Time dilation Definition and 999 Threads

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. J

    Does Entering a Black Hole Speed Up Universal Aging?

    Would the universe end if you entered a black hole? What I mean by this is that due to time dilation would time elapse so fast for the universe outside the black hole relative to you inside it that all the stars would burn out and all that wouild be left would be other black holes?
  2. P

    Time Dilation on Earth: Why Hemisphere Matters

    Does time go slower on the hemisphere of Earth that is currently rotating counter to Earth's orbit than the side the side that is rotating with Earth's orbit
  3. Candidus

    Generalisation of Time Dilation

    Hi. If calculations of the Lorentz factor are by thought experiments using the constancy of the speed of light in inertial frames (I also know of using simultaneous equations for a light signal in two different frames with a conjectured Lorentz factor to calculate it but this also involves...
  4. R

    Question About Gravitational Time Dilation

    According To Einstein's Relativity. Supposing a Man Went To Another Planet That Has a Gravity More Than Earth Hundreds Of Time Which Means That Time Is Too Slower There Than Earth. If We Say That 1 Hour In That Planet Is 10 Years On Earth And He Stayed 2 Hours There Will He Comeback To Earth...
  5. M

    Relativity question involving time dilation

    Homework Statement A muon has a lifetime of 2.20 x 106 s when at rest, after which time it decays into other particles. A) Ignore any effects of relativity discussed in this section. If the muon was moving at 0.99 c, how far would it travel before decaying into other particles, according to...
  6. C

    Black Hole Time Dilation And Observation Of Accretion

    Hello. If time is infinitely dilated at the edge of the EH, how do we observe accretion?
  7. SpiderET

    Some easier equotation for gravitational time dilation?

    Im looking for some easy equotation which would help me to make graph of time dilation depending on gravity expressed not in relation to Schwarzschild radius but simply and directly to gravitational acceleration. I would like to get some easy graph similar to this...
  8. P

    Symmetrical time dilation implies relativity of simultaneity

    This is something I've been meaning to write for a while, I finally got the time to do it, though the topic isn't currently "hot". I'm sure it will pop up again, though. Imagine we have two observers, moving at a constant velocity relative to each other far away from any objects that might...
  9. E

    Distance from Black Hole to experience Time Dilation

    How close do you have to be from a black hole to experience noticeable time dilation. I always believed you will not experience noticeable dilation until you are at or in the event horizon is this correct? Also does rotation/spin of mass such as a planet decrease it's inherent gravitational...
  10. thrush

    Time Dilation: SR Basics & Confusion

    Hi everybody, I'm learning Special Relativity, and probably ok with four vectors, the metric equation, the Lorentz Transform, and the Doppler shift, etc., but enough about me. I'm still a little confused about time dilation. In several hypothetical examples of SR that I have seen, two...
  11. L

    Time Dilation: Does Total Speed Matter?

    When a spaceship accelerates to 1.000 kmh, the effect of time dilation is tiny. But what happens if this spaceship accelerates in an inertial frame whose total speed is much slower or whose time goes much faster, will the time dilation effect be the same? If the spaceship travels in a inertial...
  12. Grimble

    Time dilation: speed relative to what?

    I have been asked about time dilation which I thought I understood, but maybe you can help me provide an answer? If a spaceship is traveling at 0.866c then time will slow by a factor of 2 due to the speed the spaceship has. Why? If it is alone in space, light years away from any other body...
  13. E

    Time Dilation & Visual Observation of Black Holes

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  14. Michaelcomputer

    Is it possible that black holes create dark matter/energy?

    Wondering if it's possible that black holes create dark matter and dark energy from the matter and energy they consume. Then, inflation might slow when supply is low. This would support author Tarō Gomi's theory that "everyone poops." What role would time dilation play if that's what's...
  15. DDov

    Time Dilation & Tunnelling Probability in Double Potential Wells

    Assume you have a 2 particles sitting inside a double potential well. Each particle occupies one side of the well and given enough time the particles may both be found on the same side or swap sides (tunnelling). Assume that the well is inside a gravitational field. It is positioned in such a...
  16. D

    How does GPS correct for time dilation?

    Hi all,as I understand it, GPS satellites are offset prior to launch in order to correct for the time dilation that they experience in orbit. I am very confused about how this works in practice. I think the velocity of a GPS satellite wrt a position on Earth would depend on the position on Earth...
  17. julianwitkowski

    Time Dilation Effects on Observer Perception

    If an observer was traveling with a Lorentz factor that would make that observers time slower than someone's on Earth, what would that observer see watching a live video feed, or if it was possible to observe Earth with a telescope, and vice versa? I understand that either party would only see...
  18. 1977ub

    Time Passes Faster: Moving Frame w/ Many Clocks

    I had asked this about 2 years ago - but for the life of me cannot find it. Please feel free to cancel this if you can find my OP. Anyhow my question was this: A "train" passes by at significant relativistic speed, along the "x" axis. "Platform" observer peers in windows of train as it passes...
  19. S

    Time dilation in the field interpretation of GR

    IIUC, there are two different interpretations of GR - either as curvature of space time (as in Misner Thorne Wheeler) or as a (spin-2)field that influences all matter (as in the books by Weinberg or in the Feynman Lectures on Gravitation) and that leads to the underlying Minkowski metric being...
  20. Rene Manzano

    Time Dilation Confusions - A Physics Newbie's Questions

    Hello! I have some confusions about this topic, I'm a physics newbie so my question may have no sense, please have mercy ;). It's supossed that relativity only considers observation as valid "what we see", but observation it's independant of what we know (we can't tell how distant we are from...
  21. R

    Special Relativity WS#2 -- Earth-Pluto SuperShuttle line time dilation

    Homework Statement The new earth-Pluto SuperShuttle line boast that it can take you between the two planets (which are about 5.0 h apart in distance) in 2.5 h according to your watch on board the shuttle. Assume that the shuttle travels at a constant velocity. a.) What time interval must the...
  22. S

    Do gravitational time dilation effects cancel out or add up?

    If we use one gravitational field in GR and try to desribe it, we will see that from the perspective of the observer on the centre of mass of the object the clock on the hovering observer (farther away from the gravitational field) runs faster, while from the hovering observer's perspective the...
  23. THE HARLEQUIN

    A problem regarding time dilation

    two spacecraft s travel parallel to each other along straight lines AB and CD as shown in the picture here ... while s1 moves with a simple harmonic motion , s2 moves with a constant speed and only at points A and B it gets enough thrust within a very negligible time to reverse its direction of...
  24. THE HARLEQUIN

    S DILEMMA: Time Dilation in Simple Harmonic Motion?

    i have been wondering about this for a while ... suppose , a spacecraft in space moves with a simple harmonic motion ( e.g. on a straight line ) between points on space A and B . it fires a rocket from point B that travels with a speed .9c ... now if the rocket comes back to point B after a...
  25. I

    Rotating Disk and Time Dilation

    My question is about comparing the time dilation of a clock on a spinning disk versus a clock in the vicinity of a massive object. It seems there should be a connection between the two, because of the equivalence principle, but I'm missing something because I don't quite get the answer I would...
  26. L

    Would the Big Rip make time stop?

    Would an accelerating expansion create any time dilation effects? And once the expansion velocity between any two adjacent points reached c would time stop altogether?
  27. C

    Relative velocity time dilation question

    Since relative velocity time dilation is due to an increase in velocity, with a person moving faster moves through time slower than those on earth, does it follow that it's possible to move slower than the Earth and therefore move through time faster than them? Because the Earth is moving...
  28. B

    Time Dilation Effects on a Probe

    I was having a discussion with a colleague earlier today regarding exoplanet exploration. Being that the biggest challenge for mankind to travel to distant planets is that time dilation would make such an extreme effect that by the time we reached our destination thousands of years may have...
  29. D

    Time Dilation & Foreshortening: Understanding the Twin Paradox

    As I understand time dilation, at 90% of the speed of light, a space traveling twin would age at a rate 44% of his/her twin on earth; at 99% it would be 14% and at 99.9% it's 4.5%. And these differences would be permanent. Since relativity explains things in terms of spacetime, does this mean...
  30. A

    Get confused about time dilation

    When the observer B is traveling at a very high speed, the observer A on the ground will record a time dilation. But at the same time,from the point of view of B, A is also traveling at a very high speed relative to B. Here comes the question:does that mean they both record the time...
  31. E

    How does time dilation affect the perception of light speed in a moving plane?

    Homework Statement A plane is moving at a constant speed of 300m/s. If you are inside and you shine a light towards the back of the plane, how will light appear to move from the Earth's frame of reference? Homework Equations None The Attempt at a Solution Light always moves at 3x10^8 m/s so...
  32. Labyrinth

    Looking for 'absolute still' with time dilation

    I looked through this thread here regarding how fast we're moving relative to the CMBR, but I wonder if it would be hypothetically possible to get an even better measurement while also looking for a decent value for 'absolute still' using the apparent asymmetry of time dilation/constriction. A...
  33. Serious Max

    Time Dilation Explained by Stephen Hawking: 1 Day = 1 Year?

    Here (at ~3:50) they say if the ship reaches 99% of the speed of light, a single day on the ship = year on Earth. But it looks like it's going to be one week on Earth. http://cosmology.com/images/3TimeDilationTable1.jpg Is it just a simplification of some sort in the video?
  34. dragoneyes001

    Exploring Time Dilation: The Effects of FTL Communication on Twin Observers

    EDIT: split from "twin paradox with a twist" thread Re: https://www.physicsforums.com/threads/twin-paradox-with-a-twist.791673/page-5#post-4985729 one question: on the charts I understand the reflections as being at the speed of light correct? what would change in the case of FTL...
  35. abrogard

    Does Time Contraction Change Substance?

    As you approach c time slows. Relative to an observer. But it is an actual thing. A material thing can be seen to have not aged as the observer did, right? Well if time slows then an atom cannot vibrate at the same frequency as 'normal'. It must be slowed. An atom vibrating at an...
  36. Einstein Devotee

    Time dilation why or how, Special Relativity causes

    I understand the theory of special relativity and the mathematics which support it. I even understand that the time dilation has been proven. Therefore I am going to ask a question which on first blush may appear that I disagree with it but that is not the case. The question I can not seem to...
  37. W

    Exploring Gravitational Time Dilation & Event Horizons

    I want to ask a question about science/physics. To me and my level of education, this has not been answered, though I am sure there is someone out there that can provide the answer. It regards something I have been pondering due to gravitational time dilation (and space dilation I suppose, if...
  38. N

    Time Dilation and Relative Time

    I was reading in Clifford M.Will's book "Was Einstein right? Putting General Relativity to the Test" that there was an experiment done where in October 1971 an experiment was done with radioactive clocks, and plane trips taken going with the spin of the earth, and against it. He reports: "The...
  39. L

    Why does time appear to slow down on a moving spaceship?

    Please forgive my ignorance in STO, but I don't understand something about the following thought experiment. Spaceship flies from Earth with large speed. We observe the clock inside the spaceship from Earth with strong telescope. We see the clock showing 12:00. When we see on the clock 12:05 (in...
  40. Palpatine

    Help Applying SR to Calculate Time Dilation

    I made this pic to illustrate my problem. A spaceship (labeled B) departs from a space station (labeled A) at 80% the speed of light (0.8c). A applies the time dilation principle and calculates that B's clocks are running slower than his. Some time later a smaller craft (labeled C) detaches...
  41. M

    Time Difference between two inertial frames of reference

    Homework Statement Let S and S' be two inertial frames of reference where S' is moving at a velocity of 0.6c relative to S. When x = x' = 0, t = t' = 0, where t and t' are time of the clocks on S and S' respectively and x and x' are the x-coordinates of the S and S' frames respectively. An...
  42. C

    Lorentz Transformation - Clock

    Homework Statement Use the Lorentz Transformation equations to derive the formula relating the time period of a moving clock to that of a stationary clock Homework Equations X'=y(X-vt) Y'=Y Z'=Z t'=y(t-vx/c^2) The Attempt at a Solution t'=1/sqrt(1-(v/c)^2) . (t-vx/c^2)
  43. H

    Time Dilation at Near Light Speed: Answers to a Thought Exercise

    I'm fairly new to the concepts provided by special and general relativity, and was wondering if someone could provide an answer to a thought exercise I came across regarding time dilation on an object going near light speed. Say a spaceship were connected by a live video feed to a monitor on...
  44. CaraKboom

    Metric Tensor: What is it and how does it relate to Riemannian geometry?

    I've been trying to get my head around time dilation in order to understand the relationship between space and time. I do not have a maths brain, I tend to understand things better as narrative concepts. I've read a lot of introductory material, but I'm having trouble making the link between...
  45. A

    Time Dilation: Photon Reflecting Surface Experiment

    I don't understand the thought experiment where a photon hitting a reflecting surface and traveling back to the observer is viewed from two frames of reference and the concept of time dilation is suggested arguing that the distances traveled by the photon are not the same in both the frames even...
  46. S

    Does Gravity Affect Time Dilation on a Flat, Non-Rotating Earth?

    On a science test that I took the other day, one of the questions inspired me to ask a question of my own. The original question was a multiple choice question that went something like this: if someone shoots a gun horizontally and simultaneously drops another bullet, which one would hit the...
  47. Ganesh Ujwal

    Why isn't length contraction permanent even though time dilation is?

    Why isn't length contraction permanent even though time dilation is? It's my understanding that when something is going near the speed of light in reference to an observer, time dilation occurs and time goes slower for that fast-moving object. However, when that object goes back to "rest", it...
  48. M

    Special Relativity and time dilation

    Homework Statement Two spaceships are traveling with a relative velocity of 1.2x10^8 m/s, both carrying clocks. According to the captain of each ship, the other captains clock ticks more slowly than his own. By what factor do the clocks disagree? Homework Equations 1/(1-(v^2/c^2))^1/2The...
  49. D

    Time dilation as seen by different observers

    Let's say the gravity around a planet of mass M is accurately modeled by the Schwarzschild metric. Then an observer (A) at infinity sees a stationary clock (B) at distance R from the center of the planet being gravitationally time dilated by the factor ##\sqrt{1-\frac{2GM}{Rc^2}}##, i.e. if B...
  50. M

    Geometry of Time Dilation

    I was recently exploring time dilation from Gravity and from velocity and I came up with an interesting derivation that I have not seen before. I was wondering if there is a paper published showing these relationships like this before and where I could find it? First you start with the...
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