# Questions tagged [time-dilation]

This tag is for questions regarding the 'time dilation' which is the lengthening of the time interval between two events for an observer in an inertial frame that is moving with respect to the rest frame of the events (in which the events occur at the same location).

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### Can anyone explain all kinds of motion in the same perspective? [closed]

Imagine an object in space, you hit it with a force equivalent to its mass. The mass first resists due to inertia, but then accelerates with increasing acceleration until reaching a constant speed to ...
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### Gravitational time dilation and power beaming

Consider this thought experiment that kept me awake for far too long last night. Two spacecraft are located near a black hole, and their relative positions are such that, due to the gravitational time ...
0answers
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### What about Time Contraction and Length Dilation? Do they even exist?

I recently started learning relativity, and I am writing an article about Length Contraction and Time Dilation. While summarising, I came up with few questions that I cannot find answers to. What ...
3answers
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### Is it possible to derive the time dilation expression directly from the space-time interval? [duplicate]

Is there any way of deriving the time dilation expression: $$\Delta t'=\gamma\Delta t$$ from the space-time interval: $$s^2=c^2t^2-x^2-y^2-z^2$$ I know how to derive the time dilation expression by ...
1answer
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### At what speed will the dilated time be twice the time on earth [closed]

At what speed will the dilated time be twice the time on earth? All my calculations using $$t'=\frac{t}{\sqrt{1-\frac{v^2}{c^2}}}$$ have given me strange results. Is this even possible. If not, why?
3answers
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### Relativistic length contraction (length measurement result differences)

I'm currently taking "Understanding Einstein" Coursera course before reading Smith's "Introduction to Special Relativity", and there's something I probably miss regarding ...
2answers
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### How we can visualise that gravitational potential, instead gravity is responsible for time dilation?

How we can visualise that gravitational potential, instead gravity is responsible for time dilation here on Earth? How possibly 'point A' can know that it should add some time dilation because at '...
0answers
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### I think there has to be relation or dependency between Time Dilation and Light Emitted from an object (density of Photons)

"If you watched an object fall into a black hole, no matter how long you watched, you would never actually see the object enter it due to time dilation" There is something not adding up here....
3answers
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### A question on special relativity

Imagine yourself inside a moving spaceship at velocity v(non zero velocity) Now imagine yourself holding a glass in your hand and you drop it. Now say after 5 sec the glass hits the floor and breaks. ...
2answers
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### Effects of time dilation on particles

According to time dilation, having 2 clocks, 1 further than the other from a gravitational center, makes the clocks run differently in respect to each other. My question is, what exactly happens at a ...
1answer
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### How does the equation of time period of a simple pendulum change in a very high gravitational field

I want to calculate the time period of oscillation of a simple pendulum in a planet with a very high gravity. In classical mechanics where time is absolute, the time period of a simple pendulum is T=...
4answers
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### Why isn't time dilation invalid for small values of the lenght of the clock?

I have to say that I'm not really sophisticated in physics, as I'm studying pure math. Still, there is a question I carry with me since late High school, and I wanted to ask it now: I remember vagily ...
2answers
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### Why don't we consider both time dilations in Special Relativity Questions? [duplicate]

If we have a periodic motion happening in frame A and if a moving frame B was to observe the event, B would see the time period reduced to $\frac{T_A}{1+v/c}$. This happens because of the finite ...
3answers
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### Can we increase (not decrease) time relative to earth?

If I understand special relativity correctly, when we accelerate an object around earth (or back and forth to another planet), the clock on the projectile will slow down and thus effectively time ...
1answer
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### How simultaneity of same event in time dilation works?

If an event has happened in space and that same event is observed from two different frame of references in one frame it takes more time to happen than other when observed(Time dilation). Now because ...
2answers
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### Will the man in the relativistic train stop counting instantly?

Consider if you wave at a person in a relativistic train for 3s. Since they're traveling 0.86c they will see you wave for 6s. However, from your frame of reference you see their timer as slow. As such,...
1answer
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### Why wouldnt this method of measuring absolute inertial motion work? [closed]

Einstein's famous light clock works like this in the reference frame of a rocket moving at .5c: And like this in the frame of a stationary observer: For the purpose of this variation on the original ...
0answers
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### Objects A and B fall into a black hole. B is released 1s after A. How do A and B see each other's trajectories? Esp. when crossing the event horizon?

Imagine we have three observers, A, B and C, all standing on a platform hovering just outside the event horizon of an ideal Schwarzschild black hole$^1$. At time $t=0$, as measured from the platform, ...
1answer
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### If humans can be shrunk down to the quantum level, does this mean that the shrunk human will experience time slower as they have smaller mass? [closed]

I am doing some research about "time travelling" by shrinking humans to the quantum level. It's something based on the delayed choice quantum experiment, so that we can go back to the past ...
2answers
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### I am confused about the passage of time for an outside observer versus an observer moving at the speed of light [duplicate]

Specifically, why would some say that the time experienced for those on Earth would be far greater than the time for light to travel to the destination and back. Example, I have heard it said that if ...
2answers
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### Time dilation on the same medium [closed]

Einstein's theory of special relativity says that time slows down or speeds up depending on how fast you move relative to something else. Does that mean, that time dilation can occur within the same ...
1answer
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### Straight line motion with uniform velocity in spacetime according to General Relativity

“The analog of a straight line in space is for space-time a motion at uniform velocity in a constant direction. The curve of shortest distance in space corresponds in space- time not to the path of ...
2answers
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### How do we know that the muons created by cosmic rays in the upper atmosphere are the same muons reaching our detectors at the surface?

I was reading the summary of most significant experiments done so far verifying muon's Special Relativity time dilation and lifetime extension here: https://en.wikipedia.org/wiki/...
1answer
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### Time dilation. What is the problem in my understanding?

This question is about special relativity. Assumptions 1. Speed of light is constant to all observers. Context: Let us imagine a train traveling in deep space. Now, let us suppose an observer 'A' ...
1answer
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### Special relativity v.s. “homogeneous time” within an inertial reference frame

I am asking a conceptual question. As we learned from classical mechanics, say Lagrangian formulation, as stated in Chap 7.9 of Classical Dynamics book by Thornton-Marion (5th Ed) p.260: in our ...
3answers
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### Do freefalling clocks within a small region of spacetime undergo gravitational time dilation?

I have several times seen explanations of gravitational free fall (eg, of a small object toward earth with no air resistance) that begin with the following claim about the particles of the free-...
1answer
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### Question about length contraction

If an observer A is in motion on a train relative to an observer on the train platform, B, and observer A shoots a laser which hits the wall and comes back, who measures the interval to be the ...
2answers
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### Can the ratio of the time (clock) rates at spacetime points A & B according to special relativity be different from the general relativity ratio?

According to special relativity, the rate, in an inertial coordinate system Int, of a clock moving with speed $v$ in Int, is reduced from the clock’s rate in a system in which it is stationary (its ...
1answer
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### Intuition About the Impossibility of Acceleration to C in Relativity. Is my Intuition Getting in the Way

Bob is riding a bicycle on a highway into space. His sister Alice watches him leave, and each rotation of the pedals brings Bob an absolute 1% closer to the speed of light relative to Alice. Bob also ...
2answers
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### Bell's paradox but with acceleration caused by a uniform gravitational field rather than rocket engines

Bell's paradox has in the past been the topic of quite heated discussions. It is posed in the context of a silk thread connecting two identical rockets whose engines are ignited at the same instant. ...
3answers
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### How Can I Reconcile the Glaring Problem with the Pulse-Clock-on-a-Train Time Dilation Explanation

I think the pulse-clock-on-a-train model for explaining time dilation is obviously flawed. The external observer never sees the light that travels from the emitter to the mirror, and back again. ...
1answer
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### Consequence of Time dilation of Planck's constant

Planck's constant is joules x second. However, the second can be time dilated from an external reference frame's point of view and seemingly extended. Following this logic. Would an external reference ...
2answers
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### How to get velocity of of observer? (Special Relativity)

An observer O at rest midway between two sources of light at x=0 and x=10m observes the two sources to flash simultaneously. According to a second observer O’, moving at a constant speed parallel to ...
1answer
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### What is observed as rate of change of proper distance with time due to space-expansion to a binary star approaches, then exceeds the speed of light?

Aliens on planet M observe a binary star at distance D with a 10 day "clockwise" revolution period. All other massive objects are FAR away and can be ignored. At time=0, the center of mass ...
2answers
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### Does an observer moving in a circle with constant angular velocity in space experience GR gravitational time dilation?

Assuming that there are no other planets or other gravitational sources around the observer in empty space, would the observer's very fast circular motion create GR gravitational or else called ...
2answers
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### Does Einstein's Equivalence Principle ignore time dilation? [duplicate]

It seems Einstein's equivalence principle is neglecting time dilation. If an observer is at rest in an inertial reference frame, free of any gravitation, she will experience time flow at the "...
2answers
400 views

### Is space a property of something that moves and does it move with it? [closed]

While reading Sheng Liu (2015) A new approach to the correction of Galilean transformation IN Physics Essays 28(2) I started thinking that space itself moves with objects that have mass. So anything ...
1answer
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### What would an interference pattern at relativistic speeds look like?

What would happen to a dual slit experiment's interference pattern if one observer was moving at relativistic speeds and another wasn't? For example if an observer performs a double slit experiment on ...
2answers
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### Another question about time dilation

Also dont understand this question i found on a past exam paper (31% got it correct): A robot is heading radially towards the surface of a planet in the Hoth system at a constant speed of 0.85c. ...
4answers
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### Why can no observer measure proper time here?

This is a relatively difficult question I found on a past exam (12% got it right): Two spacecraft travel in opposite directions, with spacecraft Ajax travelling at a speed of 0.5c and spacecraft ...
1answer
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### Do observers near a black hole see far-away onlookers speeding up?

I recently watched the movie Interstellar, and I have a question about time dilation, as it's a huge part of the movie. I know that to an onlooker, someone going near a black would appear to slow, due ...
1answer
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### How does time dilation apply at the centre of a black hole?

At the direct centre of a black hole, you have $0$ GPE, and the net gravitational force is $0$. So how does time dilation work there (or is this another physics mystery)? Specification: I refer to how ...
1answer
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### Reconciling the Rindler Metric with a multiplicative time dilation in a constant gravitational field

So looking over this answer: Does gravitational time dilation happen due to height or difference in the strength of the field? I am not sure if I am following completely. My issue relates to time ...
0answers
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### Clock synchronization and definition of simultaneity along a curve or contour in general relativity

What I understand so far Fix a point $A$ with coordinates $x^\alpha$ with respect to a frame $K$ with metric tensor $g_{\alpha\beta}$. Then take an arbitrary point $B$ infinitesimally close to it with ...
2answers
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### Gravitational Time Dilation and Equivalence Principle

My question relates to page 118 of these notes, which is reproduced below for your convenience. Specifically, I have difficulty understanding the line "This shows that time slows in a region of ...
0answers
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### Gravitational Time Dilation at height H Formula

The Wikipedia lists this formula for finding the time dilation in a gravitational field from one point to another point at "height" h, by integrating over the gravitation. However there is ...
1answer
359 views

### Can electric field cause time dilation?

Is it possible that time pass slower or faster if an object is in high electric field just like gravity?