The special theory of relativity describes the motion and dynamics of objects moving at significant fractions of the speed of light.
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1answer
376 views
Can relativistic kinetic energy be derived from Newtonian kinetic energy?
Relativistic kinetic energy is usually derived by assuming a scalar quantity is conserved in an elastic collision thought experiment, and deriving the expression for this quantity. To me, it looks ...
3
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2answers
877 views
How to deduce the theorem of addition of velocities?
Lorentz contraction and time dilatation can be deduced without Lorentz transformation. Can you deduce also the theorem of addition of velocities
$$w~=~\dfrac{u+v}{1+uv/c^2}$$
without Lorentz ...
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1answer
124 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% ...
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3answers
173 views
Twin paradox - observers counter orbiting Earth
Imagine three observers - one (A) stationary on the surface of Earth (latitude 0 deg) and two others orbiting the planet in the same circular equatorial orbit just in the opposite direction. When the ...
2
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2answers
312 views
Is the change in kinetic energy of a particle frame independent?
Intuitively, I would expect the change in kinetic energy of a particle to be frame independent. It just doesn't "feel" right that between two points in time-space, one frame should measure a change in ...
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0answers
104 views
special relativity velocity composition [closed]
Can i use proper time in such example ?
IE:
Imagine We have a rocket ''Ra'' moving with respect to earth at 0,8c and a ''Rb'' rocket moving with respect to earth at 0,98c. Rb is following Ra until ...
4
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2answers
588 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 ...
3
votes
2answers
134 views
Does locality emerge from (classical) Lagrangian mechanics?
Consider a (classical) system of several interacting particles. Can it be shown that, if the Lagrangian of such a system is Lorenz invariant, there cannot be any space-like influences between the ...
11
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2answers
598 views
A simple pendulum moving at a relativistic speed - how does the period change?
I've been pondering the precise mechanism of time dilation for the example of a simple pendulum in two different situations:
The observer and ground are at rest in one frame of reference; the ...
4
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3answers
759 views
Is acceleration relative?
A while back in my Dynamics & Relativity lectures my lecturer mentioned that an object need not be accelerating relative to anything - he said it makes sense for an object to just be accelerating. ...
5
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2answers
246 views
Entanglement and relativity
Two observers A and B measure a quantum entangled state and obtain correlated results, even if their separation is space-like (each is out of the light cone of the other). A possible interpretation is ...
0
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1answer
129 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 ...
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1answer
265 views
Special Relativity - Relativistic Dynamics
I've been wrestling with this problem but to no avail. I'm hoping that someone here can give me a little nod in the right direction.
Problem statement:
A thrust-beam space vehicle works bearing a ...
0
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2answers
171 views
faster-than-c photons
As far as I know, according to quantum field theory, there are some photons that go faster than c, which is the speed of light in vacuum.
However, there seems to be a paper and a corresponding ...
5
votes
1answer
315 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 ...
0
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0answers
19 views
Is the universe a quantum computer - is light speed barrier a computational constraint [duplicate]
Possible Duplicate:
Is the universe a quantum computer - is light speed barrier a computational constraint
Cross-posting this question, since physics.stackexchange has not provided any ...
4
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2answers
522 views
Can a static magnetic field turned into a static electric field? or vice versa?
Consider some positive charge that is distributed uniformly over a very long line along the z-axis.
If I am stationary with respect to the line then there is only static electric field which has ...
2
votes
1answer
156 views
Can Mirror box simulate long light travel?
Imagine that there is a cube box that has mirrors all 6 faces in . If we use a strong laser and enter in the box from a small hole on the box. The laser light travels in the box long time that we can ...
12
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3answers
930 views
Is the universe a quantum computer - is light speed barrier a computational constraint
There is currently a debate ongoing on leading maths blog Gödel’s Lost Letter, between Gil Kalai and Aram Harrow, with the former arguing that building a quantum computer may not be possible due to ...
7
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4answers
502 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 ...
3
votes
1answer
331 views
Why can't we make measurements in a photon's rest frame when loop diagrams make measurements possible?
It is one of the axioms of special relativity that the photon has no rest frame; light travels at speed c when measured in any inertial frame of reference. As a corollary, it is often said that if one ...
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2answers
135 views
Pushing with a lorentz contracting stick
If I use a stick to push and accelerate an object, my hand pushes one end of the stick distance $x$, while the other end of the stick pushes the object distance $y$.
Distance $y$ is smaller than ...
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 ...
5
votes
3answers
88 views
Analyticity and Causality in Relativity
A few weeks ago at a conference a speaker I was listening to made a comment to the effect that a function (let's say scalar) cannot be analytic because otherwise it would violate causality. He didn't ...
6
votes
4answers
440 views
The Dual Cloud Chamber Paradox
2012-04-07 Addendum: The Dual Cloud Chamber Paradox
Two 10m diameter spheres $A$ and $B$ of very cold, thin gas have average atomic separations of 1nm. Their atoms are neutral, but ionize easily and ...
1
vote
3answers
271 views
What is the reason behind specific values for charge of electrons, protons?
Why do things like protons and neutrons have specific values. Also speed of light is a speed in which even if you go towards it, the speed does not vary. But why does light have to travel at speed?
4
votes
1answer
289 views
Lorentz force law in Newtonian relativity
I know that in special relativity Electric and Magnetic fields mix together in different reference frames, but my question is about classical mechanics.
It seems weird to me is that the Lorentz Force ...
0
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1answer
133 views
Approximate Time Dilation at Rocket Speeds
How do you calculate the time dilation effect experienced by a traveler traveling at a relatively low speed?
Specifically, how much time dilation would a traveller moving at $v=0.0007 c$ (speed of ...
8
votes
3answers
363 views
Whether $m$ in $E=mc^{2}$ and $F=ma$ are both relativistic mass?
I know that $m$ in $E=mc^{2}$ is the relativistic mass, but can $m$ in $F=ma$ can also be relativistic? If the answer is yes, then can you tell me whether this equation is valid $E=\frac{F}{a}c^{2}$? ...
1
vote
4answers
312 views
The speed of tachyons
The other day I was wondering: When a tachyon is coming towards you faster than the speed of light, will you see it before it hits you? Then I thought of course not, since the light waves aren't ...
1
vote
1answer
282 views
How are fundamental forces transmitted?
How are the fundamental forces transmitted? In particular I wonder, are all "processes" local, i.e. without superluminal distant interactions? But if they are local, then particles would have to ...
4
votes
1answer
131 views
Is radiation pressure constant in this experiment, and does force of a spring change?
Let's say a light clock consists of two parallel mirrors, some photons bouncing between the mirrors, and a spring that pulls the mirrors together with the same force that the photons push them apart.
...
11
votes
3answers
319 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 ...
3
votes
2answers
789 views
If I move a long solid stick can I send message fastest than light? [duplicate]
Possible Duplicate:
Is it possible for information to be transmitted faster than light?
I mean by using a perfect solid stick long enough and moving it forward and backward can I send ...
1
vote
2answers
234 views
Connection between momentum and energy
What is the connection between momentum and energy?
Which of the answers is the correct?
A particle can have zero momentum but energy.
A particle can have zero energy but momentum.
...
2
votes
1answer
211 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. ...
7
votes
2answers
803 views
Relativistic centripetal force
The thought randomly occurred to me that a circular particle accelerator would have to exert a lot of force in order to maintain the curvature of the trajectory. Many accelerators move particles at ...
3
votes
2answers
319 views
Discreteness of Spacetime and Violation of Lorentz symmetry
It is usually said that existence of discrete spacetime violates Lorentz symmetry. What quantity is used to quantify such violation? I mean could someone points a reference for a derivation that shows ...
1
vote
1answer
179 views
Does path integral and loop integral in a Feynman diagram violate special relativity?
Consider a correlation function between two points A(x1,t1) and B(x2,t2), we need to integrate over paths which could be ...
1
vote
0answers
237 views
How equivalent are heat energy and work energy in connection with a spinning flywheel?
Let's say we have two identical spinning flywheels, that have arbitrary geometry, and are made of copper.
Now we apply some heat energy at the center point of flywheel A, causing it to slow down a ...
0
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0answers
63 views
Relativity Scenario [closed]
Does anyone have any ideas about this scenario? I'm having trouble comparing what happens at the different speeds. It has to do with simultaneity
Suppose Al is at rest standing in between two sets ...
1
vote
2answers
248 views
What does a closed time-like curve look like?
I want to see a plot of closed time-like curve in $(t,x)$.
$t$ - vertical axis
$x$ horizontal axis
(the usual setting just neglect $y$ and $z$ components of $(t,x,y,z)$).
What does it look like?
3
votes
5answers
164 views
Will a warm body naturally slowdown?
Suppose a warm body moving in an empty space with high speed.
The body emits radiation based on its temperature. The protons emitted forwards of the body will have higher energy due to Doppler shift ...
-3
votes
2answers
185 views
Why is $c$ considered as the speed of the photons?
Maxwell equations brought $\ c_{o}=\frac{1}{\sqrt{\mu_{o}\varepsilon_{o}}}\ $.
Since this is a constant, it made all physicists at that time wonder where was the frame of reference?
They ended up with ...
3
votes
0answers
41 views
Spectrum of a quantum relativistic “distance squared” operator
This question disusses the same concepts as that question (this time in quantum context). Consider a relativistic system in spacetime dimension $D$. Poincare symmetry yields the conserved charges $M$ ...
1
vote
1answer
415 views
Einstein's Famous Thought Experiment Contradiction
Putting Special Relativity into the General Relativity category as is current practices submerges important aspects of Einstein's 1905 paper, which I recently read in a 1952 Dover paperback (The ...
4
votes
5answers
451 views
What happens to angular momentum when matter is converted to energy?
Let's say a spinning star radiates mass-energy only from it's pole regions. How does the loss of mass-energy effect the angular momentum of the star?
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0answers
38 views
Why has the ether been disregarded as a valid medium through which light can propagate? [duplicate]
Possible Duplicate:
Ether theory acceptance
Although the Einstein's theory of relativity seemed to make the concept of an ether obsolete, did it necessarily invalidate it? Are there any ...
-1
votes
1answer
256 views
Relativity and Entanglement
Say we have two particles which are entangled so that they have opposite spins. If one is up, the other is down. They are sent off to two spatially separated observers A and B. Both observers can ...
5
votes
4answers
515 views
Does the stress-energy tensor contain the equations of motion?
Derivatives $\nabla_i T^{ik}=0$ of a stress-energy tensor of physical system express conservation laws. Whether contains a stress-energy tensor also the information on the equations of motion of ...
