# Re: Another stab at the universal present moment - a gedanken..

```Jason,

Apparently we are not talking about the same scenario here somehow.```
```
Only acceleration/gravitation effects produce permanent clock time
differences that both observers agree to when they meet up again.

The same amount of acceleration, no matter where or when (or an equivalent
gravitational field), produces the same amount of permanent time dilation.

You claim that this is an SR effect and a geometric effect. As I said you
can analyze it that way, but the fact is that the geometry is CAUSED by GR
gravitational and acceleration effects. As I'm sure you know gravitation
expresses itself via spacetime geometry. In any world line diagram, changes
in direction of the lines are CAUSED by accelerations. The geometry is an
effect of gravitation/acceleration. That is GR at work...

Or maybe you are confusing the picture by confusing GR and SR effects. It
is true that accelerations also cause relative motions which add SR effects
to the GR effects, but all relative motion effects are NON-permanent and
cease as soon as the relative motion ceases and the twins meet up again.

So you CANNOT properly analyze this with respect to Present moment P-time,
as I pointed out in great detail in yesterday's post, WHILE there is still
that contradiction and why it does not falsify the notion of a common
present moment in my post yesterday.

There is always a common Present moment P-time, but (only) during relative
motion it is impossible to assign a consistent mapping that ALL observers
agree upon of clock time to P-time. But that doesn't mean P-time doesn't
exist. It just says that SR clock time effects can't be mapped consistently
to it because they are different for different relative motion observers in
the SAME present moment. But that is a temporary illusion of measurement.

Relative motion equal and opposite clock time dilation is an ILLUSION of
measurement that disappears as soon as the relative motion stops. On the
other hand acceleration/gravitation clock time dilation is an absolute
permanent clock time effect that all observers agree upon WHEN there is no
relative motion.

That should clarify everything but I fear it won't....

Edgar

On Friday, January 3, 2014 11:23:42 AM UTC-5, Jason wrote:
>
>
>
>
> On Fri, Jan 3, 2014 at 11:13 AM, Edgar L. Owen <edga...@att.net<javascript:>
> > wrote:
>
>> Jason,
>>
>> Come on Jason. Of course not. You have to have EQUAL amounts of
>> acceleration to produce the same effect. But doesn't matter where in space
>> it  is.
>>
>
> There are equal amounts of acceleration in both cases: 4 minutes worth.
>
> What there is not equal amounts of is relativistic time dilation, which is
> what explains the bulk of the age difference in the Sam-Pam case. The time
> dilation and slowed ageing of Pam is due to her high speed. She does not
> regain those lost years when she comes to a stop. So your statement that
> all the effects of SR vanish once they are back in the same frame is false.
>
> True, they are no longer time dilated or length contracted relative to
> each other, but they are still different in age because of it.
>
> Jason
>
>
>>
>> Edgar
>>
>>
>>
>> On Friday, January 3, 2014 10:24:26 AM UTC-5, Jason wrote:
>>
>>>
>>>
>>>
>>> On Fri, Jan 3, 2014 at 10:19 AM, Edgar L. Owen <edga...@att.net> wrote:
>>>
>>>> Jason,
>>>>
>>>> If the acceleration is the same, the slowing of clock time will be the
>>>> same... Doesn't matter where it is. Or equivalently (by the principle of
>>>> equivalence) it could be standing 'still' in a strong gravitational field.
>>>>
>>>> Edgar
>>>>
>>>>
>>>
>>> Okay but this is certainly not what happens.  If you spent 4 minutes
>>> accelerating and came back, there would not be a 4 year age difference when
>>> Pam returned.
>>>
>>> Jason
>>>
>>>
>>>
>>>>
>>>>
>>>>
>>>> On Friday, January 3, 2014 10:06:08 AM UTC-5, Jason wrote:
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> On Fri, Jan 3, 2014 at 9:21 AM, Edgar L. Owen <edga...@att.net> wrote:
>>>>>
>>>>>> Lliz, Brent and Jason,
>>>>>>
>>>>>> Actually Liz is correct here, by GR it is the acceleration. That is
>>>>>> the physical cause of the clock time differences of the twins.
>>>>>>
>>>>>
>>>>> In my experiment, lets say the acceleration lats for a total of 4
>>>>> minutes: one minute to accelerate up to 0.8 c, one minute to slow down at
>>>>> Proxima Centauri, one minute to accelerate back up to 0.8 c toward Earth,
>>>>> and a final minute to accelerate down to back at Earth.
>>>>>
>>>>> If the accelerations alone account for the clock discrepancies, then
>>>>> there would be no need to go to Proxima Centauri at all.  Pam could spend
>>>>> 4
>>>>> minutes whizzing around the solar system and get in all the same
>>>>> accelerations.
>>>>>
>>>>> Is this what you are saying?
>>>>>
>>>>> Jason
>>>>>
>>>>>
>>>>>>  It is true the effects can also be analyzed just by spacetime paths
>>>>>> as others have suggested, but it is actually the acceleration (or
>>>>>> equivalent gravitational field which is in effect an acceleration) which
>>>>>> actually physically produces the clock time differences when the twins
>>>>>> meet
>>>>>> up again.
>>>>>>
>>>>>> Edgar
>>>>>>
>>>>>>
>>>>>> On Friday, January 3, 2014 1:27:55 AM UTC-5, Liz R wrote:
>>>>>>>
>>>>>>> On 3 January 2014 17:30, meekerdb <meek...@verizon.net> wrote:
>>>>>>>
>>>>>>>>  On 1/2/2014 8:00 PM, LizR wrote:
>>>>>>>>
>>>>>>>>  On 3 January 2014 15:52, Jason Resch <jason...@gmail.com> wrote:
>>>>>>>>
>>>>>>>>   On Thu, Jan 2, 2014 at 9:31 PM, LizR <liz...@gmail.com> wrote:
>>>>>>>>>
>>>>>>>>>> Jason,
>>>>>>>>>>
>>>>>>>>>>  You may be missing the fact that the acceleration of the space
>>>>>>>>>> traveller is what causes the twin paradox.
>>>>>>>>>>
>>>>>>>>>
>>>>>>>>>  I would say it is not so much the acceleration that explains the
>>>>>>>>> paradox, but the fact that no matter how you rotate the paths, you
>>>>>>>>> always
>>>>>>>>> see a kink in the path Pam takes.
>>>>>>>>>
>>>>>>>>
>>>>>>>>  May I venture to suggest this is the same thing :-)
>>>>>>>>
>>>>>>>>
>>>>>>>> That's not exactly wrong - but it tends to make it confusing.  It's
>>>>>>>> like saying a road from A to B is longer than as-the-crow-flies
>>>>>>>> because of
>>>>>>>> its curves.  Yeah, that's true; but if you want to calculate how much
>>>>>>>> longer you see that the rate of excess distance is proportional to the
>>>>>>>> first integral of the curvature and so the total excess is the second
>>>>>>>> integral of the curvature - which is just the distance.  So it boils
>>>>>>>> down
>>>>>>>> to unstraight lines are longer than straight lines.  All the specific
>>>>>>>> details of acceleration get integrated out so it's easy to see that a
>>>>>>>> broken line (infinite accelerations) is just longer.  Or in spacetime,
>>>>>>>> unstraight worldlines are shorter than straight ones.  To phrase it in
>>>>>>>> stressful
>>>>>>>> effects of acceleration and how that could affect a clock,...
>>>>>>>>
>>>>>>>> I bow to your superior knowledge. I wasn't thinking about the aging
>>>>>>> effects of acceleration (as in the Heinlein story where they have to
>>>>>>> fly to
>>>>>>> Pluto at 3G) but just the fact that the course changes are the only way
>>>>>>> the
>>>>>>> twin paradox can be enacted - that is to say, it's what breaks the
>>>>>>> symmetry
>>>>>>> that otherwise exists between one ref frame's measurements and
>>>>>>> another's.
>>>>>>>
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