Talk:Time in physics

Former comments
(William M. Connolley 22:01, 10 Jun 2005 (UTC)) This article is weird. Most of it is about the history of time in physics (which is how it started off) which is splendid stuff but really belongs in an article called... history of time in physics. Some of it (eg the lagrangian stuff) appears to be "some equations which have time in them" and I can't see the point. Charles, this is all your fault :-)

Perhaps it should be called "the history of time in physics", but then again the subject of what time has meant to physicists has changed over time. The reason for this is because just thinking about time one can come to so many conclusions. And the issue of the physics tied in with the philosophy of time has not even been suggested by the title. For anyone too impatient to wait for the cleanup I suggest reading "Time" by Craig Callendar. Dessydes 16:34, 19 May 2006 (UTC)

To the reader
Time is a fundamental subject in physics which has taken thousands of years to understand and master. In distinction to Space, which is obvious to our eyes, it took some technological developments to make the subject of Time easier, and we are not yet done with the subject.

If you do not understand part of the article, just let it pass; your mind will return to that which you did not understand, if you are still interested, and you have prepared yourself for the next encounter.

Time in computational physics
I left this section alone, during the rewrite. Does it make sense to delete it? It is covered in a previous sentence of the article: time is a parameter in physical models Ancheta Wis 10:25, 1 February 2007 (UTC)
 * Unless others object, I'm gonna delete it. This section contains unreferenced statements originating from an erroneous identification of the update step in an algorithm with time. The two are unrelated. JocK (talk) 14:00, 2 February 2008 (UTC)
 * Done. -- JocK (talk) 09:02, 10 February 2008 (UTC)

To the editors
I have retained the cleanup notice; it sits at the foot of the article. If the community deems it fit, we can then remove the notice, in time. Removed the tag as a bot got hold of it. --Ancheta Wis 18:36, 6 January 2007 (UTC)

The physics of a conversation
Since working on the cleanup, I realize that I have never seen research on the physics of a conversation. What I mean is that the world line of a system can be known, but what about two intercommunicating systems? Are world lines doomed never to interact, except thru dynamical influences? The closest thing to this I know about is A Mathematical Theory of Communication which embodies encoding and therefore protocol, but I would appreciate a citation for a basic, from the ground-up, analysis. --Ancheta Wis 14:40, 10 September 2006 (UTC)
 * See Rudolph Carnap (May 1957) Chapter G (sections 48-51: pages 197-212), "Axiom Systems of Physics", Introduction to Symbolic Logic and its Applications, a translation by William H. Meyer and John Wilkinson of Carnap's January 1954 Einführung in die symbolische Logik.
 * Carnap utilizes the concept of a signal line which finesses the need for contiguity of world lines, but which instead allows for a signal chain between world points.
 * Ancheta Wis 19:04, 25 December 2006 (UTC)

Why time causes paradoxes in physics
Math is a highly compressed language that seeks to symbolize experiences in a very precise way. In many calculations time is treated as an abstract term, just a number, and detatched from the experience that is beyond the symbol, namely a cycling countable event. because of this detatchment, silly notions like backwards in time and time travel can arise. It is not so easy to make time into a negative if you see it for what it is, namely some perceived stable event that one can use as a gauge for other less orderly events. Speed is Distance/time, but this gets all hairy in relativity where its not so nice and neat as the mass of the object and its speed begins to effect the time factor, which mathematically seems to go negative beyond light speed...but of course that is only because the numbers have lost their connection to the events they are symbolizing.Jiohdi 21:44, 5 February 2007 (UTC)

I will get more concrete and refer to John Cramer [http://seattlepi.com/local/292378_timeguy15.html is preparing an experiment] to determine whether quantum entanglement is also nonlocal in time as it is in space. This can also be stated as 'sending a signal back in time'. The experiment is still in preparation as of 10:57, 16 November 2006 (UTC).

Eckard Blumschein ,, claims that there is no signal back in time but perhaps just a mistake. E. Schroedinger wrote in 'Quantisierung als Eigenwertproblem', 4th Mitt. in Ann. Phys. (4)81, 109ff (1926), p. 112, 'one may consider, if nessessary, the real part of psi the real wave function". He omitted the aspect of required apparent symmetry. Only positive elapsed time can be measured. Our usual time scale is bound to an arbitrarily chosen event. It has been abstracted and extrapolated from elapsed time which is bound to a real object. This abstraction replaces one-sided integral relationships by differential equations. Pertaining time-symmetry requires exclusion of the unphysical advanced part of solution in order to obey causality: Future quantities cannot influence current processes being causally embedded into the integral effect of past influences. Invariance against shift and even reversal of time reversal is only possible at the level of abstracted usual time.

Since time and frequency are related to each other via complex Fourier transform, function of either time or frequency must exhibit Hermitean symmetry, i.e. positive as well as 'unphysical' negative arguments. Fictitious negative elapsed time is required as to encode merely positive frequency chosen by Schroedinger and also by Dirac. Weyl did not understand this in 1931. He wondered about PCT-symmetry.

One has to humbly accept that both imaginary and apparently negative quantities are the tribute one has to pay for abstraction into IR anstead IR+ and use of complex calculus. Apparent symmetries must be interpreted as unreal. They would disappear with correct inverse transform as do imaginary quantities, too. Blumschein 17:22, 5 March 2007 (UTC) Links corrected 3 February 2010 Blumschein (talk) 10:52, 3 February 2010 (UTC)


 * Your paper suggests an experiment based on Cramer. Cramer might try dumping energy into both future and past. Your paper suggests all the energy will wind up in either the past or the future, and not in both directions. But this would require careful accounting of the energy in each pulse which he is transmitting. --Ancheta Wis 19:17, 5 March 2007 (UTC)

Do not get me wrong. I just picked up Cramer's idea as an example of ignored essentials. Nobody can analyze future data. They simply do not yet exist. While past events are evident from left traces, future events are only predictions, no matter whether they will come true or not. Albert Einstein wrote: 'For us believing physicists, the division into past, present and future has merely the meaning of an albeit obstinate illusion.' I do not see any reason to share this belief with him, Newton, Minkowski, Hamel, Hilbert, Noether and many others. At least there is no doubt: While past is unchangeable, future is uncertain. All measurable reality exclusively belongs to the past. It makes a serious difference whether one deals with abstract time as did A. E. and John Cramer or with reality-bound elapsed time. I am pointing my finger squarely to most serious consequences of the neglect of this essential difference between abstract time in IR and concrete elapsed time in IR+. While obviously nobody can go back in elapsed time, mainstream physics and technology do not yet understand the implications for signal processing and quantum mechanics, including fourfold redundancy, non-causality, arbitrariness, and misinterpretation of apparent symmetry. Blumschein 07:07, 6 March 2007 (UTC)

Relativity
An interesting concept arises when relativity is analyzed. The fact that an object's speed and mass have an effect on time itself is a rather unique, interesting concept. Perhaps the best explanation for this, in my opinion, is that time is not a stable, concrete quantity. In other words, time can be thought of as simply a manifestation of matter and its properties. For instance, in a universe which has no beginning and no end, and in which all matter remains in a fixed, constant position and does not change in any way, time can be thought of as inexistent, since matter and the universe it inhabits doesn't exhibit any modification. Therefore, all observable changes in time can be thought of as simply changes in matter. When we consider time for an object sitting still, one might say that the object's time progresses even though the object exhibits no change. While this statement is valid, one could also say that this is simply because the surrounding matter (surrounding the observed object), and, consequently, the universe itself, is in continuous motion and constantly exhibits observable changes which influence the observed time for the observed object. In a universe in which all matter remains constant (and the universe itself did not, will not and does not exhibit any change whatsoever), time for any object can be considered as being inexistent. Nevertheless, time is significant and its presence is influential. The answer to the question "what is time?," however, is, I believe, more complex than a simple 'AM-PM' differentiation. —Preceding Signatures comment added by 24.219.29.168 (talk) 08:09, 18 January 2008 (UTC)
 * 24.219.29.168, I like your contribution, but it does not follow that time is dependent on matter. All that can be said with certainty is that parties within a common light-cone can signal with each other, if one were to accept general relativity. We currently do not even have a way to tell if an object is 'sitting still', because our ideas about that are formed by our relationship to the massive earth on which we sit, and that earth was formed during the long passage of time. If our own earth was the result of accretion of iron-based accreta from a past star, and if we are currently too far away from objects like black holes to suffer huge gravitational effects, then we do not yet know very much about the relationship of time to matter, for lack of observations. The new space-borne observatories are remediating this lack, and we await the science which will be published from this data. But new physics can arise from new philosophy as well, as Newton so stunningly showed, so your contribution just might be indicative the new approaches that we need. --Ancheta Wis (talk) 12:34, 18 January 2008 (UTC)
 * Note that the article shows the dependence of the passage of time on the strength of a gravitational field. But matter is subject to other fields than gravitation, as well. An accounting of the factors in the accuracy of a time standard includes other terms besides the effect of the gravitational field on the satellites of the global positioning system. The last I read, there are at least a dozen other terms in the error budget of such a system. --Ancheta Wis (talk) 12:47, 18 January 2008 (UTC)

Ancheta Wis, you have an interesting point. Perhaps time is as you describe it, however, I am still curious as to whether or not a 'timeless' universe can exist. Theoretically, however, I doubt that we could ever discover such a universe (at least, not through the use of wormholes, as their existence requires the presence of time, and, therefore, 'hopping' from our universe to a timeless universe would be impossible with wormholes). What I find interesting from your statement above is that we do not have a concrete way to determine whether or not an object is 'sitting still.' This does raise a few questions, since the concept of standing still is present throughout various physics topics. I agree with what you said about time and the gravitational field, however, I have yet to see how my previous statement can be considered a meaningful contribution. As far as I'm concerned, my, "philosophy" is, in the end, a compilation of unconfirmed facts, which, as you have stated, is incorrect anyway. 24.219.29.168 (talk) 09:17, 20 January 2008 (UTC)24.219.29.168

Accuracy of UTC timestamp
The section "The state of the art in timekeeping" contains the statement: ''The UTC timestamp in use worldwide is an atomic time standard. The accuracy of such a time standard is currently on the order of 10(-15) seconds.''. What accuracy is this? An absolute accuracy compared to what? I can hardly believe the statement to be correct. More likely the relative accuracy is of the order of 10(-15) (second per second). (This figure is typical for atomic clocks). JocK (talk) 14:16, 2 February 2008 (UTC)
 * My source was an NIST writeup. sigma of .5 * 10(-16) sec Yes, on the face of it, the accuracy is with respect to the system, because no absolute measurement exists, but measurements relative to the standards, i.e., to NIST-F1 will not vary by 1 second in 60 million years, which is 1 in $$1.89 *10^{15}seconds$$ --Ancheta Wis (talk) 20:57, 2 February 2008 (UTC)
 * Thanks, that's most useful. Have changed the text to reflect that this is a relative accuracy (measured in dimensionless units). JocK (talk) 07:11, 3 February 2008 (UTC)

Not canonical conjugate
This is certainly a difficult topic to write about and the article contains considerable confusion. For example, the statement "Energy and time are canonical conjugate variables of each other." is not true. I won't go into details as the matter is subtle but if this is disputed then provide a citation. Xxanthippe (talk) 09:15, 10 February 2008 (UTC).
 * I assume you are refering to the section on the Hamiltonian formulation of Newtonian mechanics? To me that seems a piece of text only complicating the issue. However, I can't find anywhere a remark like "Energy and time are canonical conjugate variables of each other." -- JocK (talk) 09:27, 10 February 2008 (UTC)
 * Ahh.. I see, you have already deleted the remark from the text. JocK (talk) 09:42, 10 February 2008 (UTC)

Modern perspective missing
The article lacks any discussion on the treatment (and emergence) of time in modern physics. No discussion on time in (loop) quantum gravity, no remarks on time emerging from spin networks, causal sets, no discussion on the twistor formulation of spacetime, etc. etc. As it is, the article should be entitled "The history of time in physics - from Galileo to early 20th century". I think the article needs a lot of work to become meaningful as a deepening into the physics not discussed in the general article Time. -- JocK (talk) 09:51, 10 February 2008 (UTC)
 * Be Bold with statements of additional content, backed up by citations with page numbers to the articles or books. If you were to get the ball rolling, I could help out. But the Penrose and Hawking equations are too hard for general consumption, so if you have an approach to make their exposition more accessible, how about giving it a go? --Ancheta Wis (talk) 10:42, 10 February 2008 (UTC)

More fuzzy headed fantasies
Forgive the use of the word fantasies. It may be strong but I feel it relevant. This is because I recently sat through a UK TV documentary on the subject of time where the question "What is time?" was asked repeatedly. The physicist asking the question then went off on several irrelevant tangents and frequently behaved as if he had answered the question. I was somewhat shocked at the standard of the presenters logical reasoning. Or lack thereof. The simple truth is time does not exist.

By "time" most people who should know better and would if they stopped and thought about it for 5 seconds think of time as a "dimension." There are of course 3 of those x y and z. All others alluded to are fantasy. String theory is so much overcooked spaghetti. The pasta burnt partly because of the requirement for 4 or more dimensions. 11 or more is just comic desperation. The fact that mathematics can be done is abstract irrelevance. If a notion sounds idiotic it probably is and it probably is because the proposer confused time with a "dimension."

What is actually meant by "time" is just a convenient shorthand for "sequence." Clocks measure nothing but sequence and simply indicate their power source is not totally defunct. They measure nothing - they merely indicate. The difference is important. They sequence with the sun, the moon their own mechanisms and so on. Similarly atomic clocks merely sequence decay in relation to the previous. If they relied on some mythical "fourth dimension" why would the concept of a "leap second" even exist?

There is no evidence of any "time" dimension. There is nothing capable of measuring time as a dimension. That is the simple truth. I would assert scientific truth, today.

If the concept of time is indeed of any importance then everyone at CERN needs to downtools and start looking for it because as yet (appart from abstract numbers on a page referencing mere sequence) there is not one single shred of evidence that something we call "TIME" exists.

But then we live in a world where politicians are requiring us to change light bulbs because someone somewhere thinks they (and other idiotic activities) can affect, "global warming" ... Perhaps we should stop putting flouride in the water and use lithium instead.

213.48.36.3 (talk) 16:01, 5 January 2009 (UTC)jw

PS Please don't annoy the next user of this IP address - This is a dialup connection and they won't know what you're talking about.
 * You are welcome to contribute to the article. I actually sympathize with your contribution on this page, but let's try to build up the encyclopedia, here. Please give citations for your assertions, and No Original Research. We live in a culture which espouses a causal universe and time, sequence, causation etc. have had a long history before us in this epoch. I admit that there are animals and cultures which would accept your thoughts without qualm, but have you also considered that plants follow a law of growth, which requires time? --Ancheta Wis (talk) 17:59, 5 January 2009 (UTC)

Rationale for the prerequisites infoboxes
When someone is reading a subject they have not studied, then even elementary terms can be roadblocks. These infoboxes serve to show where more information can be gained. If someone understands a subject, the infoboxes do no harm. If someone knows less than they think they need to know, the infoboxes serve to show the extent of what is to be known.

My teacher, Feynman noted that it takes 4 years of diligent study to understand physics, and then graduate school to contribute to physics. The encyclopedia serves others; what better way than to show them what is entailed in learning a subject.

--Ancheta Wis (talk) 15:30, 5 February 2009 (UTC)

oh, to watch my seedling grow!
i remember when i wrote "intellectual history of time" and it was decried as reading much like a college essay (and it did!). it was split and became this article, and oh what it is now! a detailed, thorough, and much more encyclopedic "high" importance article! gotta love wikipedia! kudos to everyone! Kevin Baastalk 21:36, 24 February 2010 (UTC)
 * Thank you from one of the elves. ;-) --Ancheta Wis (talk) 22:48, 26 February 2010 (UTC)

OR in lede
{or-section|date=July 2010|reason=}


 * Remove POV and WP:OR paragraph to talk page here. This is unencyclopedic, and reads like a commentary or magazine article. I placed it here because it is part of this discussion Steve Quinn (talk) 05:13, 3 August 2010 (UTC)


 * Time is a real phenomenon (according to most physicists and philosophers (cf. exceptions)) and it therefore has a basis in physics&mdash;ie. physical functions and physical laws. However its full workings remain mysterious and not all understood (likely holographic and logical in nature). Hence though time may be a key aspect within the study of physics and physical interactions, it is treated simply &mdash;as a measurable and transactional continuum that acts upon a physical object, generalized (cf. general relativity) to a single quantifiable dimension within the geometry of a physical space (cf. reference frame).

The assertion that time is real is either contentiously meaningless, or is POV opposing several scholarly authors. 2>What it "likely is" is completely unsubstantiated AND never discussed in the article - so it does not belong in the lede. 3> that it is an agent that "acts upon a physical object" is too speculative to not be at least attributed to some scholar, somewhere in the article. This appears to be nothing but POV original research --JimWae (talk) 19:37, 30 July 2010 (UTC)


 * Thank you for commenting. The word "real" links to reality. Could you please explain how these "several scholarly authors" claim that time is not "real" or else a part of "reality?" -Stevertigo (w | t | e) 22:10, 30 July 2010 (UTC)


 * I do not hold that time is not real, nor do I assert it is "real". See

Time. Einstein also made comments questioning the "reality" of time. It is not up to you or I to pronounce them wrong.--JimWae (talk) 00:07, 31 July 2010 (UTC)


 * You have not addressed my points--JimWae (talk) 00:10, 31 July 2010 (UTC)


 * You don't seem to have any points to make. The sophistic approaches in the section you point to are not convincing, and there is nothing wrong with asserting that time is "real" or a part of "reality." Lets put it this way: All things which exist are said to be "real," and all things which are "real" have physical basis. Physics, the science of physical things, treats time as a property of "reality" or nature. Hence "time" is known to scientists to have a physical basis, and thus we may regard it as "real."
 * I could argue the other way, attacking the sources which argue that time is "unreal" "surreal" or "non-real:" Their arguments, summarised from article section.:
 * Antiphon the Sophist: "Time is not a reality (hypostasis), but a concept (noêma) or a measure (metron)."
 * Parmenides: 'time, motion, and change were illusions,'
 * Zeno: Zeno's paradoxes
 * "Buddhist thought": Time as illusion is also a common theme in Buddhist thought,
 * "Some modern philosophers" - have carried on with this theme.
 * J. M. E. McTaggart: "argues that time is unreal (see also The flow of time).'
 * Julian Barbour: 'argue that quantum equations of the universe take their true form when expressed in the timeless configuration spacerealm containing every possible "Now" or momentary configuration of the universe, which he terms 'platonia'.'
 * Of course, I don't even need to find refutations for the above (""several [of Zeno's paradoxes] are essentially equivalent to one another; and most of them were regarded, even in ancient times, as very easy to refute"" article), as the whole section contains an enormous caveat:
 * "However, these arguments often center around what it means for something to be "real". Modern physicists generally consider time to be as "real" as space.."
 * So, again you appear to be simply (and unncessarily) argumentative. -Stevertigo (w | t | e) 01:26, 31 July 2010 (UTC)


 * It appears the lede is not in agreement with the rest of the article as Jim has stated earler. It is necessary to keep the POV out of the lead and remain neutral. I propose a lead that is supported by the references in the article. On another note, I am wondering if the current lede in the Time article would be useful here in some form or other? That is a very strong lede. Steve Quinn (talk) 05:05, 3 August 2010 (UTC)


 * Its "strong" only because its uselessly un-abstract. JimWae tagged my version here with exactly two flag comments:
 * cn - this sentence is presented as an argument, not a summation of sources.
 * cn - also:never discussed further down in article, violating WP:LEDE.
 * 1) The passage her is referring to is that 'time is a real phenomenon' and it "therefore has a basis in physics—ie. physical functions and physical laws." - This isn't controversial. This is only controversial to a subjectivist like Jim who introduces the material at Time as a counterargument to the notion (that time is "real" and not "unreal" or "surreal").
 * 2) The argument he's referring to was the simple parenthetical notation that time is "likely holographic and logical in nature." This introduces two essential concepts of modern physics, namely holographic principle and quantum logic. If its not mentioned in the body of the article then it needs to be. Its not a violation of LEDE at all to use a top-down approach to writing, and I think JimWae is more than misconstruing this policy.
 * -Stevertigo (w | t | e) 20:24, 3 August 2010 (UTC)

In this edit I have removed Stevertigo's unsourced original research, as far as I can see, not related to physics. I have taken the most important statement to the front and added what every physicist will agree what time is: it is what a clock reads. Let's keep in mind that this article is about time in physics. It is not about time in general, or in philosophy. I have also added a source for this. As it is now, we clearly "say what [it] actually is". DVdm (talk) 20:49, 3 August 2010 (UTC)


 * Saying that 'time is what the clock reads' is not only tautological, but its circular reasoning dependent entirely on the definition of a clock: 'a clock is what tells the time.' You can't introduce a concept - for example a car - and define the concept by saying something like 'cars can be measured from tip to stern.' 'A car is a vehicle with an engine or motor for locomotion.' We have to say what [it] actually is. Time is in fact a continuum allowing change to occur - an unknown set of physical functions that make physical objects transform. -Stevertigo (w | t | e) 21:00, 3 August 2010 (UTC)


 * It is most certainly not tautological, or circular. Whenever you can count something, you can call the result "time". That is the essence of the definition. Just look at the standard definition of the second. It is a pure count and there is nothing tautological, or circular about it. It is used all over the place in physics, technology and in the street. The counter is the clock, and what we read on it, is time. It's really very simple. Two observers can compare their times (between events) as read on identical clocks they cary with them. It is also how Galileo started doing physics: by counting the number of his heart beats to measure the "time" between two events. Remember, this is about time in physics - not in philosophy. DVdm (talk) 21:13, 3 August 2010 (UTC)


 * The formal definition of a second does not rests on the physical properties of caesium - its the formal measurement that rests upon the properties of caesium. A definition of time does not in fact rest upon any matter, even though its measurement may be correlated to the quantum properties of some element. You are confusing the mathematical/physical usage of "is defined as" with the actual concept of "definition" - ie. "the meaning of [a word]."
 * Relativity is of course relevant, but the concept of relativity does not actually change the (eigen-) definition of what time is, namely that it is that which provides all physical change itself. -Stevertigo (w | t | e) 21:26, 3 August 2010 (UTC)
 * It is not how Stevertigo characterizes it. It is simply either WP:OR or WP:RS and WP:VERIFY. Parsing statements and paragraphs is irrelevant. Either the material is based on reliable sources and is verifiable - or its moot. Wasting time discussing tautological and car engines is, well,  a waste of time.  The material DVdm edited into the article is Physics, and it is referenced. If the OR material returns to the top of this article it will be revereted. Steve Quinn (talk) 21:29, 3 August 2010 (UTC)

I don't see anything "resting" on anything, and I am not confusing anything. Someting can be unambigiously and straightforwardly counted by everyone and we call it "time". This is one of the most perfect definitions we can ever dream, and what is so important about it, is that it is an operational definition. Sure, of course philosophers don't like it, and yes, every philosopher has done his own original research, and no two of them agree, but -again- this is about time 'in physics. Perhaps you don't know, but specially in relativity, time is what each observer reads on his own clock. They all have their own time. Without this definition, relativity is moot. Just read any introduction to relativity. DVdm (talk) 21:44, 3 August 2010 (UTC)


 * (To SQ) What seems to be going on is that JimWae called for a RFC as a red herring to avoid losing the argument to me. That's the kind of person he is - fixated on argumentation and adversarial process. "Either the material is based on reliable sources and is verifiable - or its moot." - Almost 80 percent of what I wrote was supported by the source I gave. SQ claims "the material DVdm edited into the article is Physics, and it is referenced," which is bullshit. DVdm gave only one source and it is:
 * "Considine, Douglas M.; Considine, Glenn D. (1985). Process instruments and controls handbook (3 ed.). McGraw-Hill. p. 18-61. ISBN 0-070-12436-1."
 * Which is nothing more than a "best-selling guide [that] covers the design and operation of measurement and automatic control systems used in such industries as chemical, petroleum, petrochemical, food, pulp and paper, textile, water and wastes, metallurgical and product manufacturing." Nowhere in this guide does it talk about time itself in the general terms we require such that would support all of DVdm's writing.
 * (to DVdm) DVdm wrote: "I don't see anything "resting" on anything, and I am not confusing anything. Someting can be unambigiously and straightforwardly counted by everyone and we call it "time"." - But "time" is not "countability" in nature, or even "counting" in science. DVdm claims his definition ("time is what clocks say") is "one of the most perfect definitions we can ever dream" - Its simplistic. Is simplistic "perfect" for you? DVdm: "Sure, of course philosophers don't like it, and yes, every philosopher has done his own original research, and no two of them agree" - True, but what you fail to note is that I am taking a philosophers and physics approach, Jim is taking a Sophist philosophers approach, and you are taking what is only an engineers approach. DVdm: "They all have their own time. Without this definition, relativity is moot." - Good point. Your only good point.
 * -Stevertigo (w | t | e) 22:10, 3 August 2010 (UTC)
 * Suppose I were to write something that is almost identical over at the blackholes page: Blackholes are real phenomenon (according to most physicists and philosophers (cf. exceptions)) and therefore have a basis in physics—ie. physical functions and physical laws. However their full workings remain mysterious and not all understood (likely holographic and logical in nature). Hence though they may be a key aspect within the study of physics and physical interactions, they are treated simply —as measurable masses that act upon physical objects, generalized (cf. general relativity) to singularities within the geometry of a physical space (cf. reference frame). Although convoluted, the italicized part is more to the point, no pun intended, than any continuum/process/paradigm or whatever is said to be with respect to time, but from the first sentence on, my parody derivative work is mainly a load of non-differentiating rubbish for blackholes and so does not meet the criteria for wp:lede for a good opening first sentence and the paragraph is needlessly argumentative in tone and over-the-top stylistically, that says basically nothing about what blackholes really are until, of course, drum role please, the italicized conclusion. Whether or not what I wrote is original research (I could probably find various sources echoing any of one of these vague ideas) its simply not very good writing that should be reverted on sight with or without citations.  --Modocc (talk) 03:26, 4 August 2010 (UTC)


 * First of all the previous lede constructed by Stevertigo is essentially,overall, a philosophical statement. In other words it is not physics. Moreover, the attempt to provide sourcing is other Wikipedia articles, and these are not considered to be reliable sources, according to Wikipedia standards.


 * In the first line is the assertion that time is "a real phenomenon according to most physicists and philosophers". This does not work because there is nothing to back up "according to most physicists." I see that it is an attempt by the author of this statement to present this as not his own words. However, without a reliable source showing that this is according to most physisicst and philosophers then this single statement is pure WP:OR. At best it is personal opinion, and according to policy and guidelines the author's personal opinion is not acceptable material for a Wikipedia article.


 * The next sentence is unencyclopedic language: "However its full workings remain mysterious and not all understood" ... "full workings", "mysterious", "not at all understood" could be construed as WP:WEASEL weasel words, in that these are vague phrases. In addition, all three phrases read like opinion, or commentary. The next part of this statement is not understandable, or in other words, incomprehensible - "(likely holographic and logical in nature. In any case it obvious this whole second sentence, taken in part, or in whole is now in the realm of philosophy, and not the physical sciences or physics.


 * The third sentence almost fits with the sense of this article (imho): Hence though time may be a key aspect within the study of physics and physical interactions, it is treated simply as a measurable and transactional continuum that acts upon a physical object, generalized to a single quantifiable dimension within the geometry of a physical space.  Change to - Time is a key aspect within the study of physics (and physical interactions falls under physics). And I agree that time is treated as a measureable quantity,  as already stated in this discussion. And I agree that time is to be percieved as a continuum. Is it necessary to include "transactional continuum" -  instead of just continuum?.


 * Then this sentence falls short by stating time is a continuum "that acts upon a physical object." Time does not act on, interact with,  or  impact objects - hence this part is really not accurate,  and could not be supported by any reliable source. True,  in the other article Jack's introduction accurately states time is a single dimenision, which is also relevant to physcis. Finishing with "within the geometry of a physical space" sounds consistent with the science of physics to me......


 * Basically, overall, the first two sentences would probably have to be thrown out for the reasons stated above. The third sentence is confused, and melds accurate ideas with personal opinion, but may be salvagable and useful. (That's what it looks like). Furthermore, I reccomend not arguing for the first two sentences because it would detract from positive arguments and corrections that might be made for the third sentence. Also, I reccomend seeking out sources other than other Wikipedia articles for WP:RS   Steve Quinn (talk) 04:03, 4 August 2010 (UTC)


 * P.S. I will not be the one making positive arguments for the third sentence. I merely point out that it is possible to salvage this sentence (somehow).  Steve Quinn (talk) 04:21, 4 August 2010 (UTC)


 * I've read that relativistic spacetime and masses act on each other, so I think timelike curves can be said to act on objects. But I'm without a handy reliable source to further this cause. --Modocc (talk) 05:15, 4 August 2010 (UTC)


 * Modocc, I believe you are correct. I wasn't thinking about that when I wrote my above comments. I did think about it afterwards though :>). Steve Quinn (talk) 05:23, 4 August 2010 (UTC)

I'm just wondering what the physicists are going to say when they find out this article has been overrun by engineers. -Stevertigo (w | t | e) 01:14, 5 August 2010 (UTC)


 * LOL! Thanks for the laugh, Stevertigo (I really am chuckling about that comment). Also, I am glad you came back to read our responses on this talk page. Steve Quinn (talk) 01:27, 5 August 2010 (UTC)


 * - Modocc, I think it is interesting to note that you and I reached a very similar conclusion about the third sentence, at about the same time. But I guess I didn't have quite the same "special effects" (drumroll please!). I say this because when I first tried to post the above "critique" I had an edit conflict with you. I had scrutinized the lede in question because my curosity was piqued when I noticed that a certain percentage of Stevertigo's responses appeared to be down-to-earth physics, without any other dressing. It was then I decided to critique (or parse) the lede under discussion. Steve Quinn (talk) 01:53, 5 August 2010 (UTC)

Synthesis
For this section, these statements may require citations to references, or else it comes across as synthesis, and mostly vague. First, is the first appearance (see: heliacal rising) of Sirius to mark the flooding of the Nile each year somewhere in these three articles? Sorry, but I don't have the time at the moment to search through these articles to see if this is an accurate fact. If it is in these articles and it is sourced then it mght be OK. However, I reccomend some references with citations.

Second, the periodic succession of night and day, one after the other, in seemingly eternal succession does need to be cited with a source, and how does this relate to this aricle?

Third, the position on the horizon of the first appearance of the sun at dawn. Again, same as number 2, including how does this relate to this article? (vague)

Fourth, the position of the sun in the sky. This can be construed as common knowledge, however, when did the position of the sun in the sky have a relationship with telling time, or knowing increments of time? Again, same as number 2 and 3 (vague).

Five, the marking of the moment of noontime during the day is simply a vague statement. Again this does need to be cited with a source, and how does this relate to this aricle? And probably the statement with the gnomen needs to be cited and sourced.

In other words, all these need some sort of referencing to back up the claim - "Before there were clocks, time was measured by those physical processes which were understandable to each epoch of civilization". Specific epochs probably need to be related to by cited sources, otherwise I only have a vague notion that this sounds true, and might possibly true. Thanks for your time. Steve Quinn (talk) 06:37, 5 August 2010 (UTC)


 * Yes, I agree, this needs sourcing for the individual steps and for the conclusion. Otherwise it will die through wp:SYNTH . Won't be easy. On the other hand, I think this isn't relevant in this article to begin with, as it does not focus on physics. I propose we remove the section and simply rephrase (and cite) the first sentences of the intro-text part of source of the second. It briefly mentions the solar day in astronomy and its problems, and it can be properly sourced. In fact, if we put it in the following section, it is already sourced by itself. I.m.o. that should be sufficient in this article. DVdm (talk) 07:27, 5 August 2010 (UTC)


 * Friends of physics, It may help to read Otto Neugebauer's book. That's where I learned this. His examples may be difficult to follow unless you know some astronomy. But this is not OR because it's in astronomy books. --Ancheta Wis (talk) 09:37, 5 August 2010 (UTC)
 * If these examples seem obvious, yes, to me they are, but any careful listener in a beginning astronomy class could come up with them (except for the heliacal risings of Sopdet -- Sirius). And astronomy has everything to do with our conception of time. --Ancheta Wis (talk) 10:01, 5 August 2010 (UTC)
 * In case it is not obvious -- Physics, as the fundamental science, subsumes the first science, Astronomy. --Ancheta Wis (talk) 10:27, 5 August 2010 (UTC)
 * And to repeat the obvious, it takes a periodic phenomenon to define time, as does the current definition from BIPM. But everyone already knows this, no? --Ancheta Wis (talk) 10:35, 5 August 2010 (UTC)


 * Thanks for having provided the source and the notes. More sources to replace the notes are of course welcome. DVdm (talk) 12:59, 5 August 2010 (UTC)


 * Yes, thanks for providing references, I sincerely appreciate the time and work involved. Ummm... regarding reference number four. If I think a little bit about this reference, I catch its relevance to this section. However, this does not specifically describe an epoch in past civilizations, before clocks, when night and day was a measure of time, or a way to tell time. Also, I hate to state the obvious here, but this is a fictional work, and perhaps, by itself, is not a reliable source. Perhaps, another WP:RS could be added here which specifically describes night and day as a measure of time, before the invention of clocks, during a particlular time period in the history of civilization. Thanks for your time.


 * One other note: I have also been wondering if this section is relevant to the article. However, maybe this section is a way to further flesh out this topic :>). Steve Quinn (talk) 03:23, 6 August 2010 (UTC)


 * Another comment - User:Ancheta Wis has provided some quality references, definitely noteworthy. I haven't reviewed them all, but the first several references are very impressive. Thanks for the quality work, including reference number four! Steve Quinn (talk) 03:29, 6 August 2010 (UTC)

nonce tag
I have removed to tag, introduced by  after the lead was extensively discussed on the talk page (see above, all over the place), and a consensus (with only Stevertigo disagreeing) was reached. As it stands now, the concept is properly defined, with substance and clarity and with source. DVdm (talk) 07:45, 6 August 2010 (UTC)
 * I agree with the removal and the above statement.Steve Quinn (talk) 14:17, 6 August 2010 (UTC)


 * The template cites neither any policy nor specific guideline of wikipedia. Though the essay supporting refers to WP:LEAD, there is little attempt to tie it to any particular part of that guideline. The template and the essay are both entirely the work of a single editor. The template is not much more than "Steve thinks this lead doesn't meet his sometimes impossible standards, and reserves the right to insert his own insights as the true meaning of this concept". The title itself is unclear jargon. That editor's overeager tagging of articles with it is a sure way to get the template marked for deletion someday soon.--JimWae (talk) 15:02, 6 August 2010 (UTC)


 * I was not aware of this. So indeed, when this particular user inserts the tag into an article, it amounts to inserting a personal opinion about the article into the article itself instead of on the article's talk page. I have notified the user on his talk page. DVdm (talk) 16:13, 6 August 2010 (UTC)

Prerequisites
The list of "prerequistes" quite funny. Why is signal processing there? Why are any of them there? I think its more accurate to say that time is used to help understand these things (and really everything) but not that they are prerequistes to understand time. I'm going to remove it for this reason. — Preceding unsigned comment added by 2.123.253.142 (talk) 18:26, 29 January 2012 (UTC) Well to be very clear, I only removed the very first list, and kept the others. The first list was the list for the entire article and its not accurate to say that you need to know signal processing to understand the article. — Preceding unsigned comment added by 2.123.253.142 (talk) 18:31, 29 January 2012 (UTC)

Chinese writing is older than 3500 years
I must disagree that Chinese writing is younger than 3500 years ago. Joseph Needham writes of the origin of Oracle Bone divination which are right at 3500 years ago. According to Needham's description (Science and Civilisation in China volume 1), the ideograms formed by the oracle bones as they cracked in the fire were recognized as Chinese characters at that time (3500 ya). Therefore Chinese characters are older than 3500 years. 4000 years is another estimate which I have seen, which is consistent with Needham. --Ancheta Wis   (talk  &#124; contribs) 00:25, 25 June 2013 (UTC)

Time in physics
I deleted some items about when the sun comes up. That is about ancient time keeping, not time in physics. Overall going from that to relativity is a supermarket of ideas with little consistency. I think the whole section on Timekeeping should be deleted, it has nothing to do with this important topic in physics. I am not really dead (talk) 13:36, 21 February 2016 (UTC)
 * The concept is about regularities in nature, ranging from the first notice of a phenomenon, such as an astronomical event, and the correlation of those events with measureable phenomena. Think of how Galileo measured the period of the swinging lamp in the cathedral in Pisa: the measure that he used was his pulse. Measurement is, at its core, a comparison with a standard, as William Shockley has said. --Ancheta Wis   (talk  &#124; contribs) 14:20, 21 February 2016 (UTC)

Shockley? I am shocked, or shall I say schockleyed? But no, I see time measurement as a separate item from "time in physics" a very key part of modern physics. But maybe I am asking too much from this article. So let that junk be there, it does not bite. But the article is hopeless in that it is a supermarket of ideas with no relevance.

The way to fix it is this:


 * - Up to Newton, usual concepts.


 * - The thermodyn section here is totally confused. If you want to do asymmetry, read and understand Davies Physics of Time Asymmetry ISBN 0520032470. That would be a good start and will change things here. One item I am not sure about is that Davies may still think pre-acceleration, which is outdated now, but I do not have that book any more, so check on that if using it.


 * - Big issue was Einstein 1905, that is relevant here.


 * - QM is necessary and is poorly treated here.


 * - The section on cosmology is not just unsourced, but hodge-podge, and useless. Just delete it, and restart.

Whether seconds or half seconds are used to measure time, does not change the concepts in physics. Delete that.

But I have spent enough time on this. Moving on. But the article is hopeless. I am not really dead (talk) 14:53, 21 February 2016 (UTC)
 * The cosmology section has a narrative, beginning with GR (general relativity, 1915) I number the paragraphs below, which are summaries of the respective paragraphs of the section. --Ancheta Wis   (talk  &#124; contribs) 01:00, 23 February 2016 (UTC)
 * Lemaitre proposes GR equations imply a primordial explosion. Einstein disagrees but is silenced by Hubble's discovery of expanding universe.
 * Gamow deduces from this that the universe was hotter and denser in the past, which would mean there is a residual background temperature.
 * Penzias and Wilson detect Gamow's predicted background hiss.
 * Relationship between Now and the Planck epoch.
 * GR provides us with the potential for gravitational wave observations (LIGO) to cover the time between the Big Bang and the opaque universe (0 to 400,000 years) that we cannot see with optical telescopes. (Need to add this to the section)

Time (physics)
To be consistent with other articles related to pure sciences and to articles cascading from this one: Motion (physics), Position (vector), Point (geometry), Space (mathematics)..., I suggest to rename this article as Time (physics). X-ode (talk) 14:37, 27 October 2017 (UTC)

"Time" is used as a Distance
Also we should make clear that Distance equated to Light Years, is in Einstein's terms, as a viewer at either end of the measurement. So if we see at a "distance" of thousands of light years away, it is really a distance, being measured in real time, today, from either end, and a misuse of "units of distance measurement". Both from our Planet and from the distant object to our Planet. We are not looking through a "glass ball" or "glass eye piece" and doing "time travel", which is a science "no-no". Many thanks for modern "witch craft"! For further "inquest" into reality, look me up!(2001:569:7DC2:E100:C16:4759:BFB6:BE02 (talk) 01:57, 27 November 2019 (UTC))

Self promotion
I have reverted edits by user per obvious wp:COI and wp:UNDUE. User keeps reverting. Warned on user talk. Comments welcome. - DVdm (talk) 22:02, 3 November 2018 (UTC)

Main definition
"Time in physics is defined by its measurement: time is what a clock reads." Is this really the best we can do? Is it really the consensus view of physicists who are interested in time? This definition obviously leads to circularity; a clock is something that tells time. Isn't the cited reference coming from a specific sub-discipline (process instruments) which has an especially limited view of time? I am no physicist. I'm just sent here from a YouTube talk which ridiculed the Wikipedia definition of time - and rather reasonably, it seems to me (see https://www.youtube.com/watch?v=PdL8CudJTcs - 35 seconds in). Mrmedley (talk) 07:51, 14 May 2021 (UTC)
 * See operational definition --Ancheta Wis   (talk  &#124; contribs) 12:32, 3 June 2021 (UTC)
 * Thank you. This helps me see that the given definition does make sense - as an operational definition. But wouldn't a more ontological definition also be relevant, given that the subject of the article also includes things like physicists' conceptions of time? At least it seems the lead definition should be flagged as an operational definition, while mentioning that the article is also concerned with ontological conceptions. Mrmedley (talk) 00:41, 4 June 2021 (UTC)
 * Ontological definitions (and other musings) can be found in the article Time. As this article is specifically created for the physics-related aspect of time, we can only give an operational definition, and I don't think we need to emphasise that, as anything beyond operational would belong to philosophy and would be off-topic. DVdm (talk) 09:46, 4 June 2021 (UTC)