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. B

    I Issue With Derivation of Gravitational Time Dilation

    Why do we use the equation ##\frac {1}{2}mv^2 = \frac {GmM}{r}## to derive potential velocity, and then put that in the Lorentz factor in order to derive gravitational time dilation? Shouldn't we be using the relativistic definition of kinetic energy -> ##mc^2(\gamma - 1)## to derive the...
  2. A

    I Falling Into a Black Hole: Time Dilation & Hawking Radiation

    I know that has been discussed elsewhere but never could find for a satisfying answer, so I try this here again. Let us not take into account that an observer (an astronaut or a clock or just let us take both: an astronaut with a clock) falling into a black hole (BH) will be killed and torn...
  3. mrSpring

    I Time Dilation Effects - Understand without Clocks

    So I am having some hard time understanding exactly the effect of moving near light-speed on time. Most of the examples mention clocks as a way of measurement but I can understand why would a clock which is a mechanical or electrical device for measuring time would be effected with motion. That...
  4. N

    How can the time dilation equation explain faster moving clocks running slower?

    Since for the two events of Samir starting the stopwatch, and the stopwatch reaching 10.0s, Samir and his stopwatch are stationary from his own frame of reference, I said it was the proper time and that delta t0 = 10s. Then the speed of the moving frame of reference was 0.6c. I thought placing...
  5. S

    B How much time dilation is there as time passes?

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  6. S

    Effect of time dilation on a satellite

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  7. benorin

    B Can Atomic Clocks Yield the Same Time Dilation Equation as Light Clocks?

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  8. Buckethead

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  9. sweet springs

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  10. M

    Length Contraction & Time Dilation

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  11. Z

    I Gravitational Time Dilation: Radius & Clock Rate Variation Explained

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  12. P

    B Does Gravitational Time Dilation Affect How We Measure Time on Earth?

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  13. G

    B Muons traveling to Earth, time dilation question

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  14. A

    I Calculate mass from time dilation

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  15. DaveC426913

    B Cause of time dilation when net gravity is zero

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  16. E

    I Second Derivative of Time Dilation Equation

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  17. W

    B Time dilation and Einstein's theorem

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  18. T

    How do proper time and time dilation differ?

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  19. H

    B What Happens When We Cross the Event Horizon of a Black Hole?

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  20. S

    B Can gravitational time dilation explain the galaxy rotation curve?

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  21. N

    B Time Dilation Problem with Mesons

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  22. L

    B I got confused about SR after trying to reply to another

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  23. C

    B Time Dilation Theory Flaw: How Can They Be Different Ages?

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  24. Ennio

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  25. R

    B Does time dilation prove the existence of an absolute zero velocity?

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  26. bland

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  27. P

    B Exploring Time Dilation and the Galaxy: Effects of Gravity and Angular Velocity

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  28. Freonpsandoz

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  29. Sandip Patel

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  30. S

    B Take on Length Contraction at relativistic speeds

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  31. D

    I Time dilation for the Earth's orbit around the Sun

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  32. P

    B Math-Based Time Dilation Paper: Seeking Suggestions

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  33. K

    I Gravitational time dilation derivation

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  34. S

    Time Dilation in a Sci-Fi Novel

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  35. Exidor

    I Time dilation vs. the Doppler effect

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  36. zox00

    I Deriving Lorentz from time dilation and length contraction

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  37. Biker

    I Time Dilation in SR: Exploring Clocks & Perception

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  38. Mr C Odd

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  39. J

    Should I use time dilation or length contraction?

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  40. P

    SR - Time dilation, space-time diagram, and radio signals

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  41. jha192001

    I Time Dilation: A & B's Age Difference

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  42. J

    B Gravitational Time Dilation: Math Formula for Clock-Slowing Factor

    What is the mathematical formula for the time dilation (clock-slowing factor) for a clock in a gravitational field g, equivalent to the Lorentz factor γ for a clock traveling at a relative speed v?
  43. Jazzyrohan

    I Time Dilation Explained: Feynman Lectures 15-4

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  44. Amaterasu21

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  45. Jazzyrohan

    I What is the physical cause behind time dilation?

    Time dilation can be shown mathematically but what is the physical phenomenon due to which it occurs?
  46. N

    I What I understand about Time Dilation

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  47. F

    I Reconciling two observers in two frames

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  48. B

    I Differential equation from derivative of time dilation

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  49. F

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  50. P

    I Gravitational time dilation - acceleration vs potential

    What I know gravitational time dilation (based on GRT) is dependent on gravity potential and not on gravitational acceleration. That would mean, that for example in center of Earth is the gravitational acceleration zero, but the gravitational potential is bigger than on the surface of Earth...
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