Time itself has a biased flow direction.

There's some good stuff here guys. I'm pleased to see a discussion on time that focusses on scientific evidence instead of wandering off into woo like time travel.

Billy, I read the Economist article and totally disagree with the conclusion. I have no issue with this:

"B-bars turn into B-minuses far faster than B-minuses turn into B-bars. As many as five B-minuses are produced for every B-bar. The chance of this result being a fluke is a nugatory one in 10^43."

But IMHO this is a cargo-cult non-sequiteur:

"Going forwards is thus not the same as going backwards, and time’s arrow really does exist".

As voiced on the thread, there is no such thing as "going forwards in time". It's merely a figure of speech. Things move or change, events occur, and clocks clock up some kind of regular cyclic motion rather than "the flow of time".

There are other proposals to explain the asymmetry, such as this one by Mark Hadley at Warwick.

"Nature is fundamentally asymmetric according to the accepted views of particle physics. There is a clear left right asymmetry in weak interactions and a much smaller CP violation in Kaon systems. These have been measured but never explained. This research suggests that the experimental results in our laboratories are a consequence of galactic rotation twisting our local space time. If that is shown to be correct then nature would be fundamentally symmetric after all. This radical prediction is testable with the data that has already been collected at Cern and BaBar by looking for results that are skewed in the direction that the galaxy rotates.”

 

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I agree with the statement that nature is asymmetrical because entropy always increases with time.

Do you see the circular argument in the words I made bold? It starts with an initial statement of nature being asymmetrical, and finishes with a final statement of nature being symmetrical after all, based on the initial statement. :shrug:

 

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I've never understood this disdain you have for time travel. The current status of time travel in physics, as I understand it, is:

• Most mainstream physics doesn't allow for it.
• Naturally, this reflects the fact we have no evidence that time travel is possible.
• General relativity is known to predict things like closed time-like loops which could be interpreted as a form of "time travel", but under some rather obscure or extreme circumstances which may be impractical or fundamentally impossible to realise in reality.
• There are a number of well known paradoxes (such as the grandfather paradox) associated with time travel. This may just mean that such paradoxes are based on an overly simplistic or crude conception of causality, but either way it is hard to imagine how time travel would be possible in a self-consistent universe.
• Some speculative theories, that are not accepted as mainstream, may allow time travel (I don't know), and some individual physicists might enjoy engaging in a bit of speculation about it from time to time. If so, that shouldn't be taken as an indication that such speculation is accepted physics or even that the person engaging in such speculation really "believes" in time travel. Just that, since we don't know all there is to know about the universe, there is still plenty of room for speculation.

Do you have a problem with anything I've written here in particular?

By that, they mean that they've found evidence that the laws of physics are not symmetric under time inversion (\(t \,\rightarrow\, -t\)), a feature of weak interactions that we've known about since the discovery of CP symmetry violations in the 1960s. Beyond that, you're getting into a pointless battle against language and figures of speech.

And what do you want, a certificate for being the millionth person to share this particular revelation? It's not even clear to me what you think you're refuting. Suppose time did "flow" in some literal sense. What would that look like? How is this "flow" measured? Who advocates that theory?

Here's the thing: I studied physics in university for five years, and I have every reason to believe everything I was taught in that time is representative of what the mainstream physics community thinks and takes seriously. One thing that is notably not on the syllabus is any formal theory about time "flowing". I was never asked to study about how time "flowed" or explain anything about time "flowing" in an exam. It is no more than an offhand phrase that is sometimes used, and if you took issue with a physicist carelessy talking about time "flowing" I seriously doubt many would be very interested in trying to formally defend their choice of words.

Just a word here: while the phrase "flow of time" is inherently meaningless in physics, don't confuse that with time itself being meaningless or not existing. We need such a thing as "time" in physics. If you specify where an event occurs but omit when it occurs, then the information you have given is incomplete. Unless you literally think now is the same thing as ten years ago, you are implicitly acknowledging that there is a difference, and that is exactly what we call "time".

Those proposals may or may not work. Either way, they are not fundamentally necessary: there is no fundamental problem if physics is not symmetric with respect to time inversion.

 

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You have badly misunderstood the text you quote. It does not start with the postulate that nature is fundamentally time-asymmetric. It starts with the observation that nature is apparently time-asymmetric and proposes that this may be an instance of what's sometimes called a "broken symmetry" in physics rather than a true fundamental asymmetry in nature. A "broken symmetry" means that a symmetry fundamentally exists but is apparently broken in some circumstance where an asymmetrical background effect is not accounted for.

Simple example: nature fundamentally has a full 3D rotational symmetry, but it doesn't look that way to us as we get on with our everyday lives on the Earth's surface. It looks in particular like "up" and "down" are different from horizontal directions, so it looks like the symmetry is broken. The symmetry is restored by noting that the gravitational field we experience is not "given" or "absolute" but is instead produced by a big rock in space that we happen to be sitting on.

Electroweak theory contains a famous instance of a broken symmetry: in electroweak theory all the gauge bosons are fundamentally massless, but they're all coupled to the Higgs field. At larger distance scales the Higgs field gains a nonzero vacuum expectation value with the result that the guage bosons emerge as different particles (the photon and the W and Z bosons) with different apparent masses.

General relativity also restores a broken symmetry, specifically with regard to the privileged or "absolute" role special relativity and Newtonian physics before it attributed to inertial coordinate systems. In GR the "inertialness" of a coordinate system is no longer absolute but is instead dependent on the distribution of matter and energy in the universe.

 

No mate. It was a refutation of the former view by the later view. The first bit just puts the orthodox view as a global claim, while the second bit points to new research that suggests that any claimed 'a-symmetry' should always be 'qualified' as conditional to local environmental factors like galaxy rotation/frame drag effects etc. etc. on the chirality of processes within its sphere of influence. Hence conclusion: Globally, the universe is symmetric. That's all that was saying. Cheers.

 

But how can you have speed without reference to time?
Speed is distance over time.

Take an hour or only a minute to make the same speed change and get the same mass change.
There must be some error here.
Cant think what it is at the moment
but I'll be back.

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Yes, it's more than some individual physicists might enjoy engaging in a bit of speculation about it from time to time. See for example this article where Kip Thorne talks about the possibility of time travel. Thorne is of course one of the authors of Gravitation by Misner/Thorne/Wheeler. Wheeler also indulged in time travel in the guise of his absorber theory, see this regarding "one electron". Sadly my hero Feynman has to be included too - the myth that the positron is an electron moving backward in time lives on. There's other examples such as Ron Mallett talking about building a time machine and John Cramer testing for retrocausality, plus more on arXiv.

It's not pointless przyk, it's important. The wrong language and the wrong figures of speech can cause huge problems.

No, but what I don't want is a whole pile of negativity from you in response to I'm pleased to see a discussion on time that focusses on scientific evidence instead of wandering off into woo like time travel.

An awful lot of people talk seriously about the flow of time. Google it. Here's George Ellis talking about it.

See above. It's more than just an offhand phrase.

I don't go round saying time does not exist. Surely you must know by now that what I say is this: Time exists like heat exists, being an emergent property of motion. It's a cumulative measure of motion used in the relative measure of motion compared to the motion of light, and the only motion is through space. So time doesn’t really flow and we don’t really travel through it.

 

There's maybe a bit of an error in that it would be better if Billy referred to motion or relative motion rather then speed. You've doubtless heard me say it before, but hold your hands up a foot apart. You can see the gap, the space, the distance between them. Now waggle your hands, and you can see them moving. You can see the motion. You can see distance and you can see motion, but you can't see time. So give motion a bit of priority.

 

Although speed is stated in, for example, MPH or per second or per day etc. these are just units that count the number of real events, like clock ticks or sunrises etc. I.e. speed is a comparison of change in location with change in something real, like a clock´s hands, not to something that cannot be observed as it does not exist (time).

 

@BillyT
That's an interesting way of looking at it.
Not sure yet, but I'm coming over to your way of thinking.
Yes, time might be a useful notion for explaining things and performing maths with data, yet not exist.
We express relative movement in time and space in the same way that we express weight in grams,
but "grams" as something independent of human experience does not exist.

Would you say space exists?

@Everyone else.
Before BillyT claims me as a convert, has anyone got good objections to this position?

 

Almost of these references prove, is that some really smart people like thinking about science fiction, just as much as the rest of us.

 

Have a look at the watt balance section of the wikipedia kilogram article:

...The Planck constant defines the kilogram in terms of the second and the meter. By fixing the Planck constant, the definition of the kilogram would depend only on the definitions of the second and the meter...

I'd say it's going a bit too far to say "time does not exist". See above where I said time exists like heat exists. Touch a hot stove and you get burnt. That's real enough. So are my grey hairs.

I don't mind people thinking about science fiction. But I do mind when they present it as science. In my humble opinion really smart people don't peddle time travel. In my humble opinion really smart people understand why it's science fiction.

 

Because you have not specified 'where' it occurs. The spatial 'where' given is only relative to an 'object' that has moved since the last observation. If you open up the light clock and unfold the light path, it tells you how far the 'object' has moved relative to light speed. The clock is measuring light distance, but labeled as 'time'.

 

Yes. It has serveral properties, two of which can be measured in the lab and do, just a Maxwell predicted, let you calculate the speed of light in vacuum from these lab measurements. Also electrons and positron pairs pop up in space (That is 1.022 Mev from nothing but only for the duration that the uncertain principle delta T x delta E permits) unless that happens just at the no escape boundary of a black hole which "swallows" one member of the pair. When that happens the other lives long time adding 0.511 Mev to our non-black hole part of the universe and reduces the mass energy of the black hole correspondingly - an over simplified POV about "evaporation of black holes" that really needs math few can follow to do correctly.

Also as space has at least three dimentions, not only the one the time coordinate has, so you cannot do the trick I did earlier to eliminate space from all the equations describing the universe. I.e. you can formally prove time is just a convenient coordinate, but not do that for (x,y,z) coordinates of space.

SUMMARY: Space has at least two lab measurable properties (possible even mass via average mass associated with the vacuum polarization pairs?) but time has none. Time has no color, no stiffness, no mass or mass/ second, etc. - none. Unicorns have more properties than time does and indeed, may be pulling plows on some distant planet as I type.

 

It seems that through exposure to the popular media of today, even respected scientists sometimes explore the fantasies of science fiction from the perspective of science. Sometimes that is driven by nothing more than money and fame or public exposure and sometimes by a desire to insert at least some measure of science in what, is science fiction, or popular public entertainment.

Sure there are a few almost fringe prepublication papers, that seem to approach things like antigravity, time travel and perpetual motion, as if they were serious. Even a few published in respected journals. Some may even be deluded into thinking such are serious pursuits, but most are no more than attempts to cater to the Scifi appetites of the lay public.

Another thing to keep in mind is that there are sometimes differences between honest theoretical explorations of how the theories we currently depend on diverge from the reality we experience, and explorations of their descriptions and predictions of reality.

Sometimes exploring the fantasies that seem to emerge from a theory can tell us as much about how well it describes reality as restricting our explorations to what we can currently see and measure.

Time travel is a very good example.

 

Hi Farsight,

By this, I guess we can assume that you consider yourself "really smart". That's fair enough, but may I ask how you've reached this conclusion, in the current context? From what I've gathered from your posts here

• You believe you're a more competent physicist than most professionals.
• You don't hold any physics qualifications beyond high school.
• You openly accept that you dont understand the details of many of the papers you cite (e.g. basic details of Einstein's general relativity are way beyond your grasp).
• You have no record of publishing physics papers in reputable journals.

Could you help me reconcile these points. I would love to have your confidence, as would many of my colleagues who work in academia! Many thanks.

 

I don't see your problem here. That is exactly some physicists speculating about time travel from time to time, and I see nothing wrong with it. Criticising the idea of time travel is fine - personally, I don't mind people exploring the idea but I wouldn't bet on it actually going anywhere myself. But I get the impression you'd like to see it practically censored and treated as a taboo subject. That is not a healthy, open minded attitude. Your negative reaction to the whole idea just seems too emotional for my taste.

Huge problems for whom? And what sort of huge problems anyway? It's certainly not a huge problem for any physicist, because we always have detailed mathematical formulations of physics that we understand and can fall back on and test. One physicist might give a mathematical description of a physical system evolving, say in a paper, and loosely refer to time "flowing", but because another physicist reading the paper will have the mathematical description, they will always have the capacity to disagree with the original author's choice of words.

I don't know about you, but when I read a paper it is with the aim of understanding the essential content and concepts and concrete results of the paper on my own terms, and not just to memorise the author's catchphrases. I have the same experience with all the physicists I work with: they're all fiercely independent people who like thinking about things in their own way.

How is that a useful measure of anything? Simply looking at the number of Google hits I get isn't going to tell me who is saying these things, how seriously they mean it, how many of them are actually educated in physics, etc. More importantly, what about all the physicists and people not talking about the flow of time?

Besides, your assessment simply doesn't square with my own experience, and I am speaking as a physicist who works in a physics research environment in a group that collaborates with other physics research groups around the world. I unavoidably interact with other physicists on a regular basis and I'm simply not seeing this "cult" of belief in time flowing that you seem to think exists. The status of the idea of "time flowing" in physics probably falls in the classic "ask two physicists and you'll get three different answers" bin.

Are you disagreeing with the content of the paper or just the title?

You make me wish I could actually make you work in a theoretical physics group with international contacts and collaborations for a couple of years.

So time doesn't fundamentally exist like heat doesn't fundamentally exist. I think you'll find that idea breaks down if you take it too seriously. The problem is that the whole idea of motion itself basically presupposes time. While it's true that things like the t coordinate we use in physics and measures of time such as the second are man made conventions, the idea that "change" can occur in the first place is not, and I would argue that is really the essence behind the idea of time. At least the way I see things, you cannot talk about change or motion without implicitly acknowledging and presupposing time. You also have the problem that time has some basic but important properties associated with it (the sort of thing a mathematician might like to call "topology"): for example, in physics it has special significance when things happen simultaneously (same place and time) or events are "infinitesimally" separated from one another, and you give no explanation of how you recover this.

Special relativity also puts another spanner in the works for you here, since according to relativity there are many different possible measures of time that are all experimentally indistinguishable and equally good as far as physics is concerned. That's a problem because one inertial frame's measure of time is actually a mixture of another frame's space and time measures. So of all the different but equally good sets of x and t coordinates we could use in physics, which x coordinate would represent "real" space and which t coordinate would be entirely this "derived" time of yours? I see only two conclusions here: either you have to abandon your idea in light of relativity, or you have to go back to the pre-relativity days of imagining there is some absolute but undetectable state of rest in which the x coordinate would be measuring only space and the t coordinate would be measuring only your "derived" time. General relativity only makes this worse.

 

on post 74, I forgot to mention two other measurable properties of space. It is quite stiff, but a large mass, like the sun, can "bend" it and it can support "virtual EM radiation" that can have its longer wavelenghts "shorted out" between two closely separated conducting plates with the unbalance external EM pushing them together with a very tiny but measurable force - I forget the name of it just now. (As long wave lenghts don´t have much energy or make much pressure so to be measurable the plates must be very close together shorting out wave lenghts equal to their separation or longer.)

 

Hi guys.

It's hilarious and serious all at the same time.

For the serious part, it's the double standard that gets me. For instance, Mazulu ponders and tries to make experiments on his 'frequency-shifting' idea for possible manipulation of space to produce gravity effects, and he is called a 'crank' delusional fantasizer. But when a professional physicist writes reams and reams about 'time travel' fantasies in the face of known theoretical and practical limitations to such speculative notions, he still retains his 'professional' status and is not immediately called a 'crank' delusional fantasizer (as he should be if what is good for the goose is good for the gander). That is what rankles when reading rationalizations as to why one is legitimate and one is not.

For the hilarious part, I will just observe that it appears the reason why professionals still write reams of time travel speculation is because they have nothing better to do. By that I mean that the collection of partial theories (however practically useful they may be within their partial domains of applicability) have hit a brick wall where 'consistent unification' is concerned, and they themselves have plateaued in the cosmological 'explanations' which explain very little but merely hypothesize still about unknowns upon which the theories depend. In short, it seems that time travel exercises are just a 'holding pattern' while they wait for something big 'to break' that will finally make sense of all the disjointed and iffy assumptions/models of the universe to date. It's like 'escapism' for the frustrated professional who hasn't anything more to offer. To relieve stress/frustration of going nowhere, and to distract from the impotence of current approaches to the universal reality interpretations. The ordinary joe goes to the movies; the medico goes to a golf course to hit a little ball around; and some professional physicists sit and write about time travel fantasies. No problem with physicists relieving stress and distracting the public with these professional fantasies....except for that double standard I spoke about above, which treats their musings as 'legitimate' speculation while others doing their own speculation on what interests them are called 'cranks' for doing essentially the same sort of thing.


To whom it may concern: Nothing personal. Just making my objective observations on this aspect.

Still, it takes all kinds, even in the professional ranks.....double standards notwithstanding. End of opinionated rant.

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As I don´t think time has any properties I disagree. First, AFAIK "topology" is concerned only with shape and really just the connectivity of it not the sizes. (People and donuts have same doublely connected shape to a topologist.)

Secondly, as I think you know from your later mention of the mixing of time and space coordinates when describing how events in one frame would be described in another frame, there is no special aspect of "simultanity" as you seem to assert. Many things are the same in all frames. E.g. The topology of an object is the same for all frames and H2O freezes at 0 C in all, but lengths and time intervals say between two LED flashes, measure by local clocks also change (don´t agree) and can be simultaneous in only one frame. These difference are just in how one frame describes meter sticks and light flashes, of another frame, not real changes in one frame.

Please try to explain to me what property time has in more detail that are not just descriptive changes with POV when frame changes. I.e. in one frame what is a property of time?