Value of c and strange things that don't happen when at c

[S.Vasojevic]

I think we can safely presume that for the purpose of the thought experiment we are both comoving observers and our peculiar velocity is 0. I do not see how you can now break the symetry of our views and easily distinguish who is moving and who is not? All will be relative.

Ok, I didn't put it to well. Try reading this: https://www.physicsforums.com/showthread.php?t=349396"

Also some usefull links are:
http://www.einstein-online.info/en/"
http://www.astro.ucla.edu/~wright/cosmolog.htm"

If we are comoving, and our peculiar velocity, is 0, but we are separating at 0.999 C, then you are sitting on the very edge of my observable universe, and vice versa, and we are moving due to the expansion.

 

[ZirkMan]

If we are comoving, and our peculiar velocity, is 0, but we are separating at 0.999 C, then you are sitting on the very edge of my observable universe, and vice versa, and we are moving due to the expansion.

Ok, I see your point now. You are right, I cannot be comoving and at the same time "accelerated" to 0.999c by something else but the expansion of space.

So, Ok, in my experiment we are not comoving observers. But even then the measurement of your and my relative velocity in relation to the comoving frame of reference doesn't give you any base to judge who is moving and who is not in absolute terms (only relative to the comoving frame). And it certainly doesn't give rise to the difference in age of the traveling twins. The existence of the comoving frame is totally irelevant to the effect because the geometry of the universe in the comoving frame is considered to be flat (so we do not presume any global diferences in the background spacetime curvature of the frames in comparison). The difference in age after the journey is solely based on the broken symetry resulting from the cumulation of differences of the frames both twins went through during the duration of the journey (as I have explained above). But this would apply only for the twins experiment.

For our experiment if we were twins and we would be born into our inertial frames of reference moving in relation to each other with 0.999c and then I would suddenly stop and meet you (so no slow acceleration/deacceleration would occur) we would be the same age after we met. Even though before I was moving with 0.999c in relation to you. I know this is not realistic but as an illustration should be enough.

 

[S.Vasojevic]

For our experiment if we were twins and we would be born into our inertial frames of reference moving in relation to each other with 0.999c and then I would suddenly stop and meet you (so no slow acceleration/deacceleration would occur) we would be the same age after we met. Even though before I was moving with 0.999c in relation to you. I know this is not realistic but as an illustration should be enough.

If we are twins we must be born in the same frame, by definition. If something suddenly stops, it is infinite deacceleration. Speck of dust falling on the floor of your room would exert infinite force if instantly stopped, thus can not be instantly stopped.

It is not like when SR, GR and new age stuff came along that we dropped classic physics.
It is absolutely essential to have good knowledge of classical mechanics and electromagnetism in order to trully comprehend paths of modern physics.
I suggest that you start with Newtonian mechanics.

EDIT: When you are coming up with thought experiment, in order to make any sense, you should obey every known law of physics. If you ask what would happen if something instantly stops, the only result you will get is answer why it can not be so. You can not put it in any broader contest.

 

[ZirkMan]

All right. I think we came as long as we could. I wanted to demonstrate the basic principles not to model an exact experiment in the real universe (not yet). Thank you for your time.

 

[ZirkMan]

I suggest that you start with Newtonian mechanics.

My personal opinion on that this is really wrong. We should start teaching physics even small children from the beginning from the relativity's point of view (of course not matematically but as a principle) and introduce classical mechanics as a special limited case later as a historic note.

This is because the relativistic model of the world is so much real model of reality than any other model and when you study for years physics in the classical framework of absolute time and space and only a after many years you are introduced to the relativity as if it was some special case of the previous model (most people won't even reach this stage and physics will remain for them classical forever), no wonder people have problem to understand even basic principles of relativity and struggle with a twin paradox or other thought experiments for such a long time (and even then their explanation must not be based on correct principles)

So this is my personal view, and I am going to watch the Mechanical Universe series now so that nobody can point to me that I should study that first (which I have but not full time). :)