Anyway, so while I will spend some hours staring at a sign saying 'Your seat cushion can be used as a floating device', here is a poll for you addressing one of my more permanent confusions. That being the question whether or not the past does exist the same way as does the present, as does the future. Having been taught time is a dimension since I was ten or so, combined with my disliking of the measurement process in quantum mechanics, I tend to believe the past, present, and future 'exist' equally, and our perception of a 'now' is an illusion that comes with consciousness. However, I then recently came across this article Is There an Alternative to the Block Universe View?, which starts with saying
"If one can talk about a widely (explicitly or implicitly) accepted view on reality it is presentism - the view that it is only the present (the three-dimensional world at the moment `now') that exists. This common-sense view, which reflects the way we perceive the world, has two defining features: (i) the world exists only at the constantly changing present moment (past and future do not exist) and (ii) the world is three-dimensional."
Which left me wondering how widely accepted this view really is, and how far I'm a victim of my education. So what do you think? I know the question is somewhat fuzzy given that I don't explain what I mean with 'exist'. Let me put it like this: I guess most people would agree that the present moment 'exists' in some way. So without explaining in exactly which way it exists, let me ask whether the past and future exist that same way.
PS: The results from our last poll on the Photic Sneeze Reflex are here. There were 321 people who voted. About 62% of men (56% of women) said they do sneeze when looking into bright sunlight after having adapted to the dark. I didn't realize this was so common! The ratio of men to women who voted is about 6.5.
> I guess most people would agree that the present moment 'exists' in some way.
ReplyDeleteYes, I agree.
>So without explaining ... let me ask whether the past and future exist that same way.
Although you "do not explain", I would think that past and future do not exist the same way, otherwise why would you feel the need to distinguish past and future from the present and why would the question even come up?
The fact that the "now" is real implies that the past and future must also be real in exactly the same sense as the "now". This is the case because the physical state of the universe in the future or the past can be mapped to the present state.
ReplyDeleteIf O is an observable, then the operator
O(t)= U-dagger(t) O U(t)
with U the time evolution operator is the corresponding observable for the future a time t later.
In this philosophical question about the reality of the past and future the practicality of actually being able to measure O(t) is irrelevant. What matters is if reality conformes to the formalism of quantum mechanics, allowing one to measure
O(t) in principle.
E.g. we can measure who will be the next US president. Clearly we can measure who is he current US president. This means that there exists a (very complicated) observable for this and thus also for the time evolved observable.
If we actually were to measure the next president of the US, the wavefunction would collapse into a state that will evolve exactly to the measured future state.
> e.g. we can measure who will be the next US president.
ReplyDeleteCould you please measure now for us the outcome of the November election?
8-)
Wolfgang,
ReplyDeletebecause we're all human beings and have to cope with the burden of consciousness.
Count,
If there was no measurement process in qm, yes. However, the question then persists why do we experience the 'now' as being somehow different from the 'then', and whether the fact that the present moment being somehow special and the feeling that time 'flows' does not enter our theories is a lack of these theories, or, as I said above I believe, an 'emergent' feature due to our consciousness and the ability of our brains to store a memory (of the past, but not of the future).
Best,
B.
reg the president. The possibility to make predictions within a system doesn't only depend on it's deterministic evolution and the knowledge of initial conditions, but also how chaotic it is.
ReplyDeleteWhen you fly up look down. See the past? Cities! The past uniquely exists.
ReplyDeleteThe future is undetermined. Will you meekly accede to Homeland Severity warrantless search and seizure? Will you draw a knife and slash throats instead? Wholly different futures pivot on the flutter of a butterfly's wing.
http://www.fourmilab.ch/fourmilog/
25 April 2008
http://science.nasa.gov/headlines/y2006/images/longrange/butterfly.jpg
If the sun is revving up for a really big whoopsie, the butterfly is moot - global determinism versus local freedom of choice. Local evolution is important to the locals.
A chaotic system has a determined future. It is just very sensitive to distubances in the initial conditions (the butterfly).
ReplyDelete> the burden of consciousness
ReplyDeleteI assume that once you would be able to better specify what you mean with 'consciousness', it would be much easier to discuss your question about past, present and future...
"Exists" as usually used implies a time element, because things come into and pass out of existence. So, the past existed, but no longer does, and the future will exist, but does not yet.
ReplyDeleteIs "the event of Bee's birth" eternal? From a classical, deterministic point of view we could probably answer yes. Even when the event was in the future, we could legitimately talk about it.
Once Quantum Mechanics comes around, I'm not so sure we can talk about definite future events; "A or not A" doesn't hold in QM unless there is the suitable measurement situation, and I feel we have to be careful. Maybe I'm wrong. I don't think QM puts any such constraint on the past.
Hi Bee, when in flight, if the clouds are being bombarded by cosmic rays, you get to see the cotton wool, or brain effect?..pattern of cloud roof is like that of cloud chamber, the patterns can be identical.
ReplyDeleteWell there can be no part of the past wherby any change is occuring, the past is not available for change of any kind, thus is not like the present time or future.
The present "now", interestingly has no part of it that can not have any change occuring, one can slow things down to a finite crawl, but there will be at the least a little change occuring, nothing can be at absolute unmoving stillness?
Have a nice break, and best to you and stefan, paul.
Well interna
ReplyDeletewe can allegedly see ten billion years into the past
but I'm darned if I can SEE where I put those keys yesterday
I would say that all matter is moving thru time and therefore changing and growing or decaying as bodies do ...
and we can recall past memories, though we cannot 'time' travel (yet)
whether there is something in us that exists in the two year old or twenty year old we once were I cannot say - I only know for sure that there is something of the twenty year old still in me.
PS - Fortunately no one NOW can call you on the mobile yesterday
Oh, I don't know. My guess is that they all exist in the same ways, but our experiences of them are different. Time affects all things, not just those us with a consciousness. Speaking of flying, and sort of what uncle al was saying, when you fly across time zones you are advancing into the future or returning to the past, depending on the direction of flight and in relation to the people on the ground. And the future will always be, even if none of us are here to experience it. And every time we look at the stars we are only really seeing the distant past. Anyway, have a safe flight and a good visit home.
ReplyDeleteHave you read any papers on "the problem of time," in a general-relativistic sense? As far as I can tell that's the 'right' way to look at such conundrums. And just like most 'right' ways of looking at things (IMO), the key seems to be realizing that concepts such as future/past/etc. are much more so byproducts of one's local reference frame than they are of the underlying "universe" or "theory of everything." You can see some of this in special relativity already, of course.
ReplyDelete(Actually, assuming that nobody's moved around since last summer, Hans Westman in the office one door down from yours does some research in this area. Could be fun to ask him for an introduction.)
On a level more in line with my intuition/education/everyday physicist-perspective, I'd say that the past/present/future all exist in exactly the same sense; however, I would not phrase the distinction as arising from "consciousness" in any way. Because to me that implies that with enough tweaking of the consciousness mechanisms (via drugs, surgery, or future technology---whatever) you would be able to make yourself experience time backwards. And (in this everyday POV, mind) it seems fairly clear that time flows in a certain direction, at least from the point of view of a single 'particle' (or human).
This seems to be all about defining what one means with "exist". I can think of sensible definitions according to which each of the answers would be correct.
ReplyDeleteAn excellent question from the Institute.
ReplyDeleteI clicked "other" because I think that the present exists (otherwise free will doesn't work, and without free will, why should I have opinions about physics), and the future exists (this is necessary in order for Feynman's path integral calculation technique to be made ontological, different prospective paths need to simultaneously exist in order to interfere), but that the past does not necessarily exist (if it exists, why is it not alterable?).
First, time as we experience it is not something that can be modeled by mathematics. Yes, despite your hearing about d__/dt etc. and all that. Of course we can create functions and graphs and have the variance of one quantity with respect to another, but that is not inherently about "time." Time has to be put in "by hand" because otherwise you are just talking about "configurations" of points, worldlines, etc. Hence some think that time "is an illusion" which I consider a copout. I accept it as I experience it, and it it's an illusion than consciousnesses is just that much more special to be able to manifest something that doesn't "make sense" in physical and mathematical terms.
ReplyDeleteRemember, that physical existence isn't logically definable either (modal realism.) I'm not saying MR is true, only that strict logic doesn't really allow distinction between "models" and "real stuff."
As for logical fallacies, always remember that a fallacious argument doesn't have to lead to false conclusions. (Thinking it does might be called "the fallacy in reverse.") It is just unreliable, such that if true, it is a lucky coincidence. For example, consider a dog thinking: "I have four legs, dogs have four legs, therefore I am a dog." Well, he got it right that time, but a cat using the same fallacy of converted conditional would end up wrong.
Hi Bee,
ReplyDelete“I tend to believe the past, present, and future 'exist' equally, and our perception of a 'now' is an illusion that comes with consciousness.”
Well Bee I find we see a thing or two the same way once more. Not too surprising as most in the poll do as well. I was surprised that you felt consciousness played a role in all this which is the same way I look at it. The surprise is not so much that I do, yet rather you as well. I wonder how many physicists of the theoretical bend share this perspective? I would think very few, then again how would I know. There was also once a famous contemporary writer who wondered the same shown as follows;
“Time present and time past
Are both perhaps present in time future,
And time future contained in time past.
If all time is eternally present
All time is unredeemable”
T.S Elliot - Burnt Norton (1935)
Best,
Phil
P.S. I’m confused by the problem you have with the boredom of flight time or do they not allow you to use laptops anymore on overseas flights?
Yeah, I don't see how the past can be real. But then, I don't see how the future can be either. I guess I'm with St Augustine on that one: In whatever manner, therefore, this secret preconception of future things may be, nothing can be seen, save what is. But what now is is not future, but present.
ReplyDelete[a] Do note that arguments based on *special* relativity should be viewed with caution since generic cosmological spacetimes don't have boost symmetries. Using SR to establish the "existence" of the past/future is therefore something that works only locally. As we go back in time, "locally" contracts to smaller and smaller sizes. Eventually the scales get so small that it becomes meaningless to speak of the existence of past/future. Combined with quantum mechanical effects, this is the "emergence" of time.
ReplyDelete[b] Note in this connection the bizarre nature of the Hamiltonian formulation of GR. Take a 3-dimensional space on which is defined a symmetric tensor K_ab *which has no meaning*. Then use the Einstein equations to *construct* a 4-dimensional spacetime in which it *turns out* that K_ab was the extrinsic curvature etc etc etc. In short, the 4-dimensional spacetime "emerges" from a basic 3-dimensional structure, which is more fundamental. In that sense, past/future are *implicit*
in 3-dimensional space.
[c] Summary: my answer to your question is: I have no idea.
The idea that the present is some kind of illusion goes back at least to Einstein, and it's popular with physicists, but it seems dishonest to me. Physicists prefer to believe that it's an illusion because there is no place for it in the usual theories. To quote Hamlet, though, it's just possible "that there are more things under the sun than are dreamt of in your theories.
ReplyDeleteThe problem with shuffling the present into consciousness and psychology is that it doesn't solve anything. If consciouness can conjure up the present, how does it do it? With physics or some kind of magic psycho juice?
And if it's magic psycho juice, what is the physics of that? We can imagine that the division of time into past, present, and future is an illusion, but don't forget that you can't do any physics or even plan your breakfast without it.
Martin says:
ReplyDeleteThe past, present and future must be three (or at least two different "things"), because
- The past is what already has happened and cant be changed in any way.
- The future is what hasnt happened yet and might be influenced (by what- or whomever).
- The present is at least the border between past and future.
I strongly believe (and i usually *believe* close to nothing) that any scientific theory that looks at past, present and future as the same "thing", is too "simple", no matter how useful/complicated/proven it is.
Hi Bee,
ReplyDelete...then recently came across this article Is There an Alternative to the Block Universe View?....Which left me wondering how widely accepted this view really is, and how far I'm a victim of my education.
I think few physicists have the courage to ask this. Another who did was John Bell. His book, Speakable and Unspeakable in Quantum Mechanics, has a section titled "How to Teach Special Relativity."
He argues we should not overlook the Lorentz-Poincaré interpretation of relativity, where time plays a privileged role. Due to the measurement problem you mentioned, he also advocated the de Broglie-Bohm interpretation of quantum mechanics. His book also notes that such a quantum mechanics (which does not depend on human observers) seems to require this earlier version of relativity.
Lorentz-Poincaré relativity is based on a preferred reference frame, where time is treated as a separate one-way parameter. Of course in Minkowski (block) space-time, time needs to be interchangeable with its 2-way spatial dimensions. How then do we experience 1-way time? Some say, if time goes backwards, your brain does too, so everything works. But this overlooks the fact that forward and backward time are different, from the perspectives of thermodynamics and quantum mechanics. And Minkowski space-time by itself contains nothing which can represent or describe that difference.
Feynman recognized the problem. Based on Wheeler's idea of anti-particles as particles moving backwards in time, he proposed once that maybe time goes forward because particles outnumber anti's. But it has never been clear how that might work. (What are the particles going to do -- take a vote? What if the vote is 50-50?) As far as I know, that idea has never gone anywhere.
Parameterized quantum-mechanics deals with the problem by introducing an extra 1-way parameter, in addition to the 2-way time of Minkowski space-time. However this paper by Hartle notes it may be impossible to incorporate such an extra parameter into general relativity.
Domenic Denicola wrote, "Have you read any papers on 'the problem of time,' in a general-relativistic sense?" I think Hartle's paper is a good one.
What I like about LQG is that it acknowledges existence of "the problem of time." But I disagree with the proposed solution -- to get rid of ordinary time completely. I think Einstein and Minkowski threw the time baby out with the bathwater, and that would be throwing out the bathtub too. If this means that, like Lorentz and Poincaré, I'm a flawed person who "doesn't get" relativity, so be it.
Best wishes, Kris
CIP,
ReplyDeleteWe can imagine that the division of time into past, present, and future is an illusion, but don't forget that you can't do any physics or even plan your breakfast without it.
Beautiful!
Hi Kris,
ReplyDeletePast, present and future can all exist in one place and that place being configuration space. The difference being is in this place all is what we would call potential. Therefore to hold to Einstein’s view of things is to consider that the now is a preferred frame within such a space. The question then is what forms the preference?
Best,
Phil
To address the question of whether time exists in the first place, I believe that you would have to address the nature of inertia. Since after a moment's thought there are only 2 possibilities for defining time: A- Time is movement. B- Time is related to movement; considering that inertia is the most "intrinsic" movement one can imagine, I strongly believe that time and inertia are intertwined entities.
ReplyDeleteThe following is just a simple thought experiment that undoubtedly deserves more elaboration, but from it you'll see what I am at.
Suppose an universe in which there exists only one spinning body or particle, which cannot access information from outside an isotropic/uniform box to which it is confined.
If inertia were a property that depended on the existence of other particles in the universe, ie, if it were not an intrinsic property of the body, the spinning particle, being completely alone in the universe, could not tell that it is spinning, and as a consequence it could not tell by any means that time exists (ie, passes). Even if the universe by itself evolved in such a way (or had some property) that could change the spin rate of the particle, the particle could not "tell" it, since it would not bulge, given that the universe was empty except for the existence of that particle, and in this case it is assumed that inertia depended on the mutual existence of other particles. If you included more and more other particles in the universe, however, the original body would bulge, and the degree of the bulge could change, e.g., by the change of the configuration of the other particles. That change would measure time.
On the other hand, if inertia were an intrinsic property of the body (did not depend on other particles in the universe, but only on the particle itself), the alone-particle-in-the-universe could in principle tell that time exists, but in order to tell it, its spinning rate would have to change, in order that its bulge changes, and that would indicate the passage of time. That would presume some property of the universe that acts as an effective torque on the particle as the universe evolves. It would then bulge, even if it were the only particle in the universe, and time would pass.
These are of course unrealistic or too simple thought experiments, but I believe there is some deep connection involving time and inertia (and both in a large-scale sense involving the nature of the universe itself). There is also, of course, quantum mechanical issues one could argue about (or even quantum gravity issues, for that matter, also involving thermodynamical issues)... Time is a great mystery.
The division between "past", "now" and "future" is, IMHO, a human trait, which nonetheless embeds the whole construction of our theories and how we make measurements to confirm them. Whenever we move farther and farther from our common sense experiences more and more that division of time ("past-now-future") becomes more and more peculiar. This is an indication that nature's substratum might operate in a different manner.
Christine
Bee, thinking a bit more about the argument I was making yesterday, I should have mentioned the "Strong AI Assumption", i.e. the idea that consciousness does not depend on the way it is implemented.
ReplyDeleteAs Marvin Minsky once said, a big analog computer simulating someones brain would have the same consciousness as brain it is simulating.
Now, because the laws of physics conserve information, the future as well as the past is implemented in the "now", albeit in a very scrambled way.
So, we have to admit that President Obama, President Hillary and President McCain all exist "now". We can't observe them in practice as that would involve a joint quantum-mechanical measurement of all the particles in the Earth. But what matters is that they all subjectively experience being in the White House.
This relates indirectly to the nature of time, in the sense of how rotation fits into the idea of "velocity." You have heard that rotation can be considered relative, especially in the sense of coordinate systems. But consider: let's assume that velocity is relative but at least unambiguously "real" per that consideration. That's a reasonable take on "relative velocity." But if so, then points on a rotating body are in definite relative velocity with respect to each other! Isn't that a bit fishy?
ReplyDeleteBTW, I just don't accept the "block universe." We should accept that we have a weird universe in which offbeat, mathematically fishy aspects like real time, real randomness (REM that mathematics is a deterministic system and that so-called random variables etc. are either just about the averages themselves, or must have actual results "put in by hand."), real conscious experience, and even realness in general over and above being a platonic model, are just the way it is. If abstractionist prissies don't like it, that's their tough luck.
In response to this post, I can't help but think of the Stephen King short story, 'The Langoliers'. In any case, have a nice flight! ;)
ReplyDeleteBee:” Having been taught time is a dimension since I was ten or so, combined with my disliking of the measurement process in quantum mechanics”.
ReplyDeleteI have two questions for you:
1)what do you mean “the measurement process in quantum mechanics”?
2)do you dislike it also since you were ten or so?
I believe that the following:” This common-sense view, which reflects the way we perceive the world, has two defining features: (i) the world exists only at the constantly changing present moment (past and future do not exist) and (ii) the world is three-dimensional” is a quotation of Mr.Petkov. It belongs to your previous post “Logical Fallacies”: 1) this view is not common-sense; it is non-sense; 2) it is very exotic individual POV of the writer which to best of my knowledge is not shared by any physicist.
wolfgang:” e.g. we can measure who will be the next US president."
It is not what is stated by Count Iblis; it is not what was defined by J.von Neumann as R-process; it is not what was explained in details by R.Penrose.
Bee:” why do we experience the 'now' as being somehow different from the 'then', and whether the fact that the present moment being somehow special”.
QM time dispersion must shrink to delta t=0 to satisfy the requirements of SR as was explained by A.Einstein at 5th Solvay.
Regards, Dany.
Hi All,
ReplyDeleteThanks so much for your interesting comments! I didn't quite expect this 'Interna' would receive so much attention. I think I will have a follow-up post which will address some of your questions clarifying my opinion (but I think some pictures would be helpful, so the comment section isn't such a good place). I also have some more comments on that article I mentioned above (it's interesting, but despite me not being a 'presentist' I don't agree on the conclusion) that however will need a longer explanation. Best,
B.
Hi Wolfgang,
ReplyDeleteI assume that once you would be able to better specify what you mean with 'consciousness', it would be much easier to discuss your question about past, present and future...
What consciouness is, and how it can be defined is an interesting question, but isn't the point here. The point is simply that everything we experience goes through our brain, and is thus not only subjective but also much more complicated than the fundamental laws of nature. All I wanted to say is that whether we like it or not, we have this extra 'baggage' (as Tegmark calls it), and I think that our impression that the present moment is somehow special is not a fundamental property of nature, but a consequence of that baggage. I hope I can make the reason why I think so clearer in the next post.
Best,
B.
Dear Arun,
ReplyDeleteYes, I tend to agree on that. In the standard interpretation the fact that the measurement process in QM is non-deterministic implies the future is 'open' whereas the past isn't.
Hi Quantum Ranger
Well there can be no part of the past wherby any change is occuring, the past is not available for change of any kind, thus is not like the present time or future.
I doubt you can prove that you can change the future, or that we have a free will. So how do you justify 'there can be no ..., thus...' ?
Best,
B.
Hi Dany,
ReplyDeleteI have two questions for you:
1)what do you mean “the measurement process in quantum mechanics”?
2)do you dislike it also since you were ten or so?
1) I meant it in the operational sense in the standard framework of picking an eigenvalue with the probability belonging to it, which I find rather unsatisfactory as to what actually constitutes a measurement in practice that justifies this procedure.
2) No, I didn't learn qm until high school or so. I had an instantaneous disliking of Feynman's book 'QED, The Strange Theory of Light an Matter'. (Not saying it's not a good book - it is. I just didn't like it for I think (if I recall that correctly) it doesn't address any of these underlying questions about quantum mechanics. Instead it has repeated statements of the kind don't worry if you don't get it, you don't have to.)
I believe that the following:” This common-sense view, which reflects the way we perceive the world, has two defining features: (i) the world exists only at the constantly changing present moment (past and future do not exist) and (ii) the world is three-dimensional” is a quotation of Mr.Petkov. It belongs to your previous post “Logical Fallacies”: 1) this view is not common-sense; it is non-sense; 2) it is very exotic individual POV of the writer which to best of my knowledge is not shared by any physicist.
I don't think the author of that paper knows very much about physics. You notice it from his explanations about Special Relativity. The biggest part of the paper is actually a rather trivial statement about observers in Minkowski space that he explains very complicatedly.
I should maybe have mentioned that I don't agree on the conclusion in that paper, but I will explain the reason for that some other time.
However, the paper isn't as bad as these opening lines may suggest in that the author doesn't actually argue that whatever he believes is common-sense is of importance, so there's no fallacy since he doesn't use this opinion of his to justify something. In fact, he attempts to make a scientific argument. I don't know why he used this introduction, I find it rather unwise to start with appealing to common-sense (especially since it turns out that at least on this blog the sense isn't that common).
Best,
B.
Hi Kris,
ReplyDeleteSome say, if time goes backwards, your brain does too, so everything works. But this overlooks the fact that forward and backward time are different, from the perspectives of thermodynamics and quantum mechanics. And Minkowski space-time by itself contains nothing which can represent or describe that difference.
The question why time has an arrow that points this way and not that way is certainly interesting, but it is a different question to whether it is only the present moment that exists. Not saying these two issues are unrelated though, I just think they have a different origin and entangling them might not be helpful. Best,
B.
Hello
ReplyDeleteThere is no past, present or future. There are only events upon other events and related to other events. They evolve not in time and space but in relation to other events and "themselves".
Rovelli said:
"We need to free ourselves from the prejudices associated with the habit of thinking of the world as inhabiting space and evolving in time".
Regards
Hi Giotis,
ReplyDeleteDefinition of dogma: "A religious doctrine that is proclaimed as true without proof." How is this any different?
Dr. Rovelli's statement would carry more weight if he had actually achieved some of the lofty goals he has attributed to LQG.
As Feynman pointed out at the end of his Nobel Prize Lecture, many viewpoints are possible in physics, and its hard to tell which may help us make progress. Maybe even one which is not so fashionable as yours.
Hi Phil,
ReplyDelete...what forms the preference?
As a preferred frame for the universe, Einstein used to speak about "the fixed stars." If there is one, the reference frame singled out by the cosmic microwave background might be a good guess. More local preferred frames have also been proposed such as of the that of the "Great Attractor."
The WMAP quadrupole CMB anomalies are interesting. Since those are aligned with the ecliptic, it's conceivable those might be associated with preferred-frame effects involving Earth's motion.
Cheers, Kris
Hi Bee,
ReplyDelete“I meant it in the operational sense in the standard framework of picking an eigenvalue with the probability belonging to it, which I find rather unsatisfactory as to what actually constitutes a measurement in practice that justifies this procedure.”
Why you choose something unsatisfactory instead to what actually constitutes a measurement in practice? I prefer E.P.Wigner definition as the universally valid process of acquisition of knowledge. If system under test obeys laws of the classical physics then it is classical measurement and if it obeys QM then I would say that it is quantum measurement.
“I just didn't like it for I think it doesn't address any of these underlying questions about quantum mechanics. Instead it has repeated statements of the kind don't worry if you don't get it, you don't have to.
What wrong with Feynman’s integrity? He talk about the theory that hasn’t has been constructed yet.
“I don't think the author of that paper knows very much about physics... In fact, he attempts to make a scientific argument.”
There is internal inconsistency in your statement. The author should attempt to make a scientific argument in area of his competency (sex, I guess, would be better). However, I didn’t read a paper and don’t intent to do that.
Regards, Dany.
If you were a conscious photon I think you could experience a full past and future as your present. We kind of only I think experience a present state (that includes a memory of the past) because we are constantly repicking the part of the worldline that goes into the future. It's like we only get to branch at the present while the photon can branch anywhere along it's worldline. I may not be saying this exactly the way I'd like to.
ReplyDeleteHi Dany,
ReplyDeleteWhy you choose something unsatisfactory instead to what actually constitutes a measurement in practice? I prefer E.P.Wigner definition [...]
I say I find X unsatisfactory, and upon asked clarify with X I mean soandso. You then suggest to understand X instead as thisandthat. Similarly, had I told you I don't like getting up early, and clarified with early I mean before ten a.m., you could suggest I should understand early as being before six a.m. But I still wouldn't like getting up at nine. So I don't actually know what you are saying except for that you like Wigner's definition (six a.m.).
I didn't say there's anything wrong with Feynman or his book.
There is internal inconsistency in your statement. The author should attempt to make a scientific argument in area of his competency (sex, I guess, would be better). However, I didn’t read a paper and don’t intent to do that.
I don't see what's inconsistent with what I wrote. I was describing my impression of the paper since you criticised the paragraph I quoted and I meant to clarify it doesn't go on in this style. I have no problems with authors who write papers about topics not in the area of their competency. However, I also don't see in how far this is relevant for the topic.
Best,
B.
Hi Bee,
ReplyDeleteGenerally speaking, I wrote my comments to present my POV and to discuss/compare it with others as others. I have no intention to force you to accept my POV or convince you to change yours.
“I didn't say there's anything wrong with Feynman or his book... Not saying it's not a good book - it is. I just didn't like it.”
I supposed to know to read.
“Similarly, had I told you I don't like getting up early, and clarified with early I mean before ten a.m., you could suggest I should understand early as being before six a.m. But I still wouldn't like getting up at nine. So I don't actually know what you are saying except for that you like Wigner's definition (six a.m.)”.
No. I get up no later than five a.m. (honestly). I didn’t say you should get up at six. I don’t think I am that stupid (W. Pauli was getting up not earlier that 12 p.m.).
To be more serious, we discuss the theory of measurements. The original formulation was suggested by P.A.M. Dirac and J.von Neumann. The central problems were formulated by W.Heisenberg, E. Schrödinger and A. Einstein. In my opinion the best summary is presented by E.P.Wigner, AJP, 31, 6 (1963).
Nobody (you included) is required to accept that.
Regards, Dany.
Hi Dany,
ReplyDeleteSure. Thanks for sharing your point of view. Best,
B.
PS: Living in North America with most of my friends and family in Europe, I've come to realize 'early' is very relative :-)
OT: You don't have to post as 'anonymous' even if you don't have a blogger account (or one of the other options). If you choose 'Name/URL' you can enter a name (you don't have to enter an URL). I'm suggesting this because it is much easier to follow the comment section if the posts start with 'X said...'
ReplyDeleteHi Phil,
ReplyDeleteRegarding the flight time, it's not the boredom, but the sitting. My version of hell is an economy seat on an eternal flight to nowhere. Air Canada doesn't only allow laptop use, they now even have power outlets and USP ports! I hardly ever use my laptop on airplanes though.
Regarding consciousness, I hope it will become clearer in the next post what I meant. I'll be interested to hear what you think. Best,
B.
Hi Carl,
ReplyDeleteWhere in Quantum Theory is the past fixed by the present; for uncertainty would imply that the present remains uncertain as does the future. Uncertainty in the strict sense is not as a consequence of ability, yet rather a restriction of nature. So if the present remains uncertain, what then has the past not to be so? Wheeler’s delayed choice would appear to imply that the past can be affected (or rather formed) in the future and therefore suggests to me the only way around this is that all then is holistic in nature, including time. Does this then dismiss free will; no, for only if you deny the holism would that be necessarily true.
Best,
Phil
Hi Kris
ReplyDeleteRovelli's statement is based on GR not on LQG.
Regards
Hi Bee,
ReplyDelete“Regarding the flight time, it's not the boredom, but the sitting. My version of hell is an economy seat on an eternal flight to nowhere.”
You truly are a Bee; for I must admit when I imagine one it is always in motion. This then leads me to wonder, how you are when you write this blog or read one of the many books you manage to and often post a review? :-) I would also like to ask and of course neither expect nor deserve an answer, if you ever strike up a conversation with the person seated adjacent to you? I must admit I often have and one of the first questions asked mutually is what the other does for a living? I have often wondered if I would respond as you that I was a theoretical physicists (which of course I’m not) if the conversation would progress past this juncture and if so what would form the nature of the dialogue?:-)
I am also now curious as to the content of your continued discussion about you thoughts on the nature of time and how for you consciousness plays a role.
Best,
Phil
P.S. How does a Bee respond to jet lag? :-)
Hi Kris,
ReplyDelete“If there is one, the reference frame singled out by the cosmic microwave background might be a good guess. More local preferred frames have also been proposed such as of the that of the "Great Attractor."”
Yes and yet none of these exist in, although manifest of configuration space. In relation to this, some months back I read Prof. Harvey Brown’s (of Oxford)book entitled “Physical Relativity”, where he discusses the dynamic as opposed to the kinetic perspective of SR and GR. Although his arguments are convincing, he seems to me to have only a vague and might I dare say a confused conception of how configuration space in regards to QM has a role in such considerations.
Of course in as I’m only a novice it should not be a surprise it is I, not he that is confused:-) However, as an admitted and somewhat weak defense, when it comes to the nature and reality of time that for me would not form to be an embarrassment. It is also interesting to note that Prof. Brown is at present on sabbatical at PI and leads me to wonder if Bee may have had a conversation or two with him in regards to all this?
Best,
Phil
Cudgel my brain, but I cannot remember the future.
ReplyDeleteWhatever the stuff of our consciousness, presumably it arose via evolution, which means it is a useful construct for the handling of reality, and so with its sense of time. That is, the lifelines - the sum total of spacetime events involving the ancestors and descendants of creatures with memories extend longer than those without.
Also, presumably, remembering the future either is impossible or else is an evolutionary dead-end or else there is no pathway yet to evolve to such a state.
Some part of our sense of time comes from memories, and probably another part from the fact that our "present" really is a time interval of several hundred milliseconds within which a little or a lot can happen.
The best thing to do in a flight is to sleep.
Arun:Cudgel my brain, but I cannot remember the future.
ReplyDeleteYou just don't remember it Arun. :)
You are the best architect of your own social future. We have previews of it all the time when we project ourselves(some better then others).
You might think we might not of moved, but the seeds had already been planted?
So in that sense, the future is a strange thing when we know the mechanics of the situation i the psychological sense, is a "fundamental part of our ability to choose" how we can become better citizens of what ever place we live in?
It goes back to the questions of what determinism is, in the choices we make subjectively. While we think subjective and philsophically this may be of no value in the science world, some who choose to do things otherwise, do know better.:)
I'd use some quotes, but I'd be referencing historical situations, and if we can't use these to prove our point, then what shall we do, ignore what we send to our past?:)
Hi Bee,
ReplyDelete“I've come to realize 'early' is very relative… You don't have to post as 'anonymous' even if you don't have a blogger account (or one of the other options).”
I apologize if you will consider that off-topic: it is on paradoxes of relativity, anonymity and memory:
1)Anonymity; I know and agree with your arguments on that, but only with respect (relatively) if there exist intention to insult anybody. I have somewhere a blogger account but I lost it (lost identity). Using 'anonymous' I don’t need non-existing memory of non-existing past for the applications in the non-existing future. Using Least Principle it is the shortest path to post a comment.
2)I am intrinsically elementary particles physicist (and according to my professional background) but currently focused on the theory of measurements, information, communication and all that. Consequently, the only thing that interests me is the elementary particle of knowledge. In my subjective ref frame I claim that I know what does it mean “yes” but do not agree with J.von Neumann what is “no”. I guess that for the outsider all that sounds as completely idiotic questions, but behind my words stand entirely the math relations and machinery of the finite dim Hilbert spaces. As a final accord I do not agree with A.Zeilinger treatment of the beam splitter.
Regards, Dany.
Dear Arun,
ReplyDeleteIndeed, this is about the same directions my thougt went, see the recent post. Best,
B.
PS: Anybody noticed that one can now 'schedule' drafts to appear?
My present moment is composed entirely of things from my past lightcone.
ReplyDeleteSpecial Relativity tells me that all observers agree on what events are in my past lightcone.
Special Relativity also tells me that when I try to extend my present moment to a global plane of simultaneity, then it is subjective. Given any two events in this extended present that I consider simultaneous there are observers who will find them in either time order.
From this last observation, some come to the idea that past, present, future all equally exist. But the more robust lesson, I think, is that only the present exists, and that too, at the space-time event where I am. That is the one thing that all observers can agree on.
The reason that simultaneity seems to be a physically reasonable notion is primarily because the earth is tiny and we don't move fast relative to it. If we were regular traversers of intergalactic space, we might be able to come up with a notion of simultaneity from the fact that the universe is homogenous and so everywhere has pretty much the same history, CMBR, etc.
It also seems to me, but maybe at 1:44AM I'm prey to sleepiness errors, that without any invocation of entropy or anything, my past light cone is increasing and my future lightcone is shrinking. i.e., my past lightcone at time t is a proper subset of my past lightcone at t+delta. This fact doesn't require an arrow of time, entropy, QM, or whether future, past and present exist in the same sense or not. An observer has an intrinsic direction of time defined by her shrinking lightcone. If this is correct, then the only remaining mystery is why different observers' shrinking lightcones always point in the same direction.
Will you be passing through Munich by any chance?
ReplyDeleteArun writes,
ReplyDelete"...then the only remaining mystery is why different observers' shrinking lightcones always point in the same direction."
My hunch is that by manipulating gravity, dark energy determines the direction and, to a lesser, the "speed" of light cones.
Light cones contain a pretty clear fossil record of electromagnetism, but a not so clear fossil record of the other forces in nature -- especially gravity. And the fossil record of dark matter (and especially dark energy) is nowhere to be seen in light cones.
Bee:” Similarly, had I told you I don't like getting up early, and clarified with early I mean before ten a.m., you could suggest I should understand early as being before six a.m. But I still wouldn't like getting up at nine.”
ReplyDeletePerhaps, you could suggest I should understand that as: I don’t like E.P.Wigner too.
If so, why?
Regards, Dany.
Hi Robert,
ReplyDeleteNo, sorry, we're headed North instead!
-B.
Bee, I absolutely love your blog. This is my first time posting, but I think I'll be around for a while.
ReplyDeleteAs to the question of "Now" being different than past or future, I think
I agree with you. But I feel I am missing something profound here (?)
In what sense would it be meaningful for "Now" to be any different than past or future? (other than the trivial sense of the observers experience).
To me the question seems as important as asking whether "Here" is a different "sort of space" than "There".
(And Here is Clearly the Only point in the universe. If you ever make it to Seattle I'll prove it.)
Best of luck with the job hunting.
-Jeremy
Hi Jeremy,
ReplyDeleteWell, the difference is that we know we can be in the same place at two different times.
Thanks for your kind wishes regarding my job search. I did find a new job, and am presently organizing my move.
Hope to see you around...
B.