I just posted a long and slightly OT response to this consisting of the
math for the "symetric twin" paradox. Since this discussion is really
just the earlier twin paradox restated, the same analysis applies to both.

However, there's one specific point which should be addressed, and which
Steve Bint should try to grok. Until you get this you'll never see why
the math works out, let alone understand what "really" happens.

Stephen Bint wrote:


It baffles me, that intelligent people, capable of algebra, cannot
see that the assertion that time is slowed in a moving frame is a
symmetrical assertion, because frames move relative to each other,
symmetrically.


When two frames are moving relative to each other, their clocks can NOT
be in sync. What this means, in confusing English, is that when I move
through SPACE in a frame which is moving relative to me, I am also
moving through TIME in that frame! The X axes are not aligned --
they're skewed.

So, the time rates are slowed symetrically ... but the rate of time
change with X position is mirror-imaged between the frames.

If this makes no sense to you (and I expect it does) then you should
really try to work through the math to see why it's asserted as part of
SR. The math, though messy, is _just_ linear algebra -- nothing more.

--
To email me directly, take out nospam and put back foobox.

"Dirk Van de moortel" wrote
in message ...

"Martin Hogbin" wrote in message
...

"Stephen Bint" wrote in message
.. .
.
you are appealing to me to be open-minded enough to be able to believe
it is
possible that I am wrong. I would ask the same of you.

There is a difference. Dan's view is supported by thousands
of physicists throughout the world who have studied the subject
in great detail for nearly a century.

You should start by understanding how two inertial observers
in relative motion would measure one another's clocks. It
would then be useful to understand how they would _see_
one another's clocks, which is different.

You have a choice. You can either join the list of crackpots
who frequent this group, and be treated with scorn and derision
by the physicists here, or you can make an effort to understand
the subject.

He has been here before with another name.
Same troll, new name.

Dirk Vdm

What was his old name, do you think?

Harald

See below.

"Stephen Bint" wrote in message
.. .
I started a thread about the twin paradox and cross-posted it to three
newsgroups. I am grateful to those who discussed it, even though it got a
tiny bit personal at times

I was frustrated by the account of the twin paradox in the FAQ for
sci.physics (http://www.faqs.org/faqs/physics-faq/part4/), because it
resorts to saying that there is assymetry in the situation. One twin has
undergone an acceleration and it is that one which is younger.

I agree, the faqs can be improved for sure.
Acceleration certainly isn't the official explanation; it's merely an
indicator of asymmetry.
(But you could have noticed, if you read it carefully: "and" instead of
"therefore"...)

SNIP

It baffles me, that intelligent people, capable of algebra, cannot see
that
the assertion that time is slowed in a moving frame is a symmetrical
assertion, because frames move relative to eachother, symmetrically.

But everyone sees that!

Besides which, the formula for time dilation is a function of the velocity
of the observed frame and makes no mention whatsoever of the acceleration
of
either frame, before or while the calculation is made.

True.

I was told again and again by several posters, "Do the math. Just plug the
numbers into the formulas and it all works out just fine." These were the
same people who want me to factor in acceleration, which is not mentioned
in
the formula, because time dilation is purely a function of the relative
velocity, which is the same in both directions.

Acceleration of the ref. frame of observation is not part of SRT, and
therefore not included in the equations either.
However, it is acknowledged that acceleration has no relativistic effect on
the accelerated clock... and then it gets tricky! ;-)
I may post another time more about that point, which is one that made me
choose LET instead of SRT as standard theory.
In case you are really new, LET is the abbreviation used in this group for
Lorentz' interpretation of his transformations and SRT, which differed from
that of Einstein. Nowadays only Einstein's interpretation is taught at
school. No need to tell more, you can find many hours of reading in the
archives... but the same is true for the Twin paradox!

Plug the relative velocity of skateboarders A and B into the formula and
find out how much slower B's clock is, than A's. And how much slower A's
is,
than B's. I don't need to "do the math" to see that this formula is
telling
me two things which cannot both be true.

I suppose it depends on your definition of "working out fine".

Because I constructed my example with two moving twins, to force them to
face the symmetry, the defenders of relativity introduced a new twist:
acceleration causes time to speed up, cancelling out the age difference,
in
both skateboarders. This is an new addition to relativity. Einstein never
said anything of the sort.

Wrong, he did, in 1918; it was -as he put it himself- his clever way out of
the Twin problem (in German, sorry).

To say that acceleration makes time run faster, implies that if one of the
skateboarders is accelerating, the time contraction due to acceleration
will
at least partially counteract the dilation caused by the velocity
(predicted
by Einstein), allowing the other to see the bouncing beam move faster than
c.

Really? Make sure that you know which acceleration has what effect on which
clock and according to who!

Still, though frustrated, I thoroughly enjoyed the thread I started and I
am
grateful to all of the people who had the patience to contribute. In
return,
I can only assure you that I will continue to post under the name "Stephen
Bint", so as not to undermine your killfile strategies.

And may I say in conclusion, that trying to bring the sweet light of
reason
to the proponents of relativity, is like trying to bring salvation to the
DAMNED.

Don't overestimate yourself!

Harald

"Stephen Bint" wrote in message ...

[crap snipped]

I see that you are both a jackass and an idiot.
You believe that because you are too stupid/lazy/arogant to learn the
math, that all you need to do is wave your arms and try to apply your
own ignorant comic-book misconception of relativity. You are a
clueless ineducable blubbering baffoon.

Paul Cardinale

"sal" wrote in message ...

The problem as stated was "two twins fly to Earth, each from a distance
of 1 ly, at a velocity of 0.75c. What happens?"

Earth uses coordinates (x,t)
Right twin uses coordinates (x',t')
Left twin uses coordinates (x",t")
World line Earth: x = 0 (t-axis)
World line Right twin: x' = 0 (t'-axis)
World line Left twin x" = 0 (t"-axis)

Right twin is present at event R: (x,t) = (D,0)
where/when his clock is set to t' = 0,
and he approaches Earth with relative speed v
Left twin is present at event L: (x,t) = (-D,0)
where/when his clock is set to t" = 0,
and he approaches Earth with relative speed v

[M]
/|\
/ | \
t"/ t \t'
/ | \
/ | \
/ | \
/ | \
-----[L]------|------[R]------x

Transformation Earth coord -- Right twin coord:
{ x' = g( (x-D) + vt )
{ t' = g( t + v(x-D)/c^2 )
Transformation Earth coord -- Left twin coord:
{ x" = g( (x+D) - vt )
{ t" = g( t - v(x+D)/c^2 )
where in both cases
g = 1/sqrt(1-v^2/c^2)

Meeting of the 3 world lines at event M:
{ x = 0
{ x' = 0
{ x" = 0
== 2 lines of algebra ==
(x,t) = ( 0, D/v )
(x',t') = ( 0, D/(gv) )
(x",t") = ( 0, D/(gv) )
According to Earth D/v seconds have passed.
According to both twins D/(vg) seconds have passed.

Dirk Vdm

"Harry" wrote in message ...
See below.

"Stephen Bint" wrote in message
.. .

[snip]

I was told again and again by several posters, "Do the math. Just plug the
numbers into the formulas and it all works out just fine." These were the
same people who want me to factor in acceleration, which is not mentioned
in
the formula, because time dilation is purely a function of the relative
velocity, which is the same in both directions.

Acceleration of the ref. frame of observation is not part of SRT,

Ha, but it *is* part of SRT:
net-ops.be

and
therefore not included in the equations either.

I think it is not included in the standard twin paradox
treatment because it is irrelevant.
When the accelerations are taken large enough, such
that the cruising velocities are reached in a short time,
then what happens during these accelerating phases
can be ignored when compared with what happens
during the cruising phases.

Dirk Vdm

"Harry" wrote in message ...

"Dirk Van de moortel" wrote

[snip]

He has been here before with another name.
Same troll, new name.

Dirk Vdm

What was his old name, do you think?

Not sure yet. His style suggests a few candidates.
But I could be wrong of course, this one could be
brand-new after-all :-)

Dirk Vdm

"Paul Cardinale" wrote in message om...
"Stephen Bint" wrote in message ...

[crap snipped]

I see that you are both a jackass and an idiot.
You believe that because you are too stupid/lazy/arogant to learn the
math, that all you need to do is wave your arms and try to apply your
own ignorant comic-book misconception of relativity. You are a
clueless ineducable blubbering baffoon.

You are too kind, sparing him like that ;-)

Dirk Vdm

Stephen Bint wrote:
[snip}

No need to do the math, eh? Crackpot. Special Relativity is a set of
hyperbolic rotations in 4-space. Do those matrix multiplications
intuitively, git.

http://hyperphysics.phy-astr.gsu.edu...iv/gratim.html
http://www.eftaylor.com/pub/projecta.pdf

--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!

Dirk,

When you warned me that G=EMC^2 Glazier is a
troll, I didn't like the way you elected yourself judge and jury over who is
a troll and who isn't. Nor did I like the way you saw fit to speak on behalf
of the others on this newsgroup.

Dirk:

"I think you don't want to know what the Bert believes.
You might want to know that in the beginning the Bert
used to be a Herb. We all wonder whether next year
the Bert will call himself a Terp or a Terk, and the year
after, whether the Terp will call himself a Perd or a Perl,
or perhaps whether the Terk will become a Kerl or a
Kerm. To survive on this forum one needs patience.
But you'll find that out soon enough."

I will be the judge of whether I want to know what Bert believes.

Now you are accusing me of being a troll, I like it even less. I have
started one thread on alt.sci.physics.new-theories about my cranky
strobing electron theory and contributed to a couple of other threads.
I have started two threads about the twin paradox, which I have
cross posted to three groups. I have confined myself almost entirely
to discussing the topics of these threads with those adults who have
chosen to discuss them with me.

Who the hell are you to declare me a troll, or any sort of pest? The threads
I have started concern subjects of great interest to me and I have every
right to discuss them here. I suppose you think the people contributing to
these discussions are all fools who have fallen into my trap. They come
across as a good deal more intelligent than you.

What I really take exception to is this:

He has been here before with another name.
Same troll, new name.

Dirk Vdm

This is a lie. You are lying about me, though I have done nothing to you,
nor have I been rude to anyone on this list, except Uncle Al, who was much
ruder to me first.

I think you owe me an apology.

Stephen Bint


"Dirk Van de moortel" wrote
in message ...

"Martin Hogbin" wrote in message
...

"Stephen Bint" wrote in message
.. .
.
you are appealing to me to be open-minded enough to be able to believe
it is
possible that I am wrong. I would ask the same of you.

There is a difference. Dan's view is supported by thousands
of physicists throughout the world who have studied the subject
in great detail for nearly a century.

You should start by understanding how two inertial observers
in relative motion would measure one another's clocks. It
would then be useful to understand how they would _see_
one another's clocks, which is different.

You have a choice. You can either join the list of crackpots
who frequent this group, and be treated with scorn and derision
by the physicists here, or you can make an effort to understand
the subject.

He has been here before with another name.
Same troll, new name.

Dirk Vdm