Re: SR time dilation on remote objects ?

From: Marcel Luttgens (mluttgens_at_wanadoo.fr)
Date: 07/22/04 

Date: 22 Jul 2004 05:39:58 -0700

Bjoern Feuerbacher <feuerbac@thphys.uni-heidelberg.de> wrote in message news:<cdjhpc$he9$1@news.urz.uni-heidelberg.de>...
> Marcel Luttgens wrote:
> > Bjoern Feuerbacher <feuerbac@thphys.uni-heidelberg.de> wrote in message news:<cdgrco$39j$1@news.urz.uni-heidelberg.de>...

[snip]
 
> > Assuming an expanding universe, time on an object A moving
> > at v wrt an object B is observed by B to be slowed down by a factor f.
> > In an expanding universe, B moves at -v wrt the observer A, hence
> > B concludes that time on A is slowed down wrt its own time by
> > the same factor f.
>
> *sigh* You make the *same* error *again*, which I already corrected.
> Have you got a short memory, a bad reading comprehension, or is this
> simply willful ignorance?
>
> The time on the object A is *not* observed to *be* slowed down
> by a factor of f compared to the time on the object B. The time on the
> object A is observed to *HAVE BEEN SLOWER WHEN THE LIGHT WAS EMITTED*
> than the time on the object B *WHEN THE LIGHT IS OBSERVED*.
>
> Likewise, the time on the object B is *not* observed to *be* slowed down
> by a factor of f compared to the time on the object A. The time on the
> object A is observed to *HAVE BEEN SLOWER WHEN THE LIGHT WAS EMITTED*
> than the time on the object B *WHEN THE LIGHT IS OBSERVED*.
>
> Or, summarized, as I already told you:
> dt(when the light was emitted) = f*dt(when the light is observed)
>
> ***NOT***
> dt(A) = f*dt(B)
> and
> dt(B) = f*dt(A),
> as you keep arguing - despite my correction!!!
>
 
What an awful mess!

Let's use some formulae.
In an *assumed* expanding universe, an object A moves at v wrt
an object B (approximately, v = Hd, where H is the Hubble
constant, and d is the distance separating A and B at the instant
of observation.

The light source is on A. The ratio of the frequency of the light
measured by B to the frequency of the light source Nu at rest is
Nu(observed by B) / Nu = sqrt(1-v^2/c^2) / (1+v).
As the universe is expanding, v > 0, hence B observes a redshift.
But, according to the observer A, a light source of frequency Nu,
emitted by B, has a frequency corresponding to
Nu(observed by A) / Nu = sqrt(1-v^2/c^2) / (1+v).
Hence Nu(observed by B) = Nu(observed by A), v being expressed
as a speed. But *when v is expressed as a velocity*
(as should be, since when A moves at v wrt B, B moves at -v wrt a),
Nu(observed by A) / Nu = sqrt(1-v^2/c^2) / (1-v), which corresponds
to a blue shift.
Taking into account the Cosmological Principle,
Nu(observed by A) should be equal to Nu(observed by B). Hence,
the velocity v is necessarily zero, meaning that the universe
is not expanding.

You could claim that speeds should be used, not velocities.
Then show it.

>
> Bye,
> Bjoern

Marcel Luttgens

Relevant Pages

  • Re: SR time dilation on remote objects ?
    ... >> at v wrt an object B is observed by B to be slowed down by a factor f. ... In an *assumed* expanding universe, an object A moves at v wrt ... The light source is on A. The ratio of the frequency of the light ... Marcel Luttgens ...
    (sci.astro)
  • Re: SR time dilation on remote objects ?
    ... >> simply because it is symmetrical to any observer in the universe. ... at v wrt an object B is observed by B to be slowed down by a factor f. ... In an expanding universe, B moves at -v wrt the observer A, hence ... Marcel Luttgens ...
    (sci.astro)
  • Re: SR time dilation on remote objects ?
    ... Logic alone never suffices in serious science. ... >at v wrt an object B is observed by B to be slowed down by a factor f. ... >In an expanding universe, B moves at -v wrt the observer A, hence ...
    (sci.astro)
  • Re: SR time dilation on remote objects ?
    ... > a constant velocity wrt every observer, ... What would the velocity of light appear to an observer moving at ... Marcel Luttgens ...
    (sci.astro)