There can be no defence against the twin paradox
Stephen Bint
which clear readings are taken as two spaceships fly toward a meeting point
at 0.75c.
The experiment:
My twin and I, called A and B, are in spaceships, at rest with respect to
eachother and exactly one light-year apart. We know this by triangulation. I
synchronize my clock to the one on B's spaceship by setting mine exactly one
year ahead of his, as I see it through my telescope.
We intend to travel towards eachother very quickly and watch eachother's
clocks and speedometers and use triangulation to keep track of our apparent
speed, as we travel.
At an agreed time, we accelerate rapidly towards one another, until our
speedometers say 0.75c. We travel at 0.75c most of the way, then decellerate
until we are at rest with respect to eachother, at a meeting point.
Before I move,
1. His speed, using triangulation, appears to be 0.
2. His clock appears to be going at exactly the same rate as mine.
3. His speedometer says 0.
while I am accelerating,
1. His speed, using triangulation, rises to slightly less than 1c.
2. His clock appears to be getting slower and slower.
3. His speedometer rises to less than 0.75c.
while I am travelling at 0.75c, after allowing the image of his speedometer
saying 0.75c to reach me across space,
1. His speed, using triangulation, appears to be less than 1c.
2. His clock appears to be going slower than mine, at a constant rate.
3. His speedometer says 0.75c.
while I am deccelerating,
1. His speed, using triangulation, shrinks from near 1c, to 0.
2. His clock's rate improves from slower than mine, to the same as mine.
3. His speedometer's reports fall from 0.75c to 0.
When we get out and shake hands,
1. His speed, using triangulation, appears to be 0.
2. His clock appears to be going at exactly the same rate as mine.
3. His speedometer says 0.
Is that what would happen? If it is, we have an inescapable paradox. If I
witnessed those events, then my twin must be younger than me. His clock ran
at varying degrees of slowness, but never faster than mine, so his clock
must be behind mine.
But of course, because my twin behaved identically to me, he must have had
an identical experience and my clock must be behind his.
These contradictory and mutually exclusive predictions cannot both be true,
nor can only one, because the twins have behaved identically. Which leaves
"neither perdiction is true", as the only conceivable possibility.
If I have made a mistake in describing the experience of time dilation in
this example, please point it out.
Stephen
Sam Wormley
Stephen Bint
"Sam Wormley" <swor...@mchsi.com> wrote in message
news:3F9E96A6...@mchsi.com...
>
> http://scienceworld.wolfram.com/physics/SpecialRelativity.html
>
http://math.ucr.edu/home/baez/physics/Relativity/SR/TwinParadox/twin_intro.html
> http://www.edu-observatory.org/gps/gps_books.html#Relativity
Thank you for those. The first link is no use to me in this context, though
it does describe Einstein's theories very well.
The page at the second link attempts to solve the paradox using the
acceleration argument, which does not survive the problem as I have laid it
out in this thread. It only works when one twin remains stationary.
The third one is interesting. It never occurred to me that obsevations
relevant to relativity would be produced as a spin-off of GPS. I didn't read
them thoroughly, so I was left unsure as to whether the clocks are brought
forward in order to compensate for the sum of the effects of speed and low
gravity. Are they?
Will you hazard a guess at why my example leads to an inescapable paradox?
Stephen
Dirk Van de moortel
"Stephen Bint" <bi...@iname.com> wrote in message news:3f9e944a$0$116$65c6...@mercury.nildram.net...
> I would like to clarify the paradox by describing a simpler experiment, in
> which clear readings are taken as two spaceships fly toward a meeting point
> at 0.75c.
>
> The experiment:
>
> My twin and I, called A and B, are in spaceships, at rest with respect to
> eachother and exactly one light-year apart. We know this by triangulation.
Triangulation requires triangles. You have two points and
no way to make a triangle. You can know your distance
by sending radar signals and timing the round trips.
But that's not important...
[snip]
> Is that what would happen? If it is, we have an inescapable paradox. If I
> witnessed those events, then my twin must be younger than me. His clock ran
> at varying degrees of slowness, but never faster than mine, so his clock
> must be behind mine.
No.
Try to understand the entries in the FAQ *thoroughly* before
you try to understand what happens with accelerated frames.
When you are ready - take your time -, attack this one keeping
in mind that you have a symmetrical situation here.
>
> But of course, because my twin behaved identically to me, he must have had
> an identical experience and my clock must be behind his.
That is right.
>
> These contradictory and mutually exclusive predictions cannot both be true,
> nor can only one, because the twins have behaved identically. Which leaves
> "neither perdiction is true", as the only conceivable possibility.
The second is true. The first was wrong.
Try to find out why with the FAQ.
hth.
Dirk Vdm
Dirk Van de moortel
"Stephen Bint" <bi...@iname.com> wrote in message news:3f9e944a$0$116$65c6...@mercury.nildram.net...
> which clear readings are taken as two spaceships fly toward a meeting point
> at 0.75c.
>
> The experiment:
>
> My twin and I, called A and B, are in spaceships, at rest with respect to
> eachother and exactly one light-year apart. We know this by triangulation.
Triangulation requires triangles. You have two points and
no way to make a triangle. You can know your distance
by sending radar signals and timing the round trips.
But that's not important...
[snip]
> Is that what would happen? If it is, we have an inescapable paradox. If I
> witnessed those events, then my twin must be younger than me. His clock ran
> at varying degrees of slowness, but never faster than mine, so his clock
> must be behind mine.
No.
Try to understand the entries in the FAQ *thoroughly* before
you try to understand what happens with accelerated frames.
When you are ready - take your time -, attack this one keeping
in mind that you have a symmetrical situation here.
>
> But of course, because my twin behaved identically to me, he must have had
> an identical experience and my clock must be behind his.
Likewise, no.
>
> These contradictory and mutually exclusive predictions cannot both be true,
> nor can only one, because the twins have behaved identically. Which leaves
> "neither perdiction is true", as the only conceivable possibility.
You have the same ages because you had identical experiences,
and because you are together now.
Sam Wormley
The NAVSTAR GPS clocks are set to 10.22999999543 MHz vs 10.23000000000 MHz
http://rattler.cameron.edu/EMIS/journals/LRG/Articles/Volume6/2003-1ashby/index.html
Uncle Al
>
> I would like to clarify the paradox by describing a simpler experiment, in
> which clear readings are taken as two spaceships fly toward a meeting point
> at 0.75c.
> My twin and I, called A and B, are in spaceships, at rest with respect to
> eachother and exactly one light-year apart. We know this by triangulation.
You're already screwed. A relativistic universe has four distinct
distances: luminosity (inverse square), angular diameter, parallax,
and proper motion. No two of them need agree to maintain
consistency. Clocks can only be synchronized by being local.
There is no paradox. One twin travels relativistically, one twin
stays at home. When they reunite the traveling twin is seen to have
aged much less than its genetic double. The only "paradox" is the
asymmetry (not the effect). If they *both* travel, you work out the
relative hyperbolic rotation in 4-space vs. an outside observer to
both.
Acceleration breaks the symmetry of who ages faster. To accomplish
that, the acceleration can occur before the clocks (or the twins)
exist. Only reference frames matter.
Inertial frames with relative *velocities* pursue different paths
through spacetime in Special Relativity. No clock anomaly is apparent
in any of them until clocks are compared (by all being local when you
do it, initial calibration then experiment). Acceleration is
irrelevant in SR to the running of the clocks (as opposed to
Equivalence Principle acceleration in GR). Acceleration is necessary
at some arbitrary time not associated with the experiment itself for
breaking the symmetry of clock observation. Acceleration defines
which reference frame takes what path through spacetime - even if it
occurs when the clocks are *off* (or not even constructed yet, or
destroyed) - so the situation is NOT symmetric. There is a difference
between the reference frame and any clocks in it.
1) Acceleration is an absolute measurement and it does not require a
clock to make the measurement (e.g, simultaneous displacement of three
independent orthogonally cantilevered masses). There is no doubt who
was accelerated even if a clock was not running/existing during
aceleration. Any past accelerated reference frame has a different
mixture of space and time from an unaccelerated frame.
2) Past acceleration is irrelevant to the running of present clocks,
but not to the mixture of space and time in the reference frame that
said clocks measure. This is an important subtlety and the key to the
whole thing. You cannot synchronize clocks except by having them
local. That's what Relativity demands. If they are local at the
start, you can tell who was naughty thereafter without needing a clock
to do the acceleration measurement. Accelerometers are not clocks.
EXAMPLE: We have three identical clocks that are off (a state of not
running, or of not even having been fabricated) and zeroed. Each
clock has/will have a very short toggle jiggger switch sticking out.
We load them (or their parts, or ore and a smelter and a machine shop)
in individual spaceships and set up the experiment.
CLOCK 1: That's our clock. It sits stationary in our inertial
reference frame with a little jigger sticking out. Touch the jigger
and the "off" state becomes "on" or the "on" state becomes "off."
Clock 1 is "off." Or we can build it from parts just before we need
it, and in the "off" state, zeroed.
CLOCK 2: In a spaceship traveling at 0.999c relative to our inertial
frame of reference. Clock 2 is "off." It was built after all
acceleration ceased, and set to zero. It skims past Clock 1 (our
clock), the jiggers touch, both Clocks 1 and 2 are now "on" and
locally synchronized by touching. Elapsed time accumulates in each
one. The situation is NOT symmetric! We have an accelerometer and
they have an acelerometer. We know who accelerated to set up the
experiment even if there wasn't a clock present when it happened.
CLOCK 3: In a spaceship traveling at 0.999c relative to our inertial
frame of reference, but 180 degrees counter in direction to Clock 2.
Clock 3 is zeroed and "off." It was built after all acceleration
ceased, and set to zero.
Some arbitrary time after Clocks 1 and 2 synchronize and turn "on" by
touching, Clocks 2 and 3 brush past each other, touching jiggers.
Clock 2 is now "off," Clock 3 is now "on." Write down the elapsed
time in now "off" Clock 2, then smash the clock with a sledgehammer.
Or melt it down, or toss it over the side. The spaceship with Clock 3
is returning back over the path taken by the spaceship with Clock 2.
CLOCK 1: That's our clock. It sits stationary in our inertial
reference frame with a little jigger sticking out. Clock 3 rushes
past, jiggers touch. Clocks 3 and 1 are now off. All clocks are
off. No clock has accelerated while "on" or even while existing.
Write down elapsed times, smash each clock with a sledgehammer. Or
melt them down, or toss them.
BOTTOM LINE: Get all three slips of paper together... Accelerate as
you need. Or send all the results to all three folks by radio and
never decelerate. All clocks have been smashed, melted, tossed.
Their elapsed times were written down. The numbers on the papers
won't change when you accelerate or broadcast the data.
Acceleration is arguably General Relativity, as we did setting up the
experiment. It is irrelevant to the clocks. No clock is running or
even exists during acceleration. Numbers written on slips of paper
are unaffected by Special or General Relativity. One could as easily
build the clocks from their component parts after setting up the
experiment. No clock exists during acceleration up or down. The
*reference frame* has accelerated in the past, and that changes its
mix of space and time relative to an unaccelerated frame. The clocks
are passive observers in a presently unaccelerated setting.
Finally.... compare elapsed times. Elapsed time #2=#3 (straight line
motion for both traveling clocks, no acceleration!), but elapsed time
#2+#3 does not equal #1, the local stationary reference frame
summation. The sum of #2+#3 elasped time is only about 4.5% that than
of #1's accumulated elapsed time. You have the Twin Paradox (or,
Triplets) without any running clock having been accelerated - or
having even existed during acceleration up or down.
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
kenseto
> which clear readings are taken as two spaceships fly toward a meeting
point
> at 0.75c.
>
> The experiment:
>
> My twin and I, called A and B, are in spaceships, at rest with respect to
> eachother and exactly one light-year apart. We know this by triangulation.
I
> synchronize my clock to the one on B's spaceship by setting mine exactly
one
> year ahead of his, as I see it through my telescope.
There is no way to synchronize the two clocks as you said.
Ken Seto
Stephen Bint
"kenseto" <ken...@erinet.com> wrote in message
news:vptafl3...@corp.supernews.com...
the angles they adopt when trained on a point of the other ship, I can
triangulate the distance. Knowing the distance, I can account for the time
elapsed since the image of the clock I can see began its journey to my eye.
At what point do you think I would be doing the impossible?
Stephen Bint
"Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com> wrote
in message news:uDxnb.111979$Kh6.4...@phobos.telenet-ops.be...
>
> "Stephen Bint" <bi...@iname.com> wrote in message
news:3f9e944a$0$116$65c6...@mercury.nildram.net...
> > I would like to clarify the paradox by describing a simpler experiment,
in
> > which clear readings are taken as two spaceships fly toward a meeting
point
> > at 0.75c.
> >
> > The experiment:
> >
> > My twin and I, called A and B, are in spaceships, at rest with respect
to
> > eachother and exactly one light-year apart. We know this by
triangulation.
>
> Triangulation requires triangles. You have two points and
> no way to make a triangle. You can know your distance
> by sending radar signals and timing the round trips.
> But that's not important...
>
point on the other ship. By measuring the angles the telescopes are pointing
I can calculate the distance to the other ship. Are you saying that wouldn't
work?
> [snip]
>
> > Is that what would happen? If it is, we have an inescapable paradox. If
I
> > witnessed those events, then my twin must be younger than me. His clock
ran
> > at varying degrees of slowness, but never faster than mine, so his clock
> > must be behind mine.
>
> No.
> Try to understand the entries in the FAQ *thoroughly* before
> you try to understand what happens with accelerated frames.
> When you are ready - take your time -, attack this one keeping
> in mind that you have a symmetrical situation here.
>
The FAQ avoids the paradox, rather than solving it, by having the twins
doing different things. I have carefully avoided that bolthole in my
example.
If you think there is a flaw in the logic of my example, please point out
which of the three readings I described at the five points in my journey are
wrong.
> >
> > But of course, because my twin behaved identically to me, he must have
had
> > an identical experience and my clock must be behind his.
>
> That is right.
>
> >
> > These contradictory and mutually exclusive predictions cannot both be
true,
> > nor can only one, because the twins have behaved identically. Which
leaves
> > "neither perdiction is true", as the only conceivable possibility.
>
> The second is true. The first was wrong.
> Try to find out why with the FAQ.
> hth.
>
> Dirk Vdm
>
I don't understand what you mean. Please say which of these is false:
1. The twins behaved identically.
2. Because they behaved identically, it foillows that their experiences of
their journeys must have been identical.
3. My experience of seeing the other twin aging slowly, is in direct
contradiction of the other twin's experience, which is of me aging slowly.
4. Since they contradict eachother, they cannot both happen.
and remember, the FAQ's example has one twin remaining at earth, allowing
smoke and mirrors to allow people to sidestep the question.
Stephen
Dirk Van de moortel
"Stephen Bint" <bi...@iname.com> wrote in message news:3f9eb78a$0$122$65c6...@mercury.nildram.net...
>
Stephen, you replied to a post that I had cancelled
because I had misread one of your paragraphs.
Can you please look at my next response and reply
there?
Thanks and sorry :-)
Dirk Vdm
Richard
Simple, it's not a paradox, it's an outright contradiction. Now you can
get on with your life.
Richard Perry
Dirk Van de moortel
"Richard" <no_mail...@yahoo.com> wrote in message news:3F9EC1A1...@yahoo.com...
[snip]
> Simple, it's not a paradox, it's an outright contradiction. Now you can get
> on with your life.
What a child you are.
http://groups.google.com/groups?&as_umsgid=%Fkcb.38312$2w1.1...@phobos.telenet-ops.be
Dirk Vdm
G=EMC^2 Glazier
compared to its twin in a space ship going at "c" SR tells us at "c'
time stops. Bert
Richard
I can be childish at times, OTOH I call it relaxing and having a bit of
fun. OTOH, I'm right about SR. Demeanor has little to do with
plausibility, and you would still be wrong even if we were best buds.
Richard Perry
Stephen Bint
snip
>
>
> Simple, it's not a paradox, it's an outright contradiction.
Richard, are you defending time dilation or are you dismissing it as a
fallacy?
Are you saying the Secial Theory doesn't contradict itself, or that it
doesn't matter that it does.
> Now you can get on with your life.
>
> Richard Perry
I care, that people in charge of billion-dollar particle accelerators,
believe a theory which cannot possibly be true. So I'll keep my life on hold
for the moment.
Stephen
Uncle Al
>
> "Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com> wrote
> in message news:uDxnb.111979$Kh6.4...@phobos.telenet-ops.be...
> >
> > "Stephen Bint" <bi...@iname.com> wrote in message
> news:3f9e944a$0$116$65c6...@mercury.nildram.net...
> > > I would like to clarify the paradox by describing a simpler experiment,
> in
> > > which clear readings are taken as two spaceships fly toward a meeting
> point
> > > at 0.75c.
> > >
> > > The experiment:
> > >
> > > My twin and I, called A and B, are in spaceships, at rest with respect
> to
> > > eachother and exactly one light-year apart. We know this by
> triangulation.
> >
> > Triangulation requires triangles. You have two points and
> > no way to make a triangle. You can know your distance
> > by sending radar signals and timing the round trips.
> > But that's not important...
> >
> I have telescopes at opposite side of my ship. They are both trained on a
> point on the other ship. By measuring the angles the telescopes are pointing
> I can calculate the distance to the other ship. Are you saying that wouldn't
> work?
Won't work. That's distance by parallax. First, you can't measure
that small a subtended angle. Second, a relativistic universe has
four distinct distances: luminosity (inverse square), angular
diameter, parallax, and proper motion. No two of them need agree to
maintain consistency. Third, clocks can only be synchronized by being
local.
Fourth, all your communications will be delayed by a minimum of two
years. You have decribed an undoable experiment.
[snip]
Stephen Bint
"Uncle Al" <Uncl...@hate.spam.net> wrote in message
news:3F9ED293...@hate.spam.net...
> Stephen Bint wrote:
> >
> > I have telescopes at opposite side of my ship. They are both trained on
a
> > point on the other ship. By measuring the angles the telescopes are
pointing
> > I can calculate the distance to the other ship. Are you saying that
wouldn't
> > work?
>
> Won't work. That's distance by parallax. First, you can't measure
> that small a subtended angle.
At what distance does triangulation become impossible? Or is it impossible
at any distance?
Are you saying "can't measure that small a subtended angle" regardless of
how good your technology is? Is there something inherently unmeasurable
about small differences between angles?
You realise, that in an example in which I have two spaceships that can
travel at 0.75c, the standard of my engineering is very high.
> Second, a relativistic universe has
> four distinct distances: luminosity (inverse square), angular
> diameter, parallax, and proper motion. No two of them need agree to
> maintain consistency. Third, clocks can only be synchronized by being
> local.
>
How far apart is not local? As long as I can get a fixed point from which to
triangulate, I can calculate the distance and use the speed of light to
correct for the time lag and be certain, that the clocks are synchronized,
can't I?
Unless you can say why and at what distance triangulation fails to work.
Stephen
Stephen Bint
> Stephen Bint wrote:
> >
> > I would like to clarify the paradox by describing a simpler experiment,
in
> > which clear readings are taken as two spaceships fly toward a meeting
point
> > at 0.75c.
> [snip]
>
> > My twin and I, called A and B, are in spaceships, at rest with respect
to
> > eachother and exactly one light-year apart. We know this by
triangulation.
>
> You're already screwed. A relativistic universe has four distinct
> distances: luminosity (inverse square), angular diameter, parallax,
> and proper motion. No two of them need agree to maintain
> consistency. Clocks can only be synchronized by being local.
>
> There is no paradox. One twin travels relativistically, one twin
> stays at home. When they reunite the traveling twin is seen to have
> aged much less than its genetic double. The only "paradox" is the
> asymmetry (not the effect). If they *both* travel, you work out the
> relative hyperbolic rotation in 4-space vs. an outside observer to
> both.
>
identical accelerations. Can you corect my account of my observations of the
three instruments (speed by triangulation, other twin's clock, other twin's
speedo)?
> Acceleration breaks the symmetry of who ages faster. To accomplish
> that, the acceleration can occur before the clocks (or the twins)
> exist. Only reference frames matter.
>
I appreciate you trying to set me straight and I don't want to be awkward,
but I have devised this thought experiment specifically so people cannot say
that the twin that undergoes an accelleration is the one that goes slower.
That is why I would be grateful if you could refer to that example.
I'm sorry, but I'm not the shiniest apple in the barrel and I couldn't grasp
this example.
Stephen
Stephen Bint
"G=EMC^2 Glazier" <herbert...@webtv.net> wrote in message
news:2251-3F9...@storefull-2356.public.lawson.webtv.net...
> OH Yes there is. One twin is stationary on the Earth surface,as
> compared to its twin in a space ship going at "c" SR tells us at "c'
> time stops. Bert
>
you please look at the example I have given, in which neither twin is
stationary and tell me if you disagree with my account of what the twins
see?
The important thing about this example is that both twins undergo indentical
accelerations, in opposite directions, so any attempt to draw a distiction
between them based on different accelerations becomes impossible.
Let me know if it's lost from your server and I'll post it again.
Stephen
Androcles
"Stephen Bint" <bi...@iname.com> wrote a paradox in message
news:3f9e944a$0$116$65c6...@mercury.nildram.net...
Nothing wrong with your logic.
Fight relativists all you want, its a waste of time.
The reason there is a paradox is that time dilation can't happen. To see
where relativity goes wrong,
http://www.androc1es.pwp.blueyonder.co.uk/
Androcles
Androcles
> The NAVSTAR GPS clocks are set to 10.22999999543 MHz vs 10.23000000000 MHz
>
http://rattler.cameron.edu/EMIS/journals/LRG/Articles/Volume6/2003-1ashby/index.html
In other words, they run slow deliberately, and speed up in orbit, right?
Androcles
Dirk Van de moortel
"Stephen Bint" <bi...@iname.com> wrote in message news:3f9ed634$0$122$65c6...@mercury.nildram.net...
I think you don't want to know what the Bert believes.
You might want to know that in the beginning the Bert
used to be a Herb. We all wonder whether next year
the Bert will call himself a Terp or a Terk, and the year
after, whether the Terp will call himself a Perd or a Perl,
or perhaps whether the Terk will become a Kerl or a
Kerm. To survive on this forum one needs patience.
But you'll find that out soon enough.
One more thing: if you came here to learn some basic
facts about relativity, go away ASAP or even sooner.
Go to the FAQ and read some good introductory books
(see FAQ for an excellent list).
Alternative course of action: become our next Village
Idiot and join the club of Ken Seto, Richard Perry, Herb
and Bert Glazier, Androcles, and many many many
many others...
Dirk Vdm
Uncle Al
>
> "Uncle Al" <Uncl...@hate.spam.net> wrote in message
> news:3F9ED293...@hate.spam.net...
> > Stephen Bint wrote:
> > >
> > > I have telescopes at opposite side of my ship. They are both trained on
> a
> > > point on the other ship. By measuring the angles the telescopes are
> pointing
> > > I can calculate the distance to the other ship. Are you saying that
> wouldn't
> > > work?
> >
> > Won't work. That's distance by parallax. First, you can't measure
> > that small a subtended angle.
>
> At what distance does triangulation become impossible? Or is it impossible
> at any distance?
The ship is a kilometer long. The vertex is a lightyear distant
(9.4605284 в 10^12 km). What interior angle do you get vs. 90 degree
parallel lines to the distant point? How 'bout thermal jitter?
Remember that the two two ends of your ship are 3 microseconds apart.
You cannot communicate the data one end to the other with sufficient
accuracy. You don't now how long your baseline is to sufficient
accuracy to measure the necessary parallax angle.
How do you perform a meaningful measurement with a year delay? A month
after the photons you see departed, the viewed ship accelerated at a
constant (measured in-ship) 1 gee. Where is it now vs. your
measurement?
> Are you saying "can't measure that small a subtended angle" regardless of
> how good your technology is? Is there something inherently unmeasurable
> about small differences between angles?
>
> You realise, that in an example in which I have two spaceships that can
> travel at 0.75c, the standard of my engineering is very high.
"Ye canna' break the laws of physics."
> > Second, a relativistic universe has
> > four distinct distances: luminosity (inverse square), angular
> > diameter, parallax, and proper motion. No two of them need agree to
> > maintain consistency. Third, clocks can only be synchronized by being
> > local.
> >
> How far apart is not local? As long as I can get a fixed point from which to
> triangulate, I can calculate the distance and use the speed of light to
> correct for the time lag and be certain, that the clocks are synchronized,
> can't I?
"Local" is approximately "touching." If you assert ridiculous
accuracies, the universe will reply with equally ridiculous hurdles to
those accuracies. Special relativity is a self-consistent axiomatic
geometry. It contains no internal errors. There aren't any
loopholes, there aren't any paradoxes.
> Unless you can say why and at what distance triangulation fails to work.
The system is rigged. You cannot make a measurement of any kind that
will contradict the geometric construct. Everything is already
perfectly compensated at the starting gun to prevent the occurance of
contradiction. That is why relativity works.
There are two ways to assault relativity (or any theory),
1) Demonstrate an empirical contradiction, observation vs.
prediction. No dice.
<http://rattler.cameron.edu/EMIS/journals/LRG/Articles/Volume4/2001-4will/index.html>
Experimental constraints on General Relativity.
http://arxiv.org/abs/gr-qc/0308010
Nature 425 374 (2003)
<http://rattler.cameron.edu/EMIS/journals/LRG/Articles/Volume6/2003-1ashby/index.html>
http://www.eftaylor.com/pub/projecta.pdf
Relativity in the GPS system
2) Empirically counterdemonstrate a postulate, bringing down the
whole house of cards. No axiomatic system can defend its postulates -
or they would not be postulates.
http://www.mazepath.com/uncleal/qz.pdf
http://www.mazepath.com/uncleal/eotvos.htm
Stephen Bint
> Stephen Bint wrote:
> >
> > "Uncle Al" <Uncl...@hate.spam.net> wrote in message
> > news:3F9ED293...@hate.spam.net...
> > > Stephen Bint wrote:
> > > >
> > > > I have telescopes at opposite side of my ship. They are both trained
on
> > a
> > > > point on the other ship. By measuring the angles the telescopes are
> > pointing
> > > > I can calculate the distance to the other ship. Are you saying that
> > wouldn't
> > > > work?
> > >
> > > Won't work. That's distance by parallax. First, you can't measure
> > > that small a subtended angle.
> >
> > At what distance does triangulation become impossible? Or is it
impossible
> > at any distance?
>
> The ship is a kilometer long. The vertex is a lightyear distant
> parallel lines to the distant point? How 'bout thermal jitter?
> Remember that the two two ends of your ship are 3 microseconds apart.
> You cannot communicate the data one end to the other with sufficient
> accuracy. You don't now how long your baseline is to sufficient
> accuracy to measure the necessary parallax angle.
>
Or even better. Let's dispense with the initial synchronization. We'll
assume the clocks mark time at the same rate because a) they do when they
are local and b) they are identically constructed to the very highest
standards. Also, let's not be sticklers for the distance apart. Let's say,
we start roughly a light year apart. The exact terms I defined were to help
people visualise and are not necessary to the illustration. The important
distinction between this and previous examples is that both twins are
behaving identically with identical spaceships.
I would still like you to say whether the clock I observe on the other
spaceship at the different stages of my journey, is going faster or slower
than mine. I don't want to know how fast it's really going. I only want to
know how fast it appears to be going, as I observe it, at the five stages:
before acceleration, during acceleration, after a while at 0.75c, during
deceleration, and after deceleration.
It's a simple question, which you can answer with a few words for each
stage. eg:
before acceleration: same as my clock
during acceleration: getting slower and slower
mid journey, at constant 0.75c: slower, but constant
during decelleration: slower than mine but returning to same as mine
after decelleration: same as mine
But I suspect you will not, because you cannot do so without contradicting
yourself.
Stephen
Big Bird
> I would like to clarify the paradox by describing a simpler experiment, in
> which clear readings are taken as two spaceships fly toward a meeting point
> at 0.75c.
>
> The experiment:
>
> My twin and I, called A and B, are in spaceships, at rest with respect to
> eachother and exactly one light-year apart. We know this by triangulation. I
> synchronize my clock to the one on B's spaceship by setting mine exactly one
> year ahead of his, as I see it through my telescope.
>
> We intend to travel towards eachother very quickly and watch eachother's
> clocks and speedometers and use triangulation to keep track of our apparent
> speed, as we travel.
>
> At an agreed time, we accelerate rapidly towards one another, until our
> speedometers say 0.75c. We travel at 0.75c most of the way, then decellerate
> until we are at rest with respect to eachother, at a meeting point.
These "speedometers" of yours are quite interesting gadgets. I'd be
curious to hear *in what coordinate system* you're travelling at 0.75c
and how you are measuring that.
This is your cue to to either of the following two:
- you assert that this is some kind of "absolute speed" in which
case the issue ends here.
- you say something like "with respect to the coordinate system
in which they were at rest at the beginning".
In this latter case (the more interesting one) I ask you how you
measure your speed with respect to such a coordinate system. You would
then introduce a third clock that was at rest at the beginning wrt the
two twins in the spaceships and which does not perform any kind of
acceleration (and just to be on the safe side I'll ask you how you
ensure that, i.e. how you measure it.)
I will then argue that we can introduce a "third twin" here who sits
at the third clock. For simplicity's sake, let this third clock be in
the center between the two space ships.
NOW you not only have to contend with the observations of each other's
ships AND the observations of a third, centrally located clock (and
just to make sure: how do you use that third clock in order to measure
your speed?) but you also have to make sure you understand what the
third triplet in the middle sees when he observes the two space ships
approaching him.
Approximately at this point, you ought to be able to notice that this
is really just the plain old original version of the twin-"paradoxon"
except that you are using two travelling siblings instead of one.
The problem, of course, is that you were never able to figure out the
original scenario in terms of actually computing the elapsed proper
time in both coordinate systems and that you introduced this "new
improved" "paradoxon" because you imagined that this would allow you
to wave around your hands qualitatively and that way somehow disprove
something which you don't understand in the first place and which is
observationally confirmed millionfold every single day all over the
world.
OF COURSE you are free to sit down and actually compute what each of
the triplets sees at each stage of the process -- in the proper
quantitative terms. If you want to show any kind of self-contradiction
in special relativity, you'll have to bother USING special relativity.
For so far the only self-contradiction you've shown is in your own
vague muddled thoughts.
It isn't actually that hard -- if you need help, MTW chapter 6 hands
you all the tools and has a couple nice exercises on the issue: #6.3
is about the twin "paradox" itself, but you would probably benefit
from doing #6.4 and #6.5 as well (which are about using radar to
measure distance and speed and how their measurements will transform
relativistically).
Chapter 6 will also introduce you to the useful *extent* of 'an'
accelerated frame (some of the many fallacies in your original post),
the consequent differences between coordinate time and clock rate and
so forth -- I would guess if you were to work yourself through the
entire chapter (it's only 14 pages, unfortunately most of them 'track
2') you may find it rather rewarding.
Jon Bell
won't let me crosspost to a group that it doesn't carry]
In article <3f9e944a$0$116$65c6...@mercury.nildram.net>,
Stephen Bint <bi...@iname.com> wrote:
>I would like to clarify the paradox by describing a simpler experiment, in
>which clear readings are taken as two spaceships fly toward a meeting point
>at 0.75c.
I've worked this out using a speed of 0.8c rather than 0.75c because it
makes the arithmetic come out a bit simpler.
>The experiment:
>
>My twin and I, called A and B, are in spaceships, at rest with respect to
>eachother and exactly one light-year apart.
Again, to make the arithmetic simpler, I made you start out 8 light-years
apart, and for convenience I put the earth halfway in between, just to
serve as a reference point and destination.
>We know this by triangulation. I
>synchronize my clock to the one on B's spaceship by setting mine exactly one
>year ahead of his, as I see it through my telescope.
In my version, you (A) set your clock 8 years ahead of B's clock, as seen
through your telescope.
>We intend to travel towards eachother very quickly and watch eachother's
>clocks and speedometers and use triangulation to keep track of our apparent
>speed, as we travel.
>
>At an agreed time,
Let's suppose this is when both of our clocks show the beginning of
the year 2008, just to be specfic.
>we accelerate rapidly towards one another, until our
>speedometers say 0.75c. We travel at 0.75c most of the way, then decellerate
>until we are at rest with respect to eachother, at a meeting point.
Make that 0.8c instead of 0.75c, of course; and the meeting point is the
earth. Also, let's assume that the acceleration is rapid enough that we
can consider it to be practically instantaneous, in comparision with the
other time intervals in this problem. Including finite acceleration
periods only complicates the math without affecting the factors that
really matter here.
>Before I move,
Specifically, just an instant before you start to move,
>1. His speed, using triangulation, appears to be 0.
>2. His clock appears to be going at exactly the same rate as mine.
And, as you look at his clock through your telescope, you see it just
about to read the beginning of the year 2000. (You're now almost at the
beginning of 2008, and it takes 8 years for light to travel from him to
you.)
>3. His speedometer says 0.
This is presumably his speed relative to the earth.
>while I am accelerating,
[snip]
We'll ignore this part, because it's too short to be significant.
>while I am travelling at 0.75c, after allowing the image of his speedometer
>saying 0.75c to reach me across space,
>
>1. His speed, using triangulation, appears to be less than 1c.
>2. His clock appears to be going slower than mine, at a constant rate.
No, not slower, and not at a constant rate.
>3. His speedometer says 0.75c.
Note carefully that when you start out, there are 8 years' worth of light
signals on their way from him to you, carrying images of clock readings
ranging from 2000 up to the end of 2007. The fact that he has also
started to move isn't going to affect the propagation of those signals.
You have to receive all of those 8 years' worth of signals before you
receive any light that he emitted after he started to move.
Because you are now moving towards those signals as they approach you, you
will see them arrive *faster* than they otherwise would have, because of
the Doppler effect. Time dilation still figures into this, so you have to
use a relativistic Doppler shift equation rather than the classical one
that you encounter in freshman-physics books. But the overall effect is
nevertheless that you *see* his clock running faster, not slower.
To be specific, let's consider the light signals that he emits at the
beginning of each year (by his clock). Using the relativistic Doppler
shift equation (written in terms of the period, not frequency, of the
signals), we find that you will receive those signals at intervals of
(1 year) * sqrt ((1 - v/c) / (1 + v/c))
= (1 year) * sqrt ((1 - 0.8) / (1 + 0.8)) = 1/3 year
Therefore:
When your clock reads 2008, you will see (through your telescope) his
clock reading 2000. (this is of course when you start your journey)
When your clock reads 2009, you will see his clock reading 2003.
When your clock reads 2010, you will see his clock reading 2006.
When your clock reads (the beginning of) September 2010 (i.e. 2010
plus 2/3 year), you will see his clock reading 2008, and you will finally
see him starting to move.
Now we use the velocity-addition formula to calculate your relative
velocity, which turns out to be
(0.8c + 0.8c) / (1 + (0.8c)(0.8c)/c^2) = 0.97561c, approximately.
Therefore, his annual beginning-of-year signals now start to arrive at you
every
(1 year) * sqrt ((1 - 0.97561) / (1 + 0.97561)) = 1/9 year
that is, three times more often than before. How many of these signals
does he send before you meet?
In the earth's frame he (like you) is moving at 0.8c, therefore he (like
you) will take 5 years (in the earth's frame) to cover the 4 light-years
between his starting point and the earth (your meeting point). Applying
time dilation, we find that from his point of view the elapsed time of his
journey is 3 years. By symmetry, this is also the elapsed time, from
your point of view, of your own journey.
So, he sends three more yearly signals before you meet.
As calculated above, you receive these signals 1/9 of a year apart, i.e. 1
and 1/3 month apart, or about one month and ten days apart. Therefore:
When your clock reads about 10 October 2010, you will see his clock
reading (the beginning of) 2009.
When your clock reads about 20 November 2010, you will see his clock
reading (the beginning of) 2010.
When your clock reads (the beginning of) January 2011, you will see his
clock reading (the beginning of) 2011.
At this point, both of you have now arrived on earth. You can step out
of your spaceships, shake hands, and show each other your clocks, which
are running at the same rate and showing the same time.
By symmetry, he sees exactly the same things happening as he observes your
clock during his journey. And *neither* of you actually *sees* the
other's clock "run slow," because of the Doppler effect caused by your
approaching each other.
--
Jon Bell <jtbe...@presby.edu> Presbyterian College
Dept. of Physics and Computer Science Clinton, South Carolina USA
Stephen Bint
"Big Bird" <con...@biosys.net> wrote in message
news:df160b8f.03102...@posting.google.com...
own acceleration with a large mass on a horizontal spring balance. During
acceleration, the spring is compressed, so I can measure how much I have
accelerated.
But you are wasting your time, hoping to avoid ansering the question
directly by introducing technical difficulties. The reason both twins move
in this example is because people have skillfully sidestepped the paradox in
the past by saying that only the twin which accelerates goes slower.
Is it not the case that twins accelerating identically toward eachother will
see relativistic effects in their observation of the other? Or do they see
eachother going at 1.5c?
Do you doubt that the twins can establish that they are at rest to begin
with?
They could use red-shift as a guide, or send timing pulses back and forth.
So let's say, the twins start at some large but arbitrary distance apart and
do not bother synchronizing their clocks. The experiment is concerned purely
with how much time appears to have elapsed on the other twin's clock.
So, these are my observations of the rate of the other twin's clock,
compared to mine, according to my understanding of time dilation:
before acceleration: same as my clock
during acceleration: getting slower and slower
mid journey, at constant 0.75c: slower, but constant
during deceleration: slower than mine but returning to same as mine
after deceleration: same as mine
Do you disagree that these would be my observations? Care to correct them?
> The problem, of course, is that you were never able to figure out the
> original scenario in terms of actually computing the elapsed proper
> time in both coordinate systems and that you introduced this "new
> improved" "paradoxon" because you imagined that this would allow you
> to wave around your hands qualitatively and that way somehow disprove
> something which you don't understand in the first place and which is
> observationally confirmed millionfold every single day all over the
> world.
>
You don't know that. For all you know, I might simply take a delight in
watching the proponents of relativity bend over backwards to avoid answering
a direct question.
Stephen
Paul Cardinale
[snip]
You forgot RS. Do the math instead of waving your arms; you'll see
there's no problem.
Paul Cardinale
Paul Cardinale
[snip]
>
> Simple, it's not a paradox, it's an outright contradiction.
No, it only seems that way to people who can't/won't do the math.
Paul Cardinale
Uncle Al
THE ANGLE APPROACHES 90 DEGREES MORE CLOSELY AS THE BASELINE SHRINKS.
Work the math. THE SYSTEM IS RIGGED. YOU CANNOT WIN.
> Or even better. Let's dispense with the initial synchronization. We'll
> assume the clocks mark time at the same rate because a) they do when they
> are local and b) they are identically constructed to the very highest
> standards.
When do they start measuring elasped time? THE SYSTEM IS RIGGED. YOU
CANNOT WIN.
> Also, let's not be sticklers for the distance apart. Let's say,
> we start roughly a light year apart. The exact terms I defined were to help
> people visualise and are not necessary to the illustration. The important
> distinction between this and previous examples is that both twins are
> behaving identically with identical spaceships.
You don't know that. The essence of relativity is that information
transfer is limited by by lightspeed. THE SYSTEM IS RIGGED. YOU
CANNOT WIN. If they are twins then they were born locally. if you
want them to be a lightyear apart you must separate them, and at least
one must accelerate. If you build two clocks a lightyear apart you
cannot synchronize them. THE SYSTEM IS RIGGED. YOU CANNOT WIN.
Relativity is an axiomatic self-consist geometry. There are no
loopholes. THE SYSTEM IS RIGGED. YOU CANNOT WIN. If you thnk you
have, you have made a mistake.
> I would still like you to say whether the clock I observe on the other
> spaceship at the different stages of my journey, is going faster or slower
> than mine. I don't want to know how fast it's really going. I only want to
> know how fast it appears to be going, as I observe it, at the five stages:
> before acceleration, during acceleration, after a while at 0.75c, during
> deceleration, and after deceleration.
Nothing exists until local comparison. Since the clocks cannot be
sychronized to start, you have no elapsed time measurement. Look
stupid, play it backwards. You start with local synchronized clocks
THEN you shoot off into space. How do you know when to synchronously
stop the clocks? You do not.
You go back and read my triplet exposition. That has strictly local
clock synchronization (literally touching) and no clock accelerations
at all. It has no effect upon the time dilation or who ages slowly.
> It's a simple question, which you can answer with a few words for each
> stage. eg:
>
> before acceleration: same as my clock
> during acceleration: getting slower and slower
> mid journey, at constant 0.75c: slower, but constant
> during decelleration: slower than mine but returning to same as mine
> after decelleration: same as mine
>
> But I suspect you will not, because you cannot do so without contradicting
> yourself.
ACCELERATION IS IRRELEVANT. Get this through your head: The whole
experiment can be performed start to finish with no clock acceleration
at all. You can build the clocks after acceleration, trigger them by
sequential touching, write down the elasped time numbers, destroy the
clocks, then accelerate/decelerate to compare numbers, or radio them
in. You see what relativity predicts. I used 0.999c. A 1/gamma of
22.4 only accentuates the bottom line, as opposed to your 1/gamma of
1.5.
Stephen Bint
"Paul Cardinale" <pcard...@volcanomail.com> wrote in message
news:64050551.03102...@posting.google.com...
Are you saying that if I did the math I would be able to say what I see the
other twin's clock doing, eg:
before acceleration: same as my clock
during acceleration: getting slower and slower
mid journey, at constant 0.75c: slower, but constant
during deceleration: slower than mine but returning to same as mine
after deceleration: same as mine
You've done the math. Can you say what I would observe my twin's clock
doing?
Stephen
G=EMC^2 Glazier
thoughts. A person looking into the window of a space ship going at 'c'
sees its clock stopped. A person in the space ship going at 'c' looking
out the window and sees a clock and that clock will be stopped. If
relativity works it has to be the same effect. Bert Sorry I missed
your posting
Uncle Al
The units of acceleration are m/sec^2, the dimensions are
length/time^2. You can measure internal acceleration as nice as you
please. What does that mean when viewed externally from an inertial
frame of reference? You end up with relativity. You can accelerate
(measured internally) at one gee forever. At the same time you cannot
even begin to pull that off vs. an external viewer. Less than a year
into the exercise your externally measured velocity would go
asymptotic to lightspeed and your externally measured 3-space
acceleration would go asymptotic to zero as you merrily continued to
measure 1 gee internally. Until you can see that - and calculate it -
you are lost.
If you fell into a black hole an external observer would see you
descend into the event horizon forever, never quite making it. You
would see yourself simply fall through with no fancy pants anything
(aside from painful tidal distortion - and not even that for a really
massive black hole). There is no contradiction here. The math is
explicit. You do both, depending on the point of view.
Given any achievable velocities V1 and V2 and any finite lightspeed,
the sum of the velocities as viewed by any inertial observer cannot
exceed
(V1 + V2)/[1 +(V1)(V2)/c^2]
This is transformation of velocities parallel to the direction of
motion. For velocities at an arbitrary angle theta, Jackson gives
u_parallel = (u'_parallel + v)/(1+(v dot u')/c^2)
u_perp = u'_perp/(gamma_v(1+(v dot u')/c^2))
Relativistic doppler shift,
http://www.mathpages.com/rr/s2-04/2-04.htm
http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/reldop2.html
http://www.phys.ufl.edu/~rfield/PHY2061/images/chp39_2.pdf
> But you are wasting your time, hoping to avoid ansering the question
> directly by introducing technical difficulties. The reason both twins move
> in this example is because people have skillfully sidestepped the paradox in
> the past by saying that only the twin which accelerates goes slower.
Run the math. You are so terrifically wrong that you smoke. There is
no absolute set of coordinates to measure yourself against. Any
measurement you make is relativistic - and you cannot divine an
aberrant bottom line. There is none possible. The system is
perfectly rigged as assuredly as every Euclidean triangle's interior
angles sum to exactly 180 degrees and every spherical triangles'
interior angles always sum to more. There are no parallel lines on
the Earth. If you think you can draw a pair, you are wrong.
[snip crap]
Can one exactly square a circle? Sure! There are lots of quadratix
curves - Hippias', Ozam's, an Archimedian spiral, a cochlioid... Can
one square a circle by Greek rules using only a straightedge and
compass? Absolutely not! A circle cannot be squared using only
linear and quadratic operations.
When you spew you are poisoning the well. Special Relativity is a
self-consistent axiomatic geometry. it contains no mistakes, it has
no paradoxes. If you think otherwise, go searching for your mistake.
Others have pointed out some of your spectacular errors. Special
relativity spacetime interactions are not Newtonian or Euclidean
(Galilean) additions, they are hyperbolic (Lorentizan) rotations.
Relativity works exactly to spec,
<http://rattler.cameron.edu/EMIS/journals/LRG/Articles/Volume4/2001-4will/index.html>
Experimental constraints on General Relativity.
http://arxiv.org/abs/gr-qc/0308010
Nature 425 374 (2003)
<http://rattler.cameron.edu/EMIS/journals/LRG/Articles/Volume6/2003-1ashby/index.html>
http://www.eftaylor.com/pub/projecta.pdf
Relativity in the GPS system
Learn something before you spew. The relativistic 12-foot broomstick
fits into the 10-foot barn with both doors closed. You cannot say
otherwise.
Uncle Al
Spacetime interactions are not Euclidean, time and space are not
separable. Newton was wrong. You are mess. Get a few books on
special relativity and start reading. Learn something before you
spew.
--
Sam Wormley
Time speeds up (less gravity), slows down (time dilation), etc. The net need
is to make the clocks run a bit slow to correct for all the factors.
Stephen Bint
Thank you taking the time to produce such a lucid answer. I am genuinely
prepared to accept that you are right. Forgive me for not being able to do
the math. It is no less fascinating to me because of that.
I found a calculator at
http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/tdil.html
which gives the distance contraction and time dilations for any v > 0 and <
c.
For values greater than c it gives NaN. So what am I to do, to work out the
time dilation and distance contraction with respect to my twin?
You say:
> In the earth's frame he (like you) is moving at 0.8c, therefore he (like
> you) will take 5 years (in the earth's frame) to cover the 4 light-years
> between his starting point and the earth (your meeting point). Applying
> time dilation, we find that from his point of view the elapsed time of his
> journey is 3 years. By symmetry, this is also the elapsed time, from
> your point of view, of your own journey.
>
The calculator tells me that the distance contraction at 0.8c is 0.599. So,
I travel 4 light years in 3 years, but distance contraction gives me the
impression I only travelled about 2.4 light years in three years. I suppose
the experience of that is like seeing earth through a zoom lens.
The 8 light year gap between me and my twin closed in three years. That
suggests distance contraction to about 3/8 of its at rest value. Yet the
calculator (so I assume the contraction formula) gives NaN, for v = 1.6c.
Can you shed any light on this? In both the time dilation and distance
contraction formulae, v is used to mean relative velocity I presume. What is
my twin's velocity, relative to me?
"Jon Bell" <jtbe...@presby.edu> wrote in message
news:bnmu23$ml1$1...@jtbell.presby.edu...
Stephen Bint
What's the matter Al, can't answer the question?
sal
Stephen Bint wrote:
> "Big Bird" <con...@biosys.net> wrote in message
> news:df160b8f.03102...@posting.google.com...
>
> [snipped a bunch of stuff just cause there's a lot of it... ]
>> In this latter case (the more interesting one) I ask you how you
>> measure your speed with respect to such a coordinate system. You
>> would then introduce a third clock that was at rest at the
>> beginning wrt the two twins in the spaceships and which does not
>> perform any kind of acceleration (and just to be on the safe side
>> I'll ask you how you ensure that, i.e. how you measure it.)
>>
>
> No, I have two, finely engineered identical spaceships that measure
> their own acceleration with a large mass on a horizontal spring
> balance. During acceleration, the spring is compressed, so I can
> measure how much I have accelerated.
>
> But you are wasting your time, hoping to avoid ansering the question
> directly by introducing technical difficulties. The reason both twins
> move in this example is because people have skillfully sidestepped
> the paradox in the past by saying that only the twin which
> accelerates goes slower.
This isn't really quite right. I already posted (some of) the math on
this one earlier today, but I only posted it to alt.sci.physics --
didn't cross-post. If you want to see it go look at that newsgroup. I
also didn't take the extra step of correlating each leg of the journey
with projected observations -- that's an interesting exercise but I
don't have time tonight, so that posting just consists of the relevant
transformations to obtain the predicted elapsed times.
The problem one tends to stumble over here is that the clocks in two
inertial frames traveling at different speeds can't be synchronized --
you can sync them at _one_ event, but the farther away from that event
you get _in_ _space_ the farther out of sync the two frames get. This
is totally counter-intuitive and makes understanding this stuff at a gut
level really difficult: as soon as someone changes speed, the RELATIVE
TIMES of all points traveling at the same speed as that observer which
are separated from them by space changes. So, the heart of the matter
really is in the moments of acceleration, however brief they may be,
because that's when the observers are changing from one reference frame
to another.
>
> Is it not the case that twins accelerating identically toward
> eachother will see relativistic effects in their observation of the
> other? Or do they see eachother going at 1.5c?
They'll see each other approaching at something like 0.8c, just as you'd
expect.
>
> Do you doubt that the twins can establish that they are at rest to
> begin with? They could use red-shift as a guide, or send timing
> pulses back and forth.
The initial syncing up is not an issue, of course. Just send a light
beam back and forth once and you're done. They're in the same inertial
frame at that moment so that's not a problem.
>
> So let's say, the twins start at some large but arbitrary distance
> apart and do not bother synchronizing their clocks. The experiment is
> concerned purely with how much time appears to have elapsed on the
> other twin's clock.
>
> So, these are my observations of the rate of the other twin's clock,
> compared to mine, according to my understanding of time dilation:
>
> before acceleration: same as my clock during acceleration: getting
> slower and slower mid journey, at constant 0.75c: slower, but
> constant during deceleration: slower than mine but returning to same
> as mine after deceleration: same as mine
>
> Do you disagree that these would be my observations? Care to correct
> them?
What you've left out of this picture is that the whole thing goes into a
cocked hat when you change speed. Run the math, and you find out the
clocks get wildly out of sync at that point.
Here's a different but related example, that plays on the one real
asymmetry in the problem. All the measurements are done using the
LABORATORY frame (earth, fixed, stationary, whatever you want to call
it) -- the frame in which both twins are at rest before anybody
accelerates. Try measuring the distances in the SPACESHIP frame, and
you'll start to see the real problem. Here's a simple but dramatic
approach:
Give each twin a spaceship which is ONE LIGHTYEAR LONG. The nose is at
the Earth; the back end is a lightyear away. The twins are sitting in
the back seats. Now, try to figure out what happens when each twin hits
the "go" button.
To make it more dramatic, stick a "star drive 1000" engine to the hull
every 100 feet on both ships (that's a lot of engines!), and give the
engines enough power to bring the whole ship up to speed in a few
nanoseconds. (Impractical, but not physically impossible, right?) Now,
fire the engines all at the same time in the laboratory frame. What
happens to the starships?
Answer: They're ripped to shreds. When the stunned passengers try to
figure out what happened, they realize that the clocks on the motors are
all out of sync, despite the fact that they were in sync before they
started the motors. Strange...
>> The problem, of course, is that you were never able to figure out
>> the original...
Let's try to keep this civil. The twin paradox may be "trivial" but
it's still interesting and it's certainly confusing. And the variant
with two twins flying to the middle is interesting in its own right, as
is the variant with the really long space ship.
> You don't know that. For all you know, I might simply take a delight
> in watching the proponents of relativity bend over backwards to avoid
> answering a direct question.
Keep this in mind: Relativity is a mathematical model, nothing more.
SR consists largely of a bunch of linear transformations playing games
together. Its consistency isn't in doubt, any more than the consistency
of linear algebra is in doubt. What remains debatable is how well
either SR or GR represents reality -- mathematical models are never
identical to the real world.
SR's correspondence to reality has been confirmed in many cases to the
limits of accuracy of the measurements. But, the same thing could be
said of Newtonian mechanics. Neither is a complete description of the
universe we live in.
If you want an even more incomprehensible paradox go look at the
relativistic lever stuff on Androcles's website. I can't agree with
everything Androcles says but he's certainly put a lot of thought into
this stuff.
Oh -- and I almost forgot -- if you're looking for a textbook, Bernard
Schutz's "first course in general relativity" is in the same general
vein as Misner, Thorne and Wheeler, but I find it much more accessible,
and it's a lot skinnier and less than half the price. You could
sensibly read it on a bus, e.g., unlike MTW. (Schutz was one of
Thorne's students, IIRC.)
--
To email me directly, take out nospam and put back foobox.
Jeff Root
I think you set up a very good thought experiment, and I'm
surprised that no-one else has pointed out the flaw in your
analysis of it.
I agree that you can synchronize the clocks as long as you are
both motionless and can determine the distance between you.
> while I am accelerating,
>
> 1. His speed, using triangulation, rises to slightly less than 1c.
> 2. His clock appears to be getting slower and slower.
> 3. His speedometer rises to less than 0.75c.
You begin accelerating simultaneously, we hope. You don't see
him begin to accelerate until the light which left his ship at
the moment he started accelerating reaches you.
> while I am travelling at 0.75c, after allowing the image of
> his speedometer saying 0.75c to reach me across space,
>
> 1. His speed, using triangulation, appears to be less than 1c.
> 2. His clock appears to be going slower than mine, at a constant
> rate.
moving toward the light at 0.75c, so it takes 4/7 or 0.57 year
for the light to reach you from the instant his ship starts
accelerating. The light travels 4/7 of a light-year, and you
travel 3/7 of a light-year.
During the first 6/7 of your trip, you see your twin in his
spacecraft waiting for his clock to reach the agreed-on start
time. It is only in the final 1/7 of your trip that you see
his ship accelerate and speed toward you at very nearly c.
His clock is slowed down, but appears to you to be speeded up.
There are two reasons for that. One is that his clock is moving
toward you, and you are moving toward his clock, so the light
from his clock at each successive tick has a shorter distance
to travel to reach you. The second reason his clock appears to
be speeded up is that you are slowed down. Events that are not
in your accelerated frame of reference appear to you to happen
faster than normal.
It will take you 8 months to travel 1/2 light-year at 0.75c.
To you, it will be only 7 months or so (I didn't calculate it).
You will see your twin's clock madly go through about 7 months
of ticking in the final month of your trip.
-- Jeff, in Minneapolis
Subtract 1 from my e-mail address above for my real address.
.
Richard
Right, one argument for symmetrical systems, and another for
asymmetrical systems, even though acceleration doesn't enter into either
equation. Just lovely.
Tell me this: You're traveling along through space in your little space
capsule and run into your twin who has also been frolicking about the
galaxy. You know only this, that by the time you spot one another you
are x meters distant and your relative velocity is v, and constant. You
send a signal to your twin, he beams one back, etc. etc. you get your
clocks as synchronized as you can with this sort of feed back, er GPS
style.
Now you are left with exactly the OP's system, OTOH it isn't necessarily
the OP's system, but how the hell can you know? Thus the same result
must follow regardless of acceleration history, moreover the lorentz
transform couldn't care less about acceleration histories, it only
requires v in the now.
Since you have shown that there will be no difference in the aging of
the twins during this sequence, then the argument applies necessarily to
any two twins in uniform relative motion.
SR may be internally consistent, but its adherents damn sure aren't.
Richard Perry
Big Bird
> No, I have two, finely engineered identical spaceships that measure their
> own acceleration with a large mass on a horizontal spring balance. During
> acceleration, the spring is compressed, so I can measure how much I have
> accelerated.
Fortunately I already gave you the hint in my last post why this is
nonsense. MTW, ch6; six or seven pages in. Compare g and \xi, then
accelerate: to measure anything, your test mass will have to move in
the frame of the ship - compare g and \xi now. Compute 1+g*\xi for the
rest-position of the mass and for its current position. NOW tell me
how you are going to use your measurement to compute the *velocity* of
the ship (hint: no amount of acceleration will allow you to exceede c)
I note that you were unable to answer the question
>> *in what coordinate system* you're travelling at 0.75c
>> and how you are measuring that.
Of course you were, as you haven't grasped yet that a coordinate
system is a *local* concept. Special Relativity deals with coordinate
systems only to the extent that they are locally defined by
*Observers* -- these latter ones (observers) being the fundamental
entity.
Had you simply read the text of ch6 in MTW and ignored all the math,
you'd know that there is no such thing as "the" reference of an
accelereated observer.
> But you are wasting your time, hoping to avoid ansering the question
> directly by introducing technical difficulties.
Something that is undefined, in self-contradiction or *in principle*
impossible is hardly a "technical difficulty".
> So, these are my observations of the rate of the other twin's clock,
> compared to mine, according to my understanding of time dilation:
>
> before acceleration: same as my clock
> during acceleration: getting slower and slower
> mid journey, at constant 0.75c: slower, but constant
> during deceleration: slower than mine but returning to same as mine
> after deceleration: same as mine
Never in the world are you going to observe such nonsense. As would be
trivially obvious to yourself if you simply made the effort to justify
to yourself what you are measureing and how you are measuring it.
(Another obvious hint: The light that you keep receiving in your
fabled telescope was emitted *when*?)
>
> Do you disagree that these would be my observations? Care to correct them?
>
Contrary to the continued assertion of you religious whackos, nobody
has to "prove you wrong": YOU are making the assertion up there that
you are going to observe certain things, the burden of proof is
strictly on YOU to show that this is what you would indeed observe.
This requires little less than figuring out what special relativity
actually, truly SAYS about accelerated coordinate systems. (Yet a
another hint: it disagrees with you).
Androcles
have frequent corrections made to keep it on time, and another ground
station has been added to do so because two were insufficient. The reason,
of course, is that the satellite clocks are running slightly slow as anyone
with an ounce of common sense would expect.
A relativist will reduce the clock rate because his magical number theory
predicts he should. A scientist would investigate the physical cause, if
there really was one. Not all scientists are physicists, some are chemists.
Relativists are not scientists. Go poke your relativity into chemistry for a
change. Maybe you can slow down or speed up some chemical reactions.
Androcles
Sam Wormley
>
> Yeah, yeah, yeah... seen all that before. As it happens, the system has to
> have frequent corrections made to keep it on time, and another ground
> station has been added to do so because two were insufficient. The reason,
> of course, is that the satellite clocks are running slightly slow as anyone
> with an ounce of common sense would expect.
>
> A relativist will reduce the clock rate because his magical number theory
> predicts he should. A scientist would investigate the physical cause, if
> there really was one. Not all scientists are physicists, some are chemists.
> Relativists are not scientists. Go poke your relativity into chemistry for a
> change. Maybe you can slow down or speed up some chemical reactions.
Androcles hasn't educated himself about GPS uplinks, which primarily
update the Ephemeris date for each satellite transmitted in the GPS
navigation message.
See: http://www.edu-observatory.org/gps/gps_books.html
Androcles
> THE SYSTEM IS RIGGED. YOU CANNOT WIN.
Mathematics is a system of proving theorems based on primitive axioms that
cannot possibly be broken down to simpler concepts. If they can be, then
they are not axioms. Mathematicians have no faith, they want proof.
Religion is a system based on faith, that which is to be believed without
proof.
Relativity is a religion, based on two postulates, the PoR, an axiom, and
the 'postulate' that the speed of light is independent of the motion of the
source in empty space.
That so-called postulate is not an axiom, it cannot be. It can be tested by
experiment. Being testable, it doesn't qualify.
It never has been tested.
The mathematician breaks down the structure to its basic building blocks
before constructing a fine ediface with a solid base, and calls it a
theorem. he can then construct greater theorems from lesser theorems The
physicist does the same, delving deeper into the workings of the atom.
The relativist builds an unstable pyramid, standing on its point, and is
constantly propping it up as it wobbles, and there are a number of us
pushing at it to topple it.
The rigging holding it up is wearing thin, and such assertive claims are
pretty desperate. Shouting them only underscores the desperation.
Assertion carries no weight.
Prove the system is rigged as well.
Androcles
Androcles
"sal" <beli...@nospam.com> wrote in message
news:3F9F2E5E...@nospam.com...
> I can't agree with
> everything Androcles says but he's certainly put a lot of thought into
> this stuff.
MMX contains a deliberate error and how-to-build-a-time-machine is obviously
facetious, but if you have any other disagreements I'll be pleased to
discuss them. If I'm in error I'll correct. I gave acknowledgement to Martin
Gradwell when he found I had mistakenly assumed the mirror to be material to
the argument.
Androcles
Androcles
> Jon,That calculator is rigged, just as 'Uncle' Al said. I put in a negative
velocity, and various other tests. It doesn't work according to the
equation. R Nave (the name at the bottom) is a knave.
Androcles
Robert Calvert
> >
> > http://scienceworld.wolfram.com/physics/SpecialRelativity.html
> >
>
http://math.ucr.edu/home/baez/physics/Relativity/SR/TwinParadox/twin_intro.html
> > http://www.edu-observatory.org/gps/gps_books.html#Relativity
>
> Thank you for those. The first link is no use to me in this context,
though
> it does describe Einstein's theories very well.
>
> The page at the second link attempts to solve the paradox using the
> acceleration argument, which does not survive the problem as I have laid
it
> out in this thread. It only works when one twin remains stationary.
>
> The third one is interesting. It never occurred to me that obsevations
> relevant to relativity would be produced as a spin-off of GPS. I didn't
read
> them thoroughly, so I was left unsure as to whether the clocks are brought
> forward in order to compensate for the sum of the effects of speed and low
> gravity. Are they?
>
You might be interested to know that the same problems described would be
encountered even in a strictly Newtonian universe. We can assume that the
microwave radiation is changing speed and being Doppler shifted as a result
of the earth's gravity and the motion of the satellites as Newton would
probably argue. Or we can assume that space-time is being warped as a result
of the earth's gravity and the time dilation effects that are coming into
play as Einstein would probably argue. Ether way, the effect would be the
same (in this context) and the same corrections would be required to make
the system work.
I once read an article in a science textbook about how Einstein's General
Theory of Relativity was "proven correct" when it was found that light can
bend under the influence of gravity. Even though it's not likely that this
would prove Einstein's theory wrong, I would be hard pressed to see how this
could prove it right.
Robert
> Will you hazard a guess at why my example leads to an inescapable paradox?
>
> Stephen
>
>
>
Helmut Wabnig
wrote:
>
>"Uncle Al" <Uncl...@hate.spam.net> wrote in message
>news:3F9EA86B...@hate.spam.net...
>> Stephen Bint wrote:
>> >
>> > I would like to clarify the paradox by describing a simpler experiment,
>...............
>I'm sorry, but I'm not the shiniest apple in the barrel and I couldn't grasp
>this example.
>
>Stephen
>
Honest person, you are.
To subsumize and distill the essence:
Special relativity does not deal with acceleration,
uniform motion is supposed.
Revise your examples that way.
w.
Helmut Wabnig
<jp006...@blurbblueyonder.co.uk> wrote:
>
>"Stephen Bint" <bi...@iname.com> wrote a paradox in message
>news:3f9e944a$0$116$65c6...@mercury.nildram.net...
>
>Nothing wrong with your logic.
>Fight relativists all you want, its a waste of time.
>The reason there is a paradox is that time dilation can't happen. To see
>where relativity goes wrong,
>http://www.androc1es.pwp.blueyonder.co.uk/
>Androcles
>
How do you calculate the GPS clock corrections?
w.
Androcles
> Androcles hasn't educated himself about GPS uplinks, which primarily
> update the Ephemeris date for each satellite transmitted in the GPS
> navigation message.
>
Yep... You did say Ephemeris DATE, didn't you?
My point exactly.
Androcles.
Robert Calvert
"Helmut Wabnig" <hXXXw...@aXXXon.at> wrote in message
news:3lrupvc6gg7m50l74...@4ax.com...
Robert
Androcles
"Helmut Wabnig" <hXXXw...@aXXXon.at> wrote in message
> How do you calculate the GPS clock corrections?
>
> w.
No calculation necessary.
You upload fresh data to the satellites on a regular basis to correct the
error introduced by GR. In other words, tell them the right time. Since
thet system was built, it has been necessary to add an additional ground
station to upload them more frequently.
Androcles
Paul R. Mays
"Robert Calvert" <Herc...@pcstarnet.com> wrote in message
news:vputpum...@corp.supernews.com...
There are no paradox's ... the illusion of paradox exists when
the existing laws governing the construct are incomplete...
And many mathematical constructs fall into this category...
Until we learn the rules of causation we will always be faced
with laws of effect which will fail at some point and when
they do we end up with the illusion of paradox, infinity and
constant.
Paul R. Mays
----------------------------------------------------------------------------
-
Some where within the Quantum State
Http://Paul.Mays.Com/story.html
http://paul.mays.com/mayday.html
http://paul.mays.com/rainy.html
"Physics is experience, arranged in economical order."
-
Ernst Mach
Androcles
"Paul R. Mays" <u...@ftc.gov> wrote in message
news:nZednQBK4Jm...@giganews.com...
> There are no paradox's ... the illusion of paradox exists when
> the existing laws governing the construct are incomplete...
True. That's the whole point. SR is paradoxical because its existing laws
are 'incomplete'.
The 'laws' are 1)
"light is always propagated in empty space with a definite velocity c which
is independent of the state of motion of the emitting body"
and 2)
"In agreement with experience we the further assume the quantity
2AB/(t'A-tA) = c
to be a universal constant- the velocity of light in empty space."
I wouldn't call them 'incomplete', though. I call them downright wrong.
Androcles
See
http://www.androc1es.pwp.blueyonder.co.uk/Fundamental.htm
for unfairly choosing the biggest half of the apple.
alen
> Is that what would happen? If it is, we have an inescapable paradox. If I
> witnessed those events, then my twin must be younger than me. His clock
ran
> at varying degrees of slowness, but never faster than mine, so his clock
> must be behind mine.
>
> But of course, because my twin behaved identically to me, he must have
had
> an identical experience and my clock must be behind his.
>
> These contradictory and mutually exclusive predictions cannot both be
true,
> nor can only one, because the twins have behaved identically. Which
leaves
> "neither perdiction is true", as the only conceivable possibility.
>
> If I have made a mistake in describing the experience of time dilation in
> this example, please point it out.
>
> Stephen
The responses to your experiment show the contortions of
thought by which people try to avoid the paradox. I say that
this is because SR is true, and the paradox is real also, but
SR is not understood in the way necessary to answer it.
I have a different view of SR, and will give you my answer:
The twins are identical in all respects and you can set up their
relationship so that that will be the case. Each twin has his
own reference frame, and sees the other twin travelling in it.
Each twin sees the other's clock running slow, and this
contradiction obviously cannot represent what the clock times
'really' are. I have argued elsewhere that each twin does not
see the other's clock as it is, but as it was in the past.
This effect only exists for each as a result of the relative velocity
of the apparently slower other clock. Both clocks always
show the same time in their own frame and, when the
twins meet and decelerate, and the velocity is reduced to
zero, each twin will think the other clock is speeding
up until they show the same time when the velocity is
zero. SR causes a moving clock to be seen via its history,
but the clock itself is not altered by the relative velocity.
Alen
Stephen Bint
"Androcles" <jp006...@blurbblueyonder.co.uk> wrote in message
news:TdInb.2090$0E5....@news-binary.blueyonder.co.uk...
run high because the proponents of relativity have invested a great deal of
themselves in learning all the maths concerned with it, so they are strongly
averse to finding out that all that hard work was a complete waste of time.
Stephen Bint
answers for relative speeds greater than 1c?
Surely they must, or they are a bit limited. What am I supposed to do when
two observers fly in opposite directions at 0.8c?
Paul Cardinale
That is not correct. SR can handle acceleration just fine. In fact,
you can use SR to resolve the twin paradox when the travelling twin is
always accelerating/decelerating.
Paul Cardinale
Paul Cardinale
> "Paul Cardinale" <pcard...@volcanomail.com> wrote in message
> news:64050551.03102...@posting.google.com...
> > Richard <no_mail...@yahoo.com> wrote in message
> news:<3F9EC1A1...@yahoo.com>...
> >
> > [snip]
> >
> > >
> > > Simple, it's not a paradox, it's an outright contradiction.
> >
> > No, it only seems that way to people who can't/won't do the math.
> >
> > Paul Cardinale
>
> Are you saying that if I did the math I would be able to say what I see the
> other twin's clock doing,
Of Course.
> eg:
>
> before acceleration: same as my clock
> during acceleration: getting slower and slower
> mid journey, at constant 0.75c: slower, but constant
> during deceleration: slower than mine but returning to same as mine
> after deceleration: same as mine
>
You got it wrong.
> You've done the math. Can you say what I would observe my twin's clock
> doing?
>
During your acceleration, you would observe the other twin's clock to
be going faster than yours.
Paul Cardinale
Stephen Bint
"alen" <al...@westserv.net.au> wrote in message
news:01c39e20$cb676980$017ea6cb@default...
This is a plausible suggestion someone else has made, that an opposite
effect to time dilation, which I am inclined to call time contraction,
occurs in objects you observe as decelerating with respect to you. I think
if that occurs, it may save the theory from the paradox.
But there is a problem with it. We use distance contraction and time
dilation to explain why the twins do not see eachother going faster than
light.
It is surely possible to devise a situation in which they are travelling at
say, 0.75c in opposite directions so that distance contraction and time
dilation must be employed to shrink their apparent speed with respect to
eachother, and then have both ships accelerate or decelerate to cause the
opposite effect, time contraction, so that time dilation is cancelled and
the twins will not be prevented from seeing eachother going faster than
light.
What do you think, is that possible?
Stephen
Stephen
Stephen Bint
"Paul Cardinale" <pcard...@volcanomail.com> wrote in message
news:64050551.03102...@posting.google.com...
news:<3lrupvc6gg7m50l74...@4ax.com>...
> > On Tue, 28 Oct 2003 20:45:17 -0000, "Stephen Bint" <bi...@iname.com>
> > wrote:
> >
> > >I'm sorry, but I'm not the shiniest apple in the barrel and I couldn't
grasp
> > >this example.
> > >
> >
> > To subsumize and distill the essence:
> >
> > Special relativity does not deal with acceleration,
> > uniform motion is supposed.
> >
>
> That is not correct. SR can handle acceleration just fine. In fact,
> you can use SR to resolve the twin paradox when the travelling twin is
> always accelerating/decelerating.
>
> Paul Cardinale
Paul,
You have said in another thread, that the twins see eachother's clocks going
faster during acceleration. What if they are travlleing at speed with respct
to eachother and accelerating at the same time? Do the speeding up/slowing
down effects of time dilation cancel eachother out?
Stephen
Paul R. Mays
that is variable at the expansion rate of the universe so its only
observable
and expressible as a constant to man due to scale of variability in that
the variance is not detectable within the life span of our solar system.
And the mechanism of variability is the separation distance of physical
particles due to the inverse tensor nature (elastic mode) of the Quantum
State between all physical particles... And that all " particles" that
display the aspect of duality are not "particles" but EM waves observed
with the intrinsic bias of the quantum connection of the observer and the
observed and any device designed to observe.
So having that view generally sticks me into the KooK bin ...
Paul R. Mays
----------------------------------------------------------------------------
-
Some where within the Quantum State
Http://Paul.Mays.Com/story.html
http://paul.mays.com/mayday.html
http://paul.mays.com/rainy.html
"Science tries to answer the question: “How?” How do
cells act in the body? How do you design an airplane
that will fly faster than sound? How is a molecule of
insulin constructed? Religion, by contrast, tries to
answer the question: “Why?” Why was man created?
Why ought I to tell the truth? Why must there be sorrow
or pain or death? Science attempts to analyze how
things and people and animals behave; it has no concern
whether this behavior is good or bad, is purposeful or
not. But religion is precisely the quest for such
answers: whether an act is right or wrong, good or bad,
and why."
- Warren Weaver (1894–1978)
Jon Bell
Stephen Bint <bi...@iname.com> wrote:
>
>Surely they must, or they are a bit limited. What am I supposed to do when
>two observers fly in opposite directions at 0.8c?
You use the relativistic velocity-addition equation to find out how fast
each observer appears to be moving, from the other's point of view, as I
did in my example. You get the same result regardless of whether they are
moving towards each other (as in my example) or away from each other. See
my previous posting for the number. As I recall, it was approximately
0.97c.
Helmut Wabnig
Cardinale) wrote:
>
>That is not correct. SR can handle acceleration just fine. In fact,
>you can use SR to resolve the twin paradox when the travelling twin is
>always accelerating/decelerating.
>
>Paul Cardinale
I know, there are some efforts, to extend SR.
Far beyond the Original Poster's intentions :-)
w.
Helmut Wabnig
>>
>I am still giving relativity a chance to be true, but I expect emotions to
>run high because the proponents of relativity have invested a great deal of
>themselves in learning all the maths concerned with it, so they are strongly
>averse to finding out that all that hard work was a complete waste of time.
Nice.
Do you know how to calculate GPS clock corrections
with simpler math?
w.
Helmut Wabnig
wrote:
>
>Surely they must, or they are a bit limited. What am I supposed to do when
>two observers fly in opposite directions at 0.8c?
>
>
You are supposed to apply SR formulas :-)
w.
Dirk Van de moortel
"Helmut Wabnig" <hXXXw...@aXXXon.at> wrote in message news:8710qvkjmhuoitt0o...@4ax.com...
> On 29 Oct 2003 06:35:41 -0800, pcard...@volcanomail.com (Paul
> Cardinale) wrote:
>
> >
> >That is not correct. SR can handle acceleration just fine. In fact,
> >you can use SR to resolve the twin paradox when the travelling twin is
> >always accelerating/decelerating.
> >
> >Paul Cardinale
> I know, there are some efforts, to extend SR.
SR treatment of accelerated motion:
http://groups.google.com/groups?&threadm=a3M1b.82977$F92....@afrodite.telenet-ops.be
> Far beyond the Original Poster's intentions :-)
Indeed. The OP's problem can be handled perfectly without
accelerations, just like the standard twin-paradox.
Besides, I'm quite sure that the OP doesn't even know the
difference between speed and acceleration.
And his intensions... that's yet another matter ;-)
Dirk Vdm
Dirk Van de moortel
"Helmut Wabnig" <hXXXw...@aXXXon.at> wrote in message news:hb10qvgo4a2ji62gn...@4ax.com...
Wow, I hadn't seen that one :-)
http://users.pandora.be/vdmoortel/dirk/Physics/Fumbles/AChance.html
Title: "Giving Relativity A Chance"
A fancy entrance :-)
Dirk Vdm
James Dolan
stephen bint <bi...@iname.com> wrote:
|I care, that people in charge of billion-dollar particle
|accelerators, believe a theory which cannot possibly be true. So I'll
|keep my life on hold for the moment.
hi. let me try to explain why the theory that those people believe
can be true without any logical contradiction.
it's like this:
say you have a long, straight railroad track, say 1000 miles long.
and by the side of the track there are milepost signs, spaced exactly
a mile apart. and you have a red train at one end of the track, and a
blue train at the other end of the track. and at exactly noon on the
day before halloween, both trains start heading towards each other,
slowly at first, then faster, and then slowing down again so they
don't crash when they meet at the exact midpoint of the track. and
the two trains both follow the exact same pattern of acceleration and
deceleration, and they both always stay under the speed limit of 100
miles per hour. and on top of the red train there's a box full of red
pigeons, and there's a guy who stands next to the box, and every time
that the train passes another milepost sign, he reaches into the box
and releases another red pigeon who starts flying at exactly 100 miles
per hour towards the blue train. and on top of the blue train there's
a guy with a catcher's mitt who catches the red pigeons and puts them
into a box. and there's _another_ guy on top of the blue train who
stands next to a box full of blue pigeons and releases one blue pigeon
at every milepost to fly at exactly 100 miles per hour towards the red
train, and there's _another_ guy on top of the red train with a
catcher's mitt who catches the blue pigeons and puts them in a box, so
the situation is really symmetrical between red and blue.
and you're a passenger on the red train, watching the pigeons with
another guy sitting next to you, and this other guy says: "hey, we're
losing red pigeons faster than we're gaining blue pigeons! we're
losing out on the pigeon trade! those guys on the other train are
holding out on us, pigeon-wise!". and he describes to you a
complicated calculation which purports to show that even though the
precise number of pigeons of each color on each train at each moment
varies in an annoyingly complicated way, nevertheless the number of
red pigeons transferred from the red train to the blue train will
always be more than the number of blue pigeons transferred from the
blue train to the red train, even at the end of the trip when the two
trains meet at the midpoint and stop and all the pigeons are back in
the boxes.
and you try to explain to the guy that he must be mistaken, that as
long as the situation is symmetrical between red and blue, the pigeon
trade will end up being a fair trade if there's a final accounting of
pigeons in the end. and the guy keeps on coming up with a bunch of
complicated variations involving three colors of giant carnivorous
pigeons, and it takes a long time to get him to understand the mistake
that he's making. particularly if there's a bunch of other guys
who're all trying to explain the same thing at the same time except
that they're mostly a bunch of morons who only _think_ that they
understand how it all works.
(the blue pigeons received by the red train from the blue train
represent "progress reports" that the red train receives about the
progress made by the blue train in traveling towards its destination.
yep it's confusing when there's a gap between "progress actually made"
and "progress confirmed by progress reports", but if you think about
it carefully enough it all works out just fine.)
--
[e-mail address jdo...@math.ucr.edu]
Androcles
Math is useful art, and it has a host of applications. It is also jsut a
tool if you use it that way.
Androcles
Androcles
"Helmut Wabnig" <hXXXw...@aXXXon.at> wrote in message
news:hb10qvgo4a2ji62gn...@4ax.com...
they drift as a result of GR miscorrections.
Androcles
Paul Cardinale
Since speed and distance would be constantly changing, such
cancellation could only occur at one point, it could not occur over a
period of time.
Paul Cardinale
Martin Hogbin
"Stephen Bint" <bi...@iname.com> wrote in message news:3f9e944a$0$116$65c6...@mercury.nildram.net...
.>
> My twin and I, called A and B, are in spaceships, at rest with respect to
> eachother and exactly one light-year apart. We know this by triangulation.
You do not make clear what you mean by 'triangulation'. Is a
third observer or object involved?
I presume the twins are in an inertial frame to start with.
>I
> synchronize my clock to the one on B's spaceship by setting mine exactly one
> year ahead of his, as I see it through my telescope.
OK.
> We intend to travel towards eachother very quickly and watch eachother's
> clocks and speedometers and use triangulation to keep track of our apparent
> speed, as we travel.
How are you going to use triangulation to track speed?
What do you mean by 'apparent speed'? Do you mean
'relative speed'?
> At an agreed time, we accelerate rapidly towards one another, until our
> speedometers say 0.75c.
Is that 0.75c relative speed or do they both travel at
0.75c in the starting frame.
> We travel at 0.75c most of the way, then decellerate
> until we are at rest with respect to eachother, at a meeting point.
>
>
> Before I move,
>
> 1. His speed, using triangulation, appears to be 0.
> 2. His clock appears to be going at exactly the same rate as mine.
> 3. His speedometer says 0.
OK
> while I am accelerating,
> 1. His speed, using triangulation, rises to slightly less than 1c.
Is that his speed relative to you?
> 2. His clock appears to be getting slower and slower.
Depends on what you mean by 'appears'.
> 3. His speedometer rises to less than 0.75c.
How can this be? Say it is a digital meter. Either it reads
0.75c or it does not. The reading must be the same in both
frames.
<snip>
> Is that what would happen? If it is, we have an inescapable paradox. If I
> witnessed those events, then my twin must be younger than me. His clock ran
> at varying degrees of slowness, but never faster than mine, so his clock
> must be behind mine.
>
> But of course, because my twin behaved identically to me, he must have had
> an identical experience and my clock must be behind his.
>
> These contradictory and mutually exclusive predictions cannot both be true,
> nor can only one, because the twins have behaved identically. Which leaves
> "neither perdiction is true", as the only conceivable possibility.
> If I have made a mistake in describing the experience of time dilation in
> this example, please point it out.
You have made so many mistakes and suffer from so many
misunderstandings about the subject that it is hard to
write anything helpful.
You need to consider how measurements are made in a single
inertial frame, and make it clear what measurements you are
referring to for a start.
You also need to make clear when you are referring to
what is seen and what is measured.
Try this book for a start.
Spacetime Physics : Introduction to Special Relativity
by Edwin F. Taylor, John Archibald Wheeler, Archibald Wheeler (Contributor)
Paperback - 312 pages 2nd edition (December 1992)
W H Freeman & Co.; ISBN: 0716723271
Martin Hogbin
Martin Hogbin.
Robert Calvert
rate....?
I find it interesting that nobody (so far as I know) has ever tried to
explain Einstein's Theory of Relativity (not to be confused with the
Classical Theory of Relativity which was around before Einstein's day) by
presenting examples of how clocks would compare after various experimental
scenarios.
Let's say that, out in interstellar space, we have three spacecraft and two
markers that are 100 light hours apart. In the first experiment, spacecraft
A is positioned at marker #1. Spacecraft B is positioned at marker #2.
Spacecraft C is positioned in the middle and remains stationary relative to
the markers throughout all the experiments. After they all synchronize their
clocks, spacecraft A and B rapidly accelerate toward each other until their
clocks should be running at one tenth normal speed relative to spacecraft
C's clock. After spacecraft A and B have passed each other and are both
approaching the opposite marker, they stop and all three compare each others
times. What would the clocks read?
Now let's try another experiment. Both spacecraft synchronize their clocks
and start toward each other from the markers just like before. Only this
time, when spacecraft A and B approach each other, spacecraft A makes an
about face and matches the speed and direction of spacecraft B so that both
spacecraft are now traveling in the same reference frame. They both continue
like this until they reach the marker that spacecraft B started from, then
they both stop. What would all three clocks read now? It would also be
useful to know how the clocks on spacecraft A and B would compare
immediately after spacecraft A made it's about face and entered the
reference frame of spacecraft B.
We could also try a thought experiment in which an alien solar system has
always been traveling at close to the speed of light relative to our own. In
this case, when we and the inhabitants of the other solar system observed
each other and compared each others clocks, who would be inhabiting the
privileged frame of reference? Would we conclude that their clock is running
slower than ours? Or would they conclude that our clock is running slower
than theirs?
When you stop and think about it, Einstein's theory only makes sense if we
conclude that motion is not relative after all.
Robert
> Paul Cardinale
Stephen Bint
> "Stephen Bint" <bi...@iname.com> wrote in message
news:<3f9fd6ca$0$119$65c6...@mercury.nildram.net>...
> > Paul,
> >
> > You have said in another thread, that the twins see eachother's clocks
going
> > faster during acceleration. What if they are travlleing at speed with
respct
> > to eachother and accelerating at the same time? Do the speeding
up/slowing
> > down effects of time dilation cancel eachother out?
> >
>
> Since speed and distance would be constantly changing, such
> cancellation could only occur at one point, it could not occur over a
> period of time.
>
> Paul Cardinale
If two spacehips are approaching each other in opposite directions after
accelerating to 0.75c from a common inertial frame, and one of them
accelerates to 0.95c (relative to the initial frame), then during that
period of acceleration, the clock on both ships will be speeded up, by the
acceleration, which will cancel out the time dilation to some extent, will
it not?
I have to ask, because acceleration is not a factor in the time dilation
formula, is it? So this is beyond the theory as it has so far been stated.
Stephen
Stephen Bint
You speak my language. Can you clarify please, whether there is someone on
the blue train making a similar complaint about being shortchanged for
pidgeons. I suppose there must be. Sorry if I am missing the point, but I am
trying, honestly.
Are you saying, like some of the others, that there will be a flood of
pidgeons at the end, making it all come out alright?
Apart from the fact that the reversal of time dilation during acceleration
is not a feature of the original theory, it raises even more difficult
questions. If the amount of time dilation and distance contraction required
to prevent us seeing eachother going faster than light is precise as the
formula suggests, then its reduction or reversal by acceleration will throw
a spanner in the works, won't it?
Stephen
"James Dolan" <jdo...@math-rs-n03.math.ucr.edu> wrote in message
news:bnp2rv$eii$1...@glue.ucr.edu...
Patrick Reany
In SR, all reference frames are NOT equivalent for the description of
nature. The inertial frames are preferred in that the laws of physics
do not distinguish between them in an absolute sense -- that is, they
do not provide a necessary meaning to "absolute velocity." However,
Einstein said that in SR accelerated motion is considered as
"absolute." The upshot of this is that in SR all motion is not
relative after all (who ever said it was anyway?). One has to advance
to GR to get full equivalence for all reference frames.
Read Einstein's essays on this in his book Ideas and Opinions.
Patrick
puppe...@hotmail.com
[snip]
> You might be interested to know that the same problems described would be
> encountered even in a strictly Newtonian universe. We can assume that the
> microwave radiation is changing speed and being Doppler shifted as a result
> of the earth's gravity and the motion of the satellites as Newton would
> probably argue.
Ok, where in Newton's work exactly does he treat doppler shift
of radiation due to gravity? As far as I can tell, Newton's
work does not show *any* effect of gravity on light.
You can do a halfway hybrid of relativity and Newton and get
*a* prediction. This turns out not to match observation.
Socks
Bonnie Granat
> >
> >
> I am still giving relativity a chance to be true, but I expect emotions to
> run high because the proponents of relativity have invested a great deal
of
> themselves in learning all the maths concerned with it, so they are
strongly
> averse to finding out that all that hard work was a complete waste of
time.
>
If SR is not true, it will not be someone who doesn't understand the math
who points it out.
--
Bonnie Granat
Granat Technical Editing and Writing
http://www.editors-writers.info
Paul Cardinale
A: 0.1005
B: 0.1005
C: 1.005
>
> Now let's try another experiment. Both spacecraft synchronize their clocks
> and start toward each other from the markers just like before. Only this
> time, when spacecraft A and B approach each other, spacecraft A makes an
> about face and matches the speed and direction of spacecraft B so that both
> spacecraft are now traveling in the same reference frame. They both continue
> like this until they reach the marker that spacecraft B started from, then
> they both stop. What would all three clocks read now?
A: 0.1005
B: 0.1005
C: 1.005
> It would also be
> useful to know how the clocks on spacecraft A and B would compare
> immediately after spacecraft A made it's about face and entered the
> reference frame of spacecraft B.
>
A: 0.05025
B: 0.05025
>
> We could also try a thought experiment in which an alien solar system has
> always been traveling at close to the speed of light relative to our own. In
> this case, when we and the inhabitants of the other solar system observed
> each other and compared each others clocks, who would be inhabiting the
> privileged frame of reference?
There is no privileged frame of reference.
> Would we conclude that their clock is running
> slower than ours?
Yes.
> Or would they conclude that our clock is running slower
> than theirs?
>
Also Yes.
> When you stop and think about it, Einstein's theory only makes sense if we
> conclude that motion is not relative after all.
>
Wrong. Obviously, you haven't studied relativity. Learn before you spew.
Paul Cardinale
Androcles
>
> "Androcles" <jp006...@blurbblueyonder.co.uk> wrote in message
> news:GrOnb.5032$0E5....@news-binary.blueyonder.co.uk...
> >
> > "Paul R. Mays" <u...@ftc.gov> wrote in message
> > news:nZednQBK4Jm...@giganews.com...
> > > There are no paradox's ... the illusion of paradox exists when
> > > the existing laws governing the construct are incomplete...
> >
> > True. That's the whole point. SR is paradoxical because its existing
laws
> > are 'incomplete'.
> > The 'laws' are 1)
> > "light is always propagated in empty space with a definite velocity c
> which
> > is independent of the state of motion of the emitting body"
> > and 2)
> > "In agreement with experience we the further assume the quantity
> > 2AB/(t'A-tA) = c
> > to be a universal constant- the velocity of light in empty space."
> > I wouldn't call them 'incomplete', though. I call them downright wrong.
> > Androcles
> > See
> > http://www.androc1es.pwp.blueyonder.co.uk/Fundamental.htm
> > for unfairly choosing the biggest half of the apple.
> >
> Don't get to comfy in my statement because I also consider c a variable
> that is variable at the expansion rate of the universe
Light expands in shells from each star. Each shell contains a finite
quantity of energy that is the light. The surface area of this shell is
increasing while the energy it contains remains constant. We should see some
effect. I think the effect we see is redshift. The further the star is from
us, the greater it's shell, the lower the energy density, just merely
distant. Therefore I would expect to find redshift from stars that were not
moving away. This gives us a static universe, infinitely large. No Big Bang,
and no expansion. It has always been thus, and will continue evermore. If
there were a Big Bang, we should at least be able to locate a direction, a
centre it came from. That has not been possible.
But of course you are entitled to your opinion.
[snip, no comment]
Rene DesCartes said "I think, therefore I am."
By stating what should be obvious, he established his existence.
The questions that any journalist worth his salt would ask are the five w's,
Who, What, Where, When and Why?
Who, Where, When are relative terms. A name only identifies the individual
from other individuals. Where cannot be described without a reference, and
the same applies to When. As such, these questions are trivial.
The question one must ask before "Why am I?" is "What am I?"
What am I? should contain the answers to "How " and "Why".
Alas, Rene Descartes is not. Therefore he doesn't think.
Androcles
Jim Greenfield
The LT equations involve ONE dimension only, right? But where are the
observers of the rockets who are doing the "mathemagic"? They are
looking from the SIDE; ie, another dimension. Do you really think that
such blatantly mistaken views can "explain" SR?
For SR observations to be taken seriously, the observer must be in the
line of velocity of all events and objects being discussed, AT ALL
TIMES.....
So there is your eye, with an arrow coming at it. Although the arrow
is 300,000kms long, if it is travelling close to c, according to SR,
head and feathers of arrow must hit eye within interval greatly less
than one second, as the arrow has "shrunk".................
Androcles is correct in asserting that you are hitting your head on a
brick wall to try to convert DHR's---- they can't even see the
ridiculousness of using one dimensional formula in a planer situation.
Jim G
Bonnie Granat
> The questions that any journalist worth his salt would ask are the five
w's,
> Who, What, Where, When and Why?
> Who, Where, When are relative terms. A name only identifies the individual
> from other individuals. Where cannot be described without a reference, and
> the same applies to When. As such, these questions are trivial.
> The question one must ask before "Why am I?" is "What am I?"
> What am I? should contain the answers to "How " and "Why".
> Alas, Rene Descartes is not. Therefore he doesn't think.
> Androcles
The journalist's questions are actually who, what, when, where, and how (not
why).
--
Bonnie Granat, former journalist
Jon Bell
me crosspost to a group that it doesn't carry]
In article <3c4afb26.03102...@posting.google.com>,
Jim Greenfield <greenf...@hotmail.com> wrote:
>
>The LT equations involve ONE dimension only, right?
Wrong. For simplicity, we often restrict ourselves to motion in one
dimension. Nevertheless, it's possible to apply Lorentz transformations
to three-dimensional motion, using 4-dimensional matrix algebra, similar
to the way we handle rotations in classical mechanics using 3-dimensional
matrix algebra.
James Dolan
stephen bint <bi...@iname.com> wrote:
|James,
|
|You speak my language. Can you clarify please, whether there is
|someone on the blue train making a similar complaint about being
|shortchanged for pidgeons.
yeah, there could be someone on the blue train, and yeah, it would
seem to them like their train was the one being shortchanged for
pigeons. exactly symmetrical to the way it seems to the guys on the
red train.
|I suppose there must be. Sorry if I am missing the point, but I am
|trying, honestly.
well, i wouldn't say that there _must_ be, but there could be. unless
you're trying to make sure that the situation is _exactly_
symmetrical, in which case i guess, yeah, you'd better put some guys
on the blue train to make the situation exactly symmetrical.
|Are you saying, like some of the others, that there will be a flood
|of pidgeons at the end, making it all come out alright?
i didn't actually bother to figure out the details of how it would
work out, because i know that it _has_ to work out somehow, but yeah,
now that you mention it, i guess that's pretty much the way it has to
work out. presumably if someone like jon bell wanted to figure out
what happens in this situation he'd figure out some formula for it,
but personally, if i had to figure it out, i'd probably just write a
computer simulation and count the pigeons as they arrive.
|Apart from the fact that the reversal of time dilation during
|acceleration is not a feature of the original theory, it raises even
|more difficult questions. If the amount of time dilation and distance
|contraction required to prevent us seeing each other going faster
|than light is precise as the formula suggests, then its reduction or
|reversal by acceleration will throw a spanner in the works, won't it?
well, if i understand what you're asking here, then the really amazing
thing about this stuff is that although it sounds at first like it
would take some really delicate and tricky planning and coordination
to get everything to dilate and contract by exactly the right amount
at exactly all the right times, in fact it really doesn't require any
planning at all; instead it all just happens automatically due to the
fact that all material objects are made out of little atoms that in
effect do all of their communication and interaction with other atoms
by means of imaginary little carrier pigeons all traveling at the
exact same speed, the speed of light. (the "imaginary little carrier
pigeons" are actually things like light waves and other sorts of
influences that travel at the speed of light.) again, to really
understand what i mean by all of the dilation and contraction
happening "automatically", i think the best thing to do is to write a
computer simulation of how this stuff works, or at least to imagine
writing such a simulation. for some people, though, it's good enough
to just learn how to draw so-called "space-time diagrams" that show
what's going on.
--
[e-mail address jdo...@math.ucr.edu]
Gregory L. Hansen
Not extensions at all, but perhaps applications that the Original Poster
hadn't originally thought of. But heck, Einstein's opinions were never a
postulate of the theory, anyway, so it really doesn't matter what he
thought his theory applied to. Or rather originally thought, his opinions
undoubtedly evolved in the decades between 1915 and his death. All that
matters is whether a conclusion follows from the premises, that's what an
axiomatic system is all about.
Use the Lorentz transforms to boost from one reference frame to another,
dx'/dt' = = (u+v)/(1+uv/c^2)
You've seen that derivation a hundred times. Now do it again,
d^2(x')/d(t')^2 = d^2(x)/dt^2 (1-v^2)^(3/2) / (1-v (dx/dt))^3
from Desloge and Philpott ("Uniformly accelerated reference frames in
special relativity", Am. J. Phys. 55 (3), 252 (1987)).
Same dx' and dt' that was used before! No extension beyond the assumption
that if you can take a derivative once, you can take it again. The
Lorentz transformations are applied twice but they're still the Lorentz
transformations, no additional assumptions are made. An accelerated
frame in special relativity is a boost, followed by a short time interval,
then another boost, then another short wait, and so on. If the first
boost is a part of special relativity, then the second one is, too, and
every boost after that.
Integrate to find a coordinate system and you get some gravity-like
effects including an event horizon, although it's an event horizon that
disappears when you turn the rocket engines off.
--
"Let us learn to dream, gentlemen, then perhaps we shall find the
truth... But let us beware of publishing our dreams before they have been
put to the proof by the waking understanding." -- Friedrich August Kekulé
Gregory L. Hansen
Those are small corrections. Without the general relativistic corrections
you get about a kilometer of error per day, which is clearly unacceptable
since the corrections are only made once per day.
dlzc@aol.com (formerly)
"Dirk Van de moortel" <dirkvand...@ThankS-NO-SperM.hotmail.com> wrote
in message news:0PTnb.113836$_l3.5...@phobos.telenet-ops.be...
>
> "Helmut Wabnig" <hXXXw...@aXXXon.at> wrote in message
news:8710qvkjmhuoitt0o...@4ax.com...
> > On 29 Oct 2003 06:35:41 -0800, pcard...@volcanomail.com (Paul
> > Cardinale) wrote:
> >
> > >
> > >That is not correct. SR can handle acceleration just fine. In fact,
> > >you can use SR to resolve the twin paradox when the travelling twin is
> > >always accelerating/decelerating.
> > >
> > >Paul Cardinale
>
> > I know, there are some efforts, to extend SR.
>
> SR treatment of accelerated motion:
>
http://groups.google.com/groups?&threadm=a3M1b.82977$F92....@afrodite.telenet-ops.be
Can you *do* this with the precept that c is c for all frames, when the
accelerated frame does not measure c to be c? Is is just a small error for
achievable accelerations?
David A. Smith
Paul R. Mays
"Bonnie Granat" <bgr...@editors-writers.info> wrote in message
news:3fa0...@andromeda.5sc.net...
He wasn't talking about journalism....
Bonnie Granat
It makes no difference. He *did* write:
"The questions that any journalist worth his salt would ask are the five
w's,..."
That statement was all I corrected.
--
Bonnie Granat
Richard
Stephen Bint wrote:
>
> "Richard" <no_mail...@yahoo.com> wrote in message
> news:3F9EC1A1...@yahoo.com...
>
> snip
> >
> >
> > Simple, it's not a paradox, it's an outright contradiction.
> Richard, are you defending time dilation or are you dismissing it as a
> fallacy?
> Are you saying the Secial Theory doesn't contradict itself, or that it
> doesn't matter that it does.
>
> > Now you can get on with your life.
> >
> > Richard Perry
>
> I care, that people in charge of billion-dollar particle accelerators,
> believe a theory which cannot possibly be true. So I'll keep my life on hold
> for the moment.
>
> Stephen
It's not a problem when the theory that they believe in is an
approximation of a special case of the correct theory, which former is
only applicable to just such systems as are rigidly mounted to the local
aether frame, i.e. to the Earth.
OTOH note that the photons propelling the particles are infinitely
redshifted wrt those particles, when those particles are moving at c wrt
the source of those photons. (The sources of the photons are the plates
within the accelerator.) Now what infinitely redshifted photon ever
imparted momentum to a particle? The photon of zero hz has zero
momentum. Now how do you suppose such a machine could possibly
accelerate a particle to speeds greater than c? If OTOH the plates were
set into motion wrt Earth, then the particle may be accelerated to
greater than c wrt Earth, which result will also follow by simply
letting the observer take up a motion wrt the plates. SR velocity
addition simply will not apply in either of these cases, in fact it only
accidentally approximates speeds in any other experiment that supposedly
verifies it. Fizeau is a prime example, whose experimental results are
strictly in accord with Galilean relativity rather than SR. Proof upon
request.
Richard Perry
Robert Calvert
expected. But, in order to come to these conclusions, we would have to
assume that spacecraft C carries some magical property known as
*stationary*. But lets pretend that, in the last scenario that you answered,
spacecraft C doesn't exist at all. Let's also pretend that spacecraft B is
really just the earth and that spacecraft A is really a spacecraft returning
from a long trip at close to the speed of light. In this case the answers
"A: 0.05025 and B: 0.05025" could not be correct as judged by your own
rules. And if we assume that all motion is relative, we would also have to
admit that there is not one bit of difference between that last scenario and
a spacecraft returning to earth with the younger twin on board.
Robert
Robert Calvert
"James Dolan" <jdo...@math-cl-n03.math.ucr.edu> wrote in message
news:bnpmfs$jkv$1...@glue.ucr.edu...
<snip>
> ...for some people, though, it's good enough
> to just learn how to draw so-called "space-time diagrams" that show
> what's going on.
I did exactly that. Go to this webpage
http://math.ucr.edu/home/baez/physics/Relativity/SR/TwinParadox/twin_vase.html
and go to figure 3. Study this diagram closely and you'll see that Stella
can only remain younger than her twin as long as she remains in motion and
keeps heading away from her twin. Once she turns around and heads back, this
situation reverses itself. Even though this diagram resolves all variations
of the Twin Paradox, it also means that one twin can never return home
younger than the twin who remained behind. This makes me wonder why
Relativists continue to believe this.
Robert
Stephen Bint
dilation is direction-independent. The formula asserts time dilation in both
directions, so that is what they must defend.
Stephen
Ahmed Ouahi, Architect
......... ...If you limit your choices only to what seems possible or
reasonable, you disconnect yourself from what you truly want, and all that
is left is a compromise!!!!!!!!!!............ ...
--Robert Fritz
--
Ahmed Ouahi, Architect
Best Regards!
"Robert Calvert" <Herc...@pcstarnet.com> kirjoitti viestissä
news:vq18hv7...@corp.supernews.com...
Androcles
> The journalist's questions are actually who, what, when, where, and how
(not
> why).
> --
> Bonnie Granat, former journalist
> Granat Technical Editing and Writing
> http://www.editors-writers.info
Whow!
Androcles
Dirk Van de moortel
"Jim Greenfield" <greenf...@hotmail.com> wrote in message news:3c4afb26.03102...@posting.google.com...
You *are* improving :-)
http://users.pandora.be/vdmoortel/dirk/Physics/Fumbles/OneDim.html
"ONE dimension only, right?"
Dirk Vdm
Androcles
"Gregory L. Hansen" <glha...@steel.ucs.indiana.edu> wrote in message
news:bnpngo$22u$2...@hood.uits.indiana.edu...
Don't just say "Predictions of Relativity", or quote an equation, that's
like me asking what holds the roof up and you saying the walls. What are
walls?
Brick structures held together with cement. What are bricks? Cooked dirt.
Ok, no need to go further on that, it might be interesting how one makes
bricks, but doesn't help in holding up the roof. What's cement? Cooked dirt.
Ok, Now I'm satisfied as to what hold the roof up.
I've looked into it, and it seems to me that whatever makes it work, it
isn't what you say it is, because what you say it is amounts to magic.
You've described the dimensions of the bricks precisely, I can pile the
bricks up, adding height, but I find the roof to be lower than it should be.
The whole is less than the sum of its parts. What happened to the missing
bricks, or missing cement? Well, perhaps the walls are leaning...ok, now I
have a cause I can accept. The roof is lower than it should be because the
walls are leaning.
So, how does it work? How do clocks run faster than they should because they
are at the top of a tower? This is, after all, physics, not mathematics. In
math, I can create structures such as the Klein bottle and describe its
properties. I cannot construct one physically. I live in a world that is
physical in Nature, and Nature doesn't let me make Klein bottles, even if I
can imagine them.
So... how does it work? What is 'leaning' to make the clocks run fast?
Here's my problem.
I create a simple oscillator with a glass tube and some bits and pieces from
the electronic store. It consists of an LED and a photosensitive detector,
such as I use to transmit pictures from my cell phone to my computer and
back again. I put these side-by-side at one end of the tube and a mirror at
the other end. I turn on the LED and off again, and when the light returns
down the tube, trigger it to do it again. Thus I have a simple oscillator,
and I turn it into a clock by counting the pulses. Now I suck out all the
air, shove it into a dometic refrigerator to maintain its temperature, rent
some space in the elevator winding gear room at the top of a tower and let
it run for a couple of months, and figure out it's rate. Then I take down a
mine shaft and repeat. If the velocity of light is constant, and I've made
no changes to the system, what would cause the clock rate to change?
How does it work?
Androcles
alen
> This is a plausible suggestion someone else has made, that an opposite
> effect to time dilation, which I am inclined to call time contraction,
> occurs in objects you observe as decelerating with respect to you. I
think
> if that occurs, it may save the theory from the paradox.
I have to say that I don't like any kind of 'reversal of time dilation'
terminology that might suggest some kind of special time contraction
mechanism to cancel time dilation. In my view, the only
mechanism involved is that a clock travelling at a particular
velocity is seen via its history, and the higher the velocity the
further back in its history it will be seen. Thus, if the velocity is
reduced, the clock will automatically be seen less far back in its
history so that, at zero velocity, it must be seen in its present
reality, as it is always seen by its own observer in its own frame.
Thus, velocity is the only mechanism involved.
I referred to decelerating clocks as appearing to 'speed up', but I
think I might have to abandon that description as too suggestive
of some kind of 'reverse mechanism', or add a caveat to avoid
that.
> But there is a problem with it. We use distance contraction and time
> dilation to explain why the twins do not see eachother going faster than
> light.
>
> It is surely possible to devise a situation in which they are travelling
at
> say, 0.75c in opposite directions so that distance contraction and time
> dilation must be employed to shrink their apparent speed with respect to
> eachother, and then have both ships accelerate or decelerate to cause the
> opposite effect, time contraction, so that time dilation is cancelled and
> the twins will not be prevented from seeing eachother going faster than
> light.
>
> What do you think, is that possible?
>
> Stephen
I have never tried to use this approach to understand the velocity of
light as a limiting velocity, so I don't know whether it could be
explained that way or not. For me, the 'relativistic mass' or
'relativistic
energy' equation seemed sufficient, because it not only limits the
maximum velocity but, if the equation is expanded as a series, the
kinetic energy formula, 1/2mv^2, emerges nicely as the second term
in the expansion.
I understand time dilation and length contraction as a means whereby
a photon can be seen to be travelling at the same velocity at the same
time in two relatively moving reference frames, which would otherwise be
impossible.
Regarding length contraction: this occurs only if you measure
lengths within the moving frame. As I indicated, I don't know whether
or not you could use a 'relativistic velocity', as seen via the moving
frame, to explain the maximum velocity limitation, since I haven't
tried to see if it can be done that way.
Alen