| Topic: |
Science > Physics |
| User: |
"oldton" |
| Date: |
07 Apr 2006 11:01:48 AM |
| Object: |
symmetry in simultaniety of relativity(phew) |
in all the explanations i've read of simultaniety of relativity there
is violation of symmetry between the reference frames. i.e the logic
works when the situation is seen from one reference frame but not the
other. I have read numerous sources (resnick and halliday and several
other books and websites.
HELP
.
|
|
| User: "Martin Hogbin" |
|
| Title: Re: symmetry in simultaniety of relativity(phew) |
07 Apr 2006 01:54:11 PM |
|
|
"oldton" <ussupraj@gmail.com> wrote in message news:1144425708.463979.40510@j33g2000cwa.googlegroups.com...
in all the explanations i've read of simultaniety of relativity there
is violation of symmetry between the reference frames. i.e the logic
works when the situation is seen from one reference frame but not the
other. I have read numerous sources (resnick and halliday and several
other books and websites.
In all descriptions of the relativity of simultaneity that I have
seen the situation has been symmetrical. What situations are
you referring to?
Martin Hogbin
.
|
|
|
|
| User: "Mike Fontenot" |
|
| Title: Re: symmetry in simultaniety of relativity(phew) |
08 Apr 2006 11:57:23 AM |
|
|
Here's a previous posting of mine on how simultaneity
is different for each twin in the classic
"twin paradox" problem. I think it is relevant to
the current question:
_____________________________________________________
Years ago, I derived a simple equation that
relates the current ages of the twins, ACCORDING
TO EACH TWIN. Over the years, I have found it to
be very useful. Originally, I inferred the equation
while staring at a Minkowski diagram. Then later, I
derived it formally from the Lorentz equations.
To save writing, I write "the
current age of a distant object", where the
"distant object" is the stay-at-home twin, as
the "CADO". The CADO has a value for each age t of
the traveling twin, written CADO(t). The traveler
and the stay-at-home twin come to DIFFERENT conclusions
about CADO(t), at any given age t of the traveler.
Denote the traveler's conclusion as CADO_T(t), and
the stay-at-home twin's conclusion as CADO_H(t).
(And in both cases, remember that CADO(t) is the age of
the home twin, and t is the age of the traveler).
My simple equation says that
CADO_T(t) = CADO_H(t) - L*v/(c*c),
where
L is their current distance apart, in lightyears,
according to the home twin,
and
v is their current relative speed, in lightyears/year,
according to the home twin. v is positive
when the twins are moving apart.
(Although the dependence is not shown explicitly
in the above equation, the quantities L and v are
to be considered functions of t, the age of the
traveler).
The factor (c*c) has value 1 for these units, and
is needed only to make the dimensionality correct.
The equation explicitly shows how the home twin's
age will change abruptly (according to the traveler,
not the home twin), whenever the relative
speed changes abruptly.
For example, suppose the home twin believes that she
is 40 when the traveler is 20, immediately before
he turns around. So CADO_H(20-) = 40. (Denote his
age immediately before the turnaround as t = 20-,
and immediately after the turnaround as t = 20+.)
Suppose they are 30 ly apart (according to the home
twin), and that their relative speed is +0.9 ly/y (i.e.,
0.9c), when the traveler's age is 20-. Then the traveler
will conclude that the home twin is
CADO_T(20-) = 40 - 0.9*30 = 13
years old immediately before his turnaround.
Immediately after his turnaround (assumed here
to occur in zero time), their relative speed
is -0.9 ly/y.
The home twin concludes that their distance apart
doesn't change during the turnaround: it's
still 30 ly.
And the home twin concludes that
neither of them ages during the turnaround,
so that CADO_H(20+) is still 40.
But according to the traveler,
CADO_T(20+) = 40 - (-0.9)*30 = 67,
so he concludes that his twin ages 54 years
during his instantaneous turnaround.
In the usual traveling twin scenario, the sudden
change in speed is a negative change: i.e., the
relative speed decreases (becomes more negative, or
less positive), changing from +V to -V (with the
convention that v is positive when the traveler is
moving away from his twin). But note that, if the
sudden speed change is positive, the CADO equation
says that the traveler will then conclude that
his twin suddenly gets YOUNGER, not older.
The CADO equation works for arbitrary accelerations,
not just the idealized instantaneous speed change
assumed above. When the separation is sufficiently
great, even 1-g accelerations can produce rapid
changes (positive and negative) in the current age of
the home twin (according to the traveler). I've got
an example with 1-g accelerations on my web page:
http://home.comcast.net/~mlfasf
The derivation of the equation is given in my paper
"Accelerated Observers in Special Relativity",
PHYSICS ESSAYS, December 1999, p629.
Mike Fontenot
.
|
|
|
|
| User: "=?UTF-8?Q?Jeff=E2=80=A6Relf?=" |
|
| Title: Time is intrinsically local. |
09 Apr 2006 12:11:35 AM |
|
|
Hi Oldton, You wrote:
In all the explanations i've read of simultaniety of relativity there
is violation of symmetry between the reference frames.
i.e the logic works when the situation is seen from one reference frame
but not the other. I have read numerous sources
( resnick and halliday and several other books and websites ). HELP
Time is intrinsically local,
to think otherwise indicates a failure to measure.
If you had accuate enough clocks, -- say with 10 ^ -16 second accuracy --,
you'd notice that the rate your clock ticks
depends on minute changes in your altitude.
Although the speed of light in an ideal vacuum is the same for all
inertial and accelerated observers, the standard second and meter
are both _Observed_ to be elongated in objects moving near the speed of light
or in more accelerated frames... relative to you, the observer.
For example, suppose I met up with you one day and I hopped into my spacecraft,
hovered above you and accelerated myself to the speed of light,
firing my thrusters to maintain a low orbit despite my great velocity.
Sure, it's absurd... not only would the infinite accelerations
require more energy than exists in the cosmos... I'd be instantly vaporized.
Anywho... ignoring such _Minor_ details, ha ha, suppose that fifty years later,
with you still in the same spot, posting to Sci.Physics,
I terminated my orbit and descended to meet you.
I would've experienced almost no proper time compared to your 50 years,
....provided I had infinite energy at my disposal and survived it... ha ha.
.
|
|
|
| User: "Eric Gisse" |
|
| Title: Re: Time is intrinsically local. |
09 Apr 2006 12:45:38 AM |
|
|
Jeff...Relf wrote:
[snip]
As usual, you don't know what you are talking about. Stop posting to
sci.physics.
.
|
|
|
|
|
| User: "hetware" |
|
| Title: Re: symmetry in simultaniety of relativity(phew) |
07 Apr 2006 11:19:19 AM |
|
|
oldton wrote:
in all the explanations i've read of simultaniety of relativity there
is violation of symmetry between the reference frames. i.e the logic
works when the situation is seen from one reference frame but not the
other. I have read numerous sources (resnick and halliday and several
other books and websites.
HELP
Is this 'illogic' related to the appearant acausality suggested by, for
example, the EPR gedanken experiment when considered under the Lorenz
transformations?
--
http://www.vho.org/GB/c/DC/gcgvcole.html
http://www.vho.org/GB/Books/dth/
http://www.germarrudolf.com/
http://www.ice.gov/graphics/news/newsreleases/articles/051115chicago.htm
.
|
|
|
| User: "oldton" |
|
| Title: Re: symmetry in simultaniety of relativity(phew) |
07 Apr 2006 12:23:53 PM |
|
|
what r all d links abt??
and by d way i dont even know what EPR is
.
|
|
|
| User: "hetware" |
|
| Title: Re: symmetry in simultaniety of relativity(phew) |
07 Apr 2006 12:57:36 PM |
|
|
oldton wrote:
what r all d links abt??
It's called a 'signature'. The links will take you to web pages which
provide their own explanation. I suggest you examine the last one first.
and by d way i dont even know what EPR is
http://www.google.com/search?q=EPR+gedanken+experiment
--
http://www.vho.org/GB/c/DC/gcgvcole.html
http://www.vho.org/GB/Books/dth/
http://www.germarrudolf.com/
http://www.ice.gov/graphics/news/newsreleases/articles/051115chicago.htm
.
|
|
|
|
|
|
|
Related Articles |
|
|
