# Questions tagged [time-dilation]

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### Universal Time System that takes into account Time Dilation [closed]

I'm creating a game with a space setting and whilst I could just use a simplified earth calendar and time, I wanted to look into what a calendar might look like once we have need of a time system ...
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### I have an issue with how long sunlight takes to reach Earth

It is a well-known fact that light from the Sun takes about 499 seconds to reach Earth. However, there is such a thing as time dilation; different observers experience time differently due to there ...
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### Is there tested proof of time dilation in the stationary frame, from the perspective of the moving frame?

I know that they have proven time dilation in the moving frame from the perspective of the stationary frame, eg comparing two cesium clocks in the jumbo jet test. But have tests been done on the other ...
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### Reconciling Wikipedia formulae for time dilation due to gravity and velocity

Wikipedia "Time dilation" shows the formula $\sqrt{ 1-v^2-v_e^2-v_r^2.v_e^2/(1-v_e^2) }$ where v is (perhaps) the 3D speed, $v_e$ is the Newtonian escape speed, $v_r$ is the radial speed. ...
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### How to figure out the time difference for events that happen simultaneously in one reference frame?

Suppose there's a clock on a spaceship and a clock on earth. The spaceship is moving toward earth at a constant relativistic velocity, and both clocks start simultaneously from the reference frame of ...
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### Gravitational time dilation at a point between two stars? [duplicate]

What will be the time dilation between a point on a line connecting the centre of mass of both stars? ( Gravitation time dillation at point p ) Assuming both stars have equal mass.
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### How long would one orbit around our galaxy's supermassive black hole be in the reference frame of S2

With the 2020 Nobel Prize in physics being awarded for the proof and discovery of supermassive black holes, I started doing some research and came across the star closest to our own galaxy's ...
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### If objects in motion experience time differently, how does my body stay synced when I move my legs or arms?

If I move my swing my arm really fast, the matter in my arm should experience time slower than the matter in my body. So how does my body still sync with each other? And a more general question that ...
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### What time dilation effect would occur when two objects near the speed of light approach each other? [closed]

What time dilation effect would occur when two objects would approach each other at e.g. 90% the speed of light? For each of the objects the other object appears to be moving at 180% the speed of ...
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### What is the general formula for time-dilation due to velocity and gravity together?

I see a formula in the Wikipedia entry on time dilation: $$\sqrt{1-v^2-v_e^2-\frac{v_r^2\cdot v_e^2}{1-v_e^2}}$$ where $v$, $v_e$, $v_r$ are the actual velocity, the escape velocity from gravity, ...
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### Is the Accretion Disk of a Black Hole just an illusion?

As a matter of fact, I recently learnt that as an object is approaching a black hole, to an outside observer the object seems to be getting slower and slower and will cross the event horizon after an ...
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### Hidden variable special relativity paradox

Members of this community were kind enough to contribute to my last paradox post: Special relativity paradox involving two light clocks I'm creating this new post to address the issues raised in that ...
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### Special relativity paradox involving two light clocks

I came up with this thought experiment that seems to exemplify a paradox. In this paradox, one clock is ticking unevenly for one observer and evenly for another. Essentially, the clocks record a “tick”...
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### Equivalence principle and time dilation

I apologize to ask, again and again, a question that seems to come back often, but I believe this is new. I am trying to test the equivalence principle applied to two similar situations: Flat ...
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### Shouldn't it be impossible to fall into a black hole? [duplicate]

Imagine that you, unfortunately, fell into a black hole. For external observers, you would slowly go closer and closer to the event horizon. Then, when you reach the event horizon, you would appear to ...
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### Would time dilation make it impossible to accurately convert between calendars across the galaxy?

A hypothetical signal is emitted from a known exoplanet thousands of light years away. The signal marks the occurrence of an epoch-worthy event on that planet, and we (the receivers) want to know ...
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As many of you have probably known there was a famous Hafele–Keating experiment, which was about a plane traveling the globe in order to prove predictions of special relativity and general relativity. ...
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### How can we see black holes form and gain mass if nothing can cross a horizon (when viewed from our reference frame)? [duplicate]

As things approach the horizon of a black hole, their time dilation approaches infinity. How then can we observe black holes gaining mass if, according to our reference frame, nothing can pass the ...
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### Is there an analogue to 'length' in time, in SR?

It seems to me that the notion of 'length' (in 1 spatial dimension, I define the length of a body in a certain referential to be the maximal spatial gap of two of its points at the same time) has no ...
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### Am I understanding the equivalence principle correctly?

So Einstein stated that gravity and acceleration are the same things in a local reference frame (please correct me if I misstated that). Here is what I think I understand and want you to verify if it ...
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### How much time dilation are we experiencing here on Earth? [duplicate]

We experience time dilation from speed and gravity, but we are in more than just the Earth's gravity field, but also the sun's and the galaxy's gravity field and we are both spinning at 1,670 km/h, ...
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### Is our metrics and/or constants geocentric?

Considering that all our metrics is now based on physical constants as measured here on earth, With earth having both gravity and velocity, as well as the whole solar system having too, and special ...
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### Equation for effects of the density on time dilation

The higher the density of an object is the more it will cause distortion on space and time. I want to know the equation that links density to time dilation. I found the Lorentz equations that link ...
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### Time transfer from proper to coordinate: apparent Special / General Relativity mismatching in theory

In SR we've learned that the time dilation for an observer moving clock w.r.t one fixed in a frame at rest is $$\tau = \gamma \tau_0 = \frac{\tau_0}{\left(1-v^2/c^2\right)^{1/2}}$$ ref: "Special ...
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### How to compute the composition of 2 gravitational time dilations?

This question could apply to stars orbiting a black hole, or planets orbiting a star, or moons orbiting a planet. The example numbers don't matter, just the concept. Lets say that a star has a ...
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### Question about proof of time dilation and length contraction

I was studying special relativity, but there is a "proof" than I don't understand: When we need to prove time dilation, we write the Lorentz equation in form of $\Delta t= \gamma \Delta t'$ ...
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### Generalizing a flat-spacetime-approach for time dilation to curved spacetimes

I would like to discuss an idea to generalize a flat-spacetime-approach for time dilation to arbitrary curved spacetimes. Starting Point Suppose we have - in flat spacetime - one inertial observer ...
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### When time does not run with same speed? [closed]

When we consider a solid body or a liquid, we consider that time does run in all parts of the solid and the liquid at the same speed. What however would happen with the solid or the liquid if time ...
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### Travelling 3.6 LY at $(3/4) c$, how much time passes for the traveler and how much time passes for the people in Alpha Centauri? [duplicate]

This specific thought experiment is for a story I'm writing. Assume a spacecraft can travel at 3/4 the speed of light. It leaves Alpha Centauri A and travels 3.6 LY. Being a non-physicist layperson I ...
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### Does time run slower at the center of a massive object?

Time runs slower near a massive object. I believe this time dilation is due to the gravitational potential present near the surface when compared to a distant point. What about the center of a massive ...
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### What determines intensity + range of a gravity field?

Related questions.. How does the Sun's gravity extend out millions of miles to influence the far reaches of our solar system? Reference: movie - "Interstellar", 2014 Nolan) / How does a ship ...
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### Help me to envision a man falling towards a black hole with all of the time dilation involved

I'm standing at a safe distance from a black hole and I'm in an Earthlike time frame of reference. Through my telescope I see a man starts to fall towards the black hole. I have looked at this ...
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### How can time be slowed down for two moving bodies simultaneously?

I am very confused now, after reading lot of articles and watching videos on special relativity. Let's assume there are only two bodies in universe one is moving at 80% of speed of light. Which means ...
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### Time dilation & Pions - Why Both Stationary and Moving Pions Should not See the Same Result?

One of the proofs for time dilation is how pions travel further than they should as their lifetime expands due to their travelling near speed of light. Now imagine you have 2 pions: one stationary on ...
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### TIME Dilation - What is the best source of Data listing all candles used for calculating universe expansion (Speeds, Measurement Dates)?

I am researching the impact Time Dilation of Earth (Velocity not gravitational) has on the Hubble Constant and am looking for available data. Hubble's Orbit = 8,040 mps; Earth Orbit around Sun = 29,...
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### Relative simultaneity in Special Relativity: was it ever used in real world examples?

I'm working on researches in the area of Special and General Relativity (SR/GR) focused on time dilation and I have a question to pose. Lorentz transformations (LT) introduce a time transformation ...
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### Confusion regarding common definition of proper time?

I am a bit confused regarding a commonly cited definition of proper time. For example, in Spacetime and Geometry, Sean Carroll writes: the proper time between two events measured the time elapsed as ...
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### Does the fact that light (photons) are bent by a sufficiently big mass prove that a quantum theory of gravity doesn't exist?

As is proven, light can be bent by a heavy mass in the context of classical General Relativity. In a quantum theory of gravity, the gravity field around a heavy mass consists of a condensate of (...
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### Why would time behave differently in different parts of the galaxy? [closed]

I watched Interstellar and I got really confused around different time thing. How can it be possible at all that time is different at different places in the universe? Please explain.
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### How does the period of an oscillating mass-spring system comply with the relativistic time dilation as viewed by a moving observer?

Consider a simple mass-spring system. The spring is attached to the ceiling in the lab frame of reference and a block of mass $m'$ is suspended from the spring. The mass starts to oscillate with ...
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### Visualization of object falling into black hole from the perspective of a distant observer

There exist a few relativistic renderings, even videos of this kind of event from the perspective of the infalling object, yet I have never seen the same event from the perspective of a distant ...
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### Why is the photon clock equivalent to all clocks?

I can understand why, if the speed of light is invariant, a photon clock would tick slower. I find this explanation very useful in terms of introducing the idea of time dilation (also because it ...
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### Question about the circumstances of apparent causality violation due to objects with negative ADM mass

In The Generalized Second Law implies a Quantum Singularity Theorem, Aron C. Wall asserts that an object with a negative ADM mass would produce a "Shapiro advance" rather than the ...
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### Effect of Earth's Rotation on Time [closed]

According to Wikipedia: Earth's rotation is slowing slightly with time; thus, a day was shorter in the past. This is due to the tidal effects the Moon has on Earth's rotation. Atomic clocks show that ...
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### Time (or rather, $dt$) as a Vector? [duplicate]

I want to preface this by saying that I'm by no means experienced with the field of physics, but while on my commute this morning, I started thinking: Basically, I thought about time being a fourth ...
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I want to simply eliminate the effect of acceleration, which is the cornerstone in resolving the traditional twin paradox, through the following thought experiment: Assume twins $A$ & $B$ are ...
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### Relative time dilation at relativistic speeds

As I understand it (feel free to correct me if I'm wrong here), the core tenet of Einstein's theory of special relativity is the idea that if you were on a sealed train moving at any constant velocity ...
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### Why does time dilation imply length contraction? [duplicate]

This is probably a nonsensical question, but I'm having trouble wrapping my head around it. I'm thinking of the classic scenario where a stationary observer is watching a spaceship move horizontally. ...
So I'm having some problems understanding how if a moving object emits light, the speed of that light is still the constant, $c$, speed of light. So according to Einstein's theory of relativity, light ...