Brent, and anyone else who wants to answer, First, thanks for your patience and consideration in answering my questions. I appreciate it, and hope you will also take the time to address what I see is the crux of the journey to the center of the galaxy case below.
To review: the case of A traveling to the center of the galaxy at 1g acceleration and B staying home on earth (also in an exactly equal 1g acceleration of earth's gravity). On completion of the journey A's clock is found to have slowed greatly relative to B's. Now you say the actual slowing of A's clock relative to B is due only to geometry. But the question is who's geometry? Obviously your answer holds ONLY if we use B's geometry (a frame with B's location as origin) to be the correct frame. But from the POV of A, B's geometry is exactly equal and opposite. It is then B who travels 31,000 light years in space, and thus if it's only geometry A should see B's clock slow by the same amount that B sees A's clock slow. Is that not correct? If so then why is the slowing of A's clock relative to B's what both A and B agree upon at the end of the trip? If relativity is correct and all frames are equally valid and arbitrary then why, in this case, must we use only B's frame rather than A's to get the correct result? Does that not assume there is some absolute spacetime, similar to the aether, that all motion is relative to? If that is not correct then it can't just be geometry because we must choose one possible geometry over the other, one frame over the other as the 'correct' frame. It is no longer a matter of just geometry but choosing the single one CORRECT geometry since there are two (actually infinite) possible geometries. If we claim that we have to choose B's geometry, that it is somehow right and thus absolute in some sense (not just relative, and an arbitrary choice of coordinate system) then it seems we have to assume that there is some absolute spacetime similar to the aether, that all motion is relative to. On the other hand if we claim the effect is NOT due to geometry, but to acceleration, we are faced with the problem that A and B both experience the exact same 1g acceleration for the entire duration of the trip. So how could it be an acceleration effect if the acceleration of both A and B are identical? That would seem to violate the Principle of Equivalence would it not? Or, if like Liz, we claim it is due to A's reversal in direction of acceleration mid trip then we are faced with the problem that the direction of B's 1g acceleration is also continually changing during the trip as earth rotates. Thus we seem to have 3 choices each of which contains an unanswered question. Can you clarify please? Specifically why we must choose B's geometry over A's to get the correct result, when if we use A's geometry we get the opposite result, because B is moving relative to A during the entire journey the exact same amount that A is moving relative to B in B's geometry. So why is B's geometry privileged and A's isn't? I hope my question is clear. If not let me know and I'll try to clarify it... Thanks, Edgar On Saturday, February 1, 2014 8:51:28 PM UTC-5, Brent wrote: > > On 2/1/2014 9:46 AM, John Clark wrote: > > > > > On Sat, Feb 1, 2014 at 7:57 AM, Edgar L. Owen <edga...@att.net<javascript:> > > wrote: > > > One might think it was the acceleration that slowed time on A's clock, >> BUT the point is that A's acceleration was only 1g throughout the entire >> trip which was exactly EQUAL to B's gravitational acceleration back on >> earth. So if the accelerations were exactly equal during the entire trip >> how could A's acceleration slow time but B's not slow time by the same >> amount? >> > > If A were going into space and accelerating upward off the surface of > the Earth at one g (32 feet per second per second), then he would be > experiencing 2g, one g from the Earth and one g from his continuing change > in upward velocity. > > > But A would experience acceleration quickly decreasing to 1g as he left > the vicinity of the Earth. And the result wouldn't change if B entered a > centrifuge and experienced an exactly equal acceleration while remaining on > Earth. This is why I emphasize that it is NOT an effect of acceleration, > it is a geometric effect of different path lengths. > > Brent > > > > both = 1g throughout the entire trip >> > > No, not during the entire trip. And if the space traveler ever wants to > return to Earth to rejoin his friend so they can directly compare their > clocks then he's going to have to change the direction of his acceleration > by 180 degrees. So their clocks will not match because their travel > experiences were not symmetrical. > > John K Clark > > > > -- > You received this message because you are subscribed to the Google Groups > "Everything List" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to everything-li...@googlegroups.com <javascript:>. > To post to this group, send email to everyth...@googlegroups.com<javascript:> > . > Visit this group at http://groups.google.com/group/everything-list. > For more options, visit https://groups.google.com/groups/opt_out. > > > -- You received this message because you are subscribed to the Google Groups "Everything List" group. 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