On Jan 4, 2014, at 5:36 PM, "Edgar L. Owen" <edgaro...@att.net> wrote:


PS: And don't tell me the twins meeting with different clock times in the same present moment is "an event" as if that explained something.

I use that word in the usual relatavistic (and traditional) sense. As something with defined spatial and temporal coordinates. A known time and place, where and when.


Of course it's an event. Everything that happens in the entire universe is an event. But what is the nature of that event from your perspective?


On Saturday, January 4, 2014 3:06:21 PM UTC-5, Jason wrote:

On Jan 4, 2014, at 12:32 PM, "Edgar L. Owen" <edga...@att.net> wrote:


If you don't agree with my theory of the Present moment, then what is your theory of this present moment we all experience our existence and all our actions within?

I believe no event embedded in space time is more real than any other event. You might interpret this as "all events exist". Our own perspective of existing in one particular event speaks nothing to the existence or non-existence of other events, be they in other places or in other times.

Under this view, the present momenent pops out as an indexical property of an observation. That is, one of Caesar's observations believes the present to be some moment in time around 0 AD, while one of mine believes it to be 2014. Another, equally real observation of mine, replying to a previous e-mail of yours might consider it to be 2013.

It clearly is not a clock time simultaneity since Pam and Sam shake hands and compare watches in the same present moment and their clock times are not simultaneous.

This can all be explained by normal special relativity. Relativity is not only fully consistent with the view I describe above, but relativity seems to be incompatible with the alternatives philosophies of time: presentism and possibilism.

This question is the key to the whole issue. Be interested to hear your answer...

I think the view of time I describe above is key to understanding what time is under relativity. Your rejection of this view may also be why you have so much difficulty reconciling your world view with relativity. I don't think presentism is a definsible position if special relativity is true.



On Friday, January 3, 2014 11:51:53 AM UTC-5, Jason wrote:

On Fri, Jan 3, 2014 at 11:10 AM, Edgar L. Owen <edga...@att.net> wrote:

Thanks for your several posts and charts. You really made me think and I like that!

Thanks, I am glad to hear it. :-)

I'm combining my responses to your multiple recent posts here.

First though there are two ways to analyze it, GR acceleration, as opposed to SR world lines, is the most useful because it makes the following argument re present time easier to understand.

In my example, acceleration effects can account for no more than 4 minutes worth of age difference, since they spend no more than 4 minutes accelerating. How do we explain the other 3 years, 355 days, 23 hours and 56 minutes that are missing from Pam's memory?

Imagine a new experiment in which Pam is completely still relative to Sam but somewhere way off in the universe and in a gravitational field of exactly the same strength. In this case both Pam's and Sam's clock times run at exactly the same rates and both agree to this. Therefore it is clear they inhabit the exact same present moment even by your arguments, and their identical clock times correlate to this.

Now assume Pam's gravitational field increases to the point where her clock time runs half as fast as Sam's. Again there is no relative motion so again both agree that Pam's clock time is running half as fast as Sam's. And again both exist in the exact same present moment, it's just that Sam's clock time is running twice as fast through that common present moment. Again clock time correlates with present moment time...

I think we should resolve the apparent problems P-time has with SR before trying to tackle GR...

This gravitational time slowing is a GR, not SR effect, and GR effects are absolute in the sense that they are permanent real effects that all observers agree upon. They must be distinguished from SR effects which make the situation more difficult to understand in terms of a present moment.

You may be right that P-time has no difficulties with GR, but it seems to have some with SR so let us focus on solving that.

An acceleration equivalent to the gravitational field would produce the exact same GR effect, but also introduces an SR relative velocity effect.

Now consider an pure SR effect in which Pam and Sam are traveling past each other at relativistic speeds but there is no acceleration. Velocity is relative, as opposed to acceleration which is absolute, therefore both observers think the other is moving relative to them, and both views are equally true. Now because of this relativity of velocity both observers see the clock of the other observer slow and by equal amounts. But the absolutely crucial thing to understand here is that this SR form of time dilation is not permanent and absolute like GR time dilation is. It vanishes as soon as the relative motion stops,

That is not true, the the effects of dilation in SR remain as well. Let's say James was born on a space ship at Proxima Cenauri travelling at 80% c toward Earth. It takes 5 years to get to Earth at this speed, but when we see baby James on board as he whizzes by he is only 3 years old. If the ship stops (or not), James is still 3 years old. GR never was a factor in James's reduced age.

whereas GR time differences are absolute and persist even after the acceleration stops.

This is why the SR versus GR model is more useful in understanding what is going on particularly with respect to the common present moment.

SR and GR are not two ways of looking at the same phenomenon, but two ways of explaining two different phenomena.

So during relative motion between Pam and Sam there most certainly is a common present moment, but trying to figure out what clock times of Pam and Sam correspond to that present moment leads to a contradiction (as you quite rightly pointed out with your diagrams) because Pam and Sam see clock time differently and do not agree on it. They did agree on their GR relativistic time differences and thus knowing which of their clock times corresponded to the same present moment was easy. With SR, equal and opposite, time dilation it is impossible to correlate both observers' clock times to the same present moment. Nevertheless that's just an artifact of SR clock time which doesn't falsify a common present moment. A common present moment exists, it just isn't correlated with clock times the same way by both observers.

Gabriel offered a clear example that I think falsifies the notion of a single consistent present moment, and his point has not yet been adequately addressed.

All the nice chart examples you took the time to produce demonstrate this. They are trying to assign an agreed upon clock time to the common present moment time during SR relative velocities and thus they correctly lead to the contradiction you pointed out.

However once you understand how this works

Do you currently understand how this works or are you also still trying to figure it out?

you understand that fact doesn't falsify a common present moment as you implied.

Why doesn't it? I am not seeing it or you haven't explained it clearly enough for me to get it.

Now consider the twins from the original example. In this case there is both lots of relative velocity SR effects between both twins, and there is the absolute GR acceleration effect on Pam only.

Now the SR effects persist only during relative motion and when the twins meet up again that leaves ONLY the GR acceleration effect which is the only cause of the twins' clock time difference.

If Pam were under acceleration for just a few minutes it could not explain an age difference of years. If you put Pam under the gravity of a black hole for 4 minutes, she would not age much during those 4 minutes, and so when you took the black hole away you would find her 4 minutes younger. In the experiment I described, the acceleration, which you compare to gravity, only lasts a few minutes. It is the time dilation of special relativity that accumulates over the years, and remains to explain the bulk of their age difference.

All SR relative velocity effects must vanish when the relative velocities cease. Otherwise we would have Pam and Sam meeting up again with each claiming the other's clock time was going slower than theirs. That is impossible.

It is possible when you consider the geometry of the situation, as Brent's nice charts further clarify. (What software did you use to make them Brent?)

At rest in the same present moment all observers must be able to agree on their clock time differences. Both agree Pam's clock time passed more slowly than Sam's and both agree as to the amount, based ONLY on GR (acceleration) effects.

Not true.

Assume again the twins passing each other at a constant (no acceleration) velocity. Both see the other's time passing slower than theirs and thus both see each other at an earlier clock time date than themselves. This is contradictory

It is not contradictory, it is because their paths are at an angle to each other through space time. If both of our paths are at 22.5 degrees toward each other, either of us can consistently say "the other is at a 45 degree angle toward me." This is not inconsistency, only relativity.

and cannot last when they meet. It is the acceleration that brings the relative velocities to zero that produces the only absolute persistent time effect and when, and only when, that happens will the twins agree as to their time differences, as always in a shared universal present moment.

In my "James example", there is no acceleration on James but he ages only 3 years in his 5 year journey.

This is why is is possible to correlated clock times to present moment time for GR acceleration time dilation, but NOT for SR relative velocity time dilation.

Hope this is clear. It may be a little difficult...

I don't think we've yet addressed the core issues between SR and P- time. Also, you have not said what use P-time has beyond SR. What can it explain that SR cannot? In other words, when would it make a prediction that differs from SR?


On Thursday, January 2, 2014 9:52:54 PM UTC-5, Jason wrote:

On Thu, Jan 2, 2014 at 9:31 PM, LizR <liz...@gmail.com> wrote:

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. So even if we start in Pam's reference frame where she is still, she has to stop (putting her back in the reference frame where Sam is 5 (not 1.8), then accelerate to 0.8 c back toward Earth, which she will see as length contracted to 2.4 ly again, and she will experience as taking 3 years, but in this frame, of heading back toward Earth at 0.8 c, Sam is not 5, but 7, so when she gets there after 3 years, Sam is (as she expects) 10 years old.

It isn't the acceleration which causes her age to suddenly change, but rather, her changing frames of reference (present moments), that causes her perspective of Sam to radically change, depending on her velocity.

As Edgar pointed out, time dilation is mutual, but only while velocities are constant.

Their relative velocity in relation to each other, and therefore their relative time dilations and length contractions, are always the same.

Your diagram demonstrated that the straight line parts of Pam's movement could be mapped either way onto Sam's (just tilt the diagram. But you can't may the entire trajectory onto Earth time by tilting the diagram.

I'm not sure what you mean by this..

Apologies if I'm teaching my gradnmother to suck eggs.

No worries. Let me know if my example or explanation still does not make sense. :-)


On 3 January 2014 15:25, Jason Resch <jason...@gmail.com> wrote:

On Thu, Jan 2, 2014 at 8:57 PM, Edgar L. Owen <edga...@att.net> wrote:

An excellent question. First of all let's stick with the actual example of only Sam and Pam. Now how do you know all this stuff about who is doing what when?

I calculate it from the parameters of the experiment as I described it. The different answers depend on different reference frames, which you can consider as straight lines dividing the past and future (but at different angles depending on one's velocity through space).

If you consider the gold and purple stars as two different events, the person moving to the right sees the present as all events on the blue line, and so they see the purple star happen before the yellow star, and vice versa for the observer moving to the left, whose present is represented by the red line. They see the yellow star come before the purple star.

How are you measuring it to know it's true?

4 light years away, at 80% the speed of light. It is no different than figuring out how long it takes to travel 4 miles at 0.8 miles per year. However, when travelling at these speeds, you have to contend with length contraction and time dilation (which are two aspects of the same phenomenon seen from two different perspectives).

See: http://faraday.physics.utoronto.ca/PVB/Harrison/SpecRel/Flash/LengthContract.html for a good explanation.

And again the important point to understand is that you MUST disregard SR relative velocity effects which are illusory and non- permanent and vanish when the relative velocities cease when they meet again.

You cannot disregard them. Otherwise you cannot explain why Pam is 6 when she meets with Sam at 10.

SR effects are not 'real' in the sense of being absolute. They are transient and relative and equal and opposite for both observers. Both see the other's time slow but that is just measurements, their time is not actually slowing in any absolute permanent sense. By that I mean they are illusions of measurement that exist only during relative motion. So they are not relevant when trying to analyze what is happening in the present moment.

They aren't illusions, from each one's own reference frame, the other is going more slowly through time.

GR acceleration affects on the other hand are real and absolute and experienced the same by both observers as the slowing of only the accelerating twin's clock relative to the non-accelerating twin's clock.

Relativity explains clock desynchronization. GR only comes into play when gravity is concerned. Pam would still be 6 and Sam 10, even if they accelerated instantly, or if Pam was already in motion when they were both born.

I think when temporary SR effects are eliminated this problem is resolved and your question is answered...

It's the SR effects that explain the age differences, and Pam doesn't age 4 years when she decelerates.


On Thursday, January 2, 2014 8:39:08 PM UTC-5, Jason wrote:

On Thu, Jan 2, 2014 at 8:07 PM, Edgar L. Owen <edga...@att.net> wrote:

That's very simple P-time allows us to explain how there is a present moment in which we experience our mutual existence, are able to converse together, shake hands, and compare our (different) clock times.

If there weren't such a common present moment distinct from our different clock times we could do none of those things because we would be in different moments of existence. We wouldn't even inhabit the same reality.

Obviously that's not a function of being in the same clock time, because it happens when we are in different clock times as well....

I think it does lead to a problem. Pam and Sam start at the same time, they are both zero and at Earth. They kiss each other good bye and Pam goes off into space. The present moment advances and both Pam and Sam experience something, they are now slightly older and both doing and experiencing something at this time.

A little time later, they are both slightly older, and they are both experiencing something. and so on, and this keeps happening, each of them experiences one moment after the other. Now, eventually, the event happens where Pam gets to her destination, Pam is now 3.

You agreed in an earlier e-mail tha
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