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Question: <p>I came across this exercise in Elementary General Relativity by Alan MacDonald:</p>
<p>A source of light pulses moves with speed v directly away from an observer at rest in an inertial frame. Let $ \Delta t_e $ be the time between the emission of pulses, and $ \Delta t_o $ be the time between their recept... | https://physics.stackexchange.com/questions/68132/doppler-redshift-in-special-relativity |
Question: <p>How are classical formulas in physics (such as p = mv, or kinetic energy, or maxwell distribution of speeds) treated with the appropriate relativistic correction/modification? Is it done by using the Lorentz transformation equations? Could anyone give me a few examples of relativistic corrections to classi... | https://physics.stackexchange.com/questions/71943/relativistic-corrections-to-classical-physics-formulae |
Question: <p>Hi all I'm a little confused </p>
<p>So I have that in special relativity time is included as a coordinate so that in 1 spatial dimension we have 2 space time coordinates. The most basic metric is the Minkowski metric given by $\left[ {\begin{array}{*{20}{c}}
{ - 1}&0 \\
0&1
\end{array}} \r... | https://physics.stackexchange.com/questions/76134/minkowski-metric |
Question: <p>In many textbooks, the interval</p>
<p>$$
I = -(c\Delta t)^2 + (\Delta x)^2 + (\Delta y)^2 + (\Delta z)^2
$$</p>
<p>is taken for granted as the same for two events in any reference frame.</p>
<p>Is it possible to derive this just from the two postulates,</p>
<ol>
<li>That the laws of physics are the sa... | https://physics.stackexchange.com/questions/76716/is-it-possible-to-derive-the-invariant-spacetime-interval-from-einsteins-two-po |
Question: <p>Let we consider time in stationary frmae t, and respect the to stationary frame moving frame time $t^ \prime $ .</p>
<p>According to lorentz transformation,</p>
<p>$$t^\prime= \frac{t-\frac{vx}{c^2}}{\sqrt{1-\frac{v^2}{c^2}}}$$ and according to inverse Lorentz transformation, $$t= \frac{t^\prime +\frac... | https://physics.stackexchange.com/questions/83841/time-dilation-apeears-in-the-both-frame-where-is-the-problem |
Question: <p>If I am a stationary observer and the electrons are moving relative to me,then shouldn't its density increase according to special relativity and thereby create an altogether negative net charge.</p>
Answer: <p>Increase in density doesn't mean that it creates negative net charge. The charge is preserved. ... | https://physics.stackexchange.com/questions/83908/special-relativity-and-current-in-wire |
Question: <p>If light is travelling vertically upwards and I am travelling horizontally and perpendicular to light, the velocity of light in the vertical direction will get reduced. How does this happen? How does motion in x-direction cause a reduction in speed of light in y-direction ?</p>
<p>Also, in Lorentz Transfo... | https://physics.stackexchange.com/questions/91344/speed-of-light-and-special-relativity |
Question: <p>Say I have a ball at 0.999999% the speed of light going past the Sun toward Earth. Now from the ball's reference frame, the distance between Earth and Sun is the same length as the ball's diameter. Why is the ball occupying the entire space between the Earth and Sun? What happened if a comet was between th... | https://physics.stackexchange.com/questions/91084/how-is-length-contraction-reconciled-with-other-objects-occupying-space |
Question: <p>How can two clocks be synchronised with each other at some instant without being at the same place and same time $?$ considering that simultaneity is a relative concept .</p>
Answer: <p>Here's the standard way in flat spacetime. Let's say you want to produce a synchronized pair of clocks that are a spati... | https://physics.stackexchange.com/questions/93463/synchronisation-of-clocks |
Question: <p><a href="http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/Special_relativity_rel_sim/index.html" rel="nofollow">http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/Special_relativity_rel_sim/index.html</a></p>
<p>Talking about the situation of clocks shown on this page. Clocks A&B. Now su... | https://physics.stackexchange.com/questions/93675/moving-clocks-time-problem |
Question: <p>Two light sources emit light at the same moment but in opposite directions. At what speed the distance between two light fronts is increasing? <strong>c</strong> or <strong>c</strong> * 2?</p>
<p>Note, that there is only one coordinate system here - a system, where these two light sources are placed and t... | https://physics.stackexchange.com/questions/94492/relativity-and-speed-of-light-again-two-opposite-light-sources |
Question: <p>Reference) "Feynman lectures on Physics Vol.3 , p.7-4 ."</p>
<p>With four vectors $x_{\mu} = (t,x,y,z)\ , \ p_{\mu} = (E,p_{x},p_{y},p_{z})$</p>
<p>the inner product of these two four vectors is scalar invariant and equals to $Et - \overrightarrow{p} \overrightarrow{x}$ . Alright.</p>
<p>But I cannot un... | https://physics.stackexchange.com/questions/32762/inner-product-of-four-vectors-in-special-relativity |
Question: <p>I'm struggling with an introductory example of special relativity. We haven't done the math yet so I would like an explanation based only on the fact that the speed of light is the same in every inertial frame.</p>
<p>An airplane travels east with a certain speed. There is a "clock" at both ends of the ai... | https://physics.stackexchange.com/questions/43258/airplane-example-of-special-relativity |
Question: <p>Could someone explain to me how <a href="http://en.wikipedia.org/wiki/Special_relativity" rel="nofollow">special relativity</a> works?</p>
<p>I know there are thousands of sources and databases of knowledge out there, but I find it difficult to understand, even after reading up on those sources.</p>
<p>(... | https://physics.stackexchange.com/questions/45308/special-relativity |
Question: <p>this is relativistic action:
$$S=\int_C \mathcal {L}dt$$
where the $\mathcal{L}$ is $-m_oc^2\gamma^{-1}$
what is use of relativistic action!?</p>
Answer: <p>The use of an action is do derive all the dynamical equations of a theory from the least-action principle, $\delta S=0$ (action is minimized along th... | https://physics.stackexchange.com/questions/52122/what-is-use-of-relativistic-action |
Question: <p>$$\text{proper time}= \tau= \sqrt{dt^2-d\mathbf{s}^2}$$</p>
<p>$$\text{proper length}= L= \sqrt{-dt^2+d\mathbf{s}^2}$$</p>
<p>What tangible benefit is brought about by calling $i \tau$ 'proper length' (applying when $\Im(L)=0$ (the spacetime intervals are spacelike))?</p>
<p>Could one extend the notion ... | https://physics.stackexchange.com/questions/52912/why-does-proper-length-exist-as-a-notion |
Question: <p>Proper time is used to parameterize the world line of a moving particle in a way which is Lorentz invariant, which is elegant and powerful. Since space and time are usually treated on the same footing, I'd expect proper length to be a powerful parameter of some sort, yet I've never come across it being use... | https://physics.stackexchange.com/questions/55007/what-are-the-uses-of-proper-length-as-a-parameter |
Question: <p>Let's assume I have a spaceship in front of me let's say at 1000000km distance. Now let's assume I have also a stationary wall just behind the spaceship at 999999km. Initially the spaceship's speed is 0.</p>
<p>Now let's accelerate the spaceship rapidly to relativistic speeds.</p>
<p>Due to the length co... | https://physics.stackexchange.com/questions/62008/does-an-accelerating-spaceship-move-backwards-due-to-length-contraction |
Question: <p>I want to write $F^{\mu \nu}F_{\mu \nu}$ in terms of $F_{\mu \nu}F^{\mu \nu}$. How to do it?</p>
Answer: <p>The two expressions you wrote down are the same because for each pair $(\mu,\nu)$, the quantities $F^{\mu\nu}$ and $F_{\mu\nu}$ are real numbers and can be commuted past one another.</p>
| https://physics.stackexchange.com/questions/62309/faraday-tensor-antisymmetric-electromagnetic-tensor |
Question: <p>Suppose a man leaves from Earth to a star which is 1000 light years away. He accelerates to a velocity such that the entire trip lasts a year, from the reference frame of the rocket.</p>
<p>Now lets pretend the person in the rocket wants to have a transmission of the radio to him.</p>
<p>Due to time dila... | https://physics.stackexchange.com/questions/62851/doppler-shift-of-radio-signals-to-an-accelerating-observer |
Question: <p>Einstein in his thought experiment(?) for the constancy of speed of light in vacuum in all frames reasoned , that if speed of light of vacuum isn't constant than you'll be able to perceive effect before action .</p>
<p>But then this must happen in all mediums , but it doesn't ,that means if you live in a ... | https://physics.stackexchange.com/questions/64419/speed-of-light-and-information |
Question: <p>I have just started looking into special relativity and I have come up with an intriguing <em>gedanke</em>, as Einstein himself called such theoretical thought experiments.</p>
<p>Imagine a space shuttle traveling through space at a constant velocity close to $c$. As the shuttle passes earth, a previously... | https://physics.stackexchange.com/questions/8539/a-video-conference-between-earth-and-a-space-shuttle |
Question: <p>I'm working in a book on relativity. The author states that if $u$ and $u'$ are a velocity referred to two inertial frames with relative velocity $v$ confined to the $x$ axis, then the quantities $l$, $m$, $n$ defined by </p>
<p>$$
(l, m, n) = \frac{1}{|u|}(u_x, u_y, u_z)
$$</p>
<p>and</p>
<p... | https://physics.stackexchange.com/questions/9507/physical-interpretation-of-equation-for-relativistic-aberration |
Question: <p>An electron is shot towards a target that is negatively charged. While the electron is traveling, the target makes an abrupt move towards the electron. While the information that the target moved is traveling from the target to the electron, the electron behaves like an electron that is moving towards a ta... | https://physics.stackexchange.com/questions/11075/how-is-energy-conserved-when-a-moving-charge-has-false-ideas-about-positions-of |
Question: <p>I am reading Landau's Volume 2 of the course of theoretical physics. I have a doubt after reading the first few pages of it which I explain below.</p>
<p>Landau first defines intervals and on pages 5 and 6 shows that two events having time like interval between them can never occur simultaneously in any r... | https://physics.stackexchange.com/questions/12265/non-interchangeability-of-time-like-intervals |
Question: <p>Many years ago (in the '70s I think) I read an explanation of the meaninglessness of simultaneity at large distances. The example had to do with two people walking along a sidewalk in opposite directions, and an alien race on a planet millions of light-years away planning an invasion of the Solar System. ... | https://physics.stackexchange.com/questions/14958/looking-for-specific-relativity-example |
Question: <p>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:</p>
<p>There are two observers A and B. Observer 'A' faces direction X, and will be labeled "stationary." Another observer B faces direction X and is tra... | https://physics.stackexchange.com/questions/15906/relative-synchronicity |
Question: <p>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 $$ v = \biggr ( \frac {dP} {d\lambda}\biggr)_{\lambda =0} $$ </p>
<p>why is $ \lambda $=0? what does tha... | https://physics.stackexchange.com/questions/16432/why-evaluate-at-lambda-0 |
Question: <p>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.</p>
<p>Below the Energy-Momentum stuff the book had some problems. One was the following:</p>
<blockquote>
<p>Given an event... | https://physics.stackexchange.com/questions/16845/lorentz-transformation-via-geometry |
Question: <p>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 answers.
Thank you.</p>
Answer: <p>No more absolute than using the position of distant Quasars</p>
| https://physics.stackexchange.com/questions/17055/a-possible-absolute-reference-system |
Question: <p>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?</p>
<p>I figure there are two competing effects at play - time dilation and diminishing distance.</p>
Answer: <p>You can see this as an example... | https://physics.stackexchange.com/questions/19370/what-would-an-observer-see-if-he-she-flew-toward-a-clock-at-relativistic-speeds |
Question: <p>Putting Special Relativity into the General Relativity category as is current practices submerges important aspects of Einstein's 1905 paper, which I recently read in a 1952 Dover paperback (The Principle of Relativity). That paper is totally unlike the modern presentations in texts. I noticed a marked dis... | https://physics.stackexchange.com/questions/20532/einsteins-famous-thought-experiment-contradiction |
Question: <p>Let's say a light clock consists of two parallel mirrors, some photons bouncing between the mirrors, and a spring that pulls the mirrors together with the same force that the photons push them apart.</p>
<p>Now we start accelerating the mirrors and the spring, in the direction parallel to the mirrors. Whe... | https://physics.stackexchange.com/questions/21419/is-radiation-pressure-constant-in-this-experiment-and-does-force-of-a-spring-ch |
Question: <p>If I use a stick to push and accelerate an object, my hand pushes one end of the stick distance $x$, while the other end of the stick pushes the object distance $y$.</p>
<p>Distance $y$ is smaller than distance $x$, because of Lorentz contraction of the stick. </p>
<p>My hand does work $Fx$.</p>
<p>Work... | https://physics.stackexchange.com/questions/21919/pushing-with-a-lorentz-contracting-stick |
Question: <p>By using some axioms people derives equation for Lorentz force and, then, Maxwell's equations from the Coulomb's law and Lorentz transformations. When I used analogical methodology for Newton's law of universal gravitation, I derived some equations like gravitomagnetic equations deriving from the GR equati... | https://physics.stackexchange.com/questions/24188/factor-2-and-equations-for-the-weak-gravitational-field |
Question: <p>Since Einstein first derived the Lorentz transformations, their generalisation and execution has changed over the century. So starting with those first derived by Einstein: </p>
<p>What are the main, increasingly sophisticated ways, of carrying out a Lorentz transformation today? What are their advantages... | https://physics.stackexchange.com/questions/29387/what-are-the-increasingly-sophisticated-ways-to-perform-a-lorentz-transformation |
Question: <ol>
<li><p>We know that cosmic microwave background temperature is about 2.7K. But what temperature we will measure in space using a simple Kelvin thermometer in the shadow? Can it be lower than 2.7K?</p></li>
<li><p>Suppose a space ship is flying in our solar system with a speed of 0.99c relative to earth. ... | https://physics.stackexchange.com/questions/29418/the-temperature-in-space |
Question: <p>I have a question about finding inverse Lorentz transformations explicitly, in matrix form:</p>
<p>Suppose I have a Lorentz transformation $\Lambda^\mu_{\;\nu}$, with matrix representation $\underline{\underline{\Lambda}}$. The inverse Lorentz transformation $(\Lambda^{-1})^\mu_{\;\nu}=\Lambda_\nu^{\;\mu}... | https://physics.stackexchange.com/questions/408382/computing-inverse-lorentz-transformations-in-matrix-form |
Question: <p>I understand that the formula for time dilation is given as</p>
<p>$$T = T_0\gamma = \frac{T_0}{\sqrt{1-v^2/c^2}}$$</p>
<p>Where T is moving with velocity <em>v</em> seen from $T_0$. Though, this is when an event is occuring, since the value for $T$ would in any case of $v>0$ be greater than $T_0$, me... | https://physics.stackexchange.com/questions/408604/time-dilation-formula-question |
Question: <p>In the twin paradox from what I understand both observer see each other's time dilated so they always believe that the other frame is younger. Finally because the space ship frame has to make many accelerations it results that he will be younger. However, what if the frame in the space ship doesn't have to... | https://physics.stackexchange.com/questions/411161/paradox-of-the-twins-in-time-dilation |
Question: <p>If you went at light speed, you would literally and instantly teleport from the sun to the Earth. Any slower would create the perception of time. In other words, we appear frozen to the light (or observer going at c).</p>
<p>Still, the light can never appear frozen to us. Its speed is always the same, so ... | https://physics.stackexchange.com/questions/422405/proof-that-an-observer-cannot-be-in-two-places-at-once |
Question: <p>Imagine an LC circuit in which the capacitor consists of two metal discs of area <span class="math-container">$A$</span> and spacing <span class="math-container">$D_0$</span> which is connected to a solenoid coil which for convenience has length <span class="math-container">$D_0$</span>, cross-sectional ar... | https://physics.stackexchange.com/questions/433230/what-is-the-behavior-of-an-electronic-oscillator-at-relativistic-speeds |
Question: <p>Special relativity implies the possibility of some apparently paradoxical situations, which can ususally be made sense of if one applies the theory rigorously. One of these is the car-garage paradox: a car speeds towards a garage which, at rest, is slightly shorter than the car. From the reference frame of... | https://physics.stackexchange.com/questions/436396/car-garage-paradox-with-just-one-door |
Question: <p>If the combined mass of an electron and a positron was approximately <span class="math-container">$1$</span> MeV/<span class="math-container">$c^2$</span>, then would the total energy of their annihilation be equal to <span class="math-container">$9 \times 10^{16}$</span> MeV? Why do we not multiply the re... | https://physics.stackexchange.com/questions/442709/rest-mass-of-electron-positron-would-be-the-same-as-their-energy-in-annihilation |
Question: <p>Suppose a space ship is traveling from star A to star B at some significant fraction of the speed of light. In the frame of the ship, the distance A to B is less than the distance in A and B's rest frame. Is it possible for the ship to quickly increase its speed so that in its frame the ship is then closer... | https://physics.stackexchange.com/questions/460049/length-contraction-scenario |
Question: <p>So the Lorentz Transformation formation equation are
<span class="math-container">$$x′=\gamma(x−vt),$$</span></p>
<ol>
<li>Does <span class="math-container">$x′$</span> and t represent time and position at one event(one instance) or do they represent two events- meaning is <span class="math-container">$x'... | https://physics.stackexchange.com/questions/466211/question-regarding-lorentz-transformation-formula |
Question: <p>Here I state and try to answer three variations of the twin paradox</p>
<p><strong>1) "Classical" problem, no acceleration, no turn around</strong></p>
<p>Consider the case where there's a stationary planet, and a moving spaceship moving at close to the speed of light, starting at the left going ... | https://physics.stackexchange.com/questions/467099/3-variations-of-the-twin-paradox |
Question: <p>You awaken on a deep space observing station. You do not know its acceleration history but right now there is no gravity and you are billions of light years from the nearest other molecules. A light-year-long series of high speed, high resolution video cameras stretches out left to right as viewed from you... | https://physics.stackexchange.com/questions/477472/is-length-contraction-and-time-dilation-symmetrical-between-non-accelerating-ref |
Question: <p>In <a href="https://medium.com/starts-with-a-bang/this-one-anomaly-is-driving-physicists-to-search-for-light-dark-matter-774ec0eb7023" rel="nofollow noreferrer">This One ‘Anomaly’ Is Driving Physicists To Search For Light Dark Matter</a>, what does Ethan Siegel mean by "The fact that there are no stationar... | https://physics.stackexchange.com/questions/496197/what-does-ethan-siegel-mean-by-the-fact-that-there-are-no-stationary-oscillati |
Question: <p>Consider an apparatus similar to that used in Michelson-Morley experiment kept in a frame (S') moving with a constant speed (v) to the right of an inertial frame (S).</p>
<p>The apparatus consists of a light source, a partially silvered glass (B) in front of the source and two mirrors facing B (at a lengt... | https://physics.stackexchange.com/questions/509553/how-can-two-different-inertial-frames-observe-two-different-events |
Question: <p><strong>[Question]</strong>
I recently read that two perpendicular Lorentz boosts equal to a rotation after a boost. Can anyone here show me an example of this happening? Thank you for your time and assistance!</p>
<p><em>Source: None - (not a homework question)</em></p>
Answer: <p>Here is an explicit ex... | https://physics.stackexchange.com/questions/515663/special-relativity-perpendicular-boosts-equaling-to-a-rotation-after-a-boost |
Question: <p>I was studying length contraction and it considered the following scenario.</p>
<p>A rod is moving at a velocity <span class="math-container">$v$</span> with respect to a frame <span class="math-container">$S$</span>. A frame <span class="math-container">$S'$</span> observes the rod stationary and thus me... | https://physics.stackexchange.com/questions/516209/how-will-the-length-of-a-moving-rod-change-for-an-observer-seeing-it |
Question: <p>In general, let us have a light emitting point A and two light absorbing points B and C, such that the three points fall on a straight line and B is somewhere between A and C. For simplicity, let us consider all photons emitting from A to travel along this same line in the direction of the points B and C. ... | https://physics.stackexchange.com/questions/531552/how-does-a-photon-decide-what-to-hit-along-its-path |
Question: <p>It's hard to get an intuitive grasp of the Lorentz transformations; I was wondering if the same mathematical formulas – hyperbolic rotation – appear under disguise in other physical systems. Note: I doubt there's a direct <em>mechanical analogy</em>, with a speed limit much lower than <span class="math-con... | https://physics.stackexchange.com/questions/541139/analogue-to-special-relativity-in-other-physical-systems |
Question: <p>Suppose, in inertial reference frame <span class="math-container">$F_1$</span>, observers A and B are at rest, each having torch, and are separated by some distance and we have put machine M at middle of A and B.</p>
<p>Machine M has light bulbs on both sides ,right and left, so that if it catches light f... | https://physics.stackexchange.com/questions/554156/simultaneity-and-special-relativity |
Question: <p>The question is extention of thought experiment proposed by Einstein of light pulses in a train cart called <a href="https://en.m.wikipedia.org/wiki/Relativity_of_simultaneity#:%7E:text=Einstein%27s%20thought%20experiments-,Einstein%27s%20train,to%20strike%20at%20different%20times." rel="nofollow noreferre... | https://physics.stackexchange.com/questions/569274/can-different-observers-observe-different-realities |
Question: <p>In the Feynman Lectures, he lays out how in special relativity, the mass is adjusted by a factor of <span class="math-container">$\sqrt{1 - v^2 / c^2}$</span> and then writes:</p>
<blockquote>
<p>For those who want to learn just enough about it so they can solve problems, that is all there is to the theory... | https://physics.stackexchange.com/questions/594901/why-does-feynman-say-that-is-all-there-is-to-the-theory-of-relativity-it-just |
Question: <p>Consider an inertial frame <span class="math-container">$S'$</span>. With respect to this frame of reference consider a system of <span class="math-container">$n$</span> particles. The <span class="math-container">$k$</span>-th particle has rest mass <span class="math-container">$m_{0,k}$</span> and it mov... | https://physics.stackexchange.com/questions/621603/energy-of-a-n-particle-system-in-special-relativity |
Question: <p>Let me take you through the logic in my head...</p>
<ul>
<li>In frame S, you have coordinate <span class="math-container">$x$</span></li>
<li>Transform to frame S' with velocity <span class="math-container">$v$</span> so the coordinate is now <span class="math-container">$x' = \gamma x$</span></li>
<li>Now... | https://physics.stackexchange.com/questions/635048/how-does-lorentz-transforming-forwards-then-backwards-stay-consistent |
Question: <p>This is a variant of the twin paradox. But having each of the twin astronauts take off in opposite directions and returning to meet such that all aspects of acceleration and velocity are the same. Both should observe the other’s clock being slow for the whole trip but when they meet they should have aged e... | https://physics.stackexchange.com/questions/657975/how-can-a-twin-travelling-astronaut-paradox-be-resolved |
Question: <p>In my introductory text about special relativity, I am told to consider the whole coordinate system as consisting of meter sticks (rods) joined by clocks. I am told to consider a light pulse which is used to synchronize the clocks, with each clock stopping when it receives the pulse and correcting for the ... | https://physics.stackexchange.com/questions/662666/what-is-the-meaning-of-clocks-and-rods-in-special-relativity |
Question: <p>There is no gravity. Two lasers, one in <span class="math-container">$(x, 0, 0)$</span> and the other in <span class="math-container">$(-x, 0, 0)$</span>, are motionless. Both of them are pointing upward (in z direction) toward circumference of a motionless disk. The disk will start moving upward in z dire... | https://physics.stackexchange.com/questions/687497/how-does-wigner-rotation-manifest-itself-in-3-forces |
Question: <p>Assume an event that happens at P=(ct:2,x:4) in some inertial frame of reference S. Assume a second inertial frame S' in standard configuration and <span class="math-container">$\beta=4/5$</span> (<span class="math-container">$\gamma=5/3$</span>). The Lorentz transform is:</p>
<p><span class="math-containe... | https://physics.stackexchange.com/questions/689301/understand-result-of-lorentz-transform |
Question: <p><strong>Context for this question:</strong> There is a famous thought experiment used to explain time dilation that uses two mirrors and a photon to set up a clock. The two mirrors are placed parallel to one another, and a photon is sent travelling perpendicular to the planes of the mirror, bouncing back a... | https://physics.stackexchange.com/questions/699949/how-does-the-principle-of-relativity-imply-that-photon-clocks-and-mechanical-clo |
Question: <p>Suppose a clay ball of mass <span class="math-container">$m$</span>, travelling at speed <span class="math-container">$v=\sqrt{3}c/2$</span>, collides with an identical clay ball that is at rest. They undergo a perfectly inelastic collision.</p>
<p>After performing the relevant calculations (using two sepa... | https://physics.stackexchange.com/questions/731793/relativistic-inelastic-collisions |
Question: <p>I am high school student. I want to read the articles of famous scientists. These articles must be in their original language and not edited in any way. For example, I want to read Special Relativity, which was published by Einstein in 1905. In the German language and with an exact copy from 1905. Where ca... | https://physics.stackexchange.com/questions/729882/how-can-i-read-articles-by-famous-scientists-for-free |
Question: <p>I am currently studying the <a href="https://en.wikipedia.org/wiki/Rindler_coordinates" rel="nofollow noreferrer">Rindler coordinates</a> </p>
<p><span class="math-container">$$T = x \sinh(a t) , \, X = x \cosh(at).$$</span></p>
<p>I am trying to understand the connection between the Rindler coordinates ... | https://physics.stackexchange.com/questions/440400/spacetime-diagram-in-rindler-coordinates |
Question: <p>If I understood well, in the special relativity </p>
<p>1- A stationary observer sees other moving observer's clock works more slowly than the stationary clock. </p>
<p>2- Motion is relative, the moving observer thinks the stationary observer is moving.</p>
<p>I cannot understand how it is possible then... | https://physics.stackexchange.com/questions/201700/symmetrical-twin-paradox-without-changing-direction |
Question: <p>I am trying to read of synchronization of two clocks in same inertial frame in special relativity. Suppose we have two synchronized clocks in an inertial frame placed at positions $x_1$ and $x_2$ in that frame. Suppose two observers at $x_1$ and and $x_2$ try to measure speed of some object moving in betwe... | https://physics.stackexchange.com/questions/203920/regarding-synchronization-of-clocks-in-special-relativity |
Question: <p>I'm sure this seems like a stupid question but I hope someone can try to explain it as if to a child...</p>
<p>This relates to Lorentz contraction. Why do objects in motion relative to the observer not get <em>longer</em>?</p>
<p>In the train example. A stationary observer is at the middle of a train car... | https://physics.stackexchange.com/questions/220921/why-do-objects-traveling-faster-appear-shortened-rather-than-elongated |
Question: <p>Apparently a bunch of people totally misunderstood my <a href="https://physics.stackexchange.com/questions/231505/what-happens-to-wheels-of-a-car-moving-near-speed-of-light">previous question</a> and choose to ignore the clarifying comments. Let me change the conditions to remove all the confusion.</p>
<p... | https://physics.stackexchange.com/questions/231614/lorentz-contraction-of-object-in-circular-motion |
Question: <p>My question is similar, if not identical, to <a href="https://physics.stackexchange.com/questions/214247/feynman-lectures-on-physics-the-michelson-morley-experiment">this one</a>, but I don't find the answer satisfying, given the context of experiment.</p>
<p>First, here is an outline my understanding of ... | https://physics.stackexchange.com/questions/238535/feynman-lectures-on-physics-michelson-morley-question-about-angle-of-light |
Question: <p>This is quite a naive question however I hope to learn from this - I had always learnt a light clock in a space ship is placed like so :</p>
<p><a href="https://i.sstatic.net/YK2wc.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/YK2wc.png" alt="enter image description here"></a></p>
<p>Tha... | https://physics.stackexchange.com/questions/240143/does-light-still-slow-down-in-the-direction-of-motion |
Question: <p>Extending on the <a href="https://physics.stackexchange.com/questions/241792/time-dilation-diagram-on-wikipedia">question about the time dilation on Wikipedia</a>, namely this diagram in the <a href="https://physics.stackexchange.com/a/241807/56376">accepted answer</a>:</p>
<p><a href="https://i.sstatic.ne... | https://physics.stackexchange.com/questions/244701/direction-of-the-lightbeam-in-srt-thought-experiments |
Question: <p><a href="https://i.sstatic.net/1tQFG.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/1tQFG.png" alt="Experiment seen from two different inertial frames."></a></p>
<p>Consider two very short light pulses emitted from the centre (C) of two mirrors A and B (as shown in the diagram).
From the p... | https://physics.stackexchange.com/questions/259199/relativity-paradox-with-mirrors-and-light-pulses |
Question: <p>Two ships of the same proper length $L$ move towards each other, as in the diagram below (which shows it in the reference frame where the ship at the left is at rest). The fronts (noses) are pointing to each other.</p>
<p><a href="https://i.sstatic.net/Dw0QB.jpg" rel="nofollow noreferrer"><img src="https:... | https://physics.stackexchange.com/questions/262076/special-relativity-is-this-a-known-paradox-or-one-at-all |
Question: <p>I am currently a 3rd year undergraduate electronic engineering student. I have completed a course in dynamics, calculus I, calculus II and calculus III. I have decided to self study a basic introduction to special relativity as it was not part of my physics syllabus and is not included in any of my other m... | https://physics.stackexchange.com/questions/277520/special-relativity-with-no-short-cuts |
Question: <p>One of the classic examples to describe that simultaneity is relative is the following:</p>
<p>"Imagine a freight car, traveling at a constant speed along a smooth, straight track. In the very center of the car there hangs a light bulb. When someone switches it on, the light spreads out in all directions ... | https://physics.stackexchange.com/questions/285760/relativity-of-simultaneity-issue-with-the-train-car-example |
Question: <p><a href="https://i.sstatic.net/GULKM.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/GULKM.png" alt="enter image description here"></a></p>
<p>In the above figure Observer A is detecting the events P and Q by sending and receiving lights to the continuous paths. Observer B is also trying to... | https://physics.stackexchange.com/questions/286536/a-question-about-the-relativity-of-simultaneity |
Question: <p>I will refer to this wikipedia page: <a href="https://en.wikipedia.org/wiki/Bell%27s_spaceship_paradox" rel="nofollow noreferrer">https://en.wikipedia.org/wiki/Bell%27s_spaceship_paradox</a>
and especially this diagram:</p>
<p><a href="https://i.sstatic.net/8KZdj.png" rel="nofollow noreferrer"><img src="h... | https://physics.stackexchange.com/questions/287428/bells-spaceship-paradox-special-relativity |
Question: <p>Please don't mark as duplicate. My specific question was not answered in other posts. And this question here <a href="https://physics.stackexchange.com/questions/289025/which-photon-would-win-the-race">Which Photon would win the race?</a></p>
<p>is also about neutrinos, electrons. </p>
<p>My question now... | https://physics.stackexchange.com/questions/289234/is-a-photon-going-through-a-center-of-mass-affected-by-time-dilation-more-then-a |
Question: <p>Set up: A moving train with two flash lights on the wall, a person in the middle of the train. A mid point on the tracks where second person/observer stands. Flash lights flash a light when mid-point on the tracks and of the train have the same coordinate in both frames of reference. Suppose 1D problem plu... | https://physics.stackexchange.com/questions/299459/analysis-of-simultaneity-in-special-theory-of-relativity |
Question: <p>The red dots shown below, are RF transmitters.<br>
Clocks are located nearby each of these RF transmitters.<br>
All spaceships are identical and thus have identical rocket engines.</p>
<p><a href="https://i.sstatic.net/nb4Sn.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/nb4Sn.gif" alt="ht... | https://physics.stackexchange.com/questions/310673/with-quad-spaceship-setup-will-rf-time-periods-between-all-ships-remain-the-sam |
Question: <p>I was doing a problem on relativity and I was thinking about the problem in terms of the postulates of Special Relativity. Special Relativity only considers motion in inertial reference frames and I was doing this problem over here; </p>
<p>Essentially, if I have a rod which is tilted at an angle (theta)0... | https://physics.stackexchange.com/questions/318013/relativity-and-a-rotating-rod |
Question: <p>I am trying to make sense of Fig. 2.12, page 23 of Introducing Einstein's Relativity (D'Inverno, Oxford University Press). There it goes:</p>
<p><a href="https://i.sstatic.net/wiLWO.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/wiLWO.jpg" alt="fIG.2.12, PAGE 23"></a></p>
<p>The book pict... | https://physics.stackexchange.com/questions/320581/time-lines-of-observers-meeting-each-other-doubts-about-their-graphical-repres |
Question: <p>I am reading the book "Gravity in a nutshell" in which the author talks about rotation in a plane and different frames, one rotated with respect to the other. The rotated frame is denoted with a prime. We are trying to find the matrix relating the differences of coordinates in both frame. It is s... | https://physics.stackexchange.com/questions/594933/rotation-matrix-and-referencials-in-relativity |
Question: <p>I'm just starting to learn special relativity, and I'm having trouble with the following concept:</p>
<p>In relativity, units of length and time of moving frame are related to that of stationary one through <span class="math-container">$$x’=\frac{x}{\gamma}\quad \quad \text{ and }\quad \quad t’=t\times \ga... | https://physics.stackexchange.com/questions/574856/in-relativity-if-units-of-length-contracts-and-time-dilates-then-does-unit-of-v |
Question: <p>I have a version of the twin paradox which I am completely stumped by. There is a similar question on the forum but this particular version is unanswered. I really hope someone a lot better at physics than me is able to solve it!</p>
<p>Imagine two twins (Max and Tony) which are accelerated at birth in two... | https://physics.stackexchange.com/questions/603880/how-can-i-resolve-this-version-of-the-twin-paradox-in-special-relativity |
Question: <p>In many relativity illustrations, it is mentioned that someone in a spaceship believes he is standing still and the observers are moving and vice versa. The example of a light-beam clock slowing down for an observer but not for the passenger of the ship is often how relativity is explained.</p>
<p>But if t... | https://physics.stackexchange.com/questions/611376/if-an-object-is-orbiting-another-body-dont-both-the-orbiting-object-and-an-obs |
Question: <p>I have a question regarding the concept of length contraction.
Consider a rod of rest length <span class="math-container">$L_o=x_2-x_1$</span> in frame <span class="math-container">$S$</span>. Now if we want to measure the length of the rod in <span class="math-container">$S^{'}$</span> i.e <span class="ma... | https://physics.stackexchange.com/questions/612498/why-do-we-take-measurments-of-the-end-points-of-a-rod-at-the-same-time-in-an-ine |
Question: <p>On the Wikipedia page for the Twin Paradox, the example lays out the perspective of each twin in turn. Both twins are portrayed as understanding the ship's velocity as v, and the travelling twin's sense of time is then explained by saying that the earth-distant star system, being in effect one giant object... | https://physics.stackexchange.com/questions/573254/dont-twin-paradox-explanations-imply-universal-velocity-time |
Question: <p>I am having trouble understanding how to apply the Lorentz transformation to a particle trajectory.</p>
<p>Suppose we have a body moving in one dimension in one frame where the position is given by <span class="math-container">$x(t) = f(t)$</span>. Then if we apply a Lorentz transformation with velocity <s... | https://physics.stackexchange.com/questions/578953/lorentz-transformation-of-a-trajectory |
Question: <p>In Special Relativity we solve the problem of the moving wire with an electrical current saying the protons inside the wire have a higher density: hence the wire is not neutral anymore (and we exchange a force caused by a B field with a force caused by an E field):</p>
<p><a href="https://phys.libretexts.o... | https://physics.stackexchange.com/questions/581380/what-happens-with-the-number-of-protons-inside-a-wire-in-movement |
Question: <p>Suppose a rod with length <span class="math-container">$L$</span> moving toward a hole whose radius is <span class="math-container">$L$</span>. The paradox is, from the ground frame, the length of the rod is contracted hence rod will fall into the hole. However, from the rod's frame, it is the length of th... | https://physics.stackexchange.com/questions/584984/compute-the-vertical-motion-of-the-rindlers-length-contraction-paradox |
Question: <p>A normal Lorentz coordinate problem might say:</p>
<p>At <span class="math-container">$t=t'=0$</span>, two coordinate systems <span class="math-container">$S$</span> and <span class="math-container">$S'$</span> have their origins coincide with the <span class="math-container">$S'$</span> system moving with... | https://physics.stackexchange.com/questions/584040/confusion-about-lorentz-coordinate-transformation |
Question: <p>Imagine a train moving with velocity v wrt a reference frame S, there is a clock in the rear and in the front of the train, and them are synchronized in the train reference, let's call this reference frame S'.
If you, the reference frame S, take a look simultaneously wrt your reference on the clocks, how w... | https://physics.stackexchange.com/questions/590415/about-relativity-and-train |
Question: <p><span class="math-container">$$\begin{pmatrix}
1& 0 & 0 & 0\\
0& \cos\theta & \sin\theta &0 \\
0& -\sin\theta & \cos\theta &0 \\
0 & 0 & 0 &1
\end{pmatrix}$$</span></p>
<p>See this matrix, it represents a rotation in the xy plane for the Lorentz tr... | https://physics.stackexchange.com/questions/590829/lorentz-transformation-and-rotation-matrix |
Question: <p>I googled that question and found this answer:</p>
<p><a href="https://www.quora.com/If-I-had-a-laserpoint-inside-a-very-fast-moving-spaceship-and-I-point-at-the-wall-in-front-of-me-normal-to-the-direction-of-motion-will-the-light-hit-a-bit-lower-due-to-the-speed" rel="nofollow noreferrer">https://www.quor... | https://physics.stackexchange.com/questions/591364/light-perpendicular-to-spaceship-constant-relativistic-speed-different-points |
Question: <p>Two light sources are at rest and at a distance D apart on the x-axis of some inertial frame, O. They emit photons simultaneously in that frame in the positive x-direction. Show that in an inertial frame, O', in which the sources have a velocity v along the x-axis, the photons are separated by a constant d... | https://physics.stackexchange.com/questions/590998/two-light-sources-are-a-distance-d-apart-show-that-in-an-inertial-frame-o-the |
Question: <p>In time dilation, does clock really run slow when it’s in high speed? Is that means the mechanical parts of the clock run slow?
Or , It’s just the other inertial observer who thinks that the other one’s clock is running slow.(because the successive light signal is taking more time to reach the destination)... | https://physics.stackexchange.com/questions/592924/does-clock-really-run-slow-inside-a-high-velocity-rocket-ship |
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