Talk:Special relativity

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Discussion of Postulates

The section on the postulates of Special Relativity seems to need some rethinking. In section 1 of his original 1905 paper Einstein states the first postulate as "The laws by which the states of physical systems undergo change are unaffected, whether these changes of state be referred to the one or the other of two systems of coordinates in uniform translatory motion." The second postulate states the invariance of the speed of light. These seem clear enough and we expect that the Lorentz transformation will be derived from them. In Section 3 he derives the Lorentz transformation from two postulates, first that the speed of light is invariant and second that the relation between the observers is symmetrical. There is no mention of the invariance of physical laws; the invariance of the speed of light gets as far as the LT with an arbitrary constant multiplier, and the symmetry postulate settles its value as unity. In section 6, Electrodynamical Part, he shows that the equations of electrodynamics are invariant with respect to the Lorentz transformation just derived, so the laws of physics may be a consequence of the LT but are not used as a postulate. This seems to be a very common mistake; none of the derivations of the LT I have seen use the invariance of physical laws as a postulate.ColinG 03:53, 26 April 2013 (UTC)

To Colingordon (talk · contribs): The invariance of physical laws is needed to show that everything in physics (not just electromagnetism) is preserved by Lorentz transformations. It is not the derivation of LT that requires the full power of the first postulate, rather it is the application of LT which requires that full power. JRSpriggs (talk) 09:19, 26 April 2013 (UTC)

Special Relativity is Wrong!

Two twin boys staying on two inertial reference frames with a constant relative speed will never find the other boy is younger than himself as they are at completely symmetric positions. This twin paradox actually denies the existence of time dilation as predicted by special relativity. Here is my paper proving the contradiction: Special Relativity Contradicts to ItselfXinhangshen (talk) 11:21, 7 July 2013 (UTC)

Whatever validity you might feel that your results might have, this is not the forum in which to self-publish. An encyclopaedia must be compiled from secondary sources. — Quondum 14:23, 7 July 2013 (UTC)

They are not in symmetrical positions since the travelling twin undergoes acceleration and deceleration which the stay-at-home twin does not. It's all explained in the twin paradox article. MFlet1 (talk) 11:44, 23 July 2013 (UTC)

"How far can one travel from the Earth" section inconsistent?

The final example indicates 28-year trip is sufficient to reach 2 million light years (Andromeda) but earlier examples seem to take longer at the same acceleration to reach only 148,000 light years. What am I missing?--Jrm2007 (talk) 08:50, 17 October 2013 (UTC)

140,000 lyrs is for a round trip: 10 years accelerating, 10 years decelerating, turn around, repeat. 28 years to the Andromeda is one way. — Reatlas (talk) 09:31, 17 October 2013 (UTC)

Even though some authors quoted round-trip and others one-way, can someone convert all of one to the other, or simply remove some of them? Maybe drop the round-trip examples; It's interesting enough that one could reach andromeda in one's lifetime, regardless of whether you (or your children) come back. Coming back is different because you'd be coming back to an earth that had aged hundreds of millions of years, in which time humans had presumably evolved into god-knows-what or gone extinct. DavRosen (talk) 18:16, 5 November 2013 (UTC)

Time, Proper time, and Standard time

It is useful to understand the mutual relation between the above-mentioned three closely related quantities, time, proper time, and standard time, more closely, which may be relevant for this article, at least it may be helpful for understanding:

As I see it at present, the standard time is defined by the "National Institute of Standards and Technology" of the country in question, ideally as the proper time of a certain free-falling atom (i.e. the velocity is exactly compensated by the local gravity forces, see General Relativity). The corresponding "ticks" of this time correspond to the periods of the corresponding quantum radiation of this atom.

This standard time is then propagated from the institute to railway stations, airports, and elsewhere. Finally this standard time also corresponds to the time of the watches, the passengers of Einstein's "fast trains", or "fast aircrafts", may carry on their arms, if they are sitting at rest on their seats in the vehicle. In particular this standard time, ideally also the time presented by the watches, corresponds to Einstein's $\mathrm {d} t,$ i.e. to the (external) clocks on the platforms of the railway station, and not to the (internal) "proper time" $\mathrm {d} \tau$ of the well-seated passengers in the train or airplane. In fact, a re-standardization from $\mathrm {d} t$ to the last-mentioned $\mathrm {d} \tau ,$ according to $\mathrm {d} \tau =\mathrm {d} t{\sqrt {1-(v^{2}/c^{2})}},$ would show only a slightly lower result, corresponding to some kind of Hafele-Keating experiment, since $v\ll c.$ But for $v\to c$ the internal quantity $\mathrm {d} \tau$ would diverge according to $\gamma .$

Maybe you would like to comment on this, e.g. for my own better understanding? - With regards, Meier99 (talk) 17:17, 5 November 2013 (UTC)

Perhaps you could try the wp:reference desk/science. This is where we discuss the article, not the subject—see wp:talk page guidelines. Good luck. - DVdm (talk) 10:58, 6 November 2013 (UTC)

The Earth is not an inertial frame of reference. So there will necessarily be distortions involved in any system of standardized time on Earth due to its rotation, revolution about the Sun, and the Earth's gravity. JRSpriggs (talk) 08:38, 7 November 2013 (UTC)

Wave-Theoretical-Insight into the Relativistic-Length-Contraction, and Time-Dilation of Super-Novae light-curves

In a recent paper, titled: "Wave-Theoretical-Insight into the Relativistic-Length-Contraction, and Time-Dilation of Super-Novae light-curves"; published in Advanced Studies in Theoretical Physics Vol. 7, 2013, no. 20, 971 - 976 http://dx.doi.org/10.12988/astp.2013.39102 ; Hasmukh K. Tank has attempted to understand Relativistic Length-Contraction and Time-Dilation, in terms of Fourier Transform. This may be a bigining of unification of Relativity with Quantum-Mechanics.180.87.227.236 (talk) 08:34, 12 February 2014 (UTC)

The limitations of Special Relativity

The postulates of SR refer to inertial reference frames (in which the speed of light is identical). On this basis Einstein predicts the observation of length and time units in a second IRF from the observer's IRF by means of measuring rods and clocks. Einstein therefore assumes that the dimensions of an IRF are some-how transposed to matter. I do not see how this assumption is justified, and without justification the whole theory fails. Furthermore, even if this assumption was found to be correct it implies that SR applies only to inertial bodies--that is bodies with absolute zero acceleration. No such bodies exist in the Universe. I am aware that the supporters of SR apply the theory to bodies of low acceleration but this cannot be justified. For example it accepts that no relativity theory exists which applies to bodies of higher acceleration, although one is obviously required. When that theory is discovered it might well apply also to bodies of low and zero acceleration and then SR will be redundant.RFNo (talk) 12:49, 17 February 2014 (UTC)