What is Dilation: Definition and 1000 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. P

    Time Dilation - Clock running slower?

    Hi, I am having a hard time understanding one thing about this experiment for Time Dilation. I have one observer on a moving train measuring the time it takes for light to travel a distance d and be reflected back and one observer who is stationary, watching the same events. I understand the...
  2. C

    Time dilation around a planet.

    If I wanted to figure out the gravitational time dilation at different points in a the field around earth, could I just use v=gt. and find the speed that I would be moving if I went into free-fall from point x to point y. To figure out the time difference between x and y? and the t in v=gt...
  3. S

    Gravitational and movement related time dilation

    Consider a massive object moving close to the speed of light. Imagine it travels close to a black hole, but does not enter the black hole. How do you calculate the exact time dilation experienced by the massive object's reference frame? How does time dilation due to movement stack with...
  4. coktail

    Are massless objects immune to time dilation?

    Imagine there is a train moving at .9c with a person on the train and an observer on a platform watching the train go by. The person on the train walks forward while shining a flashlight. To the observer on the platform, the person on the train is time dilated and walks forward in "slow...
  5. A

    Why does Bailey experiment not show gravitational time dilation?

    Question: Why is the Bailey et. al. (1977) muon storage ring experiment not considered a refutation of GR, rather than being a corroboration of SR theory? It seems to establish that only velocity is the cause of time dilation, and the very high acceleration (order of 10^18g) plays no part in...
  6. khurram usman

    Time dilation in the period of a pendulum

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  7. J

    Points of reference for time dilation

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  8. coktail

    Relativistic mass, time dilation, length contraction, and traveling near c

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  9. A

    Black Hole Time Dilation: Light-ray Interpretation

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  10. soothsayer

    Why is gravity the only force the causes time dilation?

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  11. C

    Time Dilation in QM: Elevator Experiment

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  12. David Carroll

    Does time dilation effect rate of isotope decay?

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  13. N

    Thought experiment about time dilation

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  14. P

    Exploring the Mechanics of Light, Length and Time Dilation

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  15. E

    Time Dilation with objects at low speeds

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  16. P

    Special Relativity: Time Dilation and Length Contraction

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  17. C

    Does Time Dilation Occur When Orbiting Around a Planet?

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  18. M

    Time Dilation: Self-Consistency Problem Explained

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  19. G

    Time dilation when falling into a black hole

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  20. P

    Photon Clock & Time Dilation: Rotating the Clock 90 Degrees

    In the case where you have a photonic clock bouncing a photon between 2 mirrors, if the mirrors are alligned on the vertical axis, bouncing the photon up and down and the overall clock traveling along the horizontal axis, then the whole thing makes sense to me. However, if you were to rotate the...
  21. B

    Real vs Simulated: Examining Time Dilation in Relativity

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  22. M

    Time Dilation Formula: Travel at Speed c = Infinite Time?

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  23. FOIWATER

    Object Approaching Black Hole: Time Dilation & Visibility

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  24. M

    Time Dilation in Childrens Cartoon

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  25. Q

    Should I think of gravity/ time dilation as directional?

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  26. P

    Time Dilation and Muon Energy vs. height (Muon Experiment)

    Hey guys The lab manual for the class is found here http://advancedlab.physics.gatech.edu/labs/Muons/Muons.pdf One of the things, I was interested in figuring out was what would be the minimum height needed to put a moun detector (currently at ground level) in order to detect a minimum 1%...
  27. coktail

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  28. F

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  29. S

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  30. S

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  31. Q

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  32. JimiJams

    Time Dilation and The Twin Paradox?

    Hey everyone, I've searched the threads for an answer to my question but came up short. Basically what I want to know is how does time dilation relate to the twin paradox. I'm a newb to relativity and just started reading about it last night. I hit this bump and I'm trying to get over it...
  33. E

    A time dilation thought experiment

    Let's say we have two objects in space, far from any gravitational source. In each "object", there's an observer, and a clock. Each observer is constantly looking at both clocks(his and the other object's). Now, for observer A, observer B is moving at 0.9c, and for observer B it's the exact...
  34. G

    Misunderstanding time dilation and length contraction

    hi sorry about my english. i am from france. i have a few questions about the image i have found in my schoolbook that i attached to this post. there is a light signal moving up and down and each time it reaches the upper mirror this is somehow detected. there are also two observers: one...
  35. N

    How does time dilation effect civilisations?

    Say we had two different civilisations in two different galaxies and an observer in a neutral area of space between the two. We are going to have a race to see which civilisation can develop technology the fastest and reach the observer before the other, both are of the same species and have...
  36. V

    Red shift and blue shift as relating to time dilation

    I was listening to a lecture about the expansion of the universe and found myself confused about the light we see from very distant galaxies. These galaxies are red shifted because they are moving away from us and the photons are being stretched. Does this mean that the galaxy will appear to...
  37. C

    Free-fall and time dilation.

    If I am in free-fall and then I throw a clock above me so that it is moving away from me at a constant speed, can I just use regular time dilation to see how time is flowing in the clocks frame relative to my frame? Or do I need to worry about gravitational time dilation.
  38. G

    Time Dilation: Why Do Observers Measure Different Times?

    hi i have some troubles to understand something properly: if oberserver A is not moving in his inertial frame and there is some observer B moving relatively to oberserver A with velocity V, then this observer B will measure a different(shorter) time from the one that is measured by observer A...
  39. H

    Time dilation time interval

    Homework Statement We observe a spaceship moving away from the Earth at a velocity of v = 0.866c. The spaceship emits two light signals, the second one 4 seconds (Delta T') after the first one (measured on board). What is the time interval (Delta T) between the arrival of the two light signals...
  40. A

    Conceptual problem with time dilation and simultaneity

    All, I am having a problem resolving the common examples that are used to explain time dilation as a consequence of the constancy of the speed of light. I can't help but assume that there is something simple and fundamental that I'm missing here. I apologize in advance for forcing you to use...
  41. U

    Time dilation of Muons and a Paradox

    Hello Friends, Consider a Linear accelerator, at the one end there is a Muon Generator, and it produces a certain amount of Mouns, let's say 'x'. These Muons are accelerated to the other End of the accelerator, where the number of Muons reached are detected and displayed on a Digital display...
  42. R

    Understanding Time Dilation: Explaining the Constant Speed of Light

    I've read that time and space dilate under acceleration to ensure the constant speed of light. I'm having trouble visualizing a scenario that illustrates this concept. Could someone please explain this to me? Thanks.
  43. T

    Exploring Time Dilation in Special Relativity: A Self-Taught Perspective

    I need some help to answer a question as my physics background, while self taught, still has some holes both from following only specifics and gaps since studying it. The question is below. "is there a reputable function for the effect of time dilation in special relativity or is just...
  44. coktail

    Relative motion and accumulated time dilation

    I have a few questions about time dilation and how it accumulates. 1a. Say you have a situation where you have two clocks that move away from each other with symmetrical acceleration and relative motion. From what I understand, each clock would appear to have slowed down relative to the...
  45. U

    Speed of the light and dilation of time

    If I am 35 years old and I am in a train sitting in a special tube that is built around the entire circumference of the planet. Putting aside all of the questions of practibility and g forces and the like, if the train I am in accelerates to just a hair under the speed of light and I travel on...
  46. M

    What exactly is Time Dilation?

    So I know it has to do with reference frames and such, and I know that it is all about time relative to different observers, what I don't understand is how exactly is it that when you're moving at a speed close to 'c', you actually physically experience a different time interval than someone who...
  47. G

    How does the time dilation is being measured using atomic/quartz clocks?

    I understand time dilation exists according to relativity theory. But what I'm not able to understand is this statement, "clock is ticking faster/slower on a moving object compared to observer". How is that possible to measure it? or how does the clock (atomic/quartz) it experience the time...
  48. K

    Confused about seeming recursivity of time dilation between two moving bodies

    I only just started learning about special relativity in my physics class, and I have been running into a problem that none of my teachers have satisfactorily explained. Objects X and Y are moving relative to one another at some significant fraction of the speed of light, where ɣ is the...
  49. bayan

    Time Dilation at very slow speeds.

    Homework Statement Hi, I have a question which asks me to find the time difference (difference between a stationary frame and one that is moving at 30m/s for 1 hour) it has asked me to use binomial approximation and I am kind of lost as to what I need to do to solve the equation. Homework...
  50. S

    Speed of the light and time dilation

    Lorenz-factor has remarkable influence at speeds near to light, but formula itself has no limits. So, time dilation occurs also with slow speeds. From my point of view (an observer), Venus and Mars have different speeds which means different time dilation and this means different speed of...
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