Time itself has a biased flow direction.

When dealing with many particles a closed system´s entropy increase tells which way “time flows”. E.g. a film recording a dropped glass shattering can be played backwards, but no one will believe the shards jumped up off the floor and to form the unbroken glass. Yet a film, if it were possible to make, of most particle interactions or decays does not by itself tell which end of the film was made first. I.e. particle physics seem to be "time reversible," as I previously believed, but not after reading:

http://www.economist.com/node/21561111

I.e. time itself has a biased flow direction, even in particle physics, not related to the many particle bias of entropy increasing, which stems from fact that disordered states of a many particle system are much more numerous than highly ordered states.

 

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Makes no difference which end you play the film from, time is always positive. In either case, the film progresses through time, ie, the start of play is t=0, and the end of play is t>0. Time is the duration of play and has NOTHING to do with content or which end is start and which end is finish.

When you drive your car in reverse does time reverse? Heck no! Time is always cumulative in the positive.

 

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I don't think that really helps. For starters, we still have CPT symmetry, so while time reversal isn't a symmetry on its own, it is part of a symmetry that also includes charge and parity conjugation.

Second, my recollection is that CP and T violations aren't very pronounced and are only a feature of weak interactions. But the structure of macroscopic matter is dominated by the electromagnetic interaction and nuclei by the strong/colour interaction, so T violations in weak decays is really just an interesting side-show and doesn't really help explain why we perceive a preferred "arrow" of time on macroscopic scales.

 

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I'm not even sure we can make such a definitive pronouncement that T-symmetry is violated. Perhaps there are conditions unaccounted for? What if, say, the expansion of the universe makes certain processes more likely?

 

Time is like placing the point of a pencil on a clean sheet of paper and moving the point along the paper in any direction. There is only one thing that can happen, the length of the path that the pencil draws on the paper increases. It is impossible to decrease the length of the line by moving the pencil, that simply adds more length. Same deal with time. No matter what you do IT TAKES TIME!

 

that is why they looked at reactions where CP was violated as then CPT not being means T must be too. As I recall the article´s T violation was 5 to 1 - very large.

True but on the macro scale time would have an arrow even if there were no T violations for reason I stated in the OP - many more ways to be in disordered state than in an ordered one. That is why entropy always increases there.

 

Well as the T violation is demonstrated in a very tiny volume compared to the universe expansion that being the cause would be an extreme case of Einstein´s "spooky action at a distance." Not to mention that information always flows less rapidly than C.

 

No one is surprised by that. What is surprising is that replacing t by (-t) in particle physics equations is not always valid. - I.e. some particle physic interaction movies, if they could be made, must be shown the same way they were made: forward, not backwards.

For all particle interaction that don´t involve "weak interaction forces" if I just give you a movie of the interaction you can´t tell which end of the film is the beginning and which is the end. If I give you a macro-movie film, say of dropped glass breaking, you can tell if you are running it thru the projector backwards.

 

Well the metric expansion of space is said to be intrinsic, meaning its observable effects (if any) should be basically uniform everywhere. That was just popped off of the top of my head, though. Here's another one: the prevalence of proper matter in the labs encourages certain processes, whereas if we were able to carry out the same experiments in anti-matter labs we would get other results.

These aren't serious suggestions, I just don't like that T-asymmetry has been apparently accepted to the point of law...

 

The direction in which the film is run through the projector is not the issue, the issue is time. Time of the playing of the movie, like you timed the viewing with a stop watch. How much time did the movie run for? That is the question. The DURATION of play! Regardless of the direction in which the film is run through the projector, the duration will be the same.

 

No not the question or problem at all. Read a little about CPT conservation but CP and now T conservation violation. Nothing to due with the time events last.

Correct and not surprising. What is surprising is that sometimes only running the film one way shows the correct physics when weak interaction are recorded on the film.

Like the macro case with film of a glass breaking, some films of particle dynamics must be shown only one way to present the correct physic, but agreed, playing the film backwards does take the same amount of time. If there are no weak interactions recorded on the particle film movie you can not tell which way to show it is not correct physics.

 

Being able to tell the way the normal progression of matter occurs has nothing to do with the time for which it takes for that action to occur. Time is simply the duration of that progression. Leave time out of it, because it has nothing to do with the manner in which matter progresses. Time is simply a measure of the duration of the progression, regardless of the natural order. The natural order of events is irrespective to the measure of time in which those events occurred.

 

MD, you have made several posts now which illustrate you are not understanding the discussion at hand. No one is denying that if you sat down at noon to watch a 2 hours film but played backwards you'd finish watching it at 2pm, that isn't what is being talked about.

If someone were to show you a film where a pile of glass shards on the floor suddenly recombined into a drinks glass and leapt up onto a table top you'd say "You're playing the film backwards". However, if someone else had filmed the same event but focusing in on a few atoms within the glass you'd be unable to tell which way the film was going, the particles bouncing around don't show behaviour which lets you determine which way the film is being played. However, if you zoom in to a single atom enough to be able to observe electroweak processes then you can tell the direction of time because when the film is run backwards you'd see the particles having a preference which runs counter to their usual behaviour. To give a vague analogy, the hands on a clock move clockwise but if you watched a reversed video of a clock you'd see the hands go the opposite direction.

So the complaints you've been making about what people are saying are themselves mistaken, you're not understanding what all the various symmetries involve and what they mean. T is for 'time reversal'. If a system is T symmetric if someone shows you a video of particle processes and you'd unable to tell which way the tape is being played. C is for charge conjugation. If a system is C symmetric then if you watch a video of particle processes then you cannot tell whether you're watching matter or antimatter. P is parity symmetry. A system is P symmetric if when you're shown a video you cannot tell whether someone had done a left-right swap of the video or not. It's known that quantum field theory has CPT symmetry, so if you do all the swaps then the dynamics will be indistinguishable from if you hadn't. It's also known that the electroweak force is CP violating, you can well whether you're watching a flipped video of antimatter compared to a non-flipped video of normal matter. This suggests that T is not a symmetry of the electroweak sector, else you'd have CPT violation due to CP violation.

I know you all sorts of axes to grind and bones to pick with mainstream physic's take on space, time and space-time but at least try to understand what is being discussed rather than trying to shoehorn in a line of discussion where you can air your grievances about relativity.

 

I'll simplify AN's point even further: we are discussing whether the natural order of events is fundamental, and NOT the measure of time in which those events occurred. The former is debatable, the latter is provably false. Time dilation is irrefutable.

 

The title of the thread is " Time itself has a biased flow direction." Again, time does not have direction. What you are describing is cause and effect. You are describing the way we normally observe the relationship between cause and effect, as compared to the opposite. Effect is not cause. Ashes don't turn into logs. Many particles don't turn into fewer particles. Mass does not get more dense. Entropy does not decrease. So all you're saying is that we can see cause and effect at some scales but not other scales. Big deal, we can't see either end of the spectrum of scale of particles. The scale of the universe is so large that we have no idea what if any role our universe plays on a larger scale. The scale goes so small that it is beyond our scope to understand cause and effect infinitesimally. Time (duration) has no cause and effect to have a "biased flow," it is simply duration.

 

MD has zero understanding of what this thread is about. Probably has no idea what CPT is about and never has had that discussed in a college level course. Expecting him to comprehend what we are discussing is like trying teach geometry to a dog.

 

I am not sure that is an accurate example. It seems to me that, at least in practical terms, dogs and their ancestral counterparts do understand geometry.., from inertial and accelerating frames of reference. Wolves, wild dogs, coyotes..., are all successful hunters, which requires a functional understanding of geometry.

They may not recognize it on paper, but in practical terms.... I don't the example is being fair to dogs.

 

Guess my recollection was wrong then. I had the impression CP violations in weak processes weren't very pronounced and it was C or P (can't remember which) violations which were much more easily observable, but that's just a vague recollection from a course on CP violation that I took over three years ago.

I'm not sure that really explains anything. The problem with the second law of thermodynamics is that it basically asserts that probability theory works one way in time but not the other.

 

Here’s the link to the original paper.

Observation of Time Reversal Violation in the B0 Meson System

In the one below, technically the symmetry is preserved if you take the magnetic field into account, right?

Breaking Time Reversal Symmetry With Light

 

Not likely. The problem with T violation is that it isn't just one experimental observation. It is something that is built into the Standard Model and was bult into electroweak theory before it. So T violation has been a part of our picture of fundamental interactions since at least the 1960s. As others have pointed out, T violation is not a concept that exists in isolation since it is impliead by CPT symmetry and CP violation (if CP symmetry is violated, then T symmetry has to be violated in order for CPT symmetry to be preserved). CPT symmetry itself is required by special relativity. It is also on the basis of the same models that we would judge whether the predominance of matter in our labs should have an effect or make asymmetries appear in weak interactions, and as far as I know we shouldn't expect it to. So I don't think you could claim T asymmetry in the electroweak sector of the standard model is wrong without claiming substantial parts of the Standard Model are wrong.

Regarding general relativity, special relativity is still a locally valid approximation even in an expanding universe, as long as tidal forces are weak enough to be ignored. The biggest deviation from SR inertial conditions concerning lab experiments is that lab experiments on Earth are performed in an accelerating reference frame. As far as I know, particle and accelerator physics is always worked out theoretically assuming SR inertial conditions simply because noninertial and GR effects are never expected to be significant.

It is accepted as a feature of the Standard Model, which is currently our best picture of fundamental particle interactions. Like any "belief" in physics, it is subject to change if new information comes up that requires us to build a better theory.

If T symmetry is going to be restored in physics, I'd guess the way that is most likely to happen is that T symmetry is found to be preserved in a more fundamental unified theory of particle interactions and that it gets broken somehow at the experimental scales we are capable of probing at the moment. That said I am not familiar enough with SM physics or GUT research to be able to tell you whether that is likely or plausible.