# 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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### Moving clocks tick slow and time dilation

Here’s what I don’t understand about time dilation. Alice is at rest and Bob is moving with velocity V with respect to Alice. Let’s say Alice measures two events separated in time by $\Delta t_A$ ...
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### Shrinking of objects in General Relativity [duplicate]

As well describe by special relativity, an object moving at high speed will look shrunk by an observer outside the reference frame at rest. My question is, in the context of general-relativity, ...
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### Failed approach to get time dilation equation

Imagine two reference frames were at the same position initially and a torch remained there in turned off condition . Now the observer in reference frame $S$ saw that the torch is turned on and the ...
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### Does time really slow near the speed of light or does it only seem that way to an outside observer? [duplicate]

I was lying awake last night struggling to sleep as one does, thinking about time and Einstein's concepts of relativity and having some fun with thought experiments similar to the one Einstein ...
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### Relativistic ship and base on Earth talking

Let say humans make it possible to travel so close to the speed of light that time dilation for the ship can achieve 100 times the time of a standing still object. So one of that ships starts its ...
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### is a Joule of energy relatively different in a different gravitational potential due to time dilation?

A joule of energy is a function of kg x m^2 x s^-2 so it is related to time. Would this mean that if I am looking from earth to a much larger planet with greater gravitational time dilation, that ...
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### Why time dilation is enlarged over long distance ? (small movement of head leads to huge shift of the plane of "present")

Considering the special relativity, we know that the time for the moving object (relative to us, for example) is slower (relative to us). Now consider the Andromeda paradox explained by Roger Penrose (...
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### At which fraction of light speed could I expand ten times, and 100 times, my clock's ticking? [closed]

I face this problem in special relativity: for dilating the intervals observed in an at rest, foreign frame of reference by ten times, and also by one hundred times, how much should I reduce light ...
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### Does length contraction imply that an object you are travelling towards looks bigger in your FOV?

Let's say I'm heading towards a star 10 ly away but I am traveling at 298289729 m/s (~99.49% of light), so that I will reach the star in 1 year from my perspective. This would cause the length to ...
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### Synchronization of Clocks in Special Relativity, when ship travels near the speed of light [closed]

Suppose a telescope can see a clock inside a ship traveling near the speed of light, in a circular (constant radius) fashion. The telescope is at a certain distance perpendicular to the circle of the ...
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### Muon experiment

I am new to special relativity and I'm finding it really hard to understand concepts such as time dilation. The example I'm trying to understand is that of a decaying muon. The muon starts falling ...
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### Using time dilation to find universal frame of reference

Before I ask this question, I just want to clarify that I am by no means an expert and that this question most likely came about due to my ignorance on the subject. If this is the case, please let me ...
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### One-way speed of light determined by measuring Time Dilation in two directions? [duplicate]

I know it’s theoretically impossible to measure the one-way speed of light by measuring the time it takes to pass by two points. The issue is with synchronizing two clocks and Time Dilation that is ...
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### How fast does time pass in a void?

How much faster does time pass in a comsic void compared to earth? I know that the passage of time on earth is affected by the gravities of Earth, the Sun and the Galaxy, as well as by nearby galaxies....
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### Is it theoretically possible to create a 'time bubble', where inside the bubble time will stop or at least slow down radically? [closed]

I am a layman who dabbles online in physics, I thought this would be cool and has probably been done in sci fi already, but was wondering if it were actually possible.
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### Can time dilation make time go FASTER? [duplicate]

We have all heard of the famous twin paradox, in which the twin traveling at relativistic speeds ages slower, and finds his twin brother is now years older than him. What about the other way around? ...
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### Does an observer falling into a kerr black hole see the universe rotate an infinite number of times? [duplicate]

Does an observer falling into a Kerr black hole see the universe rotate an infinite number of times? Since to an outside observer it takes infinite time to fall into a blackhole, if the hole is a Kerr ...
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### Time and speed of light in Relativity

Time running slower near a massive object, but the speed of light does not really change near a massive object, according to Relativity - it just curves. Is not time directly related to the speed of ...
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### Wouldn't Miller's planet be fried by blueshifted radiation?

In Interstellar, wouldn't Miller's planet be fried by blueshifted radiation? The 61,000x time dilation multiplier would make even cosmic background radiation photons into extreme UV photons. I was ...
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### Under the equivalence principle, does a bullet experience gravitational time dilation during acceleration?

Does the equivalence principle include gravitational time dilation for an accelerating object? A bullet accelerates in the barrel of a gun at 10^6 m/s^2. If this acceleration was the gravity of a ...
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### Given the time dilation at the event horizon plus black hole evaporation, can anything really ever enter a black hole? [duplicate]

There are many thought experiments about what it would be like to fall into a black hole, spaghettififaction, the singularity at the center and so on. But to me it seems that no object could actually ...
1 vote
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### Would this method work for generating sustained arbitrarily high time dilation in the center?

Let's say we have a series of a large number of spherical shells. Each shell has twice the mass and radius as the last. There may be thin poles or ropes to make sure inner shells don't move around. ...
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### Does anybody know a physical explanation for the refractive index independence of the Sagnac Interferometer fringe shift?

It is generally accepted that the fringe shift produced in a fiber optic Sagnac interferometer is independent of the refractive index of the fiber. In fact, the waveguide aspect of the fiber is not ...
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### What does and observer inside of a collapsing shell observe?

What does and observer inside of a collapsing shell observe? Lets say we have a shell of matter collapsing to a black hole. What would observers near the center see? How would the rest of the universe ...
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### What would happen if the two mouths of a wormhole are receding away from each other faster than light?

If wormholes could form naturally, and point A and point B were in galaxies receding from each other faster than light, what would happen to something going from one end to the other? Physicist Kip ...
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### Would an accelerated-time space region deflect projectiles?

Suppose a spherical region in space in which time goes faster. Would projectiles shot at it be deflected away, as light is deflected by a material with a lower refractive index? Edit: This would also ...
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### Where does an object's length contract with respect to as it approaches lightspeed? [duplicate]

According to length contraction, for an inertial observer, an object's length contracts in the direction of its motion as it moves faster. However, as an object's length contract, it would contract ...
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### Observing from a reference frame moving with high speed

Suppose at a distance $x$ from earths surface,a rocket comes with $v$ velocity which is comparable with the speed of light. Suppose lifetime of the rocket is $T$. We want to know whether the rocket ...
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### Time dilation - do all moving clocks run slower? [duplicate]

I have some doubts about getting the time-dilation concept right, so I would like to suggest a scenario and see if my conclusions are right or wrong. Person A is on Earth, Person B is on a spaceship. ...
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### Worm hole travel without time travel? [duplicate]

If the two endpoints of a worm hole have to remain stationary does travelling and communicating through them still facilitate time travel? For example If I travel through a worm hole from Earth to 20 ...
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### Explanation for invariance of $c$ / Lorentz transformations? [closed]

First of all, I want to make it clear that I'm not proposing here that I have "discovered" something(I'm just trying to save myself here from accusations about being a relativity denier or ...
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### Special Relativity: If speed of light is constant, then why measured lengths and times aren't changing in the same way? [duplicate]

Special relativity postulate says that speed of light is constant for all inertial observers, meaning that measures of time and distance must accommodate in a way to show that speed of light is the ...
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### Does time beyond a Rindler horizon run backwards in the accelerating frame?

In the book Explorations in Mathematical Physics (p. 262) by Don Koks, he discusses a traveler who has constant proper acceleration and therefore a Rindler horizon behind her, about which he says: On ...
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### Error in Derivation of Time Dilation Formula [closed]

Suppose a train is travelling forwards with speed $v$ as perceived in the inertial reference frame of the railroad. Suppose moreover that there is a lightbulb at the leftmost-end of the train, and ...
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### Problem involving time dilation

Let us suppose a spaceship has left earth with velocity $v$ and after crossing a certain distance $d$ from earth, a light signal is sent from earth(which assume travels in the speed of light). At some ...
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### Gravitational red shift and gravitational time dilation

I am a beginner in general relativity. I read the relevant section 9.1.5 in Relativity make relatively easy by Andrew Steane. After that, I thought a problem in gravitational red shift and ...
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### How is gravitational time dilation different from the time dilation from Special Reativity? [duplicate]

In Special Relativity, acceleration i.e. a changing velocity 4-vector results in time dilation, that is asymmetric aging of observers. In General Relativity, the 4-vector does not change along a ...
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### Frame of Reference chosen in Hafele-Keating experiment

I do not understand why we chose the frame of reference which is at rest with respect to Earth's center. I get that it does not experience the acceleration due to centripetal force of Earth's rotation ...
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### Is time dilation due to relative velocity equivalent in principle to time dilation due to relative gravitational strength?

Is time dilation due to relative velocity and relative gravitational strength equivalent? That is, similar to Einstein's thought experiment where an observer in an enclosed capsule with no windows ...
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Your clock run slower than the clocks on Earth?
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### Interstellar Question

Assuming that a Miller's planet was possible and that the time dilation was as specified 7 years / hour. Now assume that people on Miller's planet can view Earth through their telescopes. They see a ...
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### Time slows down with speed compared to what reference point?

So as far as I understand time dilation it means that time slows down as an object approaches lightspeed. This is an issue even with for example satellites around earth compared to people on earth (...
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### Paradox arising from using a black hole to go into the far future?

Let's say you have a very powerful spaceship and decide to travel to the event horizon of a supermassive black hole, but just before crossing you reverse your thrusters and escape. According to my ...
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### Speed of the light traversing an accelerated elevator

Consider an upwardly accelerated elevator as in the figure. From outside the elevator, an inertial observer (unseen in the figure) shoots light perpendicular to the moving direction of the elevator. ...
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### Will a clock that is isolated and stationary with respect to the CMB report the highest possible value for the age of the universe?

We have a very special clock that has existed since the dawn of time. Its purpose is to measure the age of the universe. It is always very far from any massive body or gravitational field and it is ...
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