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. P

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

    Homework Statement P.S.: I'm not sure if it is allowed to ask multi-part questions. Two equally old sisters Alice and Barbara leave Earth simultaneously in opposite directions. The following velocities and distances have been measured in the Earth system. Alice travels with a speed of ##v_A =...
  2. jha192001

    I Time Dilation: A & B's Age Difference

    This is a gendenke experiment. You(A) and your friend (B) are on earth. Now your friend sits on a spaceship that can fly at speed of 0.1c. He flies for 5 year straight ahead(away from earth) and then returns back slowly. The answer that i get is B would have aged. Assuming this answer is right...
  3. 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?
  4. Jazzyrohan

    I Time Dilation Explained: Feynman Lectures 15-4

    Feynman Lectures 15-4 Transformation of time first para http://www.feynmanlectures.caltech.edu/I_15.html How is it possible that the moving clock slows down and also shows more time elapsed to the man outside?
  5. 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?
  6. N

    I What I understand about Time Dilation

    As I understand it, time dilation can occur under gravity or acceleration, which can be referred to as Gravity Time Dilation and can also appear to be happening when two things are in different frames of reference, which can be referred to as Velocity Time Dilation. With Gravity Time Dilation...
  7. B

    I Differential equation from derivative of time dilation

    Hi all! I was messing around with the equation for time dilation. What I wanted to do was see how the time of a moving observer ##t'## changed with respect to the time of a stationary observer ##t##. So I differentiated the equation for time dilation ##t'## with respect to ##t##: $$\frac {dt'}...
  8. F

    I Can Black Holes Transport Mass Back in Time?

    According to Einstien's theory of evolution, the closer to the speed of light that an object travels, the slower it appears to move to an outside observer. (see https://www.thenakedscientists.com/forum/index.php?topic=40951.0) To take this to the next step once an object crosses the event...
  9. P

    I Gravitational time dilation - acceleration vs potential

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  10. S

    I C Speed, Gravitational Time Dilation & 4-Velocity

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  11. S

    I Time Dilation: Does Gravitational Field Strength Matter?

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  12. M

    I SR Time Dilation in Rigid Structure Clocks

    Special relativity says that all clocks will show same time dilation, irrespective of clock mechanism. But Time period of a clock is a formula that must continue to hold even if time dilates. Let us look at a tuning fork clock. Here time period depends on the dimensions of the vibrating...
  13. U

    I How does gravitational time dilation work?

    I understand time dilation due to speed, but am confused on why time dilates depending on the distance from a mass. Help?
  14. S

    A General relativity: time dilation and speed of light

    Hello everyone, I'll go straight to the question. The gravitational time dilation is equal to tearth = tspace*sqrt(1 - rs/r), with rs = 2GM/c2. However, the formula for speed of light in gravitational field is equal to v = c(1 - rs/r). My intuition tells me that these two formulas must be the...
  15. G

    Time Dilation for Moving Rectangle with Clocks at its Corner

    Homework Statement A rectangular structure carries clocks at its four corners. The clocks are synchronized in the structure’s rest frame, in which it has length L =4ft and width W = 3ft. In our laboratory frame the rectangle is moving in the positive x direction at speed v = 0.8c. As the clock...
  16. C

    Does Time Dilation Affect Synchronized Clocks in Different Frames?

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

    Frames of Reference and Time Dilation

    Homework Statement Imagine that you are flying on an airliner on a long flight to Europe, at a constant speed of 300 m/s. a) You throw a ball towards the back of the plane at 20 m/s. You then shine a beam of light towards the back of the plane. How will these two things—the ball and the...
  18. wolram

    B Lack of time dilation in type 1a supernova

    Here is one for every one to pull apart, it goes beyond every thing I have learnt. arXiv:1804.10274 [pdf, other] Lack of time dilation in type Ia supernovae and Gamma-Ray Bursts David F. Crawford Comments: 4 pages, 2 figures and 1 table Subjects: High Energy Astrophysical Phenomena...
  19. aatari

    Time Dilation - Darth Vader's age

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  20. Craftek_Ana

    B Traveling to Mars and time dilation

    If/when we go to Mars how will we deal with time dilation due to the gravitational differences between the two planets?
  21. M

    B Time Dilation: "Did I Use Formula Correctly?

    Hi, We are not learning this in class, but I am giving a presentation on special relativity and as part of my presentation I would like to show that time is not absolute and that if a ship moves away from the Earth for a time t at a speed v then if like 8 years pass on board the ship a greater...
  22. P

    I Time dilation vs the Equivalence principle

    Some time ago there was a similar thread https://www.physicsforums.com/threads/clock-hypothesis-gravity-time-dilation-and-equivalence-principle.929838/ but what I want to discuss is similar but not the same and I would like to specify my question in such way, that it hopefully won't go sideways...
  23. lookez

    Thermal dilation formula discrepancy?

    Considering the linear thermal dilation formula ΔL=Li*a*ΔT (length change equals initial length times thermal dilation coefficient times temperature change), I was wondering why does it not work backwards? am I using it wrong or is there something missing? For instance if we assume a=5*10^-5 ...
  24. Physics345

    Frame of reference/ time dilation

    Homework Statement Imagine that you are flying on an airliner on a long flight to Europe, at a constant speed of 300 m/s. a) You throw a ball towards the back of the plane at 20 m/s. You then shine a beam of light towards the back of the plane. How will these two things-the ball and the...
  25. Physics345

    Time Dilation & 2 Atomic Clocks (one in orbit)

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

    B Relative speed and time dilation

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  27. Y

    I Interstellar Travel Without Propulsion or Time Dilation

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  28. A

    How Does Relativity Affect the Measured Distance Between Cities at High Speeds?

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  29. J

    B Speed of Light & Time Dilation: Travel Distance in 1 Sec?

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  30. DC0

    I How much time dilation is there within a contracting remnant

    Relative to a remote point, when using the standard GR method, how does the rate of time passage (1 / gravitational time dilation) typically vary with radius within a contracting 5 solar mass supernova remnant, when its’ outer radius crosses a value of about 1.6 times the Schwarzschild radius?
  31. M

    I Understanding Time Dilation and Velocity: Debunking Common Misconceptions

    Hello. I have a question. If I am moving with velocity v for an observer O. If I experience and kind if time dilation and my time slows down with respect to observer O's time. But if my time slows down. For O I will be moving slowly in time. If time dilation is large enough. I will almost freeze...
  32. G

    B Why do clocks experience time dilation in special and general relativity?

    I understand time dilation in both special and general relativity in terms of motion, ie. an object in a gravitational field will move slower than an object outside the field, as the spacetime causes the object in the field to take a longer path to the same destination. Same goes for two objects...
  33. K

    Length contraction and time dilation in relativity

    Homework Statement A graduate student discovers that an elementary particle produced in his experiment travels 0.250 mm through the lab at a speed of 0.950c before it decays (becomes another particle). What is the lifetime of the particle measured in its rest frame (proper lifetime). A) 8.77 x...
  34. M

    B Time Dilation & Length Contraction: Does Relativity Work for Mediums?

    Hello I am new here and I am just Junior college student. So please use simpler terms. I need to know that does relativity work for mediums like air and water. I mean the equations of time dilation and length contraction, do they work for other mediums. If so shall I take C as the speed of light...
  35. R

    B Time dilation and 2 identical clocks

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  36. erik giles

    Light-clock and time dilation [was: Hydrogen atom expressed mathematically]

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  37. Junkwargo

    I Time Dilation: Get Answers to Your Questions

    Hi, I've always had a doubt concerning time dilation, and today the curiosity got the best and I decided to ask people that know their stuff, you people. Maybe the question has been asked before, but I did a quick search and couldn't find it, sorry if that's the case. Well, here it goes. As I...
  38. S

    I Time Dilation and photodetectors

    In the image below, we will be accelerating the entire apparatus. It won't ever reach a frame of inertia. Would someone in a different frame of reference be able to detect this acceleration from the output of the photo-detector? As time slows and the distance the laser travels contracts; would...
  39. E

    B Is Time Dilation Explained by Special Relativity, General Relativity, or Both?

    Is time dilation defined by Special Relativity, General Relativity or both? The topic of time dilation seems to come up often. So I thought I would pose a question, and give my summary and conclusions. I've recently been struggling to understand time dilation. While researching this topic l...
  40. E

    I Time dilation again, Einstein or Resnick?

    I continue to see references to time dilation that I don’t understand. Maybe the bluntest one is in a textbook by Resnick. Introduction to Special Relativity, p. 93: “Indeed we find that the phenomena are reciprocal. That is, just as A’s clock seems to B to run slow, so does B’s clock seem to...
  41. ISamson

    B Can Time Dilation Affect the Mechanical Functioning of a Clock in Orbit?

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  42. D

    Time Dilation and Length Contraction Problem

    Homework Statement Anna and Bob are both born just as Anna's spaceship passes Earth at 0.9c. According to Bob on Earth, Planet Z is a fixed 30 ly away. As Anna passes Planet Z on her continuing outward journey, what will be (a) Bob's age according to Bob, (b) Bob's age according to Anna, (c)...
  43. F

    I Demonstration of time dilation

    I try to find the formula of dilation of time between a reference frame (R') moving at a speed v and a fixed observer in (R). For this, I take the example that we often find as a demo : that of a train in which a light beam is emitted vertically (in the train): this vertical trajectory in the...
  44. B

    I Clock hypothesis, gravity time dilation and Equivalence Principle

    1. The Clock Hypothesis states that the rate of a clock does not depend on its acceleration but only on its instantaneous velocity. This has been experimentally verified at very high accelerations. 2. A clock in a gravitational field experiences time dilation and runs slower that one not in a...
  45. S

    Mapping Circle to Ellipse with Dilation?

    Homework Statement The problem comes from S. Lang's "Basic mathematics", chapter 7, §1: "Consider the following generalization of a dilation. Let ##a > 0, b > 0##. To each point ##(x, y)## of the plane, associate the point ##(ax, by)##. Thus we stretch the x-coordinate by ##a## and the...
  46. C

    B The "why" behind time dilation

    Feel free to correct anything I state here. I'm trying my best to understand some rather complex (for me) ideas about time dilation. So if I understand correctly, increasing velocity compresses time, causing you to exist more slowly relative to anyone not moving at that velocity. Similarly, the...
  47. H

    I Gravitational time dilation in Weinberg's "Cosmology"

    I have a question about the gravitational time dilation explained in Appendix B of the book "Cosmology" written by S. Weinberg. Why can the author say "In the negative gravitational potential at the surface of a star clocks therefore tick more slowly than in interstellar space, or in the much...
  48. E

    I Mechanical clocks and time dilation

    Does anyone know if any mechanical clocks have ever been accurate enough to show time dilation? (That would be a clock with a spring-mass harmonic oscillator.) Is there any reason to suspect they might not show the same thing as the atomic clocks? (Pendulum clocks would not, for example. They...
  49. A

    Time Dilation, calculate the age of the returning astronaut

    Homework Statement "In 2010, a 20-year-old astronaut leaves her twin on Earth and goes on a rocket to explore the galaxy. The rocket moves at 2.7 x 10^8 m/s during the voyage. It returns to Earth in the year 2040. Using relativity, calculate the age of the returning astronaut." Homework...
  50. Crowxe

    I Time dilation (speed Vs. acceleration)

    There's a common example to explain time dilation that states ... "if you traveled at a speed close to the speed of light and came back in a round trip of 1 hour , you may find that on the departure frame of reference 2 hours had passed" but that 2 hours trip can't be done without accelerating...
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