Re: Twin paradox revisited ll

"bill" <cosmosco@xxxxxxxxxxxxxxx> wrote in message
news:1184975348.416557.318470@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Bill
When the traveller is in inertial motion he us fully justified in
suggesting that he is stationary and the Earth is moving.

Having experienced the force of acceleration as he blasts off from the
planet and is now in free fall he may be justified in idly musing
about the fact that it appears that the planet is moving away from him
but is this philosophical solipsist notion reality?

Yes .. if you are moving away from me, then I am moving away from you

Has the planet, and the rest of the universe, undergone acceleration
thereby creating this motion.?

Noone is claiming that. We aretalking about the situation AFTER the
acceleration. The acceleration is finished .. in that past. Lets say that
the traveller was nconsciour during launch and just woke up. he would
simply note that the planet is moving away from him (and other planets
moving closer) .. and that he is stationary.

Surely an intelligent astronaut would
conclude that whilst this appears to be taking place it is nothing
more than an illusion created by his travel through space?

What someone might calcaulte or conclude is not relevant to the physics ..
thats just psychology.

When
he in not in inertial motion (because he is accelerating to turn
around) he cannot consider the Earth to be accelerating.
Acceleration is not relative.

He is not accelerating to turn around.

Yes .. he is .. you cannot change velocity without acceleration.
acceleration IS change in velocity.

In accordance with your comment that acceleration is not relative
then, as he accelerates away from the planet, he is not allowed to
conclude that it is the earth that is accelerating away from him

Yeup .. but at any instant, the earth is moving away from him and him away
from the earth

however, having attained a maximum required instantaneous velocity he
takes his foot off the gas pedal and, at that very instant, he
concludes that he is no longer moving away from the earth but that it
is the earth that is moving away from him?

Again .. you're bringing psychology into it. What he thinks doesn't matter
... he IS moving away from the earth AND the earth IS moving away from him.
Both are true. How he cares to think about it makes no difference.

On the basis of the relativity insistence - along with Einstein's 1918
explanation - that it is the traveler's clock, having experienced the
force of acceleration, that is ticking over at a slower rate than the
inertial twin's clock how can the inertial twin be of the opinion that
the traveler's clock is ticking over at a faster rate than his own
clock?

It is the relative motion that makes it slower .. after accelerating, the
travellers clock is slower in the iFoR of the earth AND the earth's clock is
slower in the iFoR of the traveller.

What *experiment* has shown that from the inertial twin's point of
view the traveler's clock is alternately ticking over at slower and
faster rates than his own clock?

The travellers clock never ticks faster that the at-home twin

If the traveler is moving away from the earth at just below that
particular velocity (whereby the gamma factor = 30,000) then one
second of his time is equal to 30,000 earth seconds. In addition, each
of the traveler's years must be equal to 30,000 years earth time and
for this to take place he must see the earth orbiting the sun at a
speed of 1m-s i.e 30,000m-s/30,000.

If he was moving (unaccelerated) at he'd see the earth taking 30000 years to
orbit

He would see the earth orbiting the sun more slowly than once per year
and on the basis that what he sees (i.e. that it is the earth that is
moving away from him rather than that he is moving away from the
earth) is, in his opinion, reality then he must determine that it
takes 30,000 earth orbits of the sun to equal one of his own years and
for this to take place it can only be moving at 1m-s from his point of
view.

You just contradicted yourself .. if eath is orbitting more slowly hewould
see one orbit of the earth take 30000 of his years

How can he measure 30,000 seconds of earth time for each of his own
seconds yet not measure 30,000 years of earth time for each of his own
years?

There is no problem here .. you just got it backwards

The subject on hand is not special relativity per se but the idea that
the inertial twin determines that the traveler physically ages at
faster or slower rates than himself depending on the traveler's
direction of travel.

The traveller ages less (because less time has elapsed) .. there is no
faster OR slower.


.

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