What is Dilation: Definition and 1000 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. E

    Need help resolving this paradox with time dilation

    Before I post this, I want to assure everyone that I am not a conspiracy theorist who doubts Einstein or relativity theory in any aspect. I just don't understand special relativity as well as Id like to and I think having this paradox resolved in my mind will help. The paradoxes that I've...
  2. Ryan_m_b

    Exploring Time Dilation: The Case of Alice and Bob

    I understand that the faster one goes the slower time goes but a thought popped into my head recently that I couldn't resolve; Alice and Bob are at rest relative to each other in an otherwise empty universe (i.e no point's of reference). Suddenly Alice observes Bob moving away from her at...
  3. A

    Gravitational Time Dilation - Is my head older than my feet?

    According to general relativity, objects in a strong uniform gravitational field experience time slower that objects in a weak uniform gravitational field. Does this mean that my feet, being closer to the Earth that my head, are younger than my head when I die? If this is correct could someone...
  4. H

    Which Clock Slows Down with Time Dilation?

    If you send an ultra precise clock circling at a huge speed on a train and leave a clock stationary near the rails and then compare them,there would be a small difference in the time they display,right?But if everything is relative,doesn't that mean that from the point of view of the people in...
  5. B

    Question on Time Dilation Experiment

    If time is slowed for an observer circling the Earth and we put an observer on the earth, sun, center of the milky way and finally the center of the universe then would it be correct to say that time would be moving fastest for the observer at the center of the universe? If so is it possible...
  6. J

    Understanding Time Dilation Formula: Exploring the Effects of Speed on Time

    The time dilation formula: \Delta t'=\frac{\Delta t}{\sqrt{1-\frac{v²}{c²}}} says that the closer you come to the speed of light the slower time goes (for the object in movement). That mean if you travel to a distant star in very high speed, there will take shorter time to get there (for the...
  7. Z

    How Does Gravitational Time Dilation Relate to Gravitational Red-Shift?

    Einstein introduced the concept of gravitational time dilation. I get the impression that it was determined to be a consequence of gravitational red-shift. Can anybody tell me the logical reason why gravitational time dilation follows on from gravitational red-shift? Or was the existence of...
  8. S

    Wrong Time Dilation: Why Observers Disagree

    Hello ! Can you tell me what's wrong? I suppose two observers. They measure speed of light. One observer is in rocket of length L. Observer in rocket measured speed C'=\frac{L}{t'} and t' is time from observer's view. Second observer is outside. He measured C=\frac{L+vt}{t} where v is...
  9. D

    Time dilation/ light speed-thought experiments

    There are a few things bothering me about time dilation, its derivation, and special relativity. Einstein started with the assumptions that light travels at a constant speed no matter the observer or their frame of reference. He then details the light box experiment in which two observers are...
  10. R

    A problem with time dilation help?

    A problem with time dilation help!? when we move with light our time is slower and when we move against it then it's slower but what if we move at 99%C in a direction and a light ray is move with us and another light ray moves opposite from our direction simultaneously?
  11. D

    Basic questions on time dilation (probably already answered, sorry)

    New to PF, and while I don't know much about the science behind these things, I do come in peace. I have more a philosophical understanding of special relativity, never having worked out a formula, and can't even understand the language of those physics equations. I do, however, grasp the...
  12. M

    Scenario where time dilation seems to be paradoxal

    Imagine the following scenario: There is a train, that crosses the entire planet, and has the length of the Earth diameter (has no start or no end, it's like a "ring"). This train has in the floor a treadmill that runs in the opposite direction of the train. Also, the treadmill has the length...
  13. G

    Time dilation plus constancy of light implies space is dilated?

    Dear all, I've read the following argumentation for curved spacetime: 1) From the equivalence principle one can derive that time is dilated in gravitational filed.. 2) The velocity of light is constant for all local observers 3) If time dilates, then also space must dilate if one wants the...
  14. B

    Would gravitational time dilation prevent Singularity in a black hole?

    In the current mainstream theory of black holes, there exists a singularity of infinite density. However, it seems to me that matter actually could not compress tightly enough to reach this point. As matter coalesces in a black hole, space-time would increasingly curve. As the density...
  15. A

    Time Dilation and Death: Understanding the Effects of Gravity on Aging

    lets say that there is a triplet at the age of exactly 60 years old.one of them A is in space far away from any gravitational field and not moving , B is on planet earth,and C is near a black hole. C looks at A and see that for every 10 min passes according to his clock(hand and biological) A...
  16. P

    Gravitational time dilation on cylinderical objects

    I am simply looking for the formula to work out the time dilation on cylinders with uniform density. Also, any links to arbitrary precision calculators would be appreciated.
  17. V

    Time dilation and twins paradox

    "The confusion that arises in problems like Example 26.1 lies in the fact that movement is relative: from the point of view of someone in the pendulum’s rest frame, the pendulum is standing still (except, of course, for the swinging motion), whereas to someone in a frame that is moving with...
  18. A

    Why is the dilation factor of a^kx

    ...equal to 1/k? Why isn't it just interpreted as k?
  19. B

    Time Dilation - Is this a paradox?

    [PLAIN]http://www.science27.com/forum/rocketL2.jpg Above the head of observer “A” a mother-ship is moving east 100,000 km/s. and right above the Earth it is launching a small spacecraft moving west with the same speed (100,000 km/s). REFERENCE FRAME A Observer “A” would now (from...
  20. J

    Gravitational time dilation implies energy change?

    According to Einstein's Gravitational Time Dilation, if an oscillating physical system is elevated to a height H above the Earth then it oscillates at a higher frequency than the same system at ground level. According to Planck's relation between energy and frequency this surely means that...
  21. A

    Exploring Time Dilation and Mass

    Hello, I don't know if this is the right place to come for my type of question but its the place that made sense to me so here it goes. I know that time stretches out when traveling near c (I am familiar with Einstein's twin paradox), however I remember somewhere I heard that objects with a...
  22. N

    Wikipedia: using the four-velocity to understand time dilation (?)

    Hello, I was wondering if the following quote by Wikipedia (http://en.wikipedia.org/wiki/Four-velocity section "Interpretation") makes sense: Cause I would think it doesn't make sense: in this reasoning they're acting as if the norm is something like a^2+b^2+c^2+d^2, so that if...
  23. K

    Exploring Time Dilation Symmetry: A Case Study of a Rocket Traveling at 0.8c

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  24. C

    Lenght contraction of a charged wire and time dilation?

    In my class we were doing examples with a current carrying wire and if we moved with a speed v we would see length contraction. And because of this the moving line charge would go up in value and we would see an Electric field. And then we did the same for a solenoid but he said we need to...
  25. B

    Why does time dilation create a velocity barrier but not a density barrier?

    Please explain to me what I'm missing: You can't go faster than the speed of light, because of time dilation. The faster you go, the slower time moves for you as compared to objects at rest, and time would stop for you if you ever went the speed of light. That's what makes C the universal...
  26. V

    Length Contraction and Time Dilation

    Length Contraction and Time Dilation Gamma= 1/sqrt(1-v^2/c^2) = 2 (Assumed) We have L=L’/Gamma…………………………………….1 And dT= dT’ * Gamma ………………………………2 Let primed frame is that of Bob and unprimed that of Dave. Let us define identity as an equation in which values on both...
  27. D

    Ambiguity in time dilation due to relative velocity

    I would like to see some comments on this observation that appears to lead to an ambiguity re: time dilation: The usual definition for time dilation is the expression: t =t'/(1-V^2/c^2)^1/2 where an individual in the unprimed coordinate system "at rest" in empty space, sees a clock in the...
  28. R

    How Much Longer Does an Atomic Clock Run on the Moon Compared to Earth?

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  29. C

    Why is the Speed of Light Constant in Time Dilation?

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  30. A

    Pore dilation with increased pressure

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  31. R

    Time dilation & length contraction

    Hi guys and girls. Need some assistance with these problems, not the hardest examples, but I need some help on the way. Homework Statement 1. An astronaut travels at 0.9c across our galaxy, which is 100 000 light years in diameter. How long time will it take (according to the...
  32. A

    [Special Relativity] - Time Dilation

    Homework Statement If a cosmic ray proton has 15J of energy how long, according to the proton's proper time would it take to travel from the galaxy M31 to our Galaxy, a distance that we mesure as 2.5x106 light-years? Homework Equations K.E = m_{o}c^2 (\gamma -1)The Attempt at a Solution I...
  33. R

    Silly time dilation question

    I was wondering, imagine if I had twin brothers who each set off in their space ships at the same time, at a speed of 0.5c. One traveled 20 light years in a straight line, then turned around and traveled 20 light years back to me, the other traveled along a complete circular path, with a...
  34. J

    Time Dilation Puts Two Observers at different Times?

    Okay. A man in a spaceship travels at \beta=\frac{\sqrt{3}}{2} giving him a Lorentz Factor of \gamma=2 and a time dilation of t'=2t Another man sits "stationary" in space. After traveling for one of the stationary observer's seconds the moving observer passes by the stationary...
  35. Z

    Question about time dilation in the schwarzchild metric?

    My first question is the following. Does the radial component of the schwarzchild metric account for just the radius of the body in study or is it the distance between the body and the observer, where the body is treated as a singularity (Point mass particle)? My second question is about how...
  36. A

    Question regarding light clocks and time dilation.

    Hello. I am trying to gain a more intuitive understanding of relativity, and hopefully someone may be able to help me. Suppose there are two light clocks on two different spaceships - ship A and ship B. If the two ships are moving past one another with a constant velocity, then an observer on...
  37. D

    Time dilation flashlight problem

    I have a copy of "Relativity and Early Quantum Theory" by Robert Resnick. On page 78 there is a problem from chapter 2: A, on earth, signals with a flashlight every six minutes. B is on a space station that is stationary with respect to the earth. C is on a rocket traveling from A to B...
  38. W

    Do I have time dilation right?

    Hello all, First let me say that I have been battling with time dilation for years, all the videos seem to drive me more into confusion and reading does the same. The past few weeks I have been really trying to get a grasp on it better. I understand the concepts, theories, and postulates but...
  39. H

    Mass inflation exactly equals time dilation?

    Two spacecraft in inertial motion have relative velocity .5c. The ships have identical "grandfather" clocks very much like earthly grandfather clocks, except that the force of gravity is replaced by Coulomb repulsion. [The clocks have charged plates on either side of a charged pendulum...
  40. M

    Length Contraction causes Time Dilation?

    I had a big epic discussion on another board after someone stated that "if I were to travel to Betelgeuse at a sufficient velocity I would reduce the distance between myself and Betelgeuse until it is say, 2 light years, which means I would only experience 2 years or so during my journey", this...
  41. F

    Time dilation yes, why no contraction?

    The example I have read to show time dilation is that of a light clock on a train. Two mirrors are one metre apart. Light is beamed from the first mirror to the second. An observer on the train sees that it takes the amount of time for light to travel 1m for the light to reach the second mirror...
  42. S

    Understanding Light Clock & Time Dilation

    Hi guys, I am having trouble getting my head around the light clock scenario which demonstrates time dilation. I can't help but intuitively feel that it seems like a fault of the clock, rather than time dilation. I hope you can understand what I'm getting at. If someone could try to give an...
  43. N

    Time dilation and length contraction

    Can someone please clear this up for me? Lets say the distance of Point A from Earth is 10.4 light years. Some spacecraft is traveling 0.95c. So. The person in the spacecraft will see Earth contract but Earth will see the spacecraft contract in length too. The thing I'm confused on is...
  44. A

    Mass Dilation: Does 0.9c Travel Increase Mass?

    Hey guys, i was just wondering what would happen if a person was on a spacecraft traveling at 0.9c was standing on a set of scales that measured his mass, went past a stationary observer. Would the stationary observer see the reading on the scales increase due to mass dilation? I asked a...
  45. B

    Why do clocks appear to run at different speeds when traveling at high speeds?

    I don't understand this: http://casa.colorado.edu/~ajsh/sr/timevbig_gif.html if the mirror is moving fast enough, why won't the light just miss it? why is the light traveling towards at an angle instead of straight?
  46. G

    Is time dilation relative, or absolute?

    I explain my question through an example. If we brought down a GPS clock, would it show the normal time, because it was accelerated before launch, but it has been slowed down by time dilation? Or we have to accelerate those clocks in order to compensate for the time loss, till the signal from...
  47. A

    Calculating Time Dilation on an Airplane in Special Relativity

    Homework Statement An airplane travels 1250 km/h around the Earth in a circle of radius essentially equal to that of the Earth, returning to the same place. Using special relativity, estimate the difference in time to make the trip as seen by Earth and airplane observers Homework...
  48. F

    A good video explaining time dilation

  49. W

    Time Dilation: Does Length Contraction Apply?

    Suppose I am standing on the Earth surface and observing a rockhet of very high speed then i will see the length the rocket contracted and abserver on the rocket will also see my length contracted(I am not sure about it)in the direction of motion. Is the same case takes place with time...
  50. A

    Need help understanding time dilation

    I keep reading that an observer will find the clock moving relative to him to be slower than his own local clock. But isn't his own local clock measuring proper time, which should be a shorter time period than the moving clock? How can the slower (moving) clock measure a longer time period...
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