Questions tagged [time-dilation]

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92
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2answers
6k views

Is there such thing as imaginary time dilation?

When I was doing research on General Relativity, I found Einstein's equation for Gravitational Time Dilation. I discovered that when you plugged in a large enough value for $M$ (around $10^{19}$ ...
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8answers
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How can time dilation be symmetric?

Suppose we have two twins travelling away from each other, each twin moving at some speed $v$: Twin $A$ observes twin $B$’s time to be dilated so his clock runs faster than twin $B$’s clock. But twin ...
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8answers
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What is time dilation really?

Please will someone explain what time dilation really is and how it occurs. There are lots of questions and answers going into how to calculate time dilation, but none that give an intuitive feel for ...
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8answers
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If the speed of light is constant, why can't it escape a black hole?

When speed is the path traveled in a given time and the path is constant, as it is for $c$, why can't light escape a black hole? It may take a long time to happen but shouldn't there be some light ...
58
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5answers
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Can radioactivity be slowed through time dilation?

Can radioactivity be slowed using the effect of time dilation? If you put cesium, tritium or uranium in a cyclotron at relativisitic speeds, do their half lives become longer in our frame? Could ...
55
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11answers
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Why isn't length contraction permanent even though time dilation is?

It's my understanding that when something is going near the speed of light in reference to an observer, time dilation occurs and time goes slower for that fast-moving object. However, when that ...
51
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4answers
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Does time move slower at the equator?

While answering the question GPS Satellite - Special Relativity it occurred to me that time would run more slowly at the equator than at the North Pole, because the surface of the Earth is moving at ...
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4answers
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Are today's chip scale atomic clocks accurate enough to conduct my own test of time dilation?

Regarding the Symmetricom SA.45s Quantum™ Chip Scale Atomic Clock, is it accurate enough to test time dilation if I place one at sea level, and one on a mountain? It's accurate to 3.0⋅10−10 per month....
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5answers
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Is gravitational time dilation different from other forms of time dilation?

Is gravitational time dilation caused by gravity, or is it an effect of the inertial force caused by gravity? Is gravitational time dilation fundamentally different from time dilation due to ...
25
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4answers
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How to travel between two stationary worlds in the least amount of time? (time dilation)

Let's imagine there are two, isolated, stationary worlds in space (called A and B), very far apart from each other. I live on World A, and some aliens live on World B. I want to learn about the ...
23
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2answers
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Why isn't the center of the galaxy “younger” than the outer parts?

I understand that time is relative for all but as I understand it, time flows at a slower rate for objects that are either moving faster or objects that are near larger masses than for those that are ...
20
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4answers
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Time dilation all messed up!

Okay! There is a problem with my logic and i cannot seem to point out where. There's a rocket ship travelling at close-to-c speed v without any acceleration (hypothetically), and there is an observer ...
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3answers
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Energy Conservation Dilemma

Assume that a man is travelling in a space ship at a certain relativistic speed with respect to a man at rest at some point in space, such that 3 minutes in the ship is equal to 5 minutes for the ...
18
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2answers
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So Black Holes Actually Merge! In 1/5th of a Second - How?

I've read a lot of conflicting answers in these forums. However, today saw the awesome announcement of gravitational waves. Two black holes merged: http://www.slate.com/blogs/bad_astronomy/2016/02/11/...
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6answers
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Is it possible to watch the same distant star's supernova event twice?

Usually relativistic time dilation effects require something traveling near the speed of light. But the high speed requirement can be replaced with a high distance requirement instead. Traveling away ...
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7answers
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Can a ultracentrifuge be used to test general relativity?

With today's ultracentrifuge technology, they can spin so fast that the sample can be subjected to accelerations of up to 2 millions Gs. That is equivalent to two solar masses. Has someone tried to ...
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7answers
7k views

According to special relativity, has the future already happened? [closed]

According to special relativity, a photon traveling at the speed of light, does not “experience” time. It is traveling into the future at an infinite rate, right? That would mean that everything that ...
15
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1answer
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What is the maximum time dilation factor when orbiting a rotating black hole?

Suppose one spaceship is stably orbiting a rotating black hole and another is far away from the black hole. What is the maximum time dilation factor between the two ships? Can it be made arbitrarily ...
14
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2answers
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Understanding Time Dilation at the Event Horizon

I was recently reading about the event horizon of black holes and came across the fact that, to a "stationary" observer, it takes forever for someone to fall into a black hole. The sources claim that ...
14
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1answer
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Movie Interstellar - Question about Escape Velocity

The movie Interstellar shows people on a water planet where time is dilated so much that 1 hour is equal to 7 years back on Earth. Even though they lift off from Earth using a Saturn-V two stage ...
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4answers
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Time dilation clock experiment: what would happen if the clock were flipped 90 degrees?

I have seen and understood the classical thought experiment where you imagine a "light clock" sending a light ray between two mirrors while moving in a perpendicular direction to the lights direction ...
13
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1answer
674 views

Can a difference in the “speed of time” introduce acceleration? [closed]

Hypothetically, lets say we have a space divided equally into two adjacent areas where (somehow) in one of the areas time goes by at half the speed as the other area. Or specifically, when a clock in ...
11
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2answers
982 views

If you hover just above the event horizon of a black hole, would you see the future of the universe?

Let's do this thought experiment. You have an insanely powerful rocket and it can accelerate to 0.999999c. Now you fly to a supermassive black hole and hover just above its event horizon, where the ...
10
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6answers
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Is time dilation an illusion?

It is said that we can verify time dilation by flying a very accurate clock on a fast jet or spaceship and prove that it registers less time than the clocks on earth. However, the clocks on earth ...
10
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2answers
928 views

What is the highest speed time dilation has been tested?

What is the highest speed time dilation has been tested? How close to the Special Relativity prediction did it get?
10
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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 ...
10
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2answers
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How is quantum entanglement consistent with the relativity of time?

It is well known that relativity predicts time moves slowly near massive objects e.g.. time moves slowly for clocks on earth as compared to clocks on GPS satellites by about 40000 nanoseconds. ...
10
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0answers
215 views

How do gravitons make time go slower?

In the classical view of General Relativity, time moves slower near massive objects where the gravitational field (spacetime curvature) is stronger. In the quantum view however, the gravitational ...
9
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1answer
113 views

What's the smallest height difference over which gravitational time dilation has been experimentally observed?

In a famous experiment, reported in Optical Clocks and Relativity. CW Chou, DB Hume, T Rosenband and DJ Wineland. Science 329 no. 5999 pp. 1630-1633 (2010); NIST eprint. and nicely described in ...
9
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1answer
285 views

Would time dilation cause a planet to rotate?

For the sake of the argument lets use a black hole so the time dilation effects are greater and the planet in question is orbiting close enough to have significant TD effects but far enough to not ...
8
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2answers
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Why we don't see time dilation in stars orbiting black hole?

We have images of stars orbiting black holes or black holes destroying near stars, but why do we see the stars moving normally? I mean, if time dilation does exist, shouldn't we see that stars slow ...
8
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4answers
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Time dilation for a moving electronic clock

Is this a correct application for the time dilation theorem? Suppose an electronic clock has a copper wire of length $d$, which allows the electrons to take $t$ seconds to complete a cycle on the $d$-...
8
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0answers
173 views

Radiative equilibrium in orbit of a black hole

According to Life under a black sun, Miller's planet from Interstellar, with a time dilation factor of 60,000, should be heated to around 890C by blue-shifted cosmic background radiation. How they ...
7
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4answers
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Quick time dilation question (Proper time)

This is super frustrating. I literally cannot grasp the concept of what proper time is and I have no idea why. There's something I'm missing here. If someone is standing on earth and there's a clock ...
7
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2answers
698 views

Does Earth experience any significant, measurable time dilation at perihelion?

Is there any measurable time dilation when Earth reaches perihelion? Can we measure such a phenomena relative to the motion of the outer planets?
7
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2answers
270 views

Does STR imply that time dilation is effected by an orientation of clocks?

Many texts about STR time dilation use as an example thought experiment with 2 mirror photon clock. The conclusion of this experiment is: In a frame moving relative to the clock, they will appear to ...
7
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2answers
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Does gravitational redshift imply gravitation time dilation?

The EEP is used to justify that if an observer on the ground shoots a beam of light towards a tower, then when the light reaches the tower, it will be red shifted. This is because of what happens in ...
6
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2answers
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Do strong magnetic fields cause time dilation?

Does a strong magnetic field cause time dilation? If you have a strong magnetic field, and a magnetic radio active material, does the half life of the material change due to field?
6
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4answers
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Would time speed up near a large body of negative mass relative to observers in micro gravity?

Time tends to slow down near objects with large amounts of positive mass relative to observers in micro gravity. Considering that negative mass is the opposite of normal mass and would time tend to ...
6
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3answers
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Are length contraction and time dilation physical?

Are length contraction and time dilation real physical phenomena, or are they just a measurement issue?
6
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3answers
314 views

Why cannot a perfect clock exist?

I have a question about the reason Feynman gives for why a perfect clock - a clock that remains in sync while in motion with a stationary clock, cannot exist. It is clear why the "light clock" (...
6
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1answer
119 views

Two places having same gravitational acceleration - Do they also have same curvature of space time?

If there are two places (possibly on/above two different planets) having same gravitational acceleration (g), would it imply that the two places have same extent of space time curvature and will have ...
6
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2answers
942 views

Question/Doubt about Time Dilation Symmetry in Special Relativity

Apologies if this has been asked and answered before, as I am still having doubts reconciling the symmetrical effects of time dilation (i.e each frame sees clocks of other frame slowing down), and I ...
6
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1answer
154 views

Twin paradox with one twin in orbit, one in radial free-fall

Many questions on Physics SE relate to the twin paradox, but I did not find any that ask this specific question. Suppose that object A is in a circular orbit around a spherically symmetric, non-...
6
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3answers
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Why do GPS satellites care about Earth clock at all? (relativity)

Many online resources make grandiose claims about how GPS would be useless without relativistic corrections. Specifically, they outline that satellite clocks runs slower by 7μs/day due to special ...
5
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3answers
523 views

Can a photon that is emitted from a denser part of the universe to a less dense part appear redshifted?

Galaxy one is located in a dense area of the universe and galaxy two is located in a less dense part of the universe. Would galaxy one appear red-shifted to galaxy two? Is the mass density at our ...
5
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2answers
754 views

Gravitational time dilation compensated by acceleration

I would like to compare the time indicated by two clocks: clock A is located at the top of a mountain, the clock B is in an helicopter flying stationnary at the same altitude than the clock A. Clock ...
5
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4answers
136 views

If a photon doesn't experience time, how can it have a frequency? [duplicate]

It is said that photons, moving at c, do not experience time. But then, if a photon doesn't experience time, how can it have a frequency?
5
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3answers
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Where in Universe does time move faster than it moves on Earth?

I know that around black holes and areas with dense gravitational fields, time is supposed to move a lot slower, meaning that for example, a year in Earth might be just a second around a Black Hole. ...
5
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4answers
148 views

Time dilation in a gravitational field

A friend and I were talking about relativity and we had different opinions about this situation: If I choose a frame of reference on the surface of a planet, would time "run" differently between the ...