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 (5)

2
votes
3answers
254 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 ...
1
vote
2answers
192 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
301 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 ...
3
votes
3answers
163 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
1answer
259 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 ...
3
votes
1answer
419 views

The Particle-Antiparticle Problem in Relation to Special Relativity

Prelude: Let’s consider a pair of events $A(t_1,x_1)$ and $B(t_2,x_2)$,having a spacelike separation wrt an inertial frame denoted by K.In the frame K’ moving along the positive x-x’ direction with a ...
1
vote
0answers
4k 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
2answers
308 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. ...
2
votes
4answers
680 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 ...
1
vote
2answers
199 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
votes
2answers
1k views

How does time dilation work without a privileged reference frame?

As I understand special relativity, light travels at the same speed in all reference frames. What I fail to understand is why time dilation would occur in one reference frame, but not by an equal ...
19
votes
10answers
12k 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 ...
2
votes
1answer
177 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 ...
0
votes
2answers
378 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 ...
1
vote
1answer
393 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 ...
4
votes
1answer
428 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 ...
5
votes
3answers
439 views

How can we know, today, that there's something from 100 light-years from here?

In my understanding, to take a picture of something that is 100 light-years from here, our "camera" would have to travel 100 years at light speed, take the picture, send to us, and 100 years later we ...
4
votes
4answers
4k views

That 10km/day error predicted if GPS satellite clocks not corrected for relativity

Some authorities have stated publicly and without explanation that if the theories of Special and General Relativity were not taken into account in the design of the GPS (by building the satellite ...
6
votes
4answers
407 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 ...
-4
votes
1answer
215 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? .
2
votes
1answer
180 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 ...
2
votes
2answers
239 views

Relativistic transformation of the wave packet length

Let us suppose we have an excited atom at rest. It has a certain mean lifetime $\tau_0$. If we wait sufficiently long time $t>>\tau_0$, we will find a deactivated atom and a (spherical) ...
0
votes
1answer
103 views

A possible absolute reference system

What about considering the microwave background radiation (2.7K if I remember well) as a reference system with some absolute character? Please explains if this question make sense and possible ...
1
vote
2answers
536 views

A Paradox in Special Relativity

Two inertial frames K and k’ are considered. They are in relative uniform motion along the x-x’ direction with relative speed =v. In the frame K’ we have a cuboidal piece of dielectric [at rest wrt ...
1
vote
2answers
228 views

The time component is $\gamma m c$, so shouldn't $E=mc$?

Basically, the book is Brian Cox's Why Does $E=mc^2$?: (And Why Should We Care?). I just finished Chapter 5, where we derived the spacetime momentum vector (energy-momentum four vector, as he ...
1
vote
1answer
155 views

On BE and FD Statistics

Lets consider the Bose-Einstein and Fermi-Dirac statistics: Bose-Einstein statistics: $$\langle n_i\rangle = \frac{1}{\exp{[(\epsilon_i-\mu)/kT]} - 1}$$ Fermi-Dirac statistics: $$\langle ...
2
votes
4answers
2k views

Inertial frames of reference

I'm struggling with the notion of an inertial frame of reference. I suspect my difficulty lies with the difference between Newtonian and relativistic inertial frames, but I can't see it. I've read ...
4
votes
2answers
354 views

Lorentz Transformation via Geometry

Today, I was tutoring and explained the space-time. I explained how one can convert North-South into West-East by rotating, and how you can convert time into space with velocity. Below the ...
8
votes
5answers
2k views

Why Negative Energy States are Bad

The argument is often given that the early attempts of constructing a relativistic theory of quantum mechanics must not have gotten everything right because they led to the necessity of negative ...
2
votes
2answers
3k views

Metric tensor of coordinate transformation

How do you find a metric tensor given a coordinate transformation, $(t', x', y', z') \rightarrow (t, x, y, z)$? Our textbook gives a somewhat vague example as it skips some steps ...
2
votes
2answers
767 views

Galilean transformation in relativity

Assume flat spacetime in a general relativistic framework (or special relativity for that matter) and two observers $A$ and $B$, with non-vanishing velocity relative to each other. We know that they ...
3
votes
5answers
2k views

About the Ether Theory acceptance

Why was the Ether Theory refused by Modern Physics? If you please explain me, I just wanted to understand it more.
1
vote
1answer
257 views

why evaluate at lambda = 0

I am trying to understand Herbert Goldstein's introduction to 4-vectors. He describes a 1-D curve in spacetime $ P_(\lambda) $ then he says a 4 vector is defined as the tangent vector to this curve ...
4
votes
3answers
1k views

Why is time order invariant in timelike interval?

Why do two observers measure the same order of events if we are inside the light cone? (e.g. if $ds^2 > 0$ time order is preserved according to the classical mechanics book I am reading, but it ...
4
votes
5answers
791 views

Does $E$ really equal $mc^2$?

I'm currently in a debate with a co-worker. If mass is sped up to the speed of light, does the mass become energy?
7
votes
3answers
465 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 < ...
4
votes
2answers
304 views

Is there a contradiction of the theory of relativity here? — Length contraction and EMR amplitude

Suppose there is a laser beam powerful enough to burn through iron aimed at a piece of iron. You observe this event while you are in the same frame as the piece of iron and the laser-beam generator. ...
15
votes
4answers
2k views

Does a photon in vacuum have a rest frame?

Quite a few of the questions given on this site mention a photon in vacuum having a rest frame such as it having a zero mass in its rest frame. I find this contradictory since photons must travel at ...
9
votes
7answers
4k views

How does Newtonian gravitation conflict with special relativity?

In the Wikipedia article Classical Field Theory (Gravitation), it says After Newtonian gravitation was found to be inconsistent with special relativity, . . . I don't see how Newtonian ...
4
votes
2answers
983 views

Can an “absolute” frame of reference be determined by measuring the compression of light?

General relativity tells us that there is no absolute frame of reference (actually, it tells us that all frames are relative, which is close but not the same as there is no absolute frame). Special ...
2
votes
1answer
470 views

What happens to speed and frequency of a light beam moving in transparent medium when observed from different inertial frame of reference?

Suppose a transparent medium where speed of light is $c/n$, an inertial frame of reference $K$ which is stationary relatively to the medium and an inertial frame of reference $K'$ which is moving ...
0
votes
2answers
204 views

Relative Synchronicity

Einstein said that the synchronization of two clocks is dependant on the velocity of the observer. But I feel a conceptual contradiction can be made: There are two observers A and B. Observer 'A' ...
1
vote
1answer
330 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 ...
3
votes
2answers
863 views

Relativistic effects

When are relativistic effects justifiably negligible? (I know that that is true for 'small velocities', but how small is 'small enough'?) 0.1c, 0.01c, etc.? And how does one properly justify that? I ...
16
votes
15answers
3k views

What are the mechanics by which Time Dilation and Length Contraction occur?

What are the mechanics of time dilation and length contraction? Going beyond the mathematical equations involving light and the "speed limit of the universe", what is observed is merely a phenomenon ...
11
votes
1answer
371 views

Can the CPT theorem be valid if Lorentz invariance is only spontaneously broken?

Earlier, I asked here whether one can have spontaneous breaking of the Lorentz symmetry and was shown a Lorentz invariant term that can drive the vacuum to not be Lorentz invariant. How relaxed are ...
10
votes
2answers
950 views

The derivation of the Belinfante-Rosenfeld tensor

It seems me that there is a "difference" (at least apparently) in how the Belinfante-Rosenfeld tensor is thought of in section 7.4 of Volume 1 of Weinberg's QFT book and in section 2.5.1 of the ...
2
votes
3answers
461 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 ...
2
votes
3answers
370 views

Does the Special Theory of Relativity “form” the foundation of Modern Physics?

Does the Special Theory of Relativity "form" the foundation of Modern Physics? My question is in reference to Geoff Brumfiel's Scientific American article "Particles Found to Travel Faster than Speed ...
9
votes
1answer
1k views

Why Lorentz Transformation in Special Relativity has to be like this?

Basically I think Albert Einstein (A.E.) was trying to find a transformation that: Always transform a constant-velocity movement into a constant-velocity movement. Always transform a ...