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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3answers
517 views

Why does nonlinearity in quantum mechanics lead to superluminal signaling?

I recently came across two nice papers on the foundations of quantum mechancis, Aaronson 2004 and Hardy 2001. Aaronson makes the statement, which was new to me, that nonlinearity in QM leads to ...
5
votes
2answers
771 views

Why do we say that irreducible representation of Poincare group represents the one-particle state?

Only because Rep is unitary, so saves positive-definite norm (for possibility density), Casimir operators of the group have eigenvalues $m^{2}$ and $m^2s(s + 1)$, so characterizes mass and spin, and ...
2
votes
2answers
839 views

What would earth look like if traveling at 77% the speed of light?

I've been having a bit of trouble wrapping my mind around this. If I were in a ship going 77% the speed of light (enough to experience reasonable time dilation) would I see earth going in fast ...
16
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4answers
998 views

How would we see a near-lightspeed object emitting light?

Consider an object travelling near the speed of light relative to us (let it be a spaceship or a star), which is emitting light (consider it monochromatic resulting from a two level electronic ...
0
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1answer
159 views

Moving electron - finding the wavefunction

On our modern physics class my professor did a problem: Write down a wavefunction of an electron which is moving from left to right and has an energy $100\text{ eV}$. At first i said: "Oh i know ...
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2answers
288 views

Why does the guy moving on spaceship look younger in twin paradox?

If there is no particular absolute choice of frame of reference, the guy who sits on Earth is also moving away from the guy on spaceship perspective and hence time on Earth should also dilate when ...
3
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2answers
366 views

Imaginary time?

If we begin with the equation for time dilation: $$ \Delta t^\prime = \frac{\Delta t}{\sqrt{1-\frac{v^2}{c^2}}} $$ Now, for a particle moving in space with no potential energy, $$ E = \frac{1}{2} ...
3
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1answer
239 views

Photon mass and life time

In this article, the author tried to explain that, Einstein's theory may not valid because he says "photon can decay because it may have minute amount of mass". I'm totally in a conundrum state that ...
2
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1answer
590 views

Can we live forever by taking advantage of the time dilation effect?

I have been reading about Time dilation and twin paradox in Relativity. So,I thought that if It can be the difference of 10 yrs between the Girl in space and on Earth, then why can't anyone not age ...
0
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2answers
330 views

Relativity - Lorentz transformation

Can someone show me how the Lorentz transformation can be derived from the metric equation: $s^2=c^2t^2-x^2$
0
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0answers
62 views

relativity - equivalent frames do not have equivalent clocks and rods

In problems about relativity we have a stationary frame S and a moving frame M and two observers initially at the same reference point. Then the two frames pass each other and we measure the distance ...
0
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1answer
107 views

An electron emits a photon and the core is pushed (recoiled) back!

I have come across a problem which is a homework indeed, but i tried to pack this question up so that it is more theoretical. What I want to know is: If I am allowed to write energy conservation for ...
0
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0answers
91 views

accelerating a gravitational field

Newton's equation for gravity calculates gravitational force between two bodies $F= GMm/r^2$ My question is: How does the force change as these two bodies accelerate together through the universe and ...
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9answers
4k views

If an event happens 10 light years away and we observe it here, did it actually happen 10 years ago?

I'm sorry if this question has been answered a squillion times, I need someone with smarts to explain it to me. If an event happens 10 light years away, and we observe it here, did it actually happen ...
-1
votes
1answer
177 views

Could time be changing without us knowing? [closed]

I've been wondering about relativity for a while now. We seem to measure time by using the speed of light. Light can be slowed down or stopped We assume light doesn't change in a vacuum - yet, how ...
-1
votes
1answer
82 views

Mass is a stuff or not? [closed]

Einstein said, there can be no clear definition can be give for moving body mass – instead of giving its name as “rest mass”, it is better to mention, “momentum and energy”. Matter is a stuff, ...
2
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0answers
157 views

Charge above a conductor; effects due to Lorentz force law for moving charges

Currently working through a practice preliminary examination problem. I have your standard charge situated a distance d from a infinite conductor(lets say in the $\hat{z}$ direction and neglecting ...
2
votes
1answer
228 views

Can relativistic energy transformation be explained by time dilation and E=h f?

Can one explain the relativistic energy transformation formula: $$E = \gamma\ E',$$ where the primed frame has a velocity $v$ relative to the unprimed frame, in terms of relativistic time dilation ...
0
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0answers
68 views

Where does the transformation of $\gamma$ come from?

I was reading Tipler, and in his book he says that in order to transform energy, we must write gamma in terms of quantities in the non-primed frame. However his derivation makes no sense to me, it's ...
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3answers
178 views

Is it possible to defy time using speed? [closed]

I have always wondered if we were to travel at past the speed of light (even beyond the current capability) would we be able to slow down time around us? I have asked my teacher at school and he has ...
1
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1answer
576 views

Relativistic corrections to classical physics formulae

How are classical formulas in physics (such as p = mv, or kinetic energy, or maxwell distribution of speeds) treated with the appropriate relativistic correction/modification? Is it done by using the ...
0
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1answer
191 views

Lorentz Transformation

I have specific questions about Lorentz transformations specifically about length contraction. Why does length contraction only occur in the direction of travel, (not in all directions) when ...
0
votes
1answer
260 views

Ultrarelativitistic particle - what kind of a particle is this?

I have heard many times that we can treat a moving particle as a: classical particle non-relativistic relativistic particle ultra-relativistic particle While I know equations for 1, 2, & 3, I ...
0
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1answer
148 views

The Movement of Light

I've asked several other questions like this, and I know it's a dumb question but I really can't understand. When light is emitted from a moving source, it still moves straight in that source's frame. ...
3
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3answers
525 views

How can we deduce the relation $m = \frac{m_0}{\sqrt{1-\frac{v^2}{c^2}}}$ between relativistic mass and rest mass in special relativity? [duplicate]

I was watching a video on Youtube which deduce Einstein's relation $E=mc^2$ and the process of deduction used the relation between relativistic mass and rest mass, which is $$m= ...
4
votes
1answer
121 views

Can we obtain non-Lorentzian metric from Lorentzian metric, through renormalization methods?

Since low-energy, non-relativistic thermal field theories are defined in Euclidean spacetime, while high-energy relativistic theories are define in Minkowski spacetime, I was wondering if there are ...
1
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1answer
139 views

Accelerated Light Sources

When someone accelerates towards a light source, how does the light that's radiating off from it look? I suppose in an inertial frame, all the light should be moving off straight from the source, but ...
2
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1answer
199 views

From the Poincare group to Minkowski space

In special relativity one assume that spacetime can be locally described by 4 coordinates, so it makes sense to model it as a 4-dimensional manifold. I had the impression that it is assumed that ...
-5
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1answer
86 views

What is the term $t$, in the expression $E=t^{0}m^{1}c^{2}$? [closed]

$E=(t)^{0}(m)^{1}(c)^{2}$. Here, $m$ = mass of the body. $c$ = velocity of light. Is $t$ the time?
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1answer
264 views

Describing the path of light from a moving source with waves [closed]

Can anyone explain the path of light to me, using a wave model, that show the angled path in different reference frames?
2
votes
2answers
522 views

2 protons collision (both with different kinetic energies) - I don't know what to put in for $p^2c^2$

The problem statement: Two protons with kinetic energies $W_{k1}=4GeV$ and $W_{k2}=2GeV$ colide and form new particles. What is the mass of newly born particles? There are as many as possible ...
2
votes
2answers
221 views

Light in Different Reference Frames

I think I'm just confused, but for some reason I thought that light moving straight in one frame would have to move in the same direction in another frame. I know there are photons-but because I have ...
6
votes
4answers
2k views

Relativity and Current in Wire

If an observer is stationary relative to a current-carrying wire in which electrons are moving, why does the observer measure the density of moving electrons to be the same as the density of electrons ...
3
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0answers
477 views

The connection between classical and quantum spins

I have two questions, which are connected with each other. The first question. In a classical relativistic (SRT) case for one particle can be defined (in a reason of "antisymmetric" nature of ...
0
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1answer
72 views

Measurement of event time by different observers

Follow up question to Doppler redshift in special relativity A source of light pulses moves with speed v directly away from an observer at rest in an inertial frame. How will the time of the emission ...
0
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1answer
46 views

Are these data enough to solve this simulataneity problem

observers: S and S'. S stands in midway between two events (say, 2 flashes) located 20 metres apart. He sees two flashes occurring simultaneously. S' notes a 20ns difference in them. S' is moving ...
7
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5answers
2k views

Can one create mass from energy?

Due to $ E =m c^2 $, one can convert mass to energy. A classic example would be matter/anti-matter annihilation to produce energy (photons, etc.). Can one do the reverse? So could one do something to ...
5
votes
2answers
699 views

The problem of a relativistic path integral

Many books have described the path integral for non-relativistic quantum. For example, how to get the Schrödinger equation from the path integral. But no one told us the relativistic version. In fact, ...
0
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1answer
174 views

Can inertial mass affect gravity of the object? [duplicate]

Every time I watch this TV program that discusses about all the facts about the universe , and it came to a point where they said that as an object approaches the speed of light the mass of the object ...
1
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2answers
382 views

If two observers pass each other in opposite directions at $.5c$ what would effect on each others clocks be?

Assume an alternate universe with same physical laws as here. In this universe nothing exists except 3 observers, each in a transparent box with a clock. Observer A is travelling at .5c. Observer C is ...
4
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1answer
126 views

Original paper on Lorentz representation theory

Which was the original paper on the representations of the Lorentz group? Is there even one paper on this, or was this knowledge gained iteratively in a series of papers?
-2
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1answer
137 views

Time relative to pressure? [closed]

We all know the effects of speed on time, and we have a formula for that, but I have a hunch, that time also is relative to pressure, and that by increasing the pressure on matter, in fact time will ...
0
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0answers
492 views

Collision of 2 particles - calculating the mass and a speed after the collision

Lets say we have a particle of mass $m_1$ which has a kinetic energy $W_{k1}$. This particle collides with another same particle. How can i calculate mass $m_2$ and the speed $v_2$ of the particle ...
1
vote
1answer
130 views

Are there (or could there be) electrically charged particles that move at the speed $c$? [duplicate]

A photon, a neutrino (if it has zero rest mass) move at $c$ but what about charged particles? If the answer is no, is there a fundamental reason or just because of the radiation it emits?
2
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0answers
65 views

Manipulating a formula for a relativistic Doppler shift

Lets say we take the standard configuration when $x'y'$ is moving away from system $xy$ (image 1). By knowing that the phase is constant in all frames $\phi=\phi'$ we can derive the Lorenz ...
3
votes
1answer
223 views

How can “quantum particles have positive masses, even though the classical waves travel at the speed of light”?

Clay Mathematics Institute writes about the Yang-Mills and mass gap problem on this page http://www.claymath.org/millennium/Yang-Mills_Theory/: The successful use of Yang-Mills theory to describe ...
3
votes
1answer
183 views

nuclear physics homework

i have a homework in our nuclear physics class. the question is "An astronaut whose height in the earth is exactly 6ft is lying parallel to the axis of a spacecraft moving at a 0.9C relative to the ...
0
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3answers
161 views

Homework - length contraction ($\gamma$ and $u$ are unknown)

I am very sorry for posting these problems in this forum, but i don't know where to post otherwise... I have a weird special relativity problem where i get a relative speed $u$ which is larger that ...
5
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3answers
724 views

Potential energy in Special Relativity

In Special Relativity, the energy of a free particle is $E^2=p^2c^2+m^2c^4$. But what would be the energy when there is potential energy? If it's something like $E=\sqrt{p^2c^2+m^2c^4}+U$, what ...
2
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2answers
202 views

How much faster would a Clock without gravity run?

Pardon the misleading title. It is to my understanding that moving/heavy clocks run slow. The Earth itself is under gravitational influence from many sources, and is moving. Is there a way to know ...