defining Time: Our Everyday Mystery

[jeebs]

I recently realized that we use this concept constantly but I have absolutely no idea how I would answer this. Never in any school physics lesson or university lecture I've attended has anyone even mentioned this. It's just sort of taken for granted because we all have experience of it passing. This a pretty open ended question, just thought I'd throw it out there. So, how would you define this quantity we call time?

 

[Edi]

Tim is change/ movement. If there is no movement/ change in a system (and I mean at the deepest possible level), then practically, there is no time flowing. And it works backwards - no time= no change/ movement.
Jap.. this is the best I have :P

And yes - this is a very good and fundamental question that is bugging me for some time now..

 

[pallidin]

I would agree. "Time" is just a concept that involves "change"
Without change there can be no time.

However, one has to be a little careful with this.
That is, just because something may not change internally does not mean that it doesn't change with respect to its external environment.
Movement of an internally, non-changing object through space is an example.

In short, "time" is a measurement of change, specific on perspective frame.

 

[jeebs]

that's kind of unsatisfying I think. I mean, we could be sat in an enclosed room with no windows just staring at a wall, and be unable to detect any movement of anything, but we'd have no reason to suppose that time had stopped just because we couldn't see any of its effects. we could assume the world outside was still going about its business. am I missing the point here?

 

[khemist]

You see the effect of time because you are still living. The fact your heart is beating is an indicator of time.

Time is obviously relative, however, and people might not agree on the simultaneity of a specific event.

 

[bp_psy]

My favorite textbook definition for time is :"If the internal state of a particle or a localized object is changing, its successive states define a continuum,which we call the time of that particle"
Classical Mechanics, Volume 1 A. Desloge

Whether that is enough for you is another issue.

 

[Arsenic&Lace]

"Time is what happens when nothing else does." --Feynman Lectures

 

[James A. Putnam]

The difficulty with time, I think, has to do with perception. We receive data from photons that consist of changes of velocity with respect to time. Moving down theoretically, it means that changes of distance with respect to time are not constant, they vary. I know that you know this. My point is that if we return to considering the data, and, recognize that we use it to form a visualization of what may be happening in the outside world, then visualizing distance and not visualizing time is a matter of interpretation. Time is not less real than is distance. Distance does not gain credibility leaving time to be an effect just because one is visualized and the other is not. (Gravity is not visualized either).

The cause of changes in distance are not known. The cause of time is not known. That is because, we do not know what cause is. Theoretical physics is necessary in order to substitute imagined causes for that which we cannot know. We can imagine something that we choose to generically call force to account for changes of position of an object; but, we cannot imagine something that causes time to move on. Force causes acceleration; but, that same imagined cause cannot cause time to accelerate. It is rather inferred from theory. Inferring is not satisfactory for explaing what time is. So, without an obvious clear answer, it is sometimes put forward that the motion of objects causes time. In other words, time is an effect.

Relativity theory seems to support this idea, so, it continues to be put forward. My point to this is that everything we observe is an effect. We never observe cause. Therefore, that which we observe objects to do may relate to time, but, cannot be shown to be the cause of time. The 't' in physics equations is always about a non-constant standard of cyclic activity. When that 't' varies it does not tell us what time is doing, it tells us what that cyclic activity is doing. If we discovered a measure of duration in time that was constant everywhere, at all time, in the universe, then we would know that time is not an effect of motion. However, that discovery would also necessitate doing away with Relativity Theory alltogether. Perhaps the most interesting possibility of an existing natural constant standard of time is that as a universal constant it should already appear in today's theories. Its interpretation may be incorrect; but, it should be already recognized by us under a different name.

Everything we learn comes from observing patterns in changes of velocity. There are two clearly fundamental properties that we cannot put into containers. We cannot isolate them in order to experiment on them. Neither one experiences changes of velocity. Those two properties are space and time. Since we cannot push or pull either of them, we cannot make measurements of rates of change for either. We only experiment on objects. We only know what it is that objects do. Objects are always things that exist in space and during time. Objects cause other objects to change that which they were doing. Objects causing effects that we observe to occur to other objects do not tell us about either space or time.

James

 

[PhysDrew]

The simplest of question yet one of the most elusive!
Wasn't the question of time's uni-directionality one of the causes for physicist's to attempt to formulate a theory of everything? For in order to examine the nature of time, one must go back to the beginning. And once physicists mathematically examined the beginning with the two main theories of the time, the maths turned out to be nonsense.
And i don't think that the implication that if an entity is living, time is passing. A virus is considered 'dead' outside of a host. Surely time doesn't stop for the virus? How would it's metabolism kick in once it found its way into a host? How would it know, if time ceased for the virus?

 

[71STARS]

Time is a measure of our Planet's 24 hour segment. Other planets and star system will naturally differ. We have even calculated light-years based on our conception of the Speed of Light, but it may differ within other systems. Bottom Line: Time is a measure.

 

[Oldfart]

I think of time as a sort of ether which is repelleded by mass, energy. and by objects moving through space. Thus it might be a particle, and maybe is represented by what we call dark energy. Figuring this out is way outside my pay grade...

OF

 

[Pilot7]

The question is the deepest (physical) question I know. I spend several years on this one (basically as the guiding question of a masters and then PhD thesis in philosophy and the philosophy of physics).

Here is my favourite answer:

Time is God's way of keeping everything from happening at once...

Okay, and a little more explicative:

Time in physics actually has somewhere on the order of 14 flavours. For example in quantum physics, there are at least 10 different and even inconsistent definitions of time. Relativity theory, Quantum Gravity, etc. all do weird things with time. Coming back to classical physics, even here it has several variants. There is time the measure used in a laboratory and time the theoretical metric used to describe the evolution of classical systems. And there are some ways it has been used to talk about entropy and even be defined in terms of entropy (thinking to Prigagine for example).

On thing in all of this to keep in mind. All notions of “flow” are strictly non-physical. In fact, this sort of “time” has been traditionally called “psychological time”. Now what I will add is that if you think this through, you will see that there is still a pretty serious mystery behind all this: What is flow? This was the question I was addressing in the context of my graduate work—very subtle stuff. There is not theory in physics that even hints at what this could conceivably be, with the possible exception of certain variations of quantum gravity that treat the wave collapse as a genuinely “real” or ontological phenomenon. Even then, it requires something of a conceptual dance to tease out the semantic features that would make flow flow (pun intended).

If anyone is interested, write me and I will forward a copy of one of my papers that has a fair amount of background of all this stuff in it. (In other words, even if you don't like my approach to the problem, you get a taste of who else has said what about the issue).

 

[GoliathX]

I have a theory which can explain time, dark matter, dark energy and the expansion of space easily.

First, I do not have a background in mathematics or physics. I was pursuing a pre-engineering degree before I got derailed by life stuff and will not be going back anytime soon.

Second, how can I go about getting taken seriously? Where is a place that I could honestly begin?

This is an honest inquiry and no I will not share this information publicly.

Thank you.

 

[Athletico]

I have a theory which can explain time, dark matter, dark energy and the expansion of space easily.

First, I do not have a background in mathematics or physics. I was pursuing a pre-engineering degree before I got derailed by life stuff and will not be going back anytime soon.

Second, how can I go about getting taken seriously? Where is a place that I could honestly begin?

This is an honest inquiry and no I will not share this information publicly.

Thank you.

I'd post your thoughts here. People on PF are pretty open-minded for the most part. Just be prepared for criticism - especially if your views are highly speculative and go against the grain of accepted theories.

 

[DrGreg]

I have a theory which can explain time, dark matter, dark energy and the expansion of space easily.

First, I do not have a background in mathematics or physics. I was pursuing a pre-engineering degree before I got derailed by life stuff and will not be going back anytime soon.

Second, how can I go about getting taken seriously? Where is a place that I could honestly begin?

This is an honest inquiry and no I will not share this information publicly.

Thank you.

I'd post your thoughts here. People on PF are pretty open-minded for the most part. Just be prepared for criticism - especially if your views are highly speculative and go against the grain of accepted theories.

No, if your views are highly speculative and go against the grain of accepted theories, then it's against the rules of this forum to post your thoughts here:

Overly Speculative Posts:
One of the main goals of PF is to help students learn the current status of physics as practiced by the scientific community; accordingly, Physicsforums.com strives to maintain high standards of academic integrity. There are many open questions in physics, and we welcome discussion on those subjects provided the discussion remains intellectually sound. It is against our Posting Guidelines to discuss, in most of the PF forums or in blogs, new or non-mainstream theories or ideas that have not been published in professional peer-reviewed journals or are not part of current professional mainstream scientific discussion. Personal theories/Independent Research may be submitted to our Independent Research Forum, provided they meet our https://www.physicsforums.com/showthread.php?t=82301; Personal theories posted elsewhere will be deleted. Poorly formulated personal theories, unfounded challenges of mainstream science, and overt crackpottery will not be tolerated anywhere on the site. Linking to obviously "crank" or "crackpot" sites is prohibited.

Unfortunately, without a background in mathematics or physics you will have great difficulty in being taken seriously anywhere else. For people to take your theory seriously, they will expect you to have a good understanding of existing theories. (E.g. see the Independent Research Guidelines referred to above.)

 

[GoliathX]

No, if your views are highly speculative and go against the grain of accepted theories, then it's against the rules of this forum to post your thoughts here:



Unfortunately, without a background in mathematics or physics you will have great difficulty in being taken seriously anywhere else. For people to take your theory seriously, they will expect you to have a good understanding of existing theories. (E.g. see the Independent Research Guidelines referred to above.)

It is not really that highly speculative, all it really is is a change in perspective of how the current theories are currently viewed. It is just one thing or idea that can explain a bunch of these things we scratch our heads at, more than just specified above.

I have a good understanding of existing theories, I just do not have the schooling to go with it. Well read, just can't do the math, by myself that is. I would love to work with somebody that does possesses those qualities, but I have no idea how to go about finding somebody willing to come down to my level (little math).

I don't just want to throw the idea out there however, especially on a message board. It is not because I am worried about criticism, that is expected.

 

[pallidin]

Second, how can I go about getting taken seriously?

Well, that must be "earned"
That is, you must prove yourself right(or reasonably so) WITHOUT any DEMAND that others MUST prove you wrong.

In other words, try not to have an attitude like "well, you can't prove me wrong so I must be right"
That just goes nowhere really fast, and makes one look like a babbling idiot.

So, with a speculative theory, I would approach it by first asking reasonable, specific questions. Allow yourself to be educated by the responses.

 

[GoliathX]

Well, that must be "earned"
That is, you must prove yourself right(or reasonably so) WITHOUT any DEMAND that others MUST prove you wrong.

In other words, try not to have an attitude like "well, you can't prove me wrong so I must be right"
That just goes nowhere really fast, and makes one look like a babbling idiot.

So, with a speculative theory, I would approach it by first asking reasonable, specific questions. Allow yourself to be educated by the responses.

That is not an issue. I am trying to bring this information humbly, I know where I stand. I am at the bottom rung of the ladder pretty much when it comes to credentials.

I have seen plenty of people raise their hands triumphantly saying THEY HAVE THE ANSWER only later to be seen with their tail between their legs. I do not have THE ANSWER. What I have may possibly be an answer, but I don't have the means or the methods to verify this by myself.

 

[pallidin]

... but I don't have the means or the methods to verify this by myself.

OK, well, that's perfectly fine, so what are your questions or statements regarding your theory? Let's start with that.

 

[GoliathX]

I am not quite sure where to begin, honestly. Like I stated earlier, I don't wish to put everything out on a message board.

I guess the expansion of space is as good as any.

Space isn't expanding, all of the material within 'space' is getting smaller. The more mass and volume something has the quicker this takes place. This is why everything around us is redshifting.

Go ahead and ask your questions, I will do my best to answer them.

 

[PhysDrew]

Space isn't expanding, all of the material within 'space' is getting smaller. The more mass and volume something has the quicker this takes place. This is why everything around us is redshifting.

So are you saying that all of the mass in the universe is getting smaller? Or is the volume of the mass getting smaller (in which case the density would increase)? Seems to me that either of these would lead to violations in the theories of relativity and the effects of gravity (please correct me if I'm wrong).

 

[pallidin]

So, you are under the impression that the "space" is contracting as opposed to expanding. Do I have that right?

 

[pallidin]

A little heavy, but a good treatment on "redshift":

http://en.wikipedia.org/wiki/Redshift

 

[GoliathX]

No, I am not saying space is contracting, nor am I saying objects are becoming more dense.

I am saying that all objects are decreasing their size in space. This is where I know that I don't have enough of an education in math or physics to explain myself but I will do my best.

Think of it like a tesseract, but in time. In one moment the outer cube exists, but as what we call 'time' passes, 'time' being change, the same cube exists but each point in the 3rd dimension has decreased its volume in physical space. This happens continuously.

It is a fractal in that in the very next moment, which never ends, it can only be self-similar. It cannot be the same thing twice. We know that all of the atoms in the cube move, but the space between all things increases as well (but is an illusion).

This would be why everything is 99.9% space, in, through and around atoms. Not because space is expanding, but these things, by nature of the 4th dimension and what it is, are getting smaller.

Time passing is a fractal. All movements and change are self-similar to what it previously was. Things change because nothing can be the 'exact' same thing it was before.

Hopefully this makes some sense.

 

[bp_psy]

What I have may possibly be an answer, but I don't have the means or the methods to verify this by myself.

I am sorry but you do not have any "possible answers". You only have a illogical sequence of ideas that sound cool to you but do not really mean anything.
You should learn what a scientific theory is ,how it is developed and what is its purpose before you even try to think of coming with one of your own.

 

[PhysDrew]

No, I am not saying space is contracting, nor am I saying objects are becoming more dense.

I am saying that all objects are decreasing their size in space. This is where I know that I don't have enough of an education in math or physics to explain myself but I will do my best.

Think of it like a tesseract, but in time. In one moment the outer cube exists, but as what we call 'time' passes, 'time' being change, the same cube exists but each point in the 3rd dimension has decreased its volume in physical space. This happens continuously.

It is a fractal in that in the very next moment, which never ends, it can only be self-similar. It cannot be the same thing twice. We know that all of the atoms in the cube move, but the space between all things increases as well (but is an illusion).

This would be why everything is 99.9% space, in, through and around atoms. Not because space is expanding, but these things, by nature of the 4th dimension and what it is, are getting smaller.

Time passing is a fractal. All movements and change are self-similar to what it previously was. Things change because nothing can be the 'exact' same thing it was before.

Hopefully this makes some sense.

Hmmm doesn't really sound plausible. Sounds unnecessarilly complex as well (Occam's razor would do wonders with this). So are you implying that the universe is finite?

 

[GoliathX]

Hmmm doesn't really sound plausible. Sounds unnecessarilly complex as well (Occam's razor would do wonders with this). So are you implying that the universe is finite?

Not sure how it would be more complex. 4th dimension being both 'time' and volume (volume being a point tangent off of every 3 dimensional surface point, not sure if I am explaining dimension correctly here) explains the redshift of all solar objects away from us as well as the movement of local bodies away from us (sun and moon).

Right now, they explain the expansion of space as 'possibly' being Dark Energy since they really don't have a good grasp as what is really causing it, as well as why those objects further from us are moving more rapidly. The sun (15cm per year) and moon (4cm per year) moving away from us is currently believed to be because of tidal forces.

Which would be more complex to explain the expansion? A 4th dimensional change over time that occurs to all objects (micro and macro), or a bunch of other options that we aren't even sure of?

 

[PhysDrew]

Which would be more complex to explain the expansion? A 4th dimensional change over time that occurs to all objects (micro and macro), or a bunch of other options that we aren't even sure of?

I see you point, however the bunch of other options are based on the well known, experimentally proven (as well as rigorous mathematical proofs) theories.

And also, when you say the 4th dimension is both time and volume, are you implying that both time and volume are changing linearly? Sounds like it, as you say volume being a point tangent off of every 3D surface. I can think of at least one specific example where volume change isn't linear.

 

[GoliathX]

I know that the math works for those other options, I am not saying they don't and I am also not saying they are not right. I don't see why it would have to be either/or and not both/and. With a 4th dimensional change there is certainly room for other causes for expansion as well.

I do mean linearly. Tangent off of every point of a surface, yes, meaning a sphere within a sphere at the Planck scale. And another, and another and so on over what we call 'time'.

What is your example? Just want to make sure we are seeing it the same.

 

[PhysDrew]

Well I have to say it certainly sounds interesting to me. But yes not sure if I'm understanding your view of linear volume change. The example relates to a simple thermodynamic process in the freezing of water. From 0 to 4 degrees celsius the volume of water decreases, whereas from 4 degrees celsius on, the volume increases. This is why only the top layer of a lake freezes (as water has its greatest density at 4 degrees celsius, thus the temperature of water below the ice is set at 4 degrees, as the more dense water 'sinks'), and has important consequences for life on Earth overall. Variations like this seem to make volume an intrinsic property of matter, rather than an extrinsic, emergent phenomenon.

 

[GoliathX]

Thanks for using the example of ice, I know what you are meaning with that and I think I confused you and others. I used the word 'volume' initially thinking it would help get my point across, but I think it may have made it worse. This is where I know my lack of schooling is going to cause me issue.

I hope this works. I will use an example of three spheres.

From the point of their creation, these 3 spheres are each 1m apart and 1m in diameter. We will just use 100 years as a timeline from beginning to end. At the end of 100 years, they are each still measured at 1m in diameter, but the space between them say increased to 1.05m.

If you view this sphere in a 4th dimensional structure over 100 years, it would be a straight line. Going down this line from beginning to end, you would see a gradual decrease in its size. However, the sphere will never notice it's own change, since this same change is happening to everything simultaneously.

I am not going to do the math for this example since I am trying to get this done quickly as it is late, but the .05m change in distance between these objects was not caused by anything external, but rather a change in their 4th dimensional shape over 100 years.

Like the tesseract (cube within a cube), but this is happening at the Planck scale. Each fraction of an attosecond, every surface point is forced to immediately change but must remain self-similar.

 

[Pilot7]

JustOne of the problems I have when people talk about time is that they are not clear what they mean from the get-go. This goes for high and low alike (for example, I take pretty serious issue with Hawking's characterization). In fact, just about the only person I have heard talk sensibly about time is Penrose, but that is mostly because he avoids saying too much...

As a philosopher (of science) I would say this question is one of a very few questions in physics where philosophy might really have something to offer. It is important to get clear and then really clear about what we are saying when we talk about "time" or any cardinal measure of time.

Because there are some bad habits that lurk in this. For example, if we speak of a "second" we may even be sensible enough to identify a relativistic frame of reference, but there are still two wildly different senses we could mean. The one might be something like "if I were in place/reference frame X, Y could happen in a second". The other could mean that "over in place/reference frame Z, Y would take 1 second to happen". The difference is subtle, because in the first instance I am grounding the phenomenology in my first person experience (or potential first person experience), as in what things would be like if I were to run some sort of physical experiment. In the second, I am organizing data according to a theoretical filing system I call time, but not in a way where I imagine what it would be like to be there in (first) person.

This may seem obscure to physicists and physically minded folk, but you cannot escape the issues that appear. The hydra of quantum physics makes the issues very prescient - as those of you who are familiar with usual run of quantum paradoxes to do with cats and cat keepers and Zeno and so on are aware.

Underlying the inevitable first person aspect of QP (quantum theory) and the radically third person view of RT (relativity theory) there is a really big contradiction lurking where the two come in contact. Sometimes called the "problem of time" in certain circles.

Anyhow, hope I am sounding lucid here :-) A few paragraphs like this always feels like a ramble when talking about this stuff...

 

[Dale]

GoliathX, please review the rules of overly speculative posts. This forum is for learning and discussing mainstream physics, not personal theories.

 

[Delta2]

Indeed time has to do with change but then what is change? An object as long as it isn't in the absolute zero will always have thermal motion so internally it continously changes. But change is always thermal motion or motion in general?of course not for example when a particle and an antiparticle anihhilate, mass is converted(changed) to energy (although this process still involves motion of the particles). I guess the notion of change is elementary and cannot further be explained.

 

[GoliathX]

GoliathX, please review the rules of overly speculative posts. This forum is for learning and discussing mainstream physics, not personal theories.

You are right, it kind of got derailed from what I felt time was to speculation on expansion. Sorry about that. Would it be possible to spin those off to it's own thread for those that wish to discuss?

 

[Pilot7]

Indeed time has to do with change but then what is change? An object as long as it isn't in the absolute zero will always have thermal motion so internally it continously changes. But change is always thermal motion or motion in general?of course not for example when a particle and an antiparticle anihhilate, mass is converted(changed) to energy (although this process still involves motion of the particles). I guess the notion of change is elementary and cannot further be explained.

Indeed - but is change elementary? Currently not in any physical theory I know of.

One of the difficulties in talking about 'change' is that we currently lack a specific or concrete way of talking about it. THis was the direction of my own work: develop a logic that makes 'change' explicit.

If you think through this a bit and take a look around, you will find that (almost) all attempts to such reduce the notion of change to a relative frame of reference involving 'time' -- ahhh, but what was time? I thought we had defined 'time' in terms of 'change'!

Round and round we go...

However, if you try to define 'change' without reference to time, you find you get into theoretical deep water very quickly. The problem is to develop a *consistent* logic that does this, and it may indeed be impossible.

If there is a way to formulate a consistent logic to speak of change, it is going to require a radical rethink of the way we identify reality: one has to move to a system of perspectival moments instead of socially acknowledged absolute events (which are the foundation of the physical and scientific enterprise -- we need all to be able to refer to specific experiments and agree on the outcome...)

Another alternative is the development of what are called 'para-consistent' logics: Here you provide for limited inconsistency in the theoretical expressions referring to the phenomenological world.

If this is sounding like Greek, let me put it this way:

You want to find a way to speak about say a glass of wine on a table in one moment and the *same* glass of wine on the floor in another moment, and you want to find a way of speaking about this 'change' without referencing 'time'. If you say the *same* glass of wine is both on the floor AND on the table, there is an intrinsic inconsistency.

Most logics (including the 'languages' we call physics and mathematics) are not formulated in a way to allow even a single inconsistency.

This seems to be the rub of the problem on the theoretical side.

 

[K^2]

There are three entirely different and only somewhat related things that are meant by people when they say "time".

1) Time is a parameter in Quantum Mechanics. It has absolutely none of the typical connotations. It's an arbitrary quantity by which the system's state is parametrized. An infinitesimal change in time-parameter results in infinitesimal change in state. A differential equation relating two infinitesimal changes can be found.

2) Time is a dimension in General Relativity. Very straight forward. It's just a distance in a fairly arbitrary direction in 4-space. There are restrictions on which direction you can pick, but there are still infinitely many possibilities. Two coordinate systems with different choices of time direction are moving relative to each other.

There is a relationship between time in Quantum Mechanics and time in General Relativity, in that if you measure change in GR time along particle's own world-line (Proper Time), it agrees with change in time-parameter in particle's equation of state. This has many useful consequences. For example, it let's us build clocks.

3) Time is the ordering of states in Statistical Mechanics. This one is probably the most interesting one. It's the one that tells you why you remember yesterday, but cannot remember tomorrow, even though in both QM and GR the two directions in time are absolutely identical. Entropy of a closed system cannot decrease. Second Law of Thermodynamics. Another way to read this law is that the state with higher entropy must come after the state with lower entropy. This is very important, because process of storing information requires an increase of entropy in the surrounding. That means that information is always available only about events on one side of time axis from moment in question. That's what let's you recall yourself recalling something else, and gives the entire effect of time flow.

 

[Pilot7]

There are three entirely different and only somewhat related things that are meant by people when they say "time".

1) Time is a parameter in Quantum Mechanics. It has absolutely none of the typical connotations. It's an arbitrary quantity by which the system's state is parametrized. An infinitesimal change in time-parameter results in infinitesimal change in state. A differential equation relating two infinitesimal changes can be found.

2) Time is a dimension in General Relativity. Very straight forward. It's just a distance in a fairly arbitrary direction in 4-space. There are restrictions on which direction you can pick, but there are still infinitely many possibilities. Two coordinate systems with different choices of time direction are moving relative to each other.

There is a relationship between time in Quantum Mechanics and time in General Relativity, in that if you measure change in GR time along particle's own world-line (Proper Time), it agrees with change in time-parameter in particle's equation of state. This has many useful consequences. For example, it let's us build clocks.

3) Time is the ordering of states in Statistical Mechanics. This one is probably the most interesting one. It's the one that tells you why you remember yesterday, but cannot remember tomorrow, even though in both QM and GR the two directions in time are absolutely identical. Entropy of a closed system cannot decrease. Second Law of Thermodynamics. Another way to read this law is that the state with higher entropy must come after the state with lower entropy. This is very important, because process of storing information requires an increase of entropy in the surrounding. That means that information is always available only about events on one side of time axis from moment in question. That's what let's you recall yourself recalling something else, and gives the entire effect of time flow.

Yes in the rought. However there is more to be said and a few minor corrections and a major conceptual issue to addres and one paradox in a pear tree...

QM - there is an asymmetry in one case: some kind of muon (I forget which - kaon? Pion?)

However, yes, it is a theoretical parameter with complex value. However, even how this parameter is computed specifically varies in certain contexts (this is what I meant earlier about the.. seven times of quantum theory - btw, there was a nice book a few years ago with a title along those lines - can look it up if you are interested)

GR time is fairly straightforward (bad pun!) provided you stick to classical worldlines only. And no revolving universes (Goedel universes). If you allow the latter, you get backwards time travel, which is not necessarily a problem in itself... unless you think there is something to freewill. In which case you just got in hot water for a number of reasons.

There is also a minor issue that has been proposed in the so called hole argument, but I don't think it amounts to anything personally (sure, let that one be a pun intended).

If however you mix up QT and GR you have issues per the EPR paradox for example. This is very troubling if you are the sort of physical thinker who likes to create problems. A lot of fundamental ontological questions get asked, including the fundamental nature of time (as some kind of parameter on some kind of states, whether QT or classical).

As for CP (Classical Physics) and entropy (whatever that is exactly) - I was never satisfied by the definition of time based on this. There are several reasons why, but to highlight a few points:

Remember, the 2nd law of thermodynamics speaks in terms of time in the first place. However, if you grant that, it is sometimes interpreted as explaining directionality, and this is really a big mistake. At best you get asymmetry, not directionality, which is a more subtle concept that invokes intentionality (philosopher's term - but basically the idea of meaning or semantics). It is worth adding that even the asymmetry aspect breaks down in certain borderline cases as I believe Penrose demonstrated.

Anyhow, it is a very big jump to suppose that the 2nd law of entropy is responsible for inability to remember the future and only the past. To say this has not be proven or demonstrated in any sense by anyone is no far fetched claim. That is just one of the dogmas of the religion of scientism (ie it is not at all science...)

Cheers!
Pilot

 

[Pilot7]

right, and forgot to add most importantly...

In QT, there is a big difference that arguably results from treating wave collapse as ontological. If you do that, then it begs a time frame for successive quantum states. That is not the only way of course to treat quantum events. Note my reference previously to the EPR paradox in this respect.

K - going to step away from this can of worms now and do some work.

 

[Delta2]

However, if you try to define 'change' without reference to time, you find you get into theoretical deep water very quickly. The problem is to develop a *consistent* logic that does this, and it may indeed be impossible.

If there is a way to formulate a consistent logic to speak of change, it is going to require a radical rethink of the way we identify reality: one has to move to a system of perspectival moments instead of socially acknowledged absolute events (which are the foundation of the physical and scientific enterprise -- we need all to be able to refer to specific experiments and agree on the outcome...)

Another alternative is the development of what are called 'para-consistent' logics: Here you provide for limited inconsistency in the theoretical expressions referring to the phenomenological world.

If this is sounding like Greek, let me put it this way:

You want to find a way to speak about say a glass of wine on a table in one moment and the *same* glass of wine on the floor in another moment, and you want to find a way of speaking about this 'change' without referencing 'time'. If you say the *same* glass of wine is both on the floor AND on the table, there is an intrinsic inconsistency.

Most logics (including the 'languages' we call physics and mathematics) are not formulated in a way to allow even a single inconsistency.

This seems to be the rub of the problem on the theoretical side.

First all i am greek myself ) some of it sounded not greek but chinese i would say (hehe both greek and chinese are civilizations with big history anyway). I still don't see it as a problem of consistency/inconsistency/partial or limited inconsistency, rather i see it as a problem to express something which seems to be elementary in other more trully elementary concepts.

There are three entirely different and only somewhat related things that are meant by people when they say "time".

1) Time is a parameter in Quantum Mechanics. It has absolutely none of the typical connotations. It's an arbitrary quantity by which the system's state is parametrized. An infinitesimal change in time-parameter results in infinitesimal change in state. A differential equation relating two infinitesimal changes can be found.

2) Time is a dimension in General Relativity. Very straight forward. It's just a distance in a fairly arbitrary direction in 4-space. There are restrictions on which direction you can pick, but there are still infinitely many possibilities. Two coordinate systems with different choices of time direction are moving relative to each other.

There is a relationship between time in Quantum Mechanics and time in General Relativity, in that if you measure change in GR time along particle's own world-line (Proper Time), it agrees with change in time-parameter in particle's equation of state. This has many useful consequences. For example, it let's us build clocks.

3) Time is the ordering of states in Statistical Mechanics. This one is probably the most interesting one. It's the one that tells you why you remember yesterday, but cannot remember tomorrow, even though in both QM and GR the two directions in time are absolutely identical. Entropy of a closed system cannot decrease. Second Law of Thermodynamics. Another way to read this law is that the state with higher entropy must come after the state with lower entropy. This is very important, because process of storing information requires an increase of entropy in the surrounding. That means that information is always available only about events on one side of time axis from moment in question. That's what let's you recall yourself recalling something else, and gives the entire effect of time flow.

1 and 2 are very mathematical ways of looking at time, it might be convenient to look it that way for QM or GR . However how can we say that the two directions in time ( i suppose u mean backward and forward) are identical since entropy increases as time increases and if we could go backwards in time we could have a decrease in total entropy.

 

[Pilot7]

First all i am greek myself ) some of it sounded not greek but chinese i would say (hehe both greek and chinese are civilizations with big history anyway). I still don't see it as a problem of consistency/inconsistency/partial or limited inconsistency, rather i see it as a problem to express something which seems to be elementary in other more trully elementary concepts.

1 and 2 are very mathematical ways of looking at time, it might be convenient to look it that way for QM or GR . However how can we say that the two directions in time ( i suppose u mean backward and forward) are identical since entropy increases as time increases and if we could go backwards in time we could have a decrease in total entropy.

Well Yahsu! Or Nee Hao Ma!

Yes, so we have an apparent elementary quality and maybe there is something more elementary we can use to define/characterize/address it. Maybe.

Here was my approach: First, tease out all the features that bundled together with what we mean by time. There are quite a few... for example,

1. There are several structural layers. It is one dimensional or two (noting complex case in QT). It has a metric, a topology, etc. etc. Ultimately, all of these structural features boil down to a set theoretic expression defining:

i. a set
ii. with a topology
iii. with a metric
iv. asymmetrical structure

and so on. Doing this actually helps to clarify the rather significant differences evident in different physcial characterizations of time. Okay, this was the 'easy' part of the problem. Now to the hard part...

i. it has direction
ii. it has 'flow'
iii. it has a magical locus called a 'now'

There are two ways to go. Either we say all this other stuff is 'psychological' and leave it to the psychologists to sort out (personally, not an approach I recommend!) or we rethink what we mean by physical properties.

If we go the second way, it may well be that there are more 'fundamental' ways to speak about time - in fact, that is my own personal 'religious' intuition on the issue - but whatever the 'truth' of the matter may be, we need to find a way to even speak about it.

In this sense, we need to be able to speak about something like 'change' or 'now' or 'direction' or 'flow' (as a 'quale' or phenomenological qualityity) in terms that a hard nosed physicist can actually smell it so to speak. That is not easy in some cases.

Sure, we can define 'now' as a perspective - that is relatively unproblematic. But direction has no meaning in the physical lingo nor does flow or change...

So without this, how can we ever hope to find the real elementary parts upon which what we called time is built/structured/made? For even if we epiphony our way to an answer, we still do not have the language or semantic tools to speak about these things...

 

[K^2]

1 and 2 are very mathematical ways of looking at time, it might be convenient to look it that way for QM or GR . However how can we say that the two directions in time ( i suppose u mean backward and forward) are identical since entropy increases as time increases and if we could go backwards in time we could have a decrease in total entropy.

Yeah, the directions themselves are symmetrical, so it must be something about the states in the two direction that result in the "arrow of time".

If you allow me a bit of speculation here, because there are a few shaky points in what follows, I can try to suggest a solution. If we take GR as our starting point for looking at the universe, the entire universe as a whole just is. It's not really expanding, or evolving, or doing anything else. It's a 4-manifold with some fields in it. For whatever reason, it happens to be "larger" on one "end" of what we call time than the other. Specifics aren't important. What's important is that if our notion of entropy as applied to a closed volume still applies to the entire space, we must conclude that the total equilibrium entropy is higher where the time-section of the universe is larger. This is one of these shaky points, because we are now dealing with stat-mech, which relies on QM, in context of GR, and GR and QM don't agree. We really need Quantum Gravity here. Now, this is equilibrium entropy, and we are dealing with non-equilibrium system. So something else must be going on. It seems like it should work out in Many-Worlds, but again, can't do Many-Worlds and GR at the same time without Quantum Gravity.

Short version - We really need Quantum Gravity to properly describe time, but expansion seems to be responsible for the arrow of time.

Edit: Pilot7, you can't treat time as a purely mathematical entity. It's related to entropy, we know that, so you aren't going to be able to describe time without keeping stat-mech in mind.

 

[Delta2]

Short version - We really need Quantum Gravity to properly describe time, but expansion seems to be responsible for the arrow of time.

Suppose time occasionally goes backward in this universe, if that is happening in the universe as a whole (as expansion is happening on global scale ) how could we ever observe it? Since our brains are living in the universe when time goes backward, it goes backward for our brains too and all of the neurobiochemical processes of our brain which are responsible for the storing of info are reversed too and this is info is just removed from our minds. It is like growing old and then with time reversal becoming baby again but once you become baby all of your memory is removed and you won't remember that you had grown old.

The only way to observe time reversal is if it is happening on confined region of the universe and the observers are out of this confined region.

 

[MJA]

Tic Toc

Historically time was a manmade mathematical tool designed to measure the motion of the stars. Today we use it not only to measure everything including ourselves, we also use it to control ourselves. Unfortunately time is as uncertain as any other of our manmade measures of nature, and Heisenberg's Uncertainty Principle truly only the tip of the berg.
Time is as all of our measures only theoretically quantum mechanical at best.
And beyond our current best measurements is the absolute truth.
God doesn't play dice, but we do.

=

Need proof?
What time do you have?

 

[Pilot7]

Yeah, the directions themselves are symmetrical, so it must be something about the states in the two direction that result in the "arrow of time".

If you allow me a bit of speculation here, because there are a few shaky points in what follows, I can try to suggest a solution. If we take GR as our starting point for looking at the universe, the entire universe as a whole just is. It's not really expanding, or evolving, or doing anything else. It's a 4-manifold with some fields in it. For whatever reason, it happens to be "larger" on one "end" of what we call time than the other. Specifics aren't important. What's important is that if our notion of entropy as applied to a closed volume still applies to the entire space, we must conclude that the total equilibrium entropy is higher where the time-section of the universe is larger. This is one of these shaky points, because we are now dealing with stat-mech, which relies on QM, in context of GR, and GR and QM don't agree. We really need Quantum Gravity here. Now, this is equilibrium entropy, and we are dealing with non-equilibrium system. So something else must be going on. It seems like it should work out in Many-Worlds, but again, can't do Many-Worlds and GR at the same time without Quantum Gravity.

Short version - We really need Quantum Gravity to properly describe time, but expansion seems to be responsible for the arrow of time.

Edit: Pilot7, you can't treat time as a purely mathematical entity. It's related to entropy, we know that, so you aren't going to be able to describe time without keeping stat-mech in mind.

@K^2

I like the model - I think this is roughly the way one has to go in thinking about this if one takes going theories as they currently are.

I should probably clarify some of what I said before not to be misunderstood. I don't think time actually is just a mathematical construct, nor do I think this approach in itself is helpful. What is helpful is separate out its constituent qualities as we try to understand it, and in this sense, we want to in a way isolate all of its mathematical properties on one side so to speak.

Yes, of course entropy is clearly a very important part of whatever is actually going on, and statistical mech (as founded on QT) is a very important part of the equation so to speak. And while I do not think all of 'psychological time' will reduce to SM as is sometimes advocated by a certain subsection of the faithful who pray at the alter of scientism, that doesn't mean it is still not clearly a very important part... In other words, entropy is arguably an essential or necessary aspect of our temporal experience, but it is not a sufficient foundation in itself.

One of the very, very important aspects to keep in mind here is what we mean by the 'arrow of time' which has really created a mess in the literature. Because there are different sorts of qualities that need to be distinguished clearly (asymmetery, anisotropy, direction, etc.) and part of why I try to avoid using the arrow of time metaphor.

Anyhow, following through on your model - so we have a big hyper-dimensional blob that models the universe GT style. And for the most part (except at the edges) it behaves like a good differential manifold (I think I am getting terms right - I'm a bit rusty on some of this). Now we want to identify 'entropy' in our big puzzle board - so we say it is a relative measure of organization of parts of fields in different regions of our blob.

Based on this, can we show or dot in a time dimension that is 'perpendicular' so to speak of the gradient of entropy regions? Or are there many such entropy time lines?

But this approach partly begs the question of what we mean specifically by entropy, which can be treated differently in different contexts. I will admit that I feel like I have tended to play a little fast and loose with entropy here and not done my home work to get very clear about what it means or how to represent it, in the sort of model you have sketched out for example.

Ok - defintely feel like I am rambling now, so will stop...

 

[Pilot7]

Suppose time occasionally goes backward in this universe, if that is happening in the universe as a whole (as expansion is happening on global scale ) how could we ever observe it? Since our brains are living in the universe when time goes backward, it goes backward for our brains too and all of the neurobiochemical processes of our brain which are responsible for the storing of info are reversed too and this is info is just removed from our minds. It is like growing old and then with time reversal becoming baby again but once you become baby all of your memory is removed and you won't remember that you had grown old.

The only way to observe time reversal is if it is happening on confined region of the universe and the observers are out of this confined region.

Careful - you really need to be clear on what 'time going backwards' means... do you mean the universe is infused with an ether of 'causal arrows' of some kind? Do you mean that local conscious experience has rearranged its successive states of awareness and the 'intentionality arrows' between phenomena are reversed? Important to be clear on what going backwards (or forwards) actually means...

 

[Delta2]

Careful - you really need to be clear on what 'time going backwards' means... do you mean the universe is infused with an ether of 'causal arrows' of some kind? Do you mean that local conscious experience has rearranged its successive states of awareness and the 'intentionality arrows' between phenomena are reversed? Important to be clear on what going backwards (or forwards) actually means...

I can't possible know how a time reversal could be initiated and further analyzed but in a time reversal as i see it, the effect becomes the cause and the cause becomes the effect. Everything goes like someone pressed the reverse playback button on a video player. Not sure what will happen to the local conscious experience but i guess if with time going forward we gain experience, with time going backwards we lose experience. So if we indeed lose experience when a time reversal happens we could never realize that it has happened. Perhaps all that remains is a deja vu feeling but then again this means that the time reversal was not ideal.

 

[K^2]

If you COMPLETELY reverse time, nobody would notice anything. You only perceive time because of your ability to remember things, and if your memories run "backwards" along with everything else, you still perceive time in the original "direction".

The more interesting question is what happens in localized time-reversal. There have been experiments where dynamics of a system is locally reversed. That is equivalent to local time reversal. However, there is a problem. There is no way to interact with a time-reversed state without altering it, and if you alter the state, you ruin time-reversal. So while we can run time "backwards" in a small closed system, we cannot use it to send information, and so it's useless for any practical purpose.

 

[Pilot7]

Backwards time 'travel' --

Here is the thing - first before we can talk about 'backwards' time travel, we need to understand 'forward' time travel. And that requires us to be clear by what we mean by 'travel' altogether! And looking more closely at that, we need to understand or define identity, as in 'bob travels' - what do we mean by 'bob'?

So I invite you all to consider very carefully what is identity – as in why is YOU the same YOU that was yesterday/tomorrow? Think of it this way, we are here now. And we have clones in the past and future. And we thing those clones are US – and happily our clones feel similarly, identifying with us through memory and expectation – not unlike the Borg actually...

Can we then transpose this sort of identity onto objects putatively without an inner sense or consciousness of identity? Can we say that electron is a clone of that electron that was fired out of that cathode ray tube?

If we can get clear on what we mean by identity, then we talk about travel. If we can get clear about travel, then we can get clear about interaction and causality. If we can do that, we can begin to speculate about what direction might mean. If we can do that, we can make sense of forward. If we can do that, sorting out backwardness will follow easily...

So on that, your local philosopher friend leaves off with a warning: Beware my physicist friends, pay attention to your fundamental assumptions :-)clone Pilot7-555 signing out

 

[Selraybob]

I've been reading through a bunch of these posts, and I can't get it out of my craw that Time is just a count. There are all of these complicated, mathematical theories that make Time into a fourth dimension or some theoretical math thing, but it's just a count. All we've ever been doing is counting things that happen, counting and marking them on the wall.