Talk:Gravitational time dilation

message: How is the 66.4 seconds calculated?
I got 66.9 seconds when I set r, the radial coordinate of the observer, to be ON the surface of the sun next to the proper time clock! 
But shouldn't the observer be very far away from the proper time clock? 2003:E5:1F0C:3685:D3C:A7B8:74AA:8477 (talk) 05:44, 4 July 2023 (UTC)
thread_title:  Time dilation at the surface of the sun

message: Fisrt line in the article:
"Gravitational time dilation is the effect of time passing at different rates in regions of different gravitational potential; the lower the gravitational potential (closer to the center of a massive object), the more slowly clocks run."
This does not tally with the fact there is no gravitational potential the centre of a massive object. There seems to be a confusion about whether time dilation is caused by gravity i.e. curvature in space-time, or dilation in space-time, which is highest at the centre of a massive object.  —Preceding unsigned comment added by 79.70.197.119 (talk) 07:47, 18 March 2010 (UTC)
replies: text: If you choose the centre of the gravitational object as your reference, then clocks simply run faster as you ascend, which is equivalent to the statement quoted from the article.   However, this choice of reference does not seem to me to be a great idea, as the references for different mass gravitational objects will be inconsistent.   A standard way this problem is addressed is to assign zero to a theoretical location that has the highest possible gravitational potential and treat all gravitatiol potentials as negative values relative to this.  This is the basis for the expression "gravitational well"PhysicistQuery (talk) PhysicistQuery (talk) 14:03, 14 December 2022 (UTC)
thread_title: gravitational potential

message: My own meager calculations led me to the conclusion that here on earth our gravitational time dilation is equal to 1.00000000009 days for every 1 day that passes to an observer outside the system.  These were based on what is thought to be the current size of the black hole (299,460,000 km in diameter) at the center of the milkyway and our 26,000 light year distance from the black hole. Feel free to check my math, it's probably a off since i used the windows calculator.  I felt obligated to put something here since no one else has yet.
(Note: unsigned commment  10:38, 6 December 2005 71.254.97.250.  In future, 71.254.97.250, please use ~~~~ to sign your posts--- it helps alot in keeping track of who said what in talk pages, which can sometimes become very long and complicated!  And of course this is even more helpful if you have a static IP address or register an account (possibly under a pseudonym), but that's up to you.)
: Interesting, but not possible to confirm. We can't yet observe from somewhere outside of our relative position in the Milky Way. Jeff Carr 11:52, 21 January 2006 (UTC)
thread_title: Magnitude of gravitational time dilation at the surface of the Earth

message: Increasing the intensity of a gravitational field in a region reduces the effective rate of timeflow in the region?  Not true.  This doesn't even make sense.  Time flows at the same rate everywhere, or in geometric terms, lapse of proper time corresponds to arc length along a timelike curve.
What the author should have said is that spacetime curvature can cause the divergence of null geodesics as they move outward from an isolated massive body.  That means that a distant observer monitoring time signals from an second and much closer observer who uses his rocket engine to hover over the massive body will find the recieved signals to run slow relative to his own clock.---CH 21:09, 10 December 2005 (UTC)
thread_title: Well, for starters, the very first sentence is wrong

message: These formula only apply to:
*Schwarzschild exterior, i.e. static and spherically symmetric vacuum, so don't apply to field outside a nonrotating disk, outside a rotating black hole, outside a charged nonrotating spherically symmetric black hole, etc.
*a pair of static observers, one at Schwarzschild radius r and the other "at spatial infinity", so don't apply as stated to say an Earth-orbiting satellite and someone standing on the surface of the Earth.
Suggest a careful and thorough rewrite.---CH 21:17, 10 December 2005 (UTC)
thread_title: Section ''The equation(s) for Gravitational Time Dilation'' is misleading

message: Oh boy, oh boy, I dunno how this article got in this state, but it needs a complete rewrite before it can be called a reasonable encyclopedia article.  See the todo list for hints.---CH 21:25, 10 December 2005 (UTC)
thread_title: Organization

message: Ooops, just noticed another serious mistatement: Note that in General Relativity, the circumference of an orbit is less than 2 \pi the radius due to a mathematical consequence of the spherical spacetime geometry surrounding gravitating bodies.  Of course, by definition, in any spherically symmetrical static spacetime, in the Schwarzschild coordinate chart, the radial coordinate accurately represents circumference and area of nested spheres (constant r).  However, differences in r value do not correspond to radial distance (along radial spacelike geodesics with constant t). ---CH 22:37, 10 December 2005 (UTC)
thread_title: Mischaracterization of meaning of the Schwarzschild radial coordinate

message: The current editor of this page seems to be confusing gravitational time dilation with geodesic deviation.  Gravitational time dilation can exist in the absense of a curved spacetime.  All that is needed is to be in an accelerated frame of reference, and it appears.  The source of the acceleration (such as the gravitational field of the Earth) is irrelevant.  Similarly, the Albert Einstein quote does not belong here, since this is effect is a consequence of SR instead of being a refutation of it.  (Of course, in the overall context of GR that quote does apply, but this article is not about GR itself.) --EMS | Talk 18:31, 11 December 2005 (UTC)
replies: text: See the equivalence principle.  An accelerating rocket ship in outer space will, for the people on the rocket ship, have a gravitational field.  That this gravitational field is generated by the mechanical acceration of the rocket ship instead of curved spacetime is irrelevant to its being a gravitational field.  Yes, this is a linear acceleration, but for the people on the rocket ship, gravitational time dilation is a reality all the same. --EMS | Talk 19:09, 11 December 2005 (UTC)
thread_title:  Changed intro 

message: The disputed material has been removed, so I'm taking down the dispute message.Kmarinas86 23:04, 25 December 2005 (UTC)
replies: text: I think that you are effectively "rearranging the chairs on the Titanic".  You are obtaining a better grasp of the material, and for that I applaud you.  None-the-less, this is still far from being a good article on the subject.  The big offense right now are the terms "fast-acting" and "slow-acting":  These are neologisms, and their use is prohibited by the no original research policy. Also, there is no need to use new terms when describing a well-known phenomenon.  I therefore strongly call on you to get rid of those terms.  (Besides, what is "fast" or "slow" is not the observers but rather the rate of proper time passage at their location.) --EMS | Talk 18:25, 26 December 2005 (UTC)
thread_title: From worse to good to better

message: Here are my complaints:
# Time dilation is the result of a gravitational field, not the presense of a massive object.  general relativity explains how massive objects generate gravitational fields, but that is not the only source of such fields.  In Einstein's definition, a gravitational fields exists in an accelerated box, and gravitational time dilation most certainly does also.  In addition, letting yourself spin like a top creates a world view with a gravitational field also, albeit one that is a function of your rate of spin.
# The Schwarzschild Solution is a good example of how gravitational time dilation is manifested, but it must be emphasized that this is for an idealized case (spherically symmetric non-rotating masses), and the equations for other cases (the accelerated box and the spinning observer) need to be dealt with also.
With my having gotten rid of a bunch of extraneous material, this article is now somewhat better than before.  However, it still has a ways to go, and I will see if I can work on it sometime soon. --EMS | Talk 19:19, 28 December 2005 (UTC)
thread_title:  New accuracy tag 

message: Is there a source for the airplane atomic clock experiement? I've heard this claim before but have never been able to find sources. How did they tell that the clocks had drifted and how much did they drift? This lack of information on this experiment has bugged me for years. I'm starting to think it's just urban legend. Especially now that I know how hard it is to measure small amounts of time drift between clocks, I wonder how it was that someone measured the drift. Jeff Carr 12:31, 21 January 2006 (UTC)
replies: text: Add also a request for a source that the GPS system uses this in it's calculation. I've also looked into that claim in the past and could never find verification. Jeff Carr 12:42, 21 January 2006 (UTC)
replies: text:  Further more, the white dwarf Sirius B and the Pound-Rebka experiment are both redshift experiments, not confirmation of time dilation. Jeff Carr 12:47, 21 January 2006 (UTC)
replies: text: The experiment was done. However it is only of historical interest, imho; far more stringent tests have been passed since then. The amount of science confirming both SR and GR is massive, seriously doubting it isn't scientifically useful (in MOST contexts it is safe to take it as 'true'). OTOH, it is very unlikely to be the last word on the structure of spacetime, either. Abitslow (talk) 19:43, 4 January 2015 (UTC)
thread_title:  Experimental verification ??? 

message: , aka the Jazztel triple play services anon from Spain, wrote "Gravitational in GR means Fictitious force. Gravitational time dilation can be manifested at any kind of accelerated reference frame, and by virtue of the equivalence principle, it will apeear also by the presence of large mass...".  The first sentence doesn't make much sense and is arguably seriously misleading; most would say that in gtr, gravitational effectes are identified with curvature effects in a Lorentzian spacetime.  I reverted the change, although I agree that this article could use much improvement. ---CH 23:24, 13 June 2006 (UTC)
thread_title: Edits by 87.217.89.114 

message: As a courtesy, I have removed the "expert" items from the todo list.
I am leaving WP and doubt anyone else will know how to implement the suggested improvements since this was mostly a note to myself.
Sadly, I am now abandoning this article to its fate.  I emphatically do not vouch for anything you might see in more recent versions.  Given past history, I have reason to believe that at least some future versions of this article are likely to contain slanted information, misinformation, or disinformation.  Beware also of external links to other websites, which may be cranky.
Good luck to all students in your search for information, regardless!---CH 00:19, 1 July 2006 (UTC)
replies: text: You're right, this is a pretty horrible article, fraught with bad wording and just plain old mistakes. It's lacking a lot. 93.172.41.139 (talk) 06:51, 16 May 2009 (UTC)
thread_title: Todo list

message: The last sentence of the following extract is in error:
If one is inside the sphere, the sphere can be split in two parts: a hollow sphere above and a solid sphere below. One is weightless anywhere in the interior of a uniform hollow sphere. With respect to one's gravitational potential, it is as if the hollow sphere is not there.
It is true that with respect to the gravitational field (the gradient of the potential), it is as if the hollow sphere is not there.  However, the potential inside the sphere is everywhere the same as that reached when moving inwards to the inner surface of the sphere.  This is a standard textbook result.
The following paragraph is also incorrect:
The implication is that the gravitational time dilation reaches its maximum at the surface of the non-rotating massive spherically-symmetric object, and that the gravitational time dilation reaches its minimum at the center of the sphere.
The gravitational time dilation actually continues increasing to a maximum at the center of the sphere, so this is misinformation.  I have seen a couple of cases in physics forums and newsgroups where people have been misled by this specific sentence in this article.  This section therefore needs rewriting to correct this error.
Jonathan A Scott (talk) 11:28, 20 February 2008 (UTC)
thread_title:  Error in section "Inside a non-rotating sphere" 

message: Why not just explain in that:
F1 = F2 = (M1 x M2)/r^2
F = MA^2
Td = Td/Square Root of v^2c^2
Response: Because your layperson, your average Wikipedia article reader will not understand them. They should be presented. But they need to be explained rather than just expecting the person to understand what each variable means.75.133.90.126 (talk) 19:32, 27 December 2012 (UTC)
thread_title:  Why not just present basic equations and their combination: 

message: Why isn't the "time dilation" in "Gravitational time dilation" capitalized in the title? 65.24.171.166 (talk) 21:47, 16 December 2008 (UTC)
thread_title:  Capitalization 

message: I just added reference sources including an online text (English translation) for the Einstein 1907 paper referred to in the lead paragraph.
Comments elsewhere on this talk page have shown the tensions that there can be in this subject-matter area over the addition of material that represents physical/mathematical mistakes, or original research, or possible fringe or crank theories.
I offer the following suggestion about possible improvements to the encyclopedic character of the article.
It seems to me that among the existing strengths of the article (whatever its discussed defects), is the part of the (curiously-named) definition section that mentions, and to some extent describes, how the equivalence principle can be applied to specific classes of case -- such as linear acceleration and the rotating disk, giving expressions associated with each.  It's a strength because it shows the interrelationships, and to some extent enables them to be followed up (which it would do better if there were also some inline references).
One of the arguable weaknesses, on the other hand, is that the description of the (Schwarzschild) case of the massive sphere gives no hint at all about the existence let alone the detail of a major peculiarity, the anisotropic character of the Schwarzschild coordinates.  While 'periti mathematici' may consider that this matter goes without saying, and/or can be found elsewhere (which seems so far hardly the case for WP), it's arguably the kind of point on which an encyclopedic text differs from a professional text, and it would be helpful not only to point it out but also to give alternative forms, in isotropic coordinates, which might better point out the way in which approximations have been derived and used.
One of the partial safeguards against mistakes, original research and crank theories would be the provision of plenty of inline references pointing to strongly reputable sources.  Again, 'periti mathematici' often write as if they are apt to think it's enough that the text should provide its own cogency. Maybe for some such reason, there's a general scarcity of references in WP mathematical articles to which experts have given their welcome attention.  But many encyclopedic readers can not judge that, and are much helped when they are able to see the provenance as well as the content.
With good wishes, Terry0051 (talk) 14:18, 13 August 2009 (UTC)
thread_title:  Citations, and encyclopedic character 

message: I am wondering, could the gravitational time dilation cause a redshift? Mevistoveles (talk) 19:37, 2 February 2010 (UTC)
replies: text: That's basically what gravitational redshift is (though I notice that article is tagged as needing expert attention so I don't know how helpful you'll find it). Also, article talk pages are designed for discussing improvements to their associated articles; if you have more questions about the subject matter you might want to try the science section of the reference desk. Olaf Davis (talk) 20:03, 2 February 2010 (UTC)
thread_title:  Redshift? 

message: Please, rectify these links. I am not an English speaker and can’t easily realize what effect this text is about. Incnis Mrsi (talk) 08:49, 28 February 2010 (UTC)
thread_title:  …[[dragster]] or [[space shuttle]] 

message: I look for objections about this piece of text persistently removed by  and once today – by . What is so wrong in it that you remove it compeletly? Also note that Pound-Rebka experiment is a redirect and incorrect typography. My change to direct link and correct typography was reverted three times by these users without explanations. Incnis Mrsi (talk) 15:53, 7 August 2010 (UTC)
replies: text: I simply reverted to the July 3rd version, before  started their edits. I thought this version was clearer than your version. However, I see that restoring the phrase "clocks run" may appear to give support to Jsolebello's nonsense, so I have now replaced it with "time passes". I have also restored your Pound–Rebka experiment correction. Gandalf61 (talk) 16:47, 7 August 2010 (UTC)
thread_title:  the lower the gravitational potential (closer to the center of a massive object), the less [[proper time]] will be elapsed there in the same temporal interval…  

message: Does anyone else think that the section headed Important things to stress is mostly either incomprehensible or nonsense ? Phrases such as "radiation and matter may be equally affected, since they are made of the same essence"; "as long as an observer is forced to observe only the photons which intercept the observing faculties" and "When the other, distant light intercepts the distant observer, it will come at c from the distant observer's perspective" make little or no sense to me. Gandalf61 (talk) 16:17, 13 January 2011 (UTC)
thread_title:  "Imporrtant things to stress" 

message: There is a big error in the start of the definition:
"Clocks which are far from massive bodies (or at higher gravitational potentials[dubious – discuss]) run faster, and clocks close to massive bodies (or at lower gravitational potentials[dubious – discuss]) run slower (slow is low)."
A clock which is farther from a massive body is at lower gravitational potential than a clock which is closer, not higher.
Considering the base relationship between distance from massive bodys and gravitational potential is wrong, I wonder how correct all the affirmations that involve distance from earth can be.
In the beginning of the article: "the lower the gravitational potential, the more slowly time passes;"
If this is correct, then the the definition must be wrong. If this is wrong, then the definition bust be right (despite the part about gravitation potential still being wrong).
Aristidesfl (talk) 08:32, 28 July 2011 (UTC)
replies: text: Hello, let me clarify. Here the Gravitational potential means the potential energy stored due to its vertical distance from the massive body. Remember the formula PE=mgh ? The same holds good here. By that we can say that if you are at mountain peak then you have greater Gravitational potential than you had when you were at the bottom of the mountain. So lower gravitational potential means nearer to massive body, higher gravitational potential means farther from massive body. About the time dilation, E=hf, f=1/T. As you are nearer to massive body the time runs slower and if you get away from it time runs faster. By this we can say that the above statement "the lower the gravitational potential, the more slowly time passes" is correct. Shriram (talk) 08:54, 28 July 2011 (UTC)

text: As Shriram says, the article is correct. To move an object away from a massive body such as a planet, you must do work on it, so you increase its gravitational potential energy (or, from an alternative point of view, you increase the potential energy stored in the gravitational field). Therefore the gravitational potential close to a massive body is lower than the gravitational potential further away. Think of it like stretching a spring - the potential energy of an unstretched spring is lower than that of a stretched spring. See gravitational potential for more details. Gandalf61 (talk) 08:57, 28 July 2011 (UTC)
replies: text: I understand both you explanations. Perhaps it is a matter of correctness of the terms behing used, which I believe are behing confused. Despite that, in the gravitational potential article, there are multiple evidences that indicate the farther away you are from a massive body the lower gravitational potential is. Maybe the most immediate evidence, is the table at the end with some examples: Gravitational potential#Numerical values. Aristidesfl (talk) 23:03, 28 July 2011 (UTC)
replies: text: Note that the sentence immediately above that table explains that the values shown in the table are absolute values of the gravitational potential. Gravitational potential is, by convention, negative everywhere (and notionally zero "at infinity"). So the actual values for gravitational potential with respect to the Earth are −60 MJ/kg at the Earth's surface, −57 MJ/kg at Low Earth Orbit etc. And −60 is indeed lower than −57. Where else, exactly, do you think the gravitational potential article supports your point of view ? Gandalf61 (talk) 10:05, 29 July 2011 (UTC)

text: Gandalf is correct. But Aristidesfl may have become confused because the absolute values do not have negative signs or may not have noticed the word absolute. So thought that they were positive. The first equation in the Gravitational potential#Mathematical form itself suggests negative sign. But they are absolute values so negative sign is not considered. Shriram (talk) 11:58, 29 July 2011 (UTC)
thread_title:  Gravitational Potencial vs Distance From Body 

message: The variable e in the first equation the one about the accelerated box is undefined. Definition please!75.133.90.126 (talk) 20:35, 28 December 2012 (UTC)
thread_title:  Why Isn't e defined? 

message: I think this is incorrect: "In an accelerated box, the equation with respect to an arbitrary base observer is T_d = e^{gh/c^2}"
There is a Rindler-horizon behind the accelerating obsever according to this article. If the locally felt acceleration is \alpha,
then the rinder horizont is at c^2/\alpha behind the observer. So the 1 + \alpha h / c^2 must be correct for linear acceleration. 
If you substitute -c^2/\alpha into h you get 0, as the time at the Rindler horizon stands still (like at the event horizon of a black hole).
This formula also justifies the paradoxical effects of Rindler coordinates. If an accelerating observer measures \alpha at bottom of a spaceship. The hyperbola
for the observer h higher corresponds to the acceleration \frac{c^2}{c^2/\alpha + h} which is a smaller acceleration. But as the observer accelerates
the plane of simultaneity rotates, so the two ends always connect two points on the hyperbolas where the slopes of the two hyperbolas is the same, so the local speed is always
the same along the object and the acceleration of the body remains uniform.
Now this is where the gravitational time dilation kicks in. The rate of the two accelerations is exactly 1 + \alpha h / c^2. 
Although the acceleration is uniform, observer h higher will indeed measure smaller acceleration because his clock is faster.
So to sum up I would edit that formula. 
I would also split the article into two parts. One that discusses the accelerating bodies (in flat spacetime) and the another one that discusses the effects of spacetime curvature.
Calmarius (talk) 15:10, 21 June 2013 (UTC)
replies: text: I agree with your criticism. One should specify how exactly the “box” accelerates, and, most importantly, is the space-time flat or curved. For Rindler observers, in the flat space-time, there would be no exponent, because magnitude of the acceleration depends inverse-proportionally on the  coordinate, and after integration we’ll obtain exponent of a logarithm, i.e. a proportional dependence of proper time on . Constant dependence of  on what they call  (≈ Rindler’s ) is impossible in a flat space-time, and is not a natural condition in a curved space-time. You may wreck the rogue exponent, but I think it would be better to replace it with exponent of the anti-derivative (integral) of the dependence of  on . Incnis Mrsi (talk) 16:38, 21 June 2013 (UTC)
replies: text:  Apparently older citations for the exponential equation exist from Weinberg and maybe Schwarzschild;  but one place where it was derived can be found on the talk page for the wikipedia article Gravitational Red Shift, under the heading Is Something Amiss? Samdhatte (talk) 06:21, 10 February 2015 (UTC)
thread_title:  Where does {{math|''e''<sup>''gh''/''c''<sup>2</sup></sup>}} comes from? 

message: I questioned the statement made concerning time dilation in a merry-go-round. There you always stay at the same level in the gravitational well. It should be a quite straight-forward and simple experiment to perform. All you need is an atomic clock and a playground close to the university. My question is: has such an experiment ever been done, and if so, did it support such a statement? Has anyone, ever, placed an atomic clock in a merry-go-round and observed time dilation? If no such experiment has ever been successfully done, then I do not think that the claim that time dilation exists in a merry-go-round can be totally unquestionable. The reptile brain of wikipedia however immediately removed my 'reference needed'. Why not instead provide a reference to an experiment made, or a 'but this has not been proved experimentally yet' statement? And, of course, if I happened to insult someone's profound religious beliefs, then please accept my apologies. Hilmer B (talk) 20:35, 8 February 2014 (UTC)
replies: text: The gravitational time dilation is a phenomenon. General Relativity with its equivalence principle is a physical theory. The theory reduces several phenomena to certain basic explanation (I mean non-inertial frames) – a good theory, but centripetal forces are certainly not gravitational forces. The example with Rindler’s acceleration can be considered: it is simple. The example with Ehrenfest’s disc is, mathematically, not so simple. I do not see any reason why should we dedicate sizeable fragments of this article to rotation-specific examples. I shall sleep now and can’t participate in the ongoing edit war with .  can you cope with it? Incnis Mrsi (talk) 21:57, 8 February 2014 (UTC)
replies: text: I agree that some articles have been written by authors that were maybe a bit too eager to cover it all and a bit more. Maybe that's the spirit of wikipedia. It will take time to get everything right, to which end we must all contribute, even if it's only a simple spelling error. So, I'm patient Hilmer B (talk) 11:12, 9 February 2014 (UTC)

text: I would get some form of consensus before removing the material in question from this article. The very fact that the effect of time dilation in physical systems such as in an accelerated (gravitational) reference frame is indistinguishable from that in rotating coordinates (such as a merry-go-round, or rotating disc) makes the discussion relevant to this article. Coldcreation (talk) 18:49, 9 February 2014 (UTC)
replies: text:  Furthermore, the quote above (with merry-go-rounds etc) is not mine. I merely reverted an edit that had removed the phrase. Coldcreation (talk) 18:56, 9 February 2014 (UTC)

text:  Certainly our discussion is relevant to the article. The question is whether the Ehrenfest’s disc, with its specific formulae for velocity and acceleration, is relevant to the article. Johan Prins quotes Einstein and considers the example himself, but I do not see where it is stated two things are the same. And what do Groen & Naess say? Incnis Mrsi (talk) 19:09, 9 February 2014 (UTC)

text: RoTFL. A person who can’t correctly count how many times certain Incnis_Mrsi edited the article in 2014 also removed certain Hilmer_B’s maintenance template because… okay, what namely merits a discussion in the article? Could you, Coldcreation, explain why my edition is minusminusungood? Which undisputedly relevant material did I remove? Incnis Mrsi (talk) 21:08, 9 February 2014 (UTC)
thread_title: Concerning Merry-go-rounds

message: In the second paragraph, the sentence "The effects detected in such experiments are extremely small, with differences being measured in nanoseconds." is meaningless. It tells us nothing.
The effect of time dilation is a systematic error in frequency as seen by a non-local observer. It is not a fixed offset between the two clocks, but an error that diverges over time, therefore the frequency error between two clocks is a unitless ratio. Let's say an error of 1ns accumulates every 1000s, then the error is 1ns/1000s = 1e-12 or 1 part per trillion.
I don't have at hand a realistic figure for observed time dilation, but it is obvious that "nanoseconds" is dimensionally invalid for measurements of the effect.
118.93.217.77 (talk) 13:23, 29 May 2014 (UTC)
thread_title:  With differences being measured in nanoseconds? 

message: This article is rubbish !!
Apart from all the problems outlined below, the 4th paragraph of the opening "Definition" says:
g(h)=c^2/(H+h) with constant H.
...without ever saying what "H" is !!
Useless !  
— Preceding unsigned comment added by 80.189.31.110 (talk) 18:18, 3 October 2014 (UTC)
replies: text: I agree that that section is horrible. Not only is H left undefined, but g' is not defined nor mentioned in the text at all yet is used in the equation as the critical parameter.Abitslow (talk) 16:55, 9 January 2015 (UTC)

text: More than six years later, I agree also, which is why I looked at the talk pages.   In addition, H is not a constantPhysicistQuery (talk) 14:15, 14 December 2022 (UTC)
thread_title:  Rubbish 

message: The lede isn't very good. The difficulty in explaining what is meant by time dilation is poorly addressed. I would bet that most people reading the lede would conclude that the effect is ONLY on clocks. Its pretty simple: to an observer who is in a lesser gravitational field, the time observed to pass in a higher field is less. This means that clocks tick slower on the surface of the Earth than they would in outer space, but it also means that everything is 'slower': breathing, chemical reactions, atomic motion, everything. To an observer in the high gravitational field, seconds tick by one-by-one, s/he ages one second every second that passes, remembers one day, for every day that passes. Only when s/he compares events with someone in a (very) different field will differences be noted. In Special Relativity, velocity imparts time dilation but it is symmetrical: observer A sees observer B's clock ticking 'slower' and at the same time observer B sees A's clock ticking slower. This means they will NOT agree which is "really" running slower and which faster. In General Relativity gravity (acceleration) breaks the symmetry: the more gravity (acceleration) an observer experiences the slower the passage of time.  If A is on Earth, and B in outer space or on Mars, then both A and B will see B's clock running faster than A's clock. They will agree that A's clock is slower than B's. The lede attempts to AVOID the use of proper time (which is probably good to start) but replacing the concept of the actual time someone is subject to with his/her clock time is confusing, imho.
Here is my suggestion for the first two sentences:
1. Change "Gravitational time dilation is a form of time dilation, an actual difference of elapsed time between two events as measured by observers situated at varying distances from a gravitating mass." to "Gravitational time dilation is a form of time dilation, a comparative difference of the passage of time as measured by observers under different gravitatational acceleration. (For instance, compared at different heights from the surface of the Earth; or on the surface of Earth compared to on the surface of Mars.  In any of these locations, an observer there will measure time passing normally, it is only upon comparison to observers under different gravity will differences be noted."
2. Change "The stronger the gravitational potential (the closer the clock is to the source of gravitation), the slower time passes." to "The stronger the gravitational potential, the slower time is seen by an 'outside observer' to pass there." note that it isn't just about distance from the mass, it is also the size of the mass. (distance, density and mass; actually).Abitslow (talk) 20:43, 4 January 2015 (UTC)
thread_title:  Clocks - a side-issue 

message: The diagram shows two vertical lines; one representing the surface of the Earth and one labled "Shuttle Orbits" (which at this scale are essentially a single line). I wasn't able to quickly find the range and average of the 130+ Shuttle orbits, but the International Space Station, a common co-orbiting object, orbits at 380 km. On my monitor, the distance between 0 and 10,000 km is 44.4 mm. The lines are less than 0.5 mm apart (essentially, on top of each other) yet the distance between 6380 km and 6760 km would be about 2 mm. In other words, the two lines should be separated, slightly. I understand that shuttle orbits vary, but for illustrative purposes the way they are depicted is, imho, wrong/misleading. Oh, the 44.4 mm was on the diagram's 'home' page (expanded), but the image as depicted in this article has the same problem: the lines should be separated, slightly.Abitslow (talk) 17:17, 9 January 2015 (UTC)
thread_title:  Problem with the diagram in Experimental Confirmation section 

message: Gravity is reciprocal to the squareroot of the distance. The gravitation on Earth compared to the gravitation 20200 km above the earth is about 17 times larger. So the difference of the gravitational component from earth the hight of a GPS satelite is reduced by a factor of 17. Any further reduction is small compared to this reduction. The effect of grafitational time dilation is far greater from the earth to the a GPS satellite than it is from a GPS satellite to the infinity and beyond.
So the greater distances do not demonstrate a greater effect, the effect of greater distances is little compared to the effect from earth to a GPS satellite.
Therefore my opinion is that reducing the above line to
Demonstrating greater effects would require a larger gravitational source. 
Crazy Software Productions (talk) 12:05, 8 April 2016 (UTC)
thread_title:  Demonstrating greater effects would require greater distances from the Earth and/or a larger gravitational source. 

message: In the second paragraph it states "Relative to the earth's age in billion of years, the earth's core is effectively 2.5 years younger than the surface [2] leading to a paradox of alignment with the celestial sphere due to the rotation of the earth."  What exactly is the paradox? Is it the Ehrenfest paradox or something else?  I'm not disputing the statement it's just I don't understand? Can anyone clarify?  Thanks  — Preceding unsigned comment added by 207.34.27.84 (talk) 06:12, 2 December 2016 (UTC)
thread_title:  Paradox of alignment 

message: I know this effect is widely known as "gravitational time dilation" and defined as observers experiencing slower time the greater the gravitational field they're exposed to. Now, my issue is, is this really tied to gravity at all? If you are on a spaceship that's subject to constant acceleration, someone on said ship's nose would experience slower time than someone at said ship's tail. Therefore, time dilation is introduced by acceleration itself, and not gravitation (which is one of many ways to induce acceleration), and I'd say the rule is that you experience slower time the further ahead you are in the direction of the acceleration. The definition based on the gravitational field's intensity is just a coincidence due to the fact that gravitational fields increase in intensity as you get further ahead in the direction of acceleration. Am I missing something? --uKER (talk) 04:59, 15 August 2017 (UTC)
replies: text: There are several problems with the way you deal with the subject. First of all, gravitational time dilation is proportional to the gravitational potential, not field, so that the clocks in the center of a star would do slower, than the same clock faraway, although neither experience noticeable acceleration relative to each other or the star. In general it is a slippery slope to try to pinpoint "who is exactly responsible" for a given phenomenon in general, but gravitation time dilation refers specifically to discrepancy to time pace for still clocks near a still gravitating body caused by the spacetime curvature, which in this particular case is present due to the body's gravity. So it is reasonable to call this gravity as a source, even if it works through general means of skewing the metric. L3erdnik (talk) 18:31, 16 August 2017 (UTC)
replies: text:  Just to avoid confusion, gravitational time dilation is not always defined by potential. For example, in the Friedman-Robertson-Walker metric, distant galaxies are said to have time dilation with respect to us, as evidenced by their redshift. But the redshift is due to the increasing scale factor a(t), which involves no potential. Of course, you specified "still", or static configurations, in which case what you said is qualitatively correct. But rigorously, time dilation is defined by the metric, and not by the potential, which is different. (Many metrics do contain terms proportional to potential of course.) 70.57.229.251 (talk) 20:07, 26 June 2018 (UTC)
replies: text: Sure, the proper time is affected by the whole range of possible peculiarities of the metric. However, particular model cases (that focus on a certain aspect in order to understand the majority of situations in terms of few simple model contribution) are pretty specific. Velocity time dilation focuses purely on the relative motion, Doppler effect focuses on how the change in distance affects the perceived time dilation purely by means of the signal having to travel, say, longer and longer distance (as an example being a part of the cosmological redshift, which you seem to talk about), and the gravitational time dilation focuses on the way a body affects the time flow purely by means of its gravity, while not trying to encompass all kinds of possible scenarios within GRT. L3erdnik (talk) 01:26, 27 June 2018 (UTC)
thread_title:  Is it gravitational at all? 

message: Hi [Coldcreation], do you have a specific reason for reverting my edit over at Gravitational time dilation ?  The r in question does refer to the 'slow-ticking' observer, and if you're someone who just wants to do a quick calculation, that section is clarified by making it explicit (it's explicit in all other occurence of 'observer' in the section). [The diff page is here.] Ketarax (talk) 16:48, 15 February 2020 (UTC)
replies: text: There is no such thing as a "slow-ticking observer". What was your former Username here at Wikipedia? Coldcreation (talk) 18:17, 15 February 2020 (UTC)
replies: text:  There's a "slow-ticking observer" in the clarification for t0 in that same section.  There's a "fast-ticking observer" spelled out for tf.  This "fast-ticking observer" is at r=inf.  The r we're dealing with is for the "slow-ticking observer", ie. the one within the gravitational field; also, this r cannot < rs. If you want to talk about rigorous presentation of general relativity, fine, but given the purpose and present state of that page, my clarification is not making it any worse. I want you to explain to me why in your opinion it would be wrong to call the observer within the strong gravitational field "slow-ticking" in this case. Ketarax (talk) 09:38, 16 February 2020 (UTC)

text:  I have never had any other accounts here at Wikipedia.  I've only made a handful of minor edits (like the present one).  I started my userpage yesterday, because I wanted to make it absolutely sure you can contact me; figured out right after that it was not needed.  If you would, I'd like to also hear what about my transactions has you feeling I'm playing some username-games? Ketarax (talk) 09:20, 16 February 2020 (UTC)
replies: text: There is no such thing as a "fast-ticking observer". More rigorous would be to write 'an observer whose clock is measured to run faster' and visa versa, instead of a "slow-ticking observer". Clocks tick, observers measure differences in time, or the relative speed at which observed clocks tick. Coldcreation (talk) 13:48, 16 February 2020 (UTC)
replies: text: So, you are actually against the language used in the whole section. Why you didn't edit the other slow/fast-references, I don't know, but I can do that. The point I'm trying to get through here is that as it stands, the section is ambiguous about the parameter r, and that this ambiguity can be resolved by explicitly stating whose distance it refers to.  I don't care if the end result speaks of slow/fast or Observer 1 and Observer 2, but this third "anonymous" observer that we currently have confuses the layman.  It might not confuse the expert -- but even an expert might overlook the ambiguity [when pasting wikipedia in their book].  Please don't kickban (or w/e) me as a returning vandal if and when I edit it again.  I'm only interested in concise dissemination of the scientific topics I'm involved with. Ketarax (talk) 14:44, 16 February 2020 (UTC)

text:  My proposed version is up now.Ketarax (talk) 15:35, 16 February 2020 (UTC)
replies: text:  Looks good. No need to use "fast-ticking" or "slow-ticking". I made a little tweak, removing the event names. - DVdm (talk) 16:06, 16 February 2020 (UTC)
thread_title:  Question about a revert