Re: Twin paradox revisited ll

"bill" <cosmosco@xxxxxxxxxxxxxxx> wrote in message
news:1185067888.303275.182390@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Yes .. its possible that when the travelling twin returns, the at-home
twin
could be dead .. and so could his descendants for many generations .. All
dead. But the traveller didn't kill them.

That's *not* what I'm talking about. I'm referring to the idea that
the traveler truly believes that the earth is *physically* orbiting
the sun at 1m-s as he travels away from us at close to the speed of
light or, during his return trip, that the earth is *physically*
traveling around the sun at close to the speed of light.

From his iFor it IS physically doing that

I do not accept that idea on the basis that neither twin can do
anything to the other and the traveler cannot change the orbital
velocity of the earth as that original posting insisted.

But it is different for the two twins. Really. A twin at rest wrt the sun
would see the earth orbitting at a faster rate than a twin moving wrt the
sun.

I didn't ask that question. I asked how either of the twins can
determine that the other one is physically aging at a different rate
than himself other than by observation. Perhaps you should have added
'from the point of view of the traveling twin'?
When the traveler returns they can compare. Count birthdays .. look at a
calendar .. better, have an accurate clock with each twin.
I had hoped that readers would have realised that I was referring to
observations or determinations made *during the trips*.

Both twins age at the same rate .. but less time elapses for the travelling
twin. It is the acceleration (which is for the traveller and not the
at-home twin) that causes this.

And in that coordinate system the traveling twin can destroy all life
on the planet
The travelling twin does nothing .. other than travel and return.
The stay at home twin does even less.
That's what I'm *saying*.

But it is the phyics of the acceleration that changes time for the
traveller.

so perhaps we had better keep that idea a secret from
any traveler who may become space happy.
You're being silly.
It was a flippant response to an asinine comment.

Indeed

3. There is a coordinate system in which the traveling
twin ages faster than the stay-at-home twin at all points
In other words, special theory is wrong?
Why do you think that?

Because special theory insist that a moving clock ticks over at a
slower rate than a stationary clock

That is correct .. when travelling inertially (ie no acceleration)

*not* that a stationary clock
ticks over at a faster rate than a moving clock.

Its not that it is a moving clock .. but an ACCELERATING clock. That's the
difference.

The moving clock does not
tick over at a slower rate than the stationary clock
But it does .. from the iFoR of the stationary clock
You have deliberately taken that comment out of context.

No

and this can be
*confirmed* by drawing lines on a piece of paper?
*except* for the brief turn-around, but the stay-at-home
twin ages *much* faster during turn-around.
The traveler brings his ship to a stop. He either reverses his engines
or turns the ship over end for end which takes about a minute? In that
minute (at which time he is stationary relatively to the earth - i.e.
he is in the same reference frame as the planet) and his clock is
*physically* ticking over at the same rate as his twin's clock,
If he stops accelerating and moving yes. But it is not required for him
to
stop accelerating .
He was *not* accelerating prior to turn around but was *decelerating*

Its the same thing. Declerating is just a colloquial (non-physics) term for
an accleration in a particular direction relative to an given observer and
object.

prior to which he was *not* accelerating but was moving at a uniform
velocity.

Yes .. during that time uniform velocity period we have the symmerticall
case that both clocks ctick slow relative to the other.

a time
differential that may have arisen from a journey that lasted for
twenty years with the ship moving at close to the speed of light is
completely reversed?
And this *physically* takes place because somebody draws lines on a
*** of paper?
Does a road travel between one town and another because it is on a map ..
don't be silly
Perhaps you should *read* my comment?

I did .. you should read my reply

I'm suggesting that a time
differential that may have arisen from a journey that lasted for
twenty years with the ship moving at close to the speed of light is
completely reversed and that this *physically* takes place because
somebody draws lines on a *** of paper is a nonsensical idea
analogous to your traveling road.

Yes .. its nonsense .. did you not see me agree with that?

See response to coordinate system
These are alternative descriptions of what happens. What
they have in common is the end result: When the two twins
get back together, the traveling twin will be younger than
the stay-at-home twin.
Agreed.
So what's your problem?
My *problem* is that I do *not* accept the idea that the earth bound
twin ages at the faster rate on the basis that this is what the
traveler determines.

And as I've told you several times .. BOTH twins age at the SAME rate. But
less time elapses for the travelling twin. That is due to the acceleration
of the travelling twin.

You might ask how can the traveling twin's turning around
cause the stay-at-home twin to age faster?
I might and I *have*.
The answer is
that "rate of aging" is not a physically meaningful quantity.
No, when it's applied to the stay at home - its a nonsense.
The rate of aging is the same .. the difference is that less time has
elapsed for the travelling twin
Agreed

There you go then

my point being that it is nonsensical to suggest, as per the
original posting, that *more* time has elapsed for the stay at home
twin.

Its not nonsense .. if less time has elapsed for the traveller than the
stay-at-home twin, then move timw has elapsed for the stay-at-home twin than
for the traveller. How could it be otherwise?

SR (and the twins paradox) does not say anything about the rate of aging.
Both twins age at the same rate. What happens is that the elapsed time
in
which they age (at the usual rate) is shorter for the travelling twin.
So
he will be younger than his brother when he returns.
I *know* that!

Good .. but you still seem to be talking about rates of aging being
different.

The original posting insisted that the stay at home
physically ages at a faster rate than the traveler

I've said consitently here that both twins age at the same rate

and only during
acceleration following turn around and *this* is what my argument is
all about.
You have seemingly entered a discussion unaware of the original concept

No .. but you seem to have some odd (or misunderstood) ideas of your own
here.


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