What is Time dilation: Definition and 999 Discussions

In physics and relativity, time dilation is the difference in the elapsed time as measured by two clocks. It is either due to a relative velocity between them (special relativistic "kinetic" time dilation) or to a difference in gravitational potential between their locations (general relativistic gravitational time dilation). When unspecified, "time dilation" usually refers to the effect due to velocity.
After compensating for varying signal delays due to the changing distance between an observer and a moving clock (i.e. Doppler effect), the observer will measure the moving clock as ticking slower than a clock that is at rest in the observer's own reference frame. In addition, a clock that is close to a massive body (and which therefore is at lower gravitational potential) will record less elapsed time than a clock situated further from the said massive body (and which is at a higher gravitational potential).
These predictions of the theory of relativity have been repeatedly confirmed by experiment, and they are of practical concern, for instance in the operation of satellite navigation systems such as GPS and Galileo. Time dilation has also been the subject of science fiction works.

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  1. H

    Time Dilation: What's the Rest Frame?

    I really don't quite understand the result of time dilation. Let's say that we have two identical twins A and B. Twin A is at rest and twin B is on a high speed rocket ship. Let's say that 10 years has passed in frame A. According to relativity, the twin in frame B is supposed to measure less...
  2. P

    Time dilation due to SR plus GR

    So I've been trying to find an equation that will represent total time dilation. I've looked through a couple threads and it seems the consensus of the threads I've seen on the topic say that total time dilation is the product of time dilation due to velocity and gravity. But I'm not clear...
  3. J

    Time Dilation: Clark Kent's Scenario

    I understand for the most part how Time Dilation works. I understand that time slows down that for the individual traveling at the speed of light and that the rest of the world moves on. So my question is illustrated by the following scenario: I have an individual, let's say, Clark Kent...
  4. inflector

    Another Way of Looking at Gravitational Time Dilation?

    https://www.physicsforums.com/showthread.php?t=433866" that relativistic time dilation does not depend on acceleration, i.e. that there are instances where the acceleration might be zero while there would be significant time dilation. The example in the other thread was gravity and acceleration...
  5. T

    Time dilation or length contraction

    Hi, i asked some quesitons about this before but i need a clarification. Generally we use vertical light clocks and compare the distances taken by light and since c is constant the longer path taken by the light means a dilation in time, from here we say every other type of clcok dilates in same...
  6. C

    Time Dilation: Does Aging & Decay Slow Down?

    I understand that time dilation means that the closer to the speed of light an object goes, the slower time seems to pass relative to a stationary observer. My question is, if time seems to slow down in the spaceship moving at something close to the speed of light, then would other time related...
  7. J

    Does Gravitational Time Dilation imply mass change?

    According to Einstein's Gravitational Time Dilation, if an oscillating physical system is elevated to a height H above the Earth then in oscillates at a higher frequency than the same system at ground level. According to Planck's relation between Energy and frequency this must mean that the...
  8. R

    Understanding Time Dilation: Confusions and Questions Answered

    In the proof of time dilation. Below http://www.phys.unsw.edu.au/einsteinlight/jw/module4_time_dilation.htm I have a doubt in symetry of time dilation. If there's a big lcd screen digital clock in jasper's verandah(at rest wrt ground). And zoe is moving at speed close to c. Do he see that lcd...
  9. Z

    Time Dilation & Black Hole Mergers: Exploring Ringdown Gravitational Waves

    Time dilation and black-hole--black-hole mergers, and ringdown gravitational waves An observer far away from an event horizon never sees a particle cross the event horizon. How does this effect the apparent merger of two black holes? Also, I've seen that the gravitational waves during the...
  10. B

    Time Dilation Debate: Arguments For and Against

    I am interested in a reason as to why time dilation is not possible. I have done some sloppy google research and have found few people that think it is false. Is there anyone that could give me a basic explanation of why it might not be true? other than the fact there is no proof of it.
  11. A

    Voyager probes and time dilation

    The Voyager probes are traveling at non-relativistic speeds, at the edge of the solar system where the gravitational field is about 0 so we could consider them a rest frame. If so, from my calculations using the formula for time dilation: \tau(t) = \frac{c}{g} \operatorname {arsinh} \left(...
  12. I

    Age comparison to observer on Earth (time dilation)

    Homework Statement Alpha Centauri is about 4 light years from the Earth. If you were to travel to Alpha Centauri and back at the speed of the electron that you calculated in question A (0.780c), how much would you age compared to an observer on Earth? Homework Equations There equations...
  13. T

    Acceleration and Time Dilation

    If an observer is in a rocket traveling at a constant speed, both the rocket and the observer are in the same frame of reference - right? Anything influenced within the frame of reference will behave the same regardless of speed. The closer a rocket gets to the speed of light, the speed limit...
  14. D

    Beginner's questions on time dilation

    Hello, I just started taking a Modern Physics course in University, and have a moderate understanding of time dilation. The problem is that I'm stuck with a problem I asked myself. I understand the light clock thought experiment. If you are within a rocket ship moving at a fast speed and a...
  15. K

    I understand time dilation with light clocks, but

    Imagine I were to make a light clock by placing two mirrors facing each other, with a photon bouncing between them vertically, such that one complete round trip for the photon takes exactly one second. I understand that if this contraption were moving horizontally at significant speed, an...
  16. A

    Exploring Possible Causes of AF's Time Dilation in yuiop's Thread

    This is related to another current thread https://www.physicsforums.com/showthread.php?t=426307" wherein yuiop presents a very convincing demonstration of non-reciprocal proper time differential between an accelerated system AF and an inertial system IF between two points A and B In...
  17. R

    Atomic Level Time Dilation Resources

    Hi, I'm looking for any resources explaining time dilation at the atomic level. I can't find anything on it sooo If anyone could please refer me that would be helpful. kind regards
  18. barnesbb

    Time dilation due to relative velocity

    Hi all, I have been interested in the Theory of Special Relativity for the past few years, and there is something I'd like to discuss. Somebody else may be discussing this elsewhere but if there is I haven't been able to find them. I have never felt comfortable with time dilation due to...
  19. R

    Exploring Time Dilation in a Subatomic World

    Hi I'm not a physicist, but I have a keen passion for physics. If we could shrink a clock down to the smallest particle we know, and smaller. Then observe it. Would we witness a time dialation? Then, if we had to repeat this experiment, glueing the clock to the smallest particle we know...
  20. T

    Regarding quasars not showing signs of time dilation.

    Here's the article http://news.discovery.com/space/no-time-dilation-for-distant-quasars.html So the distant quasar is more red-shifted than the closer one, which means the farther one is traveling at a higher velocity, makes sense. My thought is if the quasar is "riding" if you will...
  21. atomqwerty

    Time Dilation: Cells Divide on Earth & Travel to Sun

    Homework Statement Two cells that divide on Earth each 10s start a travel to the Sun at v = 0.85c (Distance earth-sun: 1.5·10^11 m). How many cells should exist when the rocket they travel in carshes with the Sun? Homework Equations Time dilation: t=t0/sqrt[1-v2] being t0 the time from a...
  22. P

    Question about calculating time dilation of clocks at sea level

    I am trying to understand how relativity explains that clocks all over the globe count at about the same rate at sea level. One of the papers that I have looked at is "The global positioning system, relativity, and extraterrestrial navigation" at...
  23. TrickyDicky

    General relativity time dilation

    Accordingto GR, as an object gets farther from a massive body , its proper clock runs faster than the clock of an object nearer to the massive body. So would the planet Pluto for instance measure time significantly faster than we on earth, being further from the sun than us? If so how could I...
  24. M

    The scope of inertial time dilation?

    I am trying to resolve a number of questions concerning the scope of time dilation within the confines of special relativity, i.e. flat spacetime. For example, if I simply state that 2 inertial frames of reference pass each other with a relative and constant velocity [v], it is my understanding...
  25. atomqwerty

    A question about reference system and time dilation

    Hi everyone, These days I've been reading about relativity (special) in a book of general physics, and I have a doubt about the reference system: If I stay on Earth and I observe a rocket traveling away from the Earth with a great velocity (let's be 0.5c), and I notice that time inside the...
  26. A

    Non-reciprocal Time Dilation

    This is a very simple scenario. Given: Earth (E) t=0, x=0 ,and a station (Stn.) at rest wrt (E) at 100 ls,...t=0, x=100 And a ship S which instantaneously accelerates to 0.8c at t=0, x=0 and t'=0. At t,t'=0 all three systems begin sending simple quantitative sequential time...
  27. K

    Time dilation or time relativity?

    Are these terms synonyms or do they actually mean different things? I see both refer to the same phenomenon but it looks as if "time dilation" assumes the point of view of only one observer whereas "time relativity" or "relativity of time" seems to include all the observers. Still, most...
  28. A

    TIme Dilation & Quantum Entanglement Question

    Yesterday, my 12 year old nephew asked me a physics question after we watched a documentary about Einstein and relativity on the science channel. I know just enough about physics to be dangerous, and I can usually answer his questions but this time he had me stumped, and I couldn't find...
  29. S

    Why is my calculation for velocity using time dilation and speed incorrect?

    Homework Statement was a home work problem. I am redoing it for practice im stuck on part c this is the hint for part C Homework Equations t=T/(1-(v/c)2)1/2 The Attempt at a Solution my attempt. i know that from the restaurant to school it will take 15 min in school's...
  30. D

    Time dilation inside the second horizon of the BH

    Here is an example, where time dilation is coordinate-independent. Alice freely falls into the rotating BH. When she crosses the second horizon, she stops and hovers (enjoying the spectacular view of the naked ring singularity). As ring actually repels in some places, she would be safe and...
  31. N

    Is Time Dilation Just an Illusion?

    One commonly quoted example of speedy things ‘living longer’ is the accelerated Muon. If you accelerate a beam of muons in a circular synchrotron and accelerate them to .99c then the muon lifetime is increased by a factor of 100. Quite a significat value and not one that could be fobbed off...
  32. Z

    What Causes Time Dilation Between Two Objects?

    I have been curious about the concept of time dilation. what is it exactly? and I am not talking about how it occurs, but the force that exist that makes it change or alter the similar state between two objects in two different places. example would be the twin paradox or the Muon tests...
  33. D

    Time Dilation Basics: What It Means for Space Travel

    Sorry, this is a very novice question. If I was floating in space and saw a spaceship go past at (0.75)^0.5, would every 2 seconds for me, be one second to the spaceship?
  34. P

    Does Time Dilation Explain the Lack of Effects in Quasar Light Curves?

    On a paper published recently by Hawkins (not Hawking): Comments? Opinions? http://www.physorg.com/news190027752.html http://www3.interscience.wiley.com/journal/123345710/abstract?CRETRY=1&SRETRY=0
  35. N

    Is Time Dilation Caused by Motion or the Fabric of Time Itself?

    Hi. It's known that for an object in a motion relative to another, time will slow down. Now the question is why? Is it merely the mechanical effect that since the object is in motion, all its processes (which are practically motion of particles within the structure) now have to travel further...
  36. G

    Time Dilation: Solving Brian Greene's Example w/ Math

    I was reading The Elegant Universe by Brian Greene and I wanted to see how to do one of his examples with math. Here's an excerpt: I believe I've included all the relevant information. If not let me know what I'm missing. I would like to understand the math behind this.
  37. N

    Cosmological Redshift in FRW Coordinates – Energy Conservation & Time Dilation

    I want to discuss energy conservation and time dilation relative to the cosmological redshift. Because the elements of the redshift are coordinate specific, I’ll focus just on the FRW metric using proper distance coordinates (not comoving coordinates). As explained in Tamara Davis’s cover...
  38. R

    Time dilation and length contraction for rotating black holes

    hello, how is it possible to calculate the only GRAVITATIONNAL time dilation and length contraction factor in the Kerr metric and/or the Kerr-Newman metric, for an object falling but otherwise at rest, since there is frame dragging, and the metric contains dt^2 components but also dt.dphi...
  39. R

    Spacetime / Time Dilation Question

    As I understand it, anything that is traveling at the speed of light moves through space but not through time. So if we were able to track a photon from the surface of the Sun, we would say it took about 8 minutes for the photon to travel to Earth. However from the photon's point of view, it...
  40. Q

    Exploring the Time Dilation Effects of Acceleration & Gravity

    Time Dilation- slowing or speeding up time. Acceleration Time Dilation as an object travels faster time will slow down. If an object were traveling 10,000 mph for a few days the time dialtion would be in nanoseconds, but if an object were traveling the speed of light time would "stop". The time...
  41. D

    Gravitational time dilation on a non-spherical object

    A radius is required for this relativistic formula: t=\frac{1}{\sqrt{1-\frac{2GM}{Rc^2}}} However, I notice that some objects are not spherical. Because of this, I am unsure of how to calculate gravitational time dilation for different shapes. Could somebody help me with this and provide...
  42. B

    Exploring Gravitational Time Dilation: A Brief Overview

    http://en.wikipedia.org/wiki/Gravitational_time_dilation Having trouble understanding this, any posts will help. cheers, BT
  43. A

    Space traveler and time dilation

    Maybe some one can help clear up a problem. According to Wikipedias article on time dilation “In the case that the observers are in relative uniform motion, and far away from any gravitational mass, the point of view of each will be that the other's (moving) clock is ticking at a slower rate...
  44. Fredrik

    The terms length contraction and time dilation

    The terms "length contraction" and "time dilation" Is there a particular reason why we say length contraction but time dilation? A Lorentz transformation \Lambda=\gamma\begin{pmatrix}1 & -v\\ -v & 1\end{pmatrix} takes \begin{pmatrix}1\\ 0\end{pmatrix} to \gamma\begin{pmatrix}1\\...
  45. E

    Resultant time dilation from both gravity and motion

    When a frame is moving in relation to an observer in his rest frame at infinity, and the frame is in a gravitational well, is the resultant time dilation simply the sum of the motional and gravitational dilation, e.g...
  46. mathyou9

    Question re: time dilation equations

    For both time dilation equations (kinematic and gravitational) I have often seen \Delta t^\prime = \frac{\Delta t}{\sqrt{1-(v/c)^2}} and \Delta t' = \frac{\Delta t}{\sqrt{1-\frac{2GM}{rc^2}}} I'll calls these equations as "Set A" ------------------------ And at other times as...
  47. M

    Need Help on Time Dilation and Relativity

    I need to give a presentation on some of the physics of space travel. One of the things i will be covering is Time Dilation and Relativity. I am not too knowledgeable about this subject. What are the main topics of time dilation and relativity that i should present? I need this info as soon as...
  48. Z

    Gravitational time dilation, redshift and doppler

    If as a result of the equivalence principle we can derive the gravitational red shift entirely from the perspective of an accelerating body with no reference to gravity and no reference to gravitational time dilation then one is essentially just working out the Doppler shift of a signal...
  49. jaketodd

    Time dilation where there is no net gravity?

    Imagine a low-mass object between two massive objects. Their configuration is such that the low-mass object does not move due to the gravity of the two massive objects. Since the gravity is canceled for the low-mass object, is the time dilation canceled as well for the low-mass object...
  50. jaketodd

    Time dilation by homogeneous distribution of massive objects?

    If a low-mass object is surrounded by massive objects homogeneously so that the low-mass object does not experience acceleration, then is there any time dilation due to the gravitation from the massive objects? Thanks, Jake
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