Re: Twin paradox revisited ll

On Jul 30, 12:02 pm, "papar...@xxxxxxxxx" <papar...@xxxxxxxxx> wrote:
On 29 jul, 20:07, bill <cosmo...@xxxxxxxxxxxxxxx> wrote:



On Jul 30, 4:03 am, Mike Fontenot <mlf...@xxxxxxxxxxx> wrote:

bill wrote:

There seems to be a discrepancy in your article at http://home.comcast.net/~mlfasf.

In paragraph 4 you have the traveler accelerating away from the earth
at 1g for a period of two years his time then coasting for 9 years.

In paragraph 5 he accelerates at -1g for two years [...]

You apparently misread the 5th paragraph...it actually says that
he accelerates at -1g for 3 years, not 2. When he starts that
acceleration, his speed is 0.968c (moving away from his twin).
When he finishes that acceleration, his speed is -0.774c (moving
toward his twin).

Mike Fontenot

Thank you, I did make that mistake - reading 2 years ilo the 3 years
you specified.

Bill

I think the main interpretation problem in this topic, is the fact
that every observer (both twins and possibly an external observer)
will have knowledge of what is going on the travel, only by his local
information (clocks) and by the outside information he is receiving at
Earth or at the ship (like radio messages or position of guiding
stars). This received information can only travel from its source at
c, since c is the maximum interaction propagation speed.

So the total trip look like this. Let us assume Twin A is staying
home, and Twin B is traveling to a star located 6 light years away, at
a speed v=0.6c. Every birthday, each twin sends a message to his
brother. The only information each has is his local time for the
sending of the message and his local time for the reception of his
twin message.

a) Twin B will travel, according to twin A, for 10 years before
reaching the star. In his local clock, this travel time will only
measure 8 years (due to time dilation).
b) Acceleration need not to be considered, since the acceleration
period is short with respect to the distance to be covered (at 2g, 4
months will make the ship to reach 0.6c).
c) At the 1st, 2nd, 3rd, 4th anniversary, twin A messages will have to
catch the traveling ship, the information will reach twin B at 2, 4, 6
and 8 years of his local clock. The last message will reach twin B
just as he is arriving to the destination star.
d) At his own 1st, 2nd, 3rd and 4th anniversaries, twin B will send
back to Earth his messages. These messages will reach twin A in his
own local time at 2, 4, 6 and 8 years. Twin B 5th to 8th messages will
be received by twin A at 10 to 16 years of his local clock.

So we see up to this point that the situation is quite symmetric, with
both twins seeing the other as "younger", according to received
messages.

e) Direction of travel changes and ship returns to Earth. Trip will
last 10 years, according to twin A, but only 8 years, according to
twin B.
f) Messages from twin A now arrive more frequently to the ship. So
messages from 5th up to 20th anniversaries will be received at twin B
location at 8.5, 9, 9.5 and so on to 16 years of his local clock.
g) Messages from twin B, on his way back to Earth, also arrive more
frequently to twin A. Thus twin B messages 9th, 10th up to 16th
anniversaries will be received at twin A location at 16.5, 17, and up
to 20 years of his local clock.

Again the situation is quite symmetric, but at the end twin B's clock
is showing 16 years has passed, while twin A's clock is showing 20
years has passed.

Miguel Rios

You are missing the point of my original posting which was that in the
correspondence 10 years ago and now in Mike's posting the traveler
determines that his twin appears to be aging at a slower rate than he
is thus he concludes that this is *physically, meaningfully, really*
taking place; that as Mike points out - when the traveler accelerates
during his return trip his sister's aging rate is *reversed*.

In accordance with that concept - the traveler truly believes that
during his period of acceleration the earth is *physically* spinning
backwards and is orbiting the sun in the opposite direction; that
millions of people have come back to life all because he has hit the
gas pedal.

This must give the traveler a *real* power of Godlike omnipotence -
the power of life over death and the ability to eliminate millions of
people by making them go back into the womb and to negate their
conception.

He can also 'cause' the galaxy to spin in the opposite direction;
reverse its direction of travel toward Virgo and bring about the
creation and destruction of millions of planets and stars.

One response to this discussion was that the traveler's actions - his
direction or rate of travel and his pressure upon, or release of, the
gas pedal - can have *no* physical effect on the earth or his sister
or on every galaxy in the entire universe and I tend to agree.

Any 'law' that insists otherwise is asinine.

The traveler is sitting in his ship on the launch pad. He hears the
command 'ignition'. He sees voluminous clouds of smoke and flames and
feels himself being pushed back into his seat. He continues to
accelerate and, as he does so, he sees, out his front window, that
section of the universe *appearing* to accelerate toward him and, via
his rear-view mirror, the rest of the universe, including the earth,
*appearing* to accelerate away from him.

He takes his foot off the gas pedal and at that very instant,
according to some posters, he is of the opinion that he is no longer
moving but that he is at rest and it is the universe that is moving
past him!

In the nanosecond prior to his taking his foot off the gas pedal he
sees what had appeared, prior to take off, a seemingly 'fixed'
firmament *appearing* to be flashing past him at close to the speed of
light and although he *knows*, having experienced a tremendous force
of acceleration during take off, that prior to removing his foot from
the gas pedal *he* was moving but a nanosecond later insists that he
is *not* moving?

In that previous nanosecond he was conducting an internal dynamic
experiment which proved, as he suspected, that his was *not* an
inertial reference frame - that his ship was in fact accelerating but
a fraction of a second later he concludes that, irrespective of that
period of acceleration, he has come to a stop?

If, as some people suggest, he is of the opinion that he does not
start moving following ignition but that it is the earth that is
dropping away from him he would be fully justified in screaming that
the sky is falling.

Why do some people continue to insist that the traveler cannot apply
logic and realise that millions of people are not coming out of the
grave? That he does *not* possess the power of life over death either
for people back on the planet or the stars themselves?

I am of the opinion that this is what they were taught and, in
accordance with that 'education' system, have lost, or never
possessed, the ability to be able to think for themselves.

In response to one of my postings a Professor of Physics at a major
Asian University wrote that whilst he could not agree with the
argument I had put forward at least it had made him *think*. What more
could one ask?

Bill


.

Relevant Pages

  • Re: Twin paradox revisited ll
    ... direction or rate of travel and his pressure upon, or release of, the ... moving but that he is at rest and it is the universe that is moving ... of acceleration during take off, that prior to removing his foot from ... If you consider twin B his view, of the space surrounding him, is ...
    (sci.physics.relativity)
  • Re: Twin paradox revisited ll
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    (sci.physics.relativity)
  • Re: SR paradox - help!
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  • Re: Proper Time v. Absolute Motion.
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