Time's arrow, or what universal property is asymmetric, anyway?

[john 8]

Originally Posted by john 8
Every measurement of time is based on what man decided that measurement to mean. Seconds, minutes, hours and so on are all man made. Time did not come pre-packaged in these units, man agreed on what to call these durations. Clocks measure how much of a pre-determined man made unit passed for a given motion. If something takes a minute of time, then that activity lasted for what man determined to be a minute. Time is the concept of man.

: following this same train of thought:

"Every measurement of mass is based on what man decided that measurement to mean. Kilograms, slugs, tons and so on are all man made. Mass did not come pre-packaged in these units, man agreed on what to call these amounts. Balance scales measure how much of a pre-determined man made unit balances a given object. If something is a kilogram of mass, then that object balances what man determined to be a kilogram. Mass is the concept of man."

Do you really think that mass is not physical? If not, then how is your logic plausible for time if it is so obviously not plausible for mass?

Holy crap! Do you really think that this is a logical argument in favor of your idea that time is a physical thing? I never said mass was not physical. Though your flawed logic makes it appear so.

Really? Did you even think this through? It sounds more like a knee jerk reaction.

Well you put this out here, so I will respond to it, but please think your thoughts through a bit better.

Here I go. I say that time is not a physical thing. You say time is a physical thing.

I say that there is no written or observational evidence that provides evidence that time is a physical thing.

You say time is a physical thing and yet have not given any scientific evidence to back up your claim. I am just supposed to take your word for it. Sorry, that is not science.



I said that every measurement of time is based on what man decided that measurement to be.

You wanted to use my example of time and replace time with mass and try to logically show that if mass is a real physical thing then time is a real physical thing. I like your ingenuity, yet it is severely flawed and I will show you how.

I will totally agree with you 100% that when you replace the term time with the term mass what you said is true about mass.

Here is where your logic falls flat:

Balance scales measure how much of a pre-determined man made unit of a given object is .

Balance scales require that you put a real physical object on it in order for that scale to give a man made unit. The important point here is, mass is a real physical thing and does not need to be measured in order for it to be a physical thing. Mass was a physical thing before it was measured. Mass is a physical thing even if it is not measured. Mass is defined in scientific reference books as something that is a real physical thing. Time is not.

You see, we already know that mass is a physical thing, measuring this thing does not change it. You are already applying a known physical thing to a scale and getting a man made unit of that measurement. The mass is an outside influence that is added to the scale and the scale then reacts to this influence (mass) and gives a man made measurement. The scale is provided a real physical thing, that thing was physical before it was measured.

Now time on the other hand is not a known physical thing that is defined as such in any scientific reference book. Clocks do not measure time. Time is not an outside influence that effects the movement of the clock.

In order for a clock to measure a thing called time then a clock would have to be constructed to measure this outside influence you call time. Time would have to be made in such a way as to have the ability to effect other physical objects. In order for any thing to have the ability to influence other physical objects that thing would have to be physical in some way, either a particle or a wave. So this rules out time as being a physical thing since it is neither a particle or a wave.

Your logic is faulty because mass is already known to be a real physical thing so your example does not prove that mass is a real physical thing because it can be measured. Mass was already a thing.



Clocks are a man made device operating as man designed it, counting off man made increments that man gave a numeric significance to, that results in a man made concept called time. Clocks are designed to give numbers, to which man assigns a significance or importance to. A clock could be considered to be a device or machine that generates a number or numbers in a regulated manner that was pre-determined by man. A clock is akin to a regulated number generator that converts mechanical, electrical, or the motion of an object to a number through a pre-determined engineering of the device, and these numbers are delivered at a rate that follows the set standards that man has agreed to be universal in all such machines.


Please share with me your definition of a clock and time that shows that clocks actually measure anything outside of its immediate construction. What outside influence is a clock measuring?


In order for your logic to be correct you will have to show that time is a physical thing before it is measured.

If time is physical it will be either a particle or a wave. Which is it?

 

[Chrisc]

No, no, it's not a circular argument. (BTW, that would be temperal 'inversion', rather than translation.)

It is circular. You've claimed that changing the sign of time "results" in inverted kinematics with no regard for the dynamics that gave rise to those kinematics in
the first place. Then you claim your inverted kinematics prove the dynamics are unchanged.
All you've done is shown the kinematical symmetry between left and right hand orbits.

You seem to think that all vectors such as acceleration and force should be inverted on inverting t. That depends on the equations of motion for any given physical arrangement.

Of course it depends on the equations of motion, but it depends on more than the kinematics of those equations.

Believe what you wish.

It is not belief, it is reason.

I won't bother this further until you give a mathematical example.

The mathematical example is your own, "When it's trajectory x=x(t) is is replace with x=x(-t) the orbit is reversed in direction, but the change in velocity, the acceleration, is still directed inward."

Why is the acceleration still directed inward? Is this something you've discovered or are you aware that all you've done is changed the orbit from left to right or right to left?

If I flip the spring in my clock, the hands will run backward. But the spring is still losing tension just as it was when the hands ran forward. This flip of the spring is what you are defining as time. It is not. It is the dynamics of the spring force that determines the kinematics of the hands or which way time runs. It is not the kinematics of the hands that determine which way time runs.

This does not follow.

It does, but you won't see it if you insist time is nothing more than kinematics.

I have no idea what gives you this idea.

It will make sense when you realize kinematics arise from dynamics. The second law of thermo"dynamics" expresses the indisputable empirical evidence of the order of events observed in the kinematics arising from . . . dynamics.

 

[Office_Shredder]

No, no, it's not a circular argument. (BTW, that would be temperal 'inversion', rather than translation.)

It's not very convincing considering all you've done is pick a periodic process and act shocked that it's periodic. Most people don't think of gravity as orbiting bodies, but as things falling or coming together. Is that process time reversible?

Also, G has a time unit component, so if you reversed time you have no reason to believe G will be unchanged

 

[Phrak]

Either of you two can use all the rhetoric you wish, but unit you put up with a concrete, mathematically backed example, I'm done with this parade. In either case you will fail to provide a valid argument, so it is moot.

 

[Dale]

Do you really think that this is a logical argument in favor of your idea that time is a physical thing?

Certainly not. It is a "reductio ad absurdum" rebuttal of your argument, not an a affirmative argument in favor of my position.

If time is physical it will be either a particle or a wave. Which is it?

I notice that you have dropped your "physics is about either matter or energy" in the other thread for this "physics is about either particles or waves". You are making the same argument with different categories so I will give you the same response as I gave https://www.physicsforums.com/showpost.php?p=1972713&postcount=53":

I wouldn't categorize physics like that, nor have I ever seen anyone else do so. Since you are making up this categorization, which category do you think distance belongs in? You should put time in the same category.

Also, what is your time-free definition of a wave?

 

[gendou2]

Troubles of categorization aside, do we have any laws that predict the arrow of time?
All known laws are time-symmetric, right?
The arrow of time does appear in experiments, right?
(Example: Waiting for a broken egg to piece itself back together and hop up onto a table -- a very boring experiment).
To me this seems to imply that there is a law missing, one that predicts the arrow of time.
Does anyone get the same impression?

 

[ZapperZ]

Troubles of categorization aside, do we have any laws that predict the arrow of time?
All known laws are time-symmetric, right?
The arrow of time does appear in experiments, right?
(Example: Waiting for a broken egg to piece itself back together and hop up onto a table -- a very boring experiment).
To me this seems to imply that there is a law missing, one that predicts the arrow of time.
Does anyone get the same impression?

But there are many phenomena that have a broken time reversal symmetry[1,2]. In fact, the CP violating events in kaon decays indirectly implies a broken T symmetry in such decays.

Zz.

[1] Covington et al. PRL 79, 277 (1997).
[2] Kaminski et al. Nature, 416, 610 (2002).

 

[Chrisc]

Troubles of categorization aside, do we have any laws that predict the arrow of time?
All known laws are time-symmetric, right?
The arrow of time does appear in experiments, right?
(Example: Waiting for a broken egg to piece itself back together and hop up onto a table -- a very boring experiment).
To me this seems to imply that there is a law missing, one that predicts the arrow of time.
Does anyone get the same impression?

I certainly do.
That's what my posts refuting Phrak's comments are about.
What's missing is the Principle of General Relativity applied to our "qualification" of fundamental
dimension instead of as it is now, just a quantification of measure. This is the reason the constant
debate over as you put it, the "categorization" of time continues.
It is also why such dimensional equivalences expressed by E=mc^2 are falsifiable and incredibly accurate "quantitatively".
If you're interested, I have submitted a model of time that predicts the second law of thermodynamics
in the FQXI.org contest.
"The Heuristic Significance of the Principle of General Relativity on the Nature of Time"
It is probably too absurd for most to appreciate, but might help you understand the dilemma.

As for your question of the time symmetry of the laws of physics, you will find all the laws are
and always will be time symmetric as long as the operational definition of time remains the accepted
definition of time in physics.
Any argument against such a kinematical-mathematical operation is futile as it amounts to disputing
the axioms of mathematics. Without any concern for the identities, kinematic and dynamic the math
represents, this operational definition of time cannot fail. This is the gist of Phrak's argument above.

So as long as we ignore the evidence of the second law (the most pervasive empirical evidence in
the history of the universe) and as long as we do not care about the few exceptions such as ZapperZ
pointed out, we can keep our heads in the sand and look for more comfortable solutions.

 

[Dale]

All known laws are time-symmetric, right?
The arrow of time does appear in experiments, right?
(Example: Waiting for a broken egg to piece itself back together and hop up onto a table -- a very boring experiment).

No, as mentioned above not all known laws are time-symmetric. The "boringness" of the broken egg experiment is governed by the time asymmetric 2nd law of thermo: dS/dt >= 0.

 

[ThomasT]

Troubles of categorization aside, do we have any laws that predict the arrow of time?
All known laws are time-symmetric, right?
The arrow of time does appear in experiments, right?
(Example: Waiting for a broken egg to piece itself back together and hop up onto a table -- a very boring experiment).
To me this seems to imply that there is a law missing, one that predicts the arrow of time.
Does anyone get the same impression?

The second law of thermodynamics is the thermodynamic arrow of time.

The basic equations of motion are time-independent.

The arrow of time does appear in experiments.

The universe is expanding. Since this is the source of all motion, maybe it can be used as the basis for some new fundamental law of physics.

The source of the expansion is an unsolvable problem.

 

[DB Katzin]

That's what some people think, but I really don't believe it at all. Time is something humans invented, just like any measurement system.

I think there is a distinction between a "measuring system" and the object the system is measuring. When one is describing the physical characteristic of an object the system: meters vs. yards, pounds vs. Kg is certainly arbitrary and invented but the object and quality being measured is something we all sense more or less in common: how big it is, how heavy it is, etc. Time it seems is different. When describing something when we ask how old is it we are not talking about an intrinsic quality you can rub up against like size or weight, even color or smell. Yet we all know what is being asked even if our measuring system differs: hours, days vs. moons since the great fire, etc. But I think you mean something different when you say "time is invented." Don't you mean something like this. We live in a world where we are aware of change. We change, the seasons change, the weather changes, the world changes. But not at the same rate. We need things like 2 o'clock so we can coordinate activities--something we do a lot of in complex society. So we count up a bunch of changes--sunrises, quartz crystal vibrations, etc and we standardize it so we know when to do stuff in relation to other stuff. But you don't find time anywhere. Even though you can spend time, you can't buy much with it, and even though you can save time, you can't put it in the back and get interest.