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Questions tagged [time-dilation]

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Time and distance at the speed of light [on hold]

Considering a photon (or anything else moving at the speed of light) in it's own frame of reference. I'm having a discussion with someone and I'm trying to work out whether the time in that frame is ...
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What does it actually mean to say that time “speeds up” or “slows down”?

I was thinking lately about relativistic time dilation and time passing differently on other planets (which both, eventually turned out to be caused by the same principle). Now, quite naturally (as ...
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Time dilation of accelerating object vs caught by gravity well

Suppose an object got caught by the immerse gravitational force but at the same time it has zero net force acting on it like suspending above the surface of a planet, not siting on the surface where ...
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Time dialation in General realtivity and Special relativity are same? [duplicate]

I came across a thought experiment .Consider two persons A and B both have a very accurate and synchronized clocks now if A moves with a velocity compareable to c then its his clock will run slower ...
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1answer
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Is speed of light is the only way to measure time [on hold]

After reading up on special relativity, I understood that because of Einstein's postulates -the speed of light in free space is a universal constant Everytime we measure time for an event, directly ...
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1answer
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How can time dilation occur for one person but not another? [duplicate]

I have heard of the thought experiment where someone fly off in spaceships and come back younger than their twin on earth. But a fundamental idea behind general relativity was that motion can only be ...
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Why am I not getting the right values for the time it takes a spaceship to get to 0.9c? [duplicate]

I'm attempting this problem: Rocket undergoes constant acceleration from rest until it reaches a speed of 0.9c. The astronaut in the rocket feels a constant "induced gravity" of 1g. How long does it ...
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How can our universe have black holes? [duplicate]

Assuming that we were never inside a blackhole at any point in the history of the universe, how can blackholes exist against Gravitational time dilation? For any point in space time in the known ...
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3answers
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Speed vs Velocity of light in Light clock thought experiment

A related question has been asked multiple times (like here, here and here). But none of those answers are clearing my doubt. In fact they're furthering my confusion. My specific doubt is regarding ...
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3answers
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A twisted triple paradox

As far as I know when a person travels with some velocity relative to other person time runs slower to him relative to the other person (Because the velocity of light is constant in all frame of ...
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0answers
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How time dilated is the average particle relative to the big bang? [duplicate]

Particles created during the being bang have experienced time dilation by means of gravitation and general acceleration for the past 13.8 billion years. On average, how time dilated is the average ...
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Can someone travelling close to the speed of light witness the end of the universe? [closed]

I have read that objects with non-zero rest mass cannot attain light speed $c$. But for the sake of this question let us assume that Mr. X can get as close to $c$ as he wants. So this means that an ...
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2answers
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Time Dilation and Length contraction - thought experiment

Sorry if this is obvious, but I've searched and cannot find this answered. taking a minor change to the light clock experiment on a traveling spaceship. putting the clock in the horizontal position,...
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2answers
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Do planets experience time dilation as they orbit the sun and if so what effect would this have on their orbit

Do the planets experience time dilation as they increase / decrease speed around the sun and are experiencing higher and lower gravitational forces as they move from a closer position i.e. the ...
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1answer
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Is time passing really differs on other planets/in interstellar? [duplicate]

I am aware of the idea of time dilation (which I, by the way, asked another question about) on speeds, that get close to the speed of light. Though, I wonder what other (if any) forces and laws affect ...
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4answers
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How close should you get to speed of light, in order for time to be dilated?

Recently I was watching Carl Sagan's Cosmos: A Personal Voyage. In episode 8 ("Journeys in Space and Time") there is a scene presenting the idea of time dilation, due to traveling close to the speed ...
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1answer
53 views

Time dilation caused by gravity and special relativistic velocity [closed]

I am working on an exercise for my Relativity class. The exercise is: Two atomic clocks are transported in two aeroplanes once around the Earth in either eastern or western direction. For ...
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0answers
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Quantum wave function evolution and time dilation [closed]

We know that spin state evolves with time...but in non relativistic QM time dilation is not accounted ...so in Dirac equation does evolution of spin state with time depend on speed...i.e does time ...
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3answers
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Can length contraction help the moving observer reach a star system 'faster'? [duplicate]

Would an observer moving with close to the speed of light ($\sim 99\%$) towards a star system that's $20$ light years away perceive the distance as being less than $20$ light-years? If yes, how much ...
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1answer
155 views

Time dilation under different references paradox [duplicate]

I couldn't figure this out... I understand that if Alice is moving relatively to Bob at a high speed, Alice's time elapses slower than Bob's. So when Alice is back to Bob and compares the clock, ...
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2answers
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How to calculate distance of earth when observer in space ship which travel with speed of light

Suppose we have two observer one is on earth and other is in space ship. If we launch the space craft and a light ray at the same time from earth, after 1 minute, what will be total distance travelled ...
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1answer
52 views

The light signal path through the light clock [duplicate]

Light clock: floor, ceiling, light signal Case 1: when light colck is in rest, light signal propagates straight up. The time the light signal needs to pass the distance floor-ceiling-floor is t Case 2:...
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2answers
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Effect of time dilation in Cs atomic clocks?

Let's say, Observer A is at rest and Observer B is in a spaceship moving at a significant fraction of speed of light. B synchronized his atomic clock with A's when his spaceship just passed A. Now, ...
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2answers
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Would Earth clocks tick faster than a clock on a GPS satellite if we disregard gravitational time dilation?

If we disregard the time dilation caused by a GPS satellite being in lower gravity, would earth's clocks tick faster or slower from the satellite's perspective? Edit. From earth, we understand that a ...
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2answers
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A train passes an observer on a platform at half the speed of light. Who measures the proper time?

The proper time between two events is defined as the time measured in the reference frame in which both events occur at the same location. For example, a rocket that travels from Earth to Mars ...
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1answer
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Is the formula for time dilation applicable only in 1D?

According to time dilation formula $$ \Delta t_{observer} = \frac{\Delta t_{proper}}{\sqrt{1-(v/c)^2}} $$ I have basically two questions: (1) Is this formula applicable only for 1D motion, i.e. ...
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4answers
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Do photons experience time? [duplicate]

I was just thinking about how electric field and magnetic field vectors oscillate in a Photon. but then I remember that a photon doesn't experience any time so how can these vectors oscillate if the ...
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2answers
67 views

If we filmed what happens on an extremely time dilated planet in realtime

Say there was a planet that experienced insane time dilation due to orbiting a black hole, say 1hr on there is 7 years on Earth (something like that), and that it was close enough to Earth for light ...
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5answers
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Does time dilation mean that faster than light travel is backwards time travel? [duplicate]

Ok. So my question is, I've always heard it that Faster Than Light travel is supposedly backwards time travel. However, the time dilation formula is $$T=\frac{T_0}{\sqrt{1-v^2/c^2}}$$ And while it ...
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1answer
62 views

Time and acceleration [duplicate]

I am confused by the explanations of time dilation and gravity vs. acceleration. The consensus (and apparently experiments) is that time dilation in a gravitational field (not free-falling) is "as if" ...
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2answers
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Does the position in universe of a person not matter regarding death?

I might be completely wrong, but watching a documentary about time, the Einstein theory of relativity came up. From their explanation, time "slows down" depending where you are in the universe. I ...
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At what rate does a photon blue shift as it falls toward a black hole and red shift as time slows close to a black hole?

Perhaps I am thinking about this incorrectly when a photon arrives at an event horizon, from an observers perspective time has essentially stopped for it and the photon has red shifted completely. ...
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1answer
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Symmetry in gravitationnal time dilation: some details

This question is related to this topic However I am not satisfied with the answer. Let's try to be clear and use precise notations. Let's consider a non-charged and non-rotative sphere of mass M, an ...
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1answer
52 views

Time dilation for circular movement [duplicate]

As a thought experiment, I was trying to find a way to constantly dilate time while keeping an object effectively in place. I quickly decided that moving forwards and backwards wouldn't work—the speed ...
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3answers
133 views

Question about Special Relativity similar to twin clock experiment

This question is related to twin clock experiment but also involves a third clock. Here it goes: Suppose the relative velocity between clock 2 and clock 3 is given by $v=0.8c$. This would mean that ...
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2answers
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How can we measure relative velocity of fast objects when there is time dilation

First of all sorry about the question title. I find it very difficult to ask this in less than 150 characters. I am not a physicist and only have basic understanding of advanced physical concepts. So ...
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2answers
66 views

Gravitational time dilation and distance

If I have a light clock in the centre of the earth, and one at a distance from the earth, two observers at the clocks will agree that the inner-earth clock runs slower. But if we'd look with a magic ...
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2answers
196 views

Why doesn't Faster Than Sound information transfer imply time travel or violate causality? [closed]

I am struggling to understand the answer to What are some scenarios where FTL information transfer would violate causality? In particular, I have not seen a satisfactory rebuttal to the comment from ...
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3answers
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Does the Einsteins theory of a clock tower observed from a tram really explain time dilation?

We were shown a video in our class about time dilation which explained a Einstein's theory - the one where he was travelling in a tram and realized that if he travels at light speed, time will flow ...
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1answer
67 views

Shortening of distances in Relativity Theory

I am studying relativity theory and I have understood why distances become shorter from the perspective of someone who is travelling close to the speed of light. However, later on I read that the ...
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2answers
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Distance between events at relativistic speeds

The problem: A spaceship is travelling between Mountain $A$ and Mountain $B$, both of which erupt simultaneously as recorded by a scientist on the ground. The mountains are $300 \; \text{km}$ apart on ...
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How is time dilation associated with a ship with an Alcubierre drive?

Would a round trip cause the astronaut to age less or more or the same as an Earthbound twin? Normally, time dilation works as length contraction (an astronaut would see length contract as 1/gamma, ...
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1answer
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Does a photon box have gravitational potential, and cause GR time dilation?

I have read these questions: Does a "Photon Box" have gravitational mass? Does a box containing photons have more inertia than an empty box? And it made me curious. i understand that a ...
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2answers
87 views

Can a sufficiently large black hole have low time dilation near its event horizon?

First time posting here, please let me know if I miss anything! As I understand it, as the mass of a BH increases, its Event Horizon increases more than the rate of the mass being put in. In ...
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1answer
42 views

Can the rate at which time passes be changed? [duplicate]

Can the rate at which time passes be changed? For example, can time stop, slow down, or speed up? If so, how? Is it really time that is shifting or is it the measuring devices?
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Reproducibility of time dilation for Muon decays in the atmosphere

I have read a very clear and interesting paper about the relativistic effect of time dilation on Muon decays, which is now a famous experiment (Easwar and MacIntire, 1998). However the discrepancies ...
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3answers
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Time dilation and The Big Crunch [closed]

When/if the universe collapses in onto itself as described by the big crunch theory, would time slow down due to time dilation (relative to our experience) as all matter gets pushed together, or do I ...
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If time stops at the speed of light, how do photons vibrate in waves [duplicate]

I understand photons travel at light speed because they have no mass therefore they travel at the fastest possible speed, and at the speed of light time stops. If time is frozen at light speed how do ...
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1answer
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Where in the solar system could we place a clock, such that it would run the fastest (relative to a clock on Earth)?

I know that time dilation occurs between two reference frames with differing velocity, or differing positions in a gravitational field. Many examples that illustrate this point involve things like ...
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2answers
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How do we explain this new take on the old Twins Paradox? [closed]

Here's a new take on the age old Twins Paradox that I have not been able to figure out. We have two twins in two separate space ships at the same place and time. Twin A fires his thrusters for 1 year ...