Tagged Questions
2
votes
2answers
80 views
Does inertia increase with speed?
I have heard that when the speed of the object increase, the mass of the object also increase. (Why does an object with higher speed gain more (relativistic) mass?)
So inertia which is related to ...
0
votes
1answer
26 views
Viewing a reference frame from inside of it?
Can one observe one's own frame of reference without moving out side the frame?
For example, if you are on a train and you throw ball in the air up and down.
When you are on the train (frame 1) you ...
1
vote
1answer
76 views
The definition of Lorentz transformation
I know that the Lorentz transformation, when two frames $\mathcal{S}$ and $\mathcal{S}'$ are in standard configuration (the axes are all parallel to their counterparts in the other inertial frame) is ...
4
votes
2answers
165 views
What is the Andromeda Paradox?
I have been studying causality (specifically why there is no such thing as a simultaneous instant of time across all observers) recently and I keep hearing references to the Andromeda paradox. Can ...
0
votes
3answers
106 views
Stuff can't go at the speed of light - in relation to what? [duplicate]
We all know that stuff can't go faster than the speed of light - it's length becomes negative and all kinds of weird stuff happens.
However, this is in relation to what? If two objects, each moving ...
1
vote
4answers
174 views
What is the exact mechanism by which time dilates?
What is the exact mechanism by which time dilates for a fast moving object?
Can the time dilation be explained by any theory other than relativity?
4
votes
1answer
57 views
Relativity of simultaneity - An example
I am trying to understand the relativity of simultaneity in different frames, and I am trying to work out an example.
Suppose along the x-axis there are two points 2000m apart. Event A happens at t=0 ...
1
vote
3answers
87 views
Special Relativity - speed of light question
Just a basic question:
I know that if you are traveling at $x$ speed the time will pass for you slower than to an observer that is relatively stopped. That's all just because a photon released at the ...
2
votes
1answer
67 views
Difference between proper and comoving frames
I'm reading this book "Introduction to Quantum Fields in Classical Backgrounds" by Mukhanov & Winitzki, and there in the chapter 8 "The Unruh Effect" they introduce 3 reference frames.
Laboratory ...
0
votes
0answers
103 views
About the theory of relativity
Why is speed of light constant in every non inertial frame of reference? Is there any theoretical explanation behind this postulate Since we cannot completely depend upon the experimental results?
2
votes
1answer
96 views
Lorentz invariance of the wave equation
I want to show that the 2-d wave equation is invariant under a boost, so, the starting point is the wave equation
$$\frac{\partial^2\phi}{\partial x^2}=\frac{1}{c^2}\frac{\partial^2\phi}{\partial ...
0
votes
2answers
101 views
Inertial Frames of Reference - Description of an Inertial Frame of Reference
An inertial frame of reference is described as being a frame of reference in which the first law of Newton (the law of inertia) holds. This means that all events as described with respect to this ...
-2
votes
1answer
63 views
How would time duration and space distance change when we move in the speed of light? [closed]
It is possible to figure out how time duration and space distance change when we are close to the speed of light - but I am not sure what happens to them if we travel in the speed of light.
2
votes
3answers
182 views
If time slows down when you move faster, does this give you an “effective speed” different from your proper speed?
Suppose you're travelling at 0.9c toward the sun, and you tag past the Earth and start a clock. Would Lorentz contraction/time dilation cause you to get to the sun faster than (about) 9 minutes ...
2
votes
0answers
75 views
Car parking special-relavity puzzle
Hi I read the following puzzle from an old text book long time ago. However it doesn't provide the answer. So what is the solution?
Let's suppose a car is going to park to a garage and the garage is ...
0
votes
1answer
105 views
What is the maximum time dilation between two objects, if one is standing still and the other is moving at $c$?
What is the maximum ratio in the rate of change in time in reference to object $A$ which is standing still and object $B$ which is moving at the speed of light?
1
vote
1answer
171 views
Does the increase of (relativistic) mass, while flying near speed of light, has any impact on astronauts? [duplicate]
Possible Duplicate:
Would travelling at relativistic speeds have any impact on human biology?
I am asking myself this question for a few day. What is the answer on: Does the increase of ...
0
votes
1answer
134 views
Does photon possesses no time to cover any arbitrary distance?
Photon travel 8 minutes (with speed $c$) from the sun to reach the earth. Any particle (or space-ship) with velocity $0.99 c$ covers the same distance (93 millions km) within less than 2 minutes ...
0
votes
1answer
103 views
Scattering Amplitudes in Centre of Mass Frame
I'm reviewing page 59 of the QFT notes here and am a little confused by a reference frame argument. You can compute the second order probability amplitude term for nucleon-nucleon scattering to be
...
0
votes
1answer
196 views
Calculating the speed of an object moving relative to another moving Object (Frame of reference) [duplicate]
Possible Duplicate:
How to deduce the theorem of addition of velocities?
Let's say that you are in a rocket speeding at 90% the speed of light away from Earth. Now fire a bullet inside the ...
1
vote
0answers
61 views
Does Bernoulli's principle hold in moving reference frames? [duplicate]
Possible Duplicate:
Bernoulli’s equation and reference frames
Sometimes in train, when setting behind opening window, I can feel strong gale blowing in. The closer to the window the ...
12
votes
2answers
279 views
What does a sphere moving close to the speed of light look like?
What shape does the viewer in a reference frame with $v=0$ perceive? I suppose that since the sphere moves in one direction only (oX only, not oY) its section would change into an ellipse, where the ...
1
vote
1answer
81 views
Proper times of two observers in a three-torus
Consider two observer in a tree-torus space of size $L$. Observer $A$ is at rest, while observer $B$ moves in the $x$-direction with constant velocity $v$. $A$ and $B$ began at the same event, and ...
2
votes
2answers
78 views
Terminology for opposite null lines
Is there a name for two null lines that lie on the opposite sides of the null cone? Each line can be obtained from the other by reflection in the axis of the null cone (the time-axis). In terms of ...
1
vote
1answer
152 views
4-momentum and an $y$ component of momentum
I have 2 coordinate systems which move along $x,x'$ axis.
I have derived a Lorentz transformation for an $x$ component of momentum, which is one part of an 4-momentum vector $p_\mu$. This is my ...
2
votes
2answers
529 views
Why does an object with higher speed gain more (relativistic) mass?
Today, in my high school physics class, we had an introductory class on electromagnetism. My teacher explained at some point that an object with a very high speed (he said it started to get somewhat ...
1
vote
2answers
169 views
When moving fast Time slows down Vs speeds up
I was watching an old cartoon movie where a scientist makes a gadget, which when bound on the wrist, freezes the movement of the whole world. So, that one may do 100s of things in a single second. ...
2
votes
2answers
122 views
Speed of Entropy change
If time in systems moving with different speed goes differently, does speed of entropy change differ in these systems?
(is "speed of entropy change" a valid term? can we compare them?)
-1
votes
1answer
85 views
Faster than light due to reference position [duplicate]
Possible Duplicate:
Travelling faster than the speed of light
Please try to follow and clarify me I've been curious about this for a long time as it seems a bit paradox due to the rule that ...
0
votes
3answers
149 views
Time slowing down problem
When someone moves, time slows down for him. Let, a man standing still and another moving very very very fast, this happens for an hour (as measured by the standing man). Time has moved slower for the ...
0
votes
1answer
332 views
Two trains at the speed of light [closed]
Okay. Two trains travelling towards each other at the speed of light. So, from one train (let's call it train A), the other is moving towards it at the speed of light. The other train shines a torch. ...
2
votes
2answers
218 views
A relative time dilation paradox.
Let us assume that there are two astronauts A and B who are floating in space. A sees B passing by and vice versa. A sends signals to B every minute. According to A since B is moving his clock will be ...
1
vote
2answers
161 views
Why does the (relativistic) mass change & why?
I studied that when an object moves with a velocity comparable to the velocity of light the (relativistic) mass changes...but I am really eager to know how does this alteration take place....If anyone ...
8
votes
2answers
624 views
Does the speed of light vary in noninertial frames?
The speed of light is the same in all inertial frames.
Does it change from a non-inertial frame to another? Can it be zero?
If it is not constant in non-inertial frames, is it still bounded from ...
3
votes
3answers
193 views
First Postulate of Special Relativity: What does it mean?
Wikipedia has this quote:
Special principle of relativity: If a system of coordinates K is
chosen so that, in relation to it, physical laws hold good in their
simplest form, the same laws hold ...
2
votes
1answer
251 views
Time dilation - why the observers see each other the slow one but then one of them is older or younger?
I'm in trouble with time dilation:
Suppose that there's two people on the Earth (A,B), they are twins and each other has a clock. (So they are at the same reference frame). B travels in a spaceship ...
-1
votes
3answers
166 views
Does the Lorentz transformation not apply to light?
Since you would know that light always travels at the constant velocity with respect to all frame of reference ....according to relativity whenever we are traveling at speed of light our time with ...
-1
votes
1answer
165 views
Time dilation at the speed of light
Does a massless particle travelling at the speed on light in a vacuum (c) experience an infinite time dilation effect?
i.e. Would the time dilation extend from the perspective of the massless ...
6
votes
8answers
2k views
Would time freeze if you can travel at the speed of light?
I read with interest about Einstein's Theory of Relativity and his proposition about the speed of light being the speed limit for anything with mass. So, if I were ...
4
votes
2answers
131 views
Effect of gravity at near-lightspeeds
Let's say I'm in a space station, hurtling towards our galaxy nearly close to the speed of light. From my reference frame, I see the galaxy coming towards my ship at the same speed.
I pass the Sun, ...
0
votes
1answer
125 views
What would happen to electronic circuits when traveling near the speed of light?
Imagine a space ship, loaded with all sorts of computer systems, traveling near the speed of light.
Electricity itself is very fast, and can reach speeds close the speed of light. (up to 99% ...
4
votes
2answers
600 views
How can time be relative?
I don't understand how time can be relative to different observers, and I think my confusion is around how I understand what time is.
I have always been told (and thought) that time is basically a ...
0
votes
1answer
132 views
In What Frame of Reference does the Special Theory of Relativity Operate? [duplicate]
Possible Duplicate:
Time Dilation - How does it know which Frame of Reference to age slower?
This has bugged me for years.
According to the theory of relativity, the faster an object ...
5
votes
1answer
322 views
Einstein's Gedanken Experiment that lead to the Special Theory of Relativity
Once, I read that Einstein founded the special relativity theory by imagining how an observer moves at the speed of light.
How does this thought experiment work? How to reach from this imagination to ...
7
votes
4answers
508 views
Does the “Andromeda Paradox” (Rietdijk–Putnam-Penrose) imply a completely deterministic universe?
Wikipedia article: http://en.wikipedia.org/wiki/Rietdijk–Putnam_argument
Abstract of 1966 Rietdijk paper:
A proof is given that there does not exist an event, that is not already in the past for ...
1
vote
1answer
110 views
How to explain relativistic mass with 2 moving systems, but not 3?
All the visual explanations I know work in some kind of "If you are moving relative to something A, while inside A something is moving, the stuff in A has to move slower due time dilation and ...
11
votes
3answers
320 views
Do particles have different spins in different frames of reference?
Let's say we have two photons, whose momentum vectors point to opposite directions. Also spin angular momentum vectors of the photons point to opposite directions. (Sum of spins is zero)
Now we ...
2
votes
1answer
212 views
Thought experiment about acceleration
Case 1: two people wake up in spaceships accelerating at 1g. They can measure or observe anything inside the room but not outside. They couldn't determine if they were on a spaceship or on earth. ...
0
votes
1answer
334 views
How does time dilation work without a privileged reference frame?
As I understand special relativity, light travels at the same speed in all reference frames.
What I fail to understand is why time dilation would occur in one reference frame, but not by an equal ...
4
votes
5answers
503 views
Time Dilation - How does it know which Frame of Reference to age slower?
Okay, I'm asking a question similar to this one here: Time Dilation - what happens when you bring the observers back together?. Specifically, I am curious about a specific angle on the second part of ...
