Symetry, time dilation, twin paradox and all that stuff

[resurgance2001]

"and there is just no way to tell what it is, you can also understand the question of their relative ages not to have an objective frame-independent answer at all"

But that's why I said, that to me, this has something of the 'flavour' of QM - the 'not knowing' in an objective sense - until one actually meets (which to me is like opening the box and making an observation)

It may not have any real physical similarity but I seem to find it easier to accept when I can see parallels/analogies. Some people have a lot of difficulty dealing with QM and it's apparently odd interpretations and all the uncertainty and etc. I have personally never found it hard to swallow QM ideas, but for some reason I do find these 'apparent paradoxes' in relativity excruciatingly difficult.

Thanks for your help though - I am beginning, I think, to make more sense of this thanks to you.

Cheers

Peter

 

[pervect]

If the twin paradox were like QM, assuming that a twin even had a definite age would lead to logical contradictions.

SR is really a lot simpler than QM. A twin has a "proper age" as measured in their own frame of reference (one can call this a writwatch age). This is a definite number, not one of those quantum things that is forbidden to have a definte value.

The only thing that's a bit odd about the behavior if this age is due to the fact that space and time are interconnected. Experimentally, one finds that when one twin moves around, his wristwatch age or proper age is not the same as that of the other twin when they meet again. And that's really all there is to it. If you move a clock around in a loop, it won't read the same as a clock that stays put. This is a fundamental feature of physics.

 

[JesseM]

"and there is just no way to tell what it is, you can also understand the question of their relative ages not to have an objective frame-independent answer at all"

But that's why I said, that to me, this has something of the 'flavour' of QM - the 'not knowing' in an objective sense - until one actually meets (which to me is like opening the box and making an observation)

But in QM, one can make a measurement of some variable like position and get an objective answer which would be true for everyone. In relativity, questions like the relative age of two separated twins have no objective answer, they are just frame-dependent. Would you also say that velocity in Newtonian physics is QM-like because there is no objective answer about an object's velocity, it depends on what frame you use? Would you say that the slope of a line on a 2D plane is QM-like, because the value of the slope depends on how you orient your coordinate axes? Would you say that the x-coordinate of an object in space is QM-like because it depends on where you choose to place the origin of your coordinate system? I really think the geometric analogy is best here, and few would argue that just because things like x-coordinate or slope have no single coordinate-independent value, that implies that we somehow can't have a totally objective picture of reality, whereas QM poses more of a real problem for those who want such an objective picture (although various 'interpretations' of QM do allow an objective description of the world independently of what we choose to measure).

Some people have a lot of difficulty dealing with QM and it's apparently odd interpretations and all the uncertainty and etc. I have personally never found it hard to swallow QM ideas

That may mean you don't understand it well enough! For example, would you agree that a measuring device should obey the same fundamental laws as the system it's measuring, since they're both just collections of the same type of fundamental particles? Would you say the fundamental laws of physics should be able to describe the entire universe, without the need for an external measuring device? QM poses difficulties for these notions, in a way that is unlike all non-quantum theories.