What is Special relativity: Definition and 1000 Discussions
In physics, the special theory of relativity, or special relativity for short, is a scientific theory regarding the relationship between space and time. In Albert Einstein's original treatment, the theory is based on two postulates:
The laws of physics are invariant (that is, identical) in all inertial frames of reference (that is, frames of reference with no acceleration).
The speed of light in vacuum is the same for all observers, regardless of the motion of the light source or observer.
This problem bothered me many years ago when I was taking a university course in
quantum mechanics, but I assumed it was due to an error on my part which I, however,
couldn’t locate, and I didn’t ask my course instructor about it. Recently, when
researching a q.m. question on the Internet...
This is probably extremely wrong I just want to know how. If photons don't experience time doesn't that mean they are every where at once, and if that is true doesn't part of quantum physics say before a particle is observed its in all the states it can be in? So doesn't that apply in that sense...
Good evening. I think I've got it as far as time dilation is concerned. Could someone please let me know if this calculation is correct?
- From frame C( stationary camera) Bob is moving at 50,000KM/second parallel to Alice's path
- Bob is also 50,000KM behind Alice on the parallel path
- Bob's...
I know that c is the same in all reference frames. I am trying to understand the rail car thought experiment.
I've got it down pretty well except for one part - the difference between an observer moving toward a light source versus an observer moving away from a light source at the same...
Hi pf,
When I was taught about SR, I was told it was one of the most successful theories in science and has been verified over and over again. However, I have been watching some videos online and wanted some guidance. I initially came across this:
<link deleted>
This guy claims to have a PhD...
Special Relativity dictates that if there is relative motion between two objects; their relative experience of time will change and this is measurable at velocities approaching 'c'.
Within the context of the Double-slit Experiment (with detection): When a given quantum-duality is detected by a...
Homework Statement
Two spaceships fly toward a space station as shown in the figure. Relative to the station, spaceship A has speed 0.8c. Relative to the station, what speed is required of spaceship B such that its pilot sees A and the station approach B at the same speed?
(a) 0.40c (b) 0.50c...
I'm reading "Bang!", by Brian May, Patrick Moore and Chris Lintott. On page 40, they say:
"So one [observer] may believe A preceded B by a minute, and another that A and B were simultaneous, it is impossible for any observer to see B preceding A. Hence cause and effect are preserved..."
But in...
Homework Statement
How can we tell that quantum effects do not propagate along forward light-cones that represent two separate events? How do light-cones demonstrate this notion of quantum effects? Homework EquationsThe Attempt at a Solution
We don't know which events occur first given...
Hi,
I've been following a derivation of relativistic kinetic energy. I've seen other ways to get the end result but I'm interested in finding out where I've gone wrong here: I'm struggling with integrating by parts.
The author goes from...
When expanding Kinetic energy as
T=mc2-m0c2
where m0=rest mass and
m=m0/sqrt(1-β2)
the first term correction is coming out to be -p4/8m03c2
but taking T=E-m0c2
where E=sqrt(c^2p^2+m02c4) the correction is coming to be 3p^4/8m03c2
is there any contradiction?
Consider single line motion. If an observer sees two objects, and one is seen moving say 50 m/s faster than the other, will all other observers measure the same velocity difference? The answer seems to be 'No' from the velocity addition formula of special relativity?
Thus same velocity...
Hello everyone,
For some time I'm a little bit confused about (at the first view) a very simple question, which is about the conversation of the energy of moving objects (in terms of special relativity).
As an example let's talk about firearms. If the mass of the gun M1 is infinitely higher...
Homework Statement
An electric dipole instantaneously at rest at the origin in the frame K' has potentials \Phi'=\mathbf{p}\cdot\mathbf{r}'/r'^3 and \mathbf{A}'=0 (and thus only an electric field). The frame K' moves with uniform velocity \mathbf{v}=\vec{\beta }c in the frame K.
Show that in...
Hi,
If a particle is within 2 m/s of the speed of light (like at CERN) and then more energy is transferred to the particle, where does this energy go? Some sources I have read talk about relativistic mass getting bigger and approaching infinity as a particle approaches 'c'. However, this source...
I am having a hard time trying to understand this transformation from lorentz:https://imgur.com/a/WYWMO
(You should ignore the spanish part and just focus on the math). I can’t understand well why they turn into what you can see in the second picture, when taking really small values of x...
Hello.
I want to clear a doubt on Special Relativity, time dilation and clocks.
If we get an accurate clock and make it orbit the, for example, Earth very, very fast, will the actual mechanical clock lag behind from the accurate clocks on Earth? The thing in this question is about the actual...
Homework Statement
Anna and Bob are both born just as Anna's spaceship passes Earth at 0.9c. According to Bob on Earth, Planet Z is a fixed 30 ly away. As Anna passes Planet Z on her continuing outward journey, what will be (a) Bob's age according to Bob, (b) Bob's age according to Anna, (c)...
Hi,
Can someone please anlayse the visual effects for light travel in the documentary 'Journey to edge of the universe'
Especially around the 43:12 and the 1:02:20 mark.
Can you also tell me if it is or is not an accurate depiction of what we should be seeing theoretically?
I try to find the formula of dilation of time between a reference frame (R') moving at a speed v and a fixed observer in (R). For this, I take the example that we often find as a demo : that of a train in which a light beam is emitted vertically (in the train): this vertical trajectory in the...
You are launched upward inside a railway coach in a horizontal position with respect to the surface of Earth, as shown in the figure. After the launch, but while the coach is still rising, you release two ball bearings at opposite ends of the train and at rest with respect to the train.
a)...
A non-moving observer is looking at two different rockets in space. One rocket is moving at a steady velocity of 0.5c, and the other rocket is currently moving in 0.5c but has steadily accelerated from 0.3c and will continue accelerating until it gets to 0.7c.
Assuming that there is no...
How can volumes and hypervolumes be related to Einstein's theory of special relativity and to quantum mechanics? Also, can volumes and hypervolumes of objects be used for modeling how different scenarios can change over time? Oh yeah, and hi my name is Sasha Jaffarove!
Homework Statement
Homework EquationsThe Attempt at a Solution
it is known that
##a_0
##is the proper acceleration
##
a= \frac{a_0}{\gamma^3}
##
hence integrating it gets
##
v = \frac{a_0t}{\sqrt{1 + (\frac{a_0 t}{c})^2}}
##
but this is in terms of t how to make it in terms of t'
If a frame S' moves with velocity v in x direction wrt S, and you have v = 0.5c, u_x' = -0.9c and u_y' = 0.9c then it seems you find that u_y = 1.417c, greater than c.
The relevant formula is:
u_y = u_y'/(gamma * [1+v u_x' / c^2])
Apologies for formatting.
Details: gamma = 1/sqrt(1-v^2/c^2)...
Homework Statement
My textbook states:
Since the number of particles of dust is conserved we also have the conservation equation
$$\nabla_\mu (\rho u^\mu)=0$$
Where ##\rho=nm=N/(\mathrm{d}x \cdot \mathrm{d}y \cdot \mathrm{d}z) m## is the mass per infinitesimal volume and ## (u^\mu) ## is...
Hello,
I'm self-studying Ta-Pei Cheng's Relativity, Gravitation and Cosmology. Problem 2.8 is the following:
Two spaceships traveling in opposite directions pass one another at a relative speed of ##1.25 \times 10^8## m/s. The clock on one spaceship records a time duration of ##9.1 \times...
Let's assume that a and b charges are moving. now in our lab frame there will be a electric+magnetic force whereas in a rest frame of either of the charges, there will be only an electric force.
So, two inertial observers will measure different forces?
I've commonly heard it said that Lorentz invariance is equivalent to saying that special relativity is obeyed, although I also recall discussions arguing that this is not precisely and technically correct, although the two concepts heavily overlap.
I also understand that Lorentz invariance has...
In Schutz's A First Course in General Relativity (second edition, page 45, in the context of special relativity) he gives the scalar product of four basis vectors in a frame as follows:
$$\vec{e}_{0}\cdot\vec{e}_{0}=-1,$$...
Homework Statement
Our galaxy is about 10^5 light-years across, and the most energectic particles known have an energy of about 10^19 eV. How long would it take a proton with this energy to traverse the galaxy as measured from (a) the galaxy and (b) the particle?
Homework Equations
I...
Homework Statement
Before the discovery of the neutron, it was proposed that the penetrating radiation produced when beryllium was bombarded with alpha particles consisted of high-energy &gamma rays (up to 50 MeV) produced in reactions such as α + 9Be --> 13C + γ
a.) Calculate the Q value for...
Hi There,
I've been spending some of my free time learning about Quantum Mechanics. This was all going somewhat smoothly, until I encountered something known as "Entanglement Swapping" while learning about loophole free bell tests, such as the one conducted by Hensen et al at TU Delft in 2015...
I don't uderstand how, using special relativity theory (time dilatation and length contraction), one can explain why in the Michelson interferometer there is no delay between the two rays in the reference frame where the interferometer is moving. Consider the picture ##2.##
Setting...
Pardon me if this has been asked before, but I'm confused with the implication that SR makes, that there is no objective moment of present. Do the science still believe that the time flows (i don't mean the arrow of time, but the phenomena of flowing/passing, eq. flowing of a river)? I mean, how...
Homework Statement
A visit to Regulus is on my bucket list. However, it is 77 light years away. Assuming I will live only another 40 years, can I make it to Regulus? How fast would I have to travel (at constant speed) to get there in 40 years?
Homework Equations
t1 = t0...
Let's assume that a light source is moving parralel to x-axis and is in point x,y,z in lab frame. Suppose it emits a light ray. In the rest frame that coincides with the lab frame, the light source is in point x',y and z.
However, because of relativistic aberration the two light rays will make...
Hello,
In my free time, I've been learning about an eclectic range of topics (ie. French History, Kinetic Theory etc.). Most recently I've been focused on Quantum Mechanics, which happens to be most complex topic I've ever looked at. Typically I write up summaries after reading from various...
Imagine yourself to be bat. You can't see anything. You don't have eyes. All you can do is echolocate, using ultrasound.
Now imagine something is moving away from you faster than the speed of sound. Can you locate it ? Can you perceive its existence ?
If the answer is yes, how ?
If no , then...
Hello!
If energy bends spacetime, then an object moving at high velocity will bend spacetime a lot around it due to its really big kinetic energy. It follows, that an object can become a black hole at extremely high enough velocities.
But, since velocity is relative, we can find an observer for...
Is it fair to say that the photon does not follow the rules of Special Relativity? I ask this because the photon relative to all other frames of reference has zero mass even though it is traveling at the speed of light. If we increase the speed of any other particle to the speed of light its...
Hi all,
I have a problem to fully understand how we can apply Special Relativity to a system where one observer is still in the center, and other one is moving in a circle around. For example, like a satellite orbiting Earth. In case of GPS, the clocks carried by satellite are running slower...
I'm working on semiconductor physics and cyclotrons.
There's an article that I am trying to understand, but am having difficulties matching with experiment. I asked a question on an electronics site, but apparently the physics is too advanced.
The relativity article which sparked my interest...
I have a random paradox I seem to have found with three colliding observers, though to explain it properly I'm going to use a bit of visual aid and a bit of abstracting it from the math (or setting the math so that it works according to my example).
For anyone who wants the TLDR, read this...
Hi, I have yet another question in the field of the special relativity theory.
I always thought that the derivation of the relativistic mass is trivial. But I discovered that there is some complexity due to the transverse and longitudinal relativistic mass derivation.
I saw a thread where...
Let's assume that a disk is rotating with relativistic speed in a frame. We can find the velocity of a particle using v=rw formula. However, what is the r in this formula? is it the radius of the disk in rest frame or in the lab frame??
And Is the magnitude of velocity same for all points of...
Hello everyone,
Reminder: The key of the explanation of the "twin paradox" resides in the acceleration. We know that the time runs slower for the twin in the spaceship (since it was accelerated)...
Given a Weyl Hamiltonian, at rest,
\begin{align}
H = \vec \sigma \cdot \vec{p}
\end{align}
A Lorentz boost in the x-direction returns
\begin{align}
H = \vec\sigma\cdot\vec{p} - \gamma\sigma_0 p_x
\end{align}
The second term gives rise to a tilt in the "light" cone of graphene. My doubts...
I am trying to get this idea of Time dilation understood.
If there exists only two objects in a Universe and one object is stationary and the other object is moving at 99 % the speed of light. Their clocks were both synchronized when both objects were stationary relative to each other. Then the...
Homework Statement
I have noticed that in some calculations they use $$ \vec{\nabla}\cdot\vec{u}=\frac{1}{V}\frac{dV}{d\tau}$$. I would like to derive it.
Homework Equations
##\vec{u}=(\frac{dt}{d\tau},\frac{dx}{d\tau},\frac{dy}{d\tau},\frac{dz}{d\tau})##
##\vec{A}\cdot\vec{B}=A^{\mu}B_{\mu}##...