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. S

    I Calculating Time Dilation & Galaxy Rotation Curve

    Hello, What I understood from multiple answers on different threads is that the effect of the time dilation is too small to explain the galaxy rotation curve. I was advised to do some calculations in order to see it myself. And this is what I would like to do but I need some help. - What is...
  2. K

    Ideas for novel I'm writing I would love some insight on a concept

    Summary:: Ideas for a novel I want to begin writing. Brainstorming ideas and need help with a certain concept. Any help is appreciated! Hello to you all, this is my first post, and I Google searched this astrophysics forum because I thought it might be a good place to begin asking for advice...
  3. Atstill77

    B Why do you need a light clock?

    what is wrong with the thought experiment below?! If I consider a light beam going straight towards an observer in motion it makes it look the moving clock ticks faster, but if you use a light clock it makes it look like the clock turns slower. What am I missing here? “Two observers convene in...
  4. Lutz-F

    B What Links High Velocities, Strong Gravitational Fields, and Time Dilation?

    The faster the relative speed or the more intense the gravitational field, the slower time passes. Does it make sense to ask what both have in common that affects time? Or does the question possibly only make sense in the context of certain theories, for example the LQG, where space and time...
  5. O

    B Contradictory time dilation equations

    It is possible to derive 2 contradictory time dilation equations. The first paragraph below describes the situation with Sally aiming a flashlight straight up and down so that Sally sees the light moving straight up and down and John is outside the spaceship and sees the light forming a...
  6. jaketodd

    B E & B Field Oscillation with Time Dilation: Explained

    If time for something approaching the speed of light will slow down and approach zero, then how is it that light itself can exhibit changes - the oscillation of the E and B fields? Is it because those fields are perpendicular to the direction of light travel? If so, then something other than...
  7. richengle

    I Does time dilation cause different aging rates for people?

    if you could leave the planet, and wait a year in space... would you age much much faster than a person on Earth because the Earth was moving relative to you and you are out of Earth's gravity field [like a higher up clock]?
  8. U

    I Length Contraction & Time Dilation: Proving It

    I have been able to prove to myself that, based on Einstein's two postulates and the the Pythagorean theorem, that time dilates. From here how do I prove that length contracts? (All of this observing a frame that is moving relative to the proper frame at uniform velocity.)
  9. T

    B On time dilation and length contraction

    Hello there.About time dilation, could we provide a derivative of time in relation to one of the coordinates of the manifold we have taking time as a function and get something as a result?Or its integral?And about time dilation we have the formula that gives it between two clocks and an...
  10. Drizy

    B Time Dilation: Orbit Earth at Light Speed, What Happens?

    I’m having quite a bit of trouble understanding time dilation. What will happen if you orbit the Earth close to the speed of light, 1 h passes for you and due to time dilation 2 h on earth. So what will happen when you look at Earth in that hour. Since time passes 2 times faster there will it...
  11. Drizy

    B Faster than speed of light due to time dilation?

    This probably has been asked before but i had a thought about the speed of light and time dilation. First off all i know the speed of light is constant and that it is the max speed anything can be but hear me out. So let's say a jet are traveling from point a to b in space with let's say 0,8c...
  12. X

    B Time Dilation & Length Contraction: Physics Explained

    So basically i know almost nothing about physics but i have this one curiosity and i hope you can help me ahah. For what i understand if you could move at the speed of light time would stop for you and you would see the whole universe age in a blink of an eye. But what if you could stand...
  13. Hiero

    I Twin Paradox Time Dilation in Positively Curved Universe

    I’m sure the resolution is something to the effect of “we can only apply special relativity in flat spacetime” but I’m hoping someone can explain in more detail. Disclaimer: I don’t know general relativity. So in a positively curved universe, if you keep traveling (let us neglect expansion)...
  14. Lars1408

    B Time Dilation: Direction of Motion's Effect

    Earth moves through space in a certain direction at a certain speed. Moving faster slows down your clock while moving slower increases your clock. Does this mean that the direction your moving in has an effect on time dilation? In other words, if you move along with the earth’s initial speed...
  15. V

    I A question about time dilation

    OK this is a quote from the physics forum site - it is not mine. So the above quote says that there are two effects which alters the clock ticks, the GR effect and the SR effect for clocks aboard satellites. We all know that satellite are in free fall and for free fall there must be a steady...
  16. George Plousos

    I A version of the twin paradox without accelerations

    Bob is standing on Earth and Alice is on a distant planet at a constant distance from Earth. Their watches are already synchronized in the following sense: Suppose Alice's planet is a light-year away from Earth. Bob emits a light signal to Alice at time t = 0 according to Bob's watch. When Alice...
  17. Stephen Bulking

    Length contraction and Time dilation for LIGHT?

    Radio wave travels at the speed of light 3x10^8 (m/s) Converting the distance to meter: 1.3 x 3.1x 10^16 = 4.03x10^16m The time it takes in our Earth frame of reference is: 4.03x10^16m/3x10^8 (m/s) = 4.26 years The answer is B But wouldn't the time in light's frame of reference be 0 and it's...
  18. W

    What is the algebra concept used to derive time dilation formula?

    Hi this is my first post the forum, nice to meet you all. I am trying to derive the time dilation formula following the image attached. However I am unsure of the algebra being used toget from the 2nd line of working to the 3rd line. Can someone please tell me what the name of the algebra...
  19. D

    B Time dilation and the reference frame of the vacuum

    The point of the twin paradox in special relativity is that the traveling twin experiences a real, frame-invariant effect in which the time evolution of all moving matter is slowed down. If you read a hundred articles and textbooks on SR, you'll see a hundred variations on the message that the...
  20. Sabertooth

    Transforming Y-axis table values into a separate formula?

    Hey everyone, I have generated a nice little velocity vs time graph that I would love if somebody could help me put to use. I have marked data points on the x-axis for the Y-value for every second on the function. Just to be clear: X-axis = time in seconds & Y-axis = velocity in meters/second...
  21. AndrewDes

    B Time Dilation b/w Galaxies: Dark Matter Impact?

    If time slows down near a black hole then doesn't it stand to reason that time is slower in our galaxy than inbetween galaxies. If that's the case, wouldn't our measurements of distant galaxies be over estimated do to time being faster intergalacticly. Would this time dilation help explain part...
  22. Mattv

    B Time Dilation & Relativity: Explained for Beginners

    Good morning I'm a total beginner in physics, but I recently started to read books and watch videos about cool physics stuff, like relativity. I heard that the closer to the speed of light you travel, the "slower" time passes for you. I'm talking about the fact that clocks in GPS satellites...
  23. YouAreAwesome

    B Does time dilation work in 1d space?

    Imagine this question in 2 dimensions, time (t) and distance (x), that is (t,x). Alice (A) is at the origin, x=0. Bob (B) begins at x=c. Thus we have A(0,0) and B(0,c). Both Alice and Bob send a light signal towards the other but let's say the signal changes colour every second by the colours of...
  24. P J Strydom

    B Length contraction and Time dilation calculation

    I was absent for a while due to personal constraints but I did keep myself busy with the Time dilation equation some member sent me a while back. I decided to set a time limit for myself to learn and understand time Dilation and length contraction, which must be before December 2020, or I will...
  25. ersa17

    I Why does time dilation only affect one of the twins?

    I am more confused by the theory of relativity as I start thinking about it. I have a question and it might sound silly but please, correct me if I am wrong. Suppose, A and B are twins where A is at the Earth, and B is moving on a spacecraft at a speed near to the speed of light. In this...
  26. D

    Effect of time dilation on temperature

    Thank you in advance for your replies. While reading about special relativity I started thinking about how time dilation might affect temperature. Since temperature is really the jiggling motion of molecules, does time dilation affect temperature by slowing down the jiggling motion? Or...
  27. S

    Lorentz transformation for an approaching observer

    I think this should be t'= Lorentz factor* (1+v/c)t, but that doesn't make sense to me.
  28. J

    I Gravitational time dilation using an accelerating light-clock

    I've been trying to understand gravitational time dilation by considering a light-clock of length ##l## undergoing an equivalent acceleration ##a## from rest along the direction of the bouncing light pulse. I find that the time ##t## that the light pulse takes to travel to the forward receding...
  29. just dave

    B A thought Experiment in Time Dilation

    Ok so here's my idea,it came to me while watching a record album spin on my turntable(I believe it was Dark Side of the Moon). Technically this exp. could be done now but the results would take a while. You take a disc of some super strong material attach it to a ultra high RPM motor and put...
  30. arkantos

    I Solving Confusion About Black Holes, Schwarzschild Radius & Time Dilation

    According to the theory, every mass has a Schwarzschild radius associated. Any object whose radius is smaller than its Schwarzschild radius is called a black hole. So in principle is possible to create mini-black holes, it is just a fact of matter condensed. Those mini black holes have their...
  31. C

    B Exploring the Concept of Time for Photons

    Do photons, I'm not sure how to express this, "experience" time? Since they move at the speed of light does time not exist for them? If time does not exist, how is it possible for anything to happen to them. If interacting with matter requires a change in their condition, how can a change in...
  32. PainterGuy

    B Time dilation, relativistic mass and fuel consumption

    Hi, Could you please help me with the queries below? Question 1: A GPS satellite is moving faster than the earth, for every day on Earth the clock on the satellite shows one day minus 7 microseconds due to time dilation due to special relativity. However, since the Earth's gravitational pull...
  33. penroseandpaper

    Time dilation between two frames

    [Wow - special relativity is amazing but boy is there a lot to get your head around! We're only being introduced to it as a taster of college courses but the few lessons we've had have left me with more questions than answers; most fascinating topic yet, I think!] Unfortunately I've tackled a...
  34. E

    I Time Dilation Probes: Exploring the Possibilities

    Firstly, I am a Mechanical engineer working in the aerospace industry and I know very little compared to the collective community here and my formal education had to do with practical and basic stuff, so apologies if I’m overlooking a basic principle or something. my idea: what if we launched a...
  35. samuel toco

    I Solve E = mc^2 & Time Dilation Equation

    how to equal the equation: E = mc2 and the Time dilation equation
  36. Julius Ceasar

    B Apparent contradiction in time dilation

    This video here <link deleted> 8.50 to 9.50 minutes , shows an apparent contradiction in time dilation, in the "twins paradox" the clock that is accelerated is relative, i.e. from Earth the spaceship moves but from the spaceship the Earth moves. I know time dilation is a real thing used in real...
  37. Haorong Wu

    I Time Dilation: Clock A & B Confusion

    Suppose there are two clocks. Clock B is moving with a speed of ##v## relative to clock A. Then clock A is moving with a speed of ##-v## relative to clock B. Let ##t_0## be the time interval for two events in the framework of clock A, while ##t## be the time interval for the same two events in...
  38. Chris Miller

    B Gravitational Time Dilation in L1 Point: Summed, Canceled or Else?

    In the Lagrangian (L1) point between two hypothetically massive (and close) objects , is gravitational time dilation effect summed or canceled, or something else?
  39. S

    B Shouldn't the time dilation in cosmic voids be immense?

    Shouldn't we question why cosmic voids are expanding but not galaxies?
  40. G

    I Escape Velocity, Gravitational Velocity & Time Dilation

    The is a question about gravitational time dilation and escape velocity. As others have pointed out, you may use escape velocity to calculate gravitational time dilation in a gravitational field. (Interestingly, you can't use gravity to calculate gravitational time dilation, which makes...
  41. M

    Special Relativity question using Lorentz Transformation time dilation

    with distance between planets as 4x10^8m measured by you on the ship My attempt: t' = γ(t - ux/c^2) γ = 5/3 u = 0.8c t = 0.9s x = 4x10^8m answer is: -0.278 Therefore not possible My question is what if we traveled rightwards, from p2 to p1, would the answer change? Should my above information...
  42. B

    I Time Dilation, Length Contraction & Massive Bodies

    For instance, if a stream of muons were released from a box near a massive object and traveled on a straight path slowly (at a non-relativistic velocity) away from that object, a faraway observer would notice that the particles would take longer to decay than a muon typically would in empty...
  43. A

    I How time dilation is a permanent change and length contraction not?

    Comparing high precision atomic clocks, one flying in a airplane and one on the ground had demonstrated permanent time dilation presumably due to special relativity (speed) and/or general relativity (gravity) . While similar experiment with a ruler would demonstrate length contraction only...
  44. jk22

    I Time Dilation: Relative to Medium or Vacuum?

    If a medium with speed of light ##c_1## is considered, shall the Lorentz transformation be considered relative to it or to speed of light in the vacuum ? I don't know if we could send particles like muons through water for example, to check this with their life time.
  45. P

    I Time Dilation, Mass-Energy Equivalence: Implications for Time Passage

    I'm an amateur physics enthusiast, and there is a question that's been in the back of my mind for some time that I haven't been able to answer on my own, and haven't gotten a satisfactory answer elsewhere. First, I want to define a couple of terms and make sure my understanding isn't breaking...
  46. J

    B GR & Early Universe: Time Dilation & Light Speed

    If in the early Universe the matter density was density so large causing an intense gravity field, was the time at that epoch running much more slowly compared to the actual time according to the GR? If so then, would any reference frame in the early Universe see the light apparently traveling...
  47. adosar

    B Time Dilation & Relative Motion: Who Measures Proper Time?

    Consider the example of flashing light in spaceship. The observer in the spaceshipe and the observer in the Earth measure different times. Both observers could argue that the clock of the other tick slower(motion is relative). But is anyone right ? I mean the one will measure proper time...
  48. D

    I Calculate Time & Distance Dilations: 50k Years & 1 Day

    I m a noob, I wanted to figure out the time dilation for an observer on Earth who passed 50,000 years, and the Traveler at light speed(99.9%) passed ONE DAY. I mean we pass 50,000 years on Earth and the Traveler spends One day.Problem is I tried many online calculator, but each one is giving me...
  49. D

    I Realistic Time Dilation for Objects > Subatomic Particles

    Time travel, or more precisely time dilation, has been a well known proven result of Relativity. It has been demonstrated most notably in satellites traveling thousands of mph around the world with GPS. You can only go forward with our current understanding of physics. Have there been any...
  50. S

    B Attribution of Reference Frame: A Dilettante's Question

    I can't find an answer on my dilettante question about how we attribute reference frame to complex objects, where different parts move with different velocity or where different parts experience different influence of gravitation. For example, we can take a human's body. If we take the full...
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