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