Re: LSU professor resolves Einstein's twin paradox
- From: karandash2000@xxxxxxxxx
- Date: 26 Apr 2007 11:01:31 -0700
On Apr 26, 7:17 am, Surfer <sur...@xxxxxxxxxxx> wrote:
On 25 Apr 2007 22:49:47 -0700, karandash2...@xxxxxxxxx wrote:
Imbecile: the twins paradox is ...not a paradox.
In:
What the Global Positioning System Tells Us about the Twin's Paradoxhttp://redshift.vif.com/JournalFiles/V10NO1PDF/V10N1TVF.pdf
Tom Van Flandern put it as follows:
The "twin's paradox" is an illustration of the complexity of SR's
interpretations of nature. Suppose two identical twins start out at
some common instant. One remains on Earth. The other (the "traveler")
is on a spacecraft headed for Alpha Centauri (AC) four light-years
away at 99% of the speed of light, for which speed the time dilation
factor is gamma = 7 . (We choose a large value of gamma so that the
effects of the relativity of motion will be large and obvious, not
subtle.) Upon arrival at AC, the traveler turns back to Earth at the
same speed (or is replaced by a traveler already headed toward Earth
of identical biological age at the moment they pass, to avoid need for
an acceleration). The round trip requires slightly over 8 years Earth
time; let's say 98 months to be specific. This is path 1 in
Figure 1. When the twins are reunited, the Earth-bound twin is 98
months old, and the traveler is 14 months old (a factor of 7 less).
That much is a clear prediction of SR. Note especially that no
accelerations need actually occur at the beginning or end of the
journey, nor even in the middle if we do the "twin replacement" trick.
At each stage of the journey where an event occurs, comparisons can be
made without ambiguity between adjacent points, one in each of the
inertial frames containing the clocks or twins to be compared. Despite
the fact that many textbooks discussing the twin's paradox treat
accelerations as essential, that is illusory. Accelerations are
unbounded in size, and in principle can be done in an instant,
allowing no local time to elapse in any relevant frame. Accelerations
do not change local clocks, clock rates, or biological aging.
Now we come to the paradox part: Why isn't the traveler entitled
to claim that the spacecraft remained at rest and the Earth traveled
away at 99% of the speed of light, then turned around and came back?
From that perspective, the original traveler would argue that the
Earth-bound twin should be the younger one. We will examine the
rather different answers to that question offered by SR and by LR.
<<<<
Then later he writes:
<<<<
What we have just described are careful and correct inferences of SR
as applied to the twin's paradox. This also shows the essentially
mathematical nature of the theory, because it does violence to what
we fondly call "common sense". The most important point to note
carefully is that the theory is internally consistent, and no
mathematical contradictions can be found no matter how the
transformation equations are manipulated, or how many frames or
twins are introduced. The next important point to note is that SR
makes demands on our credulity that LR does not. Let's examine
why.
At the point of turn-around on the original journey from Earth to
AC, the traveler's inferences about time on Earth changed suddenly.
Instead of the physically unrealistic instant turn-around, let's
assume the spacecraft "orbits" around AC to perform the turn-around.
(To stay at a safe distance from the star at the same speed, this
would require propulsion, but just gravity.) This can still take a
time short enough to be neglected, especially at such a high relative
speed. So the traveler's spacecraft changes from headed away from
Earth and inferring the Earth year is 2000, to traveling toward Earth
and inferring the Earth year is 2008. Again, SR says this is real,
physical time, and not an illusion.
So before commencing a journey back to Earth, let's suppose the
traveler orbits AC several times. Then each time the traveler heads
away from Earth in that orbit, Earth time drops back to 2000; and
each time the traveler heads toward Earth, inferred Earth time
becomes 2008. The Earth-year is intermediate for intermediate orbital
positions. Now the significance of repeating this situation several
times is that, as Earth time goes to 2008, many people will have died
and others will be born. And on each occasion that Earth time reverts
to 2000, some of the dead will be resurrected and some living young
children in 2008 will cease to exist in 2000. Note that while all this
is happening according to SR, the on-board GPS clock representing
LR's "universal time" continues to insist that Earth time is the same
as spacecraft time and AC time: 2004 everywhere. In SR, effects of
this type are never observable because they "lie outside the
observer's light cone", hidden from direct view by the finite speed of
light.
Nonetheless, SR insists that such changes affect real, physical time
and are not mere illusions, because the viewpoint of each inertial
frame is just as valid as that from any other frame.
In LR, one reference frame (the local gravity field) is preferred;
and speed cannot affect time, but only the rate of ticking of
mechanical, electromagnetic, or biological clocks. However, just as
we do not assume that time has been affected when the temperature
rises and causes a pendulum clock to slow down, LR says that
changes in clock rates are changes in the rates of physical processes,
and do not affect space or time. So by carrying an on-board GPS
clock on the spacecraft, we are offered a clear choice between
models: Earth time can be what SR infers it is, or it can be what the
GPS clock says it is. In the former case, SR works, but leads to
heavy-duty complexities and fantastic inferences about the nature of
time at remote locations. Moreover, the proof that nothing can travel
faster than light in forward time stands intact. In the latter case,
LR works with great simplicity and in full accord with our intuitions
about the universality of the instant "now".
- Hide quoted text -
- Show quoted text -
Surfer,
You progressed from sucking up to Cahill to sucking up to prof. kaka.
I am not going to even look at your quote by Tom van Flandern, he is a
very well known kook. Prof. kaka made a fool for himself. And you are
making a bigger fool of yourself by sucking up to any idiot who claims
a method for detecting absolute motion.
.
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