Philosophy and the Twin Paradox

The famous twin paradox of special relativity involves a scenario where one twin (he) rockets away from the home twin (her), coasts to a far-away turnpoint, reverses course, coasts back, and comes to a halt when they are reunited. At the reunion, both twins agree (by inspection) that she is older than he is.

There is no dispute about the outcome at the reunion. But physicists DO differ about what HE concludes about HER current age DURING his trip. One school of thought is that he says that she is ageing more slowly than he is, on both the outbound leg and on the inbound leg, but that he concludes that she instantaneously ages by a large amount during the instantaneous turnaround. But that conclusion can be shown to imply that he will have to conclude that it is possible for her to instantaneously get YOUNGER when he changes speed in certain other ways. THAT result is abhorrent to many (maybe most) physicists. The most extreme reaction is to conclude that simultaneity at a distance is simply a meaningless concept. Other physicists react by embracing alternative simultaneity methods, that don’t result in instantaneous ageing (either positive or negative).

So what does the above have to do with philosophy? For many physicists, there is no place for philosophy in special relativity. Philosophical arguments are usually banned on physics forums. But philosophy has always played a role in my thinking on the subject, even though I’m a physicist, not a philosopher (and I have only a VERY limited knowledge of philosophy). Philosophy has entered into my thinking about the twin paradox in this way: when some physicists contend that simultaneity at a distance is meaningless, I have a philosophical problem with that. IF I were that traveler, I don’t think I would be able to believe that she no longer EXISTS whenever I am not co-located with her. (And I doubt that many other physicists believe that either). BUT many physicists DO believe that she doesn’t have a well-defined current AGE when he is separated from her (at least if he has accelerated recently). THAT’S the conclusion that I can’t accept philosophically: it seems to me that if she currently EXISTS right now, she must be DOING something right now, and if she is DOING something right now, she must be some specific AGE right now. So I conclude that her current age, according to him, can’t be a meaningless concept. That puts me at odds with many other physicists.

What say the philosophers on this forum?

Time travel isn’t possible. If you travelled to your exact past or future, you’d exist exactly as yourself with no memory of having traversed… for the further self, you’d remember time traveling, but it would seem like nothing happened.

What’s actually occurring in terms of physics, is that you’re splitting alternate realities.

Does that help?

I realized that what I said was vague.

What I meant to say is that the type of time travel you and your physicists are thinking of, is that when these limits are approached… and that like you travel back to see yourself as a child etc… THAT type of time travel is splitting alternate realities!!

Traveling to your EXACT past or EXACT future is impossible

Philosophy is the mother of physics… I glad you stopped by

There is absolutely no time travel in my posting.

In special relativity, observers who are moving with respect to each other disagree about the current age of each other. With some types of acceleration of an observer, and when we adopt the most common of the simultaneity “conventions”, which is the co-moving inertial frames (CMIF) method, the observer will conclude that the distant person rapidly gets younger. But there is no time travel involved in that. The distant observer doesn’t agree that she is getting older … she says she is ageing at her normal rate, at all times.

My purpose here is to find out what philosophers think of my “intuitive philosophizing” that I described. I’m not interested in teaching special relativity, or in defending it.

The actual paradox is that Einstein states that time is both a constant and not a constant. He’s contradicting himself. He argues that the person approaching light does not experience time slowed down… but that their sense of time is stable, like everyone else. That means time is a constant.

He also argues that both parties experience time moving at the same rate, that means time is not a constant, because when they return, people experience more or less time, it’s relative.

We usually reserve the pissing matches for regulars here lol!

To say that “simultaneity at a vast distance” is a meaningless concept" is to make s sense to me because of the absence of an operation to measure such purported simultaneity. How can we know with any degree of confidence that two events occurred at the same instant if we can’t [at least at present] encompass both events within one gestalt?
So for now it remains meaningless.

For a concept to have meaning one ought to be able to define it or describe it (with attributes.) Attributes are the names of properties.

To enter the domain of meta-philosophy, I shall herewith define “philosophy” as the analysis and clarification of vague concepts; and science is the analysis and clarification of precise concepts. I learned that from a heavyweight-philosopher, a polymath genius, Robert S. Hartman. He gets the credit. See his book, The Structure of Value, (Carbondale, Southern Illinois Univ. Press, 1967.)
Once concepts get sharpened up enough to be exact or precise they are becoming components of a science; they are leaving the realm of philosophy. …except for the fact that there can always be a Philosophy of Science for that new science.

{We note that as scientific research proceeds, it raises more questions than it answers. Yet it does solve problems; and, in its engineering applications, it does often enhance the quality of human life. Yet, keep in mind, that every development has its costs as well as its benefits. The invention of the knife was very helpful though it can be used for murder and other evils, as well as for making fresh, nourishinng salads .}

Einstein, the creator of Special Relativity, regarded himself as a Philosopher/Scientist. Usually all the founders of new sciences are both: philosophers and scientists.

You may want to argue that “philosophy is more than conceptual analysis” but that is not what I said. I claimed that good philosophy clarifies concepts. These concepts are, at first, either vague or ambiguous. Look at any discussion here, where terms are not defined, and you could get the impression that ‘words are just chasing words.’ In contrast, in a scientific framework the terms - at least the key terms - are well-defined.

Our thanks go out to Mike Fontenot for a good contribution!!