On Jul 5, 1:04 pm, stevendaryl3...@yahoo.com (Daryl McCullough) wrote: > harald says... > > >On Jul 5, 4:18=A0am, stevendaryl3...@yahoo.com (Daryl McCullough) wrote: > >> harald says... > > >> >Einstein explained how a paradox arose with the inception of GRT: > > >> It's athttp://tiny.cc/kz0uq > > >> I read the dialog, and I do not agree with your description of it, > >>as a paradox of GR. The fact is, as I said, the "GR description" is > >>actually not GR at all, it's SR being expressed in noninertial coordinates. > > >That's wrong: SRT does not *have* such concepts as > >"induced gravitational fields". > > Yes, it certainly does. If you are in a rocket that is accelerating > upwards, and you drop a ball, it will fall to the floor. That's true > in Newtonian physica, and it's true in SR. That's all > that is meant by an induced gravitational field.
Acceleration effects are not identified as gravitational fields in Newtonian physics (which, as you now know, you didn't know); and neither is that the case in SRT. In those theories acceleration is "absolute", and no gravitational fields are caused by acceleration.
> >> The use of the term "gravitational field" is picturesque and suggestive, > >> but nothing that Einstein says about interpreting the twin paradox from > >> the point of view of the traveling twin is in any way > >> dependent on Einstein's theory of gravity. > > >Indeed it's not! > > Then it's not GR.
Please don't fool yourself: a theory's name is owned by the inventor, if he gave it that name (as is the case with GRT).
> It's SR in noninertial coordinates. So you > are mistaken in calling a paradox of GR, for two reasons: > (1) It's not a paradox, and (2) it's not GR. > > >That is well known - and it misses the point (again). > > I think it is because you have not made it very well. I still > have no idea what your point is.
Just study Einstein's paper carefully, and you'll know what theory the paradox challenges. On top of that (but that wasn't my point), you'll also find out:
- what the meaning is of his general PoR - what solution Einstein proposed
> I admit to mistaking your discussion about the General Principle > of Relativity as a discussion about GR, the theory of gravity.
> If your point is about the General Principle of Relativity (that > the laws are covariant under generalized changes of coordinates), > that has no physical content, and Einstein was mistaken to think > otherwise. You can always rewrite the laws so that they are > covariant.
I also think so, but on other grounds - in particular because of the mess that he gets himself in in his 1918 paper (is it a coincidence that it wasn't published in an English journal?). The way laws can be written hardly tells us what is physically going on.
In this thread, you pretend no less than that:
- Newton was mistaken with his Space postulate (while you evidently didn't even bother to read his arguments) - you know better than Einstein what his own theory is about (Cranky)
Which remind me of your correct analysis about cranks - but it does NOT only apply to cranks!
> However, I don't see how the twin paradox is a "consistency challenge" > for the principle of relativity or for GR, the gravitational theory. > > >1. I brought to your attention what history tells us about how the > >clock paradox started for Einstein, information that was kept hidden > >for the non-German speaking community for many decades > >2. The information conflicts with what you "know" (what you learned > >and believed for a long time) > >3. From that you conclude that point 1 must be wrong. > > I have no idea what you are talking about. I certainly have never > made claims about history. My point is about the logical relationships > among Special, General Relativity, and the twin paradox.
In order to establish such relationships, you'll have to be perfectly sure about:
- what special relativity is, and what not (don't mix it with "induced gravitational fields"!) - what general relativity is (I urge you to read Einstein's description) - what "the twin paradox" is about (it's explained in Einstein's 1918 paper).