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
267 views
Do the particles that were found to break the speed of light really break Einstein's theory of relativity? [duplicate]
Possible Duplicate:
What would be the effects on theoretical physics if neutrinos go faster than light?
Update: Loose cable caused faulty results
Apparently, researchers at CERN have found ...
3
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2answers
557 views
Does a photon see a 0-D universe?
For a massless particle the spacetime interval between its point of emission and point of absorption is zero: the two points coincide. From the vantage point of such a particle space-time has reduced ...
11
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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 ...
1
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2answers
235 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.
...
1
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1answer
418 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 ...
2
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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. ...
7
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2answers
809 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 ...
1
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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
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0answers
239 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 ...
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2answers
271 views
Momentum Energy and Higgs
So, as an object accelerates it gains energy. And energy is mass. So an object becomes more massive as it approaches the speed of light.
But, if mass is ONLY due to an object's interaction with the ...
4
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5answers
452 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?
1
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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?
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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 ...
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 ...
5
votes
4answers
518 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 ...
0
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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 ...
2
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1answer
286 views
Einstein Relative Motion and Time Order of Events
According to Einstein, do observers in relative motion agree on the time order of all events?
I don't think they would agree on the timing of events, but I am having trouble figuring out why they ...
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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 ...
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4answers
263 views
Is there a universal rest frame of reference?
I am still struggling with C being a constant and what that implies.
So can an experiment be done to find the resting state for the universe?
Take a device with an observer and a light source and two ...
2
votes
2answers
345 views
Time dilation as an observer in special relativity
I've been having a discussion regarding time dilation relating to special relativity and how it should be observed from the FoR (Frame of Reference) of "the person moving" :
I assert- If we have a ...
-2
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2answers
122 views
frames of reference [duplicate]
Possible Duplicate:
Help Me Gain an Intuitive Understanding of Lorentz Contraction
Frames k and k' are inertial frames. Frame k' is moving at a velocity of magnitude v relative to frame k ...
2
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4answers
395 views
How is this classical “paradox” resolved in electromagnetism?
A magnet and a coil move relative to each other. In the frame of reference of the magnet, there is a magnetic field and consequently a force acting on the charges in the coil according to the Lorentz ...
1
vote
1answer
116 views
Do we need a quantum theory of gravity in order to describe photons blueshifted past planck energy?
If yes, then how does this accord with relativity: the laws of physics are the same in all reference frames? We can move from a reference frame in which the photon has near zero energy density, to a ...
2
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1answer
148 views
What would an observer see if he/she flew toward a clock at relativistic speeds?
If an observer approaches a clock at a significant fraction of the speed of light, would they see the clock's hands moving at a faster or slower than usual rate?
I figure there are two competing ...
3
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3answers
143 views
How Relative Is Relativity With Respect To Visual Effects?
This might seem naive, but here goes.
Imagine Albert and Rick, of equal mass, accelerate together to a significant fraction of light-speed (call it v) relative to Earth, enough to clearly see the ...
2
votes
3answers
364 views
If it turns out that neutrinos do travel at faster than lightspeed, how will the success of special relativity be explained?
As per in the title. If it turns out that neutrinos do travel faster than the speed of light, how will the success of special relativity be explained? My apologies if this has been asked before; I've ...
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2answers
150 views
Does a Lorentz-contracted object float or sink?
Consider the following thought experiment:
Imagine an object of a certain mass density which allows it to float in water.
Now if this object is viewed from a moving frame with high speed, it will ...
2
votes
1answer
206 views
What is the mass of a photon in non-empty spaces?
It is a well known result of the special theory of relativity that the photon has no rest mass, because for a particle to attain the speed of light, it must have zero rest-mass. I will not dig into ...
2
votes
1answer
105 views
Can non-free forces change the rest mass?
While reading Hobsen et al.'s "General Relativity: An Introduction for Physicists", I came across a bit confusing derivation. Multiplying the 4-force and 4-velocity, the following derivation can be ...
12
votes
3answers
861 views
Why the vacuum polarization does not decrease the speed of light?
On one hand, in the classical electrodynamics polarization of transparent media yields in lowering the speed of light by the factor of $n=\sqrt{\epsilon_r \mu_r}$ (refractive index).
On the other, in ...
1
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0answers
2k views
Kinetic energy of Electron [closed]
I had to find the kinetic energy of electron with wavelength $2$ pm. I used the formula
$$ KE = \frac{p^2}{2m} = \frac{h^2}{\lambda^2 2m}$$
which gave me result, $KE = 376.9$ KeV. But the answer ...
2
votes
4answers
315 views
Reducing General Relativity to Special Relativity in limiting case
I understand that general relativity is applicable to gravitational fields and special relativity is applicable to case when there is no gravity. But is there a derivation on how to reduce General ...
2
votes
2answers
206 views
Confused on newton's second law being invariant under relaitivity
I am a math student with some interests in physics. I picked up a book called "A First Course in General Relativity", and I am confused on the second page. I am assuming by notation or convention.
...
1
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2answers
136 views
What will happen if we use a speed greater than light speed and find a body'motion and energy relative to it?
In Einstein's papers, he used light speed as a reference speed. What if we use a greater finite speed and do the same calculations. Won't this greater speed then be the limit.
2
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2answers
267 views
How to measure faster than light electric energy?
According to relativity,nothing can break light barrier.But a recent preprint shows energy transmission of commercial electric power (f=60Hz) is faster than light. (It is not the drift velocity of ...
1
vote
4answers
510 views
Is This The Answer To Artificial Gravity?
Einstein teaches that as an object gets faster, its relativistic mass increases...
Newton teaches that as an object's mass increases, so does it's gravitational pull...
So... if you a tethered some ...
5
votes
2answers
228 views
what is the kinematics of a particle with complex mass?
particles with real-mass have time-like kinematics ($ds^2 > 0$).
particles with zero-mass have light-like kinematics ($ds^2 = 0$).
particles with imaginary-mass have space-like kinematics ($ds^2 < ...
6
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2answers
503 views
Tachyon and Photons
Is there a particle called "tachyons" that can travel faster than light? If so, would Einstein's relativity be wrong? According to Einstein no particle can travel faster than light.
0
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0answers
58 views
Which velocity must a particle achieve to triple the relativistic mass of an idle particle [closed]
We have this question in our homework. I have the solution, but I don't know how to get to it. So, I was hoping some of you could shed some light on it.
Solution: $$\frac{2\sqrt{2}}{3}c$$
Thanks in ...
2
votes
1answer
241 views
Paradox of the Relativistic Record Player [duplicate]
Possible Duplicate:
Invariant spacetime - distance - Circular Motion
This is a question that I thought up a few years ago when I was taking mechanics. I asked the professor but didn't ...
2
votes
1answer
165 views
Motion is relative, right? And most pop sci relativity explanations are somewhat incorrect?
On page 20 of A Brief History of Time:
. . . all observers should measure the same speed of light, no matter
how fast they are moving.
But in an observer's frame of reference, they're actually ...
10
votes
5answers
106 views
How large is the universe?
We know that the age of the universe (or, at least the time since the Big Bang) is roughly 13.75 billion years. I have heard that the size of the universe is much larger than what we can see, in other ...
1
vote
1answer
156 views
Measuring a Rod in Motion with two Synchronized Clocks
An explanation of special relativity I'm struggling with, goes like this:
A rod traveling by a "stationary" observer has its length measured by use of two stationary synchronized clocks (synchronized ...
6
votes
4answers
259 views
Velocity Time Dilation
In Wikipedia article about time dilation, it says:
"Hafele and Keating, in 1971, flew caesium atomic clocks east and west around the Earth in commercial airliners...the moving clocks were expected ...
1
vote
1answer
184 views
Knowing the mass and force acting on a particle, how do we derive the relativistic function for velocity with respect to time?
Use this scenario:
An electron gains speed in the Stanford Linear Accelerator (SLA) across 3000 meters, reaching a final velocity of 0.95c due to a constant force pushing on the electron. Given the ...
3
votes
1answer
188 views
Some questions about the logics of the principles of independence of motion and composition of motion
In high-school level textbooks* one encounters often the principles of independence of motion and that of composition (or superpositions) of motions. In this context this is used as "independence of ...
1
vote
6answers
2k views
Did Einstein prove $E=mc^2$ correctly? [closed]
In his book "Einstein's mistakes" H. C. Ohanian, the author, holds that Einstein delivered 7 proofs for $E=mc^2$ in his life that all were in some way incorrect. This despite the fact that correct ...
15
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2answers
1k views
What happened to the idea of tachyonic or other superluminal neutrinos?
While hunting around for information about the recent OPERA measurement that hints at superluminal neutrinos, I discovered that this idea was actually considered back in the 1980s. Wikipedia lists as ...
-5
votes
1answer
174 views
$E=mc^2$ why is it $c^2$ and not just $c$?
Why is constant for the conversion of mass to energy square of the ligths speed? is it bedside it's the fastest real matter?
1
vote
1answer
116 views
Violation of Lorentz symmetry on cosmological distances
This question is about the domain of validity of Lorentz symmetry.
As far as I know, general relativity is a generalization of special relativity. Does that mean that Lorentz symmetry is violated on ...
