Relativity Definition and 998 Threads

In Galilean Relativity, laws of mechanics are invariant across frames. In all the frames they are the same. So, in Dynamics and Relativity by W.D.McComb, it is written that this implies you cannot perform any experiment in an inertial frame that can tell whether an inertial frame is moving or...

Goodmorning everyone, is there any implies to use in general relativity a metric whose coefficients are harmonic functions? For example in (1+1)-dimensions, is there any implies for using a metric ds2=E(du2+dv2) with E a harmonic function? In (1+1)-dimensions is well-know that the Einstein...

I am reading general and special relativity from a book and I am stuck with these lines please can someone provide its detailed explanation "Einstein demanded that the special principle of relativity should be valid also for Maxwell’s electromagnetic theory. This was obtained by replacing the...

It is customary, when discussing a particle's motion through spacetime, to talk about its path x^{\mu}(\lambda) , where x^{\mu} are the the spacetime coordinates of the particle in some frame, and \lambda is some parameter. I have a doubt regarding this parameter. Everywhere I've looked...

It is known that equivalence principle is good for understaning of general relativity (GR). This means comparison of the elevator and falling in homogenic gravitational field. But, I here somewhere something like "in the higher lever of GR, let us forget on principle of equivalence". How it is...

Why time perception changes continuously...? Could relativity be playing some role?

Oops, forgot to finish the title, but don't see how I can edit it. Sorry. How does one reconcile the idea that, according to relativity, one cannot talk of simultaneity, yet one can talk of a slice of spacetime to be space where all the points are at the same time? That is my main question...

I have read several times that general relativity has some problems with quantum mechanics and they are not compatible. However, special relativity can be introduced in quantum mechanics mainly by Dirac equations (so I am pretty sure that the problem of passing from a frame where the parameter...

HI, can anyone suggest a good book on general relativity with fairly good mathematics for beginner for self study?

I was bored, so I decided to derive the special relativity formulae. I drew the following diagram of a light clock: In order to find t, I did sinθ=d/ct Which gives tsinθ=d/c Which gives t=d/csinθ If v = 0, vt = 0, and θ = 90 sin90 = 1 t = d/csinθ = d/c We call this t0If v is greater than 0, vt...

arXiv:1605.08634 (cross-list from physics.pop-ph) [pdf] On The Relativity of Redshifts: Does Space Really "Expand"? Geraint F. Lewis Comments: 6 pages, 5 figures, appeared in Australian Physics Journal-ref: Australian Physics (2016), 53(3), 95-100 Subjects: Popular Physics (physics.pop-ph)...

Hi All, Once in the past I have heard that the vacuum in quantum mechanics, having its energy given by ## \sum_n \frac{1}{2}\hbar \omega_n ## was also obtained by methods of Einstein's relativity, through the claim that the vacuum should be a field which is invariant under a boost...

Why is it that for two clocks that are synchronised in one frame, S, but not in another, S', is there an offset in the time by a factor of ##\frac{Lv}{c}##, as measured in S'. Where L is the proper length of the body, as measured in S. I'm confused as to why there is not a factor of ##\gamma##...

Homework Statement This is an extract of a very long question. The electron is moving relative to the lab at 0.98c. In the reference frame of the electrons, calculate the time required for an electron to travel the length of a beam pipe which has a proper length of 100 m measured in the...

Since the temperature of a gas is related to its average molecular energy and the pressure to the average molecular momentum, it would seem that a Lorentz transformation would somehow relate the two. Does anyone know of related work?

I been studying quantum field theory and standard model lately. I not see how a unified theory could fit between quantum field and special or general relativity. One being for big objects and the other for microscopic one. In fact, standard model not seem to be all proven. Many particles are not...

Homework Statement Here's a standard example of special relativity in action: The mean lifetime of the muon as measured in a laboratory is about 2µs (rounded to 1 s.f.). Thus, the typical distance traveled by a muon should be about ##3\times 10^8ms^{-1}\times 2\times 10^6s = 600m##. The...

I have recently studied about relativity being the reason for magnetism. The example given was about a magnetic field generated from current down a long wire. When two such wires with current in the same direction were parallel to each other there was an attractive force between them because...

Homework Statement Hi all--humanist here. Now that the semester is over, I am taking the opportunity to (attempt to) self-study introductory SR. This is problem 12 in chapter 1 of Special Relativity by AP French. (1-12) A body of mass m1+Δm is connected to a body of mass m2-Δm by a spring of...

Hi all, I was trying to understand the time dilation in special and general relativity and after much time of "overthinking" I am pretty much stuck now. My problem is, that what seems to me to be the same premises apparently imply opposite things. In special relativity, for two inertial...

In special relativity, the electromagnetic field is represented by the tensor $$F^{\mu\nu} = \begin{pmatrix}0 & -E_{x} & -E_{y} & -E_{z}\\ E_{x} & 0 & -B_{z} & B_{y}\\ E_{y} & B_{z} & 0 & -B_{x}\\ E_{z} & -B_{y} & B_{x} & 0 \end{pmatrix}$$ which is an anti-symmetric matrix. Recalling the...

Homework Statement The figure shows a ship (attached to reference frame S') passing us (standing in reference frame S) with velocity http://edugen.wileyplus.com/edugen/shared/assignment/test/session.quest2564447entrance1_N1002E.mml?size=14&ver=1463885870814 =...

One of the greatest quest in physics is to reconcile Relativity with QM. But is this reconciliation really necessary? They both work quite well in their respective fields so why not just leave it at that? The only issue I can see is the problem of the singularity but can't that be solved by...

Homework Statement A relativistic train of proper length 237 m approaches a tunnel of the same proper length, at a relative speed of 0.951c. A paint bomb in the engine room is set to explode (and cover everyone with blue paint) when the front of the train passes the far end of the tunnel (event...

Hello can anyone recommend me a good mathematics package for solving the Einstein Field equations. You know one that can easily compute covariant derivatives and calculate the Reinman curvature tensor and can also minimize the Einstien Hilbert Action?

In special relativity we can view spacetime as ##\mathbb{R}^4## with its standard smooth structure, and a metric ##\eta_{ab} = \sum\limits_{\mu, \nu = 0}^3 \eta_{\mu, \nu} (dx^\mu)_a (dx^\nu)_b## where ##\nu_{\mu \nu} = \mathrm{diag}(-1, 1, 1, )##. Given a curve ##\gamma: I \rightarrow...

A moving charge that starts or stops generates a spherical wave-front of EM wave, can the same analogy be drawn for a moving mass? Reference: Electricity & Magnetism by EM Purcell

Homework Statement Two light beams collide head on. Calculate their relative velocity. (c) A particle moves north at speed 0.85c relative to an observer standing on the Earth. What is the velocity of this particle as observed by a fast ship traveling east on the Earth at speed 0.9c? Give the...

Homework Statement At exactly 00:00:00 hours, a group of convicts escape from a planet in a space-ship that travels at speed ##v=\frac{4}{5}c##. After 11 min, a patrol spaceship goes after them with ##v_P=\frac{24}{25}c##. Ignore all acceleration periods. (i) The convicts immediately notice the...

Homework Statement A spaceship travels from Earth to the vicinity of the star that is measured by astronomers on Earth to be six light-years away. The spaceship and its occupants have a total rest mass of 32 000 kg. Assume that the spaceship travels at constant velocity. The time taken as...

I was chatting to someone recently about the motion of objects and whether they propagate through spacetime or not. They were/are convinced that motion through spacetime is simply not possible arguing something along the lines of the following: "Objects move through space. If you depict an...

Dear PF Forum, I'd like to have some opinions here. A friend of mine says, "From Newton , we got car, airplane, rocket, etc. From Einstein, we got sci fi movies". Okayy, forget him :smile: Now, what I want to know is, what relativity has direct impact in our everyday life? There are two things...

Given the relativistic equation for energy E2 = (pc)2 + (mc2)2 I want to find the non-relativistic approximation for kinetic energy in non-relativistic terms, Knr = p2/2m I start off with subtracting the rest energy E0=mc2 from the above equation. So K = E - E0 and assume that c is very...

Let's say you have a planet rigged to explode only if two bowling balls hit respective sensors at the same time. An unfortunate observer, call him Carl, releases two bowling balls at the same time from his reference frame. Meanwhile, Shirley passes by at nearly the speed of light. From Shirley's...

I recently had someone ask me why we use 4-vectors in special relativity and what is the motivation for introducing them in the first place. This is the response I gave: From Einstein's postulates( i.e. 1. the principle of relativity - the laws of physics are identical (invariant) in all...

Why is it that the ZMF velocity is given by the total momentum of the system divided by the total energy? Many thanks :)

I was listening to a podcast about the solar neutrino problem, and they discussed how we have deduced that neutrinos are not massless due to the fact that they interact with other particles (even if this interaction occurs rarely). I paraphrase: "a particle traveling at the speed of light is...

I've been told contradicting ideas about this. I've been told that light doesn't travel at a constant speed everywhere (i.e. light slowing down in speed after entering a more dense medium). However, I've also read that light speed is constant everywhere (i.e. if you could travel close to the...

Hello, I need help with this problem. In 2D we have a lamp that emits light in 360 degrees around itself while stationary. Than it starts moving at velocity of c/4 what is the degree of the cone in which the light now emits to ? I hope you understand, like the angle of the field where the light...

Earlier today I was reading through this entire thread: https://www.physicsforums.com/threads/implications-of-the-statement-acceleration-is-not-relative.670653/ And I remained confused about one thing in particular. The original poster made a statement (bolded below) on page 1 that seemed...

Homework Statement Spaceship A of length 30m travels at 0.6c past spaceship B. Clocks in frame S' of spaceship A and S of spaceship B are synchronised within their respective frames of reference and are set to zero, so that t' = t = 0 at the instant the front of spaceship A passes the rear of...

What is general relativity all about. I don't know anything about it. I am an undergrad.

Homework Statement A pole-vaulter holds a 5.0 m pole. A barn has doors at both ends, 3.0 m apart. The pole-vaulter on the outside of the barn begins running toward one of the open doors, holding the pole level in the direction he is running. When passing through the barn, the pole just fits...

Homework Statement Two rockets are each 1000m long in their rest frames. Rocket A, traveling at 0.800c relative to the earth, is overtaking Rocket B, which is moving in the same direction at 0.600c. (i) According to the crew on B, how long does A take to completely pass? I.e. how long is it...

Conserved quantities in GR deal with ##p_\mu## not ##p^\mu## and while in Minkowski spacetime its easy to see what each of the components mean (since the metric is so simple) in general relativity I think its not and its starting to confuse me. Why exactly is ##-p_0## the energy in general...

Hi guys In an assignment I wrote for university I was penalised for claiming that FTL neutrinos would violate special relativity. Below is the relevant part of my assignment and the response from my lecturer. Could somebody please explain what he could mean by that because as far as I can...

I've been re-reading Hawking's Brief book (for the fourth time :-) and trying to understand a bit more. He discusses how General Relativity tell us that the planets don't orbit due to gravity, but due to the bending of space-time by mass/energy. That in fact, they are actually following a...

Hello, I am studing elementary particle physics and want to ask something, just to check if I have understood properly. So, as I understand, this is true about four-momentum in special relativity: 1. The square of the sum of particles' four momenta is invariant under Lorentz transformations...