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

    Atomic Clock Time Dilation Experiment

    Homework Statement Two atomic clocks are synchronized. One is placed on a satellite which orbits around the Earth at high speeds for a whole year. The other is placed in a lab and remains at rest with respect to the earth. You may assume both clocks can measure time accurately to many...
  2. X

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  3. S

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  4. Nakshatra

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  5. M

    Time Dilation in a Non-Rotating Laser Sphere: Inside vs Outside

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  6. J

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  7. G

    Time Dilation and Length Contraction the same thing?

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  8. D

    Why are the effects of Time Dilation permanent but Length Contraction is Not?

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  9. PrincePhoenix

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  10. Z

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  11. S

    How can the rest observer conclude the photon travels at an angle?

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  12. P

    Time Dilation at Center of a Neutron Star

    From https://www.physicsforums.com/showthread.php?t=40391 in gravitational time dilation. At the center of neutron star PSR J1614-2230 at 1.97 SM mass of Sun 1.9891×10^30 kg mass of PSR J1614-2230. 4 ×10^30 gravitational constant = 6.67300 × 10-11 m3 kg-1 s-2 radius(rough estimate) =...
  13. Q

    Does the center of a quasar experience time dilation?

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  14. M

    Time Dilation: Exploring Effects of Relative Motion

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  15. G

    How does gravitational time dilation increase the spacetime interval?

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  16. E

    Wikipedia quote on gravitational time dilation

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  17. E

    Simple question about time dilation in accelerated reference frames

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  18. T

    Understanding Time Dilation: Exploring Relativity in Physics

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  19. G

    Calculating Time Dilation for a Spacecraft Traveling to Proxima Centauri

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  20. M

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  21. E

    Exploring Time Dilation and the Big Bang: A Question of Mass and Relativity

    I have been wondering this ever since I was in elementary school and I am hoping for an answer. The time dilation equation for general relativity is time dilation=e^(gh/(c^2)). This applies to any object that has mass, and I am wondering if it also applies to the Big Bang (which has mass). I...
  22. D

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  23. D

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  24. D

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  25. N

    Special relativity homework question time dilation

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  26. N

    Special relativity homework question time dilation

    Homework Statement You are a passenger on a brand-new spaceship that travels at 95% of the speed of light, i.e., v = 0.95 × c. The spaceship is bound for the star, Altair, at a distance of 17 light years from Earth. If the spaceship departs on your 21st birthday, at a speed of v = 0.95c, how...
  27. T

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  29. G

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  30. D

    How to explain time dilation easily to others, maybe like this ?

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  31. S

    Relativity Theory: Connecting Gravitational & Velocity Time Dilation

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  32. C

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  33. D

    Question on Time Dilation for Traveling Observers

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  34. P

    Time dilation & the first galaxies

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  35. DaveC426913

    Time dilation and relative velocity

    https://www.physicsforums.com/showthread.php?p=3577768#post3577768" has caused me to question my assumptions. If a target of observation is moving at relativistic velocities but its distance does not change wrt the observer, is it observed to be experiencing time dilation? Alice stands at...
  36. N

    Time Dilation: Two Observers, Different Times

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  37. A

    Alternative way to calculate the special relativistic time dilation factor

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  38. L

    Time dilation thought experiment clarification

    Sorry for yet another time dilation question. I have a couple example problems that I can't seem to explain. 1) A ship leaves the Sun and heads for Earth at 0.5c. An observer on Earth would see the the light from the sun take 8 min, and the ship take 16 min. The pilot's clock would show it...
  39. E

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  40. U

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  41. B

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  42. F

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  43. J

    Understanding Aging and Time Dilation: The Twin Paradox Explained

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  44. N

    Does Earth's Elliptical Orbit Affect Time Dilation Due to Gravity?

    Relative some arbitrary point in Earth’s orbit around the Sun, does Earth experience varying degrees of time dilation specifically from gravity? With Earth's orbit around the sun being elliptical I wondered if Earth experiences varying degrees of time dilation caused by the suns gravity (or...
  45. S

    Time dilation and length contraction problem

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  46. K

    Time dilation and length contraction in hyperbolically-curved spacetime

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  47. T

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  48. A

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  49. N

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  50. D

    Does expanding space affect time dilation etc?

    In special relativity we have the velocity 'u', being the difference in speed between two objects, from which we work out time dilation, length contraction etc. But if those objects are separated by some expanding space, but not moving with respect to that space, is there still the dilation...
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