Talk:Time dilation/Archive 2008

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Needs more Wikification?

I think the page needs to be wikified more by adding more internal links.

Thanks 62.150.221.193 (talk) 17:40, 18 September 2008 (UTC)

Relative Speed

Ok, I did try reading the article, but one thing confuses me. Ok, a man's in a ship, going really fast. I'm not talking about going faster than light, or having anything go backwards in time. But how fast would the ship have to move for everything around him to slow down? I.E. onboard the ship a day passes while outside only an hour? 68.251.175.61 (talk) 19:02, 10 October 2008 (UTC)

Pretty darn fast. Take the formula $\gamma \equiv 1/{\sqrt {1-\beta ^{2}}},\ \beta \equiv v/c$.

Invert it: $\beta ={\sqrt {1-1/\gamma ^{2}}}$. Plug in γ= 24, and calculate.

—WWoods (talk) 00:57, 11 October 2008 (UTC)

Sweet! Thank you so much! I could not for the life of me figure it out before.

Ok, so a person onboard a ship going at practically the speed of light (beta= .9991) would age 24 hours by the time he returned after only an hour had passed on earth. Thanks! 68.251.175.61 (talk) 02:56, 12 October 2008 (UTC)

Other way 'round. The traveler would return a day later than he started, but he'd only have aged an hour. See Twin paradox for more on this case.

—WWoods (talk) 16:23, 12 October 2008 (UTC)

Interesting. That's funny, cause of how popular culture gets that backwards, too. Like how superheroes move so fast everything else slows down, when everything else should speed up in relation to them, lol. Thanks for explaining it! 68.251.175.61 (talk) 22:55, 12 October 2008 (UTC)

The spacetime geometry of velocity time dilation

For simplicity consider the following animation as topic animation. As both has the same meaning.

http://www.glenbrook.k12.il.us/gbssci/phys/Class/relativity/U7l2b.html http://www.youtube.com/watch?v=KHjpBjgIMVk

Imagine the same huge clock in above link is just above the head of stationary observer. Now consider the following cases.

1- Clock is above the head stationary observer and is at rest 2- Clock is moving straight up with a speed close to speed of light in the sky or space

A light pulse goes down and up on the clock reflecting off mirrors on the bottom and top of the clock. The mover himself would see no change in both cases. But in case ii, since light never speed up therefore mover himself should sees a change in c after reflection from lower mirror, although both trips would require one second to complete. Thus it would be a threat to the concept of relativity if mover himself would sees a change. But the stationary observer would always see a pulse, a stationary point in both cases. This means t=0.

Also, for simplicity consider the diagram as shown in section “Simple inference of time dilation” of the article which shows the right angle triangle. Let this is front view for parallel observer. Now there is side stationary observer which can only see the perpendicular of triangle. Thus in side elevation the hypotenuse of triangle would be look like a perpendicular of triangle. As speed of light is constant therefore this side observer would see only the same vertical distance (perpendicular of triangle) not the longer path or hypotenuse of triangle which is made by a moving light clock for front observer. Thus for this side observer t=t.

Thus, if time dilation were true then aforementioned case is also true in which t=0 and t=t. But I would say time does not depend upon position of mover / observer but tick at same rate every where. Time is misunderstood in the theory by showing a longer path of the light wrt to the stationary observer. After firing, a pulse move vertically with c as well as also horizontally (along the ship) with v simultaneously. Thus v is added at every interval to the c component. Therefore longer path of the light should be represented by ct + vt instead of ct only in order to get the actual results. Myktk (talk) 16:08, 1 December 2008 (UTC) Khattak

Note: Position of huge clock (or mover) is vertically up means stationary observer would see both (lower and upper) mirrors as a single mirror. Top view of both should be a single mirror.Myktk (talk) 03:06, 5 December 2008 (UTC)K

Similarly in the link, If the same huge clock is placed horizontally just above the head of observer such that position of both mover and observer are in the middle of right and left mirror in top view or elevation. Both clock s would tick at same rate as both could see path of pulse exactly the same either at rest or if mover goes straight up with a speed close to c.

If a clock is really slow down then a squished distance vt should also be included in the triangle, in order to get the true picture of the thought experiment. —Preceding unsigned comment added by Myktk (talk • contribs) 20:07, 4 December 2008

Proof of Time Dilation

The proof of time dilation assumes that L is the same in both reference frames without explicitly proving they're equal. I think the proof is therefore too simple and needs modifying. —Preceding unsigned comment added by 80.2.16.248 (talk) 23:51, 9 December 2008 (UTC)

Arbitrary velocity in Overview

Where did this come from?...

The range of such variances in ordinary life, where v / c < < 1, even considering space travel, are not great enough to produce easily detectable time dilation effects, and such vanishingly small effects can be safely ignored. It is only when an object approaches speeds on the order of 30,000 km/s (1/10 the speed of light) that time dilation becomes important.

Whether Time Dilation is important is dependent on the purpose to which the measurement is put. As a simple counterexample, doesn't GPS require time dilation from both satellite velocity and gravitational potential to be taken into account?JBel (talk) 23:58, 15 December 2008 (UTC)