SR time dilation on remote objects ?

Bjoern Feuerbacher wrote in message ...
Marcel Luttgens wrote:
Bjoern Feuerbacher wrote in message ...

Marcel Luttgens wrote:
[snip]




An observer moving away from a light source at a velocity v
(along a straight line of course) can consider himself
at rest wrt the source, and that the light moves at c-v
relatively to him.

No, he can't. That would only make sense if the velocity c of light
were always relative to the source. And we know quite well that that
is not true.



I never claimed the contrary.

Then the velocity of light is c, not c-v, and your argument below breaks
down.

According to SR or GR, yes, according to LET, no.



Let's call Nu the frequency of the emitted light.
If the observer is at rest wrt the light source, he considers
that light moves at c wrt him, and that he receives Nu waves/sec,
where Nu = c/lambda (c is expressed in cm/sec, and the wavelength
lambda is expressed in cm).
If the observer moves away at v wrt the source (or if the source moves
away from him at v, which is the case in an expanding universe),

How often do I need to tell you that the cosmological red shift should
not be interpreted as being due to a Doppler effect? Perhaps this link
will help:
http://www.astronomycafe.net/cosm/expan.html


Assuming a GR universe, you are right.

Do you claim that GR is wrong, or that one should not apply it to the
whole universe?


GR could be wrong.


But my universe is Euclidian.

Huh? In your universe, the signature of the metric is positive?


he considers that light moves at c-v wrt him,

No, he doesn't. See above.


He can.

It would make absolutely no sense for him to consider that. Why on
earth should he do that?

Why not? Are you so sure that c+-v = c, as claimed by SRT/GRT?


And, BTW, it is totally irrelevant what he "considers". What is
important is what he would *measure*. And he would measure c, not c-v.


He would not *measure* the speed of light relative to him, he would
observe a redshift, that he can readily explain be assuming c-v.



and that he receives
Nu(o) waves/sec, where Nu(o) = (c-v)/lambda.
Hence, for him, Nu/Nu(o) = c / (c-v), or lambda(o) = lambda * c/(c-v).
Then 1 + z = lambda(o) / lambda = c/(c-v), and
z = c/(c-v) - 1 = v/(c-v), or
z = (v/c)/(1-v/c), which is my formula for an expanding universe.

It is irrelevant what the observer "considers". The only relevant thing
is what the observer *measures*. And it is simply not true that the
red shift from a source moving at v away from the observer is given
by your formula. The actual red shift for that situation is given
by the formula of special relativity:
z = sqrt((1+v/c)/(1-v/c)) - 1
For small v/c, this gives z = v/c, as it should.

http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/reldop2.html


For small v/c, my formula also gives z = v/c.

BFD.

For larger v, your formula does not give sensible results anymore. If
you think it does, present some data to back this up. (hint: I am *not*
merely talking about cosmological data here - if your formula is right,
it should work for *all* phenomena where Doppler shifts occur)


It gives results as sensible as those of GR, in fact, statistically,
the *same* results.


And I already told you why SR doesn't apply.

No, you merely demonstrated that you don't understand it.

Claiming that time dilation is not symmetrical on objects subject to
"space" expansion (whatever this means) is nonsensical. In this regard
(and others, like the "relativity of simultaneity"), SRT is simply wrong.


With 1/H = 15 Gy, the correlation coefficient between the results
obtained with this formula and those given by Ted Wright's calculator
(with H = 71 km/sec/Mpc (about 13.7 Gy), Omega M = 0.27 and a flat
universe) for the series z = 0.1, 0.5, 1, 2, 3, 5 and 6 is 0.999.

Err, why don't you compare the predictions of your formula to the actual
data? (astro-ph/0402512)



Are you implying that the GR formulae used by Ted Wright in his
calculator are wrong?

I am implying nothing like that. I merely ask you why you use
theoretically calculated numbers instead of the actual data.

Evasion noted.

Are you claiming that the GR formulae he used are right? I then could agree
with you. But why should then my formula (based on LET) be wrong,
as it gives statistically identical results?

OTOH, the actual data you are referring to are SNe data, or we are not
even certain that the SNe are "standard candles". Moreover, the Malmquist
bias has not be taken into consideration in astro-ph/0402512.




IOW, there is no statistically significative difference between
results obtained when assuming an Euclidean stable universe or
a GR expanding universe.
Using Occam's razor, one would consider that the universe is stable,
rather than expanding.

I already told you that red shifts are by far not the only piece of
evidence for an expanding universe.


All those pieces of evidence are far from being unequivocal.

If you can explain all of them with your own model, feel free to do
so. So far, you have ignored most of them simply.



And considering that your formula
above for red shift is nonsense, your situation becomes even worse.



And my formula is right.

Provide evidence for that assertion, please.

And explain how one can derive it, in the light of the fact that
the speed of light for the observer is c, not c-v.

Once more the same GR argument. I am speaking English (LET), you
Chinese (GR). How could we understand each other? This is a dialog
of the deaf. I am not sure that it would be worth to pursue it.
Thank you nevertheless, in spite of some derogatory words you used.



Bye,
Bjoern

Marcel Luttgens

Marcel Luttgens wrote:
Bjoern Feuerbacher wrote in message ...

Marcel Luttgens wrote:

Bjoern Feuerbacher wrote in message ...


Marcel Luttgens wrote:
[snip]





An observer moving away from a light source at a velocity v
(along a straight line of course) can consider himself
at rest wrt the source, and that the light moves at c-v
relatively to him.

No, he can't. That would only make sense if the velocity c of light
were always relative to the source. And we know quite well that that
is not true.



I never claimed the contrary.

Then the velocity of light is c, not c-v, and your argument below breaks
down.


According to SR or GR, yes, according to LET, no.

In the LET, light travels in a medium, right?

And it travels in that medium with the velocity c, right?

"the observer is at rest" means that he is at rest wrt that medium, right?

If you answered "yes" to all of those questions, then the conclusion
is that the velocity of light for the observer is c, not c-v.


[snip]


Assuming a GR universe, you are right.

Do you claim that GR is wrong, or that one should not apply it to the
whole universe?



GR could be wrong.

Could, yes. Your point? Do you want to say that because we can't be sure
that it is right, we should not try to apply it to the universe as a whole?

What do you suggest instead? Newtonian gravity?



But my universe is Euclidian.

Huh? In your universe, the signature of the metric is positive?

Is it?


he considers that light moves at c-v wrt him,

No, he doesn't. See above.


He can.

It would make absolutely no sense for him to consider that. Why on
earth should he do that?


Why not?

Evasion noted.


If light moves in a medium with c, and the observer is at rest in that
medium, the velocity of light wrt him is c.

If light does *not* move in a medium, but SR is right, then the velocity
of light wrt him is also c.


How would he arrive at the assumption that it is c-v?




Are you so sure that c+-v = c, as claimed by SRT/GRT?

SR does *not* claim this.

That's a straw man.


And, BTW, it is totally irrelevant what he "considers". What is
important is what he would *measure*. And he would measure c, not c-v.



He would not *measure* the speed of light relative to him,

He could.


he would
observe a redshift, that he can readily explain be assuming c-v.

The redshift is determined by the *actual* velocity of light, not
by the velocity he "considers".

Assuming c-v would make no sense at all, neither in SR nor in LET.


[snip]


For small v/c, my formula also gives z = v/c.

BFD.

For larger v, your formula does not give sensible results anymore. If
you think it does, present some data to back this up. (hint: I am *not*
merely talking about cosmological data here - if your formula is right,
it should work for *all* phenomena where Doppler shifts occur)



It gives results as sensible as those of GR, in fact, statistically,
the *same* results.

I notice that you ignored my point above that I am *not* talking only
about cosmological data.



And I already told you why SR doesn't apply.

No, you merely demonstrated that you don't understand it.


Claiming that time dilation is not symmetrical on objects subject to
"space" expansion (whatever this means) is nonsensical.

I have explained to you time and time again what is wrong with your
argument. Is this willful ignorance or only simple stupidity?



In this regard
(and others, like the "relativity of simultaneity"), SRT is simply wrong.

For the 50th time: SR has nothing to do with cosmological time dilation.



With 1/H = 15 Gy, the correlation coefficient between the results
obtained with this formula and those given by Ted Wright's calculator
(with H = 71 km/sec/Mpc (about 13.7 Gy), Omega M = 0.27 and a flat
universe) for the series z = 0.1, 0.5, 1, 2, 3, 5 and 6 is 0.999.

Err, why don't you compare the predictions of your formula to the actual
data? (astro-ph/0402512)



Are you implying that the GR formulae used by Ted Wright in his
calculator are wrong?

I am implying nothing like that. I merely ask you why you use
theoretically calculated numbers instead of the actual data.

Evasion noted.


Are you claiming that the GR formulae he used are right?

If you would *finally* tell me about which formulae you talk, I could
go checking that. But so far, you have ignored every question by me
where Ned Wright actually gave these numbers. Do you expect me to search
his whole website?


I then could agree
with you. But why should then my formula (based on LET) be wrong,
as it gives statistically identical results?

OTOH, the actual data you are referring to are SNe data, or we are not
even certain that the SNe are "standard candles".

The data we have obtained so far show that using them as "standard
candles" gives consistent, reliable results.


Moreover, the Malmquist
bias has not be taken into consideration in astro-ph/0402512.

How do you know?



IOW, there is no statistically significative difference between
results obtained when assuming an Euclidean stable universe or
a GR expanding universe.
Using Occam's razor, one would consider that the universe is stable,
rather than expanding.

I already told you that red shifts are by far not the only piece of
evidence for an expanding universe.


All those pieces of evidence are far from being unequivocal.

If you can explain all of them with your own model, feel free to do
so. So far, you have ignored most of them simply.

I notice that you yet again choose to ignore them.



And considering that your formula
above for red shift is nonsense, your situation becomes even worse.



And my formula is right.

Provide evidence for that assertion, please.

And explain how one can derive it, in the light of the fact that
the speed of light for the observer is c, not c-v.


Once more the same GR argument.

No. The argument has nothing to do with GR.


I am speaking English (LET), you Chinese (GR).

No. Even in LET, if the observer is resting wrt the medium, the
velocity of light is c, not c-v.


How could we understand each other? This is a dialog
of the deaf. I am not sure that it would be worth to pursue it.

For starters, you could try to
1) notice that I do not even use the language you assume I am using
2) learn to use your own language correctly.


Thank you nevertheless, in spite of some derogatory words you used.

I would use less derogatory words if you would not constantly ignore
quite a lot of arguments by me, and an even larger heap of evidence.


Bye,
Bjoern

Bjoern Feuerbacher wrote in message ...
Marcel Luttgens wrote:
Bjoern Feuerbacher wrote in message ...

Marcel Luttgens wrote:

Bjoern Feuerbacher wrote in message ...


Marcel Luttgens wrote:
[snip]





An observer moving away from a light source at a velocity v
(along a straight line of course) can consider himself
at rest wrt the source, and that the light moves at c-v
relatively to him.

No, he can't. That would only make sense if the velocity c of light
were always relative to the source. And we know quite well that that
is not true.



I never claimed the contrary.

Then the velocity of light is c, not c-v, and your argument below breaks
down.


According to SR or GR, yes, according to LET, no.

In the LET, light travels in a medium, right?

And it travels in that medium with the velocity c, right?

"the observer is at rest" means that he is at rest wrt that medium, right?

If you answered "yes" to all of those questions, then the conclusion
is that the velocity of light for the observer is c, not c-v.


You are simply too "dense" (do you like such derogatory qualifier?)
to realize that the situation where the observer moves away at v wrt
the source is equivalent to the situation where the source moves
away from the observer at v, which is the case in an expanding
universe.

Situation 1: The observer O moves away at v from the source S.

After a time interval t, the distance d separating O from S
becomes d' = d+vt = ct.
Hence, d = (c-v)t, or d = c't, where c' = c-v.
Notice that c' is *not* the true speed of light, it is a
"mathematical" speed, which can be used when assuming the
constancy of d.

I repeat the demonstration leading to z, because you likely
have already forgotten it (you should appreciate my
polite wording):

Let's call Nu the frequency of the emitted light.
If the observer is at rest wrt the light source, he considers
that light moves at c wrt him, and that he receives Nu waves/sec,
where Nu = c/lambda (c is expressed in cm/sec, and the wavelength
lambda is expressed in cm).
If the observer moves away at v wrt the source (or if the source moves
away from him at v, which is the case in an expanding universe),
he considers that light moves at c-v wrt him, and that he receives
Nu(o) waves/sec, where Nu(o) = (c-v)/lambda.
Hence, for him, Nu/Nu(o) = c / (c-v), or lambda(o) = lambda * c/(c-v).
Then 1 + z = lambda(o) / lambda = c/(c-v), and
z = c/(c-v) - 1 = v/(c-v), or
z = (v/c)/(1-v/c), which is my formula for an expanding universe.

Situation 2: The source S moves away at v from the observer O.

After a time interval t, the distance d separating S from O
becomes d' = d+vt = ct.
Hence, d = (c-v)t, or d = c't, where c' = c-v.
Notice that c' is *not* the true speed of light, it is a
"mathematical" speed, which can be used when assuming the
constancy of d.

Do I have to repeat the derivation of z once more?
Perhaps, as so many GRists seem unable to understand elementary
physical reasoning (another nice as hominem).

Marcel Luttgens


Bye,
Bjoern

Marcel Luttgens wrote:
Bjoern Feuerbacher wrote in message ...

Marcel Luttgens wrote:

Bjoern Feuerbacher wrote in message ...




[snip]

Then the velocity of light is c, not c-v, and your argument below breaks
down.


According to SR or GR, yes, according to LET, no.

In the LET, light travels in a medium, right?

Right or not?


And it travels in that medium with the velocity c, right?

Right or not?


"the observer is at rest" means that he is at rest wrt that medium, right?

Right or not?


If you answered "yes" to all of those questions, then the conclusion
is that the velocity of light for the observer is c, not c-v.

I notice that you simply chose to ignore this argument.

You can't refute it, right?


You are simply too "dense" (do you like such derogatory qualifier?)
to realize that the situation where the observer moves away at v wrt
the source is equivalent to the situation where the source moves
away from the observer at v, which is the case in an expanding
universe.

Err, in the case of an expanding universe, still both situations are
equivalent (provided one uses SR or GR, but I think that would
also apply in LET).


Situation 1: The observer O moves away at v from the source S.

After a time interval t, the distance d separating O from S
becomes d' = d+vt = ct.

So, "d'" is the distance after a time t. But what is "d" in your
formula here? The distance between O and S at time 0, or what?

Do you mean d(t) = d + vt?


Hence, d = (c-v)t, or d = c't, where c' = c-v.

And what on earth has this c' to do with the actual measured or
considered velocity of light?


Notice that c' is *not* the true speed of light, it is a
"mathematical" speed, which can be used when assuming the
constancy of d.

Huh??? If either O or S moves, d does not remain constant. Why
on earth should one assume that it remains constant???


I repeat the demonstration leading to z, because you likely
have already forgotten it (you should appreciate my
polite wording):

Let's call Nu the frequency of the emitted light.
If the observer is at rest wrt the light source, he considers
that light moves at c wrt him, and that he receives Nu waves/sec,
where Nu = c/lambda (c is expressed in cm/sec, and the wavelength
lambda is expressed in cm).
If the observer moves away at v wrt the source (or if the source moves
away from him at v, which is the case in an expanding universe),
he considers that light moves at c-v wrt him,

That is *still* nonsense. WHY ON EARTH should he consider that? What
you wrote above shows nothing like that!


and that he receives
Nu(o) waves/sec, where Nu(o) = (c-v)/lambda.
Hence, for him, Nu/Nu(o) = c / (c-v), or lambda(o) = lambda * c/(c-v).
Then 1 + z = lambda(o) / lambda = c/(c-v), and
z = c/(c-v) - 1 = v/(c-v), or
z = (v/c)/(1-v/c), which is my formula for an expanding universe.

Situation 2: The source S moves away at v from the observer O.

After a time interval t, the distance d separating S from O
becomes d' = d+vt = ct.
Hence, d = (c-v)t, or d = c't, where c' = c-v.
Notice that c' is *not* the true speed of light, it is a
"mathematical" speed, which can be used when assuming the
constancy of d.

Exactly the same nonsense as above. Answer my questions!


Do I have to repeat the derivation of z once more?

No. You merely have to explain in more detail WHY ON EARTH
the observer would "consider" that the speed of light is c-v,
and WHY ON EARTH the red shift is determined by what the observer
"considers" to be the speed of light, instead of what it actually *is*.


Perhaps, as so many GRists seem unable to understand elementary
physical reasoning (another nice as hominem).

Perhaps one shouldn't use ad hominems if one doesn't even manage
to write "ad hominem" correctly.


Bye,
Bjoern

Bjoern Feuerbacher wrote in message ...
Marcel Luttgens wrote:
Bjoern Feuerbacher wrote in message ...

Marcel Luttgens wrote:

Bjoern Feuerbacher wrote in message ...




[snip]

Then the velocity of light is c, not c-v, and your argument below breaks
down.


According to SR or GR, yes, according to LET, no.

In the LET, light travels in a medium, right?

Right or not?


And it travels in that medium with the velocity c, right?

Right or not?


"the observer is at rest" means that he is at rest wrt that medium, right?

Right or not?


If you answered "yes" to all of those questions, then the conclusion
is that the velocity of light for the observer is c, not c-v.

I notice that you simply chose to ignore this argument.

You can't refute it, right?


In LET, light moves at c through a medium (the so-called ether).
Btw, in my derivation, the observer is considered as moving away from
the source (situation 1), or the source is moving away from the observer
(situation 2).


You are simply too "dense" (do you like such derogatory qualifier?)
to realize that the situation where the observer moves away at v wrt
the source is equivalent to the situation where the source moves
away from the observer at v, which is the case in an expanding
universe.

Err, in the case of an expanding universe, still both situations are
equivalent (provided one uses SR or GR, but I think that would
also apply in LET).


Then why did you claim this far that situation 2 was different from
situation 1?


Situation 1: The observer O moves away at v from the source S.

After a time interval t, the distance d separating O from S
becomes d' = d+vt = ct.

So, "d'" is the distance after a time t. But what is "d" in your
formula here? The distance between O and S at time 0, or what?


Yes.

Do you mean d(t) = d + vt?

After a time interval t, light has travelled a distance ct, whereas
the observer has travelled vt. As the distance separating the source
from the observer was d at time 0, the observer is now at a distance
d' = d+vt from the source. So, one has ct = d+vt, and d = (c-v)t.
This is mathematically equivalent to d = c't, where c' = c-v.
Can't you really understand this, or are you simply quibbling?



Hence, d = (c-v)t, or d = c't, where c' = c-v.

And what on earth has this c' to do with the actual measured or
considered velocity of light?

The observer can consider that his distance from the source is still d,
hence that light has travelled to him at a velocity c' = c-v.



Notice that c' is *not* the true speed of light, it is a
"mathematical" speed, which can be used when assuming the
constancy of d.

Huh??? If either O or S moves, d does not remain constant. Why
on earth should one assume that it remains constant???


Of course, the distance observer-source is not constant, but the
observer can "mathematically" consider that it is constant, and that
light moves at c-v.


I repeat the demonstration leading to z, because you likely
have already forgotten it (you should appreciate my
polite wording):

Let's call Nu the frequency of the emitted light.
If the observer is at rest wrt the light source, he considers
that light moves at c wrt him, and that he receives Nu waves/sec,
where Nu = c/lambda (c is expressed in cm/sec, and the wavelength
lambda is expressed in cm).
If the observer moves away at v wrt the source (or if the source moves
away from him at v, which is the case in an expanding universe),
he considers that light moves at c-v wrt him,

That is *still* nonsense. WHY ON EARTH should he consider that? What
you wrote above shows nothing like that!


WHY not? Mathematically, the observer is right.


and that he receives
Nu(o) waves/sec, where Nu(o) = (c-v)/lambda.
Hence, for him, Nu/Nu(o) = c / (c-v), or lambda(o) = lambda * c/(c-v).
Then 1 + z = lambda(o) / lambda = c/(c-v), and
z = c/(c-v) - 1 = v/(c-v), or
z = (v/c)/(1-v/c), which is my formula for an expanding universe.

Situation 2: The source S moves away at v from the observer O.

After a time interval t, the distance d separating S from O
becomes d' = d+vt = ct.
Hence, d = (c-v)t, or d = c't, where c' = c-v.
Notice that c' is *not* the true speed of light, it is a
"mathematical" speed, which can be used when assuming the
constancy of d.

Exactly the same nonsense as above. Answer my questions!


See above.


Do I have to repeat the derivation of z once more?

No. You merely have to explain in more detail WHY ON EARTH
the observer would "consider" that the speed of light is c-v,
and WHY ON EARTH the red shift is determined by what the observer
"considers" to be the speed of light, instead of what it actually *is*.


Because, as the observer considers that his distance from the source
(or the source considers that its distance from the observer)
remains d, he/it can assume that light moves at c-v. This is
logically and mathematically right.


Perhaps, as so many GRists seem unable to understand elementary
physical reasoning (another nice as hominem).

Perhaps one shouldn't use ad hominems if one doesn't even manage
to write "ad hominem" correctly.


You just demonstrated that my demonstration is false.


Bye,
Bjoern

Marcel Luttgens

Marcel Luttgens wrote:
Bjoern Feuerbacher wrote in message ...

Marcel Luttgens wrote:

Bjoern Feuerbacher wrote in message ...


Marcel Luttgens wrote:


Bjoern Feuerbacher wrote in message ...




[snip]


Then the velocity of light is c, not c-v, and your argument below breaks
down.


According to SR or GR, yes, according to LET, no.

In the LET, light travels in a medium, right?

Right or not?

And it travels in that medium with the velocity c, right?

Right or not?

"the observer is at rest" means that he is at rest wrt that medium, right?

Right or not?

If you answered "yes" to all of those questions, then the conclusion
is that the velocity of light for the observer is c, not c-v.

I notice that you simply chose to ignore this argument.

You can't refute it, right?



In LET, light moves at c through a medium (the so-called ether).

So, if the observer is at rest (in the medium), light moves with
the velocity c wrt him.


Btw, in my derivation, the observer is considered as moving away from
the source (situation 1), or the source is moving away from the observer
(situation 2).

*sigh* Why did you feel the need to repeat this?



You are simply too "dense" (do you like such derogatory qualifier?)
to realize that the situation where the observer moves away at v wrt
the source is equivalent to the situation where the source moves
away from the observer at v, which is the case in an expanding
universe.

Err, in the case of an expanding universe, still both situations are
equivalent (provided one uses SR or GR, but I think that would
also apply in LET).



Then why did you claim this far that situation 2 was different from
situation 1?

The situations are *not* equivalent if one uses *Galileian* relativity.

In LET, the situations *are* equivalent - but the proof for that
would, AFAIK, run quite different from what you presented here.


Situation 1: The observer O moves away at v from the source S.

After a time interval t, the distance d separating O from S
becomes d' = d+vt = ct.

So, "d'" is the distance after a time t. But what is "d" in your
formula here? The distance between O and S at time 0, or what?



Yes.


Do you mean d(t) = d + vt?


After a time interval t, light has travelled a distance ct, whereas
the observer has travelled vt.

Agreed. So you indeed meant d(t) = d + vt. A simple "yes" would have
been enough here.


As the distance separating the source
from the observer was d at time 0, the observer is now at a distance
d' = d+vt from the source. So, one has ct = d+vt, and d = (c-v)t.

Agreed.


This is mathematically equivalent to d = c't, where c' = c-v.

Still agreed.

But what has this c' now to do with the velocity of light, as observed
by the observer? Nothing at all!

"velocity" is "distance travelled" divided by "time the travel took".
Since in the time t, the light did *not* travel the distance d, you
can't say that c' = d/t is the velocity of the light!



Can't you really understand this, or are you simply quibbling?

Are you really unable to understand that the c' you introduced here
has nothing at all to do with the velocity of light, as measured
or "considered" by the observer?


Hence, d = (c-v)t, or d = c't, where c' = c-v.

And what on earth has this c' to do with the actual measured or
considered velocity of light?


The observer can consider that his distance from the source is still d,

WHY ON EARTH WOULD HE CONSIDER THAT??? HE SAW HIMSELF THAT THE DISTANCE
INCREASED!!!!!


hence that light has travelled to him at a velocity c' = c-v.

So, if the observer considers that a source which clearly moved away
from him was at rest, he would think that the velocity of light is
c' = c-v. What on earth has this completely mad idea of the observer
to do with the actually *measured* red shift? Red shift is determined
by what actually *happens*, not by what the observer *thinks* that
happens!!!


Notice that c' is *not* the true speed of light, it is a
"mathematical" speed, which can be used when assuming the
constancy of d.

Huh??? If either O or S moves, d does not remain constant. Why
on earth should one assume that it remains constant???



Of course, the distance observer-source is not constant, but the
observer can "mathematically" consider that it is constant,

What on earth is "mathematically consider" supposed to mean, and why
on earth should the observer do something as mad as considering
that d did not increase, although it clearly did increase?


and that light moves at c-v.

Again: red shift is determined by what actually *happens*, not by
what the observer "considers" to happen!


I repeat the demonstration leading to z, because you likely
have already forgotten it (you should appreciate my
polite wording):

Let's call Nu the frequency of the emitted light.
If the observer is at rest wrt the light source, he considers
that light moves at c wrt him, and that he receives Nu waves/sec,
where Nu = c/lambda (c is expressed in cm/sec, and the wavelength
lambda is expressed in cm).
If the observer moves away at v wrt the source (or if the source moves
away from him at v, which is the case in an expanding universe),
he considers that light moves at c-v wrt him,

That is *still* nonsense. WHY ON EARTH should he consider that? What
you wrote above shows nothing like that!



WHY not?

Because that has nothing to do with what actually happens!



Mathematically, the observer is right.

Prove this assertion, please. How on earth is the observer
"mathematically right" to claim that d does not increase, when in
reality it does increase?



[snip]


Do I have to repeat the derivation of z once more?

No. You merely have to explain in more detail WHY ON EARTH
the observer would "consider" that the speed of light is c-v,
and WHY ON EARTH the red shift is determined by what the observer
"considers" to be the speed of light, instead of what it actually *is*.



Because, as the observer considers that his distance from the source
(or the source considers that its distance from the observer)
remains d, he/it can assume that light moves at c-v. This is
logically and mathematically right.

This is nonsense. Red shift is determined by what actually *happens*,
not by what the observer "considers" to happen!


[snip]

Bye,
Bjoern

Bjoern Feuerbacher wrote in message ...
Marcel Luttgens wrote:
Bjoern Feuerbacher wrote in message ...


snip

Because, as the observer considers that his distance from the source
(or the source considers that its distance from the observer)
remains d, he/it can assume that light moves at c-v. This is
logically and mathematically right.

This is nonsense. Red shift is determined by what actually *happens*,
not by what the observer "considers" to happen!


Here is a less "synthetic" derivation:

Imagine that a crest has just reached an observer.
The wavelength of the emitted light is lambda, and its frequency Nu
corresponds of course to c/lambda.
If the observer is at rest wrt the source, he will get the next crest
after 1/Nu = lambda/c seconds.
The question is now, after what time will an observer moving away
at v from the source will get the next crest?
The answer is straightforward, after lambda/(c-v) seconds.
IOW, the number of crests got by the moving observer is (c-v)/lambda
crests/sec, which can be written Nu(o) = (c-v)/lambda.
Then we have Nu(o)/Nu = (c-v)/c, and lambda(o)/lambda = c/(c-v), or
1 + z = c/(c-v), thus
z = v/(c-v) = (v/c)/(1-v/c).
This formula is valid, whether the observer is moving away from
the light source, or the light source is moving away from the
observer.
Let's note that in an expanding universe, the observer and the
source are *simultaneously* moving away from each other, hence time
on the observer's clock and the source's clock are both dilated
by the same amount, and neither the observer nor the source can
observe a relativistic time dilation.
As in an expanding universe, v = Hd, the relation between z and d
is given by z = Hd/(c-Hd) = d/((c/H)-d), where d is the distance
separating the observer from the source.
One also gets d = (c/H) * z/(1+z),
which is the same formula as that obtained when hypothetizing
a stable Euclidean universe with mean density rho, and a negative
cosmological deceleration cH reddening light emitted from any
point of the universe.
The time t taken by light to travel a distance d is given by
t = (1/H) * z/(1+z)

If you don't understand this derivation, you really have big
"reading" problems.
Then, instead of light, you could imagine a line of cars moving
at V = 20 m/s on a highway lane, and separated by 10 m from each
other. On a parallel lane, a Volkswagen is moving at 5 m/s in the
same direction.
Try to find the number of cars that will pass the Volkswagen
per second, and compare it with the number of cars that would pass the
Volkswagen if it was parked along the lane.


[snip]

Bye,
Bjoern

Marcel Luttgens

Marcel Luttgens wrote:
Bjoern Feuerbacher wrote in message ...

Marcel Luttgens wrote:

Bjoern Feuerbacher wrote in message ...



snip

In that "snip", there was my argument which showed that the speed
of light is c for the observer, not c-v. Interesting that you choose
to ignore it.


Because, as the observer considers that his distance from the source
(or the source considers that its distance from the observer)
remains d, he/it can assume that light moves at c-v. This is
logically and mathematically right.

This is nonsense. Red shift is determined by what actually *happens*,
not by what the observer "considers" to happen!



Here is a less "synthetic" derivation:

Imagine that a crest has just reached an observer.
The wavelength of the emitted light is lambda, and its frequency Nu
corresponds of course to c/lambda.
If the observer is at rest wrt the source, he will get the next crest
after 1/Nu = lambda/c seconds.

Agreed.


The question is now, after what time will an observer moving away
at v from the source will get the next crest?

Stop right here. In your original scenario, the observer was resting,
and the source was moving.

And no, as long as one uses Galilean relativity (as you keep doing)
and a medium for light, those two situations are *not* equivalent.


The answer is straightforward, after lambda/(c-v) seconds.

Only right if Galilean relativity applies and if light moves with
c in a medium.


IOW, the number of crests got by the moving observer is (c-v)/lambda
crests/sec, which can be written Nu(o) = (c-v)/lambda.
Then we have Nu(o)/Nu = (c-v)/c, and lambda(o)/lambda = c/(c-v), or
1 + z = c/(c-v), thus
z = v/(c-v) = (v/c)/(1-v/c).

BFD. That's the standard Doppler result for sound. If one makes
the same assumption for light propagation as for sound propagation,
it's no wonder that the result is the same.


This formula is valid, whether the observer is moving away from
the light source, or the light source is moving away from the
observer.

Wrong. If you think so, *prove* that these situations are equivalent,
given the assumptions used above (Galileian relativity and light moving
with c in a medium). Hint: they aren't.


Let's note that in an expanding universe, the observer and the
source are *simultaneously* moving away from each other,

More correct: the space between them is expanding.


hence time
on the observer's clock and the source's clock are both dilated
by the same amount, and neither the observer nor the source can
observe a relativistic time dilation.

*sigh* For the 100th time: cosmological time dilation has nothing
to do with the time dilation of SR.

How often do I need to tell you that? How many links to pages written by
professional cosmologists do I have to give to you which say that?

[snip]


If you don't understand this derivation, you really have big
"reading" problems.

The derivation you gave above is perfectly valid for Galileian
relativity, light moving with c in a medium, the source resting and
the observer moving.

However, that situation has nothing at all to do with the actual
cosmological red shift.


[snip]

Bye,
Bjoern

Bjoern Feuerbacher wrote in message ...
Marcel Luttgens wrote:
Bjoern Feuerbacher wrote in message ...

Marcel Luttgens wrote:

Bjoern Feuerbacher wrote in message ...



snip

In that "snip", there was my argument which showed that the speed
of light is c for the observer, not c-v. Interesting that you choose
to ignore it.


Your argument is irrelevant. The observer can claim that light moves
at c-v wrt him. But the point is that my formula is right, what you denied
till now.


Because, as the observer considers that his distance from the source
(or the source considers that its distance from the observer)
remains d, he/it can assume that light moves at c-v. This is
logically and mathematically right.

This is nonsense. Red shift is determined by what actually *happens*,
not by what the observer "considers" to happen!



Here is a less "synthetic" derivation:

Imagine that a crest has just reached an observer.
The wavelength of the emitted light is lambda, and its frequency Nu
corresponds of course to c/lambda.
If the observer is at rest wrt the source, he will get the next crest
after 1/Nu = lambda/c seconds.

Agreed.


The question is now, after what time will an observer moving away
at v from the source will get the next crest?

Stop right here. In your original scenario, the observer was resting,
and the source was moving.

And no, as long as one uses Galilean relativity (as you keep doing)
and a medium for light, those two situations are *not* equivalent.


Both situations are strictly equivalent.


The answer is straightforward, after lambda/(c-v) seconds.

Only right if Galilean relativity applies and if light moves with
c in a medium.


Why not? And (c-v) proves that the observer could claim that, mathematically,
light moves at such velocity. Of course, he knows perfectly well that
light moves "physically" at c.


IOW, the number of crests got by the moving observer is (c-v)/lambda
crests/sec, which can be written Nu(o) = (c-v)/lambda.
Then we have Nu(o)/Nu = (c-v)/c, and lambda(o)/lambda = c/(c-v), or
1 + z = c/(c-v), thus
z = v/(c-v) = (v/c)/(1-v/c).

BFD. That's the standard Doppler result for sound. If one makes
the same assumption for light propagation as for sound propagation,
it's no wonder that the result is the same.


Why didn't you said this before? And why would not the same formula
apply to light? In fact, it is the formula used to interpret the
data obtained by the radar systems used by the police to determine
the speed of cars, whether the system is at rest along the road, or moving
(see http://copradar.com/preview/chapt2/ch2d1.html#example ).
The formula z = (v/c) / (1-(v/c) can as well be used for light emitters/
receivers subject to space expansion.


This formula is valid, whether the observer is moving away from
the light source, or the light source is moving away from the
observer.

Wrong. If you think so, *prove* that these situations are equivalent,
given the assumptions used above (Galileian relativity and light moving
with c in a medium). Hint: they aren't.


See the above reference.


Let's note that in an expanding universe, the observer and the
source are *simultaneously* moving away from each other,

More correct: the space between them is expanding.


This is the GR interpretation. But space carries galaxies, etc...,
along. How? GRT has no explanation at all.


hence time
on the observer's clock and the source's clock are both dilated
by the same amount, and neither the observer nor the source can
observe a relativistic time dilation.

*sigh* For the 100th time: cosmological time dilation has nothing
to do with the time dilation of SR.


I didn't speak of SR.

How often do I need to tell you that? How many links to pages written by
professional cosmologists do I have to give to you which say that?


By "cosmological time dilation", you mean GRT time dilation.
GRT is the theory used today, this doesn't mean that it is right.

[snip]


If you don't understand this derivation, you really have big
"reading" problems.

The derivation you gave above is perfectly valid for Galileian
relativity, light moving with c in a medium, the source resting and
the observer moving.


No, the source can be moving, and the observer can be at rest, or
both can be moving wrt each other, which is the case in an expanding
universe. See http://copradar.com/preview/chapt2/ch2d1.html#example.

However, that situation has nothing at all to do with the actual
cosmological red shift.


How do you know that the GRT formulae for the cosmological red shift
gives results that correspond to reality?
From the above, I retain that you now accept my formula when the
observer is moving, the source being considered at rest.
Read carefully the reference I gave you, and you will conclude that
the formula is also valid when the source is moving.
Acknowledge that your previous arguments against it were wrong.
Of course, you still could claim that even it it applies on Earth,
it cannot be used for the cosmological redshift. But this would be
the claim of a GRT partisan, nothing more.


[snip]

Bye,
Bjoern

Marcel Luttgens

"Marcel Luttgens" wrote in message
om...
Bjoern Feuerbacher wrote in message
...
And no, as long as one uses Galilean relativity (as you keep doing)
and a medium for light, those two situations are *not* equivalent.

Both situations are strictly equivalent.

Bjoern is right, they are not equivalent. The difference
is the speed of the medium relative to the observer. Look
up the standard formulae for Doppler shift of sound in any
text book.

BFD. That's the standard Doppler result for sound. If one makes
the same assumption for light propagation as for sound propagation,
it's no wonder that the result is the same.

Why didn't you said this before? And why would not the same formula
apply to light?

In LET both the moving source and moving observer formulae
would apply (they are not the same - see above) but you
then need to also take clock slowing into account. For a
moving observer and a source at rest in the medium, clock
slowing applies to the observer but not the source so they
do not cancel. For a moving source and an observer at rest
in the medium, clock slowing applies to the source but not
the observer and again they do not cancel. [1]

I now return you to your regularly scheduled flames.

George

[1] Hint: note that clock slowing of the source will reduce
the frequency measured by the observer but slowing of _his_
clocks makes the frequency _seem_ higher in comparison.