# Tagged Questions

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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### Small particle rotating around neutron star

First let me say I have read the article at "users.ictp.it › lns003 › Ruoff › Ruoff.ps.gz" about a small particles orbiting a neutron star and causing excitation of different modes of gravitational ...
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### Does sound waves pick up the speed of its source?

I googled the speed of sound and found that it only depends on the medium (just like the speed of light but with different parameters). I can't see how it doesn't pick up the speed of its source! I ...
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### Twin paradox on hypertorus [duplicate]

I will not describe the twin paradox again. But let's suppose we have two twins, one stationary and the other moving with uniform velocity $c/2$ for instance. And let's suppose that they live in a ...
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### Theory of relativity paradox? [duplicate]

I have seen the classical twin paradox before. It uses a twin stationary on Earth and the other traveling away and back. I have seen many contradictory solutions for it, some use general relativity, ...
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### Geometrically deriving Lorentz transformation from Minkowski diagram

How can we derive Lorentz transformation from a Minkowski diagram (like below image) by using only geometry theorems such as sines theorem and Pythagoras theorem?
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### Twin paradox with horns [closed]

I am trying to figure out if my conception of time dilation is correct. In order to avoid the acceleration-deceleration complexity in the traditional twin paradox statement, I came up with my own ...
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### Exercise 18b in Schutz's First course in GR

The question is as follows: Show that a timelike vector and a non-zero null vector cannot be orthogonal. So we have a timelike vector $\vec{A}$, s.t $\vec{A}^2<0$; and a non-zero null vector, ...
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### Special relativity and uniform circular motion

Suppose we have two observers A and B. A is in some inertial frame. B is undergoing uniform circular motion with some speed $v$ as observed by A. They each have a clock. My concern is with what A ...
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### Can a particle have an imaginary mass?

Now, I'm not very involved in the physical sciences, beyond some high-school classes - though I did listen to some college lectures for physics. I was reading "Do Tachyons Exist?" by John Baez, which ...
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### Is the energy of a collision of two photons the same as one photon hitting a 'wall'?

Special relativity says that the speed of ligt is always the same. So when a photon meets another photon he will encouter it with the speed of light and also the other one. But in case of a wall, the ...
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### Is there any description of a mechanism of curving of space-time fabric

Most of us know about famous line - "mass tells space how to curve and space tells mass how to move". There is quantitative description of the curving and its effects in Einstein's theory. Mass and ...
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### Conversion of energy to matter? [closed]

Now, this answer has sort of been asked before. But I haven't really found the answer that I'm looking for. Exactly what is the mechanism by which energy can be converted into matter? By "mechanism"...
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### Cold Solid Matter at the End of a Black Hole's Acceleration Disk?

Is it possible that black holes magnetic field are rapidly cooling matter using a type of magneto caloric effect and cold fusion creating new matter only possible with a black hole's gravity? A type ...
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### Up or Down? A Question about Relativity

The standard text discussion of the equivalence principle and the bending of light rays goes like this. We, as observers watch a glass elevator ascending. A light beam is fired from left to right. The ...
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### Where other frame observer will put new stick [closed]

my question is with relativity, if we draw two circle of same radii and fill the perimeter with stick (very small so it cover whole perimeter) now if we rotate a stick with veey high speed ...
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### Why does time stop its flow? [duplicate]

According to the "list verse" time gets to a pause when someone or something travels at the speed of light. But a question still lies in my mind, if time always travels forward and does not stop at ...
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### When does travelling at a fraction of the speed of light appear to the traveler as if they're going the speed of light? [closed]

If a spaceship is travelling to Proxima Centari, there is a fraction of the speed of light that would make the spaceship appear to reach Proxima Centauri in four years' time. What fraction of the ...
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### Decay of lepton into meson and neutrino using four-momentum

I'm learning about how to use four-momentums and am working through a problem involving the decay of a charged lepton into a charged meson and neutrino. The equation would be: $L^+ \to M^+ + \nu$ I'...
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### How do I know which observer is running the time faster or slower

Ok, I'm not a physicist, so I don't know if my question is silly (probably yes), but there is something in special relativity that I can't understand and I would really like it to be clarified. If ...
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### What makes things move in a universe with blocktime? [closed]

In a universe with blocktime the past, present and future all exist at the same time. But what makes it appear that for example my body is going from one movement ...
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### Why acceleration cannot vanish everywhere?

In attempt to introduce gr concepts When there are gravitational accelerations present, as for example in the gravitational field of the earth, the space cannot be the flat Minkowski space. Indeed, ...
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### Special Relativity problem - proper time interval

The supernova 1987A explosion in the Large Magellanic Cloud 170 000 light years from Earth produced a burst of anti-neutrinos ν ̄e which were observed in terrestrial detectors. If the anti-neutrinos ...