Tagged Questions

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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81 views

How do we measure the range of distant objects despite relativistic effects?

When we observe astronomical objects like distant galaxies there are several complicating factors for estimating the distance: Relativistic speed result in length contraction Relativistic speed ...
1answer
93 views

The status / acceptance of block time?

What is the current status or acceptance of block time as it relates to Einstein's theory of relativity? Has quantum mechanics ruled it out or is it still the favored view of the world? Perhaps there ...
2answers
156 views

Relativity of Simultaneity

Relativity of Simultaneity seems to be about OBSERVING two events simultaneously (please correct me if I am wrong). However, as long as the two events are separated by a distance (any distance) then ...
1answer
91 views

What is Relativistic Navier-Stokes Equation Through Einstein Notation?

Navier-Stokes equation is non-relativistic, what is relativistic Navier-Stokes equation through Einstein notation?
2answers
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Special Theory of relativity on electromagnetic waves

Since time slows down and length contracts, when we travel almost at speed of light, if the speed of light (or EM waves) remains same and the wavelength of light remains same, do we measure the ...
2answers
140 views

Doppler shift of radio signals to an accelerating observer

Suppose a man leaves from Earth to a star which is 1000 light years away. He accelerates to a velocity such that the entire trip lasts a year, from the reference frame of the rocket. Now lets pretend ...
1answer
55 views

Relativistic Computation?

Is it possible to employ relativity to develop computational technology? Here is a really basic example: Build a Computer and Feed it the Problem (say the problem is projected to take 10 years to ...
1answer
46 views

Live feed from a Rocket traveling near the speed of light?

Okay, odd question popped up in my physics class today. If a rocket ship is traveling at .99c for 1 year, and is streaming a video at 30 frames/sec to earth, how would the earth feed be affected? ...
1answer
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if i want action to be positive number then it require that $\tau_i$ be bigger than $\tau_f$, isn't it true? [closed]

the action is the length of the geodesic $S=-E_o\int_i^f d\tau$ we get an action that is minimised for the correct path. if i want action to be positive number then it require that $\tau_i$ be ...
1answer
187 views

drift velocity of electrons in a superconductor

is there a formula for the effective speed of electron currents inside superconductors? The formula for normal conductors is: $$V = \frac{I}{nAq}$$ I wonder if there are any changes to this ...
3answers
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Integration by parts to derive relativistic kinetic energy

I have come across a weird integration during derivation of relativistic kinetic energy. Our professor states that i can get RHS out of LHS using integration by parts:  \int\limits_0^x \! ...
4answers
171 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?
3answers
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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 ...
1answer
58 views

Rate of spontaneous tachyon emission

It's not possible for an electron to emit or absorb a photon without the presence of a third particle such as an atomic nucleus; without the third particle, it's impossible for such a process to ...
2answers
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Faraday tensor, antisymmetric rank two

$F^{\mu \mathcal{V}}$ is defined in http://www.lecture-notes.co.uk/susskind/special-relativity/lecture-7/relativistic-lorentz-force/ How to show that $F^{\mu \mathcal{V}}$$F_{\mu \mathcal{V}}$, is ...
1answer
65 views

Understanding bending light beam perpendicular to motion

I'm just reading a book about gravity. An example it gives is a spaceship accelerating. A beam of light travelling at right angles to the direction of movement of the spaceship enters it via a small ...
3answers
312 views

Can something travel faster than light if it has always been travelling faster than light?

I know there are zillions of questions about faster than light travel, but please hear me out. According to special relativity, it is impossible to accelerate something to the speed of light. However, ...
1answer
44 views

Organic Proliferation In Terms of Speed [closed]

OK for 5 stars...Dealing with Einsteins theory of special relativity: Here is the question: As observed on earth, a certain type of bacterium is known to double in number every 24.0 hours. Two ...
1answer
55 views

Faraday tensor, antisymmetric electromagnetic tensor

I want to write $F^{\mu \nu}F_{\mu \nu}$ in terms of $F_{\mu \nu}F^{\mu \nu}$. How to do it?
3answers
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Having trouble seeing the similarity between these two energy-momentum tensors

Leonard Suskind gives the following formulation of the energy-momentum tensor in his Stanford lectures on GR (#10, I believe): T_{\mu \nu}=\partial_{\mu}\phi \partial_{\nu}\phi-\frac{1}{2}g_{\mu ...
1answer
110 views

Cancelling special & general relativistic effects

We know that for a GPS we need to make a correction for both general and special relativity: general relativity predicts that clocks go slower in a higher gravitational field (the clock aboard a GPS ...
2answers
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What is the process that gives mass to free relativitic particles?

When a free particle move in space with a known momentum and energy then what is the physical process that gives mass to that free (relativistic) particle? What is role does the Higgs field in that ...
1answer
28 views

If there's a light ray and it's turned to a new location by a certain angle

Imagine that there's a light ray, with source at point A, and it's directed towards point B (which is very far from point A) and it continues for a huge distance. How will an observer at point B ...
2answers
108 views

Relativistic Doppler effect derivation

This is about a step in a derivation of the expression for the relativistic Doppler effect. Consider a source receding from an observer at a velocity $v$ along the line joining the two. Light is ...
2answers
112 views

Does an accelerating spaceship move backwards due to length contraction?

Let's assume I have a spaceship in front of me let's say at 1000000km distance. Now let's assume I have also a stationary wall just behind the spaceship at 999999km. Initially the spaceship's speed is ...
1answer
93 views

Proton-proton collisions

I have a question about proton-proton collisions at the LHC. Firstly, the 4-momentum $p^\mu=(E/c,\vec{p})$ can be represented as \$p^\mu =(m_T \cosh \Psi, p_T \cos \phi , p_T \sin \phi, m_T c \sinh ...
0answers
38 views

Relativistic solution for Zeno's stadium paradox?

The stadium Zeno paradox (not the same paradox from the Quantum-Zeno-Effect, but the same Zeno) gives a paradox about time, when two runners move toward a standing person from different directions. ...
3answers
388 views

Does entanglement not immediately contradict the theory of special relativity?

Does entanglement not immediately contradict the theory of special relativity? Why are people still so convinced nothing can travel faster than light when we are perfectly aware of something that ...
1answer
61 views

$\frac{dt}{d\tau}=\gamma$ in special relativity

I hope this is not too silly a question: We often see $$\frac{dt}{d\tau}=\gamma=\frac{1}{\sqrt{1-v^2}},$$ taking $c=1$. Problem: I don't understand why... In the Minkowski metric, using the ...
1answer
36 views

Field Tensor and classical limits

I would be very grateful if someone would kindly explain this generalization of the Lorentz force law to the special relativity domain. Please bear with me. Classically, the Lorentz force law is ...
4answers
2k views

How is the classical twin paradox resolved?

I read a lot about the classical twin paradox recently. What confuses me is that some authors claim that it can be resolved within SRT, others say that you need GRT. Now, what is true (and why)?
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Relativistic interaction: gamma + proton = delta

We have a proton at rest, and there's an incident photon that is absorbed by the proton producing the excited state "delta". Photon energy: $\hbar \omega$, Proton rest Energy: $m_p c^2$, Delta rest ...
0answers
60 views

Consequences of Third Postulate of Special Relativity [closed]

Consequences of SR arise from two postulates. know as this abstract states: "relativistic action is limited to planck's constant", and maybe we've to consider it as the possible third postulate of ...
1answer
40 views

Wavefront emitted by bodies at traveling near the velocity of light

I studied that no body can travel with the velocity of light. But, assuming that when a body moves nearly velocity of light, will it obey length contraction law of Einstein or will it emit the same ...
1answer
56 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 ...
10answers
6k views

Does the Pauli exclusion principle instantaneously affect distant electrons?

According to Brian Cox in his A night with the Stars lecture$^1$, the Pauli exclusion principle means that no electron in the universe can have the same energy state as any other electron in the ...
2answers
109 views

Can dark matter be relativistic dust?

As far as I know the mass of an observed object increases as it approaches the speed of light. Is it possible that the excess mass called "dark matter" is due to relativistic dust? Surely, stars ...
2answers
118 views

Do objects have energy because of their charge?

My gut feeling tells me things should have energy because of their charge, like they have energy because of their mass. Is this possible? Has it been shown? If not then what is missing to make such ...
3answers
154 views

Is there absolute proof that an object cannot exceed the speed of light?

Have any known experiments ruled out travelling faster than the speed of light? Or is this just a widely accepted theory?
3answers
145 views

What truly is mass, and is there a direct way to measure it?

We know a mass of an object of one kilogram as an object that weighs W = mg = 9.8 N and we reference it to that, (when it should as a fundamental parameter describe weight not the opposite). But if we ...
2answers
66 views

Can acceleration feel like constant gravity for indefinitely long?

So here's the setup: I'm in a spaceship, without windows as always, and the ship is accelerating upwards at a constant rate of $1\,\text{g}$. So inside the spaceship it feels like I'm being pulled ...
1answer
85 views

The Klein–Gordon equation

As we know that the Schrödinger equation presents basis of Quantum Mechanics and analogy with Newton second law in Classical Mechanics, I thought that relativistic interpretation of Schrödinger ...
2answers
158 views

Has anyone ever measured the one way speed of light perpendicular to the Earth at the Earth's surface?

1 - Has anyone ever measured the one way speed of photons traveling perpendicular to the Earth at the Earth's surface? 2 - Given our current understanding of Physics is there any way both the upward ...
1answer
110 views

Lorentz invariance of positive energy solutions to the Klein-Gordon equation

I am reading Arthur Jaffe's Introduction to Quantum Field Theory. (You can find it here.) There is an interesting question posed in Exercise 2.5.1: Solutions to the Klein-Gordon equation propagate ...
2answers
155 views

Relativistic equivalent of a spring-force?

Usually what helps me understand a concept better in physics is to write a simulation of it. I've got to the point where I'm competent in the basics of special relativity, but, I can't figure out how ...
5answers
420 views

Special Relativity Second Postulate

That the speed of light is constant for all inertial frames is the second postulate of special relativity but this does not means that nothing can travel faster than light. so is it possible the ...
3answers
505 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 ...
2answers
71 views

How does the wavelength change in relativistic limit?

In the text, it reads that the momentum of a particle will change if it is moving at speed close to light speed. In the general case, the wavelength is given as $$\lambda = \frac{h}{p}$$ and p ...
1answer
68 views

Properties of the Faraday tensor for constant fields

I'm doing a special relativity past exam paper and have got caught up with something that I hope someone can help me with! I have to show that for constant fields, the magnitude of A, the ...
2answers
118 views

Lorentz boost matrix for an arbitrary direction in terms of rapidity

We have derived the Lorentz boost matrix for a boost in the x-direction in class, in terms of rapidity which from Wikipedia is: Assume boost is along a direction \$\hat{n}=n_x \hat{i}+n_y \hat{j}+n_z ...
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