The special theory of relativity describes the motion and dynamics of objects moving at significant fractions of the speed of light.

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Possible mechanics based on the known symmetries in the nature (investigating rumor)

Somewhere I've heard about a relative new mathematical result regarding mechanics. Specifically, there is a list of the known symmetries of mechanics (both Newtonian and relativistic), i.e. different ...
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Why does the (relativistic) mass of an object increase when its speed approaches that of light?

I'm reading Nano: The Essentials by T. Pradeep and I came upon this statement in the section explaining the basics of scanning electron microscopy. However, the equation breaks down when the ...
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How is the classical twin paradox resolved?

I read a lot about the classical twin paradox recently. What confuses me is that some authors claim that it can be resolved within SRT, others say that you need GRT. Now, what is true (and why)?
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4answers
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Is there an upper limit on the radius of a rotating wheel?

Is there an upper limit on the radius of a real wheel which is rotating at an Angular frequency of $\,\omega \,$ along its axis, such that we just require a finite amount of energy to rotate it? ...
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Why does Minkowski space provide an accurate description of flat spacetime?

What is the chain of reasoning (beginning, of course, from observations about the universe) that leads one to predict that Minkowski space provides an accurate description of space-time in the ...
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How do you determine who is moving “faster” in relativity? [duplicate]

I suspect this question has a simple answer, but I can't get my head around it. The classic example of a person in orbit around the Earth at high speed experiencing a slower passage of time than the ...
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2answers
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What is the relative speed of two near-light speed particles headed towards each other?

I understand that nothing can move faster than light due to time dilation. I want to build upon my understanding of Einstein's theory of Special Relativity, so I came up with this hypothetical problem ...
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Velocity in frame $S$ and $S'$

If I take the Lorentz position transforms between two inertial frames, $S$ and $S'$ moving with relative velocity $u$ along a common axis (say $x-x'$), then: $$x'=\gamma(x- ut)$$ $$y'=y$$ $$z'=z$$ ...
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Special Relativity Second Postulate

That the speed of light is constant for all inertial frames is the second postulate of special relativity but this does not means that nothing can travel faster than light. so is it possible the ...
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1answer
90 views

4-velocity and 4-acceleration in instantaneous rest frames

I am trying to solve this problem: Consider a rocket moving relative to an inertial frame $\mathcal{F}$ , such that its worldline is given by ...
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0answers
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Confused about time dilation/length contraction [duplicate]

I have a following problem: A meson is generated $h$ meters above the earth's surface and begins to move towards the earth with velocity $v$. Its (proper) lifetime is $t_m$. What is $v$ if the meson ...
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1answer
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Proof that 4-potential exists from Gauss-Faraday field equation

This is a problem concerning covariant formulation of electromagnetism. Given $$\partial^{[\alpha} F^{\beta\gamma]}= 0 $$ how does one prove that $F$ can be obtained from a 4-potential $A$ such ...
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Person in a special relativistic frame observes light refract on a passing ship

The speed of light is the same in all frames of reference. But imagine a scenario in which you passed by a ship which had (B=.78), while your ship had (B=.94). While somehow being able to look through ...
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285 views

Is special relativity axiomatic?

Can special relativity be somewhat described by the following statement? If the speed of light is a universal constant, and if light can be placed in separate frames of motion, then time must be ...
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4answers
499 views

What will I see in this scenario? Will this be faster than the speed of light?

Let say there's a particle that is travelling very near the speed of light. Lets say I have a camera capable of filming this high velocity particle and I film the particle on my camera then I fast ...
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4answers
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Travelling faster than the speed of light

Let's say I fire a bus through space at (almost) the speed of light. If I'm inside the bus (sitting on the back seat) and I run up the aisle of the bus will I in fact be traveling faster than the ...
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2answers
68 views

Special Relativity Problem [closed]

I am having trouble with the following problem: Fry travels in a rocket ship towards Leela, at constant relative speed $v$: Fry is delivering a pizza, which in its rest frame stays hot for ...
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0answers
21 views

Derivation of proper acceleration in terms of rapidity

In the Wikipedia page for proper acceleration, an equation for proper acceleration in terms of rapidity is given as $\alpha = \frac{\Delta \eta}{\Delta \tau}$, where $\eta$ is the rapidity of the ...
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2answers
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Everything is a Photon

If we accept $E=\hbar \omega$, $p=\hbar k$, and $E^2-(pc)^2=(m_0 c^2)^2$, then we find $$(m_0 c^2)^2 = (\hbar \omega)^2-(\hbar kc)^2 = \hbar (\omega^2 - (kc)^2)=0$$i.e. the rest mass of any particle ...
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I think only x and t need obey Lorentz transform rule, other 4 vectors not necessarily true

Lorentz transformation aims at an invariant speed of light for all reference frames. Speed only involves x and t. Therefore it's reasonable to understand the Lorentz transform can act on spacetime ...
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2answers
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The wave equation in general relativity, special relativity, and Cartesian coordinates

The relativistic wave equation is $$\square\varphi=\rho$$ where $\varphi$ is the field, $\rho$ is the source, and $\square$ is the D'Alembert operator, defined by ...
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3answers
185 views

How to do calculation in relativity of simultaneity

I have great trouble in understanding simultaneity in special relativity. Let me illustrate it with a concrete example. Assuming there is a train, its two end points are $A$ and $B$, the length of ...
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Metric signature conventions: minus sign for $x^a$ or $x_a$?

Say I use the metric signature $(-+++)$. Then $\partial_a=(\partial_0,\partial_i)=(-\partial^0,\partial^i)$, but $\partial^a=(\partial^0,\partial^i)=(-\partial_0,\partial_i)$. The same goes for $p^a$ ...
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3answers
154 views

Question on energy mass conversion

I have a question regarding the energy-mass conversion. Well, when a particle starts moving with a speed comparable to that of light, its (relativistic) mass increases that means some matter is ...
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Relative Motion

I read the following: http://www.feynmanlectures.caltech.edu/I_15.html#Ch15-S4 "Now let us see what happens to the moving clock. Before the man took it aboard, he agreed that it was a nice, ...
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Dingle vs. Bondi: Twin Paradox Debate on BBC radio?

Herbert Dingle and H. Bondi debated the twin paradox on BBC radio before 1971. Does anyone have a link to the audio of this debate? thanks
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Does path integral and loop integral in a Feynman diagram violate special relativity?

Consider a correlation function between two points $A(x_1,t_1)$ and $B(x_2,t_2)$, we need to integrate over paths which could be infinite long. But the time length $(t_1-t_2)$ is finite, so if $A$ ...
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3answers
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What does a sphere moving close to the speed of light look like?

What shape does the viewer in a reference frame with $v=0$ perceive? I suppose that since the sphere moves in one direction only (oX only, not oY) its section would change into an ellipse, where the ...
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6answers
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Ion Drive Propulsion Top Speed

I would like to know if there is some formula / graph which would provide / show the efficiency of a certain type of propeller in space. Specifically, I'm interested in the acceleration attainable at ...
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3answers
510 views

Are length contraction and time dilation physical?

Are length contraction and time dilation real physical phenomena, or are they just a measurement issue?
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355 views

Twin Paradox: Still a Paradox?

Alright, so David Griffiths in his "Introduction to Electrodynamics" states that the Twin Paradox is not a paradox at all since the traveling twin returns to Earth. By returning to Earth, the twin had ...
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$E=mc^2$ resembles kinetic energy formula?

The simplest equation expressing mass–energy equivalence is the famous $E=mc^2$ where $c$ represents the speed of light. Compare this with $E_K = \frac{1}{2}mv^2$. Since $E=mc^2$ can be applied to ...
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How an accelerated object sees another accelerated body in special relativity?

Assume two objects are moving with a constant acceleration $a_1$ and $a_2$, which are the measured accelerations by respective object (or constant force being applied to each of the objects). My ...
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Why does GPS depend on relativity?

I am reading A Brief History of Time by Stephen Hawking, and in it he mentions that without compensating for relativity, GPS devices would be out by miles. Why is this? (I am not sure which relativity ...
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speed of the light emitted from a fast moving object [duplicate]

Would not speed of the light emitted from the front of the fast moving object be the speed of light + the speed of the fast moving object?
4
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1answer
142 views

Minkowski metric — why does it follow from the constancy of the speed of light [duplicate]

In all the sources I’ve been able to find, the Minkowski metric appears ad hoc, or is defined analogously to the euclidean metric. I’d love to see an argument why this metric (time coordinates ...
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2answers
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Confused about the concept of time and time dilation [duplicate]

I am having a hard time understanding what is time. If scientists define time as a multiple of caesium frequency, then time itself is dependent on motion, so what if I have a number of particles that ...
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2answers
240 views

Why the generators of boosts transform like a vector under rotation?

$$\left[J_i,J_j \right]=i\epsilon_{ijk}J_k$$ $$\left[J_i,M_j \right]=i\epsilon_{ijk}M_k$$ $$\left[M_i,M_j \right]=-i\epsilon_{ijk}J_k$$ where $J_i$ is the generator of rotation of Lorentz group, $M_i$ ...
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Disk spinning at the speed of light [duplicate]

Of course, I mean that the edge of the disk is traveling at the speed of light. This is a question that popped into my head a few years ago when I was learning about some basic relativity in high ...
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1answer
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Do hot objects moving at relativistic speeds slow down as they emit radiation?

In an astrophysics class I learned about the Poynting-Robertson effect, by which grains of dust orbiting a star slow down and eventually fall into the star. Every source that I have been able to find ...
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Newtonian Physics vs Relativity - the results [closed]

Does anyone have examples of the results calculated by using Newtonian physics vs the same ones calculated using relativity, compared with real measurements obtained in those experiments? Please ...
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2answers
76 views

How did Einstein come up with his postulates for Special Relativity using thought experiments on simultaneity?

In his popular book on relativity, in chapter IX, "The relativity of simultaneity", Einstein describes an experiment in which a flash happens simultaneously on A and B, as defined by the fact that an ...
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5answers
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What is the cause of Special Relativity [closed]

Why does special relativity exist? Via studying the outcome(s) of such relativity, one can end up with all the equations involved in special relativity. Thus one runs into things such as contraction, ...
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1answer
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Can I measure a journey time < 100 years on a 100 light year voyage? [duplicate]

So, I'm traveling to another star 100 light years away in my spaceship. This ship has a solar sail pushed by a laser beamed from my home star system, so can achieve a velocity close to c. It's also ...
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1answer
55 views

Pair Creation and Reference Frames

Ok, so I have a question about an example problem in my textbook (its long but not difficult to follow. My question is at the bottom after I outline the problem). Consider the situation below in frame ...
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1answer
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Red shift/blue shift: how would it appear to a fast-moving observer?

I've read sci-fi stories in which a spaceship crew, moving at some significant fraction of 'c', observes stars ahead as bluer, stars behind as redder, stars to port and starboard as...well, you get ...
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3answers
842 views

Chasing a photon [duplicate]

According to this article, the Theory of Special Relativity holds that if you were chasing a stream of light at half the speed of light, $c/2$, the light's speed relative to you would still be $c$. ...
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Did Einstein know about Michelson-Morley experiment?

The second postulate of special relativity deals with constancy of light in inertial reference frames. But, how did Einstein came to this conclusion? Did he knew about the Michelson-Morley experiment? ...
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1answer
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Distance and time measurement in the famous Superluminal Neutrinos Experiment

I tried to understand the technical aspects of the OPERA/CERN experiment, but apparently it takes some professional experience. Therefore I would like to ask someone better acquainted with such ...
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1answer
101 views

Question Regarding Lorentz Transformation

I have question regarding the following velocity transform formula: $$v_b = \frac{v_a - u}{1-uv_a/c^2}$$ $u$ here refers to the speed that one frame is moving relative to another. How do I decide ...