Dilation Definition and 1000 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. GeorgeDishman

    Gravitational time dilation for a spherical body of finite radius

    I am considering the gravitational time dilation at the centre of a spherical, non-rotating body (such as the Earth). The usual formula for gravitational time dilation is √(1-r_s/r) where r_s is the Schwarzschild Radius and r is the radius of the clock compared to one at infinity, however, this...
  2. H

    Understanding the Twin Paradox in Time Dilation

    Hello! I am currently learning the theory of relativity, but have a hard time understanding the time dilation concept. In my example down here, the subscript “A” will be used to denote “in the frame of reference of observer A”; the subscript “B” will be used to denote “in the frame of...
  3. S

    Time dilation to go a specific distance

    Traveling on a spaceship to Alpha Centauri A, 4.37 light years away, at a velocity of 0.92 c, if you just calculate the time by dividing the distance by the velocity: t = \frac{d}{v} = 1.496 x 10^8 sec = 4.74 years Is this the time from the Earth reference frame? Then the time on the spaceship...
  4. N

    Time Dilation Effects of Hypothetical Zero Gravity Pocket

    If you could create a small space on Earth in which a person could fit that was totally unaffected by gravity, or that was sheltered from the gravitational affects of external sources of gravity, what sort of affect on time dilation would be observed? Both for the person in the pocket, and for...
  5. S

    Time dilation and uniform circular motion

    Hi, I've taken a course in SR and studied GR on my own, but I do not know how to solve problems of this type. This is just purely for fun, not homework related at all. A particle of mass m is moving on a circle of radius R at constant linear velocity v = .8c. If the particle makes N...
  6. B

    What is the use of time dilation.

    I mean the application,such as because of the time dilation, humans can observe some particles which don't have long lifetime,and know it
  7. S

    Lorentz Transformation and Time Dilation

    I've managed to confuse myself and don't understand the difference between the formula for Lorentz time transformation (t'=γ(t-vx/c^2) and the time dilation equation t'=γ(t_proper) As I understand, proper time is difference between two events that happen in same place in a given reference...
  8. Y

    Combining gravitational time dilation components.

    Consider a sphere with outer radius r2 and a centred inner cavity of radius r1, forming a constant density shell with density p. Let's say the time dilation on a clock on the inner surface of the shell is ta. Now the shell with filled with a material of the same constant density as the shell...
  9. S

    Correct definition of time dilation

    Can someone give me the correct definition of time dilation(or explain it in such a way that it can be used to tackle any problem)?? What i believe now is "a moving clock ticks more slowly than a clock at rest"..but according to me this is inadequate because there can be two situations...
  10. P

    Does Gravity Affect How Long You Live?

    Here is another question As far as I know, gravity slows time...So it would be true that a person who lives in for example the moon would live less than a person who lives on earth? Or a person who lives on 25th floor lives longer than a person who lives in basement? Of course the difference...
  11. B

    Infinite Time Dilation at the Surface of a Black Hole?

    I've never fully understood how anything can actually fall into a black hole without the black hole evaporating first. Since time dilates exponentially as I fall into a black hole, a point will come where a few seconds for me will be millions of years in the outside world...trillions in fact...
  12. C

    When to use lorentz transformations vs time dilation?

    I don't understand when I should use the Lorentz transformation versus time dilation or length contraction. I found this: http://www.phas.ubc.ca/~mav/p200/lttips.html but it's still unclear to me... "Length contraction applies when you are talking about a distance that is independent...
  13. D

    Special relativity and time dilation

    I was just looking for a basic explanation of special relativity in relation to an object with mass accelerating towards the speed of light. And with reference too time dilation can v and c be referred too as a percentage or decimal depending on the units in the equation used?? Many Thanks
  14. C

    Why is this incorrect (special relativity time dilation)

    Homework Statement Anna is on a railroad flatcar moving at 0.6c relative to Bob. (Their clocks read zero as Anna's center of mass passes Bob's) Anna's arm is outstretched in the direction the flatcar moves, and in her hand a flashbulb. When the flashbulb goes off, the reading on Anna's clock...
  15. I

    Does Time Dilation Affect Daily Airline Travel?

    Hello I have some doubts about this problem which I have attached. If we assume that both the clocks are started at the time the airliner goes for a trip, then for an observer on the airliner, when the airliner comes back to the New York, the time interval would be a proper time interval...
  16. F

    Need help with time dilation and length contraction.

    Can anyone help me with this thought experiment. I have a spaceship moving at very close to the speed of light. Inside are the captain and two crew members. The captain is positioned at the front of the spaceship with a clock and a light. One crew member is positioned at the back of the...
  17. R

    Derivation problems for dilation

    Homework Statement Show that, if there are no body forces, the dilation e ( e=e_{xx} + e_{yy} + e_{zz} = div \;\vec{u}) must satisfy the condition \nabla^2 e = 0 Homework Equations (1) (\lambda + \mu)\frac{\partial e}{\partial x} + \mu \nabla^2U_x = 0 (2) (\lambda + \mu)\frac{\partial...
  18. S

    Time dilation and length contraction

    can both time dilation and length contraction occur for the same observer? i don't think it is possible since then c=reduced length/increased time which is impossible(since c is constant)... Am i wrong?
  19. F

    Time Dilation of Particles A & B in Gravitational Field

    Hi, may I ask you about a help (or where to find proper study materials)? I have two particles - A and B. A is moving at constant velocity in a gravitational field with constant acceleration (due to gravity). B is moving on spiral trajectory at accelerated velocity in a gravitational...
  20. DHF

    Traveling at the speed of light and time dilation

    hey guys, I need some tech support for a spaceship in a story that is currently in the works :) Assuming the characters could get their ship up to the speed up light in real space (no hyper drive or warp drives) What would the effects of time dilation be on the crew? Time slows down as you...
  21. rogerk8

    Gravitational time dilation reason

    Hi! I am really bad at physics so bear with me... I saw some very interesting 3 hour physics-marathon on TV the other day. I have never gotten an actual clue on how things work relativisticly even though I've read a book by Brian Greene some years ago. Since then I have tried to...
  22. P

    Question about the x term in time dilation

    When I first learned time dilation I was given this equation proven using the light clock example. t = γt' However, when I looked into the topic in more detail, I was given this equation. t = γ(t' + xv/c2) If x represents the distance between 2 frames, then does x have to change...
  23. J

    Is Cosmological Time Dilation real?

    The cosmological redshift can be understood in terms of time dilation. In an expanding Universe light travels on a null-geodesic (ds=0) so that: dr = \frac{c\ dt}{a(t)}, where dr is an element of co-moving distance along its path, dt is an element of time and a(t) is the Universal scaling...
  24. S

    Time dilation effects on a human being

    Hello everyone, long time lurker first time poster here. I've been wondering for a while about this: Let's suppose a newborn baby is placed in a spaceship capable of traveling at 0.95c. The baby travels from Earth to a (theoretical) planet 95 light-years away which is at rest relative to...
  25. D

    Need help in a time dilation question (high school)

    So basically I am in high school and have done my major exam for the end of the year. It was a good test except for one question that i got totally stumped on. The question said that a planet was 6.7 light years away from earth. A spacecraft has a maximum speed of 0.9c, how long would a clock on...
  26. A

    Seeking clarification of time dilation

    "Since we are always at rest with respect to ourselves, ignoring the effects of acceleration, our lifetime, as measured by us, will always appear shorter than it appears to others. To others our clocks will seem to run slow. But we will die, alas, on the cue of the internal timer that travels...
  27. 7

    Homework - time dilation problem (Lorenz factor is unknown)

    Homework Statement Alpha Centauri is ##4.4## light years away from Earth. What speed ##u## would a spaceship headed towards Alpha centauri had to have in order to last ##t' = 10## years for a passanger onboard? Homework Equations I know equations for time dilation, length contraction...
  28. S

    More on gravitational time dilation and escape velocity.

    First, thanks for all the replies to the first post. I was able to predict this result (an engineer did the proof) using an analogy for gravitation I worked out to replace the standard marble rolling on a rubber sheet analogy used to show the effect of curved space time, which is useless on a...
  29. S

    Gravitational time dilation and escape velocity

    The time dilation caused by gravity on the surface of a planet is equal to the time dilation for an object moving at the planet's escape velocity in space. This can be proved using the Schwarzschild metric. GR doesn't explain why this is true. It seems to be an odd coincidence.
  30. T

    Time dilation in gravitational field

    A friend of mine posed the following conundrum: If you have 2 identical clocks one at the top and one at the bottom of a tower (on the earth), then for an observer at the top, the clock at the bottom appears to go more slowly than the clock next to him. This one can deduce from the redshift of...
  31. C

    Time dilation, reference frames

    Hi, Basic question. I'm confused by a time dilation example (37.3 in Young and Freedman 11th ed.). Mavis is moving at .600c relative to earth-bound Stanley, and at the instant she passes, both start timers. Part b asks "At the instant when Mavis reads .400 s on her timer, what does Stanley...
  32. D

    Time Dilation Explained: T=T(P)*γ Example

    Hello, can someone give me an explanation of the time dilation equation t=t(p)*γ? I know it's used to measure something about a difference in sense of time in different reference frames, but I don't know how to put it into context. Can someone give me an example where you would use the time...
  33. D

    Time Dilation Problem: Help Solve Light Beam Issue

    Hello all, I've been having trouble with this problem; can someone please help? The problem is: If a light beam is shot parallel to me, and I'm running at .7c in the same direction of the light, how much time passes in the light's reference frame (point of view) if I experienced (Earth's...
  34. D

    Time Dilation Equation: Clarifying Variables

    Hello, I've recently come across the equation for time dilation, which is t=t(p)*γ, which is t=t(p)*(1/√(v^2/c^2)). Can someone please clarify what each of these variables mean?
  35. DiracPool

    Can we really ever accurately test SR time dilation?

    The two most famous "tests" for the accuracy of time dilation in SR are 1) the plane that flew around the globe with the atomic clock, and 2) the muon experiments on the mountain. I'm assuming, of course, that all the experimental controls are correct and so are the results. My question is...
  36. Z

    Time Dilation Video Feed Experiment

    Time dilation As I've understood; two parties can experience time, or timespace, differently depending on each parties' • velocity • gravity A debate led to this question: ship A and ship B install livecams, each viewing both ships' livefeed on 2 screens*. Ship B launches away from...
  37. M

    Time Dilation Thought Experiment

    A ninja the size of solar system has a sword that could slice through something the size of the sun. For the purpose of the thought experiment let's imagine a black hole and the time dilation effects around it. Now take away the black hole but keep the time dilation. What would happen to the...
  38. 4

    Can you modify this quote regarding time dilation?

    The total speed of an object through the dimension of space and the dimension of time equals the speed of light. An object moving through space must subtract from its movement through time for the sum to remain at lightspeed. So an object at the speed of light has all its movement through space...
  39. ash64449

    Is this simple derivation of length contraction and time dilation corr

    well,i found this article and i find it simple to understand. But is this article totally correct? Here is the link:http://m.sparknotes.com/physics/specialrelativity/kinematics/section2.rhtml
  40. L

    Time Dilation: Exploring the Mechanism and Alternatives

    what is the exact mechanism by which time dilates for a fast moving object. Can the time dilation be explained by any other theory other than relativity.
  41. D

    Could Time Dilation be Caused by Increased Clock Energy?

    Im definitely not an expert in this field but i have a question. From what I've picked up time dilation can be observed when a clock has a velocity or moves away from the centre of Earth and it slows/speeds up. In both these cases the clock has more energy, be it potential or kinetic. Could this...
  42. W

    Speed of Light relation with time dilation

    Hello Want to know if constant speed of light is a result cause by time dilation? When your time slow down as you approach speed of light you take a longer time to measure light speed in your spaceship, there for you think speed of light relative to your current speed is still c? When one...
  43. C

    Understanding Time Dilation: A Confusing Experiment Explained

    I've seen an experiment with a light clock that explains time dilation. A photon is fired and gets reflected off of 2 parallel mirrors. It keeps bouncing back and forth like that, with each bounce qualifying as one tick of the clock. And it looks like that from a stationary reference frame. Now...
  44. A

    Time Dilation & Space Contraction: I'm Confused

    I'm confused. If t=γ*t0 and L0=γ*t how does the equation x=v*t hold for x0=v*t0, for constant velocity (Let t0 be the time in the stationary reference frame and t the moving frame, the same for length)? Then v would be equal to γ^2*v... Perhaps I'm missing something here.
  45. S

    Do you agree with my explanation of time dilation

    The increased contraction and shortening of space is causing dilation in the passing of time. In other words, increased relative velocity spreads two points in time further from each other. Please tell me I understand this correctly! I hope the Great Peter Donis will weigh in.
  46. A

    Time dilation and length contraction

    I've recently been thinking more about special relativity, and while I understand the Lorentz factor and how to apply it to find correct solutions, I'm still stuck on the link between the effects of length contraction and time dilation, are they permutation of the same thing from different...
  47. A

    Time dilation and length contraction

    I've recently been thinking more about special relativity, and while I understand the Lorentz factor and how to apply it to find correct solutions, I'm still stuck on the link between the effects of length contraction and time dilation, are they permutation of the same thing from different...
  48. A

    Hypothetical thought experiment about time dilation

    Let's say that you leave Earth at 75% the speed of light (c). You travel out and back for a minute. And when you come back an hour has passed on Earth. (I understand this is not accurate; I'm just using it for the sake of this hypothetical) You leave again at 99% of c, again for a minute. When...
  49. A

    B Gravitational red shift and gravitational time dilation

    How does the gravitational red shift causes time dilation?
  50. ash64449

    Still confusion in relativity of simultaneity and time dilation .

    Still confusion in relativity of simultaneity and time dilation... Hello friend, Still Something in my mind is saying that Relativity of simultaneity is the reason for time dilation even though i had some corrections in my understanding by posting various threads. Well,let me use Einstein's...
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