Physics-Special Relatvity-Twin Paradox

Twin Paradox

Data Does Not Match Special Relativity Time Dilation
Open Letter On Twin Paradox
Open Letter On Special Relativity
Sign Open Letter
Survey Questionnaire
Mainstream Response
Debate Methodology
Can't Be Due To Relative Velocity
Can't Be Due To Turnaround Acceleration
Time Difference Accumulation Is Not Indeterminate
Dingle's Question
Blog Discussion
Two Step Argument
Three Step Argument
Two Step Argument #2

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This page is directed toward any student or young man or woman who plans to study, teach or use Special Relativity, with the latter including not only physics, but also areas such as astronomy, cosmology, GPS, NASA and VBLI. Any such student deserves, indeed owes it to themselves, to get a straight answer to the Twin Paradox and to Dingle’s follow-on question about Special Relativity itself as discussed in the Report page. The student should read the Open Letter, Report and Mainstream Response pages preferably before reading this page. Also, students should read the relatively new Open Letter On Special Relativity page, with special attention to the Time Dilation questions, and the Data Does Not Match Special Relativity Time Dilation page. [We use the term "mainstream" as a shorthand for all professors who support currently accepted theory including the contention that there's no problem/paradox in the Twin Paradox.]

The next two sections below invite students to consider the issues and problems of the various, conflicting solutions to the Twin Paradox published in mainstream journals. The third section outlines those proposed mainstream solutions. The Counterarguments section gives a brief overview of the problems associated with the various categories of proposed mainstream solutions and has links to four pages that provide more detail on those problems and discusses how the student can probe those solutions to see if they make good physics sense.


Unless the main reason for your choosing your field is to pull down a paycheck, you should make sure that your life’s work is going to be as productive and meaningful as possible. It’s probably impossible to know the absolute TRUTH. However, if you accept misinformation while more accurate information lies open to you just because you don’t want to ruffle any feathers, then ultimately you’ll regret it. Imagine spending years and even decades on, for example, ironing out the problems in the currently accepted Cosmology model only to find that ideas that were clearly set out by any number of respected physicists during the 20th century completely obsoleted your work – that your work was obsolete before you started it, that your work wasn’t even a step in the right direction, but rather your work went down a distracting dead end that blocked progress in your field.

For example, suppose you accept Special Relativity as directly describing the physics of the real world and you work on a cosmology model. You gather data about the relativistic Doppler shift for light coming from galaxies billions of light years away and you ascribe that Doppler shift to the relative velocity of the local telescope to that distant galaxy and compute how fast they’re separating. Noting that it’s hard to pinpoint the physical relevance of relative velocity between two objects separated by billions of light years in space and billions of years in time, one might consider a non-Special Relativistic interpretation. Assume that the speed of light in vacuo is c for some unique frame (e.g., the CBR frame) where the medium for light is at rest. Then, the physical interpretation is that the Doppler shift is a function of the difference between the velocity of the distant galaxy with respect to the unique frame at the time of emission and the velocity of the local telescope with respect to the unique frame at the time of reception. Hence, the physical interpretation is completely different and would lead to a very different cosmological model.

Conversely, let’s examine the potential downside for careful analysis of this topic. Let’s imagine that you, after studying the critics’ arguments and currently accepted theory, find a solution to the Twin Paradox that is consistent with currently accepted theory. Will you have wasted your time? No, because:

- You will have learned to think for yourself

- You will have done what no other physicist has done


1) Read the pages on this site and ask your professor probing questions. Don’t just bow to authority, make sure the answer(s) make sense to you.

2) Ask your professor to take the Twin Paradox Challenge. He/she is likely to refuse. If so, send the refusal excuse to us. Press the issue and make sure the refusal doesn’t just represent a fear of exposure. If he/she accepts the Challenge, we’ll ask questions to see if the solution is viable.

3) The Internet is a very powerful and empowering tool for those who wish to air a topic that the powers-that-be would prefer to suppress. A common blog should be used to unite all students who want a serious, open, candid analysis of questions about currently accepted theory. A blog page is now available for discussing the Twin Paradox - click on the Blog Discussion page link in the navigation bar in the top left hand column of this page..


Students are normally just taught currently accepted theory and this is understandable as there is a lot to learn. However, explicitly or implicitly, this tends to teach the student that currently accepted theory is THE TRUTH and all reasonable people agree with it. The history of how theory evolved and the questioning of that theory tends not to be covered. However, the history of the mainstream position on the Twin Paradox, even forgetting the critics, should give rise to some open mindedness and even concern regarding what is taught about the Twin Paradox and the interpretation of Special Relativity.

Not only has the mainstream "consensus" position on the solution to the Twin Paradox shifted several times, but there has consistently been many mainstream professors who have thought the current "consensus" solution was wrong. As discussed in the Mainstream Response page, there is currently an unwillingness to endorse or rule out any of the prior, mutually exclusive solutions, but rather only vague statements are given along with the claim that one cannot determine the "when-where-how" of the net proper time difference (NPTD) accumulation. When such loose ends have appeared before in physics, they have been harbingers of future paradigm shifts and great progress in physics.


There are more than a dozen arguments that have been published claiming to reconcile the Twin Paradox with currently accepted theory. A common flaw in most of them is mixing observed time with proper time. One can show that it’s not inherently contradictory to OBSERVE symmetric “time dilation”, however, the key question is “What’s the physics (the how, when, where) of NPTD accumulation?” When discussing the NPTD, one should limit the discussion to proper time between well defined events.

A second common error is using accepted equations with implied physics that is at odds with the standard physics meaning associated with those equations. For example, reconciliation arguments often use the time dilation equation which is a function of relative velocity, but use the equation with the implied/tacit assumption that the velocity is with respect to a special (unique) frame.

Five general categories and cases of reconciliation arguments are discussed briefly below. More in depth examination of some of the items below are given at Debate Methodology, Can't Be Due To Relative Velocity, Can't Be Due To Turnaround Acceleration and Time Difference Accumulation Is Not Indeterminate. Also, to see the consequences for Special Relativity of not being able to resolve the Twin Paradox using time dilation, see Dingle's Question page

a)    The net proper time difference (NPTD) accumulates smoothly during the constant velocity segments and half accumulates during the outbound segment and half during the inbound segment: Einstein’s original claim of the NPTD being caused by relative velocity and time dilation falls in this category. If one just looks at a single Twin Paradox scenario, everything looks fine. However, if one uses this approach consistently for two scenarios and reverses the roles of the two frames for the outbound segments, one is lead to an obvious contradiction. Einstein saw this and abandoned his original claim. Note that the logic that showed the flaw in the original claim also applies to ALL explanations in this category

b)    The NPTD accumulates in the turnaround acceleration: This approach encounters many problems. The period of acceleration can be made arbitrarily small compared to the constant velocity segments. Hence, a huge jump in NPTD is claimed to occur between two events that are separated by a vanishingly small amount of proper time for the traveling twin. Related to that, one can have multiple Twin Paradox scenarios where the physics parameters of the turnaround acceleration are virtually identical, but the claimed effects are alleged to differ by many orders of magnitude. Also, since the turnaround occurs in the “middle” of the scenario, the NPTD is not known until sometime after the turnaround has completed. So if instead of going all the way back to the original starting point, the traveler comes to rest in the original frame after or before that starting point, the NPTD will be greater or smaller than what is predicted in this approach. In addition, accelerationless scenarios are supposed to have basically the same NPTD as those with turnaround acceleration, hence, the turnaround acceleration per se would seem to contribute a vanishingly small amount of the NPTD. Data from accelerators also indicate that proper time loss is a function of velocity and not acceleration per se or virtual gravitational fields. There are other powerful counterarguments to this category.

c)     Relative Simultaneity: Reconciliation arguments employing relative simultaneity fall into the a) or b) categories, but are worth a quick look. Basically the claim is that the difference in what the twins observe/calculate as being simultaneous causes the NPTD. This is a good example of erroneously mixing observed time with proper time. This difference in what is seen to be simultaneous doesn’t seem to provide any physical mechanism for changing accumulated proper times. If one reset one’s clock depending on how one’s view of simultaneity changed or differed, then that would affect his clock’s reading, but even there that does not change proper time accumulation.

d)    NATURE OF SPACETIME OR KINEMATICS OF SPACETIME: This is probably a valid explanation of the NPTD, however, it is very vague and as stated doesn’t reconcile the NPTD with currently accepted theory. What’s needed is some specificity about what characteristic or property of currently accepted theory’s spacetime and/or kinematics is being referenced. Despite multiple requests no such specificity has been forthcoming from those who favor this “solution” - in fact, all likely currently accepted theory candidates have already been tried and abandoned.

e)     Cannot Tell How NPTD Accumulates: This is the new, in vogue response to the question, “How does the NPTD accumulate?” We agree that, in the context of currently accepted theory, one cannot describe the physics of how the NPTD accumulates. The disagreement is that the mainstream contends that the answer to that question is inherently unknowable or meaningless. Whereas we contend that the answer is knowable and straightforward, but it requires the construct of a unique (physics) frame where velocity with respect to that frame causes clock retardation.

Don't Be Put Off

Often a physics professor will try to avoid questions on this topic with something like:

a)     “Asking that question shows you don’t understand Special Relativity!”: This is done without articulating what was misunderstood or how it should have been understood instead. Don't be intimidated - this device has been used on professors who had clearly analyzed the theory and the paradox more deeply than the relativist and who articulated the problem/contradiction quite accurately. After attempts to use Special Relativity were abandoned, “You don’t understand General Relativity!” became the new catch phrase. It would have been nice if they added, “I guess Dingle and other critics did understand Special Relativity” at the very least.

b)    “Read Jones’ book …”: This is vague enough to be difficult to disprove. You need to press for a specific answer.

c)     “This is settled science, I’m too busy, just read the textbook”: They may well be very busy and/or reluctant to tackle this topic. However, if you’ve researched this topic and have a probing question and are ready for the standard replies, the professor, as teacher, owes you an honest answer.

d)    “I have to do my taxes”: One of us received this response when the contradiction in the professor’s position became apparent to him. It would have been OK for him to go do his taxes, if he’d have ever returned.

Spacetime physics is overdue for a paradigm change. Who's going to make it happen?

Science Revolutions: J. T. Wilson, a geologist involved in the shift to continental drift and a student of the history of science, wrote the following about revolutions in science, "In each case the great event marking the revolution revealed contradictions and introduced problems which the old system could not resolve, leading to a period of confusion. For the most part it was not experts but rebels, outsiders and interlopers from other fields of science who suggested the need for a revolution and produced the evidence supporting it. Thus most geologists continued to oppose the concept of continental drift long after Wegener (a meteorologist) had championed it, after physicists had provided key evidence supporting it and after many of the public had accepted it.

So, far from welcoming new ideas, the establishment who had the most to lose, clung for as long as possible to the old, justifying their position by questioning the new data, discrediting those who advanced them, and trying to patch up the old theories. In these endeavours they frequently found themselves supporting quite illogical positions. Before each revolution was accepted, the state of the subject had become chaotic, but each solved many problems so that the ensuing periods were times of great scientific progress and material benefit.

[Continental drift was first suggested by Abraham Ortelius in 1596, but was not accepted by geologists for 350 years until around 1950 and then it was soon further refined by the construct of plate tectonics.]

1) J. T. Wilson, Nature 265, 196 (1977)
as quoted by I. McCausland, A Scientific Adventure: Reflections on the Riddle of Relativity, pg 173 (Aperion 2011)


The same logic that forced Einstein and relativists to abandon using Special Relativity's time dilation as the cause of an asymmetric net proper time difference in the Twin Paradox also precludes using time dilation to explain any asymmetric net proper time difference. Since GPS, Hafele-Keating and much other data shows that there is asymmetric clock retardation as a function of velocity with respect to a unique (local) frame - another explanation, outside of relativity, must be found to explain this velocity dependent data.

It's important for students to understand these straightforward facts and also for students to get their physics professors to answer the questions on Time Dilation on the
Open Letter On Special Relativity page.

See the original Twin Paradox Open Letter

Online References

H. Dingle, Science at the Crossroads (Martin Brian & O'Keeffe, 1972), p. 129. Downloadable from the World Science Data Base - Click Here

T. Van Flandern, Aperion, 10 #1, 69 (2003) - see paper

C. S. Unnikrishnan, Current Science, Vol. 89, No. 12, p. 2008 (2005) – see article

F. Selleri, LA RELATIVITA' DEBOLE La fisica dello spazio e del tempo senza paradossi (Melquiades, Milano 2007-2010) [The online English version, "Weak Relativity", click to view]

G.O Mueller, 95 Years of Criticism of the Special Theory of Relativity (1908-2003); AVAILABLE ON LINE:
- English Translation

- English Version of Catalogue of Errors for Both Theories of Relativity (Translator Rothwell Bronrowan)

- Absolute Magnitude of the Special Theory of Relativity Chapter 9 – The Thought Experiment (Translator Rothwell Bronrowan)

- International Reception of GOM Project

- Original German Version

European Site 1

European Site 2 (In German)

G.O Mueller, Max Planck und der Verrat an der Wissenschaft [In German with computer translation available.]

L. Essen (Prof. Lord L. Essen, known as the "Time Lord" as he was the acknowledged leader in time measuremnt for his era), Relativity- Joke or Swindle?


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Physics-Special Relatvity-Twin Paradox
Last Modified: Friday, April 10, 2015
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