# All Questions

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### A beginner's question on time dilation [closed]

I have just started understanding relativity so the question might look absurd. I know that the faster we move through space , the slower we move through time. But I haven't understood it fully. I ...
118 views

### In what sense do photons exist?

In a photon's frame of reference travel is instantaneous, so presumably a photon cannot exist in its own frame of reference. I am not aware that a "beam" of photons interacts via gravity despite ...
88 views

### Spacetime diagrams and their interpretation

Recently started an introductory course of relativity, and started learning about space time diagrams. I couldn’t figure out what are the uses of a spacetime diagram as an alternative to Lorentz ...
21 views

### What creates the physical difference in ageing when travelling close to the speed of light? [duplicate]

I probably have a fundamental misunderstanding, so correct me if I'm wrong. When travelling close to the speed of light, movers experience time dilation, which is what results in the phenomenon of ...
76 views

### Method to observe clocks on spaceships moving near $c$?

I have read the explanation for clocks slowing down on a spaceship moving relative to a stationary observer -- something like a beam of light between two mirrors taking longer for the observer to ...
91 views

### When photons are moving at the speed of light, how come they change in position?

From what i know, photons are moving at the speed of light and that means the time that photons are experiencing is zero, but here is the thing... If the time is zero how can they travel astronomical ...
89 views

### Problem in Special Relativity [closed]

"A space probe is sent to the vicinity of star Capella, which is $D = 42.2 \ light \ years$ from earth. The probe travels with a speed of 0.9930c. An astronaut recruit on board is 19 years old when ...
76 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 ...
205 views

### Special Relativity Muon Decay [duplicate]

When talking about how muons reach earth even though their half-life is very short the explanation of time dilation is given. From earth's frame of reference, the Muon's clock is "slowed down" so is ...
732 views

### Determining the rest frame

Sorry if this has been asked before in some way, I did try looking through the special relativity tag and didn't really see a good answer to my question. I am having trouble determining which frame ...
363 views

### How Lorentz transformation is connected to reality and physics?

I don't understand whats the meaning of Lorentz transformation in Special relativity. In physics, the Lorentz transformations (or transformation) are coordinate transformations between two ...
262 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 ...
9k views

### 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 ...
219 views

### Does Minkowski diagram show that time goes faster in “moving” frame of reference?

I have a question re the diagram that appears at: http://www1.phys.vt.edu/~takeuchi/relativity/notes/section12.html The diagram purports to show that the observer in each frame of reference will ...
384 views

### Why is the Lorentz transformation's time transformation not just the time dilation?

In Taylor's Classical Mechanics text, he derives the Lorentz transformation from length contraction which, in turn, uses time dilation. But doesn't the use of length contraction necessitate that the ...
2k views

### Causality and speed of light

It is accepted that the speed of light is the speed of causality. If we exceed the speed of light, the order of cause and effect breaks down. This happens as we see our surroundings moving backward in ...
568 views

### Time goes slower the faster you go. What happens to time if you go too SLOW? [closed]

Time dilation is clear about what happens when you go faster than an earth observer, and about what happens when you travel at c. But earth is also moving, and thus we humans are not at the slowest ...
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### Does time dilation make travelling close to the speed of light redundant? [duplicate]

I find time dilation confusing so I'm not sure if it is a relevant factor. Lets say you have a spaceship. There's no such thing as faster than light travel, but you do have inertial dampener ...
3k views

### 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 views

### An experimentation on time dilation [duplicate]

In the video https://www.youtube.com/watch?v=ev9zrt__lec from 03:00 to 05:00 I hope that both the clocks would read the same equal amount ,say,1 revolution, in measuring the time elapsed for the ...
99 views

### How did we get the time dilation equation from this proper time equation?

As you can see in the text book we get time dilation equation from equation number 1.9 I just can't see how he did it here: For now, we define the proper time between events B and the origin to be ...
65 views

### Traveling close to the speed of light, would a person (or anything else) have a longer existence or would the existence be passing in slow motion?

If something, let's say, an electron or a person, travels at some speed close to the speed of light, time would slow down, right? But would it be passing in slow motion or would it have a bigger ...
412 views

### Lorentz Transformation in Different Reference Frames

TO ALL: Thanks to the help of many dedicated forum members, I have learned that this problem can be explained by understanding Minkowski diagrams. Here is a consolidated list of helpful links: https://...
120 views

### Observers at the speed of light [duplicate]

Just a quick question to help me see if my reasoning is right. The speed of light is constant from all frames of reference. So does this mean that an observer travelling at the speed and taking into ...
480 views

### Will moving observer see time dilation?

Please look at this animation. The green dots and red dots in the animation represent spaceships. The ships of the green fleet have no velocity relative to each other, so for the clocks onboard of ...
745 views

### Is a digital clock affected by special relativity?

A well-known effect of SR is time dilation. For example, a clock going at $0.5c$ is slower than a stationary one. It seems bizarre to me that a mechanical clock and a digital one would both run slow ...
85 views

### Synchronized Clocks in Inertial frame

Will the synchronized clocks placed in an inertial frame remain synchronized forever?
549 views

Let $S$ and $S'$ be two frames, moving with velocity $V$ relative to each other. Treat $S$ as a stationary frame, then $S'$ moves away with velocity $V$. Let $\gamma = 7$ so that $\Delta t = 7\Delta t'... 4answers 718 views ### A spool in Einstein's theory of special relativity I would like to know how can we model a simple spool that unrolls at speed close to light (in the frame of the wire remaining on the ground AND in the frame of the translatory motion of the rolling ... 1answer 218 views ### Is the traditional explanation of why moving clocks run slow correct? Like most people I struggle to get my head round special relativity. I read a superficially-plausible explanation for why a moving clock runs slow from the point of view of an observer in a rest frame ... 1answer 134 views ### Understanding of derivation of time dilation While deriving time dilation using the two postulates of Special theory of relativity we imagine that a light pulse is traveling back and forth between 2 mirrors. In the rest frame (when the observer ... 3answers 710 views ### A Twist in Twin Paradox I totally understand the reasons behind why the twin on Earth is aging faster than the travelling twin. However, all the explanations within the twin paradox somehow involves the fact that the ... 2answers 603 views ### Reciprocal Time Dilation in Special Relativity [duplicate] I'm trying to understand theory of special relativity, but there is one thing that really makes me confused which is reciprocal time dilation in special relativity. In special relativity, the time ... 1answer 199 views ### How is time dilation consistent between both observer? There is a special variant of time dilation paradox bugs me. Imagine there are 2 small spaceships moving toward each other in constant speed. Each ship has an observer on-board. According to both ... 1answer 336 views ### how long will take for an astronal travel in near lightspeed in his point of view I always had a question about relativity. Suppose an astronaut in orbit Saturn just must reach earth fast as possible. Your ship can travel at any speed between 0 and the speed of light. the distance ... 1answer 272 views ### Does Inertial time dilation demonstrate that Time is not a dimension? [duplicate] If time is a dimension and 'now' simply an expression of your position with respect to that dimension, the progress of any object along that dimension should remain in step with all other objects. By ... 2answers 130 views ### Time Dilation diagram on wikipedia The wikipedia article on Time Dilation (http://en.wikipedia.org/wiki/Time_dilation) has an explanation involving the following two diagrams: I have some problems with these diagrams. In the second ... 3answers 145 views ### How does an electromagnetic field oscillate if time does not pass for the speed of light? As far as I'm aware, traveling at$c$will prevent time passing due to time dilation. Electromagnetic waves rely upon oscillations to propagate. Since oscillations rely upon the passing of time, how ... 2answers 621 views ### What does$v=c\$ in the Lorentz transformation for time tell us?

For the simpler cases as boost in the x-direction, the time dilation formula following the Lorentz transformation for time is $$\Delta t'=\gamma(\Delta t-v\frac{\Delta x}{c^2})$$Now, we observe that ...
1k views

### Time difference between two moving inertial frames of reference [closed]

This is a question I am trying to solve: Let S and S' be two inertial frames of reference and S' is moving relative to S at a velocity of 0.6c. When x = x' = 0, t = t' = 0. At t = 2 x 10-7 s, an ...