Sr Definition and 477 Threads

Suppose an observer (O) sees a traveler (T1) pass by at time t=0, moving a speed 3c/5. Five years later (according to O), T1 returns. If we assume that T1 traveled at 3c/5 for half the journey and instantaneously reversed direction, returning at the same speed, we can calculate that T1 aged only...

So let us say that there are 3 separate alien species that somehow speak and write the same language. Let us say that 2 of these have always lived and died in their spaceships/asteriod ... going at speeds close to that of light. Alien species 3. A3 leaves behind a message saying that at time t0...

Homework Statement We observe an experimentalist moving by with 4-velocity ##u^\mu## and a particle zipping by with 4-momentum ##p^\mu##. Show that magnitude of the particle's 3-momentum as seen by the experimentalist is given by $$ |\vec p| = \left [ (p \cdot u)^2 + (p \cdot p)^2 \right ]...

I don't really understand how time dilation works in SR. I just know this that "Now" in one reference frame is not the same in another so for example when Observer A says his time is 10s then at the same moment he will say Observer B's time who is moving relative to him is 5s for example. The...

In Classical Mechanics, according to SR, the concept of simultaneity is dead, a meaningless concept. But in QM, entanglement implies that some limited form of simultaneity exists. If we have two particles correlated due to entanglement, a measurement of one particle immediately gives us the...

Homework Statement P.S.: I'm not sure if it is allowed to ask multi-part questions. Two equally old sisters Alice and Barbara leave Earth simultaneously in opposite directions. The following velocities and distances have been measured in the Earth system. Alice travels with a speed of ##v_A =...

<Moderator's note: Split from another thread and thus no template.> I am working on my special relativity assignment right now, and it said to find the velocity of an object when it hits the ground. The height the object is launched at is > 0. Question: comparing that velocity to the...

Consider the traditional thought experiment of moving train observers, the "stationary" observers, and the flash of a lightning strike at the midpoint of the train. It seems that the stationary observers would expect the train observers to see different flash intensities (due to different...

Hi all, I have two questions about light in Special Relativity. (I'm going to pad these questions out with a few statements about my understanding of length contraction and time dilation, so you can see how I currently think about it and clear up any misconceptions if I've got the basic idea...

@SiennaTheGr8 the SR Globe you linked to recently is a wonderful visualization aid. I was hoping to find an app that is a virtual version, but I haven't been able to, all I've been able to find are relatively uninspiring single point calculators that are about as engaging as converting lbs to...

Bob is an observer at rest in Minkowski space at ##x=L##. Alice moves in a constant acceleration (in her system). her path is depicted in the attached file, when Alice passes by Bob they synchronize their watches and Bob activates an apparatus that signals pulses to Alice. Every short time...

Homework Statement [This problem is part of a preparation for modifying the concepts involved in special relativity.] Two cars collide and lock together. They are each a mass of 800 kg and were traveling at a steady 20 m/s in opposite directions prior to collision. a) What's the kinetic...

As I understand if it were possible to send a single faster than light then one can send a signal back into the past. What is the simplest way to explain how this would happen?

Special relativity says that all clocks will show same time dilation, irrespective of clock mechanism. But Time period of a clock is a formula that must continue to hold even if time dilates. Let us look at a tuning fork clock. Here time period depends on the dimensions of the vibrating...

I’ve just realized something is wrong with my understanding of SR and I would really appreciate if you helped me sort it out. :) This won’t be a post with loads of formulas, rather the confusion is a conceptual. One way to describe my confusion is to put it into the twin paradox, although it’s...

So I learned from the first few posts on this https://www.physicsforums.com/threads/ftl-train-ftl-communication-thought-experiment.945116/ thread that one can actually work with special relativity in non inertial frames. I'd like to get some points on this. Firstly, by a non inertial frame, I...

I recall reading that in the context of special relativity, one will notice differences in the acceleration of an idealized born-rigid spaceship when one compares two identical spaceships, one with the rocket motor mounted in front, the other with the rocket motor mounted in the rear. I'm...

Homework Statement A Higgs particle of mass M is moving in the z-direction with speed $\Beta_H$c compared to the lab system. It decays to a b-quark ans anti-b quark, each of mass m. What is the speed and direction of the b-quark compared to the lab-system, if the Higgs system, (a) it is emitted...

I remember reaching to the conclusion that changing the reference frame (Galilean transformation) doesn't give the same result in Electromagnetism interactions in high school, I searched for an answer and didn't look any further than knowing that SR solved this. Now I am back in an engineering...

In Special Relativity, acceleration at high speeds causes time dilation and length contraction. Is it fair to restate this as; Acceleration at high speeds causes curvature of spacetime? In General Relativity, curvature of spacetime causes acceleration. Acceleration at high speeds causes...

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...

I have always been wondering whether GR is generally, see what I did there :), more important in terms of science than special relativity.

Homework Statement The Lorentz Force can be used to sort ions (atomic or molecular) based on their charge to mass ratio. This configuration has been used to separate isotopes and as a mass spectrometer. A beam of Strontium ions Sr+ is accelerated through a potential of 500 V and injected into...

Hi, thanks to a different thread/question on this forum I've come to appreciate time dilation ..somewhat. And from that I wondered if, given the range of locally measured times aboard any and all particles in the universe, given their different trajectories and histories since the big bang...

I'm attempting to use a artificial neural network to store a fuzzy floating point variable. While writing the code, I became somewhat creative. I used the idea of an Set Reset Latch and statistically translated the hardware SR-latch into an artificial neural network. My mathematical goal is to...

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...

Homework Statement Special relativity: A rod traveling with the relativistic velocity of 0.866c moving towards a garage. The length of the rod is L, that of the garage is L/2. From the reference frame of the garage, we find the value of Lorentz factor = 2 we say that rod would fit inside garage...

Homework Statement A train of length L moves at speed 4c/5 eastward, and a train of length 3L moves at speed 3c/5 westward. How fast must someone run along the ground if he is to coincide with both the fronts-passing-each-other and backs-passingeach-other events? Homework Equations Velocity...

This post is about the methodology required to produce the Fig. 9 Part C “optical appearance” plot as calculated by Øyvind Grøn in "Space geometry in rotating reference frames: A historical appraisal". http://areeweb.polito.it/ricerca/relgrav/solciclos/gron_d.pdf In 2014 I contributed to a...

I'd like to get some conceptual clarification on whether or not length contraction is only apparent to an observer or if it's physically real in the sense that the object under contraction would experience compressive forces? My thinking on this has been along the lines of: I know that time...

To draw oblique coordinates with the coordinates measured perpendicular to each axis would be wrong, right? I saw it done in a fairly popular book. It's usually the case that I'm the one who is wrong, but I think the book is incorrectly treating minkowski diagrams. Look at these images from...

Event is anything which can be located by (x,y,z,t). We don't need this concept in Galilean transformation. I was first introduced to the concept in the beginning of Special relativity. I haven't understood the significance of this concept till now. Can anyone please illustrate me using an...

I am self -studying SR with Books written by Resnick and A.P.French. Is that o.k. or should I take some another book? I am asking this because there are no. of books suggested on P.F., but these suggestions don't include Resnick and A.P.French.

I combined three maps of Chernobyl fallout: Cs-137 map, Sr-90 map and Pu-239 map. Map scales are the same. Lowest contour levels for Cs and Sr are the same (1 Ci/km^2), Pu contour is ten times lower (0.1 Ci/km^2). This visually demonstrates that Cs is about ten times more widespread fallout...

Hi, I was wondering, as in the Bachelor's degree curriculum there is no SR course, for one who is interested in theoretical physics (as me), would do it alone, perhaps with texts such as Rindler or Synge ...? Thank you in advance !

Homework Statement Given: An object at rest with respect to an inertial reference frame S. 2 other inertial reference frames S' and S''. S' has velocity (vx, vy) = (-.6c, 0) with respect to S. S'' has velocity (vx, vy) = (-.6c, +.6c) with respect to S. Assumptions: If I transform my...

Hello everyone. I've just recently found this forum and it has been a lot of fun browsing around. I've recently taken a stronger interest in the topics of relativity in physics and have recently developed a much better understanding of SR (and somewhat of GR) than I'd had previously and its been...

In the context of General Relativity spacetime is a four-dimensional Lorentzian manifold M with metric tensor g, its Levi-Civita connection \nabla and a time orientation vector field T \in \Gamma(TM). In this context I've seem the following three definitions: A coordinate system is a chart...

Hello everyone, here I come with a question about inertial frames as defined in General Relativity, and how to prove that the general definition is consistent with the particular case of Special Relativity. So to contextualize, I have found that one can define inertial frames in General...

Forgetting for the moment about curved spacetime, does the relativistic QFT in use today by experimental physicists live in Euclidean spacetime or Minkowski spacetime. Thanks in advance.

Since in GR and SR the basis vectors are generally orthogonal, how can we take derivatives of position with respect to time? For example, the current four-vector is $$J^{\alpha} = \sum_n e_{n} \frac{\partial x^{\alpha}}{\partial t} \delta^{3}(x - x_{n})$$ where n labels the n-th particle. In...

Homework Statement A muon has a mass of 106MeV/c2. Calculate the speed, momentum and total energy of a 200MeV muon(a muon with a kinetic energy of 200MeV). Homework Equations E=γmc K+mc2=E γ=1/(1-β)1/2 β=(v/c)2 The Attempt at a Solution To solve for the speed I plugged E=γmc into K+mc2=E to...

I’m looking for feedback with respect to an SR “paradox”. I’ve gotten myself into a dialog with an Anti-Relativity activist. I know I’ll hate myself in the morning but I thought I would at least make an attempt at explaining this “paradox”. You may be familiar with it. It goes like this...

According to this author, http://www.math.uic.edu/undergraduate/mathclub/talks/Weeks_AMM2001.pdf, a locally Minkowski spacetime with a nontrivial global topology may have a preferred inertial frame, in the sense that hypersurfaces of constant time can only be defined using particular time...

In his seminal paper on Special Relativity: On the Electrodynamics of Moving Bodies, Einstein derives a formula for the Relativistic Doppler effect. See this section: § 7. Theory of Doppler's Principle and of AberrationThe formula is: In this Wiki article, the same formula is derived. The...

I have no college degree or any advanced formal training in physics, so this may be really, really obvious. Please be kind. In GR, the amount by which time slows down on the surface of Earth compared to "empty" space is: SQRT(1-2GM/(RC^2)). For the surface of Earth that's 6.96 E-10 seconds...

I am following some lecture notes looking at the invariance of Poincare transformation acting on flat space-time with the minkowski metric: ##x'^{u} = \Lambda ^{u}## ##_{a} x^{a} + a^{u} ## [1], where ##a^{u}## is a constant vector and ##\Lambda^{uv}## is such that it leaves the minkowski...

Homework Statement A space explorer travels in a spaceship with v = 0.9c. She goes from Earth to a distant star that is 4 light years away (again, measured from Earth). What is the distance measured by the explorer and how long will she say it took her to get there? Homework Equations...

Hi everybody! The last chapter of my course named "Advanced Mechanics and Special Relativity" treats of Lorentz transformations, but the script of my teacher does not explain much about the notation used and it's getting quite confusing for me without understanding it fully. So far we've...

For quite a long time now I'm having some trouble to bridge the gap between two different approaches to Special Relativity. The first approach is the traditional one. It is the approach that Einstein presented in his paper and that is taught in most of the basic textbooks. In this approach...