The special theory of relativity describes the motion and dynamics of objects moving at significant fractions of the speed of light.

learn more… | top users | synonyms (3)

7
votes
1answer
524 views

Can a black hole form due to Lorentz contraction? [duplicate]

Possible Duplicate: If a 1kg mass was accelerated close to the speed of light would it turn into a black hole? Imagine, a rod of length L is moving with velocity approaching the speed of ...
4
votes
2answers
671 views

Does the mass of a body absorbing photons increase?

Let's say I have a photon collector in orbit around the sun. It manages to collect photons perfectly efficiently, that is, without radiating off any energy. Then, using Einstein's equation: $$E = m ...
0
votes
0answers
60 views

Taylor approximation of e(v) [closed]

Relativistic mass $\displaystyle m(v)=\frac{m_o}{\sqrt{(1-(v/c)^2}}$ $m_o$ = mass of object measured at rest $c$ = speed of light ($3\times 10^8\;m/s$) $v$ = speed If the total relativistic energy ...
2
votes
1answer
517 views

Conservation of Energy in Special Relativity

In classical Newtonian mechanics, from what I understand, conservation of energy stems from the fact that all known forces are conservative forces, and vector calculus tells us that they can be ...
16
votes
5answers
578 views

Are gravitomagnetic monopoles hypothesized?

My understanding is that gravitomagnetism is essentially the same relativistic effect as magnetism. If so, why is it that I've heard so much about magnetic monopoles, but never gravitomagnetic ...
0
votes
2answers
208 views

Behavior of shock waves at relativistic speeds

Suppose I am in a spaceship traveling inertially at a velocity $v$ that is of the same order as $c$. As I pass by a metal bar that is oriented parallel to $v$, someone hits it with another metal bar, ...
-1
votes
1answer
216 views

Will a black hole increase the speed of sound above the speed of light in this medium

For the sake of this question we are inside the EH and a sound wave enters from our perspective as the sound moves closer to us at the EH would it speed up. Specifically how would the extreme ...
8
votes
3answers
2k views

Is a photon “fixed in spacetime”?

From what I've read, according to relativity, a photon does not "experience" the passage of time. (Can we say there is no past/present/future for a photon?) Would it be better to say a photon is ...
4
votes
2answers
148 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, ...
2
votes
0answers
111 views

Does the passage of time effect a photons entanglement with another?

I recently read an article about "Delayed-choice entanglement swapping". Here is an excerpt from the article: Delayed-choice entanglement swapping consists of the following steps. (I use the ...
0
votes
0answers
183 views

Comparing Lagrangian in Special Relativity vs General Relativity for a weak gravitational field

This is a sequel to this question. Who knows a difference between the Lagrangian in SR and GR for a weak gravitational field in non-relativistic case? What is the reason of this difference?
1
vote
1answer
86 views

Perpendicular Fields and Equations of Motion [closed]

I have the following problem to solve: A particle of mass $m$ and charge $e$ moves in the laboratory in crossed, static, uniform, electric and magnetic fields. $\mathbf{E}$ is parallel to the ...
2
votes
2answers
195 views

Which new insight did $E=mc^2$ give us?

I had a special relativity course at university. Now I'm trying to extract what new insight $E=mc^2$ did give us. I mean that moving mass has/is energy (kinetic) not new. The energy merely changed ...
2
votes
2answers
596 views

Calculate relativistic boost to COM frame from two arbitary velocities?

Looking in Goldstein's book, there doesn't seem to be a standard formula to calculate the COM frame velocity for two particles, from their relativistic velocities in the lab frame, although it is done ...
0
votes
1answer
161 views

Factor 2 and equations for the weak gravitational field

By using some axioms people derives equation for Lorentz force and, then, Maxwell's equations from the Coulomb's law and Lorentz transformations. When I used analogical methodology for Newton's law of ...
2
votes
2answers
451 views

What is the displacement of an accelerated and relativistic object?

Displacement in an accelerated classical object is: $$s=ut+\frac {at^2}{2}$$ What is the displacement of an accelerated relativistic object? In Newtonian mechanics there are two types of ...
7
votes
2answers
1k views

The equivalent electric field of a magnetic field

I know that Lorentz force for a charge $q$, with velocity $\vec{v}$ in magnetic field $\vec{B}$ is given by $$\vec{F} =q \vec{v} \times \vec{B}$$ but there will exist a frame of reference where ...
6
votes
3answers
746 views

Special Relativity and $E = mc^2$

I read somewhere that $E=mc^2$ shows that if something was to travel faster than the speed of light then they would have infinite mass and would have used infinite energy. How does the equation show ...
3
votes
2answers
537 views

Spin matrices in Dirac equation

Why in every textbook when deriving Dirac's equation the smallest possible matrices ($2 \times 2$) are used? I wonder why one couldn't use spin 1 matrices ($3 \times 3$) and get relativistic equation ...
3
votes
1answer
593 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 ...
7
votes
2answers
2k 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 ...
0
votes
1answer
180 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
3answers
242 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 ...
7
votes
1answer
388 views

Spin-Statistics Theorem (SST)

Please can you help me understand the Spin-Statistics Theorem (SST)? How can I prove it from a QFT point of view? How rigorous one can get? Pauli's proof is in the case of non-interacting fields, how ...
2
votes
2answers
557 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 ...
8
votes
2answers
3k 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
154 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 ...
12
votes
2answers
951 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 ...
6
votes
4answers
2k 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. ...
6
votes
2answers
402 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
votes
1answer
237 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 ...
0
votes
1answer
370 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
votes
3answers
266 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
2answers
854 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
votes
0answers
37 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
votes
2answers
1k 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
251 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 ...
18
votes
3answers
2k 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
votes
4answers
842 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 ...
4
votes
1answer
825 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 ...
0
votes
2answers
164 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
158 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
184 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
593 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 ...
8
votes
1answer
573 views

Identification of the state of particle types with representations of Poincare group

In the second chapter of the first volume of his books on QFT, Weinberg writes in the last paragraph of page 63: In general, it may be possible by using suitable linear combinations of the ...
1
vote
3answers
440 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?
5
votes
1answer
423 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
votes
1answer
202 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
428 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
547 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 ...