Talk:Time dilation/Archive 5

message: At a quick glance, there are no inline sources. Otherwise, it looks pretty good. Hurricanehink (talk) 04:25, 17 December 2006 (UTC)
thread_title: Failed GA

message: I think some formulas in this article does not convey any understanding of time dilation or anything else. I propose to change "'Time dilation at constant acceleration section"' into:
:In Special Relativity, time dilation is most simply described in circumstances where relative velocity is unchanging. Nevertheless, the Lorentz equations allow one to calculate proper time and movement in space for any other cases.
:The next simple case is movement with constant proper acceleration. Example of such motion is the movement of charge in constant uniform electric field.
:Let t \; be the time in an inertial frame subsequently called the rest frame.
:Let x \; be a spatial coordinate, and let the direction of the constant acceleration as well as the object's velocity (relative to the rest frame) be parallel to the x-axis. Then the equations can be written in form
::\frac{d^{2}x}{d \tau^{2}} = g\frac{dt}{d \tau} \;
::\frac{d^{2}t}{d \tau^{2}} = \frac{g}{c^{2}}\frac{dx}{d \tau} \;
:where 
::g \; is the proper acceleration,
:: \tau \; is the proper time, hence
::\left( c\frac{dt}{d \tau}\right) ^{2}-\left( \frac{dx}{d \tau}\right) ^{2}=c^{2} \;
:Assume the object's coordinates at proper time \tau = 0 \; are x = 0,t = 0 \; and the velocity is v = 0 \;, then the solution of these equations is
::x \ \ = \frac{c^{2}}{g} \left( \cosh \tfrac{g \tau}{c} - 1 \right) \;
::t \ \ \; = \frac{c}{g} \sinh \tfrac{g \tau}{c} \;
:: \frac{dx}{d \tau} = c \sinh \tfrac{g \tau}{c} \;
::\frac{dt}{d \tau} = \cosh \tfrac{g \tau}{c} \;
:Velocity 
::\frac{dx}{dt} = \frac{dx}{d \tau}/\frac{dt}{d \tau} = c \tanh \tfrac{g \tau}{c} \;
:For the trajectory we have the following result
::\left( x + \frac{c^{2}}{g}\right) ^{2}-c^{2}t^{2} = \frac{c^{4}}{g^{2}} \;
--TxAlien 05:59, 19 December 2006 (UTC)
thread_title:  Unreadable formulas 

message: It would seem that the  edit by 24.149.190.76 has made the introduction nonsensical, but maybe it has some value. I'm not knowledgeable on the subject to evaluate it, but if it does have any value, it certainly doesn't follow the WP:LEAD guideline. I've reverted to this intro. CameronHarris 14:22, 4 March 2007 (UTC)
thread_title:  Nonsensical introduction? 

message: The sun's curvature of space-time is greater than the Earth's thus allowing a greater time dilation effect on the sun. When we say that the sun will die out in 6 billions of years, upon which time reference frame do we base our calculus on? Do we take the time dilation effect in consideration?
Applying the logic of time dilation, it is wrong said that the sun will become a white dwarf in 6G years since our time here on Earth flows more quickly that the time around the sun (and much quicker than inside the sun's core)
On the sun's surface, the gravitational acceleration is of 27.9g rather than of 1g on the Earth's surface. Such a difference surely must have an impact on how time flows on the sun.
If indeed the sun will last for another 6GY according to our time reference frame, it means that the sun is indeed close to its death but thanks to time-dilation created by its own curvature of space-time, the sun's remaining lifetime is "expanded" up to 6GY.
Here's a shortest explanation:
According to OUR time reference frame: The sun is close to its death but thanks to time dilation, is death is in 6GY for us.
According to the SUN'S time reference frame: The sun has another 6GY of "solar years" meaning that on Earth, thanks to time-dilation, the sun is veeeeeeeeery far from its death.
W.D. Vargen 05:33, 24 March 2007 (UTC)
replies: text: The effect amounts to two parts in a million at the surface of the Sun. --EMS | Talk 22:20, 24 March 2007 (UTC)
thread_title:  Time dilation and the sun 

message: The alleged effect follows exclusively from theory and the mathematical consequences of the theory. The fact that certain effects predicated by the theory are observed, if they are accurately observed, does not rule out alternate explanations, and certainly does not create a one to one relationship between the theory and reality. Those with the strongest conviction that time dilation is an actual phenomena should check their own premises. To quote:
“ As for "proving" gravitation: You don't do it mathmatically [sic] to begin with. Instead it is the observation that matters. A combination of math and observation comes in when one seeks to verify that a given theory of gravitation is correct. In fact, this also brings up to your last question, since any explanation of gravitation is just a model and not the reality. Even if a given theory is exactly right, there is no way from first principles to prove that gravitation must exist and have exactly certain properties. Given that, any theory of gravitation must be just a theory due to its carrying with itself its own postulates. --EMS | Talk 20:12, 7 February 2007 (UTC “
EMS would be wise to adhere to the excellent standards he illustrates for others, rather than naively wandering away from science and into mysticism in order to preserve a cherished belief. 
It is well known that if you synchronize two highly accurate pendulum clocks, one on the highest mountain, and one in the lowest valley, one will run slower than the other … this is a fact. Does this mean that time runs slower at one place than the other? Or to carry it further, let the mountain clock be moved into Earth orbit, will it confirm that time is stopped or runs at an erratic and unpredictable rate in space? Must time do what clocks do? Reductio ad absurdum. 
Spin and elucidate your theories as you will. There is no need or justification for advancing them to the level of ‘FACT’. DasV 16:08, 20 April 2007 (UTC)
replies: text: This talk page is for discussing the article. It is not for discussing your misconceptions and frustrations. DVdm 19:15, 1 May 2007 (UTC)
thread_title:  Time dilation cannot be said to be a 'fact' or ‘real’. 

message: "Indeed, a constant 1 g acceleration would permit humans to circumnavigate the known universe (with a radius of some 13.7 billion light years) in one human lifetime."
Whoa whoa whoa, hold up! If we assume that a human lives to be 100 years old, wouldn't that mean that the maximum distance a human could travel in his lifetime would be less than 100 light years? I mean, a light year is how far light travels in one year, correct? And nothing can travel faster than light, correct? So how is it possible that by traveling at a speed that is close, but not quite the speed, of light, you could travel 13.7 BILLION light years in less than 13.7 billion years?
Am I overlooking something very obvious or am I the only one who sees this?
: Yes, you overlooked Length contraction. See if you can figure it out.
: DVdm 22:23, 2 May 2007 (UTC)
replies: text: If my understanding of time dilation is correct, the idea is as follows. If a person travels at the speed of light to reach a place 100 light years away, it will take him 100 years to reach there from our, the stationary viewer's, perspective. But for him, it will feel like he reached there in only a matter of minutes, and thus will have only aged a matter of minutes. However once the ship stops and he gets out, and checks the local time, he will realize that 100 years has indeed passed. 64.236.245.243 16:18, 8 June 2007 (UTC)
replies: text: No, you can find the answer in the article. Please note that this place is for discussing the article's content and format. Places like sci.physics.relativity might be better suited to help you increase you understanding of this. DVdm 16:26, 8 June 2007 (UTC)
replies: text: No? No what? What are you saying no to? Copy and pasting the same response for different points makes you sound incoherant. 64.236.245.243 17:41, 8 June 2007 (UTC)
replies: text:  As I already hinted, this is not the place to help you find a way out of your confusion. DVdm 18:25, 8 June 2007 (UTC)
replies: text:  This is a logical fallacy because I'm answering a question in this particular discussion, not asking one. *pats your head* You are confused. 64.236.245.243 18:36, 8 June 2007 (UTC)
thread_title:  No way this is possible?! Am I wrong? 

message: Ok I'm in a spaceship moving close to the speed of light. I am somehow able to look at a stationary clock outside the ship. That clock should appear (to me) to be ticking faster right? 64.236.245.243 16:13, 8 June 2007 (UTC)
replies: text: No, you can find the answer in the article. Please note that this place is for discussing the article's content and format. Places like sci.physics.relativity might be better suited to help you increase you understanding of this. DVdm 16:26, 8 June 2007 (UTC)
replies: text: This is comming from the guy who mentioned length contraction in the previous Time Dilation question lol. Don't be a hypocrite. 64.236.245.243 17:39, 8 June 2007 (UTC)
thread_title:  Just trying to understand Time Dilation... 

message: Time dilation plays an integral part of the story in the short anime film Voices of a Distant Star. Young lovers are separated when one decides to enlist in a six month tour of the galaxy and the other ages many years.
That wasn't time dilation.  The girl traveled by way of a wormhole to a distant location, many light-years away.  There was no time-dilation, it's just that it took many years for her messages to reach him back on Earth.  I removed it. Nik42 06:54, 8 November 2007 (UTC)
thread_title:  Voice of a  Distant Star 

message: The reference to "stationary" in this article when discussing special relativity is inadvisable. Among other things, it is extremely misleading to the naive reader as it conjures up the idea that there is some special frame, as in aether theory, against which (absolute) velocity is measured - even if that was not what was meant or explicitly stated. Einstein and special relativity are quite clear that all inertial frames are on equal footing and to claim that one frame, even in the context of one example, is a special ("stationary") frame is, at the very least, misleading.
I see that some here understand this:
"That animation is designed to hammer in the point that a distinction between "being stationary" and "having a velocity" does not enter special relativity, the symmetry is unconditional" - Cleonis
In particular, there is absolutely no justification to claim, "The Einsteinian takes seriously the thesis that all motion is indeed relative to some actual (if specified only by 
implication) "benchmark" that is regarded as stationary, ...". 
Hence, I would recommend changing such references and would plan to do so after, of course, waiting for persuasive feedback.
As it happens, "stationary" is also used in the article when discussing GRT and as such is not subject to the above comments. The quote is  "Thus gravitational time dilation is agreed upon by all stationary observers, independent of their altitude". As a minor note, I think it would be clearer to delete "stationary" from that sentence. (It's usually dropped as the key for agreement is not the observer's motion relative to the observed, but the observed's motion relative to one another or rather their lack of or negligible relative motion.) 
TwPx 03:00, 14 November 2007 (UTC)
replies: text: There is a responsibility at Wikipedia to keep things in layman's terms.  Using the word "putative" in front of "stationary" is a clue that there is more to it for those who wish to read on further.  This way the article increases in complexity for those who want to make the effort of reading on. Jok2000 21:47, 14 November 2007 (UTC)
thread_title:  "Stationary"?