Relativity

suppose in thought experiment there are two cabins , one cabin is plaed at rest in gravitational field while the second cabin is accelarated in direction from bottom to ceiling with acceleration g.. In both the cabins elastic string is attached to he ceiling.To the ewn of the spring in both the cabins certain mass is attached..The spring will be stretched in both the cabins but with difference that the extent of stretching will not change with time in the cabin placed in gravitational field while the extent of stretching will go on increasig with time in the accelerated cabin . It is so because the spring is attached to cabin hence its velocity and the velocity of t…

I have recently heard of something called a Tipler cylinder, which allows time travel to the past. How is it possible for something to create time travel to the past, according to our current understanding of general relativity? Time is dilated by a factor of [latex]\frac{d\tau}{dt}=\sqrt{g_{00}}[/latex] in general relativity, so how is it possible to make the factor negative?

I believe that Einstein himself had serious reservations about the notion of Minkowski spacetime, dismissing it as "superfluous learnedness", before adopting it as a significant foundation stone in his General Theory of Relativity. The idea that a massive body causes spacetime to become curved has always seemed odd, but that doesn't stop many people accepting it without question. In fact to question it might be seen as a form of blasphemy to some. But how can a massive object cause something which is itself massless to become curved. In fact, one could see spacetime as simply a mathematical device without real existence at all. Does anyone else f…

If Einsteins special relativity states that the speed of light is the same for everyone if you are traveling at a constant velocity, then this tells me that the universe, or all of the galaxies can't be accelerating away from each other, because that would mean that we all are accelerating. It's my understanding that special relativity has been tested and proved many times. So why is it still believed that the universe or the galaxies are accelerating? Any thoughts?

I know that it is technically impossible to reach the speed of light since the mass of the object traveling would reach infinity. Despite this if it were possible, would there be some sort of theoretical equivalent to a sonic boom that would occur? Since sonic booms are formed when sound waves can't catch up with an object, could the same happen with light waves? Would it look like an immense burst of light in the sky?

In special relativity, nothing is able to travel faster then the speed of light. However, if we imagined something traveled faster then light, strange consequences arise. For example, in special relativity, time is dilated by a factor of [latex]\frac{d\tau }{dt}=\sqrt{1-\frac{v^2}{c^2}}[/latex] When the velocity is greater then the speed of light, the time dilation factor becomes imaginary. What exactly would it mean if the time dilation factor was imaginary? What would be observed by a stationary observer if an object did travel faster then light?

According to the theory of reletivity, time dilates around the speed of light. How about if the point where time dilates is not as close to the speed of light, and it only seems like that light is 299 792 458 m/s because the light is going faster/close to the dilation point so that time slows down? So, relatively time seems faster than it really is!?!?

Hi I am simply wondering if it is possible to manipulate time in anyway. Could we slow it down? If we were able to acomplish time travel would we really see our future selves? Say I went to the future 10 years to see my-self. I couldnt because I would have moved my present to the future making by last present my past and hence forth really just moving myself through time alone without actually having a futue self to meet. I would not he myself because I am no longer in my last present aka past. I would have to clone my self to do so, right? What do you think? What would really happen?

How to define a level of danger of acceleration in gravitational field and without gravitational field?

so I don't know much about spacetime or physics in general but I'm watching a Nova video on the illusion of time. On Earth, if you are closer to the ground time will move slower for you. Time will move faster for you if you are higher up relatively from the ground. Why does this happen?

suppose two isolated heavy masses in space move towards each other will the path followed be straig ht line joining the centres of two masses or curved path?

A simple question: has it ever occurred to anyone that at the sub-atomic scale accelerators have confirmed both mass increase and time distortions. If that were true, then as an object moved at a Relativistic Speed, then the atoms/nuclear particles on that object would increase in mass and the Bosons (very particularly the Gluons - the Strong Nuclear Force particles) would slow. The time distortions occur in General Relativity as well, and because the energy for any slowed Boson would have to go somewhere, the nuclear particles would increase in mass. So more complex atomic cores would absorb energy and break up - into simpler elements. In re-uniting energy and matter…

Suppose we are in deep space in a rocket. We don't accelerate, we experience no significant gravity forces and we don't rotate. Ten (10) lightyears apart from us there is an other rocket (called B) wich is at a stationary distant and direction to us. We receive a clocksignal from B. We want to go to B so we accelerate towards it. Now the following two statements concerning the speed of the clocksignal we see from B during acceleration: 1- Due to non-relativistic-Dopler effect we see the clocksignal from B going faster (what I'm saying is that if there were no relativistic effects, then on arrival at B, its clock would have gained 10 years due to its original distance) …

How do objects get shorter? Do they get shorter beginning from the point which is towards the direction of the object's displacement to the opposite end of that point on the same object? If a car was driving forward extremely fast, then the car will get shorter at the front and back? So what about the top and bottom? Which raises the question, is it possible for something to move in all directions at once without splitting itself up (Does this deal with the uncertainty principle about inability to locate exact position and movements of electrons?)? Also, is the decrease of an object's length a proportional decrease based on the object's stable length or is it a c…

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I am not sure what would happen if there were multiple lines of infinite clocks where each line of clocks was at rest in an inertial frame. each line of clocks is syncronised so that you can tell what time it is in each inertial frame from any position. I realise that in SR each inertial frame that you would see the others going slower, but wouldn't that create a paradox? a clock in inertial frame A would read the year 3000 and see a clock in inertial frame B as having the year 2000, and the clock in frame B would see the clock in frame A as having the year 1000 3000 = 1000? thats a paradox right?

I think that the assumption of standard simultaneity in SR is unnecessary, and that apparent simultaneity works just as well, and improves SR. It is explained here: http://vixra.org/abs/1304.0023 Abstract: We consider a model of special relativity in which standard simultaneity is replaced by an alternative defined per observer by the direct appearance of simultaneity. The postulates of special relativity are interpreted to permit it, using a corresponding measure of distance chosen so that the measurement of lights speed remains invariant with a value of c. The relativistic Doppler effect and Lorentz transformation of time are derived from direct observati…

I am obviously having some difficulty in my interpretation of Special Relativity as I am continuously mentally defeated by Dewan and Beran's interpretation of what is going on in this thought experiment referred to as Bell's spacehip paradox. I cannot in my mind avoid the temptation of assuming that the spatial distance between accelerating spaceships should also experience lorentz contraction. Apparently according to Dewan and Beran, it doesn't. Could someone enlighten me on why it doesn't?

I am trying to get grip on the special relativity theory and therefore I have created a thoughtexperiment. Would you be so kind to tell me what mistakes I have made? Imagine the following: There are 3 spacestations (A,B and C) far out in space, not experiencing any apparent gravitational force. These spacestations keep the same distances and angles to each other. A, B and C form an isosceles triangle. The distance between A and B, and also between A and C, is 70 lightyears (ly). The distance between B and C is 14 ly. A, B and C have "synchronised" their clocks. This meaning: A has send a signal to B and C saying "it is now 1-1-2015" (day-month-year) and on arrival…

Just a observation. While I can see special relativity being known as a archaic incorrect form. Maybe historical reference? Something that might be useful to learn before general relativity? I do not see any benefit from it being taught in this day and age. Are there really scientists who still believe gravity is a force? ?!?

As per the relativistic equation when v approaches c time dilation approaches infinity. But theoretically how far could this go? If time is dilated close to infinity it will cross the age of the universe. (relative to the big bang). Then what would happen at the event horizon of a black hole where the gravitational shear forces are sufficient to produce such an event? Please advise.

The title should have been: "Is physics invariant under global regauging of c?" The geometrical constant relating dimensions of time and distance is c=~300,000 km/sec. Are the laws of physics invariant under regauging of c; that is [math]c \leftarrow c' = b c[/math] where b is real scalar? I'm sure there's something obvious I'm missing.

As I understand it, the continued acceleration due to dark energy results in a metric with ever larger components of tension. At some point the tension should be in the order of magnitude of the strong force holding the quarks of both bosons and mesons together. How would the physical situation appear?

Do I have this right? A completely antisymmetric tensor or type (0,k) on a k dimensional manifold in orthonormal coordinates may be expressed as a scalar times the Levi-Civita symbol, [math]\epsilon_{\mu \nu \rho \sigma}[/math]. Under a general linear transformation, is the result also a scalar times the Levi-Civita symbol?

Can anyone help explain whether gravity slows light going directly up or down a gravity well over an extended (not infinitesimally small) path, if possible using the two uploaded Minkowski diagrams of linear acceleration to help a student of Special Relativity understand the answer? For figure 1, consider two ships that begin at rest in the lab frame: Rear at x=0.5 and Front at x=1.0. Simultaneously, each flashes a light toward the other and begins to accelerate at a constant proper rate (Rear at a=2, and Front at a=1). These assumptions ensure that the ships maintain their proper distance in their own frame and that lines of simultaneity for the ships in their own…