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Relativists have never answered this question

Relativists have never answered this question - Physics Forum

Relativists have never answered this question - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


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  #1  
Old 11-05-2003, 09:08 AM
Robert Calvert
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Default Relativists have never answered this question



Imagine a spacecraft that leaves Mars and heads for Earth. When it gets here
and decelerates into our own frame of reference, we find that it's clock has
only measured half the time that a similar clock here on Earth has since the
spacecraft began it's trip. Now imagine that a second spacecraft leaves Mars
headed for Earth. Only this time, instead of the spacecraft decelerating
into our own frame of reference, we accelerate the earth up to it's frame of
reference. The question quite simply is How would both clocks compare now?
If you argue that the spacecraft's clock would still register half the
elapsed time, then you have just assigned to the Earth a privileged frame of
reference. After all, instead of the spacecraft decelerating into our frame
of reference, it would be just as valid to say that the Earth decelerated
into the spacecraft's frame of reference.

If you say that both clocks would read the same or that the Earth's clock
would run slower, then we could modify this experiment so that the Earth
only spends one second accelerating into the spacecraft's frame of
reference, comparing the two clocks and then decelerating both the Earth and
the spacecraft at the same rate until they both occupied the same frame of
reference that the Earth was in before. Since both clocks (in this second
scenario) remain in the same frame of reference after they have been
compared, the spacecraft's clock could not lose time compared to the Earth's
clock as both are decelerating.

So, what gives? Does any Relativist really understand the Theory of
Relativity?

Robert


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  #2  
Old 11-05-2003, 02:28 PM
Paul Cardinale
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Default Relativists have never answered this question

"Robert Calvert" <[Only registered users see links. ]> wrote in message news:<[Only registered users see links. ]>...

It depends on how they were synchronized at the beginning.

Paul Cardinale
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  #3  
Old 11-05-2003, 03:57 PM
Randy Poe
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Default Relativists have never answered this question

"Robert Calvert" <[Only registered users see links. ]> wrote in message news:<[Only registered users see links. ]>...

I'm confused about your premise. First you say that you
are actually accelerating the earth. Then you seem to
say that no, you are applying thrust to the spacecraft
but it should be equivalent to accelerating the earth.

Those two situations aren't equivalent. In the case
of a spacecraft being accelerated while the earth is
not, the earth IS a privileged frame. It's inertial
(approximately) while the spacecraft is not.

At any rate, the answer to your question is that
the results of the experiment will depend on the
acceleration of both spacecraft and earth, and that
the experiments are not equivalent.

- Randy
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  #4  
Old 11-05-2003, 06:05 PM
Robert Calvert
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Default Relativists have never answered this question


"Jem" <xxx@xxx.xxx> wrote in message newsQ5qb.1973$62.1308@lakeread04...
here
has
the
Mars
frame of
now?
frame of
frame
decelerated
clock
and
of
second
Earth's
But this brings us back to a dilemma that I posted in another thread.
Instead of the spacecraft accelerating toward the Earth, let's say that they
both accelerate toward each other at the same rate. In this way, we've
eliminated the possibility that the acceleration of the spacecraft has
caused it's clock to run slower than Earth's clock. To put it another way,
we've reduced this question to one of pure relative motion and not one of
relative motion combined with acceleration.

Robert



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  #5  
Old 11-06-2003, 03:14 AM
Igor
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Default Relativists have never answered this question

On Wed, 5 Nov 2003 04:08:21 -0500, "Robert Calvert"
<[Only registered users see links. ]> wrote:


You guys seem to keep making this way too complicated. All you need
to do is take the differences in the length of their worldines and
divide by c. That's how it actually works in the end.

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  #6  
Old 11-06-2003, 03:22 AM
Paul R. Mays
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Default Relativists have never answered this question


"Igor" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ]...

<<<Snipped>>


What the hell is a "Worldine"... some new element?


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  #7  
Old 11-06-2003, 07:40 AM
June R Harton
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Default Relativists have never answered this question


"Igor" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ]...
here
has
the
Mars
of
now?
of
frame
and
of
Earth's

Igor, there is no time, spacetime, time dimension, block time, chrononon
thus no worldline, thus you best work out a new term.

news:[Only registered users see links. ]

[Only registered users see links. ]

[Only registered users see links. ]


from: Spirit of Truth

(using June's e-mail to communicate to you)!


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  #8  
Old 11-07-2003, 08:43 AM
Robert Calvert
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Default Relativists have never answered this question


"Jem" <[Only registered users see links. ]> wrote in message news:Kvsqb.7166$62.5905@lakeread04...
they
way,
of
I was always under the impression that relative motion of any kind resulted
in time dilation. Instead of a spacecraft accelerating toward Earth, we
could just as easily replace this spacecraft with an alien solar system from
another galaxy that has always been moving toward us as far as we would be
concerned. In this case, who's to say who accelerated and who didn't and by
how much? When this alien solar system passed the orbit of Mars, a space
probe of our own could record the time that it passed, the speed that it was
traveling when it passed and the time that it's clock read at the moment
that it passed Mars. If we sent the Earth hurtling toward the alien solar
system at the same speed and at the same time that the probe recorded it's
data, why should we make the assumption that our two clocks would agree on
the elapsed time once we met.? How do we know that we haven't already
accelerated toward them at some time in the distant past? Speaking for
myself, I can't help but be bugged by any concept that reeks of a privileged
frame of reference.

Robert


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  #9  
Old 11-07-2003, 12:49 PM
Igor
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Default Relativists have never answered this question

On Thu, 06 Nov 2003 07:40:01 GMT, "June R Harton"
<[Only registered users see links. ]> wrote:


And what universe are you guys posting from?


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  #10  
Old 11-07-2003, 05:14 PM
EL
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Default Relativists have never answered this question

"Robert Calvert" <[Only registered users see links. ]> wrote in message news:<[Only registered users see links. ]>...


[EL]
No.

EL
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