Special relativity Definition and 1000 Threads

Hello, I graduated from Penn State in 1986 with a B.S. in Physics and a minor in Electrical Engineering. My interests are in Special and General Relativity. I also very interested in finding ways to teach and explain physics to the general public. Joe Bigler

Homework Statement Imagine we are observing two aeroplaes from the ground and let their velocities be ##\mathbf{u}## and ##\mathbf{v}## respectively. Assume that the first plane has radar equipment permitting a measurement of the speed of the other plane relative to itself. The velocity so...

Would there have been any relativistic effects if there was no ultimate speed?

Homework Statement : You are the first astronaut aboard a ship to travel to Alpha Centauri. Coincidentally, a scientist working on an outer space station post is one of your former classmate. Your ship, with your former classmate onboard, leaves the space station traveling at constant velocity...

Feynman Lectures 15-4 Transformation of time first para http://www.feynmanlectures.caltech.edu/I_15.html How is it possible that the moving clock slows down and also shows more time elapsed to the man outside?

Time dilation can be shown mathematically but what is the physical phenomenon due to which it occurs?

This must be a basic question. :) Bob and Alice have the same age. So in special relativity Bob leaves Alice and travels at very high speed and when it returns is younger than Alice. Bob's time is dilated and his space is contracted from Alice frame of reference. But now, if I take Bob's frame...

From what I have read the twin paradox can be resolved with the Rindler metric and without the need to bring in general relativity. Special relativity will suffice. But how does the Rindler metric get derived in the context of a constant accelerating reference frame. I haven't seen anything in...

Someone told me that I don't need the whole mechanics of GR to be able to calculate the proper time in an accelerated frame of reference. I can just use SR but with curved coordinates and then integrate for time. But he didn't give me a reference where I could find the formula to do this. How do...

Where in this though-experiment do I get it wrong? Even though no mass can travel faster then c, maybe information can? And I'm not talking about quantum entanglement etc. Consider a pipe, filled with balls that are very tightly arranged. If I push the outermost ball on one side of the pipe...

Hi, I am trying to wrap my brain around special relativity equations but I'm struggling with the math. I am a computer programmer comfortable with the algebra and but never studied calculus or physics. Say I am already traveling at velocity "v" where "v" is approaching the speed of light. I...

Special relativity is replete with examples of turning mirrors into clocks. Place two mirrors across from one another, bounce light between them, and measure the time. But as I thought about this, when a photon hits the mirror, it is absorbed by an electron which moves to a higher energy...

As I understand it with an orthodox interpretation of Special Relativity, if in flat space there was a velocity difference between two inertial frames of reference, then observers in either could calculate the clocks in the other to be going slower. And it could be said that both views are...

What is the difference between ##{T{_{a}}^{b}}## and ##{T{^{a}}_{b}}## ? Both are (1,1) tensors that eat a vector and a dual to produce a scalar. I understand I could act on one with the metric to raise and lower indecies to arrive at the other but is there a geometric difference between the...

Hi all! I was messing around with the equation for time dilation. What I wanted to do was see how the time of a moving observer ##t'## changed with respect to the time of a stationary observer ##t##. So I differentiated the equation for time dilation ##t'## with respect to ##t##: $$\frac {dt'}...

Hello, I would be interested in a collection of experimental data for the Michelson-Morley Experiment . I would like to see if there would be many data available, and if a statistical analysis could be of some fun. Would you know some compilation of data? Thanks, Michel

Hi 1-)If an object's total velocity through space-time(four-velocity)is c, for example even we stand still we move with velocity c (through time) and if mass slows down time, can we say mass also increase our velocity in space? 2-) Is Four-velocity magnitude constant in General Relativity...

Homework Statement There are 2 particles(1,2) separated ∆x=L moving with the same velocity u_x in frame of reference S , there's an other reference S' moving at v . I have to calculate ∆x'. GAMMA(LORENTZ'S FACTOR) Homework EquationsThe Attempt at a Solution I have done x1=0 when t=0 So for...

I took a stab at simplifying Special Relativity, but I want to be 100% sure I'm not butchering physics in the process. Anybody care to weigh in on that? Here is a draft of my Medium article: https://medium.com/@philipkd/special-relativity-explained-with-a-deck-of-cards-f99bfd873bd5 Thanks, - Phil

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'm reading Special Relativity by TM Helliwell and in it he describes the second postulate and the fact that moving with respect to air changes the speed of sound, and that because light doesn't need a medium it's speed is constant. I remember my physics teacher saying that light itself(EM...

I'm just an undergraduate with a layman's interest in Physics. With regards to special relativity, I think I grasp the concept that the laws of physics are the same for all observes in uniform motion relative to one another. So if I am standing still and a spaceship zooms past me at 80% the...

In Special Relativity, we have the four vector, (E/c, px, py, pz). However, isn't the first term just `p` given that `E=pc` for a photon? Why is it an energy-momentum four vector when the first term isn't really energy but momentum?

Homework Statement A particle A (mother particle) with a mass of mA decays to two particles B and C (daughter particles) with mass values of respectively mB and mC. Calculate momentum of the two daughter particles, pB and pC. (at first the mother particle is at rest) Homework Equations The...

I just solved an exercise in the special relativity book of A.P. French. I would like you to tell me if the answer is correct. Yes I suposse is a very easy exersice. I hope you can help me, because I really like learn relativity and cosmology, but I have not had teachers of this, and I am...

Hi I just saw this video . Here it's said that that electromagnetic force is just a consequence of special relativity, but I don't get the explanation. According to the video the electromagnetic force is generated by relative motion of charges, so it is essentially an electric force. It doesn't...

In 1851 Fizeau made a famous experiment which corroborated de Fresnel's drag coefficient of the luminiferous ether. In the experiment two light beams traveled through a tube of moving water (at 7cm per second), one moving against the water flow (let's called it beam A), and one for the water...

The energy of a photon depends on its wavelength, so theoretically when it is blueshifted it should have more energy right? Then what if a spaceship with a solar panel on the front is traveling towards the sun at relativistic speeds. An incoming photon undergoes a blueshift from the observer on...

Hi, my classmate asks me an interesting question: For a finite 4D volume in spacetime, its boundary is a 3D close surface. If the 4D volume is a 4D rectangular, the boundary consists of eight 3D surfaces. The boundary condition is specified on these eight 3D surface. Please explain the physical...

Homework Statement A rectangular structure carries clocks at its four corners. The clocks are synchronized in the structure’s rest frame, in which it has length L =4ft and width W = 3ft. In our laboratory frame the rectangle is moving in the positive x direction at speed v = 0.8c. As the clock...

The Special Theory of Relativity is based on two principles. The first one is, that if you have two objects, then it is not possible to tell which object is moving, and which object is standing still. So someone moving in a spaceship relative to observer, can't say who is actually moving and who...

Homework Statement Mavis boards a spaceship and zips Stanley on Earth a constant speed of 0.600c at the instant mavis passes, both start timers. At the instant mavis reads 0.400 s on her timer, what does Stanley read on his? Homework EquationsThe Attempt at a Solution since time from an...

Homework Statement Special Relativity Question. Consider objects 1 and 2 moving in the lab frame; they both start at the origin, and #1 moves with a speed u and #2 moves with a speed v. They both move in straight lines, with an angle θ between their trajectories (again in the lab frame). What...

(I hope this post doesn't cross the border into the forbidden realm of quackery and speculation.) I have what seems like a simple question about Special Relativity but I haven’t seen it discussed anywhere, nor has anyone I've asked. Does the nonlinearity of the Lorentz factor provide a way...

In SR, we know that ##\vec E \cdot \vec B## and ##E^{2}-B^{2}## are invariant. Although I can prove those two invariant physical quantities mathematically, I do not know how to find at least one example to demonstrate that ##\vec E \cdot \vec B## and ##E^{2}-B^{2}## are invariant. Many thanks!

Given a two particle scattering problem with (initial) relative velocity $|\vec{v}|$, apparently the product $E_{1}$E_{2}|\mathb{v}|$ can be expressed in the covariant form: $$ E_{1}E_{2}|\vec{v}| = \sqrt{ (p_{1}\cdot p_{2} - m_{1}^{2}m_{2}^{2}} $$ My textbook gives no further explanation -...

There are a pair of entangled particles moving in opposite directions. A measurement is done on particle A, the wavefunction collapses randomly, you observe either spin up or spin down, A does an action at a distance on B, particle B instantly collapses to the opposite spin state, a measurement...

Homework Statement A thin rod of proper length 4a is traveling along the x-axis of a frame S with a speed ##{\frac {\sqrt 3} 2}c## in the positive x-direction. A hollow cylinder CD of proper length 2a is placed with its axis along the x-axis, so that when the ends of the cylinder are open the...

Homework Statement Two spaceships pass each other. Spaceship A moves relative to nearby planet at velocity v1 , while spaceship B moves at velocity v2 relative to the planet . How fast does spaceship A moves relative to spaceship B. Homework Equations Velocity Transformation : v* =...

Greetings Folks, I expect to be interested to post profound news here in a few days. Together with trimmings, it will come in very few lines. So it probably will not take much of your time to decide whether you are interested or not. I hope you do not find such an engagement to be...

Homework Statement a) [Solved] What is the threshold energy in the center of mass for production of an antiproton in a proton-proton collision? Make sure quantum numbers are conserved. (This one was easy and I manage to solve it) b) In a fixed target experiment calculate the proton beam energy...

Homework Statement I'm stuck on part (d) but I've included the previous subquestions in case they're useful. The length of an asteroid is exactly 300 m = 1 µls (micro light-second) when at rest. Draw a carefully labelled space-time diagram to illustrate the following: (a) Depict the rest...

Homework Statement Show that it is impossible for an ultra-relativistic particle with ##pc>>Mc^2## to disintegrate into two identical massive particles of mass m. Homework Equations Conservation of four momentum The Attempt at a Solution The four momentum of the ultra-relativistic particle...

I read the Special Theory of Relativity in Jackson's textbook, Classical Electrodynamics 3rd edition. Consider the wave front reaches a point ##(x,y,z)## in the frame ##K## at a time t given by the equation, $$c^{2}t^{2}-(x^{2}+y^{2}+z^{2})=0 --- (1)$$ Similarly, in the frame ##K^{'}## the wave...

Homework Statement A Sigma^+ decays at rest into a neutron and a pion^+ meson, i.e. according to the reaction $$\Sigma \rightarrow n + \pi$$ The n and π masses are assumed known. The kinetic energy of the π + is measured to be 92 MeV. Determine the momentum of the pion. Homework Equations...

Can anyone briefly explain the difference between covariance and invariance in terms of special relativity? My understanding is that an invariant quantity is a value which does not change regardless of frame of reference it is being measured in. Covariance is a value which when measured in...

I'm having trouble understanding how the 4-wave vector is derived, and also how it is then used alongside the 4-momentum vector to formulate the relativistic de Broglie equation. The inner product of the 4-momentum vector with itself, is an invariant quantity. If we define the 4-momentum...

Greg Bernhardt submitted a new PF Insights post Rindler Motion in Special Relativity, Part 2: Rindler Coordinates Continue reading the Original PF Insights Post.

Homework Statement In an electromagnetic filed, the elctric field ##\vec{E}## forms an angle ##\theta## with the magnetic field ##\vec{B}##, and ##\theta## is invariant for all inertial observers. Finding the value of ##\theta##. Homework Equations Tranformations of fields perpendicular to the...

Homework Statement S and S' are in standard configuration with v=αc (0<α<1). If a rod at rest in S' makes an angle of 45o with Ox in S and 30o with O'x in S', then find α. Homework Equations We are in the world of Lorentz transformations so we have t'=(t-vx/c2)/(1-v2/c2)1/2...